Human immunodeficiency virus type 1 (HIV-1) genomic sequences and distinct changes in CD8+ lymphocytes precede detectable levels of HIV-1 antibodies in high-risk homosexuals

Validity of existing CD4+ classification in north Indians, in predicting immune status

BACKGROUND

The CD4 lymphocyte count had ethnic variability as observed in many studies. In populations with CD4 counts inherently lower than in the West, the Center for Disease Control and Prevention (CDC) classification system of HIV-infected individuals may not be appropriate. As there is no such criterion currently available for ethnic north Indians HIV-patients, we undertook this study to assess the applicability of the western case definition in north Indian HIV patients.

METHODS

The CD4 counts of 40 normal and 376 HIV-infected north Indian adults attending to ID clinic, SS hospital, Varanasi were estimated by flowcytometry. The mean CD4 counts were estimated and compared between CDC groups A, B and C and controls. Receiver operator characteristic (ROC) curves were generated to determine the cut-off that correlated best with clinical staging for this population.

RESULTS

For CDC groups A, B and C, the mean CD4 counts/mul (upper limits of the 95% CI) were 380.3, 249.2 and 120.9, while the mean CD4 levels in healthy volunteers was 818.4.

CONCLUSION

The mean CD4 count among normal north Indians is significantly lower than that in the western population and parallels that of the Chinese. When categorized based on the Center for Disease Control and Prevention (CDC) classification system, the mean CD4 counts in HIV-infected individuals was lower. Categories of CD4 counts >280, 120-280 and < or =120 cells/microl correlate better with disease progression among HIV-infected individuals. A longitudinal study is required before guidelines for the India population can be devised.

Virus load correlates inversely with the expression of cytotoxic T lymphocyte activation markers in HIV-1-infected/AIDS patients showing MHC-unrestricted CTL-mediated lysis

Cytotoxic T lymphocytes (CTL) are key players to suppress viral load (VL) but CTL responses become compromised with progression of HIV-infection/AIDS. Some progressors develop MHC-unrestricted CTL with anti-CD4+ cytocidal activity. Immune activation status of these CTL and its significance in disease progression are unknown. To determine the relationship between VL and T cell activation, a cross-sectional study was carried out using blood samples from 13 HIV-1-infected/AIDS patients at various stages of progression and seven age-matched seronegative controls. We examined expression of HLA-DR and CD38 activation markers on purified CTL. MHC-unrestricted killing by these CTL was also evaluated against uninfected, allogeneic CD4+ T cells as well as several human cell lines. The expression of activation markers correlated inversely (rs = - 0.91, P < 0.0001) with VL of the subjects. CTL effectors of these patients killed targets expressing or lacking CD4+, independently of MHC class I recognition. Interestingly, the patients with higher VL showed an increased number of gammadeltaTCR-bearing CTL in blood and their MHC-unrestricted killing activity was blocked significantly (P < 0.01) by gammadeltaTCR-specific monoclonal antibody. CD3+ T counts of these patients were also consistently subnormal. Inverse correlation between VL and CD8+ T cell activation markers seems to be an indicator of CTL-associated immunopathogenesis in HIV patients with elevated gammadeltaCTL in the peripheral blood.

Highly active antiretroviral therapy during early HIV infection reverses T-cell activation and maturation abnormalities. Swiss HIV Cohort Study

OBJECTIVES

To evaluate the impact of early initiation of highly active antiretroviral therapy (HAART) on disease-induced T-cell activation and maturation abnormalities during asymptomatic HIV infection.

DESIGN

A prospective open-label trial of zidovudine, lamivudine and ritonavir in treatment-naive asymptomatic HIV-infected individuals with CD4 cells > or = 400 x 10(6)/l.

METHODS

Peripheral blood CD4+ and CD8+ T cells derived from 15 asymptomatic HIV-infected individuals (median baseline CD4+ cells, 608 x 10(6)/l; CD8+ cells, 894 x 10(6)/l; plasma HIV RNA, 3.93 log10 copies/ml) undergoing therapy with zidovudine (300 mg twice daily), lamivudine (150 mg twice daily), and ritonavir (600 mg twice daily) were assessed for changes in expression of phenotypic markers of T-cell activation (HLA-DR and CD38) and maturation (CD45RA and CD45RO). At weeks 0, 2, 4, 8, 12, 16, 20 and 24, T-cell subsets were quantified by flow cytometry and plasma HIV viral loads determined using reverse transcription PCR.

