Is the clinical course of HIV-1 changing? Cohort study

The contribution of viral genotype to plasma viral set-point in HIV infection

Disease progression in HIV-infected individuals varies greatly, and while the environmental and host factors influencing this variation have been widely investigated, the viral contribution to variation in set-point viral load, a predictor of disease progression, is less clear. Previous studies, using transmission-pairs and analysis of phylogenetic signal in small numbers of individuals, have produced a wide range of viral genetic effect estimates. Here we present a novel application of a population-scale method based in quantitative genetics to estimate the viral genetic effect on set-point viral load in the UK subtype B HIV-1 epidemic, based on a very large data set. Analyzing the initial viral load and associated pol sequence, both taken before anti-retroviral therapy, of 8,483 patients, we estimate the proportion of variance in viral load explained by viral genetic effects to be 5.7% (CI 2.8-8.6%). We also estimated the change in viral load over time due to selection on the virus and environmental effects to be a decline of 0.05 log10 copies/mL/year, in contrast to recent studies which suggested a reported small increase in viral load over the last 20 years might be due to evolutionary changes in the virus. Our results suggest that in the UK epidemic, subtype B has a small but significant viral genetic effect on viral load. By allowing the analysis of large sample sizes, we expect our approach to be applicable to the estimation of the genetic contribution to traits in many organisms.

Significant reductions in Gag-protease-mediated HIV-1 replication capacity during the course of the epidemic in Japan

Human immunodeficiency virus type 1 (HIV-1) evolves rapidly in response to host immune selection pressures. As a result, the functional properties of HIV-1 isolates from earlier in the epidemic may differ from those of isolates from later stages. However, few studies have investigated alterations in viral replication capacity (RC) over the epidemic. In the present study, we compare Gag-Protease-associated RC between early and late isolates in Japan (1994 to 2009). HIV-1 subtype B sequences from 156 antiretroviral-naïve Japanese with chronic asymptomatic infection were used to construct a chimeric NL4-3 strain encoding plasma-derived gag-protease. Viral replication capacity was examined by infecting a long terminal repeat-driven green fluorescent protein-reporter T cell line. We observed a reduction in the RC of chimeric NL4-3 over the epidemic, which remained significant after adjusting for the CD4(+) T cell count and plasma virus load. The same outcome was seen when limiting the analysis to a single large cluster of related sequences, indicating that our results are not due to shifts in the molecular epidemiology of the epidemic in Japan. Moreover, the change in RC was independent of genetic distance between patient-derived sequences and wild-type NL4-3, thus ruling out potential temporal bias due to genetic similarity between patient and historic viral backbone sequences. Collectively, these data indicate that Gag-Protease-associated HIV-1 replication capacity has decreased over the epidemic in Japan. Larger studies from multiple geographical regions will be required to confirm this phenomenon.

Evolution of the human immunodeficiency virus type 1 protease: effects on viral replication capacity and protease robustness

The rapid spread of human immunodeficiency virus type 1 (HIV-1) in humans has been accompanied by continuous extensive genetic diversification of the virus. The aim of this study was to investigate the impact of HIV-1 diversification on HIV-1 replication capacity (RC) and mutational robustness. Thirty-three HIV-1 protease sequences were amplified from three groups of viruses: two naïve sample groups isolated 15 years apart plus a third group of protease inhibitor-(PI) resistant samples. The amplified proteases were recombined with an HXB2 infectious clone and RC was determined in MT-4 cells. RC was also measured in these three groups after random mutagenesis in vitro using error-prone PCR. No significant RC differences were observed between recombinant viruses from either early or recent naïve isolates (P = 0.5729), even though the proteases from the recent isolates had significantly lower sequence conservation scores compared with a subtype B ancestral sequence (P<0.0001). Randomly mutated recombinant viruses from the three groups exhibited significantly lower RC values than the corresponding wild-type viruses (P<0.0001). There was no significant difference regarding viral infectivity reduction between viruses carrying randomly mutated naïve proteases from early or recent sample isolates (P = 0.8035). Interestingly, a significantly greater loss of RC was observed in the PI-resistant protease group (P = 0.0400). These results demonstrate that protease sequence diversification has not affected HIV-1 RC or protease robustness and indicate that proteases carrying PI resistance substitutions are less robust than naïve proteases.

Is the virulence of HIV changing? A meta-analysis of trends in prognostic markers of HIV disease progression and transmission

OBJECTIVE

The potential for changing HIV-1 virulence has significant implications for the AIDS epidemic, including changing HIV transmission rates, rapidity of disease progression, and timing of ART. Published data to date have provided conflicting results.

