Decreased helper T lymphocytes in homosexual men. I. Sexual contact in high-incidence areas for the acquired immunodeficiency syndrome

Impact of HLA class I functional divergence on HIV control

Heterozygosity of Human leukocyte antigen (HLA) class I genes is linked to beneficial outcomes after HIV infection, presumably through greater breadth of HIV epitope presentation and cytotoxic T cell response. Distinct allotype pairs, however, differ in the extent to which they bind shared sets of peptides. We developed a functional divergence metric that measures pairwise complementarity of allotype-associated peptide binding profiles. Greater functional divergence for pairs of HLA-A and/or HLA-B allotypes was associated with slower AIDS progression and independently with enhanced viral load control. The metric predicts immune breadth at the peptide level rather than gene level and redefines HLA heterozygosity as a continuum differentially affecting disease outcome. Functional divergence may affect response to additional infections, vaccination, immunotherapy, and other diseases where HLA heterozygote advantage occurs.

Inhibitory killer cell immunoglobulin-like receptors strengthen CD8+ T cell-mediated control of HIV-1, HCV, and HTLV-1

Killer cell immunoglobulin-like receptors (KIRs) are expressed predominantly on natural killer cells, where they play a key role in the regulation of innate immune responses. Recent studies show that inhibitory KIRs can also affect adaptive T cell-mediated immunity. In mice and in human T cells in vitro, inhibitory KIR ligation enhanced CD8+ T cell survival. To investigate the clinical relevance of these observations, we conducted an extensive immunogenetic analysis of multiple independent cohorts of HIV-1-, hepatitis C virus (HCV)-, and human T cell leukemia virus type 1 (HTLV-1)-infected individuals in conjunction with in vitro assays of T cell survival, analysis of ex vivo KIR expression, and mathematical modeling of host-virus dynamics. Our data suggest that functional engagement of inhibitory KIRs enhances the CD8+ T cell response against HIV-1, HCV, and HTLV-1 and is a significant determinant of clinical outcome in all three viral infections.

Elevated HLA-A expression impairs HIV control through inhibition of NKG2A-expressing cells

The highly polymorphic human leukocyte antigen (HLA) locus encodes cell surface proteins that are critical for immunity. HLA-A expression levels vary in an allele-dependent manner, diversifying allele-specific effects beyond peptide-binding preference. Analysis of 9763 HIV-infected individuals from 21 cohorts shows that higher HLA-A levels confer poorer control of HIV. Elevated HLA-A expression provides enhanced levels of an HLA-A–derived signal peptide that specifically binds and determines expression levels of HLA-E, the ligand for the inhibitory NKG2A natural killer (NK) cell receptor. HLA-B haplotypes that favor NKG2A-mediated NK cell licensing (i.e., education) exacerbate the deleterious effect of high HLA-A on HIV control, consistent with NKG2A-mediated inhibition impairing NK cell clearance of HIV-infected targets. Therapeutic blockade of HLA-E:NKG2A interaction may yield benefit in HIV disease.

Distinct assembly profiles of HLA-B molecules

MHC class I polymorphisms are known to influence outcomes in a number of infectious diseases, cancers, and inflammatory diseases. Human MHC class I H chains are encoded by the HLA-A, HLA-B, and HLA-C genes. These genes are highly polymorphic, with the HLA-B locus being the most variable. Each HLA class I protein binds to a distinct set of peptide Ags, which are presented to CD8(+) T cells. HLA-disease associations have been shown in some cases to link to the peptide-binding characteristics of individual HLA class I molecules. In this study, we show that polymorphisms at the HLA-B locus profoundly influence the assembly characteristics of HLA-B molecules and the stabilities of their peptide-deficient forms. In particular, dependence on the assembly factor tapasin is highly variable, with frequent occurrence of strongly tapasin-dependent or independent allotypes. Several polymorphic HLA-B residues located near the C-terminal end of the peptide are key determinants of tapasin-independent assembly. In vitro refolded forms of tapasin-independent allotypes assemble more readily with peptides compared to tapasin-dependent allotypes that belong to the same supertype, and, during refolding, reduced aggregation of tapasin-independent allotypes is observed. Paradoxically, in HIV-infected individuals, greater tapasin-independent HLA-B assembly confers more rapid progression to death, consistent with previous findings that some HLA-B allotypes shown to be tapasin independent are associated with rapid progression to multiple AIDS outcomes. Together, these findings demonstrate significant variations in the assembly of HLA-B molecules and indicate influences of HLA-B-folding patterns upon infectious disease outcomes.

