The predictive value of changes in serologic and cell markers of HIV activity for subsequent clinical outcome in patients with asymptomatic HIV disease treated with zidovudine

Highly active antiretroviral therapy results in a decrease in CD8+ T cell activation and preferential reconstitution of the peripheral CD4+ T cell population with memory rather than naive cells

OBJECTIVE

Highly active antiretroviral therapy (HAART) can produce marked increases in peripheral blood CD4+ T cells and decreases in HIV plasma RNA copy numbers. However, it is not clear whether these absolute changes will be accompanied by a recovery in the known naive CD4+ T cell depletion or a decrease in the marked CD8+ T cell activation.

DESIGN

Twenty-nine patients were enrolled in studies of either nucleoside therapy alone or nucleoside therapy combined with a protease inhibitor (zidovudine + lamivudine + indinavir). One hundred and ninety-one examinations were carried out at three baseline time points and during 40 weeks of follow-up to evaluate the effect of HAART on CD4+ memory/naive phenotype and CD8+ T cell activation.

METHODS

CD4+ and CD8+ T cell number, CD62L/CD45RA expression on CD4+ T cells and CD38 expression on CD8+ T cells were measured by three-color flow cytometry.

RESULTS

Most protease inhibitor treated patients had a significant rise in CD4+ numbers. The marked rise in the CD4+ T cells seen in individuals in this study was not accompanied over a 40-week period by a change in the abnormally low CD4+ naive compartment, and thus was almost completely of memory phenotype. The CD38 expression on CD8+ cells fell during treatment, and decreased to a greater degree than the comparable rise in CD4+ T cell counts. This decrease continued in many patients after the CD4+ T cell rise or viral load decline had plateaued.

CONCLUSION

HAART results in changes in activation to a greater extent than absolute changes in CD4+ T cell numbers, but is not accompanied by an increase in naive CD4+ T cells. Measurements of CD4+ T cell numbers alone may not allow appropriate interpretation of immune activation or immune competence in patients receiving those drugs.

Human immunodeficiency virus infection, Part I

Initially recognized in 1982, acquired immunodeficiency syndrome (AIDS) has been the leading cause of death among young adults in the United States for much of this decade, and it has had a devastating impact on people in the developing world. It is estimated that 42 million people worldwide have been infected with human immunodeficiency virus (HIV), the virus that causes AIDS, and that almost 12 million people have died from AIDS-related diseases through 1997. Among these 12 million are 3 million children. Two thirds of the more than 30 million people with HIV or AIDS reside in sub-Saharan Africa. In the United States, 641,086 patients have been diagnosed with AIDS through 1997, and at least 385,000 have died. However, for the first time, new highly active antiretroviral therapies that include multiple drugs that attack the virus at several sites have slowed the progression from HIV to AIDS and from AIDS to death for those infected with HIV. The cumulative effect of these changes has been a reduction in both AIDS incident cases and AIDS deaths. Recent epidemiologic trends indicate that the proportion of AIDS incident cases and new HIV infections are increasing among women, African-Americans, and Hispanics, and the infections are more likely to be acquired through heterosexual transmission. The clinical management of HIV infection and AIDS has become increasingly complex in recent years. In addition to complete medical and social histories and physical examinations, hematologic, biochemical, serologic, and immunologic laboratory tests are required to predict the likelihood that patients will develop opportunistic infections and other complications related to HIV infection. Among the most important laboratory tests are measurements of HIV in plasma (viral load) in conjunction with peripheral blood CD4+ helper T lymphocyte counts. These tests are potent predictors of disease progression and their results have become markers for clinical response to therapy. The development of highly active antiretroviral therapy has had a profound impact on the epidemiology of AIDS and on the lives of individual patients. Through combinations of antiretroviral drugs, especially protease inhibitors, viral suppression can be achieved. However, adherence to these complex medical regimens and drug interactions have been problems for many patients. In addition, numerous questions remain unanswered, most importantly those regarding the timing of the initiation of treatment, the durability of viral suppression and clinical response, and the optimal "salvage" regimens for patients failing therapy either clinically or virologically.

Cellular proviral HIV type 1 DNA load persists after long-term RT-inhibitor therapy in HIV type 1 infected persons

In a set of 42 antiretroviral naive HIV-1 infected persons who were treated with either Zidovudine (AZT) monotherapy, or a combination of AZT + ddC (Zalcitabine) or AZT + ddI (Didanosine), the HIV-1 DNA load was measured by competitive polymerase chain reaction (PCR) and related to the HIV-1 RNA load in plasma, the CD4+ counts and to clinical markers. The question was whether a reduction in the cellular HIV-1 DNA level contributes to clinical benefit, as predicted by a lasting response in HIV-1 RNA levels in plasma. No significant decline relative to baseline in HIV-1 DNA load was found in the AZT monotherapy arm. In this arm the differences from baseline for both HIV-1 RNA load and CD4+ T cell counts were small and transient. In both combination therapy arms, the maximum mean decline in HIV-1 DNA load was 0.6 log and it never differed significantly from baseline. This is in contrast to plasma HIV-1 RNA load that declined earlier and steeper (mean of 1.5 and 1.9 log for AZT + ddC and AZT + ddI, respectively) and that remained significantly below baseline for 80 weeks. Although 9 of 42 (32%) of the patients under combination therapy had prolonged decreased plasma RNA levels, the proviral HIV-1 DNA remained present in the cells throughout the total follow-up of 144 weeks. In conclusion, combination therapy showed better laboratory parameter responses than AZT monotherapy, in agreement with the clinical data. The HIV-1 DNA sequences did not disappear in any of the patients, heralding renewed active infection after cessation of therapy.

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.

Evaluation of a newly developed HIV antigen test

A new monoclonal antibody-based enzyme immunoassay (Innogenetics) for the detection and quantification of p24 core antigens of HIV-1 (group M and group O) and of HIV-2 was evaluated on 2745 serum samples and 18 culture supernatants and compared with a reference (Coulter) HIV-1 p24 antigen assay. Positive results were confirmed by neutralization with the reagents of the respective tests. As demonstrated by dilution series of HIV cocultures, the new test recognizes p24 antigen of the most common HIV genetic subtypes, including group O and HIV-2. Titres ranged from 729 to 531441. Therefore p24 antigen assay is but very weakly reactive with HIV-2 (titres from 9 to 81). The new test is considerably more sensitive than the reference. In a population of 365 follow-up samples from 86 different patients, representing all stages of infection, the new test detected p24 antigen at least once in 52% (45/86) of these patients, whereas the reference was positive in 31% (27/86). The newly designed test detected antigen in 40% (145/365) of the samples, while the reference was positive in 21% (75/365). In a group of PCR and/or culture positive neonates, 33% (9/27) of the samples were positive with the new test versus 18% (5/27) with the reference. The specificity of the new test, as determined on 2,000 blood donor samples, was 99.65% (initially), 99.80% (after repetition), and 100% (with neutralization). The reference scored 99.95%, 100%, and 100%, respectively. In 300 seronegative samples from persons at risk, the initial specificity of the new test was 98.67% (the reference, 99.00%). With neutralization, both assays were 100% specific.