DESIGN

We conducted a meta-analysis of changes in baseline CD4(+) T-cell counts and set point plasma viral RNA load over time in order to establish whether summary trends are consistent with changing HIV-1 virulence.

METHODS

We searched PubMed for studies of trends in HIV-1 prognostic markers of disease progression and supplemented findings with publications referenced in epidemiological or virulence studies. We identified 12 studies of trends in baseline CD4(+) T-cell counts (21, 052 total individuals), and eight studies of trends in set point viral loads (10 ,785 total individuals), spanning the years 1984-2010. Using random-effects meta-analysis, we estimated summary effect sizes for trends in HIV-1 plasma viral loads and CD4(+) T-cell counts.

RESULTS

Baseline CD4(+) T-cell counts showed a summary trend of decreasing cell counts [effect = -4.93  cells/μl per year, 95% confidence interval (CI) -6.53 to -3.3]. Set point viral loads showed a summary trend of increasing plasma viral RNA loads (effect = 0.013  log(10)  copies/ml per year, 95% CI -0.001 to 0.03). The trend rates decelerated in recent years for both prognostic markers.

CONCLUSION

Our results are consistent with increased virulence of HIV-1 over the course of the epidemic. Extrapolating over the 30 years since the first description of AIDS, this represents a CD4(+) T cells loss of approximately 148  cells/μl and a gain of 0.39  log(10)  copies/ml of viral RNA measured during early infection. These effect sizes would predict increasing rates of disease progression, and need for ART as well as increasing transmission risk.

Phylogenetic approach reveals that virus genotype largely determines HIV set-point viral load

HIV virulence, i.e. the time of progression to AIDS, varies greatly among patients. As for other rapidly evolving pathogens of humans, it is difficult to know if this variance is controlled by the genotype of the host or that of the virus because the transmission chain is usually unknown. We apply the phylogenetic comparative approach (PCA) to estimate the heritability of a trait from one infection to the next, which indicates the control of the virus genotype over this trait. The idea is to use viral RNA sequences obtained from patients infected by HIV-1 subtype B to build a phylogeny, which approximately reflects the transmission chain. Heritability is measured statistically as the propensity for patients close in the phylogeny to exhibit similar infection trait values. The approach reveals that up to half of the variance in set-point viral load, a trait associated with virulence, can be heritable. Our estimate is significant and robust to noise in the phylogeny. We also check for the consistency of our approach by showing that a trait related to drug resistance is almost entirely heritable. Finally, we show the importance of taking into account the transmission chain when estimating correlations between infection traits. The fact that HIV virulence is, at least partially, heritable from one infection to the next has clinical and epidemiological implications. The difference between earlier studies and ours comes from the quality of our dataset and from the power of the PCA, which can be applied to large datasets and accounts for within-host evolution. The PCA opens new perspectives for approaches linking clinical data and evolutionary biology because it can be extended to study other traits or other infectious diseases.

Some untreated patients infected by HIV die within a couple of years, while others survive more than 25 years. To date, it is still unclear whether this variance in the virulence of the infection is due to the host or to the virus genotype. One of the main difficulties in answering this question is that, as for most human diseases, we tend not to know who infected whom. Here, we solve this problem by adopting a phylogenetic approach, which estimates the heritability of species traits on a phylogeny. In our case, species correspond to infected patients and the trait is an infection trait. The phylogeny is obtained from the HIV RNA sequences isolated in each patient. We find that more than half of the variance observed in the set-point viral load—a trait that predicts virulence—is heritable from one infection to the next. This implies that set-point viral load is strongly controlled by the virus genotype. This application of the phylogenetic comparative approach to infectious diseases yields major results for the deciphering of HIV pathogenesis. Future applications to other traits and/or other pathogens will help us to better understand rapidly evolving diseases of humans.

No evidence of a change in HIV-1 virulence since 1996 in France

OBJECTIVE

We investigated temporal trends in the CD4 cell count and in plasma HIV RNA and total HIV DNA levels measured at the time of primary HIV infection, as proxies for HIV-1 virulence, taking changes in patient characteristics into account.

DESIGN

We studied 903 patients enrolled during primary HIV infection in the French multicenter ANRS PRIMO cohort from 1996 to 2007.