Influence of HLA-C expression level on HIV control

A variant upstream of human leukocyte antigen C (HLA-C) shows the most significant genome-wide effect on HIV control in European Americans and is also associated with the level of HLA-C expression. We characterized the differential cell surface expression levels of all common HLA-C allotypes and tested directly for effects of HLA-C expression on outcomes of HIV infection in 5243 individuals. Increasing HLA-C expression was associated with protection against multiple outcomes independently of individual HLA allelic effects in both African and European Americans, regardless of their distinct HLA-C frequencies and linkage relationships with HLA-B and HLA-A. Higher HLA-C expression was correlated with increased likelihood of cytotoxic T lymphocyte responses and frequency of viral escape mutation. In contrast, high HLA-C expression had a deleterious effect in Crohn's disease, suggesting a broader influence of HLA expression levels in human disease.

Cohort- and time-specific associations of CTLA4 genotypes with HIV-1 disease progression

BACKGROUND

CTLA4 in the chromosome 2q33 region encodes cytotoxic T-lymphocyte (CTL) associated antigen 4, which downregulates CTL responses. We examined the relationships between common CTLA4 variants and several outcomes of HIV-1 infection in adults and adolescents.

METHODS

We studied 765 HIV-1-infected persons: 558 Caucasian seroconverters from three cohorts (MACS, ACS, and DCG) and 207 infected adolescents (mostly female) from another cohort (REACH) of mixed ethnicity. Single nucleotide polymorphisms in CTLA4 promoter (-1147C/T, -658C/T, -318C/T), coding sequence (49A/G) and the 3' untranslated region (CT60A/G) were resolved by PCR-based techniques. Repeated measures and survival analyses were used to test allelic and haplotypic associations with HIV-1 viral load (VL) and time to AIDS, respectively.

RESULTS

Individuals carrying -318T or the (-1147) T-(-318) T haplotype had elevated HIV-1 VL in MACS and REACH but reduced VL in DCG and ACS participants. Time-dependent associations of CTLA4-318T with VL were observed in MACS and REACH (P = 0.03-0.09). In Cox regression models adjusted for age and established contributory markers in CCR5 and HLA class I genes, CTLA4-318T was associated with rapid progression to AIDS in MACS (relative hazard 1.69; 95% confidence interval, 1.15-2.49; P < 0.01) as opposed to a non-significant slower disease progression in ACS and no appreciable association in DCG.

CONCLUSIONS

Association of CTLA4 genotypes with clinical and virological outcomes following HIV-1 infection appeared to vary with time and among the cohorts. Further analyses in conjunction with other biologically and positionally related genes, such as CD28 and ICOS, may help explain the disparate findings.

Human genes that limit AIDS

Discernable genetic variation among people and populations has an important role in infectious disease epidemics, including that of acquired immune deficiency syndrome (AIDS). Genetic association analysis of several large AIDS cohorts implicate 14 AIDS restriction genes, polymorphic variants in loci that regulate HIV-1 cell entry, acquired and innate immunity, and cytokine defenses to HIV-1. The influence and translational impact of these genes on individual and population sensitivity to AIDS is considerable.

Polygenic and multifactorial disease gene association in man: Lessons from AIDS

In an age when the majority of monogenic human disease genes have been identified, a particular challenge for the coming generation of human geneticists will be resolving complex polygenic and multifactorial diseases. The tools of molecular and population genetic association have much potential as well as peril in uncovering small cryptic genetic effects in disease. We have used a candidate gene approach to identify eight distinct human loci with alleles that in different ways influence the outcome of exposure to HIV-1, the AIDS virus. The successes in these gene hunts have validated the approach and illustrate the strengths and limitations of association analysis in an actual case history. The integration of genetic associations, well-described clinical cohorts, extensive basic research on AIDS pathogenesis, and functional interpretation of gene connections to disease offers a formula for detecting such genes in complex human genetic phenotypes.

