Vertical HIV-1 transmission correlates with a high maternal viral load at delivery

Transmission of HIV-1 from an infected mother to her child occurs in around 20% of cases. Although maternal, immunological, and virological factors have been implicated in transmission, clear association is not yet well defined. For this reason, we have conducted a study to determine the relative contribution of the above-mentioned factors with special emphasis on quantitative viral load. We studied 67 HIV-1-infected mothers during pregnancy and labor and their 69 newborns (two sets of twins) from two university hospitals in Barcelona. Plasma and cell samples were collected at delivery between January 1992 and May 1994, and HIV-1 RNA and p24 in plasma, CD4 cell counts, and tissue culture infectious doses (TCID) were measured. Diagnosis of infection in children was based on persistence of anti-HIV-1 antibodies at 18 months of age, a positive HIV-1 culture or polymerase chain reaction in two separate samples, or presence of signs or symptoms of AIDS before 18 months of age. Results showed a very high relationship between > 10(5)/ml viral RNA copies (odds ratio [OR] 22, 95% confidence interval [CI] 4.4-119.2, p < 0.00001), > 0.5 TCID (OR 17, 95% CI 2.1-139.7, p = 0.001), CDC B + C (OR 3.5, 95% CI 0.98-12.5, p = 0.055), < 400 CD4 cells (OR 4.1; 95% CL 1.1-15.4, p = 0.01) and transmission of HIV-1. In this study, a strong association between mother-to-child transmission of HIV-1 and a high maternal viral RNA load in plasma at delivery is demonstrated. Viral load, which is related to clinical and immunological status in the mother, is the main contributing factor for HIV-1 vertical transmission, and these findings may have global and even individual therapeutic implications.

CD8+ T-cell-mediated suppression of HIV replication in the first year of life: association with lower viral load and favorable early survival

OBJECTIVE AND DESIGN

To study the role and development of non-cytotoxic CD8+ T-cell-mediated suppression of HIV replication in early perinatal HIV infection in a prospective study of vertically infected infants. CD8 T-cell-mediated HIV suppression was measured several times during the first year of life and correlated with viral load, cytotoxic T-cell (CTL) activity, in vitro antibody production (IVAP) and clinical outcome.

METHODS

CD8+ T-cell-mediated HIV suppression was measured by comparing the amount of p24 antigen produced by endogenously infected lymphocytes with cultures of the same number of autologous CD4+ T cells from which CD8+ cells were removed immunomagnetically. CD8 viral suppressive activity (VSA) was defined as a > or = 50% reduction in p24 antigen in the cultures containing CD8+ cells.

RESULTS

CD8+ T-cell-mediated HIV VSA was detected in 11/16 infants in the first year of life, including six/nine infants studied before 6 months and as early as 3 weeks of age. Infants who demonstrated CD8 VSA had a lower early peak and 6-month 'setpoint' plasma HIV RNA concentration than infants who lacked CD8 VSA [1.51 versus 4.94 and 0.094 versus 0.639 x 10(6) copies/ml, respectively, and higher CD4 percentage at 1 year of age. Survival of infants lacking CD8 VSA (four/six were rapid progressors) was shorter than for infants who demonstrated CD8 VSA (none out of 10 were rapid progressors). CD8 VSA was present before CTL and before or at the same time as IVAP in two of two and 11 of 14 infants studied, respectively.

CONCLUSIONS

CD8+ T-cell-mediated VSA can be demonstrated in a large proportion of HIV-infected infants early in the course of infection. This non-cytolytic HIV-suppressive immune response appears to play an important protective role in the early control of perinatal HIV infection at a time when other immune responses are either absent or deficient.

Viral load in asymptomatic patients with CD4+ lymphocyte counts above 500 x 10(6)/l

BACKGROUND

HIV-1-infected patients with a CD4+ lymphocyte count > or = 500 x 10(6)/l may be selected for antiretroviral treatment when viral load is above a given cut-off point.

OBJECTIVES

To assess the stability of viral load measurement at CD4+ T-cell counts above 500 x 10(6)/l, and the proportion of patients selected for treatment if a cut-off point of 10,000 or 30,000 RNA copies/ml is used.

DESIGN AND METHODS

Seventy-eight consecutive asymptomatic antiretroviral-naive HIV-1-infected patients with CD4+ lymphocyte counts > or = 500 x 10(6)/l, presenting for previously scheduled medical visits as outpatients, were enrolled. None of the patients had suffered from symptomatic primary infection or seroconverted within 6 months before enrollment. Two blood samples separated by a 1-month interval [day -30 (screening) and day 0 (enrollment)] were collected in an EDTA tube. Plasma was separated and frozen at -70 degrees C within 4 h of collection. HIV-1 RNA was quantified by polymerase chain reaction. CD4+ T cells were measured by flow cytometry.

