Surrogate markers for survival in patients with AIDS and AIDS related complex treated with zidovudine

AIDS and COVID: A tale of two pandemics and the role of statisticians

The world has experienced three global pandemics over the last half-century: HIV/AIDS, H1N1, and COVID-19. HIV/AIDS and COVID-19 are still with us and have wrought extensive havoc worldwide. There are many differences between these two infections and their global impacts, but one thing they have in common is the mobilization of scientific resources to both understand the infection and develop ways to combat it. As was the case with HIV, statisticians have been in the forefront of scientists working to understand transmission dynamics and the natural history of infection, determine prognostic factors for severe disease, and develop optimal study designs to assess therapeutics and vaccines.

Mycobacterium avium Complex Disease

Despite the ubiqitous nature of Mycobacterium avium complex (MAC) organisms in the environment, relatively few of those who are infected develop disease. Thus, some degree of susceptibility due to either underlying lung disease or immunosuppression is required. The frequency of pulmonary MAC disease is increasing in many areas, and the exact reasons are unknown. Isolation of MAC from a respiratory specimen does not necessarily mean that treatment is required, as the decision to treatment requires the synthesis of clinical, radiographic, and microbiologic information as well as a weighing of the risks and benefits for the individual patient. Successful treatment requires a multipronged approach that includes antibiotics, aggressive pulmonary hygiene, and sometimes resection of the diseased lung. A combination of azithromycin, rifampin, and ethambutol administered three times weekly is recommend for nodular bronchiectatic disease, whereas the same regimen may be used for cavitary disease but administered daily and often with inclusion of a parenteral aminoglycoside. Disseminated MAC (DMAC) is almost exclusively seen in patients with late-stage AIDS and can be treated with a macrolide in combination with ethambutol, with or without rifabutin: the most important intervention in this setting is to gain HIV control with the use of potent antiretroviral therapy. Treatment outcomes for many patients with MAC disease remain suboptimal, so new drugs and treatment regimens are greatly needed. Given the high rate of reinfection after cure, one of the greatest needs is a better understanding of where infection occurs and how this can be prevented.

A Brief Chronicle of CD4 as a Biomarker for HIV/AIDS: A Tribute to the Memory of John L. Fahey

Foundational cellular immunology research of the 1960s and 1970s, together with the advent of monoclonal antibodies and flow cytometry, provided the knowledge base and the technological capability that enabled the elucidation of the role of CD4 T cells in HIV infection. Research identifying the sources and magnitude of variation in CD4 measurements, standardized reagents and protocols, and the development of clinical flow cytometers all contributed to the feasibility of widespread CD4 testing. Cohort studies and clinical trials provided the context for establishing the utility of CD4 for prognosis in HIV-infected persons, initial assessment of in vivo antiretroviral drug activity, and as a surrogate marker for clinical outcome in antiretroviral therapeutic trials. Even with sensitive HIV viral load measurement, CD4 cell counting is still utilized in determining antiretroviral therapy eligibility and time to initiate therapy. New point of care technologies are helping both to lower the cost of CD4 testing and enable its use in HIV test and treat programs around the world.

Serum Neopterin, an Immune Activation Marker, Independently Predicts Disease Progression in Advanced HIV-1 Infection

BACKGROUND

CD4+ T lymphocyte (CD4) counts and plasma human immunodeficiency virus (HIV) type 1 RNA concentrations predict clinical outcome in HIV-1 infection. Our objective was to assess the independent prognostic value for disease progression of soluble markers of immune system activation.

METHODS

This retrospective marker-validation study utilized previously obtained clinical and laboratory data, including CD4+ cell counts, and made use of stored frozen serum samples to assay for levels of beta2-microglobulin, neopterin, endogenous interferon, triglycerides, interleukin-6, soluble tumor necrosis factor- alpha receptor II, and HIV-1 RNA, and to determine HIV genotypic reverse-transcriptase inhibitor resistance. The 152 patients who participated in this study represented a subsample of participants in AIDS Clinical Trials Group (ACTG) 116B/117, a randomized trial that demonstrated the clinical benefit of didanosine over zidovudine monotherapy in persons with advanced HIV-1 infection. Marker data were analyzed in relation to protocol-defined clinical disease progression, using Cox proportional hazards models.

RESULTS

The median duration of follow-up was 344 days. Elevated baseline values for neopterin (P=.0009), endogenous interferon (P=.00039) and interleukin-6 (P=.0007) were each associated with greater subsequent risk of clinical disease progression. In a head-to-head comparison that was adjusted for CD4+ cell count (P=.0165) and HIV-1 RNA level (P=.1220), we found that elevated values for neopterin (P=.0002) and, to a lesser extent, endogenous interferon (P=.0053) were the strongest predictors of increased risk of clinical disease progression 6 months later.

CONCLUSIONS

Soluble markers of immune activation add prognostic information to CD4 counts and viral load for risk of disease progression in advanced HIV-1 infection. The robust performance of neopterin, an inexpensive and reliably measured serum marker, supports its potential suitability for patient monitoring, particularly in resource-limited settings.

Clinical and immunologic progression in HIV-infected US women before and after the introduction of highly active antiretroviral therapy

OBJECTIVE

To examine factors associated with clinical and immunologic HIV disease progression in a cohort of US women.

DESIGN

Analysis of data from a prospective, longitudinal, case-control study of HIV-infected women followed every 6 months for 7 years.

SETTING

Four urban clinical centers in the United States.

PARTICIPANTS

648 HIV-infected women who did not have AIDS at time of entry into the study.

MEASUREMENTS

Structured clinical and behavioral interviews; protocol-directed physical examinations; CD4 lymphocyte counts; plasma HIV RNA; infectious pathogen serologies. RESULTS With 2304 women-years of follow-up, 46.1% of the women developed AIDS; however, 93.3% of the diagnoses were based on CD4 counts dropping to <200 cells/mm(3). Only 10.6% of the women with CD4 counts <200 cells/mm(3) developed an opportunistic infection. Baseline CD4 count was the strongest predictor of subsequent clinical progression. Illicit substance use, multiple pregnancies, demographic variables, and other infections were not associated with progression. Among women with CD4 counts >500 cells/mm(3) at baseline, those who were anemic or had hepatitis C were more likely to progress to AIDS. By the end of the study, only 52% of the participants were on highly active antiretroviral therapy (HAART).

