Cells In HIV-infected Individuals Research Articles

Single cell analysis of IL-4 and IFN-gamma production by T cells from HIV-infected individuals: decreased IFN-gamma in the presence of preserved IL-4 production.

The specific in vitro disturbance of capacities ascribed to Th1 cells in HIV-infected individuals suggests a switch from Th1 to Th2 lymphokine secretion. Indeed, when T cell clones are generated from HIV-infected individuals compared with controls, an increased percentage of Th0 clones is present upon HIV infection. We studied cytokine production in the supernatant of in vitro activated PBMC from a large group of HIV-infected patients at various stages of infection. IL-2, IFN-gamma, IL-4, IL-5, and IL-10 production all were decreased significantly, which does not support a switch to Th2 lymphokine secretion and is possibly due to the generalized impaired response of T cells from HIV-infected individuals to activation signals in vitro. Therefore, we investigated the capacity of single cells to produce a certain cytokine. Intracellular staining of IL-4- and IFN-gamma-producing cells revealed that T cells from HIV-infected individuals contained decreased numbers of IFN-gamma-producing cells, in the presence of normal percentages of cells with the capacity to produce IL-4. This resulted in significantly decreased IFN-gamma/IL-4 ratios in both CD4+ and CD8+ T cells. Thus, in agreement with previous findings in T cell clones, we conclude, from cytokine production upon stimulation of T cells in vitro, that there is a change in the cytokine balance to the Th2 side in HIV infection due to decreased Th1 and preserved Th2 cytokine production.

Increased expression of CD80, CD86 and CD70 on T cells from HIV‐infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8+ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8+ T cells from HIV- individuals cultured in the absence of CD4+ T cells. Addition of CD4+ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4+ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8+ T cells. Thus, to some extent, CD8+ T cells in HIV-infected individuals appeared to be refractory to CD4+ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8+ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.

Adverse reactions to co-trimoxazole in HIV infection: a reappraisal of the glutathione-hydroxylamine hypothesis.

It is postulated that the unstable hydroxylamine metabolite of sulphamethoxazole is responsible for the adverse reactions to co-trimoxazole and in HIV infection systemic glutathione deficiency leads to a reduced capacity to counteract the hydroxylamine toxicity. This hypothesis has been investigated by studying the metabolism of sulphamethoxazole and assessing glutathione status in HIV infection in order to explore the modification of treatment. It is concluded that the toxicity of plasma sulphamethoxazole hydroxylamine is counteracted by normal glutathione concentrations as is the case in HIV-seropositive patients, but that increased oxidation within certain cells in HIV infected individuals may possibly give rise to increased concentrations of reactive intermediates of sulphamethoxazole. Sulphametrole and sulphamethoxazole have similar half-lives but are metabolized differently: in vivo no oxidised metabolites of sulphametrole could be detected. In a retrospective study the rate of adverse reactions to trimethoprim-sulphametrole appeared to be in the lower range of those reported for trimethoprim-sulphamethoxazole indicating that the combination of trimethoprim-sulphametrole may be more favourable. The ratio of trimethoprim:sulphonamide is 1:5, but in-vitro studies with Toxoplasma gondii indicate that because of the synergic effect of both agents the dose of sulphonamide is possibly unnecessarily high.

Expression of a protective gene-prolongs survival of T cells in human immunodeficiency virus-infected patients.

The resistance of acquired immunodeficiency syndrome (AIDS) to traditional drug therapy has prompted a search for alternative treatments for this disease. One potential approach is to provide genetic resistance to viral replication to prolong latency. This strategy requires the definition of effective antiviral genes that extend the survival of T cells in human immunodeficiency virus (HIV)-infected individuals. We report the results of a human study designed to determine whether a genetic intervention can prolong the survival of T cells in HIV-infected individuals. Gene transfer was performed in enriched CD4+ cells with plasmid expression vectors encoding an inhibitory Rev protein, Rev M10, or a deletion mutant control, deltaRev M10, delivered by gold microparticles. Autologous cells separately transfected with each of the vectors were returned to each patient, and toxicity, gene expression, and survival of genetically modified cells were assessed. Cells that expressed Rev M10 were more resistant to HIV infection than those with deltaRev M10 in vitro. In HIV-infected subjects, Rev M10-transduced cells showed preferential survival compared to deltaRev M10 controls. Rev M10 can therefore act as a specific intracellular inhibitor that can prolong T-cell survival in HIV-1-infected individuals and potentially serve as a molecular genetic intervention which can contribute to the treatment of AIDS.

