![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
Previous Article | Next Article 
Journal of Clinical Microbiology, June 2000, p. 2030-2036, Vol. 38, No. 6
Quantitative Molecular Analysis of Virus Expression
and Replication
Department of Biomedical Sciences, University
of Trieste, Trieste, Italy
Analysis of virus expression in
vitro and in vivo using the highly sensitive quantitative methods
developed during the last 10 years is at present an absolute
requirement for addressing the pathogenic mechanisms of viral
infections and the virus-host interactions at the molecular level. In
medical virology, the availability of methods and strategies able to
address in vivo the relationship between virus expression and disease
outcome is playing a crucial role in pathogenic research. These studies have documented that virus load in blood or in tissues is an important correlate of disease outcome, as documented in infections with human
immunodeficiency virus type 1 (HIV-1) (3, 5, 17, 35, 63,
70), hepatitis B virus (HBV) (10, 31), hepatitis C
virus (HCV) (25, 34, 54-56), human cytomegalovirus (HCMV) (87), Epstein-Barr virus (50, 88), human
papillomaviruses (HPVs) (89), and human T-lymphotropic virus
type 1 (42). Moreover, while the rationale for the
development of new antiviral compounds is a direct consequence of a
precise understanding of virus life cycle, identification of the
virologic correlates of disease progression in vivo using quantitative
methods has had a major role in the planning of effective treatments in
viral infections of humans. Basic science approaches have also
extensively employed quantitative molecular procedures. In virology,
these approaches have shown that a number of events in the life cycle
of many viruses (as well as those driving virus-host interactions) are
more complex than originally defined. For instance, the
characterization of the viral transcriptional profile and its dynamics
using quantitative methods has uncovered, in some cases, complex
processes or novel dynamic features. Importantly, together with new
data, the application of quantitative methods to basic virologic
research has generated new working hypotheses. Overall, the potential
of virologic investigations has increased dramatically following the
development of reliable quantitative techniques for viral nucleic
acids, and from this point of view, quantitative molecular technology
represents an important hallmark of the virology of the 1990s.
It has recently been observed that the new technologies (including
those allowing absolute quantitation of viral nucleic acids) are
driving the research agenda (9). However, despite the
intense effort of the research community, several questions concerning the technical development and the methodology of specific applications and the role of quantitative parameters in basic and medical virology remain unanswered. Firstly, it is important to verify whether or not an
ideal molecular method for the quantitative analysis of viral nucleic
acids is currently available. Secondly, although a preliminary
diagnosis in clinical virology does not require quantitation, it should
be clarified whether direct quantitative molecular methods are likely
to provide, in the near future, a real alternative to classic culture
techniques or immunological assays in the laboratory evaluation of most
(all) viral infections. Thirdly, the real prognostic-diagnostic role of
the different quantitative molecular parameters analyzed in vivo
(cell-free viral genome molecules in plasma or in different
compartments, analysis of different classes of viral transcripts in
infected cells, and provirus copy numbers in infected cells in
retroviral infections) should be evaluated in most viral infections.
Fourthly, it should be clarified whether quantitative methods are
invariably necessary and/or sufficient for monitoring specific
antiviral treatments. These general questions and other aspects
concerning the biology of specific viral agents and the relevant
features of the virus-host interplay highlight the central role of the current research in this field. Due to the general implications of
quantitative methods, the correct answers to these outstanding questions are expected to contribute significantly to the
identification of future objectives for molecular research in virology
and to the development of effective diagnostic strategies for viral infections.
Although the present report aims at addressing the present and
future impact of quantitative molecular methods in virology and not at
providing technical guidelines, a brief critical comment on available
procedures is necessary for a clear understanding of the current
research trends. Different quantitative techniques and methodologies
for nucleic acid species have been developed in the last 10 years; most
of them have first been optimized in virologic applications and later
applied to other biological and biomedical fields. Thus, virologic
applications may be regarded as an "icebreaker" for quantitative
methods aimed at determining the copy numbers of nucleic acids present
at low concentrations in biological samples.
Ideally, a quantitative assay for viral nucleic acids should be endowed
with (i) high sensitivity (in several conditions, the detection of very
low levels of viral nucleic acids is required), (ii) flexibility (viral
nucleic acids of different natures and present at highly different
concentrations in biological samples should be quantified with
identical efficiency), and (iii) reproducibility (comparative
evaluation is necessary in most cases). The assay should also (iv)
allow absolute (not relative) quantitation of nucleic acid copy numbers
and (v) be suitable for widespread routine application (fast and safe
and requiring limited handling). Unfortunately, available methods do
not meet all these requirements.
Conventional PCR amplification (80, 81) currently provides
high sensitivity and specificity for the purpose of detecting specific
nucleic acid sequences present in low amounts in biological samples.
Furthermore, PCR has demonstrated very high flexibility; other
enzymatic amplification techniques, such as ligase chain reaction
(8) and isothermal amplification methods (68),
have not yet proved to be equally versatile. However, PCR is not per se
a quantitative technique, and a commonly experienced feature of PCR
amplifications is the low reproducibility level of the amount of
product yield, even under the most stringent assay conditions. Among
the methods proposed to overcome this problem, only competitive PCR
(cPCR) (33) has proved to be sufficiently reliable for the absolute quantitation of DNA and RNA species (18, 20). A
large number of virologic applications of cPCR have clearly shown its flexibility and reliability (3, 5, 19, 30, 44, 51, 62, 75-77, 84,
88, 92). Although theoretical considerations and practical data
indicate that cPCR may be regarded as the reference method for the
quantitative analysis of nucleic acid species (21), the
relatively high technical complexity of cPCR applications and the need
for experienced operators unfortunately represent important obstacles
to the widespread routine use of this procedure.
An alternative method for the direct quantitative analysis of nucleic
acids based on signal amplification after hybridization is designated
branched DNA (66). Although in its early versions this
technique displayed lower sensitivity than PCR-based procedures, the
changes made in the method in the last few years have increased the
signal-to-noise ratio, significantly improving sensitivity. This method
exhibits several positive characteristics that could allow its
widespread application as a diagnostic tool. These characteristics include simpler and faster sample preparation for branched DNA than for
other molecular methods and better tolerance of target sequence
variation (71); the latter feature may be important when
sequences of viruses exhibiting inter- or intrasubject variability are
to be quantified.
More recently, a new fluorogenic probe-based PCR methodology
(designated TaqMan; Roche Molecular Systems, Somerville, N.J.) has
been developed and used in virologic applications. This technique is a
real-time sequence detection system which employs a dual-labeled fluorogenic probe. The probe contains a fluorescent reporter at the 5'
end and a quencher at the 3' end. The use of this probe, combined with
the 5'-3' nuclease activity of Taq polymerase, allows direct
quantitation of the PCR product by the detection of the fluorescent
reporter released during the exponential phase of PCR amplification.