RESULTS

Viral load was fairly stable, and only four (13%) out of 30 pairs had a variation > or = 0.5 log10. At day -30 and day 0, log10 HIV RNA levels (mean +/- SD) were 4.24 +/- 0.7 and 4.35 +/- 0.87 log10 copies/ml plasma (P = 0.23). The difference of the mean was -0.11 (95% confidence interval, -0.28 to 0.07). At day 0 (n = 78) mean +/- SD value was 35730 +/- 73700 RNA copies/ml (range, < 200-438480; median, 9331; 25th and 75th percentiles, 1518 and 37193, respectively). In 13 patients (16%) the viral load was < 2000 copies RNA/ml. Seven out of 10 patients, who fulfilled the criteria of long-term non-progressors (LTNP), had viral load > 10,000 RNA copies/ml, and two patients had > 30,000 RNA copies/ml. Only two of the 13 patients with CD4+ T-cell counts > 750 x 10(6)/l had viral load > 10,000 copies/ml.

CONCLUSIONS

A single-point viral load assessment is enough in asymptomatic patients with CD4+ lymphocytes counts > or = 500 x 10(6)/l since plasma HIV RNA measurements obtained 1 month apart are fairly stable. Approximately 25% of these patients (including some patients with LTNP criteria) will be selected for treatment if 30,000 RNA copies/ml is used as cut-off point, and approximately 50% if the cut-off point is 10,000 RNA copies/ml. Viral load > or = 10,000 is very unusual in patients with CD4+ T-cell counts > 750 x 10(6)/l.

HIV antibodies: further questions and a plea for clarification

The existence of specific antibody/protein reactions is the crucial assumption underlying proof of HIV isolation, proof of HIV infection and the causative role of HIV in AIDS. However, since 1. antibodies which react with the 'HIV' proteins arise following allogenic stimuli in non-HIV-infected animals and humans, as well as in mice and humans with autoimmune disorders; antibodies to antigens from both mycobacteria and yeasts cross-react with HIV env and gag proteins; 2. individuals belonging to the AIDS risk groups are subjected to allogenic stimuli and have high levels of autoimmune antibodies, while the vast majority of patients in the AIDS risk groups are infected with either or both mycobacteria or yeasts; the evidence for the existence of HIV and its putative role in AIDS must be reappraised.

Janus considers the HIV pandemic--harnessing recent advances to enhance AIDS prevention

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Progression of HIV disease is associated with increased expression of Fc gammaRI and CR1 on alveolar macrophages

The expression of receptors for complement and the Fc region of immunoglobulin by alveolar macrophages (AM) constitutes a valuable aid to effector function of these cells. However, during HIV infection such expression may also act to increase binding of immune complexes, thus facilitating viral infection of these cells. This study was designed to determine whether changes in the expression of these receptors occurs in situ during HIV infection. Lung macrophages were isolated by bronchoalveolar lavage in groups of HIV+ subjects segregated on the basis of peripheral CD4 count. A group of normal subjects was also investigated. Expression of CR1 and Fc gammaRI was quantified by measuring the optical density of reaction product following controlled immunoperoxidase staining with MoAbs CD35 and CD64. Both CR1 and Fc gammaRI were increased over normal in all HIV+ subjects. This increase was progressive with advancing disease as determined by correlation with declining peripheral CD4 count. Comparison of asymptomatic and symptomatic subjects with HIV infection showed no difference in CR1 expression but a rise in Fc gammaRI expression in the latter group. An overall inverse correlation was also found between peripheral CD4 count and Fc gammaRI expression, but not CR1 expression. These data demonstrate a significant increase in the expression of these receptors on AM from HIV+ subjects, and show that this increase may occur before any symptoms in these patients.

Increased plasma levels of the C-C chemokine RANTES in patients with primary HIV-1 infection

To investigate the role played by chemokines in the natural history of human immunodeficiency virus (HIV) infection, we measured the plasma levels of RANTES. MIP-1 alpha and MIP-1 beta in a cohort of patients with primary HIV-1 infection (PHI) followed longitudinally. The cohort included 17 patients with well-documented history of acute HIV syndrome within two months of the first observation. The mean plasma concentration of RANTES, but not that of MIP-1 alpha or MIP-1 beta, was significantly higher in patients with PHI (192.3 ng/ml) than in five HIV-seronegative controls (8.0 ng/ml) studied during the same time period. Treatment of blood with a cocktail of drugs preventing platelet activation, followed by high-speed centrifugation, reduced the levels of RANTES by approximately 2 logs both in patients and in controls, indicating that the bulk of RANTES was released by platelets, which are known to store this chemokine in their alpha-granules, in the immediate aftermath of blood drawing. No correlation was seen between the levels of RANTES and the number of HIV genome equivalents in plasma. These data suggest that large amounts of pre-formed RANTES are stored in platelets and, possibly, in other blood cells during the early phases of HIV infection. The possible role of this HIV-suppressive chemokine in the control of viral replication during PHI remains to be established.

