Vaccine-induced antibodies to the native, oligomeric envelope glycoproteins of primary HIV-1 isolates

A simple and sensitive method for measuring antibodies to primary human immunodeficiency virus type 1 (HIV-1) isolates has been developed. The flow cytometric immuno-fluorescence assay detects antibodies that bind to the native, oligomeric form of the envelope glycoprotein (gp120) expressed on the surface of PM-1 cells infected with primary isolates of HIV-1. Sera from people infected with HIV-1 or those immunized with recombinant gp120 vaccines were tested. Significant correlation was observed between neutralizing activity and oligomeric gp120 binding activity. Thirteen to 100% of individuals immunized with the subtype B bivalent vaccine AIDSVAX B/B developed oligomeric gp120 binding antibodies against a variety of subtype B primary isolates. For several isolates, AIDSVAX B/B sera reacted better than monovalent AIDSVAX B sera, suggesting that addition of the second immunogen improved the breadth of the antibody response. Cross-subtype binding activities, induced by AIDSVAX B/B, were lower than activities to subtype B isolates, suggesting that additional immunogen(s) may be desirable in vaccine(s) formulated for geographic regions where non-B subtypes are dominant.

Effects of CCR5-Delta32, CCR2-64I, and SDF-1 3'A alleles on HIV-1 disease progression: An international meta-analysis of individual-patient data

BACKGROUND

Studies relating certain chemokine and chemokine receptor gene alleles with the outcome of HIV-1 infection have yielded inconsistent results.

OBJECTIVE

To examine postulated associations of genetic alleles with HIV-1 disease progression.

DESIGN

Meta-analysis of individual-patient data.

SETTING

19 prospective cohort studies and case-control studies from the United States, Europe, and Australia.

PATIENTS

Patients with HIV-1 infection who were of European or African descent.

MEASUREMENTS

Time to AIDS, death, and death after AIDS and HIV-1 RNA level at study entry or soon after seroconversion. Data were combined with fixed-effects and random-effects models.

RESULTS

Both the CCR5-Delta32 and CCR2-64I alleles were associated with a decreased risk for progression to AIDS (relative hazard among seroconverters, 0.74 and 0.76, respectively; P = 0.01 for both), a decreased risk for death (relative hazard among seroconverters, 0.64 and 0.74; P < 0.05 for both), and lower HIV-1 RNA levels after seroconversion (difference, -0.18 log(10) copies/mL and -0.14 log(10) copies/mL; P < 0.05 for both). Having the CCR5-Delta32 or CCR2-64I allele had no clear protective effect on the risk for death after development of AIDS. The results were consistent between seroconverters and seroprevalent patients. In contrast, SDF-1 3'A homozygotes showed no decreased risk for AIDS (relative hazard for seroconverters and seroprevalent patients, 0.99 and 1.03, respectively), death (relative hazard, 0.97 and 1.00), or death after development of AIDS (relative hazard, 0.81 and 0.97; P > 0.5 for all).

CONCLUSIONS

The CCR5-Delta32 and CCR2-64I alleles had a strong protective effect on progression of HIV-1 infection, but SDF-1 3'A homozygosity carried no such protection.

Homozygous and heterozygous CCR5-Delta32 genotypes are associated with resistance to HIV infection

OBJECTIVE

To investigate evidence for resistance to HIV-1 infection associated with the heterozygous genotype CCR5-+/Delta32 and with the homozygous genotype CCR5-Delta32/Delta32, which results in a nonfunctional CCR5 receptor.

DESIGN

Cohort study of initially HIV-seronegative high-risk individuals from eight different cities. Enrollment data were analyzed to investigate the association of demographic factors and risk behaviors with CCR5 genotypes on the assumption that increased genotype prevalence among persons with histories of longer or more intensive exposure to HIV would indicate HIV resistance associated with that genotype. Longitudinal data were analyzed to investigate the association of HIV seroincidence with CCR5 genotypes. The cohort of 2996 individuals included 1892 men who have sex with men (MSM), 474 male injection drug users (IDUs), 347 women at heterosexual risk, and 283 female IDUs.

MEASUREMENTS

CCR5 genotype, HIV serostatus, demographic factors, and risk behaviors during the 6 months before enrollment, followed by measurement of HIV seroincidence during the subsequent 18 months (for men) and 24 months (for women).

RESULTS

Forty (1.3%) subjects were homozygous CCR5-Delta32/Delta32 and 387 (12.9%) were heterozygous CCR5-+/Delta32. All but 1 CCR5-Delta32/Delta32 individuals and 51 CCR5-+/Delta32 individuals were Caucasian. Among 1531 Caucasian MSM, CCR5-+/Delta32 individuals were present more frequently (22.3%) among those reporting unprotected receptive anal intercourse than among those not reporting this risk (15.9%) (p =.002), suggesting a selective advantage of the heterozygous genotype. CCR5-+/Delta32 individuals also had a significantly reduced relative risk of HIV seroconversion adjusted for unprotected receptive anal intercourse compared with CCR5-/+ individuals (relative risk = 0.30, 95% confidence interval [CI]: 0.08-0.97). CCR5-Delta32/Delta32 prevalence among Caucasian MSM was significantly associated with age among subjects recruited from high HIV seroprevalence cities (New York City and San Francisco) (odds ratio [OR] for each decade increase in age = 2.57, CI: 1.56-4.21) but not among those recruited from lower HIV prevalence sites (Boston, Chicago, Philadelphia, Seattle, and Providence/Pawtucket, Rhode Island) (OR = 1.20, CI: 0.75-1.89).

CONCLUSIONS

Cross-sectional and longitudinal analyses indicated that among high-risk HIV seronegative MSM, CCR5-+/Delta32 and CCR5-Delta32/Delta32 are associated with protection against HIV infection. These findings imply that strategies aimed at reducing susceptibility to HIV infection by blocking CCR5 receptor sites need not seek blockage of all receptor sites to achieve an imperfect but substantial degree of protection.