RESULTS

HAART-induced decrease in plasma HIV RNA levels coincided with a significant reduction in numbers of activated CD4+/HLA-DR+ (maximum change, -36%; P < or = 0.05), CD8+/HLA-DR+ (maximum change, -66%; P < or = 0.005) and CD8+/CD38+ (maximum change, -51%; P < or = 0.01) T cells. A concomitant significant increase in numbers of naive CD4+/CD45RA+ (maximum change, +12%; P < or = 0.005) and memory CD4+/CD45RO+ (maximum change, +6%; P < or = 0.05) T cells was also evident, which contrasted with a significant decrease in memory CD8+/CD45RO+ cells (maximum change, -42%; P < or = 0.005).

CONCLUSION

The observed ability of HAART during early asymptomatic HIV infection to initiate rapid reversal of disease-induced T-cell activation and maturation abnormalities, while preserving pretherapy levels of immune function, supports the concept that therapeutic advantage is to be gained by commencing early aggressive antiretroviral therapy.

Concentrations of soluble CD95 and CD8 antigens in the plasma and levels of CD8+CD95+, CD8+CD38+, and CD4+CD95+ T cells are markers for HIV-1 infection and clinical status

Apoptosis mediated via the CD95 (FAS/APO-1) receptor is thought to play a role in the depletion of CD4+ T cells in HIV infection. In the present study expression of the CD95 antigen on lymphocyte subsets and the plasma level of soluble CD95 (sCD95) were determined in HIV-1-infected adults. The expression of CD95 was increased on CD8 cells in all groups of HIV+ individuals, while increased expression of CD95+ cells on CD4 cells was limited to individuals with CD4 counts of < 200 mm3. The proportion of CD4+ that expressed CD95 was inversely correlated with the percentage of CD4+ PBL. The concentration of sCD95 was significantly higher in the plasma of HIV-infected individuals than in normal controls. The level of sCD95 in HIV-infected subjects showed no correlation with the percentage of PBL expressing CD95, indicating that the increased level of sCD95 did not reflect release from CD95+ PBL. The plasma sCD95 concentration was significantly correlated with the percentage of CD8+ cells and, particularly, with CD8+ CD38- cells. A striking inverse correlation was found between the sCD95 plasma concentration and the proportion of CD4+ CD95+ cells out of the total CD4+ population. There was no correlation between the serum level of sCD95 and that of soluble CD8 (sCD8), both of which were increased in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals was correlated with the percentage of CD95+ and CD8+ CD38+ cells. The present study indicates that plasma sCD95 may be one of the factors that regulate apoptotic death of lymphocytes in HIV infection.

Correlation of CD8 lymphocyte activation with cellular viremia and plasma HIV RNA levels in asymptomatic patients infected by human immunodeficiency virus type 1

The relationship between CD8 lymphocyte phenotypic alterations and virological parameters was studied in 47 asymptomatic subjects with human immunodeficiency virus type 1 (HIV-1) infection and CD4 T cell counts above 400/microliters. CD8 subsets were examined by means of three-color flow cytometry, using an extensive panel of monoclonal antibody combinations. Virological parameters were measured by both end-point dilution culture of peripheral blood mononuclear cells (PBMCs) and plasma and branched-DNA (bDNA) signal amplification of plasma HIV RNA. Whereas HIV-infected patients had a near-normal CD4 cell count (mean, 782 cells/microliter), several subsets of activated CD8 cells were markedly expanded relative to values in 23 HIV-seronegative controls. The PBMC cultures were positive in 38 cases and plasma HIV RNA was detected in 31. The percentage of CD4 cells correlated negatively with both cellular viremia and plasma HIV RNA levels. Conversely, a positive correlation was observed between viral load and the percentage of CD8 cells. Among CD8 lymphocytes, the CD38+CD8 and HLA-DR+CD8 subsets correlated best with viral load. Three-color analysis showed that the subpopulations involved in this relationship were CD38+HLA-DR+, CD38+CD28-, HLA-DR+CD28+, HLA-DR+CD57-, CD38+CD57-, CD38+CD45RO+, and HLA-DR+CD45RO+. Our data provide the first evidence that viral load correlates with subsets of activated CD8 lymphocytes in asymptomatic HIV-infected subjects who have near-normal numbers of CD4 lymphocytes.