Comparison of EDTA and acid-citrate-dextrose collection tubes for detection of cytomegalovirus antigenemia and infectivity in leukocytes before and after storage

Duplicate blood samples collected in EDTA and acid-citrate-dextrose (ACD) were compared by cytomegalovirus (CMV) pp65 antigenemia and CMV infectivity on the day of sample collection and after 1 and 2 days of storage at 4 degrees C. No significant difference was detected between EDTA and ACD. However, CMV antigenemia was more sensitive than culture at all time points tested.

Antiretroviral effect of zidovudine-didanosine combination on blood and lymph nodes

OBJECTIVE

To evaluate the antiretroviral effect of a combination of zidovudine (ZDV) and didanosine (ddl) on plasma, peripheral blood mononuclear cells (PBMC) and lymph nodes after 24 weeks.

METHODS

Eight patients naive of antiretroviral therapy were followed by monthly blood samples and two surgical lymph-node biopsies taken at baseline and after 24 weeks. CD4+ T cells were counted monthly by flow cytometry. Plasma HIV-1 RNA was measured monthly by polymerase chain reaction (PCR). Infectious cellular viraemia was measured monthly by a culture technique. Proviral DNA titres in PBMC were measured by endpoint dilution PCR at baseline and 24 weeks. Infectious HIV-1 and proviral DNA titres were measured in the lymph-node mononuclear cells (LNMC). The total HIV-1 RNA content of lymph nodes was measured by PCR. In some cases, phenotypic resistance to ZDV was measured, and codon 215 and 74 mutations in PBMC and LNMC were analysed.

RESULTS

A mean increase in CD4 cell count of 122 x 10(6)/l, a mean decrease in HIV-1 RNA of 1.47 log10 in plasma and a mean decrease in HIV-1 DNA titre of 0.63 log10 were found after 24 weeks of therapy. Nevertheless, there were no statistically significant changes in the mean infectious HIV-1 titre in PBMC and LNMC, in the HIV-1 DNA titre in LNMC or in the total lymph-node HIV-1 RNA burden at week 24. Phenotypic or genotypic markers of drug resistance were rarely found in PBMC at week 24, although they were detected in LNMC from some patients.

CONCLUSION

A discrepancy in the therapeutic effect can be observed between lymphoid organs and blood after 24 weeks of therapy with ZDV and ddl. This difference could be explained by the insufficient antiretroviral potency of this combination facing the significant viral burden present in lymph nodes. Development of drug resistance in this compartment prior to blood can be demonstrated in some cases, although other mechanisms remain to be investigated in future studies to explain this difference.

Vitamin A levels and human immunodeficiency virus load in injection drug users

Although low plasma vitamin A levels are associated with increased mortality and higher vertical transmission during human immunodeficiency virus (HIV) infection, it is unknown whether plasma low vitamin A levels are a marker for circulating HIV load. We conducted a cross-sectional study within a prospective cohort study of injection drug users in order to evaluate the relationship between plasma vitamin A levels and HIV viral load. Plasma vitamin A level was measured by high-performance liquid chromatography. Infectious viral load was measured by quantitative microculture of serial fivefold dilutions of 10(6) peripheral blood mononuclear cells. A total of 284 HIV-infected adults (79 women, 205 men) were studied. Plasma vitamin A levels consistent with deficiency were found in 28.9% of adults. A total of 38.0% of women and 25.3% of men had vitamin A deficiency (P < 0.04). The median infectious viral load for the entire study population was 8 infectious units per million cells. No significant relationship between plasma vitamin A levels and infectious viral load was observed in these injection drug users. This study suggests that there is no correlation between HIV viral load and plasma vitamin A levels in injection drug users, and these variables may represent independent risk factors during HIV infection. HIV-infected adult women appear to be at higher risk of developing vitamin A deficiency.

Construct group

Patients with chronic hepatitis C respond differently when treated with interferon. We randomized 116 patients with chronic hepatitis C in order to compare two dosage regimens of recombinant interferon alpha 2a:3 MIU x 3 per week for 6 months (arm A) or 6 MIU x 3 per week for 3 months and then 3 MIU x 3 per week for 3 months (arm B). There were no significant differences concerning outcome between the two dose regimens: sustained clearance of HCV viremia 6 months after the end of treatment was obtained in 12/59 (20%) in group A compared with 18/57 (32%) in group B (p = 0.24). In patients with genotype 1a, 4/31 (13%), in genotype 1b, none of 9 (0%), 9/15 (60%) in genotype 2, and 17/58 (29%) in genotype 3, showed sustained clearance of HCV viremia 6 months after the end of treatment (p = 0.002). In a stepwise logistic regression analysis, only pretreatment viral load (p = 0.0001), genotype (p = 0.001) and age (p = 0.04) were identified as independent predictors of sustained clearance of HCV viremia. Liver histology as assessed by Knodell index was significantly improved in patients with sustained HCV RNA response 6 months after the end of treatment (5.2 +/- 2.2 vs 2.6 +/- 2.2, p < 0.001), but not in responders with relapse or in non-responders. In conclusion, stepwise logistic regression analysis showed that viral load, HCV genotype and age were the only independent predictors for sustained HCV RNA response.

