Acyclovir and transmission of HIV-1 from persons infected with HIV-1 and HSV-2.

BACKGROUND: Most persons who are infected with human immunodeficiency virus type 1 (HIV-1) are also infected with herpes simplex virus type 2 (HSV-2), which is frequently reactivated and is associated with increased plasma and genital levels of HIV-1. Therapy to suppress HSV-2 reduces the frequency of reactivation of HSV-2 as well as HIV-1 levels, suggesting that suppression of HSV-2 may reduce the risk of transmission of HIV-1. METHODS: We conducted a randomized, placebo-controlled trial of suppressive therapy for HSV-2 (acyclovir at a dose of 400 mg orally twice daily) in couples in which only one of the partners was seropositive for HIV-1 (CD4 count, > or = 250 cells per cubic millimeter) and that partner was also infected with HSV-2 and was not taking antiretroviral therapy at the time of enrollment. The primary end point was transmission of HIV-1 to the partner who was not initially infected with HIV-1; linkage of transmissions was assessed by means of genetic sequencing of viruses. RESULTS: A total of 3408 couples were enrolled at 14 sites in Africa. Of the partners who were infected with HIV-1, 68% were women, and the baseline median CD4 count was 462 cells per cubic millimeter. Of 132 HIV-1 seroconversions that occurred after randomization (an incidence of 2.7 per 100 person-years), 84 were linked within couples by viral sequencing: 41 in the acyclovir group and 43 in the placebo group (hazard ratio with acyclovir, 0.92, 95% confidence interval [CI], 0.60 to 1.41; P=0.69). Suppression with acyclovir reduced the mean plasma concentration of HIV-1 by 0.25 log(10) copies per milliliter (95% CI, 0.22 to 0.29; P<0.001) and the occurrence of HSV-2-positive genital ulcers by 73% (risk ratio, 0.27; 95% CI, 0.20 to 0.36; P<0.001). A total of 92% of the partners infected with HIV-1 and 84% of the partners not infected with HIV-1 remained in the study for 24 months. The level of adherence to the dispensed study drug was 96%. No serious adverse events related to acyclovir were observed. CONCLUSIONS: Daily acyclovir therapy did not reduce the risk of transmission of HIV-1, despite a reduction in plasma HIV-1 RNA of 0.25 log(10) copies per milliliter and a 73% reduction in the occurrence of genital ulcers due to HSV-2. (ClinicalTrials.gov number, NCT00194519.)

Cutaneous leishmaniasis. The defect in T cell influx in BALB/c mice.

Local cellular responses to cutaneous infection with Leishmania mexicana amazonensis were examined in susceptible (BALB/c) and resistant (C57BL/6) mouse strains by immunocytochemical and electron microscopic studies. Infection during the first 8 wk in both animal strains was characterized by progressively enlarging lesions, epidermal thickening and ulceration, and accumulation of eosinophils and Ia+ infected macrophages. Healing of C57BL/6 mouse lesions began after 12 wk of infection and was associated with local influx of both Th (L3T4+) and T cytotoxic/suppressor (Lyt-2+) cells into the dermis, and Ia antigen expression on epidermal keratinocytes. T lymphocyte infiltration was marked and intracellular parasites were scarce by 21 wk of C57BL/6 infection. Similarly, granulomas in C57BL/6 livers contained L3T4+ and Lyt-2+ T lymphocytes and no visible intracellular parasites by 21 wk of infection. In contrast, BALB/c mouse lesions continued to enlarge and never healed. Throughout the entire course of infection, T lymphocyte influx into the heavily infected dermis was minimal. Keratinocyte Ia expression was absent in BALB/c lesions. BALB/c livers were heavily infected by 18 wk of cutaneous infection, with few demonstrable T lymphocytes. A systemic absence of T cells could not be demonstrated in BALB/c mice. Both L3T4+ and Lyt-2+ T cells were found in the peripheral blood in normal numbers in both mouse strains. Our results support the role of T cells as important local effector cells in the healing response of murine cutaneous leishmaniasis. We suggest that local T lymphocyte infiltration may provide lymphokines, particularly IFN-gamma, that can activate infected macrophages to destroy the intracellular parasites. Alternatively, T cells may play a cytotoxic role, killing infected macrophages and allowing local humoral factors to destroy released extracellular parasites.