Depression in caregivers of demented patients is associated with altered immunity: impaired proliferative capacity, increased CD8+, and a decline in lymphocytes with surface signal transduction molecules (CD38+) and a cytotoxicity marker (CD56+ CD8+)

Changes in relevant immune parameters, including function, were found to be associated with depression in elderly caregiver wives of demented patients. We studied the relationship between immune cell phenotype and T cell proliferative capacity of such caregivers to levels of stress and depression over the course of a support group intervention. The data indicate the strongest association between depression (of all stress parameters) and impaired T cell proliferative capacity. Depression was also most strongly (of stress parameters) associated with a shift in T cell populations with an increase in CD8+ T cells, and a reduced percentage of CD38+ cells in both CD8+ and CD4+ T cell populations. Since CD38 is a signal transduction factor, it was interesting that a decreased percentage of CD38+ cells correlated with impaired T cell function (proliferation). Another significant difference was the reduction in natural killer (NK) cells as well as the percentage of the CD56+ component of the CD8+ population. This latter subset is important in MHC-unrestricted cytotoxicity, and has been found expanded in healthy centenarians. This study shows that both chronic stress, and depression in particular, and age have deleterious effects on T cells, and together could significantly contribute to the higher risk of disease and mortality associated with being a caregiver of a demented individual.

Frequency of provirus-bearing CD4+ cells in HIV type 1 infection correlates with extent of in vitro apoptosis of CD8+ but not of CD4+ cells

Lymphocytes from HIV-1-infected subjects undergo massive apoptosis when cultured in vitro, and this phenomenon might reflect pathogenetic mechanisms leading to immune dysfunction in vivo. However, (1) lymphocyte death is not restricted to CD4+ cells but seems to involve predominantly CD8+ cells, and (2) the same phenomenon occurs in other viral infections. Furthermore, it is not known whether a relationship exists between the HIV-1 burden and this type of cell death. In this work we sought to determine whether the HIV-1 provirus load correlates with the propensity to apoptosis of CD4+ and CD8+ cells. We studied 10 HIV-1-infected patients with CD4+ cell counts above 500/mm3 and free of concomitant infections. We correlated the frequency of HIV-1-infected CD4+ cells with the extent of culture-induced apoptosis as well as with the phenotype of the apoptotic lymphocytes. We found that the magnitude of apoptosis correlated with the frequency of HIV-1-infected CD4+ cells (p = 0.0007), and that increasing viral load and apoptosis were associated with a shift to the selective death of CD8+ cells. Our data support the view that, in addition to CD4+ cell killing, another immunopathogenic effect of HIV might be that of priming CD8+ cells to apoptosis. In vivo, this could eventually lead to the exhaustion of the cytotoxic T cell compartment.

Cellular immune responses in rhesus macaques infected rectally with low dose simian immunodeficiency virus

Monkeys infected rectally with low dose simian immunodeficiency virus (SIV) were resistant to high dose challenge with SIV. Peripheral blood mononuclear cells (PBMC) from two of four challenged monkeys were unable to support SIV replication in vitro unless cultures were depleted of CD8+ lymphocytes. Monkeys that had survived high dose rectal infection with SIV also suppressed virus replication in cultured PBMC. PBMC from uninfected monkeys supported virus replication in both unfractionated and CD8-depleted cultures. Virus-suppressive activity of PBMC may be an important correlate of protective immunity in AIDS.

Lysis of CD4+ lymphocytes by non-HLA-restricted cytotoxic T lymphocytes from HIV-infected individuals

Individuals infected with HIV have elevated numbers of total and activated CD8+ lymphocytes in peripheral blood. CD8+ lymphocytes from HIV-infected individuals have been shown to mediate non-human histocompatibility-linked antigen (HLA)-restricted suppression of viral replication, HLA-restricted killing of cells expressing HIV antigens, and killing of uninfected lymphocytes. We studied CD8+ T lymphocytes that lysed autologous CD4+ lymphocytes. heterologous CD4+ lymphocytes from HIV-infected individuals and uninfected CD4+ lymphocytes. Killing in all cases required T cell receptor (TCR)-mediated recognition or triggering. However, these CD8+ cytotoxic T lymphocytes (CTL) killed HLA class I mismatched CD4+ lymphocytes and CD4+ lymphocytes treated with a MoAb against HLA-A, B and C antigens (PA2.6) which blocks HLA class I-restricted killing. HLA class II-negative CD4+ T lymphoma cells (CEM.NKR) were also killed by anti-CD3 inhibited CTL. Stimulation of peripheral blood lymphocytes (PBL) from HIV-infected individuals, but not uninfected controls, with concanavalin A (Con A) and IL-2, induced non-HLA-restricted TCR alpha beta+, CD8+ CTL which lysed CD4+ lymphocytes. Activation of CD4+ lymphocytes increased their susceptibility to CD8+ CTL-mediated lysis. In HIV infection, a population of non-HLA-restricted CTL which lyse activated CD4+ lymphocytes is expanded. The expansion of CTL with unusual characteristics is interesting, because the stimulus for this expansion is unknown. CTL which recognize activated CD4+ cells could play a role in immune regulation and the pathogenesis of AIDS.