Mycobacteria-reactive gamma delta T cells in HIV-infected individuals: lack of V gamma 9 cell responsiveness is due to deficiency of antigen-specific CD4 T helper type 1 cells.

Human gamma delta T lymphocytes expressing the variable T cell receptor elements V gamma 9 paired with V delta 2 are activated by antigen derived from Mycobacterium tuberculosis (M. tb.) and presented by antigen-presenting cells (APC). The subsequent proliferation is strictly dependent on the presence of CD4+ TCR alpha beta+ T helper type 1 (Th1) cells producing interleukin-2 (IL-2). In this study, we report that the reactivity of V gamma 9 cells to M. tb. stimulation in vitro was drastically decreased or absent in the majority of the analyzed HIV-1-infected individuals (CDC stages III and IV). We show that the failure of V gamma 9 cells from HIV+ individuals to proliferate following M. tb. stimulation was not due to an intrinsic qualitative or quantitative defect of gamma delta T cells but rather to a deficiency of M. tb.-reactive CD4 Th1 cells. Thus, V gamma 9 responsiveness could be restored if cultures of M. tb.-stimulated T cells from HIV+ donors were reconstituted with one of the following: (i) exogenous IL-2 (ii) purified CD4 T cells from allogeneic donors; or (iii) T cell-depleted APC from allogeneic donors. In the majority of HIV+ patients, the defective Th1 activity of M. tb.-stimulated CD4 T cells could be decreased neither by cytokines known to favor Th1 development (IL-12, interferon-gamma) nor by neutralization of the Th1-suppressing Th2 cytokine IL-10. We suggest that measurement of V gamma 9 cell expansion within M. tb.-stimulated peripheral blood mononuclear cells provides a sensitive assay for the functional capacity of antigen (M. tb.)-specific CD4 Th1 cells in HIV-infected individuals.

The Fas receptor in HIV infection

To analyse the role of the apoptosis-inducing Fas receptor in the depletion of CD4+ and CD8+ T cells in HIV-infected individuals. Peripheral blood lymphocytes (PBL) obtained from HIV-infected subjects of all 1993 Centers for Disease Control and Prevention (CDC) stages and from non-infected controls were examined. A two-colour cytofluorometry was employed using monoclonal antibodies against Fas receptor (CD95) in combination with the surface markers CD4, CD8, CD28, CD26 and CD45RO. CD4+ and CD8+ T-cell-enriched PBL were used as target cells to assess their susceptibility to lysis by CD4+ cytotoxic T lymphocytes (CTL) which kill via the Fas pathway. Fas+PBL are more elevated in HIV-infected individuals than in HIV-negative controls and increase significantly from CDC stages A to C. Whereas Fas+CD4+ and Fas-CD4+ T-cell populations decline in parallel with the progression of HIV infection, the Fas+CD8+, but not of the Fas-CD8+ fraction, significantly increases. The Fas+CD8+ lymphocytes are susceptible to Fas-mediated lysis as they are efficiently killed by Fas-ligand+CD4+CTL. The Fas receptor may contribute, but not as a unique cause, to the decline of CD4+ T cells in HIV-infected individuals. This and the significant increase of the number of Fas+ CD8+ T cells indicates that Fas-mediated immune regulation is disturbed.

Activation-induced peripheral blood T cell apoptosis is Fas independent in HIV-infected individuals.

T cell apoptosis has been proposed as an important contributor to the functional defects and depletion of T cells in HIV-infected individuals. However, the mechanisms involved in this apoptosis have not been elucidated. We recently showed that peripheral blood T cells from HIV-infected individuals are especially susceptible to Fas antigen-induced apoptosis. In this study we examine the role of Fas, CTLA-4, tumor necrosis factor (TNF) receptors (TNFR) and CD30, receptors known to be involved in T cell activation-induced cell death (AICD), in the spontaneous and activation (anti-CD3)-induced apoptosis of peripheral blood T cells from asymptomatic HIV-infected individuals. We report here that spontaneous and activation-induced T cell apoptosis cannot be inhibited by reagents that block interactions of Fas, CTLA-4, p55 and p75 TNFR and CD30 with their respective ligands. We also show that IL-12, IFN-gamma, IL-4 and IL-10 cannot modify spontaneous, activation- and anti-Fas-induced apoptosis. Anti-Fas preferentially induced CD4+ T cell apoptosis whereas AICD induced apoptosis equally in CD4+ and CD8+ T cells. We conclude that T cell AICD in HIV infection is not mediated by Fas, thus indicating that Fas-induced and activation-induced T cell apoptosis are independent mechanisms of apoptosis which may play different roles in the pathogenesis of HIV infection.