Early human immunodeficiency virus (HIV) infection in the HIV Network for Prevention Trials Vaccine Preparedness Cohort: risk behaviors, symptoms, and early plasma and genital tract virus load

Risk behaviors, symptoms, and virologic characteristics were studied among 103 human immunodeficiency virus (HIV) seroconverters in vaccine preparedness cohorts during 1995-1998. Overall, 83% of subjects were men who had sex with men; most reported multiple risk episodes and symptoms (84%, > or =1 symptom) during seroconversion. Acute HIV was diagnosed in only 8 of 50 who sought medical care. Median initial pretreatment plasma virus load was 25,800 copies/mL (range, undetectable-262,000 copies/mL) a mean of 4 months after seroconversion, and 9.7% had nucleoside-associated mutations; none had multidrug resistance. Semen virus load was more variable, 1.3 log(10) lower and modestly correlated (r=.28; 95% confidence interval, 0.16-0.42) with plasma among untreated men. When the plasma RNA level was <5000 copies/mL, 32% of untreated men, 13% on nucleoside regimens, and 7% on protease inhibitor-containing regimens had detectable seminal RNA. Acute HIV was seldom diagnosed, representing missed opportunities for early treatment and prevention. Most subjects had several relatively stable virus loads before initiation of antiretrovirals, indicating feasibility of assessing HIV vaccines on virus set point in efficacy trials.

Shorter survival of SDF1-3'A/3'A homozygotes linked to CD4+ T cell decrease in advanced human immunodeficiency virus type 1 infection

The SDF-1 3'A allelic polymorphism has been reported to influence either positively or negatively the progression of human immunodeficiency virus type 1 (HIV-1) disease. Therefore, the SDF-1 genotype of 729 HIV-1-infected individuals pooled from 3 distinct cohorts was determined. A statistically nonsignificant association between the SDF1-3'A/3'A genotype and accelerated disease progression was evident among seroconverters (n=319), but a striking correlation of decreased survival after either diagnosis of AIDS according to the 1993 definition or loss of CD4(+) T cell counts <200 was observed. The relative hazards for SDF1-3'A/3'A homozygotes, compared with heterozygotes and wild-type homozygotes were 2.16 (P=.0047), for time from diagnosis according to the 1993 Centers for Disease Control and Prevention AIDS case definition (AIDS-'93) to death, and 3.43 (P=.0001), for time from CD4(+) T cells <200 to death. Because no difference in survival was observed after diagnosis according to AIDS-'87, the association of the SDF1-3'A/3'A genotype with the accelerated progression of late-stage HIV-1 disease appears to be explained for the most part by the loss of CD4(+) T lymphocytes.

Identification of a high-risk heterosexual population for HIV prevention trials in Rio de Janeiro, Brazil. Projeto Praço Onze Study Group

The study of interventions to prevent HIV transmission requires access to populations with a high rate of HIV transmission. We estimated HIV incidence among heterosexual males and females who were seen at an HIV testing site in Rio de Janeiro, Brazil. Stored sera from individuals who visited the site between March and December 1998 were analyzed using the sensitive/less sensitive (S/LS) assay and a chart abstraction was performed. During the study period, 6353 serum samples were tested. Of those tested, 1203 were found to be HIV-seropositive or indeterminate, of which 1050 (87%) remained available for further testing. In addition, 84 serum samples, representing 63 adults, were found to produce results suggesting early HIV infection. Of these, 14 were heterosexual and female (median age, 38 years), and 19 were heterosexual and male (median age, 25 years). The estimated HIV seroincidence was 1.9 (95% confidence limits (CL), 0.9%-3.9%) and 2.8 (95% CL, 1.4%-5.3%) per 100 person-years among heterosexual women and men, respectively. A survey on willingness to participate in future placebo-controlled HIV vaccine trials in this population indicated that 54.5% and 53.9% of heterosexual women and men, respectively, indicated that they would definitely be willing to participate. We have identified a heterosexual population in Rio de Janeiro with a high rate of HIV transmission willing to participate in placebo-controlled vaccine trials. This study demonstrates the usefulness of the newly described S/LS assay, which allows one to estimate HIV incidence from single serum specimens.

Dissociation of immunologic and virologic responses to highly active antiretroviral therapy

OBJECTIVE

Immunologic markers, levels of HIV DNA, and infectious HIV were compared in partial responders (PR) to HAART who had high plasma HIV RNA levels but stable or increasing levels of CD4+ peripheral blood mononuclear cells (PBMC), and patients with complete failure (CF) who had very low or decreasing levels of CD4+ PBMC and high plasma HIV RNA levels.

DESIGN AND METHODS

CD4 and CD8 levels were monitored by flow cytometry. Beta2-microglobulin (beta2M) and neopterin levels were measured by quantitative enzyme immunoassays. Plasma and PBMC from 11 PR and 13 CF were analyzed for infectious HIV levels in limiting dilution cultures. Polymerase chain reaction (PCR) assays were used to quantify cellular HIV DNA and plasma HIV RNA.

RESULTS

In comparison with CF, PR had little or no CD4+ cell loss, a substantial increase in CD8+ cells, significantly fewer positive plasma HIV cultures (p = .03), lower frequencies of infectious HIV in total PBMC (p = .005) and in CD4+ PBMC (p < .001), and lower frequencies of HIV DNA in CD4+ PBMC (p = .007).

CONCLUSIONS

Lower levels of infectious HIV and a lower frequency of CD4+ PBMC that contain "productive" HIV DNA in PR as compared with CF may contribute to the stable or increasing CD4+ PBMC levels of the PR. However, HAART may also have effects on lymphocyte homeostasis independent of its antiviral activity.