This technique is very simple and fast (it does not require a
postamplification step), able to quantify efficiently both RNA and DNA
nucleic acid species, potentially appropriate for routine application,
and at least as sensitive as other PCR-based applications (36, 37,
43, 48, 58, 64). Major drawbacks of real-time amplification are
presently the time-consuming and largely empiric work necessary for the
optimization of new applications and the inability to quantify variable sequences.
Overall, a wide range of molecular techniques are currently available
to the research community. Although most of them exhibit interesting
features for specific applications, theoretical considerations and
technical data suggest that none is the ideal quantitative method
appropriate for universal use in molecular virology, sufficiently flexible and reliable for both routine diagnostic applications and
investigation of the pathogenic mechanisms of viral diseases in
vivo and in vitro. In the light of this evidence, further
methodological research in this important area is still of great importance.
Natural history and pathogenicity studies of viral diseases have
largely employed quantitative molecular methods to assess viral nucleic
acids. These studies have supplied a profile of viral activity during
the different phases of acute and persistent viral infections,
contributed to a better understanding of virus-host interactions,
allowed the application of mathematical models to evaluate the intrahost viral dynamics, and, finally, provided a
theoretical basis for therapeutic antiviral intervention. This process
and the application of quantitative molecular methods to in vitro
studies have revolutionized research strategies in basic and medical
virology and have greatly influenced the diagnostic methodology of
human viral infections. For this principal reason and in view of a more
widespread use of quantitative molecular methods in virology in
the next few years, a more accurate understanding of the biological and
pathogenic correlates of the different quantitative indices obtained in
the study of viral infections may be of crucial importance.
Strategies to address the dynamics of systemic viral activity in
vivo.
In vivo, systemic viral activity is a formal entity that
consists of a sum of dynamic processes, including productive infection of target cells, release of virions outside the infected cell and
eventually in the blood compartment, and de novo infection of
permissive cells. The virus variables influencing the level of systemic
viral activity and cell-free virus dynamics include degree of viral
expression and host cell range (14); host variables include
the specific (humoral and cytotoxic) immune response and (as documented
in HIV-1 infection) polymorphism of genes coding for cell receptors of viruses.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
MINIREVIEW
INTRODUCTION
Top
Introduction
Conclusion
References
QUANTITATIVE TECHNIQUES FOR VIRAL NUCLEIC ACIDS
MOLECULAR CORRELATES AND DYNAMICS OF VIRAL ACTIVITY
|
Quantitative analysis of viral transcription in vitro and in vivo. The sensitivity and specificity performances of most quantitative methods have provided in the last few years a simple approach to the evaluation of gene transcription in vivo and in vitro. A precise understanding of the dynamics of virus transcription has allowed the direct evaluation of the latency-activity of herpesviruses. Recent studies of latent HCMV and herpes simplex virus type 1 and 2 infections have provided new insights into the dynamic pattern of virus expression, with potential implications for diagnosis and treatment (79, 83, 86, 94). In addition, the close correlation observed for HCMV infection between expression of the late HCMV transcripts in peripheral blood mononuclear cells (PBMCs) and levels of viral DNA molecules in plasma (12) has suggested a potential diagnostic use for quantitative analysis of HCMV mRNAs in nonblood samples such as bronchoalveolar cells (13). In other DNA viruses, such as HPVs, the potential pathogenic role of high levels of HPV type 16 expression is the subject of a recent investigation (41).
A typical example of the role of strategies aimed at revealing the pattern of viral transcripts in different phases of the infection comes from the comparative evaluation of infection activity in samples from patients with diverging disease progression. In HIV-1 infection, consistent evidence indicated that progression of disease is driven by an increase in viral load evaluated as cell-free plasma virus; it was unclear, however, to what extent this increase stems from the dysregulation of the molecular mechanisms governing virus gene expression at the transcriptional or posttranscriptional levels. To address this issue, several quantitative virologic parameters (including provirus transcriptional activity and splicing pattern) have been analyzed for subjects with nonprogressive HIV infection and compared with those of matching groups of progressor patients. It was observed not only that high levels of unspliced (US) and multiply spliced (MS) viral transcripts in PBMCs correlate with the decrease in CD4+ T cells (1, 6, 23, 27, 82), following the general trend of systemic HIV-1 activity, but also that MS mRNA levels in PBMCs are closely associated with the number of productively infected cells (6), since the half-life of this class of transcripts after administration of a potent protease inhibitor is very consistent with that of productively infected cells (39, 95). The transcriptional pattern observed during in vitro infections of T-cell lines, primary PBMCs, and monocytes/macrophages supports these findings. Quantitative molecular analysis has simplified the evaluation of the dynamic pattern of viral mRNAs in different target cells. This allows the relative contribution of different cell subsets to a given infection to be calculated, as demonstrated in HIV-1 infection (6). In this infection, the molecular data for virus expression in cultured macrophages (S. Aquaro, P. Bagnarelli, M. Clementi, T. Guenci, R. Calio, and C.-F. Perno, Dynamics of HIV replication in primary macrophages and modulation by antiviral drugs, presented at the 6th Conference on Retroviruses and Opportunistic Infections, Chicago, Ill., 31 January to 4 February 1999) have confirmed and extended previous analyses of HIV-1 infectivity (91), lending strong support to the hypothesis of a role for these cells as an effective long-term in vivo reservoir in HIV-1 infection (96). In this context, the accuracy of studies aimed at defining the cell tropism of a virus in vivo and the role of virus reservoirs in disease progression can be improved by evaluating, besides other indices of ongoing infection, the pattern of viral mRNAs and the dynamics of virus gene expression.Virus compartmentalization and tropism in vivo. An interesting aspect of viral dynamics studies, i.e., the presence of distinct compartments for viral infections in vivo, has been addressed using either biological or molecular approaches, including quantitative techniques for viral nucleic acids. The availability of methods to investigate this aspect has opened new prospects for the understanding of the pathogenesis of viral disease and of the mechanisms of virus transmission.