Changes in antigen densities on leukocyte subsets correlate with progression of HIV disease

In a cross-sectional study of 154 HIV-infected and 33 uninfected healthy adults, we show that characteristic changes in the levels of expression of leukocyte surface antigens occur in the HIV-infected individuals. These changes, which collectively occur on virtually every leukocyte subset, are specific: a particular antigen may increase or decrease on one subset of PBMC but remain constant on another. Furthermore, within any particular subset, the levels of one or more antigens may change, while the levels of other surface antigens on the same cells remain constant. Some of these antigens density changes have been noted before, e.g. increased CD20 on B cells, and increased CD38 and HLA-DR on CD8 T cells. However, the multiparameter flow cytometry methodology used here reveals changes in a substantially larger number of surface markers, some of which are restricted to fine subsets of PBMC, such as naive or memory T cell subsets. For many of these antigens, the change in expression correlates with absolute CD4 counts >500/microl; others differ only in those with counts >100microl. The changes in antigen densities we observed on B and T cells are consistent with the observation of a persistent quasi-activated state of these cells in HIV-infected individuals. Similarly, the altered expression of the signal-transducing molecules CD7 and CD16 that we demonstrated for NK cells may correlate with the functional defects previously demonstrated in NK cells. Thus, measurements of antigen densities such as those demonstrated here may provide surrogate markers for the altered functional capacities of PBMC subsets in HIV-infected individuals, and may thereby provide a much simpler assay for immunocompetence than in vitro functional assays.

Role of TH1/TH2 Cytokines in HIV Infection

Different experimental approaches were used to prove or disprove the "TH1/TH2 switch theory" of HIV-infection. No increase, or even a decrease, in the production of TH2-type cytokines (IL-4, IL-5, and IL-10) by either bulk circulating mononuclear cells or CD4+ T-cell clones generated by PHA stimulation of single T cells from HIV-infected individuals in all stages of disease compared to HIV-negative donors was observed. However, enhanced proportions of CD4+ T-cell clones able to produce both TH1-type and TH2-type cytokines (TH0 clones) were derived from either skin-infiltrating, in vivo-activated, T cells or in vitro antigen-stimulated peripheral blood T cells of HIV-infected individuals. Of note, TH1, TH2 and TH0 clones obtained from HIV-seronegative healthy donors showed different ability to support viral replication after infection with HIV in vitro. All TH2 and most TH0 clones supported HIV replication efficiently, whereas TH1 clones did not. These results suggest preferential HIV replication in T cells producing TH2-type cytokines rather than TH1/TH2 switch in HIV infection.

Alternative complement pathway activation by CD4+ T cells of HIV infected individuals: a possible role in AIDS pathogenesis.

The mechanisms by which CD4+ T cells are eliminated during HIV infection are poorly understood. We have previously shown that HIV infected cell lines activate and fix C3 via the alternative complement pathway (ACP). In the present study we examined the ability of blood lymphocytes from 40 HIV+ individuals to fix C3. A large fraction of the CD4+ T cells reacted with anti-gp120 antibodies. These cells also carried C3 fragments in vivo and could further fix C3 if exposed to human serum in vitro. C3 activation occurred via the ACP. In some cases exposure of the lymphocytes to human serum under conditions allowing ACP activation resulted in partial elimination of CD4+ T cells. The results suggest that complement activation and fixation by CD4+ T cells opsonized with HIV particles or gp120 may contribute to their selective destruction.