Full-length human immunodeficiency virus type 1 genomes from subtype C-infected seroconverters in India, with evidence of intersubtype recombination

The development of an effective human immunodeficiency virus type 1 (HIV-1) vaccine is likely to depend on knowledge of circulating variants of genes other than the commonly sequenced gag and env genes. In addition, full-genome data are particularly limited for HIV-1 subtype C, currently the most commonly transmitted subtype in India and worldwide. Likewise, little is known about sequence variation of HIV-1 in India, the country facing the largest burden of HIV worldwide. Therefore, the objective of this study was to clone and characterize the complete genome of HIV-1 from seroconverters infected with subtype C variants in India. Cocultured HIV-1 isolates were obtained from six seroincident individuals from Pune, India, and virtually full-length HIV-1 genomes were amplified, cloned, and sequenced from each. Sequence analysis revealed that five of the six genomes were of subtype C, while one was a mosaic of subtypes A and C, with multiple breakpoints in env, nef, and the 3' long terminal repeat as determined by both maximal chi2 analysis and phylogenetic bootstrapping. Sequences were compared for preservation of known cytotoxic T lymphocyte (CTL) epitopes. Compared with those of the HIV-1LAI sequence, 38% of well-defined CTL epitopes were identical. The proportion of nonconservative substitutions for Env, at 61%, was higher (P < 0.001) than those for Gag (24%), Pol (18%), and Nef (32%). Therefore, characterized CTL epitopes demonstrated substantial differences from subtype B laboratory strains, which were most pronounced in Env. Because these clones were obtained from Indian seroconverters, they are likely to facilitate vaccine-related efforts in India by providing potential antigens for vaccine candidates as well as for assays of vaccine responsiveness.

Full-length human immunodeficiency virus type 1 genomes from subtype C-infected seroconverters in India, with evidence of intersubtype recombination

The development of an effective human immunodeficiency virus type 1 (HIV-1) vaccine is likely to depend on knowledge of circulating variants of genes other than the commonly sequenced gag and env genes. In addition, full-genome data are particularly limited for HIV-1 subtype C, currently the most commonly transmitted subtype in India and worldwide. Likewise, little is known about sequence variation of HIV-1 in India, the country facing the largest burden of HIV worldwide. Therefore, the objective of this study was to clone and characterize the complete genome of HIV-1 from seroconverters infected with subtype C variants in India. Cocultured HIV-1 isolates were obtained from six seroincident individuals from Pune, India, and virtually full-length HIV-1 genomes were amplified, cloned, and sequenced from each. Sequence analysis revealed that five of the six genomes were of subtype C, while one was a mosaic of subtypes A and C, with multiple breakpoints in env, nef, and the 3' long terminal repeat as determined by both maximal chi2 analysis and phylogenetic bootstrapping. Sequences were compared for preservation of known cytotoxic T lymphocyte (CTL) epitopes. Compared with those of the HIV-1LAI sequence, 38% of well-defined CTL epitopes were identical. The proportion of nonconservative substitutions for Env, at 61%, was higher (P < 0.001) than those for Gag (24%), Pol (18%), and Nef (32%). Therefore, characterized CTL epitopes demonstrated substantial differences from subtype B laboratory strains, which were most pronounced in Env. Because these clones were obtained from Indian seroconverters, they are likely to facilitate vaccine-related efforts in India by providing potential antigens for vaccine candidates as well as for assays of vaccine responsiveness.

Correlation between humoral responses to human immunodeficiency virus type 1 envelope and disease progression in early-stage infection

Human immunodeficiency virus (HIV)-1-infected rapid and slow progressors showed differential humoral responses against HIV envelope peptides and proteins early in infection. Sera from slow progressors reacted more strongly with short envelope peptides modeling gp160NL4-3, predominantly in gp41. Reactivity to six peptides (in constant regions C3, C4, and C5 of gp120 and in gp41) correlated with slower progression. In a novel association, reactivity to three peptides (in constant regions C1 and C3 and variable region V3 of gp120) correlated with faster progression. Envelope peptide reactivity correlated with subsequent course of disease progression as strongly as did reactivity to gag p24. Patients heterozygous for 32-bp deletions in the CCR5 coreceptor reacted more frequently to an epitope in gp41. Rapid progressors had greater gp120 native-to-denatured binding ratios than did slow progressors. While antibody-dependent cellular cytotoxicity against gp120 did not strongly differentiate the groups, slow progressors showed a broader neutralization pattern against 5 primary virus isolates.

Cross-clade envelope glycoprotein 160-specific CD8+ cytotoxic T lymphocyte responses in early HIV type 1 clade B infection

A major objective of current HIV-1 vaccination strategies is the induction of HIV-1-specific CD8+ MHC class I-restricted CTL responses, which are suggested to play a pivotal role in viral clearance and protection against HIV-1 disease progression. However, the marked genetic diversity of HIV-1 and existence of distinct viral subtypes or clades could potentially hinder the development of a universally efficacious HIV-1 vaccine. In this study we examined HIV-1 intraclade (B(LAI) versus B(MN)) Env gp160-specific CTL reactivity in recently HIV-1 clade B-infected individuals. We further evaluated the extent of interclade CTL cross-recognition of the divergent A and C Env gp160 subtypes, that are highly prevalent in the global pandemic. Freshly isolated PBMCs were stimulated in vitro with autologous PBMCs infected with recombinant vaccinia vectors expressing HIV-1 env, gag, pol, and nef genes derived from HIV-1 clade B. All 13 of the 19 HIV-1-seropositive subjects who elicited significant clade B Env gp160LAI CD8+ CTL responses also demonstrated comparable levels of CTL cross-reactivity against clade C92BR025 Env gp160. Nine of these individuals also showed extensive interclade CTL cross-recognition of clade A92UG037 Env gp160. Two HLA class I B7 donors had nondetectable intraclade CTL response against B Env gp160MN, while generating significant intraclade B(LAI) and interclade (A and C) Env gp160 CTL cross-reactivity. These observations serve to underscore the central importance of the HLA background of individuals in determining the pattern of immune reactivity to natural HIV-1 infection and presumably vaccines. Five donors studied also demonstrated broad CTL cross-reactivity against clade A92UG037 Gag p55, Pol, and/or Nef antigens. In conclusion, this present study indicates that there is a considerable degree of CD8+ CTL cross-recognition of the highly divergent HIV-1 Env gp160 subtypes during early phases of HIV-1 infection. Such findings suggest that HIV-1 vaccines based on a single clade that can induce extensive cross-clade immunity may demonstrate utility in diverse geographical regions.