CONCLUSIONS

Despite underutilization of HAART in this multicenter cohort of urban women, opportunistic infections were uncommon, despite CD4 declines.

Statistical challenges in the evaluation of surrogate endpoints in randomized trials

The validation of surrogate endpoints has been studied by Prentice, who presented a definition as well as a set of criteria that are equivalent if the surrogate and true endpoints are binary. Freedman et al. supplemented these criteria with the so-called proportion explained. Buyse and Molenberghs proposed to replace the proportion explained by two quantities: (1). the relative effect, linking the effect of treatment on both endpoints, and (2). the adjusted association, an individual-level measure of agreement between both endpoints. In a multiunit setting, these quantities can be generalized to a trial-level measure of surrogacy and an individual-level measure of surrogacy. In this paper, we argue that such a multiunit approach should be adopted because it overcomes difficulties that necessarily surround validation efforts based on a single trial. These difficulties are highlighted.

Management of Kaposi sarcoma: the role of interferon and thalidomide

Kaposi sarcoma (KS) remains the most commonly diagnosed cancer in HIV-infected patients. Although several chemotherapeutic agents have proven effective in controlling KS, the growing understanding of the factors contributing to the development of KS has provided a stronger rationale for using noncytotoxic agents that influence the mechanisms involved in KS pathogenesis. Two such agents, interferon and thalidomide, have shown activity against KS in clinical trials and have the potential to influence multiple steps believed to be important in KS development and progression. Studies are ongoing to explore the optimal way to use these agents and their mechanisms of action.

Neural networks in the assessment of HIV immunopathology

Surrogate markers are by definition quantifiable laboratory variables that have clinical and biological relevance to disease outcomes. Virologic and immunologic surrogate markers have proven useful in following HIV-associated viral burden, immune dysregulation, dysfunction and deficiency. Monitoring of sequential changes in these markers and their interrelationships may provide significant information about viral-host-drug dynamics. The complexity and fluidity of these changes necessitates that an efficient means be developed for their monitoring. We therefore generated a neural network-based model for assessing host dynamics over time and compared its performance with that of a multiple regression model. Both modeling approaches were applied to the actual, non-filtered, clinical observations on 58 HIV-infected individuals treated consistently with Highly Active Anti-Retroviral Therapy (HAART), for a period of over-52 weeks resulting in an average of 16 observations per patient throughout this time span. Results demonstrated that the neural network was at least as accurate as a multi-regression model. Since our dataset was modest in size we also believe that neural networks warrant further consideration for modeling the complexity of HIV-host dynamics on larger datasets.

Proposed CD4(+) T-cell criteria for staging human immunodeficiency virus-infected Chinese adults

The present treatment, prophylaxis, and prognostic staging of human immunodeficiency virus (HIV) disease rely heavily on peripheral CD4(+) T lymphocyte (CD4) changes. We correlated the clinical course of events and CD4 changes among consecutive HIV-infected ethnic Chinese adults in Hong Kong. Using death as end point, the estimated proportion survival and death incidences were used to compare CDC and proposed staging criteria based on stratified baseline CD4. A separate set of baseline CD4 per microliter (/microl) (percentage lymphocytes) stratification criteria of 1, >220/microl (>12%); 2, 100-220/microl (6-12%); and 3, <100/microl, (<6%) is proposed which can be used for staging HIV-infected Chinese adults. For our study population, our proposed criteria for stratifying baseline CD4 gave better discrimination and more predictive power than the CDC criteria. We assessed the potential impact of these new proposed criteria on anti-retroviral treatment and prophylaxis against opportunistic infections in our adult HIV-infected population.

Increase in dendritic cell numbers, their function and the proportion uninfected during AZT therapy

The effects of AZT treatment on the numbers, level of infection and function of peripheral blood dendritic cells (DC) were examined in patients with HIV infection. This was a cross-sectional study of patients before AZT treatment and up to 20 months after initiation of treatment. Numbers of DC separated by density gradients were below the normal range in patients before treatment, but increased between 3 and 12 months of treatment. The numbers of DC per provirus copy rose from around 100 cells to 5000 cells and this decrease in viral load in DC was significant between 3 and 20 months of treatment. The capacity of DC to stimulate allogeneic T cell proliferation was low before treatment and significantly higher between 6 and 12 months after the start of AZT. This study indicated that AZT treatment produced beneficial effects on DC by increasing their numbers, reducing the provirus load and increasing their function in stimulating T cells. These results support the thesis that the function of these potent antigen-presenting cells is important in development of immunological defects in AIDS, and that effects of AZT treatment on DC may provide a measure of its therapeutic effect.

Transforming laboratory test results to improve clinical outcome predictions in HIV patients. Swiss HIV Cohort Study

Transforming natural units of laboratory markers of HIV disease may improve their ability to predict clinical outcomes. The authors examined this issue within a prospective study of 394 patients enrolled in the Swiss HIV Cohort Study (SHCS) between 1991 and 1993. Baseline predictors included CD4+ and CD8+ cell counts, HIV RNA levels, beta2-microglobulin, and age. Outcomes were death and clinical progression. A range of power transformations was applied to each predictor, and the goodness-of-fit of the corresponding proportional hazards models was assessed. The prognostic value of all laboratory variables could be improved on by power transformations. To predict either outcome variable, the "best" transformation of HIV RNA copies and CD8+ cell counts was the logarithm; for beta2-microglobulin, it was power -2. For CD4+ cell counts, the best transformation depended on the outcome variable: it was power 0.2 when predicting survival, and power 0.4 when predicting clinical progression. The single best predictor variable was the ratio of HIV RNA copies per CD4+ cell, for both death (logarithmic transformation) and clinical progression (power -0.1 transformation). Natural units of laboratory variables are not optimal for the prediction of clinical events in HIV-infected patients. Which transformation is best depends on the predictor under consideration.