In HIV-1 infection, early data have shown that HIV-1 isolates from semen samples are frequently biologically unrelated to plasma isolates (93). More recently, remarkable sequence heterogeneity of viral quasispecies from plasma and genital secretions has been observed (101), together with the absence of a correlation between cell-free HIV-1 loads in plasma and those in semen (49). Taken together, these results suggest that plasma and semen are separate compartments and that local factors (including inflammation and other infections) may have significant effects on HIV-1 concentration in semen (and, consequently, on infectivity). Furthermore, several reports in the last few years have indicated that HCV is capable of infecting cells other than hepatocytes (15, 28, 52, 100, 102); this finding has suggested that accurate analysis of HCV tropism in vivo could be a useful strategy toward a greater understanding of the HCV pathogenic potential and the development of effective antiviral strategies. Although conflicting results have been obtained to date for the role of HCV in several human lymphoproliferative diseases (22, 24, 69), this example documents the potential of pathogenic research in medical virology by the application of quantitative methods.| |
QUANTITATIVE METHODS FOR VIRAL NUCLEIC ACIDS AND ANTIVIRAL TREATMENTS |
|---|
The introduction of new antiviral agents into preclinical and clinical use will greatly expand in the near future the treatment options available for acute and persistent viral infections. A major consequence of this new scenario will be the acute need for reliable parameters to evaluate the efficacy of therapies in real time and to monitor them (in some cases for months or years). Theoretical studies (57, 97) and early experimental evidence (4, 7, 11, 32, 39, 45, 59, 67, 95) have indicated unambiguously that most quantitative molecular methods are able to provide information on changes in systemic viral activity and that they are thus suitable for following up infected patients treated with antivirals. While there is no doubt of the usefulness of these methods in evaluating the efficacy of any antiviral treatment in vivo, several new questions have been raised. Among these, it seems important to verify whether (i) a single quantitative parameter (i.e., cell-free genome copy numbers in plasma) is sufficient to monitor viral infections during treatment or, alternatively, whether other indices (in addition to cell-free virus, viral transcripts in infected cells, viral load in different compartments, and proviral copy numbers in retroviral infections) are necessary to evaluate exhaustively the efficacy of antiviral compounds over time, and (ii) virologic indices other than those documenting the level of systemic viral activity are necessary to assess specific antiviral treatments. In other words, it is important to evaluate whether, in different infections, the plasma viral load may constitute a reliable index of selection of drug-resistant variants or whether more-specific quantitative assays are required.
Although potent antiretroviral therapy can at present control HIV-1 infection, suggesting that virus eradication might be at hand (72), a long-lived reservoir of infectious virus persists in CD4+ T cells. Furthermore, it has been shown that very high concentrations of protease inhibitors are necessary to suppress HIV-1 production in infected macrophages (74). Thus, even in patients under effective therapy and showing suppression of plasma RNA, HIV-1 DNA is easily recovered from PBMCs (98), and it has recently been shown that the dynamics of proviral HIV-1 DNA copy numbers in PBMCs from patients under effective antiretroviral therapy document the crucial role of latently infected cells (which are insensitive to current antiviral treatments) in HIV-1 persistence (29). More recently, decay of proviral HIV-1 DNA copy numbers and specific viral transcripts (US and MS) has been observed for PBMCs from patients with sustained response to the anti-HIV-1 treatment (26); this decay occurs in two phases, but the ratio between US and MS HIV-1 transcripts tends subsequently to remain stable for months, indicating that current therapies are unable to eradicate the infection, at least within a few decades. These data also suggest that measurements of different viral nucleic acid species are crucial to the accurate monitoring of antiviral therapies in HIV-1 infection.
In HCV infection, the involvement of a direct cytopathic effect or of an immune-mediated mechanism in the progression of the hepatic damage observed in chronic hepatitis C is still a matter of controversy. Similarly, conflicting results have been obtained for the pathogenic role of high HCV RNA levels in persistently infected subjects and for the capability of cell-free virus in plasma of documenting sustained response to interferon treatment (46, 47, 98). Recently, it has been observed that an accurate profile of viral replication can be obtained only by monthly testing (since longer intervals could miss viremia fluctuations, frequent in these patients) and that HCV RNA levels are more stable in asymptomatic HCV carriers than in patients with the biochemical activity of liver disease (78). Although early reports addressing the role of HCV viremia levels in subjects under treatment with interferon (or with combinations of ribavirin and interferon) have highlighted the potential usefulness of this parameter (90), further insights into this particular aspect will probably be obtained when the new antiviral compounds interfering with specific steps of the viral life cycle (such as the function of the protease-helicase HCV gene product) reach the phase of clinical evaluation. Thus, specific antiviral therapy and its monitoring could effectively contribute to the understanding of HCV disease pathogenesis.
In the routine diagnosis of HCMV infection, molecular techniques have largely replaced traditional culture-based techniques. In this infection, a high systemic viral load generally correlates with HCMV disease (11); this correlation is strong in the HIV-1-infected population and in organ transplantation recipients but less clear in allogeneic bone marrow transplantation recipients. A reduction in systemic HCMV load also correlates with response to the specific antiviral treatment (77), but (due to the scarce data currently available) further research is needed to evaluate the role of HCMV load as a surrogate marker for drug resistance in different clinical conditions.
Finally, considerable effort is currently being directed at the development of new antiviral chemotherapeutic agents. The introduction of potent viral inhibitors in monotherapy or combination therapy regimens has resulted in a marked improvement in clinical response in a small number of viral infections. However, selection of drug-resistant variants during long-term antiviral treatments is an outstanding clinical problem during treatment of persistent infections. In this context, monitoring of these therapies implies not only analysis of viral load and of other indices of viral expression but also the introduction of widespread drug sensitivity testing. Indeed, early experience in HIV-1 infection has documented that the routine use of reliable, real-time methods to test the sensitivity of replicative viral strains could drive a more effective therapeutic intervention in HIV-1 infection (38, 85). Since only incomplete data are available at present on the role of genotypic and phenotypic drug resistance testing in human infections other than those with HIV-1, thorough research into this specific aspect will be absolutely necessary when new compounds are proposed for routine use in medical virology.
In conclusion, considerable improvements in the laboratory monitoring of antiviral therapies have been achieved by the introduction of quantitative molecular techniques as routine diagnostic methods. However, the assessment of viremia levels alone does not appear sufficient to provide complete data for real-time information on treatment efficacy. The evaluation of other molecular parameters is necessary in some cases; moreover, the frequent selection of drug-resistant viral mutants requires the introduction of additional molecular assays for the early detection of the genotypic and phenotypic features of replicative viral strains.
| |
CONCLUDING REMARKS |
|---|
|
Top
Introduction
Conclusion
References
|
|---|
The data obtained in the last 10 years have unambiguously indicated that absolute quantitation of viral nucleic acid species is a crucial prerequisite for future developments in virology. The different features of the existing techniques for the assessment of viral nucleic acid copy numbers have allowed the widespread application of quantitative studies to themes of basic and medical virology. An important new area of research in virology has been developed which is directly dependent on the widespread application of highly sensitive and reliable quantitative methodologies. The availability of these methods has significantly contributed to the study of the natural history and pathogenesis of viral infections and virus-host relationships and to addressing the efficacy of antiviral therapies in real time. However, we need to consider that (i) further technical improvements are necessary since the available quantitative techniques are affected by important limitations, (ii) more than one quantitative index of viral activity is required in specific in vivo situations for a reliable evaluation of viral activity, and (iii) quantitative methods, albeit necessary, are not sufficient to address all the aspects relevant for a complete diagnosis in the monitoring of antiviral therapies, including virus resistance to inhibitory compounds. All this indicates that further research in this area is needed.