METHODS

Associations between the year of primary HIV infection and the values of the three markers were tested with regression models. The year of primary HIV infection was first introduced as a restricted cubic splines function in a regression model in order to explore the shape of the associations, and then as a continuous/categorical variable. The following confounders were considered in multiple regression analysis: time since infection and age (introduced as restricted cubic spline functions), sex, place of birth (Africa vs. others), symptomatic primary HIV infection, smoking, and virus-related factors (subtype B vs. non-B, and drug resistance mutations).

RESULTS

Multivariate analysis showed no temporal trends in the CD4 cell count (square-root) or in HIV-1 RNA and DNA levels (log10) measured at the time of primary HIV infection. We observed the well described associations between the prognostic markers and the time since infection, sex, symptomatic primary HIV infection, and smoking.

CONCLUSION

The CD4 cell count and HIV RNA and DNA levels measured at the time of primary HIV-1 infection remained stable across 12 consecutive years (1996-2007) in the ANRS PRIMO cohort, suggesting no major change in virulence, after taking into account changes in patient characteristics.

Increasing clinical virulence in two decades of the Italian HIV epidemic

The recent origin and great evolutionary potential of HIV imply that the virulence of the virus might still be changing, which could greatly affect the future of the pandemic. However, previous studies of time trends of HIV virulence have yielded conflicting results. Here we used an established methodology to assess time trends in the severity (virulence) of untreated HIV infections in a large Italian cohort. We characterized clinical virulence by the decline slope of the CD4 count (n = 1423 patients) and the viral setpoint (n = 785 patients) in untreated patients with sufficient data points. We used linear regression models to detect correlations between the date of diagnosis (ranging 1984-2006) and the virulence markers, controlling for gender, exposure category, age, and CD4 count at entry. The decline slope of the CD4 count and the viral setpoint displayed highly significant correlation with the date of diagnosis pointing in the direction of increasing virulence. A detailed analysis of riskgroups revealed that the epidemics of intravenous drug users started with an apparently less virulent virus, but experienced the strongest trend towards steeper CD4 decline among the major exposure categories. While our study did not allow us to exclude the effect of potential time trends in host factors, our findings are consistent with the hypothesis of increasing HIV virulence. Importantly, the use of an established methodology allowed for a comparison with earlier results, which confirmed that genuine differences exist in the time trends of HIV virulence between different epidemics. We thus conclude that there is not a single global trend of HIV virulence, and results obtained in one epidemic cannot be extrapolated to others. Comparison of discordant patterns between riskgroups and epidemics hints at a converging trend, which might indicate that an optimal level of virulence might exist for the virus.

Is HIV becoming more virulent? Initial CD4 cell counts among HIV seroconverters during the course of the HIV epidemic: 1985-2007

BACKGROUND

Whether human immunodeficiency virus (HIV) seroconverters have been presenting with progressively lower CD4 cell counts over the course of the HIV epidemic is controversial. Additional data on whether HIV might have become more virulent on a population level (measured by post-seroconversion CD4 cell counts) may provide important insights regarding HIV pathogenesis.

METHODS

To determine whether post-seroconversion CD4 cell counts have changed over time, we evaluated 2174 HIV seroconverters as part of a large cohort study during the period 1985-2007. Participants were documented antiretroviral-naive HIV seroconverters who had a CD4 cell count measured within 6 months after receiving a diagnosis of HIV infection. Multiple linear regression models were used to assess trends in initial CD4 cell counts.

RESULTS

The mean initial CD4 cell count decreased during the study period from 632 cells/mm(3) in 1985-1990 to 553 cells/mm(3) in 1991-1995, 493 cells/mm(3) in 1996-2001, and 514 cells/mm(3) in 2002-2007. During those periods, the percentages of seroconverters with an initial CD4 cell count <350 cells/mm(3) were 12%, 21%, 26%, and 25%, respectively. In the multiple linear model, the mean decrease in CD4 cell count from 1985-1990 was 65 cells/mm(3) in 1991-1995 (P < .001)), 107 cells/mm(3) in 1996-2001 (P < .001), and 102 cells/mm(3) in 2002-2007 (P < .001). Similar trends occurred with regard to CD4 cell percentage and total lymphocyte count. Similar decreases in initial CD4 cell counts were observed among African American and white persons during the epidemic.

DISCUSSION

A significant decrease in initial CD4 cell counts among HIV seroconverters in the United States has occurred during the HIV epidemic. These data provide an important clinical correlate to suggestions that HIV may have adapted to the host, resulting in a more virulent infection.