Influence of age on rates of new AIDS-defining diseases and survival in 6546 AIDS patients

It has consistently been reported that older AIDS patients have a shortened survival compared with younger patients. The aim of the present study was to investigate whether this difference in survival is caused by differences in the pattern of the complicating diseases. Information on patient follow-up after the AIDS diagnosis was obtained by retrospective case note review. The 6,546 patients were followed from the time of AIDS diagnosis as part of the multicentre AIDS in Europe study, which examined AIDS cases diagnosed at 52 centres in 17 European countries between 1979 and 1989. Occurrence of AIDS-defining events and demographic variables were recorded for all patients, and CD4 lymphocyte count at the time of AIDS diagnosis for approximately half the patients. After adjusting for imbalances in other variables, persons > or = 50 years of age had a significantly higher risk of contracting AIDS wasting syndrome, AIDS dementia complex and oesophageal candidiasis after the initial AIDS diagnosis, compared with age group 30-39 years [relative risk (RR) 95% confidence interval (CI)], 3.23 (2.70-3.75 CI); 2.48 (2.16-2.80 CI); 1.55 (1.26-1.83 CI), respectively]. Shortened survival after the time of AIDS diagnosis was associated with older age. After adjusting for pattern of complicating diseases, the age effect remained unchanged. Older age predisposes to AIDS-related wasting syndrome, AIDS dementia complex and oesophageal candidiasis. Independent of these differences, older age is significantly associated with shortened survival, suggesting that factors such as severity of complicating diseases or the capability of handling serious infections, rather than disease pattern, are responsible for the shortened survival.

Markers, cofactors and staging systems in the study of HIV disease progression: a review

This paper is aimed at providing a comprehensive review of markers, cofactors and staging systems used for HIV disease, focusing on some aspects that nowadays could even be considered historical, and advancing in current issues such as the prognostic value of viral load measurements, viral genotypic and phenotypic characterization, and new HIV disease treatment protocols. CD4+ cell values, combined with the new viral markers mentioned are promising as a parsimonious predictor set for defining both severity and progression. An adequate predictor of patient resource use for planning purposes still needs to be defined.

CD4+ T-lymphocyte counts in HIV infection: are European standards applicable to African patients?

CD4+ lymphocyte count (CD4+ LC) is a widely used marker of Human Immunodeficiency Virus (HIV) immune impairment. Physiological lymphocytosis is frequently encountered in Africans. Therefore, we tried to determine if given CD4+ LC levels are of similar significance in European versus African HIV-infected individuals. Lymphocyte phenotyping of 750 HIV-infected adults was retrospectively analyzed. Three hundred and seventy patients were consecutively selected in Paris, France; 185 in Abidjan, Côte d'Ivoire; and 195 in Bobo-Dioulasso, Burkina Faso. In the three settings, lymphocyte phenotyping was performed by flow cytometry using similar protocols. Data from Abidjan and Bobo-Dioulasso were combined on the basis of geographic proximity and contrasted with those from Paris. Geometric mean levels of Total Lymphocyte Count (TLC), CD4+ LC, CD8+ lymphocyte count (CD8+ LC), and CD4:CD8 ratio, adjusted for percentage of CD4+ T-cells (%CD4+), were compared between Africans and Europeans. For a given %CD4+, TLC and CD4+ LC but not CD8+ LC tended to be about one third higher in West African than in French adults (p < 0.0001). Approximate equivalencies of absolute CD4+ counts in French and West African HIV-infected adults suggest that where thresholds of 200 and 500 CD4+ cells/microliter are applied in Europe, it might be appropriate to apply a threshold of approximately 250 and 700 CD4+ cells/microliter in West Africa, respectively. Establishing indicators of progression of HIV infection with locally appropriate thresholds may represent important steps toward improvement of HIV disease management in Africa.

Role of neopterin and 7,8-dihydroneopterin in human immunodeficiency virus infection: marker for disease progression and pathogenic link

Human immunodeficiency virus (HIV) infection is associated with increased concentrations of neopterin derivatives, released in large quantities by human macrophages on stimulation with interferon-gamma (INF-gamma). Neopterin concentrations thus inversely correlate with absolute CD4+ T-cell numbers and strongly predict progression of disease from latency to AIDS. Investigations of hydrogen peroxide-induced chemiluminescence indicated a potential role of neopterin and 7,8-dihydroneopterin in oxygen free radical-mediated processes. Indeed, 7,8-dihydroneopterin is able to enhance tumor necrosis factor alpha (TNF-alpha)-induced apoptosis, accompanied by an increased production of reactive oxygen intermediates (ROIs). In line with this finding, the same combination appears to contribute to the upregulation of HIV replication due to activation of nuclear factor-kappa B (NF-kappa B), a central enhancer element of the HIV LTR promoter. Thus, besides the role of neopterin as sensitive indicator of disease activity in HIV infection, neopterin derivatives apparently are associated with the cascade of events that regulate the HIV production in infected individuals.

Predictive value for survival of soluble tumor necrosis factor receptors p55 and p75 during zidovudine-containing treatment in symptomatic human immunodeficiency virus type 1 infection

Previous studies of asymptomatic human immunodeficiency virus (HIV) infection have shown that serum levels of soluble tumor necrosis factor receptors (sTNFR) are good predictors of disease progression and clinical outcome during zidovudine (ZDV) therapy. The present study of symptomatic HIV infection was designed to evaluate whether sTNFR p55 and p75 at weeks 0 (pretreatment) and 24 and 48 are predictors of death < or = 3 years after the start of ZDV 1,000 mg alone or combined with low-dose interferon-alpha (ZDV 500 mg + IFN-alpha 3 MIU three times weekly). CD4+ T-cell numbers and serum neopterin were analyzed in a similar way. Forty previously untreated symptomatic HIV-infected persons with CD4+ T-cell numbers > or = 150 x 10(6)/L were included. At baseline, in the nonsurvivor group, mean age (42.1 vs. 34.4 years, p = 0.002) and neopterin (24.7 vs. 18.0 nmol/L, p = 0.02) were higher, whereas mean CD4+ T-cell counts (202 vs. 295 x 10(6)/L, p = 0.02) were lower than in the survivors. All analyses were adjusted for age. For the pretreatment marker values, a significant relative risk (RR) for death was noted only in the univariate analysis for sTNFR-p55 > 1.7 ng/ml [RR 3.1; 95% confidence interval (CI) 1.1-8.8; p = 0.04]. During therapy, CD4+ counts < 200 x 10(6)/L at week 24 and 48 and neopterin > 20 nmol/ml at week 48 were independent predictors of survival in the uni- and multivariate analysis. Marker values relative to baseline were not predictive. sTNFR-p55 and p75 were of little use as surrogate markers for clinical efficacy during ZDV-containing drug regimens in symptomatic HIV-infected patients with CD4+ counts 150 x 10(6)/L.