| |
ACKNOWLEDGMENTS |
|---|
This study and the research activity of my group in the present field have been supported by grants from Istituto Superiore di Sanità (I.S.S.) (Progetto di Ricerca sull'AIDS e Progetto Epatite Virale), Consiglio Nazionale delle Ricerche (C.N.R.) (Progetto Biotecnologie), and Ministero dell'Università e della Ricerca Scientifica e Tecnologica (MURST).
| |
FOOTNOTES |
|---|
* Mailing address: Department of Biomedical Sciences, Section of Microbiology, University of Trieste, Via Alexander Fleming, 22, I-34100 Trieste, Italy. Phone: 39 040 6767186. Fax: 39 040 577435. E-mail: clementi{at}popcsi.unian.it.
| |
REFERENCES |
|---|
|
Top
Introduction
Conclusion
References
|
|---|
| 1. | Bagnarelli, P., C. Balotta, A. Valenza, F. Mazzola, M. C. Colombo, M. Violin, M. Galli, and M. Clementi. 1997. Patterns of HIV-1 transcripts in peripheral blood lymphocytes from long-term nonprogressors and typical progressor patients. J. Acquir. Immune Defic. Syndr. 15(Suppl. I):S69-S71. |
| 2. | Bagnarelli, P., M. Candela, A. Valenza, A. Manzin, L. Solforosi, F. Mazzola, L. Butini, M. Montroni, A. Gabrielli, P. E. Varaldo, and M. Clementi. 1996. Dynamic features of human immunodeficiency virus type 1 (HIV-1) viremia: kinetics of cell-free HIV RNA after therapeutic plasma exchange. J. Infect. Dis. 176:801-804. |
| 3. |
Bagnarelli, P.,
S. Menzo,
A. Valenza,
A. Manzin,
M. Giacca,
F. Ancarani,
G. Scalise,
P. E. Varaldo, and M. Clementi.
1992.
Molecular profile of human immunodeficiency virus type 1 infection in symptomless patients and in patients with AIDS.
J. Virol.
66:7328-7335 |
| 4. | Bagnarelli, P., S. Menzo, A. Valenza, S. Paolucci, S. Petroni, G. Scalise, R. Sampaolesi, A. Manzin, P. E. Varaldo, and M. Clementi. 1995. Quantitative molecular monitoring of human immunodeficiency virus type 1 activity during therapy with specific antiretroviral compounds. J. Clin. Microbiol. 33:16-23[Abstract]. |
| 5. |
Bagnarelli, P.,
A. Valenza,
S. Menzo,
A. Manzin,
G. Scalise,
P. E. Varaldo, and M. Clementi.
1994.
Dynamics of molecular parameters of human immunodeficiency virus type 1 activity in vivo.
J. Virol.
68:2495-2502 |
| 6. | Bagnarelli, P., A. Valenza, S. Menzo, R. Sampaolesi, P. E. Varaldo, L. Butini, M. Montroni, C.-F. Perno, S. Aquaro, D. Mathez, J. Leibowitch, C. Balotta, and M. Clementi. 1996. Dynamics and modulation of human immunodeficiency virus type 1 transcripts in vitro and in vivo. J. Virol. 70:7603-7613[Abstract]. |
| 7. | Ballardini, G., A. Manzin, F. Giostra, R. Francesconi, P. Groff, A. Grassi, L. Solforosi, S. Ghetti, D. Zauli, M. Clementi, and F. B. Bianchi. 1997. Quantitative liver parameters of HCV infection: relation to HCV genotypes, viremia, and response to interferon treatment. J. Hepatol. 26:779-786[CrossRef][Medline]. |
| 8. |
Barany, F.
1991.
Genetic disease detection and DNA amplification using cloned thermostable ligase.
Proc. Natl. Acad. Sci. USA
88:189-193 |
| 9. | Bell, J. I. 1999. Clinical research is dead; long live clinical research. Nat. Med. 5:477-478[CrossRef][Medline]. |
| 10. | Berger, A., J. Braner, H. W. Doerr, and B. Weber. 1998. Quantification of viral load: clinical relevance for human immunodeficiency virus, hepatitis B virus and hepatitis C virus infection. Intervirology 41:24-34[CrossRef][Medline]. |
| 11. |
Boeckh, M., and G. Boivin.
1998.
Quantitation of cytomegalovirus: methodologic aspects and clinical applications.
Clin. Microbiol. Rev.
11:533-554 |
| 12. | Boivin, G., J. Handfield, E. Toma, R. Lalonde, and M. G. Bergeron. 1999. Expression of the late cytomegalovirus (CMV) pp150 transcript in leukocytes of AIDS patients is associated with high viral DNA load in leukocytes and presence of CMV DNA in plasma. J. Infect. Dis. 179:1101-1107[CrossRef][Medline]. |
| 13. | Boivin, G., C. A. Olson, M. R. Quirk, B. Kringstad, M. I. Hertz, and M. C. Jordan. 1996. Quantitation of cytomegalovirus DNA and characterization of viral gene expression in bronchoalveolar cells of infected patients with or without pneumonitis. J. Infect. Dis. 173:1304-1312[Medline]. |
| 14. |
Bonhoeffer, S.,
R. M. May,
G. M. Shaw, and M. A. Nowak.
1997.
Virus dynamics and drug therapy.
Proc. Natl. Acad. Sci. USA
94:6971-6976 |
| 15. | Bouffard, P., P. H. Hayashi, R. Acevedo, M. Levy, and J. B. Zeldis. 1992. Hepatitis C virus infection is detected in a monocyte/macrophage subpopulation of peripheral blood mononuclear cells of infected patients. J. Infect. Dis. 166:1276-1280[Medline]. |
| 16. | Bowen, E. F., C. A. Sabin, P. Wilson, P. D. Griffiths, C. C. Davey, M. A. Johnson, and V. C. Emery. 1997. Cytomegalovirus (CMV) viraemia detected by polymerase chain reaction identifies a group of HIV-positive patients at high risk of CMV disease. AIDS 11:889-893[CrossRef][Medline]. |
| 17. |
Cao, Y.,
L. Qin,
L. Zhang,
J. Safrit, and D. D. Ho.
1995.
Virologic and immunologic characterization of long-term survivors of human immunodeficiency virus type 1 infection.