Lack of evidence for changing virulence of HIV-1 in North America

Background

Several long-term cohort studies and in-vitro fitness assays have resulted in inconsistent reports on changes in HIV-1 virulence, including reports of decreasing, stable, and increasing virulence over the course of the AIDS pandemic. We tested the hypothesis of changing HIV-1 virulence by examining trends in prognostic clinical markers of disease progression from 1984 to 2005 among nearly 400 antiretroviral-naïve participants in the United States Multicenter AIDS Cohort Study (MACS), a longitudinal study of HIV infection in men who have sex with men (MSM).

Methodology/Principal Findings

Because clinical AIDS endpoints could not be used (due to antiretroviral therapies and prophylaxis), three prognostic markers of disease progression were used as proxies for HIV-1 virulence: plasma viral RNA load and CD4+ T cell count at “set point” (between ∼9 and ∼15 months after seroconversion), and rate of CD4 cell decline within three years after seroconversion. We performed multivariate analyses of the association between these markers and seroconversion year, with covariates including MACS site, race/ethnic group, seroconversion age, and CCR5Δ32 status. No statistically significant association was found between year of seroconversion and “set point” plasma viral load (at ∼9 months after seroconversion: slope = −0.004 log₁₀ copies/mL/year, p = 0.76; at ∼15 months: slope = −0.005 log₁₀ copies/mL/year, p = 0.71), CD4 cell count after seroconversion (at ∼9 months: slope = −0.112 cells/µL/year, p = 0.22; at ∼15 months: slope = −0.047 cells/µL/year, p = 0.64), or rate of CD4 cell decline over the first three years after seroconversion (slope = −0.010 cells/ul/yr², p = 0.88).

Conclusions/Significance

The lack of significant trends from 1984 to 2005 in these prognostic markers of HIV disease progression suggests no major change in HIV-1 virulence over the AIDS pandemic in MSM in the US.

Stable virulence levels in the HIV epidemic of Switzerland over two decades

OBJECTIVE

To determine whether the virulence of HIV-1 has been changing since its introduction into Switzerland.

DESIGN

A prospective cohort study of HIV-1 infected individuals with well-characterized pre-therapy disease history.

METHODS

To minimize the effect of recently imported viruses and ethnicity-associated host factors, the analysis was restricted to the white, north-west-European majority population of the cohort. Virulence was characterized by the decline slope of the CD4 cell count (n = 817 patients), the decline slope of the CD4:CD8 ratio (n = 815 patients) and the viral setpoint (n = 549 patients) in untreated patients with sufficient data points. Linear regression models were used to detect correlations between the date of diagnosis (ranging between 1984 and 2003) and the virulence markers, controlling for gender, exposure category, age and CD4 cell count at entry.

RESULTS

We found no correlation between any of the virulence markers and the date of diagnosis. Inspection of short-term trends confirmed that virulence has fluctuated around a stable level over time.

CONCLUSIONS

The lack of long-term time trends in the virulence markers indicates that HIV-1 is not evolving towards increasing or decreasing virulence at a perceptible rate. Both highly virulent and attenuated strains have apparently been unable to spread at the population level. This result suggests that either the evolution of virulence may be slow or inhibited due to evolutionary constraints, or HIV-1 may have already evolved to optimal virulence in the human host.

Differences in CD4 cell counts at seroconversion and decline among 5739 HIV-1-infected individuals with well-estimated dates of seroconversion

We studied repeated measurements of CD4 cell counts on 5739 HIV-1-infected individuals with reliably estimated dates of seroconversion (SC) aged > or =15 years at SC prior to initiation of highly active antiretroviral therapy (HAART) or AIDS using random effects models. Estimated CD4 cell count at SC differed significantly by sex, exposure group, and age, being higher in women, hemophilic men, and injection drug users (IDUs) as well as in those aged >40 years at SC. The rate of CD4 cell count decline did not differ significantly by sex; thus, differences between men and women were stable throughout the HIV-1 incubation period. There was a monotonic relationship between CD4 slopes and age at SC, with steeper slopes in older subjects. At 5 years after SC, the median difference in CD4 cell counts between the oldest (>40 years at SC) and youngest (16-20 years at SC) subjects was around 90 cells/microL. Mean rate of CD4 decline was significantly steeper in subjects diagnosed during acute infection. There was no evidence of a faster loss of CD4 cells in subjects who seroconverted after 1994. Apart from hemophilic men, who tended to have a steeper rate of CD4 decline on average, mean CD4 slopes did not differ by exposure category. These results suggest that before the initiation of HAART or other interventions based on immune status, consideration of demographic factors may be worthwhile.