A phase II study of two HIV type 1 envelope vaccines, comparing their immunogenicity in populations at risk for acquiring HIV type 1 infection. AIDS Vaccine Evaluation Group

Several immunogens induce HIV-specific neutralization and in vitro lymphoproliferation in adults at low HIV-1 risk, but responses in persons at high HIV-1 risk are not known. We performed a multicenter, double-blinded, adjuvant-controlled trial with two gp120 vaccines in 296 HIV-1-uninfected volunteers, including 176 reporting higher HIV-1 risk activities. The immunogens were remarkably well tolerated. After three immunizations, 210 of 241 vaccinees (87%) developed neutralizing antibodies, which persisted in 59% after 2 years. The injection drug users receiving SF-2/gp120 had decreased antibody responses relative to the lower risk groups. Envelope-specific lymphoproliferation peaked after two immunizations, and 54% of vaccinees mounted a DTH reaction to gp120 after 4 years. In summary, these immunogens have low adverse reactogenicity and induce durable antibody and T cell responses to the prototype strains. Unexpected differences in antibody responses among diverse HIV-1 risk strata lend support to the conduct of expanded phase II trials in populations other than low-risk volunteers.

Comparison of viral load and human leukocyte antigen statistical and neural network predictive models for the rate of HIV-1 disease progression across two cohorts of homosexual men

We compared the performance of HIV-1 RNA and models based on human leukocyte antigen (HLA) in predicting the rate of HIV-1 disease progression using both linear regression and neural network models across two different cohorts of homosexual men. In all, 139 seroconverters from the Multicenter AIDS Cohort Study were used as the training set and 97 seroconverters from the District of Columbia Gay (DCG) cohort were used for validation to assess the generalizability of trained predictive models. Both viral load and HLA markers were strongly predictive of disease progression (p < .0001 and p = .001, respectively), with viral load superior to HLA (change in -2 log likelihood [-2LL] 26.7 and 10.2, respectively, in proportional hazards models). Consideration of both HLA markers and viral load offered no significant predictive advantage over viral load alone in most cases; however, HLA-based predictions obtained from neural networks modeling improved the discrimination among patients with high viral load (p = .02). Viral load, HLA scores, and rapid disease progression were moderately correlated (p < .01 for all three pairs of these variables). The median viral load was 10(3.70) copies/ml among DCG patients who had more favorable than unfavorable HLA markers and 10(4.66) copies/ml among patients with more unfavorable than favorable HLA markers. Viral load is a simpler, stronger predictor of disease progression than early developed HLA models, but neural network methods and further refined HLA models may offer additional prognostic information, especially for rapid progressors. The correlation between viral load and HLA markers suggests a possible HLA effect on setting viral load levels.

Genetic restriction of HIV-1 infection and progression to AIDS by a deletion allele of the CKR5 structural gene. Hemophilia Growth and Development Study, Multicenter AIDS Cohort Study, Multicenter Hemophilia Cohort Study, San Francisco City Cohort, ALIVE Study

The chemokine receptor 5 (CKR5) protein serves as a secondary receptor on CD4(+) T lymphocytes for certain strains of human immunodeficiency virus-type 1 (HIV-1). The CKR5 structural gene was mapped to human chromosome 3p21, and a 32-base pair deletion allele (CKR5Delta32) was identified that is present at a frequency of approximately0.10 in the Caucasian population of the United States. An examination of 1955 patients included among six well-characterized acquired immunodeficiency syndrome (AIDS) cohort studies revealed that 17 deletion homozygotes occurred exclusively among 612 exposed HIV-1 antibody-negative individuals (2.8 percent) and not at all in 1343 HIV-1-infected individuals. The frequency of CKR5 deletion heterozygotes was significantly elevated in groups of individuals that had survived HIV-1 infection for more than 10 years, and, in some risk groups, twice as frequent as their occurrence in rapid progressors to AIDS. Survival analysis clearly shows that disease progression is slower in CKR5 deletion heterozygotes than in individuals homozygous for the normal CKR5 gene. The CKR5Delta32 deletion may act as a recessive restriction gene against HIV-1 infection and may exert a dominant phenotype of delaying progression to AIDS among infected individuals.