Direct HIV cytopathicity cannot account for CD4 decline in AIDS in the presence of homeostasis: a worst-case dynamic analysis

The central paradox of HIV pathogenesis is that the viral burden, either free or cellular, seems too low to deplete the CD4 population by direct killing. Until recently, little data could be used to compare direct and indirect pathogenic theories critically. Clinical trials with potent new antiviral agents have measured important kinetic parameters of HIV infection, including viral and infected cell half-lives. This has led to the construction of explicit models of direct killing. Using a worst-case dynamic analysis, we show that such cytopathic models are untenable. Rates of infected cell removal are orders of magnitude too low to suppress steady state CD4 counts significantly in the face of lymphocyte replenishment, especially in early infection. Furthermore, the direct cytopathic models, as proposed, predict an extremely variable disease course across the broad range of observed viral burdens (five orders of magnitude), which is inconsistent with the relatively small differences in disease progression observed between patients. In contrast, immunologic theories of pathogenesis, such as homeostatic dysregulation based on immune activation, do not suffer from these difficulties and are more consistent with the natural history of HIV infection.

Transmission of genetically diverse strains of HIV-1 in Pune, India

Surveillance of the different HIV-1 subtypes has important implications for developing candidate vaccines and understanding the dynamics of HIV transmission in various populations. In this study, HIV-1 viral subtypes were determined for homologies in the V3-V5 region by heteroduplex mobility assay (HMA) in 46 patients with sexually transmitted diseases (STD) in Pune, India. Proviral DNA from peripheral blood mononuclear cells (PBMCs) from 20 recent sero-coverters and 26 HIV seropositive individuals were analyzed. Of the 46 samples analyzed, 44 (96%) were HIV-1 subtype C and one each of subtypes A and B. Further analyses revealed that 29 (66%) of the C subtype samples had maximum homology to the C3-Indian reference strain, while 15 (34%) were most homologous to the C2-Zambian strain. The C3 genotype prevailed in the majority (80%) of the seropositive individuals. Most of the C3 (Indian) strains were closely homologous to each other, while more nucleotide sequence divergence was seen in C2 samples. A higher quasispecies complexity was observed in the samples collected from seropositive individuals. These findings may have important implications for the design and testing of effective candidate HIV-1 vaccines for India.

The role of CCR5 and CCR2 polymorphisms in HIV-1 transmission and disease progression

Entry of human immunodeficiency virus type 1 (HIV-1) into target cells requires both CD4 (ref. 1, 2) and one of a growing number of G-protein-coupled seven-transmembrane receptors. Viruses predominantly use one, or occasionally both, of the major co-receptors CCR5 or CXCR4, although other receptors, including CCR2B and CCR3, function as minor co-receptors. CCR3 appears critical in central nervous system infection. A 32-base pair inactivating deletion in CCR5 (delta 32) common to Northern European populations has been associated with reduced, but not absolute, HIV-1 transmission risk and delayed disease progression. A more commonly distributed transition causing a valine to isoleucine switch in transmembrane domain I of CCR2B (64I) with unknown functional consequences was recently shown to delay disease progression but not reduce infection risk. Although we confirm the lack of association of CCR2B 64I with transmission, we cannot confirm the association with delayed progression. Although subjects with CCR5 delta 32 defects had significantly reduced median viral load at study entry, providing a plausible explanation for the association with delayed progression, this association was not seen with CCR2B 64I. Further studies are needed to define the role of CCR2B64I in HIV pathogenesis.

Slower evolution of human immunodeficiency virus type 1 quasispecies during progression to AIDS

The evolution of human immunodeficiency virus type 1 (HIV-1) quasispecies at the envelope gene was studied from the time of infection in 11 men who experienced different rates of CD4+ cell count decline and 6 men with unknown dates of infection by using DNA heteroduplex mobility assays. Quasispecies were genetically homogeneous near the time of seroconversion. Subsequently, slower proviral genetic diversification and higher plasma viremia correlated with rapid CD4+ cell count decline. Except for the fastest progressors to AIDS, highly diverse quasispecies developed in all subjects within 3 to 4 years. High quasispecies diversity was then maintained for years until again becoming more homogeneous in a subset of late-stage AIDS patients. Individuals who maintained high CD4+ cell counts showed continuous genetic turnover of their complex proviral quasispecies, while more closely related sets of variants were found in longitudinal samples of severely immunocompromised patients. The limited number of variants that grew out in short-term PBMC cocultures were rare in the uncultured proviral quasispecies of healthy, long-term infected individuals but more common in vivo in patients with low CD4+ cell counts. The slower evolution of HIV-1 observed during rapid progression to AIDS and in advanced patients may reflect ineffective host-mediated selection pressures on replicating quasispecies.