CONTRIBUTION OF MATHEMATICAL MODELLING TO ELUCIDATION OF AIDS PATHOGENESIS

Although HIV is cytopathogenic for CD4+ lymphocytes in vitro, the depletion of these cells in HIV-infected individuals seems to be caused by some other mechanism. It is probably a direct destructive or inhibitory effect of the viral products or an (auto)immune reaction elicited by them, eventually directed at them. Mathematical model of immunological tolerance was used for simulation of CD4+ lymphocyte depletion dynamics in HIV infection under the assumption that it is caused by HIV products. This model was not able to simulate the observed three-stage dynamics of CD4+ cell counts, i.e., drop of these counts around seroconversion, followed by a slow decrease over a prolonged period and an accelerated decrease before the development of AIDS. When an immune reaction limiting HIV reproduction was included in the model, all these three phases of CD4+ lymphocyte depletion could be simulated. In the paper, different modifications and extensions of the model are reviewed, compared with available clinical data, and their relevance for HIV research is discussed.

HIV infection leads to differential expression of T-cell receptor V beta genes in CD4+ and CD8+ T cells.

To analyse variation in T-cell receptor (TCR) V beta gene expression in T cells in HIV-infected individuals. Because there are very few monoclonal antibodies available for studying TCR V beta gene expression, we used polymerase chain reaction (PCR) to analyse the TCR V beta repertoire in HIV-infected individuals using specific primers for 20 distinct families of TCR V beta. Evaluation of TCR V beta gene expression in peripheral blood from HIV-1-infected individuals [two in Centers for Disease Control (CDC) stage II, five in CDC stage III and four in CDC stage IV]. Complementary DNA was produced from CD4+ and CD8+ T cells, amplified by PCR and analysed after Southern blotting and hybridization with a C beta-specific oligonucleotide probe. V beta gene expression was dramatically modified, especially in AIDS patients. The CD4+ T-cell subset showed both overexpression (V beta 2) and deletions or underexpression (V beta 9-V beta 20), whereas these gene segments were expressed normally in the CD8+ subset. Only V beta 3 was deleted or underexpression in both CD4+ and CD8+ populations in AIDS patients. HIV-1 infection induces CD4+ T-cell deficiency, both in total numbers and by causing a paucity of select V beta gene expression in this subset. In addition, the V beta 3 gene family was deleted or underexpressed was observed in both CD4+ and CD8+ T-cell subsets from patients in CDC stage IV. These results are compatible with changes in V beta gene expression known to occur under the action of endogenous or exogenous superantigens.

Complement and virus-specific antibody-dependent infection of normal B lymphocytes by human immunodeficiency virus type 1

We tested the susceptibility of human purified, normal B lymphocytes to human immunodeficiency virus type 1 (HIV-1) infection, in the presence or absence of complement-sufficient serum and of virus-specific antibodies. Virus replication was detected when cells were infected in the presence of both complement and anti-HIV antibodies (C'-ADE conditions), by day 2 postinfection. Similar results were obtained when B lymphocytes were purified either from peripheral blood (three healthy donors) or from tonsils (four individuals with chronic tonsillitis). HIV infection was shown by polymerase chain reaction (PCR) detection of proviral sequences (gag and pol genes), by p24 antigen synthesis, and by cocultivation assay with MT2 cells. The higher p24 production was obtained when B cells were preactivated for 2 days by phorbol 12-myristate 13-acetate (PMA) before infection and then cultured in the presence of low-molecular weight B-cell growth factor (LMW-BCGF). Expression of virus envelope glycoprotein (gp) 120 could also be detected on a subpopulation of B cells (CD19+, CD22+) by flow cytometry. Blocking experiments with monoclonal antibodies (MoAbs) against CD4, CD21 (complement receptor 2 [CR2]), CD35 (CR1), CD19, and CD5 surface molecules indicated that infection of B cells involves CD4, CD21, and CD35 antigens. Indeed, blocking of CD4 receptor inhibited 10% of p24 production, and blocking of both CD21 and CD35 led to extinction of p24 signal. CR-dependent pathway is thus a major route for C'-ADE of HIV infection in normal B cells. Our results emphasize the importance of studying interactions between HIV and the complement system for better understanding infection mechanisms and the major dysfunctions of B cells in HIV-infected individuals.