The practical significance of potential biases in estimates of the AIDS incubation period distribution in the UK register of HIV seroconverters

OBJECTIVES

To assess the practical significance of the following sources of bias for estimates of the AIDS incubation period in a large seroconverter cohort: estimation of the time of seroconversion; presentation with an HIV-related illness; preferential inclusion of survivors; loss to follow-up and analysis cut-off date; the inclusion of Kaposi's sarcoma as an AIDS event; death without an AIDS diagnosis; and representativeness of the HIV population.

METHODS

Standard non-parametric survival methods were used to estimate the AIDS incubation period distribution. The practical importance of each type of bias was assessed using various sensitivity analyses.

RESULTS

The potential sources of bias of most practical importance in this study were the right-censoring strategy and that due to lack of documentation of a negative HIV antibody test. Five different right-censoring strategies gave estimates of the median time to AIDS ranging from 8.1 to 10.8 years for the 1202 individuals enrolled in the UK Register of HIV Seroconverters. HIV-infected persons with a history of a previous antibody negative test which could not be verified appeared to progress to AIDS more rapidly than persons with such verification (Relative risk = 1.8, 95% confidence intervals = 1.3-2.3).

CONCLUSIONS

As a number of possible causes of bias can impact on results, care must be taken to document them and control for them wherever possible. In our study, this was particularly relevant in relation to the documentation of a previous HIV antibody negative test and the choice of analysis cut-off dates. As methods may differ between cohorts, comparison of the published results from one cohort with those of another may be misleading.

Is the AIDS incubation time changing? A back-calculation approach

Contradictory literature was recently published on possible changes in AIDS incubation time over the period 1978-1994. The purpose of this work was to test if a change in incubation time (shortening or lengthening) was observed in France, either globally or in specific transmission groups (homosexual-bisexual men, heterosexual subjects), using a back-calculation approach. An age dependent TSI model (time since infection), which took into account a temporary treatment effect and allowed us to test for a change in the incubation time, was applied to the French AIDS cases (Réseau National de Santé Publique). The EM algorithm was used to maximize the likelihood and the best model was selected on the basis of the likelihood ratio statistic. The analysis on all AIDS cases indicated a shortening of the AIDS incubation time estimated to begin in 1983 (95 per cent CI 1982-1984). This shortening of incubation time was also apparent when analysis was restricted to homosexual-bisexual men and to heterosexual subjects. This shortening corresponded to a median incubation time of 9.6 years (95 per cent CI 8.1-10.5) for people infected at 30 years of age in 1983, versus 12.7 years for people infected at 30 years of age before the change.

Longitudinal analysis of serum chemokine levels in the course of HIV-1 infection

OBJECTIVES

To investigate the correlation between the serum levels of the CC-chemokines RANTES, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta, and the progression of HIV-1 disease.

DESIGN

Retrospective analysis of serial serum samples from HIV-1 seroconverters selected according to clinical outcome.

METHODS

Twenty-one patients, derived from a cohort recruited between 1985 and 1996 for a prospective study of the natural history of HIV infection, were analysed. All patients had at least one HIV-1-seronegative sample within 1 year prior to the first seropositive test and were followed longitudinally throughout the course of HIV-1 infection (mean follow-up, 73.5 months). Nine were rapid progressors (RP; patients who developed AIDS within 60 months of antibody seroconversion), seven were slow progressors (SP; patients who developed AIDS after 60 months), and five were long-term asymptomatic (LTA; patients with circulating CD4+ cells higher than 400 x 10(6)/l, no signs of HIV disease, no antiretroviral therapy for more than 96 months). A total of 339 serum samples was studied (mean, 16.1 per patient). The levels of RANTES, MIP-1alpha and MIP-1beta were measured by enzyme-linked immunosorbent assay and correlated with different immunological and clinical parameters.

RESULTS

Over the entire follow-up period, the geometric mean of serum RANTES was significantly higher in RP [68.6 ng/ml; 95% confidence interval (CI), 56.9-82.7] than in SP (23.7 ng/ml; 95% CI, 20.0-28.2; P < 0.001) and LTA (19.5 ng/ml; 95% CI, 15.5-24.5; P < 0.001). This difference was already significant during the early clinical stages, when patients had peripheral blood CD4+ cell counts still greater than 400 x 10(6)/l (P < 0.001). By contrast, the mean serum levels of MIP-1alpha and MIP-1beta did not differ significantly between the three study groups. Multivariate analysis using the Cox proportional hazard model demonstrated that the mean serum concentration of RANTES before the development of AIDS was independently associated with the time to AIDS (relative risk, 4.5; 95% CI, 1.1-18.2; P = 0.035). In patients with low versus high mean serum RANTES before the fall of CD4+ cells below 400 x 10(6)/l, the median AIDS-free time was 117.5 and 42.7 months, respectively (P = 0.037).