Influence of combinations of human major histocompatibility complex genes on the course of HIV-1 infection

Major histocompatibility complex (MHC) genes (HLA in humans) regulate the immune response to foreign antigens. Molecular and serologic techniques were used to identify products of HLA class I, class II and transporter (TAP) genes (also part of the MHC) in homosexual seroconverters to human immunodeficiency virus type 1 (HIV-1). Comprehensive statistical analysis produced an HLA profile that predicted time from HIV-1 infection to the onset of AIDS. The profile was developed in a cohort of 139 men and evaluated in a second unrelated cohort of 102 men. In the evaluation cohort, the profile discriminated a sixfold difference between groups with the shortest and longest times to AIDS (P = 0.001). These findings support current theory about control of antigen processing by HLA genes and have implications for immunopathogenesis of HIV-1 and other infections.

Contribution of cohort studies in understanding HIV pathogenesis: introduction of the GRIV cohort and preliminary results

In the present paper we review studies performed on HIV-infected patients cohorts in order to understand AIDS disease development. The interplay between diverse factors such as the HIV envelope proteins, cellular co-receptors, the immune response with chemokines and cytokines production define the viral tropism, cytopathicity and progression of HIV disease. We present the trends of the research particularly in the domain concerning host genetics. In this context, we describe the GRIV cohort of fast and slow/non-progressors, and its use for understanding basic features of the yet unknown HIV pathogenesis mechanisms.

Dave Byar's contribution to epidemiology

Some of Dave Byar's personal qualities and his scientific approach are described. His work on substantive epidemiologic projects is mentioned briefly. There follows a review of his work on theoretical issues, including extentions of the Mantel-Haenszel procedure and other contingency table methods, confounding, and estimation of attributable and absolute risk from case-control data.

Prognostic markers for AIDS

Human immunodeficiency virus (HIV) infection causes a number of clinical syndromes and many laboratory abnormalities, often heralding the development of the life-threatening opportunistic infections or malignancies that are known as the acquired immunodeficiency syndrome (AIDS). Drawing heavily on the results of prospective cohort studies, particularly those that my colleagues at the National Cancer Institute and I have conducted, this paper reviews the relationship of AIDS to clinical signs and symptoms, immunologic measures, and viral assays. The risk of AIDS in the next 3 years is at least 25 to 50% for HIV-infected subjects who have oral candidiasis, unexplained fever, unexplained weight loss, a CD4+ lymphocyte count below 200 cells/microliter, or combinations of these. Elevated serum levels of beta 2 microglobulin and neopterin also appear to be strong predictive markers of AIDS, but further work is needed in diverse HIV-infected populations, such as intravenous drug users and persons in pattern II countries, such as Haiti and central Africa. Elevated levels of interferon or HIV-p24 antigen in the serum are insensitive but highly specific AIDS markers that may have predictive value independent of CD4 lymphocyte levels. Several potentially valuable immunologic (immunoglobulin levels, tumor necrosis factor, soluble interleukin 2) and virologic (HIV viremia) assays remain to be thoroughly evaluated or technically simplified. Data from prospective cohort studies have provided clinical and laboratory markers of AIDS risk that have proved essential for therapeutic trials and other clinical decisions. As effective treatments for HIV infection and its complications begin to emerge, these marker data will also prove invaluable for mathematic modeling of the scope, course, and public health response to the epidemic.

Interaction of human immunodeficiency and papilloma viruses: association with anal epithelial abnormality in homosexual men

During the 7th annual follow-up of our cohort of homosexual men in 1989, we tested the hypotheses that infection with human immunodeficiency virus (HIV) may enhance the expression of human papilloma virus (HPV) and that the development of anal epithelial abnormality is related to a biologic interaction between these two viruses. Overall, 41 (39%) of the 105 men had anal swabs positive for one or more genotypes of HPV 6/11, 16/18 or 31/33/35. Twenty-three (53%) of the 43 HIV-positive subjects harbored HPV compared to 18 (29%) of the 64 HIV-negative subjects (p = 0.012), including higher prevalence rates for HPV genotypes 16/18 (p = 0.01), 6/11 (p = 0.007), and 31/33/35 (p = 0.07). Multivariate logistic regression analysis of the HIV-positive subjects showed low CD4+ cell counts to be an independent risk factor for detection of HPV (p = 0.04) and in particular for HPV genotypes 31/33/35 (p = 0.02) and 6/11 (p = 0.07). In contrast, similar analysis of the HIV-negative subset showed that a positive antibody test for syphilis was associated with HPV (p = 0.03). Anal epithelial abnormalities were found in 13 (14%) of 92 technically adequate cytologic smears and were strongly associated with detection of any HPV genotypes by the dot-blot method (p = 0.01), and in particular with HPV genotypes 6/11 (p = 0.001). None of 15 subjects with HPV detected only by PCR had anal epithelial abnormality. We propose a viral interaction model, in which HIV-related immune deficiency allows reactivation of HPV, with a subsequent or concomitant appearance of epithelial abnormality.