Complement and Virus-Specific Antibody-Dependent Infection of Normal B Lymphocytes by Human Immunodeficiency Virus Type 1

Abstract We tested the susceptibility of human purified, normal B lymphocytes to human immunodeficiency virus type 1 (HIV-1) infection, in the presence or absence of complement-sufficient serum and of virus-specific antibodies. Virus replication was detected when cells were infected in the presence of both complement and anti-HIV antibodies (C'-ADE conditions), by day 2 postinfection. Similar results were obtained when B lymphocytes were purified either from peripheral blood (three healthy donors) or from tonsils (four individuals with chronic tonsillitis). HIV infection was shown by polymerase chain reaction (PCR) detection of proviral sequences (gag and pol genes), by p24 antigen synthesis, and by cocultivation assay with MT2 cells. The higher p24 production was obtained when B cells were preactivated for 2 days by phorbol 12- myristate 13-acetate (PMA) before infection and then cultured in the presence of low-molecular weight B-cell growth factor (LMW-BCGF). Expression of virus envelope glycoprotein (gp) 120 could also be detected on a subpopulation of B cells (CD19+, CD22+) by flow cytometry. Blocking experiments with monoclonal antibodies (MoAbs) against CD4, CD21 (complement receptor 2 [CR2]), CD35 (CR1), CD19, and CD5 surface molecules indicated that infection of B cells involves CD4, CD21, and CD35 antigens. Indeed, blocking of CD4 receptor inhibited 10% of p24 production, and blocking of both CD21 and CD35 led to extinction of p24 signal. CR-dependent pathway is thus a major route for C'-ADE of HIV infection in normal B cells. Our results emphasize the importance of studying interactions between HIV and the complement system for better understanding infection mechanisms and the major dysfunctions of B cells in HIV-infected individuals.

High proportion of gamma-delta T cell receptor positive T cells in bronchoalveolar lavage and peripheral blood of HIV-infected patients with Pneumocystis carinii pneumonias.

To investigate the local immunological situation in the lung of HIV-infected patients with Pneumocystis carinii pneumonias (HIV-PCP), we analyzed the proportion and the distribution of lymphocyte subpopulations and their state of activation in bronchoalveolar lavage (BAL) and peripheral blood of 21 HIV-PCP patients (CDC classification group IV) compared to 24 HIV-negative patients with interstitial lung diseases (ILD). Peripheral blood lymphocytes (PBL) and BAL cells were stained with monoclonal antibodies. Two-color cytofluorometric analysis (flow cytometry) was performed with a cytofluorograph (Epics Profile, Coulter Corp., Hialeah, Fla., USA). In BAL from HIV-PCP patients the number of CD3-positive lymphocytes was significantly increased, yet there was no difference in the number of macrophages and neutrophils when compared to patients with ILD. Quantification of lymphocyte subpopulations showed that the increased number of BAL CD3-positive lymphocytes in HIV-PCP patients was mainly due to a significantly increased number of CD8-positive T cells, while the pulmonary CD4-positive T cells were decreased both in relative and absolute numbers. As a consequence, an inverted pulmonary CD4/CD8 ratio resulted for HIV-infected patients with PCP. Analysis of in-vivo-activated T cells in BAL and peripheral blood when measured by the expression of IL-2R, HLA-DR and VLA-1 revealed increased numbers of IL-2R and HLA-DR bearing CD8-positive T cells but significantly decreased numbers of IL-2R and HLA-DR bearing CD4-positive T cells as well as a higher number of CD8/CD57 double positive T cells in HIV-infected individuals when compared to patients with ILD.(ABSTRACT TRUNCATED AT 250 WORDS)

Activated B lymphocytes from human immunodeficiency virus-infected individuals induce virus expression in infected T cells and a promonocytic cell line, U1.

Freshly isolated B lymphocytes from patients infected with human immunodeficiency virus (HIV), in contrast to B cells from normal controls, were shown to induce viral expression in two cell lines: ACH-2, a T cell line, and U1, a promonocytic cell line, which are chronically infected with HIV, as well as in autologous T cells. In 10 out of 10 HIV-infected individuals with hypergammaglobulinemia, spontaneous HIV-inductive capacity was found with highly purified peripheral blood B cells, whereas peripheral blood or tonsillar B cells from six healthy, HIV-negative donors did not induce HIV expression unless the cells were stimulated in vitro. The induction of HIV expression was observed in direct coculture experiments of B lymphocytes and HIV-infected cells, and could also be mediated by supernatants from cultures of B cells. Significantly higher amounts of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) were detected in the B cell culture supernatants from HIV-infected patients with hypergammaglobulinemia (IL-6: mean = 536 pg/ml; TNF-alpha: mean = 493 pg/ml), as compared with normal uninfected controls (IL-6: mean = 18 pg/ml; TNF-alpha: mean = 23 pg/ml). Antibodies against these cytokines abolished the HIV-inductive capacity of B cells. We conclude that in vivo activated B cells in HIV-infected individuals can upregulate the expression of virus in infected cells by secreting cytokines such as TNF-alpha and IL-6, and, therefore, may play a role in the progression of HIV infection.