Lack of associations of chemotactic cytokines with viral burden, disease progression, or lymphocyte subsets in HIV-infected individuals

Plasma samples from HIV-infected (HIV+) rapid progressors (RP) and nonprogressors (NP) in the San Francisco Men's Health Study showed significantly elevated levels of RANTES but not macrophage inflammatory protein 1 (MIP1) alpha or MIP1 beta in comparison to HIV-seronegative (HIV-) controls. In 32 individuals who became infected with HIV during the course of this study, RANTES levels were significantly higher in plasma samples collected at the time antibodies to HIV were first detected than in pre-seroconversion plasma samples. Both RP and NP showed significant temporal increases in plasma RANTES concentrations. No significant associations were observed, however, between plasma levels of these chemotactic cytokines and progression or known predictors of progression to AIDS including viral burden, levels of beta 2-microglobulin or neopterin, and levels of activated CD8+ lymphocytes. These findings are consistent with the results of a number of recent reports which suggest that these chemokines do not play a major systemic role in the long-term control of viremia or protection against the progression of HIV disease. It remains possible that chemotactic cytokines may contribute locally to control HIV in lymph nodes or other organs but it is also possible that they may be mediators of potentially harmful inflammatory responses.

The role of viral phenotype and CCR-5 gene defects in HIV-1 transmission and disease progression

Cellular entry of human immunodeficiency virus type 1 (HIV-1) requires binding to both CD4 (ref, 1, 2) and to one of the chemokine receptors recently discovered to act as coreceptors. Viruses that infect T-cell lines to form syncytia (syncytium-inducing, SI) are frequently found in late-stage HIV disease and utilize the chemokine receptor CXCR-4; macrophage-tropic viruses are non-syncytium-inducing (NSI), found throughout disease and utilize CCR-5 (ref. 3-11). We postulated that CCR-5 gene defects might reduce infection risk in seronegative subjects and prolong AIDS-free survival in seropositive subjects with NSI but not SI virus. Homozygous (delta ccr5/delta ccr5) and heterozygous (CCR5/delta ccr5) CCR-5 deletions (delta ccr5) were found in 7 (2.7%) and 51 (19.5%), respectively, of 261 seronegative subjects from the San Francisco Men's Health Study. CCR-5/delta ccr5 genotype was identified in 33 of 172 (19.2%) nonprogressors and 25 of 234 (10.7%) progressors from the seropositive arm of this cohort. The delta ccr5 allele conferred a significant protective effect against HIV-1 infection (P = 0.001) and a survival advantage against disease progression (P = 0.02). Although both progressing and nonprogressing CCR5/delta ccr5 subjects were identified, a distinct survival advantage was shown for those with NSI virus (P < 0.0001). Thus, the protective effect of delta ccr5 against disease progression is lost when the infecting virus uses CXCR-4 as a coreceptor.

The lack of association of marijuana and other recreational drugs with progression to AIDS in the San Francisco Men's Health Study

We evaluated the associations of specific recreational drugs and alcohol with laboratory predictors of AIDS at entry into the San Francisco Men's Health Study (SFMHS) in 1984 and with the development of the acquired immunodeficiency syndrome (AIDS) during 6 years of follow-up. Marijuana use was associated with a decreased rate of progression to AIDS in the univariate analysis (RR = 0.7; P = 0.01). Marijuana use was more common among individuals with elevated HIV viral core protein antibody (p24Ab) titer (> 1:16) at baseline (P = 0.03); this finding suggests that marijuana users were healthier at baseline. When the data were adjusted for p24 Ab and other laboratory parameters, no association with progression to AIDS was observed for marijuana, suggesting that the observed univariate result was due to a difference in HIV-related disease at the time of enrollment. No statistically significant associations were observed for nitrites, methylene dioxyamphetamines, ethyl chloride, downers, cocaine, stimulants, narcotics, or psychedelic drugs. These data suggest no substantial association between use of these drugs and the development of AIDS among HIV-infected men.

Expression of CD69 after in vitro stimulation: a rapid method for quantitating impaired lymphocyte responses in HIV-infected individuals

A flow cytometric assay based on expression of the activation antigen CD69 was developed to analyze immunological responses of T cells from human immunodeficiency virus (HIV)-infected (HIV+) or HIV-seronegative (HIV-) donors after in vitro simulation by antigens and polyclonal activators. The levels of CD69 on freshly-isolated or unstimulated, cultured CD3+, CD4+, or CD8+ peripheral blood lymphocyte (PBL) subsets were low and did not differ greatly between HIV+ and HIV- donors. The frequencies of CD3+, CD4+, and CD8+ lymphocytes from HIV+ donors that expressed CD69 after culture with antigenic or mitogenic stimuli were significantly lower than in HIV- donors. Comparison of CD69 expression with [3H]thymidine incorporation revealed that both assays could detect lymphocyte responses to antigenic or mitogenic stimuli. The CD3+ PBL from HIV+ or HIV- donors did not show increased CD69 expression after culture with soluble or cross-linked recombinant envelope glycoprotein, gp120. The gp120, however, significantly inhibited CD69 expression in phytohemagglutinin-stimulated T cells in vitro and may also affect T-cell activation in vivo. These studies demonstrate the usefulness of this CD69 expression assay for the rapid assessment of defects in immune responses of phenotypically defined lymphocyte subsets in HIV+ patients and for testing the effects of agents that modulate immune activation.

Functional characterization of human immunodeficiency virus type 1 nef genes in patients with divergent rates of disease progression

We have studied the sequence and function of the human immunodeficiency virus type 1 (HIV-1) nef genes from nine patients with highly divergent rates of disease progression enrolled in a longitudinal study of HIV disease. Over an average of 7.8 years of follow-up, three patients had net positive changes in CD4+ T-cell counts, three patients had net negative changes in CD4+ T cells but did not develop AIDS, and three patients progressed to AIDS. The nef gene from each of these patients was amplified and cloned, and the sequence of 8 to 10 clones was determined. Only 2 of 88 (2.3%) nef genes recovered from these nine patients were grossly defective. Moreover, there was no relationship between the phylogeny of nef sequences and the corresponding rates of disease progression from these patients. Representative nef genes from all nine patients were tested for their abilities to downregulate cell surface CD4 in a transient-transfection assay. There was no correlation found between the functions of the nef genes from these patients and their corresponding rates of disease progression. We conclude that the nef gene is not a common mediator of the rate of HIV disease progression in natural infection.