Immunological and virological markers of HIV-disease progression

This review, based upon scientific literature, evaluates a number of immunological and virological markers for their usefulness as prognostic indicators for progression of HIV disease. The most widely studied marker, the CD4 positive T lymphocyte count, is perhaps the best single indicator of stage of illness. Serum factors such as neopterin and beta-2 microglobulin, alone and in combination with CD4 cell counts, have been shown to have good predictive value. Measurement of viral burden by quantification of viral RNA levels in plasma and immune cells also holds promise for following disease progression. It is recommended that a combination of these factors be monitored in evaluating stage of illness and responses to therapy in HIV-infected persons.

Predictive markers of survival in HIV-seropositive and HIV-seronegative Tanzanian patients with extrapulmonary tuberculosis

SETTING

Prediction of survival in Tanzanian patients with extrapulmonary tuberculosis (TB).

OBJECTIVE

To evaluate the prognostic value of clinical and laboratory parameters on survival in human immunodeficiency virus (HIV) seropositive and HIV seronegative patients with extrapulmonary TB.

DESIGN

Over an 8-month period 192 consecutive patients with extrapulmonary TB, admitted to a major referral centre in Tanzania, were enrolled in the study. Their symptoms, signs and PPD skin test were noted. Their sera were tested for HIV and analyzed for beta-2-microglobulin content. Univariate risk factors for 12 months' survival after the start of anti-TB chemotherapy were entered into a stepwise Cox regression model. Survival probabilities were estimated according to the number of risk factors.

RESULTS

Of the 192 patients 126 (65%) were HIV-infected, and 29.7% had disseminated TB. Thirty-five patients, of whom 24 (68.6%) were HIV-positive, withdrew from the study immediately after hospital discharge. For survival analysis 157 patients remained. Within 12 months' follow-up after initiation of anti-TB therapy, the case fatality rate of the 102HHIV-infected patients was 22% and of the 55 HIV seronegative patients 2% (P < 0.001). In the HIV seropositive patients the following independent risk factors were significantly associated with a decreased probability of survival: peripheral lymphadenopathy (Hazard Rate Ratio (HRR) 5.2, 95% Confidence Interval [CI] 1. 7-16.2), a decreased activity score (bedridden > 50%/day (HRR 4.5, 95% CI 1.7-11.7), lymphopenia of < 1000/microL (HRR 4.4, 95% CI 1.7-11.8), and mycobacteraemia (HRR 4.0, 95% CI 1.2-13-.1). An anergic PPD skin test reaction proved to be another independent risk factor when the analysis was performed on 89 patients with available Mantoux test results. In the HIV seropositive patients, the 12 months' survival probabilities were 93%, 86%, 54% and 0% for presence of 0, 1, 2, and > 2 risk factors respectively.

CONCLUSION

Estimation of survival probabilities in patients with extrapulmonary TB may be possible without performing CD4 cell counts.

Immunological characteristics of HIV-infected children: relationship to age, CD4 counts, disease progression, and survival

We have evaluated immunologic markers of disease progression in 79 children perinatally infected with HIV. Laboratory testing included T lymphocyte subsets and lymphoproliferative responses (LPR) to mitogens (PHA, Con A, and PWM), antigens (Candida, Tetanus), and alloantigens (MLC). Patients were graded into grades I, II, and III based on results of CD4 counts, and into grades A, B, and C based on results of LPR, with grades I and grades A being normal, III and C being the lowest, and II and B falling in-between. CD4 counts, CD4/CD8 ratio, and lymphoproliferative responses were markedly decreased in a majority of children. Grade III CD4 counts were almost always associated with decreased LPR. A majority of the children with grade I CD4 numbers, however, also had abnormal lymphoproliferative responses. Results of laboratory testing were analyzed in relation to clinical disease progression and survival. The first AIDS defining illnesses (ADI), especially opportunistic infections (OI), was usually associated with Grade III/C results in immunologic assays. Survival was significantly decreased in children with grade III CD4 cell counts, and grade C LPR, and was poorest if these abnormalities developed within the first year of life. In this latter age group, if the CD4 counts fell to grade III, the risk for dying was at least five times greater than those children with higher CD4 counts (grades II and I); if the proliferative responses to PHA and MLC were in Grade C, the survival was 22 months. Severe immune defects in the first year of life in children with HIV infection, as assessed by CD4 counts and a battery of functional tests, predicted rapid disease progression.

Pharmacokinetic optimisation of antiretroviral therapy in patients with HIV infection

More than 7 years after the introduction of zidovudine for treatment of HIV infection, little use has been made of the pharmacokinetic properties of this or any of the subsequently approved antiretroviral agents to optimise therapy. This is partly because of the limits of technologies developed to measure clinically relevant forms and concentrations of these drugs, and partly because the clinical community has been slow to recognise the potential benefits of pharmacokinetic optimisation of nucleoside analogue therapy in any disease. Nonetheless, for some of these agents, progress in understanding the relationship between pharmacokinetics and pharmacodynamics has been made. With zidovudine, for example, even though plasma concentrations have little clinical utility, evidence suggests that concentrations of active phosphorylated forms of zidovudine inside target cells are related to disease progression and toxicity. Furthermore, a decreased ability to phosphorylate zidovudine might be a prerequisite for the emergence of zidovudine-resistant HIV strains. Measurements of phosphorylated zidovudine inside cells similarly suggest that 100 mg of oral zidovudine every 8 hours approximates the optimal initial dosage regimen in asymptomatic patients. Increased plasma didanosine concentrations have been associated with several measures of clinical improvement in patients, and may be associated with an increased risk of toxicity as well. For zalcitabine and stavudine, however, the picture is much less clear. Their pharmacokinetic and pharmacodynamic relationships have not been studied in patients. Furthermore, there is insufficient data on the effects of age, gender, race and concurrent underlying conditions on the pharmacokinetics of all of these agents. Mounting evidence suggests that monitoring of these compounds could lead to individually optimised intervention strategies. Given the marginal benefits of therapy with these agents, their proven toxic effects and the lack of proven alternatives, it is critical that the clinical community strive to make the most effective use of these agents in the treatment of their patients.