The dynamics of granuloma formation in experimental visceral leishmaniasis.

We have examined the temporal sequence of events leading to the formation of hepatic granulomas after the intravenous injection of L. donovani amastigotes into BALB/c mice. Parasite ingestion by permissive Kupffer cells (KC) occurred promptly, and local KC aggregations were the foci about which granulomas were subsequently formed. Infected KC were recognized by the uptake of colloidal carbon and the expression of the macrophage-specific antigen recognized by F4/80 mAb. Peroxidase-positive granulocytes migrated rapidly and were followed by monocytes and L3T4+ T cells that enclosed the infected KC. Thereafter, Ly-2+ T cells were prominent members of the granulomatous lymphoid population. Parasites multiplied until 4 wk, and then a prompt reduction in infected cells occurred. This was associated with a sharp decline in the L3T4+ T cells of the granulomas and the maintenance of the Ly-2+ subset. In comparison, athymic nu/nu mice developed smaller, more slowly appearing granulomas that contained granulocytes and monocytes and exhibited progressive parasite replication. Upon rechallenge, the entire process was completed in 2 wk, and infected KC in the euthymic mice were never observed. We hypothesize that the effectiveness of the granulomatous response requires the destruction of parasitized host cells (KC), in a lymphokine rich environment. We further suggest that the Ly-2+ T cell serves as an important effector cell in this process, either by direct cytotoxicity or by supporting the cytotoxic potential of other cell types in the granuloma.

HIV-1 induces cytotoxic T lymphocytes in the cervix of infected women.

Although T lymphocytes are present in the genital mucosa, their function in sexually transmitted diseases is unproven. To determine if cervical T cells mediate HIV-specific cytolysis, mononuclear cells in cytobrush specimens from HIV-1-infected women were stimulated in vitro with antigen. Resultant cell lines lysed autologous targets expressing HIV-1 proteins in 12/19 (63%) subjects, and these responses were detected intermittently on repeated visits. All 8 subjects with blood CD4+ counts > or =500 cells/microl had HIV-1-specific cervical CTL, whereas only 4/11 with counts <500 cells/microl had detectable responses (P = 0.008). Class II MHC-restricted CD4+ CTL clones lysed targets expressing Env gp41 or infected with HIV-1. Class I MHC-restricted CD8+ clones recognized HIV-1 Gag- or Pol-expressing targets, and the epitopes were mapped to within 9-20 amino acids. Comparisons of intra-individual cervical and blood CTL specificities indicate that epitopes recognized by CTL in the cervix were commonly recognized in the blood. These studies provide the first definitive evidence for an MHC-restricted effector function in human cervical lymphocytes.

An excess of rare genetic variation in ABCE1 among Yorubans and African-American individuals with HIV-1.

Signatures of natural selection occur throughout the human genome and can be detected at the sequence level. We have re-sequenced ABCE1, a host candidate gene essential for HIV-1 capsid assembly, in European- (n=23) and African-descent (Yoruban; n=24) reference populations for genetic variation discovery. We identified an excess of rare genetic variation in Yoruban samples, and the resulting Tajima's D was low (-2.27). The trend of excess rare variation persisted in flanking candidate genes ANAPC10 and OTUD4, suggesting that this pattern of positive selection can be detected across the 184.5 kb examined on chromosome 4. Owing to ABCE1's role in HIV-1 replication, we re-sequenced the candidate gene in three small cohorts of HIV-1-infected or resistant individuals. We were able to confirm the excess of rare genetic variation among HIV-1-positive African-American individuals (n=53; Tajima's D=-2.34). These results highlight the potential importance of ABCE1's role in infectious diseases such as HIV-1.

Latent HIV-1 infection in enriched populations of blood monocytes and T cells from seropositive patients.