Persistence of attenuated rev genes in a human immunodeficiency virus type 1-infected asymptomatic individual

With the goal of examining the functional diversity of human immunodeficiency virus type 1 (HIV-1) env genes within the peripheral blood mononuclear cells of an asymptomatic individual, we substituted four complete env genes into the replication-competent NL4-3 provirus. Despite encoding full-length open reading frames for gp120 and gp41 and the second coding exon of tat and rev, each chimera was replication defective. Site-directed mutagenesis of codon 78 in the Rev activation domain (from a hitherto unique Ile to the subtype B consensus Leu) partially restored infectivity for two of three chimeras tested. Similarly, mutagenesis of rev codon 78 of NL4-3 from Leu to Ile partially attenuated this virus. Ile-78 was found in all 13 clones examined from samples taken from this asymptomatic subject 4.5 years after infection, including 9 from peripheral blood mononuclear cells and 4 from a virus isolate, as well as 4 additional clones each from peripheral blood mononuclear cells sampled 37 and 51 months later. We next examined conservation of the Rev activation domain within and among long-term survivors (LTS) and patients with AIDS, as well as T-cell-line-adapted strains of HIV-1. Putative attenuating mutations were found in a minority of sequences from all five LTS and two of four patients with AIDS. Of the 11 T-cell-line-adapted viruses examined, none had these changes. Among and within LTS virus population had marginally higher levels of diversity in Rev than in Env; patients with AIDS had similar levels of diversity in the two reading frames; and T-cell-line-adapted viruses had higher levels of diversity in Env. These results are consistent with the hypothesis that asymptomatic individuals harbor attenuated variants of HIV-1 which correlate with and contribute to their lack of disease progression.

AIDS as immune system activation. Key questions that remain

Immune system activation is gaining attention as a central part of HIV pathogenesis. Although there is no consensus yet as to the source of the signal or the result of the signalling, this line of thinking represents a significant shift in the paradigm away from considering HIV disease like any other cytopathic viral infection. Hopefully, completion of studies focussed on this approach will lead to more complete understanding of AIDS and more effective therapies, and will at least bring to the fore some of the central unanswered questions in modern cellular immunology.

HIV infection in homosexual and bisexual men 18 to 29 years of age: the San Francisco Young Men's Health Study

OBJECTIVES

Recent studies suggest very high human immunodeficiency virus (HIV) infection rates in some populations of younger homosexual men, but these studies may represent only particularly high-risk populations. The current study obtained population-based data on the HIV epidemic in young homosexual/bisexual men.

METHODS

A household survey of unmarried men 18 through 29 years of age involved a multistage probability sample of addresses in San Francisco. A follow-up interview and HIV test for men who were HIV negative at baseline were completed; the median follow-up was 8.9 months.

RESULTS

Sixty-eight of 380 homosexual/bisexual men (17.9%) tested HIV seropositive. Sixty-three percent of men reported one or more receptive anal intercourse partners in the previous 12 months, and 41% of those men did not use condoms consistently. The HIV seroincidence rate among those seronegative at first study was 2.6% per year.

CONCLUSIONS

HIV infection rates in young homosexual men in San Francisco are lower than those in the early 1980s; however, the rate of infection in these men, most of whom became sexually active after awareness of AIDS had become widespread, threatens to continue the epidemic in the younger generation at a level not far below that of a decade ago.

Human immunodeficiency virus type 1 evolution in vivo tracked by DNA heteroduplex mobility assays

High mutation rates and strong selective pressures imposed on human immunodeficiency viruses in vivo result in the formation of pools of genetic variants known as quasispecies. DNA heteroduplex mobility and tracking analyses were used to monitor the generation of HIV sequence diversity, to estimate quasispecies complexity, and to assess the turnover of genetic variants to approach an understanding of the relationship between viral quasispecies evolution in vivo and disease progression. Proviral DNA pools were nearly homogeneous soon after sexual transmission. The emergence and clearance of individual variants then occurred at different rates in different individuals. High quasispecies complexity was found in long-term-infected, asymptomatic individuals, while rapid CD4+ cell decline and AIDS were often, but not always, associated with lower quasispecies complexity. Proviral genetic variation was often low following in vitro culture, because of the outgrowth of one or a few variants that often became more abundant only later as proviruses in peripheral blood mononuclear cells. These studies provide insight into the dynamics of human immunodeficiency virus sequence changes in vivo and illustrate the utility of heteroduplex analysis for the study of phenomena associated with rapid genetic changes.

Circulating HIV-1-infected cell burden from seroconversion to AIDS: importance of postseroconversion viral load on disease course

The purpose of this study was to characterize quantitative changes in circulating infected cells over the natural history of human immunodeficiency virus (HIV) disease in relation to clinical/immunological outcome. HIV-1 gag DNA polymerase chain reaction (PCR) and peripheral blood mononuclear cell (PBMC) co-cultures were performed on limiting dilutions of cryopreserved PBMC from specimens collected at enrollment and after 5 years of follow-up from nine seropositive subjects classified as rapid progressors, nine intermediate progressors, and 10 nonprogressors. Limiting dilution PCR was also performed on serial pre/postseroconversion specimens from 18 seroconvertors. By quantitative DNA PCR analysis, the infected cell burden was significantly higher at enrollment in the RP [mean of 330 PCR units (PCRU)/10(6) PBMCs] than in the IP (160 PCRU/10(6) PBMCs) and NP (73 PCRU/10(6) PBMCs) groups (p = 0.05). When results were analyzed on an individual level with proportional hazard regression, baseline PCRU (p = 0.05) and CD4 slope (p = 0.0007) were significantly associated with developing acquired immune deficiency syndrome (AIDS) in 5 years, but baseline tissue culture infectious units (TCIU) was not. The increase in PCR-positive cells after 5 years was modest in all three groups (two- to fivefold), whereas the proportion of PCR-positive cells that yielded virus in culture increased significantly (21- to 31-fold) over time in all three groups. Infected cell burden in postseroconversion specimens was relatively stable within each subject, but varied greatly (from 1.6 to 1,024 PCRU/10(6) PBMCs) among subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutralizing antibody responses to autologous and heterologous isolates of human immunodeficiency virus