N. Engl. J. Med.
332:201-208 |
| 18. | Clementi, M., P. Bagnarelli, S. Menzo, A. Valenza, A. Manzin, and P. E. Varaldo. 1993. Clearance of HIV viremia after seroconversion. Lancet 341:315-316[Medline]. |
| 19. | Clementi, M., P. Bagnarelli, A. Manzin, and S. Menzo. 1994. Competitive polymerase chain reaction and analysis of viral activity at the molecular level. Genet. Anal. Tech. Appl. 11:1-6[Medline]. |
| 20. | Clementi, M., S. Menzo, P. Bagnarelli, A. Manzin, A. Valenza, and P. E. Varaldo. 1993. Quantitative PCR and RT-PCR in virology. PCR Methods Appl. (CSH) 2:191-196. |
| 21. | Clementi, M., S. Menzo, P. Bagnarelli, A. Valenza, S. Paolucci, R. Sampaolesi, A. Manzin, and P. E. Varaldo. 1996. Clinical use of quantitative molecular methods in studying human immunodeficiency virus type 1 infection. Clin. Microbiol. Rev. 9:135-147[Medline]. |
| 22. | Collier, J. D., B. Zanke, M. Moore, G. Kessler, M. Krajden, F. Shepherd, and J. Heathcote. 1999. No association between hepatitis C and B-cell lymphoma. Hepatology 29:1259-1261[CrossRef][Medline]. |
| 23. | Comar, M., G. Marzio, P. D'Agaro, and M. Giacca. 1996. Quantitative dynamics of HIV type 1 expression. AIDS Res. Hum. Retrovir. 12:117-126[Medline]. |
| 24. | Dammacco, F., P. Gatti, and D. Sansonno. 1998. Hepatitis C virus infection, mixed cryoglobulinemia, and non-Hodgkin's lymphoma: an emerging picture. Leuk. Lymphoma 31:463-476[Medline]. |
| 25. | Fanning, L., E. Kenny, M. Sheehan, B. Cannon, M. Whelton, J. O'Connell, J. K. Collins, and F. Shanahan. 1999. Viral load and clinicopathological features of chronic hepatitis C (1b) in a homogeneous patient population. Hepatology 29:904-907[CrossRef][Medline]. |
| 26. |
Furtado, M. R.,
D. S. Callaway,
J. P. Phair,
K. J. Kunstman,
J. L. Stanton,
C. A. Macken,
A. S. Perelson, and S. M. Wolinsky.
1999.
Persistence of HIV-1 transcription in peripheral-blood mononuclear cells in patients receiving potent antiretroviral therapy.
N. Engl. J. Med.
340:1614-1622 |
| 27. | Furtado, M. R., L. A. Kingsley, and S. M. Wolinsky. 1995. Changes in the viral mRNA expression pattern correlate with a rapid rate of CD4+ T-cell number decline in human immunodeficiency virus type 1-infected individuals. J. Virol. 69:2092-2100[Abstract]. |
| 28. | Gabrielli, A., A. Manzin, M. Candela, M. L. Caniglia, S. Paolucci, M. G. Danieli, and M. Clementi. 1994. Active hepatitis C virus infection in bone marrow and peripheral blood mononuclear cells from patients with mixed cryoglobulinemia. Clin. Exp. Immunol. 97:87-93[Medline]. |
| 29. | Galli, M., C. Balotta, L. Meroni, M. C. Colombo, L. Papagno, P. Bagnarelli, L. Testa, S. Varchetta, L. Colombo, M. Moroni, A. d'Arminio Monforte, M. Clerici, and M. Clementi. 1998. Early increase in cell-associated HIV-1 DNA in patients on highly active antiretroviral therapy. AIDS 12:2500-2502[Medline]. |
| 30. | Gallinella, G., M. Zerbini, M. Musiani, S. Venturoli, G. Gentilomi, and E. Manaresi. 1997. Quantitation of parvovirus B19 DNA sequences by competitive PCR: differential hybridization of the amplicons and immunoenzymatic detection on microplate. Mol. Cell. Probes 11:127-133[CrossRef][Medline]. |
| 31. | Gerken, G., J. Gomes, P. Lampertico, M. Colombo, T. Rothaar, M. Trippler, and G. Colucci. 1998. Clinical evaluation and applications of the Amplicor HBV Monitor test, a quantitative HBV DNA PCR assay. J. Virol. Methods 74:155-165[CrossRef][Medline]. |
| 32. | Gerna, G., E. Percivalle, F. Baldanti, A. Sarasini, M. Zavattoni, M. Furione, M. Torsellini, and M. G. Revello. 1998. Diagnostic significance and clinical impact of quantitative assays for diagnosis of human cytomegalovirus infection/disease in immunocompromised patients. New Microbiol. 21:293-308[Medline]. |
| 33. |
Gilliland, G.,
S. Perrin,
K. Blanchard, and H. F. Bunn.
1990.
Analysis of cytokine mRNA and DNA: detection and quantitation by competitive polymerase chain reaction.
Proc. Natl. Acad. Sci. USA
87:2725-2729 |
| 34. | Giostra, F., A. Manzin, M. Lenzi, R. Francesconi, L. Solforosi, P. Manotti, L. Muratori, D. Zauli, M. Clementi, and F. B. Bianchi. 1996. Low hepatitis C viremia levels in patients with anti-liver/kidney microsomal antibody type 1 positive chronic hepatitis. J. Hepatol. 25:433-438[CrossRef][Medline]. |
| 35. | Gupta, P., L. Kingsley, J. Armstrong, M. Ding, M. Cottril, and C. Rinaldo. 1993. Enhanced expression of human immunodeficiency virus type 1 correlated with development of AIDS. Virology 196:586-595[CrossRef][Medline] |
| 36. | Gut, M., C. M. Leutenegger, J. B. Huder, N. C. Pedersen, and H. Lutz. 1999. One-tube fluorogenic reverse transcription-polymerase chain reaction for the quantitation of feline coronaviruses. J. Virol. Methods 77:37-46[CrossRef][Medline]. |
| 37. | Hawrami, K., and J. Breuer. 1999. Development of a fluorogenic polymerase chain reaction assay (TaqMan) for the detection and quantitation of varicella zoster virus. J. Virol. Methods 79:33-40[CrossRef][Medline]. |
| 38. |
Hertogs, K.,
M. P. de Bethune,
V. Miller,
T. Ivens,
P. Schel,
A. Van Cauwenberge,
C. Van Den Eynde,
V. Van Gerwen,
H. Azijn,
M. Van Houtte,
F. Peeters,
S. Staszewski,
M. Conant,
S. Bloor,
S. Kemp,
B. Larder, and R. Pauwels.
1998.
A rapid method for simultaneous detection of phenotypic resistance to inhibitors of protease and reverse transcriptase in recombinant human immunodeficiency virus type 1 isolates from patients treated with antiretroviral drugs.
Antimicrob. Agents Chemother.
42:269-276 |
| 39. | Ho, D. D., A. U. Neuman, A. S. Perelson, W. Chen, J. M. Leonard, and M. Markowitz. 1995. Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature (London) 373:123-126[CrossRef][Medline]. |
| 40. |
Hockett, R. D.,
J. M. Kilby,
C. A. Derdeyn,
M. S. Saag,
M. Sillers,
K. Squires,
S. Chiz,
M. A. Nowak,
G. M. Shaw, and R. P. Bucy.
1999.