The extent of latent HIV-1 infection in blood T cells and monocytes of 23 seropositive individuals was examined using DNA amplification (PCR) of HIV-1 sequences. Amplified DNA was found in at least one cell type in all seropositives tested, including 13 asymptomatic, 5 ARC, and 5 AIDS patients. Amplification with two or more primer sets from the gag, env, LTR occurred in 21 (91%) patients' T cells and 17 (74%) patients' monocytes. However, amplification with the LTR primers in monocytes was uncommon. Among four patients tested, amplified DNA continued to be detected after a greater than one thousand-fold dilution (less than 500 cells) of both T cell and monocyte lysates. Repeat analysis after 7-9 mo in five seropositives yielded similar findings in T cells and monocytes, but some variation in the efficacy of amplification with individual primers occurred. There was no difference in those 10 patients who were taking AZT, compared to those who were untreated. Our results indicate that a fraction (less than 1%) of both T cells and monocytes in blood carry a latent infection in all stages of HIV-1 disease and can serve as reservoirs throughout AZT therapy.

Cytotoxic and proliferative T cell responses in HIV-1-infected Macaca nemestrina.

Macaca nemestrina has been described as an animal model for acute HIV-1 infection. This animal, unlike most infected humans, appears to contain HIV-1 replication. Therefore analysis of HIV-1-specific proliferative and cytotoxic T lymphocyte (CTL) responses following HIV-1 challenge of M. nemestrina may provide information into the role of such responses in both the control of acute HIV infection and protective immunity. Although CD4+ T cell responses to HIV-1 are generally difficult to detect in HIV-1-infected humans, early and persistent CD4+ T cell proliferative responses to HIV-1 antigens were detected in all HIV-1-inoculated M. nemestrina. HIV-1-specific CD8+ CTL responses were evaluated in PBMC by stimulation with autologous cells expressing HIV-1 genes, limiting dilution precursor frequency analysis, and T cell cloning. CTL reactive with gag, env, and nef were present 4-8 wk after infection, and persisted to 140 wk after infection. The presence of both CD4+ and CD8+ T cell responses before and after clearance of HIV-1 viremia is consistent with a role for these responses in the successful control of HIV-1 viral replication observed in M. nemestrina. Further studies of T cell immunity in these animals that resist disease should provide insights into the immunobiology of HIV-1 infection.

Role for HLA class II molecules in HIV-1 suppression and cellular immunity following antiretroviral treatment.

HIV-1-infected patients treated early with combination antiretrovirals respond favorably, but not all maintain viral suppression and improved HIV-specific Th function. To understand if genetic factors contribute to this variation, we prospectively evaluated over 18 months 21 early-treated patients stratified by alleles of class II haplotypes. All seven subjects with the DRB1*13-DQB1*06 haplotype, but only 21% of other subjects, maintained virus suppression at every posttreatment measurement. Following HIV-1 p24 antigen stimulation, PBMCs from patients with this haplotype demonstrated higher mean lymphoproliferation and IFN-gamma secretion than did cells from patients with other haplotypes. Two DRB1*13-restricted Gag epitope regions were identified, a promiscuous one that bound its putative restriction element with nanomolar affinity, and another that mapped to a highly conserved region. These findings suggest that class II molecules, particularly the DRB1*13 haplotype, have an important impact on virologic and immunologic responses. The advantage of the haplotype may relate to selection of key HIV-1 Th1 epitopes in highly conserved regions with avid binding to class II molecules. Eliciting responses to the promiscuous epitope region may be beneficial in vaccine strategies.

In men at risk of HIV infection, IgM, IgG1, IgG3, and IgA reach the human foreskin epidermis.

We profiled the humoral response in the penis, an area that has been minimally explored but may be relevant for protecting insertive men against HIV and other sexually acquired infections. Comparing paired tissue samples from 20 men at risk of HIV infection, foreskin contains less immunoglobulin A (IgA) and more IgG2 than colon. Using foreskin dermal and epidermal explants and paired plasma from 17 men, we examined Ig accumulation by normalizing Ig to human serum albumin (HSA) transudation. Dermal IgM, IgG2, IgA, and IgE ratios were greater than that in plasma, suggesting there is local antibody secretion at the dermis. Local Ig transcription was concentrated at the inner rather than the outer foreskin, and inner foreskin Ig ratios did not correlate with blood, indicating that localized production can contribute to the foreskin response. IgM, IgG1, IgG3, and IgA have preferential access to the foreskin epidermis, whereas IgG2, IgG4, and IgE are restricted to the dermis. Lastly, Ad5-specific IgA was selectively present in the colon, whereas foreskin Ad5 IgG was mainly derived from blood, and reached the inner epidermis at higher ratios than the outer (P<0.002). In summary, the foreskin antibody response combines local and systemic sources, and there is selective isotype accumulation in the epidermis.