Although laboratory-adapted strains of human immunodeficiency virus (HIV) are generally highly sensitive to neutralization by HIV-positive patient sera, we have found a more complex pattern of cross-neutralization and neutralization resistance among low-passage clinical isolates. These HIV isolates, like many other lentiviruses, resisted neutralization by the patient's own (autologous) antibodies. We assessed the degree of antigenic relatedness between different patient isolates of HIV through cross-neutralization with heterologous sera and virus isolates. Complicated patterns emerged, with variation in breadth of neutralization among individual plasmas and variation in frequency of neutralization among isolates. In longitudinal studies of individuals, we found that some but not all such patients develop a neutralizing response that "catches up" with their earlier isolates after a lag period. Taken together, these data suggest that an individual's immune response broadens with time because of cumulative exposure to multiple antigenic variants that arise throughout HIV disease.

HIV-1 PCR and isolation in seroconverting and seronegative homosexual men: absence of long-term immunosilent infection

The presence of detectable HIV-1 prior to the appearance of HIV-1-specific antibody was assessed in 41 incident infections that occurred during a 6-year prospective cohort study. All available antibody-negative samples (n = 138) and the first antibody positive sample (n = 41) were tested, under code, by the polymerase chain reaction (PCR) in two laboratories and by HIV-1 isolation in a third laboratory. Samples were available as long as 66 months and at least 18 months before seroconversion for 24/41 subjects. An equal number of time-matched control specimens from persistently seronegative homosexual men and 103 samples from normal blood donors were also tested under code. Samples with discordant results were subjected to coded repeat analysis along with appropriate controls. All but one of the 41 first antibody-positive specimens (97.6%) were PCR positive and 65% were isolation positive. Two control specimens from seronegative homosexual men were PCR positive and one was culture positive, but HLA typing provided clear evidence of specimen mix-up in the specimen archive. For 37/41 seroconvertors, all available antibody negative specimens were negative by both PCR and virus isolation. In three cases, the specimen obtained 6 months before seroconversion was PCR and isolation positive. One specimen, obtained 12 months before SC, was PCR positive and isolation negative but was determined to be the result of sample contamination. Both PCR and isolation were negative in this subject 6 months before SC. In conclusion, we were unable to detect immunosilent infection > 6 months before seroconversion in high-risk homosexual men.

The characterization of non-progressors: long-term HIV-1 infection with stable CD4+ T-cell levels

OBJECTIVE

To identify and characterize individuals with long-term HIV-1 infection who have experienced little or no progressive CD4+ T-cell loss during follow-up.

PATIENTS AND METHODS

The rate of CD4+ T-cell loss (CD4 slope) was determined for each of the 290 participants in the San Francisco Men's Health Study who were seropositive at study entry in 1984. The study population was stratified, by CD4 slope, into 10 groups of 29 individuals and each group was characterized using a variety of cross-sectional and longitudinal laboratory measurements.

RESULTS

Approximately 10% of the HIV-1-infected men experienced no net CD4+ T-cell loss during 78 months of follow-up. Compared with all other seropositive subjects, these 'non-progressors' were the extreme cases in a relatively continuous distribution of CD4 slopes, rather than a discrete subpopulation. Although they had no net cell loss, their mean CD4+ cell count was approximately 400 x 10(6)/l lower and their mean CD8+ cell count approximately 250 x 10(6)/l higher than seronegative subjects, suggesting early changes followed by stabilization. The CD4 slope was associated with the levels of beta 2-microglobulin, neopterin, p24 antibody, erythrocyte sedimentation rate, viral burden, and the proportion of HIV-1 isolates with tropism for the MT-2 T-cell line. Multivariate cluster analysis of these laboratory markers did not distinguish the non-progressors as a distinct subgroup.

CONCLUSIONS

These findings support both a biphasic natural history and the suggestion that the broad range in HIV disease progression rates may be the result of several independent factors interacting in a variety of combinations. Recent changes in laboratory markers, known to predict both CD4+ cell loss and AIDS, suggest that non-progressors are undergoing slow HIV disease progression.

Does drug use cause AIDS?

A hypothesis identifying substance abuse as a main cause of AIDS has naturally excited much publicity. But such claims have no basis in fact.

Use of T lymphocyte subset analysis in the case definition for AIDS

Infection with HIV-1 and < 200 CD4+ lymphocytes/mm3 has been proposed as an AIDS-defining condition. We have evaluated the effects of using this and other T-cell subset measurements, in the diagnosis of AIDS in two cohorts of homosexual/bisexual men in San Francisco. Among 762 HIV-1 infected men, 200 CD4+ lymphocytes/mm3 corresponded to 13 percent CD4+ lymphocytes and a CD4+/CD8+ ratio of 0.23. If these AIDS-defining criteria had been implemented in mid-1991, the number of living AIDS cases would have increased by 106 (212%), 133 (266%), and 136 (272%), respectively. When these criteria were first met, either before or in the absence of a clinical AIDS diagnosis, about half of the subjects were asymptomatic and the median clinically AIDS-free interval was approximately 2 years. Using two consecutive tests or pair-wise combinations of criteria reduced the number of cases identified by testing error or transient biological variation, but the number of living AIDS cases would still be increased more than twofold. Finally, any AIDS case definition using a specific T-cell subset value will be compromised by the inherent variability in these measurements and the substantial overlap in the results for those with and without clinical manifestations of HIV infection.