Urinary neopterin concentrations and T-cell subset data in HIV-1 infection

We investigated the ability of urinary neopterin concentrations and T-cell subset data, and their ratios to discriminate between anti-HIV-1 seronegatives, seropositives, and AIDS cases. Using receiver-operated-characteristics curves, neopterin levels were shown to provide the best discrimination. Of the ratios derived from the single variables, neopterin per CD4+ cell counts and neopterin per CD4+/CD8+ cell ratio were superior to the CD4+/CD8+ cell ratio. Multivariate analyses were performed using a generalized likelihood ratio approach as well as linear discriminant analysis. The combination of neopterin concentration and CD4+ T-cell count is well suited to discriminate between various stages of HIV-1 infection and, therefore, we recommend using more than one assay to evaluate disease progression.

What is safe sex? Suggested standards linked to testing for human immunodeficiency virus

Because of the lethality of the HIV epidemic, rational and scientifically defined standards of sex that preclude the spread of sexually transmitted diseases are required. In the context of an HIV-antibody test that has been documented to be extremely sensitive and specific, standards for truly safe sex can be defined. HIV testing can be used as a powerful tool for defining a series of standards for sexual partners that eliminates, with reasonable certainty, the further spread of HIV. Such standards provide a defined benchmark for future research aimed at evaluating the effectiveness of public health measures in arresting the spread of the virus. The fact that at least 10 million American blood donors and some 2 million Americans applying for or in the armed forces have been tested demonstrates that the adverse consequences of testing can be limited. Now is the time to minimize the fear and eliminate the risk of transmitting HIV to loved ones by urging widespread voluntary testing of sexually active adults and by developing standards for safe sex.

The impact of AIDS on gay male sexual behavior patterns in New York City

A sample of 745 gay men, ages 20 to 65, were interviewed in 1985 as part of an effort to determine the impact of the AIDS (acquired immunodeficiency syndrome) epidemic on the non-ill but at-risk community. Measured in terms of the number of different sexual partners, sexual activity was reported to have declined by 78 per cent since hearing about AIDS. The frequency of sexual episodes involving the exchange of body fluids and mucous membrane contact declined by 70 per cent, and condom use during anal intercourse increased from 1.5 to 20 per cent. Abstinence from gay sex did not change over time.

Antiviral antibodies in the sera of homosexual men: correlation with their lifestyle and drug usage

Healthy homosexual men between the ages of 21 and 65 years, from the Washington, DC (n = 162), and New York City (n = 89) areas, were studied for antibodies in the serum against cytomegalovirus (CMV), herpes simplex virus (HSV) types 1 and 2, and Epstein Barr virus (EBV) viral capsid antigen (VCA). CMV-specific antibodies were assayed by enzyme-linked immunosorbent assay (ELISA), anti-HSV-1 and -2 antibodies were measured by indirect hemagglutination (IHA), and antibodies to EBV VCA were measured by the immunofluorescence assay. Antibodies to human T lymphotrophic virus III (HTLV-III) were detected by ELISA and Western blot procedures. T lymphocytes were enumerated using OKT4 monoclonal antibody. Healthy male volunteer blood donors (n = 90) matched for age range and race proportions were used as controls. The percentage of seropositive individuals in the homosexual group was higher (90-98%) for all the viruses tested than in the control group (47-87%). Comparisons of the geometric mean titers, expressed as reciprocal serum dilutions, of seropositive individuals in homosexual (H) vs control (C) group were as follows: CMV-IgG (ELISA) H = 1:794, C = 1:68; HSV-1 (IHA) H = 1:248, C = 1:14; HSV-2 (IHA) H = 1:56, C = 1:17; EBV-VCA (IFA) H = 1:385, C = 1:131. The homosexual group also showed a higher frequency of individuals with elevated titers than the control group. The CMV IgM antibody was prevalent in 17.7% of the homosexual group and 5% of the control group; arithmetic means for ELISA values for CMV IgM were 0.207 for the homosexual group and 0.05 for the control group. In the homosexual group, the anti-CMV antibody titers increased with age (P = 0.01) and with numbers of sex partners (P = 0.06). Both anti-HSV-1 and anti-HSV-2 antibodies correlated with the number of sex partners (P = 0.04 and P = 0.05, respectively). Neither age nor partner number correlated with response to EBV, and no particular sex act was related to the EBV VCA titer level. HTLV-III seropositivity was associated with higher herpes virus group antibody titers, probably because of life style cofactors. Among the HTLV-III-seropositive subjects, those with less than or equal to 400 T-helper lymphocytes/mm3 had lower antibody titers than those with greater than 400 T-helper lymphocytes/mm3 counts, suggesting an impaired immune response secondary to immunosuppression.