A study of vaccine-induced immune pressure on breakthrough infections in the Phambili phase 2b HIV-1 vaccine efficacy trial.

INTRODUCTION: The Merck Adenovirus-5 Gag/Pol/Nef HIV-1 subtype-B vaccine evaluated in predominately subtype B epidemic regions (Step Study), while not preventing infection, exerted vaccine-induced immune pressure on HIV-1 breakthrough infections. Here we investigated if the same vaccine exerted immune pressure when tested in the Phambili Phase 2b study in a subtype C epidemic. MATERIALS AND METHODS: A sieve analysis, which compares breakthrough viruses from placebo and vaccine arms, was performed on 277 near full-length genomes generated from 23 vaccine and 20 placebo recipients. Vaccine coverage was estimated by computing the percentage of 9-mers that were exact matches to the vaccine insert. RESULTS: There was significantly greater protein distances from the vaccine immunogen sequence in Gag (p=0.045) and Nef (p=0.021) in viruses infecting vaccine recipients compared to placebo recipients. Twenty-seven putative sites of vaccine-induced pressure were identified (p<0.05) in Gag (n=10), Pol (n=7) and Nef (n=10), although they did not remain significant after adjustment for multiple comparisons. We found the epitope sieve effect in Step was driven by HLA A∗02:01; an allele which was found in low frequency in Phambili participants compared to Step participants. Furthermore, the coverage of the vaccine against subtype C Phambili viruses was 31%, 46% and 14% for Gag, Pol and Nef, respectively, compared to subtype B Step virus coverage of 56%, 61% and 26%, respectively. DISCUSSION: This study presents evidence of sieve effects in Gag and Nef; however could not confirm effects on specific amino acid sites. We propose that this weaker signal of vaccine immune pressure detected in the Phambili study compared to the Step study may have been influenced by differences in host genetics (HLA allele frequency) and reduced impact of vaccine-induced immune responses due to mismatch between the viral subtype in the vaccine and infecting subtypes.

Heme binding to Leishmania mexicana amazonensis.

Leishmania mexicana amazonensis is a pathogenic parasite whose growth, due to a biosynthetic deficiency, is dependent on a supply of exogenous heme. Utilizing [55Fe]hemin, we have demonstrated that heme binding to non-dividing cultured promastigotes of L. m. amazonensis at 4 degrees C reaches equilibrium within 6 h, is 95% dissociable by 28 h and is elevated approximately 5-fold by decreasing the pH of the binding buffer to 5.4. Metalloporphyrins substituted either at the central metal atom or in the porphyrin ring all displaced [55Fe]hemin binding to varying extents. Scatchard analysis revealed the affinity of the interaction to be 0.03 nM-1 and the number of binding sites to be 400 per promastigote. These findings are remarkably similar to those demonstrated in murine erythroleukemia cells and are characteristic of a receptor-ligand interaction. During logarithmic growth, promastigote heme binding was increased approximately 10-fold compared to stationary phase organisms. The increase was caused by a 4-fold greater number of binding sites per promastigote with no significant change in affinity. These findings demonstrate not only that L. m. amazonensis promastigotes bind heme specifically, but that the binding may be regulated by the growth phase of the parasite.

Demonstration of alpha 1-antitrypsin by immunofluorescence on paraffin-embedded hepatic and pancreatic tissue.

Studies were performed in an attempt to improve current immunohistological techniques for the demonstration of alpha 1-antitrypsin (A1AT) in formalin-fixed paraffin-embedded tissues. The unwanted fluorescence (UF) commonly occurring in such procedures was found to be effectively eliminated by immunoadsorption of A1AT antisera with human serum lacking A1AT (Pi-null phenotype) coupled in solid phase to glutaraldehyde-activated aminohexyl-Sepharose 4B. Specificity of the antisera for A1AT was established by subsequent solid phase immunoadsorption against normal human serum bound to AH-Sepharose 4B. Using these techniques, immunoreactive A1AT was demonstrated in the cytoplasm of hepatocytes in liver biopsies obtained from patients with Z and MZ serum phenotypes, and in the cytoplasm of normal pancreatic islet cells.

Immune defence against HIV-1 infection in HIV-1-exposed seronegative persons.