The lymphocytosis-promoting agent pertussis toxin affects virus burden and lymphocyte distribution in the SIV-infected rhesus macaque

Pertussis toxin from the gram-negative bacterium Bordetella pertussis is an ADP-ribosylase that modifies Gi proteins in mammalian lymphocytes and inhibits their capacity to traffic from blood into lymphoid tissues. We used this compound to induce lymphocytosis in rhesus macaques and to study its effects on SIV infection. Pertussis toxin injected at 25 micrograms/kg induced a transient lymphocytosis that peaked 3-8 days after administration and caused a rapid, transient decrease in the frequency of infectious cells in blood as judged by in vitro virus isolation assays. Lymphocyte subsets were altered during the lymphocytosis interval and sustained changes in CD8+ T cell levels were noted as long as 53 days after pertussis toxin injection. In situ hybridization studies showed that pertussis toxin altered the distribution of viral RNA in lymph nodes during the interval of lymphocytosis, and caused long-term changes with decreased virus replication in some tissue specimens.

Virus load and neuropathology in the FIV model

The FIV (feline immunodeficiency virus) induces in cats brain changes presenting similarities with those observed in human immunodeficiency virus infection. This FIV model was used to study the relationship between viral load in brain, in lymphoid organs and central nervous system (CNS) changes during the early and late stages of infection. Early brain changes were analyzed in animals experimentally infected with two different FIV isolates and sacrificed at 7 and 15 days, 1, 2, 6, and 12 months post inoculation (p.i.). Late CNS abnormalities were analyzed in naturally FIV-infected cats referred to the Veterinary School of Nantes. For each animal, one cerebral hemisphere was fixed and examined using routine techniques. The characterization of FIV replicating cells by in situ hybridization was performed on the other half frozen hemisphere on sections performed in the anterior and the median regions of the brain. During the early stages of infection, moderate gliosis with glial nodules and sometimes white matter pallor and meningitis were associated with few infected cells scattered in the brain. Infection was an early event as infected cells could be detected in brain at 7 p.i. For each cat, these findings were found identical in the two analyzed areas. During the late stages, brain lesions and the number of virus replicating cells increased especially in animals with perivascular infiltrates. The multinucleated giant cells encephalitis was never observed and the number of FIV replicating cells scattered in the whole brain was always low. This discrepancy between the number of replicating cells and the brain lesions, corroborates the hypotheses suggesting that brain injuries may be mediated via diffusive factors and amplification processes through cytokine cascades and cell activations.

Analysis of HIV-1 load in blood, semen and saliva: evidence for different viral compartments in a cross-sectional and longitudinal study

OBJECTIVES

To quantify the HIV-1 load (measured as copies of viral RNA/ml using competitive reverse transcription-polymerase chain reaction) in blood, semen and saliva and to look for relationships between the viral burden, the clinical and immunological status and antiretroviral therapy.

METHODS

Peripheral blood, semen and whole saliva samples were collected from 26 anti-HIV-1-seropositive patients selected for a cross-sectional study. Nine of the 26 patients provided samples of the three biological fluids for a longitudinal study.

RESULTS

HIV-1 RNA was detected in 26 out of 26 samples of plasma, in 25 out of 26 samples of semen and in 24 out of 25 samples of saliva. The median number of HIV-1 copies in plasma was 14 817/ml (range: 167-254 880), in semen was 515/ml (range: 0-196 050) and in saliva was 162/ml (range: 0-72 080). The viral load in semen and in saliva was significantly lower than in plasma (P < 0.0001). The HIV-1 RNA levels in plasma and in saliva were correlated (P < 0.05), but levels in semen were not correlated with either plasma or saliva levels. The HIV-1 copy number in plasma was significantly higher in symptomatic patients than in asymptomatic subjects (P < 0.05). Plasma and saliva HIV-1 RNA levels were higher in subjects with a CD4+ cell count < 200 x 10(6)/l than in subjects with a CD4+ cell count > 200 x 10(6)/l (P < 0.05). The HIV-1 RNA load in either plasma, semen or saliva is not related to antiretroviral therapy.

CONCLUSIONS

The absence of a correlation between plasma and semen loads suggests that semen and blood are distinct viral compartments. Viral load in semen is not related to the clinical stage of HIV infection or to the CD4+ lymphocyte count. Consequently, HIV-1-infected subjects are potentially infectious at all stages of immuno-deficiency and adequate precautions must always be taken to prevent the sexual transmission of HIV.