Constant mean viral copy number per infected cell in tissue regardless of high, low, or undetectable plasma HIV RNA.
J. Exp. Med.
189:1545-1554 |
| 41. | Hsu, E. M., P. J. McNicol, F. B. Guijon, and M. Paraskevas. 1993. Quantification of HPV-16 E6-E7 transcription in cervical intraepithelial neoplasia by reverse transcriptase polymerase chain reaction. Int. J. Cancer 55:397-401[Medline]. |
| 42. |
Jeffery, K. J. M.,
K. Usuku,
S. E. Hall,
W. Matsumoto,
G. P. Taylor,
J. Procter,
M. Bunce,
G. S. Ogg,
K. I. Welsh,
J. N. Weber,
A. L. Lloyd,
M. A. Nowak,
M. Nagai,
D. Kodama,
S. Izumo,
M. Osame, and C. R. M. Bangham.
1999.
HLA alleles determine human T-lymphotropic virus-I (HTLV-I) proviral load and the risk of HTLV-I-associated myelopathy.
Proc. Natl. Acad. Sci. USA
96:3848-3853 |
| 43. | Kawai, S., O. Yokosuka, T. Kanda, F. Imazeki, Y. Maru, and H. Saisho. 1999. Quantification of hepatitis C virus by TaqMan PCR: comparison with HCV Amplicor Monitor assay. J. Med. Virol. 58:121-126[CrossRef][Medline]. |
| 44. | Kogan, D. L., M. Burroughs, S. Emre, T. Fishbein, A. Moscona, C. Ramson, and B. L. Schneider. 1999. Prospective longitudinal analysis of quantitative Epstein-Barr virus polymerase chain reaction in pediatric liver transplant recipients. Transplantation 67:1068-1070[CrossRef][Medline]. |
| 45. | Lam, N. P., A. U. Neumann, D. R. Gretch, T. E. Wiley, A. S. Perelson, and T. J. Layden. 1997. Dose-dependent acute clearance of hepatitis C genotype 1 virus with interferon alfa. Hepatology 26:226-231[CrossRef][Medline]. |
| 46. | Lau, J. Y., G. L. Davis, J. Kniffen, K. P. Qian, M. S. Urdea, C. S. Chan, M. Mizokami, P. D. Neuwald, and J. C. Wilber. 1993. Significance of serum hepatitis C virus RNA levels in chronic hepatitis C. Lancet 341:1501-1504[CrossRef][Medline]. |
| 47. | Lau, J. Y., M. Mizokami, T. Ohno, D. A. Diamond, J. Kniffen, and G. L. Davis. 1993. Discrepancy between biochemical and virological responses to interferon-alpha in chronic hepatitis C. Lancet 342:1208-1209[CrossRef][Medline]. |
| 48. | Leutenegger, C. M., D. Klein, R. Hofmann-Lehmann, C. Mislin, U. Hummel, J. Boni, F. Boretti, W. H. Guenzburg, and H. Lutz. 1999. Rapid feline immunodeficiency virus provirus quantitation by polymerase chain reaction using the TaqMan fluorogenic real-time detection system. J. Virol. Methods 78:105-116[CrossRef][Medline]. |
| 49. | Liuzzi, G., A. Chirianni, M. Clementi, P. Bagnarelli, A. Valenza, P. T. Cataldo, and M. Piazza. 1996. Analysis of HIV-1 load in blood, semen and saliva: evidence for different viral compartments in a cross-sectional and longitudinal study. AIDS 10:F51-F56[Medline]. |
| 50. |
Lo, Y. M.,
L. Y. Chan,
K. W. Lo,
S. F. Leung,
J. Zhang,
A. T. Chan,
J. C. Lee,
N. M. Hjelm,
P. J. Johnson, and D. P. Huang.
1999.
Quantitative analysis of cell-free Epstein-Barr virus DNA in plasma of patients with nasopharyngeal carcinoma.
Cancer Res.
59:1188-1191 |
| 51. |
Manzin, A.,
P. Bagnarelli,
S. Menzo,
F. Giostra,
M. Brugia,
R. Francesconi,
F. B. Bianchi, and M. Clementi.
1994.
Quantitation of hepatitis C virus genome molecules in plasma samples.
J. Clin. Microbiol.
32:1939-1944 |
| 52. |
Manzin, A.,
M. Candela,
S. Paolucci,
M. L. Caniglia,
A. Gabrielli, and M. Clementi.
1994.
Presence of hepatitis C virus (HCV) genomic RNA and viral replicative intermediates in bone marrow and peripheral blood mononuclear cells from HCV-infected patients.
Clin. Diagn. Lab. Immunol.
1:160-163 |
| 53. | Manzin, A., M. Candela, L. Solforosi, A. Gabrielli, and M. Clementi. 1999. Dynamics of hepatitis C viremia after plasma exchange. J. Hepatol. 31:389-393[CrossRef][Medline]. |
| 54. | Manzin, A., L. Solforosi, D. Bianchi, A. Gabrielli, F. Giostra, S. Bruno, and M. Clementi. 1995. Virus load in samples from hepatitis C virus (HCV)-infected patients with various clinical conditions. Res. Virol. 146:279-284[CrossRef][Medline]. |
| 55. | Manzin, A., L. Solforosi, M. Candela, G. Cherubini, G. Piccinini, M. Brugia, A. Gabrielli, and M. Clementi. 1996. Hepatitis C virus infection and cryoglobulinemia: assessment of HCV RNA copy numbers in supernatant, cryoprecipitate and non-liver cells. J. Viral Hepatitis 3:285-292[Medline]. |
| 56. | Manzin, A., L. Solforosi, F. Giostra, F. B. Bianchi, S. Bruno, S. Rossi, A. Gabrielli, M. Candela, E. Petrelli, and M. Clementi. 1997. Quantitative analysis of hepatitis C virus activity in different groups of untreated patients. Arch. Virol. 142:465-472[CrossRef][Medline]. |
| 57. | Marschner, I. C. 1998. Design of HIV viral dynamics studies. Stat. Med. 17:2421-2434[CrossRef][Medline]. |
| 58. |
Martell, M.,
J. Gomez,
J. I. Esteban,
S. Sauleda,
J. Quer,
B. Cabot,
R. Esteban, and J. Guardia.
1999.
High-throughput real-time reverse transcription-PCR quantitation of hepatitis C virus RNA.
J. Clin. Microbiol.
37:327-332 |
| 59. | Mathez, D., P. Bagnarelli, I. Gorin, C. Katlama, G. Pialoux, G. Saimot, P. Tubiana, P. De Truchis, J.-P. Chauvin, R. Mills, R. Rode, M. Clementi, and J. Leibowitch. 1997. Reductions in viral load and increases in T lymphocyte numbers in treatment of naive patients with advanced HIV-1 infection treated with ritonavir, zidovudine and zalcitabine triple therapy. Antivir. Ther. 2:175-183[Medline]. |
| 60. |
Mellors, J. W.,
L. A. Kingsley,
C. R. Rinaldo,
J. A. Todd,
B. S. Hoo,
R. P. Kokka, and P. Gupta.
1995.