CONCLUSION

These data suggest that an elevation of serum RANTES predicts a rapid progression of the disease since the early stages of HIV-1 infection.

The impact of HIV on a fertility problems clinic

This article describes the impact of the human immuno-deficiency virus (HIV) on clinical infertility practice. HIV is responsible for acquired immuno-deficiency syndrome (AIDS) and first became apparent in 1979, but was not fully recognised by clinicians and scientists until 1981. It is a new disease which now infects large numbers of humans, and there is the possibility that the virulence of the virus may change or mutations may render current testing strategies ineffective. For these reasons, it is important to have a cautious and flexible approach to minimise risk to infertile couples and to future children.

Evaluating the effect of year of seroconversion on HIV progression in cohort studies. Italian Seroconversion Study

OBJECTIVES

To show how a spurious association between the calendar year of seroconversion and HIV progression arises as a result of censoring the follow-up of individuals at their last visit, when the individuals' visits are intermittent.

DESIGN

A notional cohort of 1140 seroconverters and a cohort study of 1270 HIV-infected individuals seroconverted between 1985 and 1994, and followed up to December 1995 (the Italian Seroconversion Study cohort).

METHODS

Failure times and rate of the patients attending the clinic over the study period were simulated for the notional cohort. Three separate scenarios with different probabilities of making a visit were considered. Standard survival analysis techniques were used to assess the effect of the year of seroconversion on HIV progression. The progression to a CD4 cell count of 200 x 10(6)/l according to the calendar year of seroconversion in the Italian Seroconversion Study was assessed using different censoring strategies.

RESULTS

A spurious effect of the year of seroconversion consistently appeared in 100 repeated simulations. When ignoring the visits occurring after the first year of follow-up in the Italian Seroconversion Study cohort, results supported the hypothesis of no effect of the year from seroconversion.

CONCLUSIONS

The choice of the censoring strategy is crucial when assessing the effect of year of seroconversion using survival analysis in cohort studies with intermittent visit structure. Different censoring strategies should be considered before firmly concluding that more virulent strains or the use of treatment are modifying the natural history of HIV disease from cohort studies of this nature.

Has the rate of progression to AIDS changed in recent years?

OBJECTIVES

To investigate whether the rate of progression to AIDS has changed over time by testing an effect of the year of seroconversion on AIDS onset (Centers for Disease Control and Prevention 1987 revised classification), next to an effect of the calendar period of follow-up.

DESIGN

French multicentre prospective study of 385 homosexual and heterosexual subjects and 231 subjects from a multicentre study of European injecting drug users (IDU), all with a documented date of HIV-1 seroconversion.

METHOD

The effect of the year of seroconversion was compared by the log-rank test. Crude and adjusted relative hazard (ARH) were quantified using the Cox model. Calendar period of follow-up was studied separately for sexual exposure group and IDU and treated as a time-dependent variable in a Cox model.

RESULTS

In the 616 study subjects the year of seroconversion was not significantly related to AIDS occurrence (n = 108); the ARH was 0.88 [95% confidence interval (CI), 0.56-1.38] for those who seroconverted in 1988-1989, and 1.17 (95% CI, 0.61-2.25) for those who seroconverted after 1989, compared with those who seroconverted before 1988. In the sexual exposure group, a clear trend towards less rapid progression to AIDS was observed in subjects followed in 1991-1992 (ARH, 0.49; 95% CI, 0.24-0.99) and after 1992 (ARH, 0.54; 95% CI; 0.24-1.21), compared with those followed before 1991. This favorable trend was not observed in IDU despite a significant decrease over time of Pneumocystis carinii pneumonia as AIDS-defining illness. Conversely to sexual exposure groups, the frequency of antiretroviral treatment (mainly zidovudine) prescription was still low during the most recent calendar periods in IDU when the CD4 count threshold of 200 x 10(6)/l was reached.

CONCLUSIONS

No evidence was found of a change in the rate of progression to AIDS in subjects who seroconverted in recent years. Furthermore, conversely to sexual exposure groups, the lack of favorable trends in IDU users followed in recent years suggest that health-care systems are not always adapted to their lifestyles.