HIV viral dynamics

BACKGROUND

Elucidation of the underlying rapid turnover of virus and HIV infected cells in vivo was perhaps the most informative and exciting discovery in HIV and AIDS research in the last few years. This observation, based on the rapid drop in virus load following antiviral drug therapy promises to change significantly the way we view important aspects of interaction of the virus and its host. As a result, the paradigm for HIV infection has shifted from considering the long period of clinical latency as one of viral inactivity, to viewing it as an active steady state of constant virus replication and cell death. This period should also be viewed as an integral part of the disease process, not simply a prolog to frank AIDS.

METHODS

Here, I discuss the theoretical basis of the steady state model of HIV infection as well as its important consequences for understanding and controlling HIV pathogenesis. These include the significance of genetic variation and the establishment and evolution of the virus quasispecies, the evolution of resistance of the virus to antiviral therapy, and the theoretical and practical significance of virus load measurements. Emphasis is on discussion of recent developments as well as areas where our understanding still has significant gaps.

The treatment of antiretroviral-naive subjects with the 3TC/zidovudine combination: a review of North American (NUCA 3001) and European (NUCB 3001) trials

OBJECTIVE

The compound (-)-2',3'-dideoxy-3'-thiacytidine (3TC, lamivudine) is a nucleoside analogue with potent in vitro antiretroviral activity, synergy with zidovudine, activity against zidovudine-resistant isolates and minimal cytotoxicity. In early-phase studies, 3TC had a favourable pharmacokinetic profile, was well tolerated by those with HIV infection, and had a modest effect on HIV-1 p24 antigen levels. Although resistance to 3TC monotherapy develops rapidly, the activity of the drug persists. However, zidovudine-resistant virus, in which the 3TC-resistance mutation is selected for, regains phenotypic sensitivity to zidovudine. Therefore, 3TC and zidovudine are a logical combination to evaluate as initial therapy in treatment-naive HIV-1 infected individuals.

DESIGN

Two randomized controlled trials, one in Europe and one in North America, evaluated 3TC in combination with zidovudine and compared this combination to zidovudine monotherapy. In the North American study, 3TC monotherapy was also evaluated. In both studies, subjects entered having received less than 4 weeks of zidovudine therapy and no other previous antiretroviral treatments. In the European study, subjects had CD4 cell counts of 100-400/mm3 and received blinded therapy for 24 weeks; they were then offered open-label 3TC and zidovudine for a further 24-week period. In the North American study, initial patient CD4 cell counts were 200-500/mm3, and blinded treatment continued for 52 weeks. Endpoints measured included CD4 cell counts and HIV-1 RNA in plasma, in addition to clinical and laboratory adverse events.

RESULTS

In both studies, the combination of 3TC and zidovudine resulted in rises in CD4 counts of 75-85 cells/mm3 that were sustained at 48-60 cells/mm3 above base-line at 48-52 weeks. Effects on HIV-1 RNA levels in plasma also persisted through 48 and 52 weeks at approximately a 90% reduction (1 log10 decrease) from baseline. In the European study, the combination was superior to zidovudine alone over the first 24 weeks, as measured by CD4 and HIV-1 RNA effects, and the addition of 3TC to zidovudine after 24 weeks resulted in a subsequent increase in the mean CD4 count of 39 cells/mm3. In the North American study, the combination of 3TC and zidovudine was better than zidovudine monotherapy when considering the effect on CD4 cells or HIV-1 RNA through 24 weeks. When these treatment groups were compared, using an average of the mean change from baseline of the CD4 counts and HIV-1 RNA levels over that last three study time points (44, 48 and 52 weeks), the combination treatments remained superior to zidovudine alone. In neither study did the addition of 3TC to zidovudine result in additional toxicity.

SUMMARY

In two independent studies in patients with limited antiretroviral treatment experience, remarkably similar results were obtained when 3TC/zidovudine in combination was compared to zidovudine monotherapy, demonstrating sustained antiretroviral and immunological effects of the combination over the 48 and 52 weeks of study.

Efficacy of triple combination therapy with zidovudine (ZDV) plus zalcitabine (ddC) plus lamivudine (3TC) versus double (ZDV+3TC) combination therapy in patients previously treated with ZDV+ddC

OBJECTIVE

To evaluate the immunological and virological efficacy of triple combination therapy with zidovudine (ZDV) plus zalcitabine (ddC) plus lamivudine (3TC) and a double (ZDV+3TC) combination therapy in patients previously treated with ZDV plus ddC.

DESIGN

A 6-month follow-up open-label randomized study was undertaken in 46 HIV-1-infected patients previously treated for at least 6 months with ZDV plus ddC, who were allocated to receive either ZDV/ddC/3TC (n = 15) or ZDV/3TC (n = 15) or to continue with the ZDV/ddC regimen (control group; n = 16).