Increased level of activated gamma delta lymphocytes correlates with disease severity in HIV infection

The lymphocyte subset expressing the gamma delta T cell receptor is increased in several infectious diseases including HIV infection. In this study the expression on gamma delta lymphocytes of the T cell activation markers CD25, HLA-DR and CD38, as well as the two isoforms of CD45, namely CD45RA and CD45RO, was determined in the peripheral blood of 56 HIV-infected intravenous drug users and 34 HIV-seronegative blood donors by two-colour flow cytometry. The percentage of gamma delta lymphocytes expressing HLA-DR and CD38 was higher than those in HIV-seronegative controls (P < 0.001 and P < 0.0001, respectively). Furthermore the HLA-DR+gamma delta+ lymphocytes correlated inversely with CD4+ T lymphocyte absolute count (P < 0.02 for both). The levels of gamma delta lymphocytes expressing CD25, CD45RA and CD45RO were similar to those in HIV-seronegative controls. Activated gamma delta lymphocytes may play a role in the HIV disease process and could provide a useful marker for disease progression.

Dietary intake and counseling, weight maintenance, and the course of HIV infection

OBJECTIVE

To define relationships among dietary intake and counseling, weight maintenance, and the clinical course of patients infected with the human immunodeficiency virus (HIV).

DESIGN

A prospective cohort study in an HIV clinic in a county hospital.

SUBJECTS

HIV-infected patients (68 with and 40 without acquired immunodeficiency syndrome [AIDS]) who had a good performance status and no chronic diarrhea were assessed at entry to the study and after 6 months. The following assessments were made: energy and nutrient intake based on 7-day food records, anthropometric measurements, immunologic function as lymphocyte T-cell subpopulations (ratio of CD4 to CD8), and serum cholesterol level. Patients were monitored to determine clinical outcome.

INTERVENTION

All patients received standardized dietary counseling designed to address identified intake deficiencies and maintain body weight.

MAIN OUTCOME MEASURES

Changes in energy and nutrient intake, body weight, and clinical outcome (ie, time to AIDS-defining illness and overall survival time).

STATISTICAL ANALYSES PERFORMED

Group differences (HIV group vs AIDS group) were sought using chi 2 analyses and Student's t test. A multivariate regression model was used to determined the best predictors of clinical outcome.

RESULTS

At baseline, total energy intake (based on 30 kcal/kg usual body weight) was adequate in both HIV and AIDS patients (101 +/- 4% and 103 +/- 5% [mean +/- standard deviation] of need, respectively). Despite dietary counseling and continued maintenance of energy intake, body weight, serum cholesterol level, and CD4 level progressively decreased. Consequently, saturated fat intake was found to be inversely related (P < .01) to serum cholesterol level. Clinical outcome (after 3.5 years) was associated with baseline ratio of CD4 to CD8 (P < .001), weight (P < .01), and serum cholesterol level (P < .001). Multivariate analysis related ratio of CD4 to CD8 (P < .001) and weight maintenance (P < .001) to favorable outcome in the final model.

APPLICATIONS

Weight loss in patients with HIV infection is independently prognostic of clinical outcome, and development of hypocholesterolemia is not favorable for clinical outcome. Because weight loss progresses despite conventional dietary counseling to identify energy need, interventions earlier in the disease course should be considered along with increased target levels for energy intake.

Disparity in the percentage of CD4+ T lymphocytes and prognosis of HIV-infected intravenous drug users in Malaysia

The CD4+ T-lymphocyte absolute count (CD4ac), CD4+ T-lymphocyte percentage (CD4%) and total lymphocyte count (Løac) were assessed in HIV-seropositive intravenous drug users (IVDU) with reference to their correlation with the clinical categories A, B, and C as stipulated by the Centre of Disease Control and Prevention, USA (CDC) and with each other. It was found that while the CD4ac and Løac correlated with the clinical categories, CD4% did not. This may suggest that in our local setting, the CD4% may not necessarily be a suitable alternative marker to CD4ac as proposed by CDC. Furthermore, the CD4% of the normal subjects in this study was found to be relatively lower than the reported Caucasian levels. This may indicate that the use of the cut-off level of less than 14% as an AIDS-defining criteria may not be applicable for our HIV-seropositive IVDU. In addition, unlike the CD4ac which correlated directly with CD4% and Løac, the CD4% did not correlate with Løac. Therefore, due to the observed disparity with clinical status of patients and its possibly lower levels in our normal population, CD4% as a marker for staging HIV disease should be used with caution in our setting. Such findings may also have an impact on the use of established markers for the monitoring and classification of HIV-infected individuals in this region.

A phase II study of effect of addition of trichosanthin to zidovudine in patients with HIV disease and failing antiretroviral agents

Patients infected with HIV, including those with AIDS-related complex and AIDS, and failing treatment with antiretroviral agents such as zidovudine, have been evaluated following addition of trichosanthin to the antiretroviral agent regimen. This ribosomal inhibitory protein is specifically cytotoxic for HIV-infected macrophages and lymphocytes. Ninety-three patients were treated with trichosanthin, using a schedule of weekly, then monthly, intravenous injections of 1.2 mg of drug in combination with antiretroviral agents, usually zidovudine. Side effects included myalgias, fevers, mild elevation in liver function tests, and mild-moderate anaphylactic reactions, which respond well to therapy with steroids and/or benedryl. Reversible mental status changes were noted in two patients, both receiving concomitant therapy with ddI. Clinical responses to trichosanthin treatment were monitored primarily by changes in laboratory parameters, particularly levels of CD4+ T lymphocytes. In the total population evaluated for efficacy (85 patients) there was a significant increase in CD4+ cell levels after initiation of trichosanthin therapy. A second analysis performed on 72 patients measured the rate of change of CD4+ cells during therapy, using an "area under the curve" analysis. During therapy there was a median increase of 1.2 cells/mm3/month. In patients in the top 25th percentile, this increase was greater than 8.4 cells/mm3/month. In 59 of the 72 patients, responses could also be monitored by comparing the rate of loss of CD4+ cell levels on antiretroviral agents (zidovudine or ddI) alone, during the year prior to initiation of trichosanthin, to the rate of change when trichosanthin was added to the treatment regimen. During the period before trichosanthin treatment (311 +/- 11.7 days) the median loss of CD4+ cells was 6.91 cells/mm3/month. Addition of trichosanthin to the treatment regimen resulted in a median gain of 1.1 CD4+ cells/mm3/month.