Surgical issues in the management of the HIV-infected patient

As of 1992, approximately 1,000,000 Americans are infected with HIV. The natural history of the illness includes a relatively long latent period (about 10 years) between infection and development of AIDS. Surgeons are called on to participate in the management of these patients, usually for diagnostic biopsies, supportive measures, or intraabdominal events. Precautions and safe surgical practices will minimize the risk of HIV transmission from patient to surgeon (or surgeon to patient).

Phenotypic characterization of CD8+ T cell populations in HIV disease and in anti-HIV immunity

The CD8+ T cell population is believed to play an important role in the control of viral infection, both for suppression of viral replication and for cytotoxic activity against viral infected cells. Elevated numbers of CD8+ T cells have been demonstrated in HIV infection, and CD8+ cytotoxic T cell (CTL) activity is associated with the early, asymptomatic stage of disease. We investigated the phenotypic characteristics of the CD8 population, in whole blood, in HIV disease and determined the predominant CD8+ subpopulation involved in anti-HIV CTL activity. We found that CD8+ T cells co-expressing markers of activation (HLA-DR), memory (CD45RO, CD29), and cytotoxic activity (S6F1) were significantly elevated in the early stages of disease, while the numbers of naive (CD45RA) cells remained unchanged. Progression to AIDS resulted in an overall loss of absolute CD8+ T cells, though the percentages of CD8+ HLA-DR+ and CD8+ S6F1+ remained elevated. In contrast to patients in the late stages of disease, anti-HIVgag CTL activity, following in vitro stimulation, was present in most HIV+ asymptomatic subjects and was associated with an expansion of CD8+ HLA-DR+ and CD8+ CD45RO+ cells. The absence of CTL activity was associated with a reduced ability of these populations to expand in vitro and with a significant loss of peripheral CD4+ T cells, independent of clinical stage. We suggest that CD8+ expressing HLA-DR+ CD45RO+ and S6F1+ play an important role in anti-HIV cytotoxicity.

Increases in soluble CD8 antigen in plasma, and CD8+ and CD8+CD38+ cells in human immunodeficiency virus type-1 infection

Increases in plasma levels of soluble CD8 (SCD8) antigen and expansion of the CD8+ CD38+ lymphocyte compartment were early immunologic alterations frequently observed prior to detection of antibodies against human immunodeficiency virus type 1 (HIV-1) and diminution of CD4+ cells in subjects at risk to develop AIDS. These increases identified in the 49 seronegative homosexual men were manifest in all 164 homosexual subjects and 45 intravenous drug users (IVDU) positive for HIV-1 antibodies (HIV-1+), 19 patients with ARC, and 29 AIDS patients. Augmentation of plasma sCD8 antigen correlated with increases in both CD8+ and CD8+ CD38+ cells in HIV-1(-) homosexual men (r = 0.35, P less than 0.013; r = 0.48, P less than 0.0005; respectively) and the 258 HIV-1+ subjects (r = 0.25, P less than 0.0003; r = 0.33, P less than 0.0001, respectively). In vitro examination of unstimulated peripheral blood lymphocytes from HIV-1+ homosexuals and IVDU confirmed the fivefold higher constitutive levels of cellular release of sCD8 antigen in these subjects compared to heterosexual controls. Inclusion of radiolabeled amino acids during the 3-day culture period in the presence or absence of phytohemagglutinin resulted in negligible levels of radioactivity associated with the sCD8 antigen indicative of a lack of de novo synthesis. Throughout clinical progression to AIDS, sCD8 antigen levels continued to escalate relative to the numbers of CD8+ cells bearing CD38+ antigen. The data confirm the interrelationship between sCD8+ antigen and CD8+ and CD8+ CD38+ cells.