METHODS

Changes in CD4+ cell counts and plasma viral load (VL) were analysed with analysis of variance. Sequencing of the reverse transcriptase gene was performed in a subset of 3TC-treated patients.

RESULTS

Mean CD4+ cell counts increased significantly above baseline in both 3TC regimens whereas counts decreased in the control group. Significant plasma VL reduction was achieved in both 3TC combination therapy groups at weeks 4 and 24 compared with the control group. Coexistence of mutations conferring resistance to ZDV and 3TC were found in patients from both 3TC treatment groups.

CONCLUSIONS

Both therapy strategies, switching ddC to 3TC or adding 3TC, significantly improved the virological and immunological efficacy compared with continuing ZDV/ddC. Our results support the use of 3TC in patients previously treated with the ZDV/ddC combination.

Increased plasma human immunodeficiency virus type 1 burden following antigenic challenge with pneumococcal vaccine

Primary factors that influence virus burden during human immunodeficiency virus type 1 (HIV-1) disease progression remain a fundamental issue in pathogenesis. Because pneumococcal vaccine is routinely given to HIV-1-infected patients and replication of HIV-1 within CD4 T cells is dependent on the activation state of the cell, it was investigated whether the T cell activation that enhances the immune response to vaccines may also enhance HIV-1 replication. Vaccination of asymptomatic HIV-1-infected patients led to rapid and significant increases in virus burden in some patients. The magnitude of these increases correlated significantly with the extent of the antibody response to the vaccination. Thus, antigenic stimulation by vaccines designed to prevent secondary infections may promote HIV-1 replication in certain patients. These findings provide a window for examining HIV-1 pathogenesis and for determining the appropriate preventive measures against other diseases in HIV-1-infected persons.

Effectiveness of 3TC in HIV clinical trials may be due in part to the M184V substitution in 3TC-resistant HIV-1 reverse transcriptase

OBJECTIVE

To measure the extent of HIV resistance to (-)-2',3'-dideoxy-3'-thiacytidine (3TC, lamivudine) within the context of monotherapy and to assess the presence of the M184V substitution in the case of 3TC-resistant viruses. Whether the success of 3TC in clinical trials could be due, in part, to an increase in the fidelity of HIV reverse transcriptase conferred by the M184V substitution was also considered.

METHODS

Two separate monotherapy studies were evaluated, one involving adults with CD4 counts > or = 300 x 10(6)/l, and the second involving children, some of whom had received antiretroviral treatment previously, while others were drug naive. Peripheral blood and plasma samples were collected regularly, and HIV isolation and determinations of drug median inhibitory concentration values were performed using umbilical cord mononuclear cells as targets. Amplification of the 184 mutation was performed by the polymerase chain reaction, using specific primer pairs. Fidelity determinations using purified, recombinant HIV reverse transcriptase derived from either wild-type virus or viruses that contained the 184V substitution were performed.

RESULTS

Phenotypic resistance was detected in almost all subjects at times ranging from 8-20 weeks after initiation of therapy. The 184V substitution was usually detected prior to the occurrence of phenotypic resistance to 3TC. Fidelity determinations revealed that the 184V substitution conferred an approximately 5- to 10-fold increase in HIV reverse transcriptase fidelity. In addition, titres of patient sera tested for their ability to neutralize autologous sequential viral isolates were stabilized in patients receiving 3TC therapy as opposed to other drugs.

CONCLUSIONS

Resistance to 3TC developed in virtually all subjects treated with this drug, and was associated with the appearance of an M184V mutation in HIV reverse transcriptase. The clinical benefit of 3TC therapy may be attributable in part to selection of viruses that are less able to replicate and mutate than the wild types.

Advances in antiretroviral therapy and viral load monitoring

OBJECTIVE

To highlight recent developments in the field of antiretroviral therapy and viral load monitoring.

METHODS

Review of studies detailing the efficacy of the antiretroviral agents and combinations furthest along in clinical development and the application of plasma HIV RNA quantification as a disease marker.

RESULTS

Developments in the field of antiretroviral therapy have led to substantial advances in the approach to management of HIV-infected persons. These include the end of the zidovudine (ZDV) monotherapy era; the demonstration of a survival benefit conferred by antiretroviral therapy in patients with CD4 counts of 200-500x10(6)/l; the further development of newer nucleoside analog combinations (e.g., ZDV-lamivudine, stavudine-didanosine, stavudine-lamivudine, ZDV-1592U89) and the non-nucleoside reverse transcriptase inhibitor class of compounds; and, perhaps most importantly, the advent of the protease inhibitor era. Trials of ritonavir and saquinavir have proven that clinical benefit can be conferred by protease inhibitors, and three-drug combination regimens, such as indinavir-ZDV-lamivudine, have shown the potential for degrees of viral suppression not previously seen. Newer protease inhibitors, such as nelfinavir and VX-478/GW141W94, hold promise for further advances. The concurrent development of assays to quantitatively measure plasma HIV RNA has provided laboratory tools to improve our understanding of disease pathogenesis, to assess the in vivo potency of treatment regimens and to characterize the risk of disease progression.