Quantitation of HIV-1 RNA in plasma predicts outcome after seroconversion.
Ann. Intern. Med.
122:573-579 |
| 61. | Mellors, J. W., C. R. Rinaldo, P. Gupta, R. M. White, J. A. Todd, and L. A. Kingsley. 1996. Prognosis in HIV-1 infection predicted by the quantity of virus in plasma. Science 272:1167-1170[Abstract]. |
| 62. |
Menzo, S.,
P. Bagnarelli,
M. Giacca,
A. Manzin,
P. E. Varaldo, and M. Clementi.
1992.
Absolute quantitation of viremia in human immunodeficiency virus infection by competitive reverse transcription polymerase chain reaction.
J. Clin. Microbiol.
30:1752-1757 |
| 63. |
Michael, N. L.,
M. Vahey,
D. S. Burke, and R. R. Redfield.
1992.
Viral DNA and mRNA expression correlate with the stage of human immunodeficiency virus (HIV) type 1 infection in humans: evidence for viral replication in all stages of HIV disease.
J. Virol.
66:310-316 |
| 64. | Morris, T., B. Robertson, and M. Gallagher. 1996. Rapid reverse transcription-PCR detection of hepatitis C virus RNA in serum by using the TaqMan fluorogenic detection system. J. Clin. Microbiol. 34:2933-2936[Abstract]. |
| 65. |
Neumann, A. U.,
N. P. Lam,
H. Dahari,
D. R. Gretch,
T. E. Wiley,
T. J. Layden, and A. S. Perelson.
1998.
Hepatitis C viral dynamics in vivo and the antiviral efficacy of interferon-alpha therapy.
Science
282:103-107 |
| 66. | Nolte, F. S. 1998. Branched DNA signal amplification for direct quantitation of nucleic acid sequences in clinical specimens. Adv. Clin. Chem. 33:201-235[Medline]. |
| 67. |
Nowak, M. A.,
S. Bonhoeffer,
A. M. Hill,
R. Boehme,
H. C. Thomas, and H. McDade.
1996.
Viral dynamics in hepatitis B virus infection.
Proc. Natl. Acad. Sci. USA
93:4398-4402 |
| 68. |
Oehlenschlager, F.,
P. Schwille, and M. Eigen.
1996.
Detection of HIV-1 RNA by nucleic acid sequence-based amplification combined with fluorescence correlation spectroscopy.
Proc. Natl. Acad. Sci. USA
93:12811-12816 |
| 69. | Ohsawa, M., N. Shingu, H. Miwa, H. Yoshihara, M. Kubo, H. Tsukuma, H. Teshima, M. Hashimoto, and K. Aozasa. 1999. Risk of non-Hodgkin's lymphoma in patients with hepatitis C virus infection. Int. J. Cancer 80:237-239[CrossRef][Medline]. |
| 70. |
Pantaleo, G.,
S. Menzo,
M. Vaccarezza,
C. Graziosi,
O. J. Cohen,
J. F. Demarest,
D. Montefiori,
J. M. Orenstein,
C. Fox,
L. K. Schrager,
J. B. Margolik,
S. Buchbinder,
J. V. Giorgi, and A. S. Fauci.
1995.
Studies in subjects with long-term progressive human immunodeficiency virus infection.
N. Engl. J. Med.
332:209-216 |
| 71. | Pawlotski, J. M., M. Martinot-Peignoux, J. D. Poveda, A. Bastie, V. La Breton, F. Darthuy, J. Remire, S. Erlinger, D. Dhumeaux, and P. Marcellin. 1999. Quantification of hepatitis C virus RNA in serum by branched DNA-based signal amplification assays. J. Virol. Methods 79:227-235[CrossRef][Medline]. |
| 72. | Perelson, A. S., P. Essunger, Y. Cao, M. Vesanen, A. Hurley, K. Saksela, M. Markowitz, and D. D. Ho. 1997. Decay characteristics of HIV-1-infected compartments during combination therapy. Nature (London) 387:188-191[CrossRef][Medline]. |
| 73. | Perelson, A. S., A. U. Neumann, M. Markowitz, J. M. Leonard, and D. D. Ho. 1996. HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time. Science 271:1582-1586[Abstract]. |
| 74. | Perno, C.-F., F. M. Newcomb, D. A. Davis, S. Aquaro, R. W. Humphrey, R. Caliò, and R. J. Yarchoan. 1998. Relative potency of protease inhibitors in monocytes/macrophages acutely and chronically infected with human immunodeficiency virus. J. Infect. Dis. 178:413-422[Medline]. |
| 75. | Piatak, M., M. S. Saag, L. C. Yang, S. J. Clark, J. C. Kappes, K.-C. Luk, B. H. Hahn, G. M. Shaw, and J. D. Lifson. 1993. High levels of HIV-1 RNA in plasma during all stages of infection determined by competitive PCR. Science 259:1749-1754. |
| 76. | Pistello, M., S. Menzo, M. Giorgi, L. Da Prato, G. Cammarota, M. Clementi, and M. Bendinelli. 1994. Competitive polymerase chain reaction for quantitating feline immunodeficiency virus load in infected cat tissues. Mol. Cell. Probes 8:229-234[CrossRef][Medline]. |
| 77. | Poirier-Toulemonde, A. S., B. M. Imbert-Marcille, V. Ferre-Aubineau, B. Besse, M. G. Le Roux, D. Cantarovich, and S. Billaudel. 1997. Successful quantification of cytomegalovirus DNA by competitive PCR and detection with capillary electrophoresis. Mol. Cell. Probes 11:11-23[CrossRef][Medline]. |
| 78. | Pontisso, P., G. Bellati, M. Brunetto, L. Chemello, G. Colloredo, R. Di Stefano, M. Nicoletti, M. G. Rumi, M. G. Ruvoletto, R. Soffredini, L. M. Valenza, and G. Colucci. 1999. Hepatitis C virus RNA profiles in chronically infected individuals: do they relate to disease activity? Hepatology 29:585-589[CrossRef][Medline]. |
| 79. |
Ramakrishnan, R.,
D. J. Fink,
G. Jiang,
P. Desai,
J. C. Glorioso, and M. Levine.
1994.
Competitive quantitative PCR analysis of herpes simplex virus type 1 DNA and latency-associated transcript RNA in latently infected cells of the rat brain.
J. Virol.
68:1864-1873 |
| 80. | Saiki, R. K., T. L. Bugawan, G. T. Horn, K. B. Mullins, and H. A. Erlich. 1986. Analysis of enzymatically amplified B-globin and HLA-Dqa DNA with allele specific oligonucleotide probes. Nature (London) 324:163-166[CrossRef][Medline]. |
| 81. |
Saiki, R. K.,
D. Gelfand,
S. Stoffel,
S. J. Scharf,
R. Higuel,
G. T. Horn,
K. B. Mullins, and H. A. Erlich.
1988.