Practical problems in fitting a proportional hazards model to data with updated measurements of the covariates

We review and discuss the practical problems encountered when analysing the effect on survival of covariates which are measured repeatedly over time. Specific issues arise over and above those met with the standard proportional hazards model and concern all stages of data preparation, data analysis and interpretation of the results. Data from a randomized clinical trial of patients with primary biliary cirrhosis, on whom several measurements were taken at regular intervals after entry, are presented as an illustration.

Markers predicting progression of human immunodeficiency virus-related disease

Human immunodeficiency virus (HIV) interacts with the immune system throughout the course of infection. For most of the disease process, HIV activates the immune system, and the degree of activation can be assessed by measuring serum levels of molecules such as beta 2-microglobulin and neopterin, as well as other serum and cell surface phenotype markers. The levels of some of these markers correlate with clinical progression of HIV disease, and these markers may be useful as surrogate markers for development of clinical AIDS. Because the likelihood and timing of development of clinical AIDS following seroconversion, for any particular individual, are not readily predictable, the use of nonclinical disease markers has become critically important to patient management. Surrogate markers of HIV infection are, by definition, measurable traits that correlate with disease progression. An ideal marker should identify patients at highest risk of disease progression, provide information on how long an individual has been infected, help in staging HIV disease, predict development of opportunistic infections associated with AIDS, monitor the therapeutic efficacy of immunomodulating or antiviral treatments, and the easily quantifiable, reliable, clinically available, and affordable. This review examines the current state of knowledge and the role of surrogate markers in the natural history and treatment of HIV infection. The clinical usefulness of each marker is assessed with respect to the criteria outlined for the ideal surrogate marker for HIV disease progression.

Management of antiretroviral drug therapy in human immunodeficiency virus infection

Nucleoside analog reverse transcriptase inhibitors, including zidovudine, didanosine, and zalcitabine, remain the cornerstone of therapy against human immunodeficiency virus (HIV) infection, the cause of AIDS. Although therapeutic regimens have been designed that are effective in slowing the progression of disease, therapy with these agents has not been optimized. Ultimately, therapy is destined to fail in most patients. Decisions regarding when to begin therapy and the course of action to take when failure of therapy occurs are largely in the hands of the patient's physician, and currently must be made without the support of conclusive clinical data. In addition to an understanding of the recommended dosing guidelines, proper management of AIDS therapy requires a fundamental knowledge of the disease process, the pharmacology and limitations of the agents employed against the virus, and close cooperation with the clinical laboratory. Therefore, this article reviews the pharmacology of the three drugs currently approved for treatment of HIV infection, and the current guidelines for their use. The article also reviews the clinical and laboratory management of these agents, including the use of surrogate markers and the potential for pharmacokinetic optimization of therapy.

Clinical pharmacokinetics of zidovudine: inter and intraindividual variability and relationship to long term efficacy and toxicity

The variability of the pharmacokinetics of zidovudine after its oral administration to 36 AIDS patients has been investigated by measuring the plasma and urine levels of zidovudine and its metabolite on Days 1 and 35 of continuous treatment. A two-phase absorption model was first defined from well-documented data in 12 subjects. The population characteristics of the kinetic parameters for both days were estimated by a nonparametric method. On Day 1, the mean (coefficient of variation) volume of distribution of zidovudine was 94.41 (90%), its mean half-life was 0.81 h (107%) and its mean oral clearance was 117 l.h-1 (57%) and on Day 35, these values were, respectively, 1121 (139%), 0.75 h (181%) and 295 l.h-1 (196%). The results confirm the large interindividual and intraindividual variation in zidovudine kinetics. The four covariates included in the population analysis (body weight, serum haemoglobin, creatinine and bilirubin) did not show clear relationship to the kinetic parameters. Thirty-four subjects were follow-up clinically for 99 days to 367 days after initiation of zidovudine therapy. The relationship between individual kinetic parameters (determined by Bayesian estimation), mean concentration profiles and outcome was studied through survival analysis. Long-term efficacy was defined as the prevention of opportunistic infections, which occurred in 13 patients. No clinical or kinetic variables, nor the individual zidovudine concentration profiles were found to predict the occurrence of an opportunistic infection. Toxicity was defined as a 20%-decrease in serum haemoglobin, which occurred in 13 patients. A significant relationship between mean daily concentration and toxicity was found, with an hazard of occurrence of toxicity 4.3-times larger when the mean steady stade concentration was 0.8 mg.l-1 than 0.6. The results indicate that zidovudine dosage should be individualised.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical pharmacology of zidovudine and other 2',3'-dideoxynucleoside analogues

Since the discovery of the acquired immunodeficiency syndrome (AIDS) in 1981, considerable progress has been made in the development of agents with anti-HIV activity. Zidovudine was one of the first 2'-3'-dideoxynucleosides to cause inhibition of human immunodeficiency virus (HIV) replication in vitro, by inhibiting the viral reverse transcriptase. Early trials showed that zidovudine results in clinical and immunological improvements and prolonged life in patients with AIDS or AIDS-related complex. However, haematological toxicity is the main drawback associated with zidovudine therapy. The initial recommended dose of zidovudine was 1500 mg per day, but recent studies have shown that dosages as low as 300 mg per day could be just as effective, without the severe haematological toxicity. Because zidovudine readily crosses the blood-brain barrier, it is used for the treatment of neurological diseases associated with HIV disease with some success. However, Kaposi's sarcoma does not respond to therapy with the drug. Apart from haematological toxicity, patients on long-term therapy with zidovudine may also develop resistance. Zidovudine use has also been associated with improvements in neurodevelopmental and growth velocity in HIV-infected children. The use of zidovudine as a prophylaxis has also been suggested, but the value of this is questionable. The combination of zidovudine with other agents, such as acyclovir and interferon, has a synergistic effect on the anti-HIV activity, with reduced drug toxicity. Other 2',3'-dideoxynucleoside analogues, such as dideoxycytidine (ddC) and dideoxyinosine (ddI) are effective anti-HIV agents and their use is also associated with both clinical and immunological improvements.(ABSTRACT TRUNCATED AT 250 WORDS)

Surrogate markers for assessing treatment response in HIV disease

OBJECTIVE

To provide an awareness of the issues surrounding the selection and utility of surrogate markers to evaluate treatment response for new antiretroviral therapies for HIV infection.