CONCLUSIONS

Recent progress in HIV disease pathogenesis, antiretroviral therapy and viral load monitoring indicates the interdependence of these factors. The current optimism in the field is warranted but complex challenges must be met if the fulfilment of this hope is to be realized by the world community.

The role of immunologic and viral markers in predicting clinical outcome in HIV infection

OBJECTIVE

In an ideal world, one clinical marker would explain all the variance in a disease system. In reality, however, this is rarely the case and HIV disease is no exception. This review considers several specific markers that have demonstrated some use in clinical trials and/or epidemiologic studies of antiretroviral therapy.

DISCUSSION

CD4 lymphocyte count, HIV viral load and perhaps immune activation markers can be used to measure the activity of antiretroviral therapy. Some recent studies are presented and the results discussed.

CONCLUSION

Sustained improvements in several markers (particularly HIV viral load and CD4 cell count) in combination appear to be the most predictive of clinical benefit. No current viral or immunologic markers adequately reflect toxicities attributable to antiretroviral therapy. Lamivudine/zidovudine combination therapy leads to sustained changes in several markers, and appears to be well tolerated. This may translate into significant clinical benefit but the duration of such benefit remains unknown.

CD8+ lymphocyte responses to antiretroviral therapy of HIV infection

CD8+ T lymphocytes may mediate important host responses to human immunodeficiency virus (HIV) infection by human leukocyte antigen (HLA)-restricted cytotoxicity and production of soluble HIV suppressor factors. CD8+ lymphocytes are also important for the suppression of many latent pathogens responsible for opportunistic disease in HIV-infected patients. There has been no systematic analysis of the responses of CD8+ lymphocyte counts to antiretroviral therapy. We compared CD8+ lymphocyte responses in seven trials of nucleoside or non-nucleoside analog reverse transcriptase inhibitors and in two trials of ritonavir, a HIV protease inhibitor. Nucleoside analog and non-nucleoside analog reverse transcriptase inhibitor monotherapy resulted in no substantial changes in CD8+ counts relative to baseline or placebo. Combination nucleoside analog therapy resulted in variable peak responses (-145 to +240 cells/mm3), which remained significantly above baseline for 0 to 12 weeks. In contrast, ritonavir monotherapy caused a peak increase of 892 CD8+ cells/mm3, which remained significantly above baseline for 32 weeks. There was a significant correlation (Rs 0.61, p = 0.01) between the peak CD4+ cell and CD8+ responses to each therapy, but no significant correlation between the peak viral load responses and peak CD8+ cell responses. These findings suggest that the greater CD8+ response seen with ritonavir may be due to its specific inhibition of HIV protease and also that the CD8+ response is dependent on new CD4+ cell production. The CD8+ lymphocyte proliferation observed with protease inhibitor therapy could result in improved suppression of HIV replication by the immune system and should be confirmed in a prospective trial comparing protease inhibitors with both nucleoside and non-nucleoside analog therapies.

The effect of influenza vaccination on human immunodeficiency virus type 1 load: a randomized, double-blind, placebo-controlled study

To determine if vaccination induces replication of human immunodeficiency virus type 1 (HIV-1), 42 HIV-1-infected subjects with CD4 cell counts of 200-500 cells/microL were randomized to receive influenza vaccine or saline placebo. Infectious cell-associated and plasma HIV-1 RNA virus load were measured twice at baseline and then at 7, 10, 14, and 30 days after injection by quantitative microculture and branched DNA amplification. The ratios of the geometric mean plasma HIV-1 load of the four follow-up visits compared with baseline in vaccine (n = 28) and placebo (n = 14) recipients were similar (1.05 [95% confidence interval, 0.80-1.37] for vaccine; 0.96 [95% confidence interval, 0.68-1.33] for placebo; P = .90). The geometric mean ratios of plasma virus load at each follow-up visit to baseline did not differ significantly from 1.0 for each group. Infectious cell-associated virus load measures yielded similar results. CD4 cell counts declined similarly in both groups at 6 months. Influenza vaccination did not increase HIV-1 load in this controlled clinical trial.