Primer directed enzymatic amplification of DNA with a thermostable DNA polymerase.
Science
239:487-491 |
| 82. |
Saksela, K.,
C. Stevens,
P. Rubinstein, and D. Baltimore.
1994.
Human immunodeficiency virus type 1 mRNA expression in peripheral blood cells predicts disease progression independently of the number of CD4 lymphocytes.
Proc. Natl. Acad. Sci. USA
91:1104-1108 |
| 83. |
Sawtell, N. M.,
D. K. Poon,
C. S. Tansky, and R. L. Thompson.
1998.
The latent herpes simplex virus type 1 genome copy number in individual neurons is virus strain specific and correlates with reactivation.
J. Virol.
72:5343-5350 |
| 84. | Scadden, D. T., Z. Wang, and J. E. Groopman. 1992. Quantitation of plasma human immunodeficiency virus type 1 RNA by competitive polymerase chain reaction. J. Infect. Dis. 165:1119-1123[Medline]. |
| 85. | Schmit, J.-C., and B. Weber. 1997. Recent advances in antiretroviral therapy and HIV infection monitoring. Intervirology 40:304-321[Medline]. |
| 86. |
Slobedman, B., and E. S. Mocarski.
1999.
Quantitative analysis of latent human cytomegalovirus.
J. Virol.
73:4806-4812 |
| 87. | Spector, S. A., R. Wong, K. Hsia, M. Pilcher, and M. J. Stempien. 1998. Plasma cytomegalovirus (CMV) DNA load predicts CMV disease and survival in AIDS patients. J. Clin. Investig. 101:497-502[Medline]. |
| 88. |
Stevens, S. J.,
M. B. Vervoort,
A. J. van den Brule,
P. L. Meenhorst,
C. J. Meijer, and J. M. Middeldorp.
1999.
Monitoring of Epstein-Barr virus load in peripheral blood by quantitative competitive PCR.
J. Clin. Microbiol.
37:2852-2857 |
| 89. |
Swan, D. C.,
R. A. Tucker,
G. Tortolero-Luna,
M. F. Mitchell,
L. Wideroff,
E. R. Unger,
R. A. Nisenbaum,
W. C. Reeves, and J. P. Icenogle.
1999.
Human papillomavirus (HPV) DNA copy number is dependent on grade of cervical disease and HPV type.
J. Clin. Microbiol.
37:1030-1034 |
| 90. | Trabaud, M. A., F. Bailly, S. N. Si-Ahmed, P. Chevallier, M. Sepetjan, G. Colucci, and C. Trepo. 1997. Comparison of HCV RNA assays for the detection and quantification of hepatitis C virus RNA levels in serum of patients with chronic hepatitis C treated with interferon. J. Med. Virol. 52:105-112[CrossRef][Medline]. |
| 91. | Tsai, W. P., S. R. Conley, H. F. Kung, R. R. Garrity, and P. L. Nara. 1996. Preliminary in vitro growth cycle and transmission studies of HIV-1 in an autologous primary cell assay of blood-derived macrophages and peripheral blood mononuclear cells. Virology 26:205-216. |
| 92. |
Vener, T.,
M. Nygren,
A. Andersson,
M. Uhlen,
J. Albert, and J. Lundeberg.
1998.
Use of multiple competitors for quantification of human immunodeficiency virus type 1 RNA in plasma.
J. Clin. Microbiol.
36:1864-1870 |
| 93. | Vernazza, P. L., J. J. Eron, M. S. Cohen, C. M. van der Horst, L. Troiani, and S. A. Fiscus. 1994. Detection and biologic characterization of infectious HIV-1 in semen of seropositive men. AIDS 8:1325-1329[Medline]. |
| 94. | Wang, K., L. Pesnicak, and S. E. Strauss. 1997. Mutations in the 5' end of the herpes simplex virus type 2 latency-associated transcript (LAT) promoter affect LAT expression in vivo but not the rate of spontaneous reactivation of genital herpes. J. Virol. 71:7903-7910[Abstract]. |
| 95. | Wei, X., S. K. Gosh, M. E. Taylor, V. A. Johnson, E. A. Emini, P. Deutsch, J. D. Lifson, S. Bonhoefer, M. A. Nowak, B. H. Hahn, M. S. Saag, and G. M. Shaw. 1995. Viral dynamics in human immunodeficiency virus type 1 infection. Nature (London) 373:117-122[CrossRef][Medline]. |
| 96. | Wodarz, D., A. L. Lloyd, V. A. Jansen, and M. A. Nowak. 1999. Dynamics of macrophage and T cell infection by HIV. J. Theor. Biol. 196:101-113[CrossRef][Medline]. |
| 97. | Wu, H., A. A. Ding, and V. De Gruttola. 1998. Estimation of HIV dynamic parameters. Stat. Med. 17:2463-2485[CrossRef][Medline]. |
| 98. | Zeuzem, S., A. Franke, J. H. Lee, G. Hermann, B. Ruster, and W. K. Roth. 1996. Phylogenetic analysis of hepatitis C virus isolates and their correlation to viremia, liver function tests, and histology. Hepatology 24:1003-1009[CrossRef][Medline]. |
| 99. |
Zhang, L.,
B. Ramratnam,
K. Tenner-Racz,
Y. He,
M. Vesanen,
S. Lewin,
A. Talal,
P. Racz,
A. S. Perelson,
B. T. Korber,
M. Markowitz, and D. D. Ho.
1999.
Quantifying residual HIV-1 replication in patients receiving combination antiretroviral therapy.
N. Engl. J. Med.
340:1605-1613 |
| 100. | Zhu, T., N. Wang, A. Carr, D. S. Nam, R. Moor-Jankowski, D. A. Cooper, and D. D. Ho. 1996. Genetic characterization of human immunodeficiency virus type 1 in blood and genital secretions: evidence for viral compartmentalization and selection during sexual transmission. J. Virol. 70:3098-3107[Abstract]. |
| 101. | Zhender, G., L. Meroni, C. De Maddalena, S. Varchetta, G. Monti, and M. Galli. 1997. Detection of hepatitis C virus RNA in CD19 peripheral blood mononuclear cells of chronically infected patients. J. Infect. Dis. 176:1209-1214[Medline]. |
| 102. | Zignego, A. L., D. Macchia, M. Monti, V. Thiers, M. Mazzetti, M. Foschi, E. Maggi, S. Romagnani, P. Gentilini, and C. Brechot. 1992. Infection of peripheral mononuclear blood cells by hepatitis C virus. J. Hepatol. 15:382-386[CrossRef][Medline]. |
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