Risk factors for hepatitis C virus seropositivity in heterosexual couples

OBJECTIVES

To determine the risk of heterosexual transmission of hepatitis C virus (HCV) and to identify other risk factors for HCV seropositivity in heterosexual couples.

DESIGN

Retrospective cross-sectional study comparing HCV-seropositive and HCV-seronegative heterosexual men and women.

SETTING

Couples recruited from the community and screened for participation in a study of the heterosexual transmission of human immunodeficiency virus.

PARTICIPANTS

A total of 340 subjects, 170 men and 170 women in sexual partnerships, aged 18 through 61 years.

MAIN OUTCOME MEASURE

Seropositivity for HCV antibodies.

RESULTS

Overall, 31 (18%) of the 170 women and 56 (33%) of the 170 men were positive by a four-antigen HCV immunoblot. Injection drug use and hemophilia were strongly associated with HCV seropositivity. Sixty-four percent of injection drug users were positive (odds ratio [OR], 27.0; 95% confidence interval [CI], 13.4 to 56.1; P < .0001), as were all four hemophiliacs in the study. History of blood transfusion was significantly associated with HCV seropositivity (OR, 2.7; 95% CI, 1.1 to 7.0; P = .02). Positivity for HCV was not associated with measures of sexual behavior within couples or with numbers of other sexual partners, history of sexually transmitted diseases, or human immunodeficiency virus seropositivity. However, two of the 31 women without parenteral risk but with a long-term HCV-positive male partner were HCV seropositive compared with none of 81 women with an HCV-negative male partner (P = .07).

CONCLUSIONS

These results provide little evidence of HCV sexual transmission but are consistent with infrequent sexual transmission. They corroborate the importance of injection drug use and transfusion of blood or blood products in transmitting HCV and underscore the importance of ascertaining parenteral exposures when examining sexual transmission of HCV.

Comparison of risk factors for hepatitis C and hepatitis B virus infection in homosexual men

Serum samples from 735 homosexual or bisexual men were tested for antibodies to hepatitis C virus (HCV) and serologic markers of hepatitis B virus (HBV), and risk factors for each infection were compared. Thirty-four (4.6%) were confirmed HCV-positive compared with 81% positive for one or more HBV serologic marker(s). History of intravenous drug use (IVDU) and blood transfusion were significantly associated with HCV positivity (odds ratio [OR] = 14.3 and 4.4, respectively), but neither was significantly associated with HBV positivity. Sexual behavior was significantly associated with infection with both viruses. When IVDU and blood transfusion were controlled for, HCV infection was marginally associated with > 50 sex partners/year (OR = 2.1), > 25 oral receptive partners (OR = 2.4), and > 25 anal receptive partners (OR = 1.9). HBV infection was more strongly associated with the same variables. HCV infection is uncommon in homosexual men and IVDU is the primary route of transmission, but sexual transmission also occurs, albeit infrequently.

The natural history and pathogenesis of HIV infection

Infection with human immunodeficiency virus (HIV) results in progressive deterioration of the cell-mediated immune system characterized by T-helper-cell dysfunction and loss in the face of signs of generalized immune-system activation. The final stage of HIV disease, AIDS, has a myriad of opportunistic infections and malignancies as its hallmarks. The causal relationship between HIV and this complex disease pattern is clear but the mechanisms by which it occurs are not well understood. There are a number of new developments in our understanding of the natural history of HIV infection from a laboratory standpoint. Our review of this information raises further questions as to the validity of the conventional "cytopathic" model and all its direct descendants. In response to these conflicts, we have developed and present an alternative hypothesis in which AIDS pathogenesis, in all its manifestations, is seen as the outcome of one central process, excess immune activation generated by the interaction of virus with the CD4 receptor. The implications of this hypothesis on therapy of HIV infections are discussed.

Lack of detection of human immunodeficiency virus in persistently seronegative homosexual men with high or medium risks for infection

Some studies have suggested that seronegative homosexual men who have practiced high-risk sexual behavior can carry the human immunodeficiency virus (HIV) in a silent state, detectable only by polymerase chain reaction (PCR) or selective viral culture. To assess this concept, blood specimens were studied from 59 homosexual men with recognized risk behaviors: unprotected anal receptive intercourse at least once and many lifetime sex partners. After extensive virologic studies and PCR analysis, only one virus-positive, antibody-negative individual was identified. These findings indicate that HIV virus-positive, seronegative individuals are rare.

Immune response to HIV p24 core protein during the early phases of human immunodeficiency virus infection

The immune response to the p24 core antigen of human immunodeficiency virus type 1 (HIV-1) was studied in serial samples collected prospectively from 52 homosexual males in two separate cohorts from Amsterdam and San Francisco. p24 antibody levels were quantified with an antigen sandwich immunoassay using p24 recombinant antigen as capture and probe. Titers and slopes of dilution curves reflecting antibody affinity were analyzed. Only 45 of 52 men developed a measurable primary immune response to p24. In 17 (33%) patients there was a low response with maximum antibody titer below 66, shallow (low affinity) dilution curve, and 10 of the 17 became HIV antigen positive over a 2 year period. In 24 (46%) of the 52 patients titers ranged from 100-4000, steeper dilution curves were noted, and none became HIV antigen positive. Four (8%) men developed a strong immune response with high titers (greater than 12,000) and high affinity type dilution curve. Over time, after the peak immune response, antibody titer declined in some individuals related in part to the formation of immune complexes between HIV-1 p24 antigen and antibody which were dissociable. In vitro, the addition of increasing amounts of purified p24 antigen corresponded to decreasing antibody titer and a shallower dilution curve suggesting a preferential consumption of high affinity antibodies for complex formation. The magnitude of immune response to HIV-1 p24 antigen varies widely in infected homosexual men. Both the intrinsic ability to mount an immune response and immune complex formation contribute to the measurable antibody level.