Comparison of three different hybridization assays in the quantitative measurement of serum hepatitis B virus DNA

The measurement of hepatitis B virus (HBV) DNA, is important for monitoring and evaluating the efficacy of anti-viral agents in the treatment of patients with chronic hepatitis B. Three different hybridization assays for quantitative measurement of HBV DNA: direct membrane (dot-blot) hybridization, liquid hybridization (Abbott HBV DNA assay) and branched DNA signal amplification assay (Quantiplex, Chiron), were applied to 114 serial serum samples obtained from 13 patients with chronic active hepatitis B who had received ribavirin 600 mg daily for four weeks. Among the three assays, the correlation was found to be highest between Quantiplex and Abbott HBV DNA assay (r = 0.71, p < 0.01), moderate between Quantiplex and dot-blot hybridization (r = 0.58, p < 0.01) and lowest between dot-blot hybridization and Abbott HBV DNA assay (r = 0.27, p < 0.01). Quantiplex detected 107 (94%) of 114 specimens and was the most sensitive assay. All specimens positive by dot-blot hybridization and Abbott HBV DNA assays were detected positive by Quantiplex. The Dot-blot hybridization assay detected all 89 (100%) specimens with a high HBV DNA level (> or = 10 million genome equivalent (Meq)/ml by Quantiplex), but detected only 7 (50%) of 14 specimens with a low HBV DNA level (< 10 Meq/ml). The Abbott HBV DNA assay detected 85 (95%) of 89 specimens with a high HBV DNA level, but detected only 3 (17%) of 18 specimens with a low HBV DNA level. Among 7 negative specimens in the Quantiplex assay, 2 were detected positive by polymerase chain reaction. In conclusion, Quantiplex assay was more sensitive than Abbott HBV DNA assay and dot-blot hybridization assay for quantitative measurement of serum HBV DNA and can be used in the evaluation of the therapeutic drug effect on chronic hepatitis B patients.

Combination therapies against HIV-1 infection: exploring the concept of combining antiretroviral drug treatments with HIV-1 immune-based therapies in asymptomatic individuals

The deleterious effect of HIV on the immune system begins at the time of infection. At seroconversion the virologic and immunologic factors that ultimately will dictate the rate of disease progression are believed to be already in place. The concept developed in this paper implies that, to impact significantly on the progression of disease, anti-HIV therapies should be initiated as early as possible in asymptomatic individuals. Published results have shown that combination drug therapies are potent in reducing HIV-1 RNA load in plasma in asymptomatic individuals, and that some HIV-1 immune-based therapies have a positive impact on immunological markers of disease progression, including HIV-1 cell-mediated immunity (CMI) and CD4 percent. The strategy discussed is to test a combination of antiretroviral therapy with HIV-1 immune-based therapy, such as the inactivated HIV-1 immunogen preparation, in asymptomatic individuals. The goal of this combination approach is to overcome the limitations of each therapy alone. Preliminary data suggest that antiretroviral therapy and the HIV-1 Immunogen can be combined with no noticeable interference and/or added toxicity in a broad range of HIV-1-infected individuals. Combining both therapies may enhance and expand the impact on key surrogate markers of disease progression, although they likely achieve this impact through different mechanisms. Thus, the primary question remains: Can these effects be synergistic?

Pediatric AIDS Clinical Trials Group Protocol 076 Study Group

BACKGROUND AND METHODS

A placebo-controlled trial has shown that treatment with zidovudine reduces the rate at which human immunodeficiency virus type 1 (HIV-1) is transmitted from mother to infant. We present data from that trial showing the number of infected infants at 18 months of age and the relation between the maternal viral load, the risk of HIV-1 transmission, and the efficacy of zidovudine treatment. Viral cultures were obtained, and HIV-1 RNA was measured by two assays in samples of maternal blood obtained at study entry and at delivery.

RESULTS

In 402 mother-infant pairs, the rate of transmission of HIV-1 was 7.6 percent (95 percent confidence interval, 4.3 to 12.3 percent) with zidovudine treatment and 22.6 percent (95 percent confidence interval, 17.0 to 29.0 percent) with placebo (P<0.001). In the placebo group, a large viral burden at entry or delivery or a positive culture was associated with an increased risk of transmission (the transmission rate was greater than 40 percent in the highest quartile of the RNA level). In both groups, transmission occurred at a wide range of maternal plasma HIV-1 RNA levels. Zidovudine reduced plasma RNA levels somewhat (median reduction, 0.24 log). Zidovudine was effective regardless of the HIV-1 RNA level or the CD4+ count at entry. In the zidovudine group, however, after we adjusted for the base-line HIV-1 RNA level and CD4+ count, the reduction in viral RNA from base line to delivery was not significantly associated with the risk of transmission of HIV-1.

CONCLUSIONS

A high maternal plasma concentration of virus is a risk factor for the transmission of HIV-1 from an untreated mother to her infant. The reduction in such transmission after zidovudine treatment is only partly explained by the reduction in plasma levels of viral RNA. To prevent HIV-1 transmission, initiating maternal treatment with zidovudine is recommended regardless of the plasma level of HIV-1 RNA or the CD4+ count.