Confocal Microscopic Detection of Human Immunodeficiency Virus RNA-Producing Cells

A central anomaly in the pathogenesis of AIDS is that few actively infected CD4+ cells (1 in 10(4)-10(5) have been detected in the peripheral blood, even though dramatic depletion (often greater than 90%) of CD4+ cells is the hallmark of disease progression. A sensitive, 35S-based human immunodeficiency virus (HIV) RNA in situ hybridization technique was coupled with a new detection method, confocal laser scanning microscopy, to examine transcriptionally active HIV-infected cells from individuals at different disease stages. In 35 symptomatic HIV-infected individuals (AIDS and AIDS related complex), an average of 1 in 350 mononuclear cells produced HIV RNA. In contrast, in an asymptomatic group of 30 individuals, an average of 1 in 2000 mononuclear cells produced HIV RNA. These data, obtained using this improved detection method, suggest there are more HIV RNA-producing cells in HIV-infected individuals than previously reported. In addition, increased numbers of HIV transcribing cells were found to correlate with declining clinical condition as assessed by Karnofsky performance score. These data suggest that viremia per se may account for the pathologic consequences in HIV infection.

Preferential infection of CD4+ memory T cells by human immunodeficiency virus type 1: evidence for a role in the selective T-cell functional defects observed in infected individuals.

CD4+ T cells of patients with AIDS exhibit a qualitative defect in their ability to respond to soluble antigen while their responses to mitogens remain normal. CD4+ T cells can be broadly divided phenotypically into "naive" [CD45RA+ (2H4+)] and "memory" [CD29+ (4B4+) or CD45RO+ (UCHL1+)] cell subpopulations, which represent distinct maturation stages. To determine the human immunodeficiency virus type 1 (HIV-1) infectability of memory and naive CD4+ T-cell subsets in vitro and to determine the in vivo preference of HIV-1 in these subpopulations, we obtained highly purified CD4+ T-cell subsets from normal and HIV-1-infected individuals and studied them by viral cultivation, quantitative polymerase chain reaction, and functional assays. Polymerase chain reaction studies demonstrated that the memory cell subset of CD4+ T cells is preferentially infected (4- to 10-fold more than naive T cells) by HIV-1 in vitro, and these memory cells are the principal reservoir for HIV-1 within CD4+ T cells obtained from infected individuals. Functional abnormalities attributable to CD4+ T cells in HIV-infected individuals (failure to respond in vitro to soluble antigen or to anti-CD3 monoclonal antibodies) were shown to reside primarily within these memory cells. Thus, the present study suggests that the selective functional defects present in the memory CD4+ T-cell subset of HIV-infected individuals may be a direct result of the preferential infection and consequently greater viral burden within these cells.

Priming of CD4+ T cells specific for conserved regions of human immunodeficiency virus glycoprotein gp120 in humans immunized with a recombinant envelope protein.

A nonglycosylated denatured form of human immunodeficiency virus (HIV) 1 glycoprotein gp120 (Env 2-3), which does not bind to CD4, was used with muramyl tripeptide as adjuvant to immunize HIV-seronegative healthy volunteers. In all the volunteers, three 50-micrograms injections of Env 2-3 induced priming of CD4+ T cells specific for conserved regions of the native glycosylated gp120. Moreover, we found that several major histocompatibility complex class II (DR) alleles can function as restriction molecules for presentation of conserved epitopes of gp120 to T cells, implying that a T-cell response to these epitopes can be obtained in a large fraction of the population. The possibility to prime CD4+ T cells specific for conserved epitopes of a HIV protein is particularly important in view of the lack of such cells in HIV-infected individuals and of a possible role that CD4+ T cells may play in the development of protective immunity against AIDS.