DATA SOURCES

A MEDLINE search of applicable articles published between 1987 to the present, including clinical trials, commentaries, and editorials, was performed.

DATA SYNTHESIS

Surrogate markers are proximal indicators that are predictive of rare or distant outcomes and can be used in clinical trials to decrease sample size and study duration. Characteristics of potential surrogate endpoints include relevance to disease state, face validity, ability to be detected in the majority of patients, and correlation between treatment-induced changes and terminal endpoints. Potential surrogate markers for assessing treatment response in HIV infection can be categorized as either virologic (p24 antigen, plasma viremia, proviral DNA) or immunologic (CD4+ lymphocytes, neopterin, beta 2-microglobulin, soluble interleukin-2 receptors, immunoglobulin A [IgA]). The CD4+ lymphocyte count and the p24 antigen have been evaluated in most of the clinical trials examining antiretroviral agents and have the greatest documentation supporting their use. Neopterin and beta 2-microglobulin are nonspecific markers, but may improve the predictive value of the CD4+ count when used in combination. Other markers (i.e., soluble interleukin-2 receptors, IgA) remain relatively unstudied at this point.

CONCLUSIONS

There is no current consensus regarding the selection of surrogate markers for HIV disease. On the basis of the present literature, the CD4+ lymphocyte count has the greatest endorsement: however, combination with several surrogate markers may prove to be useful in clinical trials. Studies are needed to verify the reliability of surrogate markers used alone and in combination to predict therapeutic response from antiretroviral therapy.

Zalcitabine

OBJECTIVE

To review the chemistry, intracellular metabolism, pharmacokinetics, and clinical trials of zalcitabine (2'3'-dideoxycytidine, ddC).

DATA SOURCES

English-language articles and conference procedings. The indexing terms used were zalcitabine, 2'3'-dideoxycytidine, and ddC.

STUDY SELECTION

In addition to the manufacturer's package insert, available Phase I and Phase I/II studies were reviewed.

DATA EXTRACTION

Clinical experience with ddC has been limited to uncontrolled studies and an expanded-access program. Efficacy was evaluated solely on surrogate markers of HIV disease: CD4+ lymphocyte counts and p24 antigen determinations. Clinical endpoints, such as disease progression and survival rates, must be provided to the Food and Drug Administration (FDA) for continued approval.

DATA SYNTHESIS

The FDA has approved use of ddC in combination with zidovudine (ZDV) as therapy of HIV infection for patients with CD4+ lymphocyte counts < or = 300 cells/mm3 who have experienced significant clinical or immunologic deterioration. Although ddC has the same mechanism of action as other nucleoside analogs, it is more potent on a molar basis. The drug is stable in gastric pH and has good bioavailability (approximately 70-90 percent), but is rapidly cleared from plasma (half life approximately 1-3 h). Intracellular concentrations of ddC triphosphate, the active form, are probably related to plasma concentrations, yet may persist in cells longer than the parent drug persists in plasma. When used as primary therapy in patients with CD4+ < or = 300 cells/mm3, ddC/ZDV increased CD4+ lymphocyte counts and reduced plasma p24 antigen concentrations. In comparison to ZDV monotherapy data taken from other studies, ddC/ZDV appeared to demonstrate a more pronounced and sustained increase in CD4+ cell counts; however, this observation cannot be confirmed until the results of ZDV-controlled comparisons are available. Overall, 17-31 percent of the patients receiving the currently recommended initial dosage of ddC experience peripheral neuropathy.

CONCLUSIONS

In combination with ZDV, ddC appears to augment the CD4+ cell response of ZDV monotherapy in the treatment of HIV infection for ZDV-naive patients, although controlled studies and rigorous statistical analyses are lacking at present. The efficacy of ddC/ZDV in patients who received prior treatment with ZDV monotherapy is unclear at the present.

Neopterin and human immunodeficiency virus infection

Neopterin concentrations increase in serum and urine within the first week of infection with HIV and remain increased throughout the infection. In particular, changes in neopterin concentration precede decreases in CD4 T cell numbers and the development of clinical disease, and they can be used to predict the later development of AIDS. The increased neopterin concentrations show that the immune system is activated in HIV infection and demonstrate the presence of an interaction between the virus and the immune system. The most important future use of neopterin measurements may be in fast evaluation of new drugs in HIV infection.

Quantitation of unintegrated HIV-1 DNA in asymptomatic patients in the presence or absence of antiretroviral therapy

The objective of this work was to determine the amount of unintegrated human immunodeficiency virus (HIV) DNA (HIV uDNA) in asymptomatic individuals in the presence or absence of antiretroviral therapy. Twenty-one healthy seropositive individuals with no history of any opportunistic infection or previous use of nucleoside antiretrovirals, and 9 similarly asymptomatic individuals who had initiated nucleoside antiretroviral therapy within the last 24 months were studied. All patients had CD4 lymphocyte counts above 400/microliters. All subjects administered antiretrovirals received 400-600 mg of zidovudine daily for 2-24 months. Two individuals additionally received 400 mg of dideoxyinosine (ddI) daily for 4 and 5 months. Patient peripheral blood mononuclear cells (PBMCs) were examined for integrated and unintegrated HIV DNA by a quantitative PCR assay. In addition, CD4 counts were measured, and free and immune complex dissociated p24 antigen was detected in plasma by ELISA. The mean percentage of HIV uDNA in asymptomatic individuals not on therapy was 59%, with 95% confidence limits from 50 to 69%. In contrast, patients on therapy had a mean of only 13% HIV uDNA, with confidence limits from 2 to 25% (p < 0.001). These findings indicate that a significant amount of HIV DNA in infected, healthy patients not on therapy is in the unintegrated form, and that the amount of HIV uDNA in asymptomatic patients on nucleoside therapy is much less. The amount of HIV uDNA in PBMCs deserves further study as a new marker of the efficacy of antiretroviral therapy.