Three-year incidence of AIDS in five cohorts of HTLV-III-infected risk group members

The incidence of the acquired immune deficiency syndrome (AIDS) among persons infected with human T-lymphotropic virus type III (HTLV-III) was evaluated prospectively among 725 persons who were at high risk of AIDS and had enrolled before October 1982 in cohort studies of homosexual men, parenteral drug users, and hemophiliacs. A total of 276 (38.1 percent) of the subjects were either HTLV-III seropositive at enrollment or developed HTLV-III antibodies subsequently. AIDS had developed in 28 (10.1 percent) of the seropositive subjects before August 1985. By actuarial survival calculations, the 3-year incidence of AIDS among all HTLV-III seropositive subjects was 34.2 percent in the cohort of homosexual men in Manhattan, New York, and 14.9 percent (range 8.0 to 17.2 percent) in the four other cohorts. Out of 117 subjects followed for a mean of 31 months after documented seroconversion, five (all hemophiliacs) developed AIDS 28 to 62 months after the estimated date of seroconversion, supporting the hypothesis that there is a long latency between acquisition of viral infection and the development of clinical AIDS. This long latency could account for the significantly higher AIDS incidence in the New York cohort compared with other cohorts if the virus entered the New York homosexual population before it entered the populations from which the other cohorts were drawn. However, risk of AIDS development in different populations may also depend on the presence of as yet unidentified cofactors.

Determinants of retrovirus (HTLV-III) antibody and immunodeficiency conditions in homosexual men

A cohort of homosexual men at high risk of the acquired immunodeficiency syndrome (AIDS) was monitored to examine the relation between lifestyle, clinical conditions, T-lymphocyte subsets, and antibody to the AIDS-associated human retrovirus, human T-cell leukaemia virus III (HTLV-III). HTLV-III antibodies were present in 35 (53%) of the 66 subjects tested in June, 1982. 4 of the seronegative subjects had HTLV-III antibodies when re-tested one year later, a seroconversion rate of 1.2% per month. In the HTLV-III seropositive subjects, AIDS developed at a rate of 6.9% per year (minimum incidence of AIDS = 4.6% per year) and other clinical signs of immunodeficiency (lesser AIDS) at 13.1% per year. All 6 of the AIDS cases and at least 8 of the 10 lesser AIDS cases had detectable HTLV-III antibodies 1 week to 21 months before diagnosis. Of 24 other subjects with stable lymphadenopathy, 19 (79%) had or acquired HTLV-III antibodies. Lower helper T-cell counts were very closely related to HTLV-III seropositivity (r = -0.53, p = 0.0001), even in the 26 healthy subjects with no clinical abnormalities (r = -0.37, p = 0.07). In both univariate and multivariate analyses, the lifestyle risk factors for HTLV-III seropositivity were large number of homosexual partners (p less than or equal to 0.03) and receptive anal intercourse (p less than or equal to 0.03), with an apparent synergistic interaction between these two activities (chi 2 = 8.71, p = 0.003). These data suggest that frequent receptive anal intercourse with many homosexual partners predisposes to HTLV-III infection with the consequent emergence of lymphadenopathy and the various manifestations of lesser and fully fledged AIDS.