Early markers of HIV infection and subclinical disease progression

Human immunodeficiency virus (HIV) infection in US Air Force personnel between 1985 and 1989 was examined through a mandatory serological survey, and through annual examination of infected patients. CD4+ cell counts were determined by flow cytometry; beta 2 microglobulin and neopterin were measured by immunoassay. During this period 933 cases were found, of which 161 were documented seroconversions, giving an incidence rate of 15.6/100,000 person-years. For patients with > 400 CD4 cells microliters-1, the rate of initial occurrence of opportunistic infection was 1 and 4% at 1 and 2 years, respectively. HIV-infected persons with < 400 CD4+ cells microliters-1, in contrast, had rates of 21% at 1 year and 36% at 2 years. In a cross-sectional study, beta 2 microglobulin concentration was shown to increase in both the serum and spinal fluid of patients infected with HIV as their blood CD4 numbers declined. Neopterin levels in serum and spinal fluid showed a similar trend, with significantly lower neopterin concentrations in the group that had > 1000 CD4+ T cells compared to the 0-600 CD4+ cell group. Longitudinal studies included correlation of HIV p24 antigen with CD4 counts over a 1 year period. The p24 antigen-positive group had a 21% decline in CD4+ T cells, while the antigen-negative group had a 14% decline. Specific helper T-cell subsets were also examined over a 6 month period. A significant decline was seen in the CD4+/CD29+, CD4+/CD45R+, and overall CD4+ subsets which was not seen in AZT-treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)

High dose L-carnitine improves immunologic and metabolic parameters in AIDS patients

Several reports indicate that systemic carnitine deficiency could occur in acquired immunodeficiency disease syndrome (AIDS), and that primary and secondary carnitine deficiency leads to critical metabolic dysfunctions. L-carnitine supplementation to peripheral blood mononuclear cells (PBMCs) of AIDS patients resulted in significant enhancement of the phytohemagglutinin (PHA)-driven proliferative response. High dose L-carnitine administration (6 gr per day for two weeks) to AIDS patients treated with zidovudine also led to increased PBMCs proliferation and reduced blood levels of triglycerides. In addition, a reduction of beta 2-microglobulin serum levels as well as circulating tumor necrosis factor (TNF)-alpha, mostly in patients exhibiting highly elevated levels, were found at the end of the treatment period. Our data suggest that in vivo L-carnitine could prove useful in ameliorating both the immune response and lipid metabolism in patients with AIDS, irrespective of initial serum carnitines levels. The mechanism(s) accounting for the observed results are currently not clear. Further studies are needed to confirm the hypothesis that L-carnitine affects the expression of HIV-induced cytokine.

Evaluation of a dual-color flow cytometry immunophenotyping panel in a multicenter quality assurance program

A basic immunophenotyping panel that employed dual-color combinations of fluorescein isothiocyanate (FITC) and phycoerythrin (PE) conjugated monoclonal antibodies (mAb; FITC-CD45/PE-CD14, FITC-IgG1/PE-IgG2, FITC-CD3/PE-CD8, FITC-CD3/PE-CD4, FITC-CD3/PE-CD16 + PE-CD56, and PE-CD19) was utilized in a quality assurance program to determine whether the 4 laboratories participating in a multicenter AIDS study obtained similar lymphocyte subset percentage values for T cells, B cells, NK cells, and CD4+ and CD8+ T cells. Over a 1 1/2 year period, 78 shared peripheral blood specimens were prepared and analyzed in each laboratory. The CD45bright CD14- percentage for each specimen was used to correct that individual's lymphocyte subset values. Interlaboratory coefficients of variation (CV) for the human immunodeficiency virus type I (HIV) seronegative (n = 38) and HIV-seropositive (n = 40) specimens using this panel were < 3% for total T cells; < 5% for CD4+ T cells and CD8+ T cells; < or = 17% for B and NK cells; and < 8% for CD4T/CD8T ratios. The 6-tube basic immunophenotyping panel has several notable features: a) for clinical studies, it permits comprehensive evaluation of an individual's major lymphocyte subsets, i.e., T, B, NK, and CD4+ and CD8+ T cells; b) for interlaboratory proficiency testing programs, it allows the detection of differences among laboratories in measurements of several functionally distinct cell populations; and c) for within-sample quality assurance, it provides several quality control checks, including the lymphosum, i.e., the sum of an individual's corrected T+B+NK values, a sum that was generally 100 +/- 5% on the HIV-seronegative specimens analyzed in this study.

The significance of activation markers on CD8 lymphocytes in human immunodeficiency syndrome: staging and prognostic value

The objective of this prospective cohort study was to evaluate the expression of activation markers on CD8 lymphocytes at various clinical stages of HIV infection and to determine the value of these markers in identifying patients likely to have rapidly progressive disease. One hundred and three HIV+ patients, divided into four disease stages, and 34 seronegative controls were evaluated at study entry using flow cytometric immunophenotyping. The HIV patients were followed clinically for disease progression during the following 2 years. CD8 cell numbers and percentage of lymphocytes are increased after HIV infection. Expression of the CD38, HLA-DR and CD57 markers on CD8 cells was significantly increased in asymptomatic HIV-infected patients when compared with controls, as was the CD8 cell population which did not coexpress Leu-8. These activation markers were observed to be further increased in patient groups with more clinically advanced infection. The percentage of CD38 on CD8 cells emerged not only as a discriminator of disease severity, but was a strong predictor of progression in asymptomatic, lymphadenopathy and ARC patients. Given the utility of activation markers on CD8 lymphocytes in staging disease and predicting clinical outcome, the measurement of these parameters should be considered in the monitoring and management of HIV patients.