Rare individuals who are repeatedly exposed to HIV-1 through unprotected sexual contact fail to acquire HIV-1 infection. These persons represent a unique study population to evaluate mechanisms by which HIV-1 replication is either prevented or controlled. We followed longitudinally a group of healthy HIV-1 seronegative persons each reporting repeated high-risk sexual activities with their HIV-1-infected partner at enrollment. The volunteers were primarily (90%) male homosexuals, maintaining high risk activities with their known infected partner (45%) or multiple other partners (61%). We evaluated the quantity and specificity of HIV-1-specific T cells in 31 exposed seronegatives (ES) using a IFN-gamma ELISPOT assay to enumerate T cells recognizing epitopes within HIV-1 Env, Gag, Pol and Nef. PBMC from only three of the 31 volunteers demonstrated ex vivo HIV-1-specific IFN-gamma secretion, in contrast to nearly 30% exhibiting cytolytic responses in previous studies. These findings suggest that if T cell responses in ES are induced by HIV-1 exposure, the frequency is at low levels in most of them, and below the level of detection using the ELISPOT assay. Alternative approaches to improve the sensitivity of detection may include use of dendritic cells as antigen-presenting cells in the ex vivo assay and more careful definition of the risk behavior and extent of HIV-1 exposure in conjunction with the evaluation of T cell responses.

CD8 CTL responses in vaccines: emerging patterns of HLA restriction and epitope recognition.

We evaluated MHC-class I-restricted CTL responses induced by HIV-1 clade B-based vaccines in nine HIV-1 seronegative vaccine recipients with regard to their patterns of HLA restriction and epitope recognition. We found that seven of nine volunteers developed detectable CTL reactivities against novel epitopes within the HIV-1 Env and Gag proteins. Although four of nine subjects were HLA-A*0201, none of the cellular responses was restricted in the context of this allele. The type of responses observed in this sampling of vaccines appeared similar to those reported during primary infection and among long term non-progressors, with three out of nine subjects recognizing HLA-B27 or HLA-B17(57)-restricted epitopes. Although the majority of CTL responses were directed against novel epitopes, these effectors were still able to mediate cross-clade reactivities.

Cellular immunity and target cell susceptibility in persons with repeated HIV-1 exposure.

We prospectively studied 37 HIV-1 uninfected persons engaging in repeated high risk sexual activity with an HIV-1 infected partner, as well as 18 of their infected partners. Only one subject (3%) demonstrated the homozygous 32-bp deletion delta32delta32 of the HIV-1 co-receptor CCR5. CD4+ cells from all high risk subjects except the delta32delta32 CCR5 homozygote were susceptible in vitro to both CCR5-dependent and CXCR4-dependent HIV-1 strains. Median HIV-1 plasma RNA levels of the infected partners were not significantly different from levels of matched infected controls. Thirteen subjects demonstrated HIV-1 specific CTL at one or more visits, and these activities were more commonly observed in persons with the wild type CCR5 genotype. These results indicate that cellular immunity rather than inheritance of the delta32 CCR5 mutation accounts more often for persistently HIV-1-resistant cases.

Evaluation of cytotoxic T cell responses to candidate HIV-1 vaccines in HIV-1-uninfected individuals.

The ability to induce a strong, HIV-1-specific CD8+ CTL response is assumed to be an important component of a protective HIV-1 vaccine. Identification of CTL responses in seronegative vaccines requires in vitro stimulation of CTL precursors with cells that have processed HIV-1 gene products via the endogenous intracellular pathway for presentation in association with MHC class I molecules. We have developed a method to detect CTL responses to HIV epitopes and HIV-infected cells that can be applied to recipients of HIV vaccines regardless of immunization with a particular recombinant virus or prior immunological status. Primed CTL precursors from PBMCs are stimulated for two 1-week cycles with autologous monocyte-derived macrophages infected with HIV-1Ba-L. The effector CTLs generated in culture are then tested in a standard chromium release assay for lysis, using autologous target cells, including EBV-transformed lymphoblastoid cell lines (LCLs) expressing individual HIV-1 proteins following infection with a recombinant vaccinia virus, or LCLs transduced with the CD4 gene and infected with isolates of HIV. Using this methodology we have examined CTL responses induced by candidate HIV vaccines in HIV-1-uninfected individuals participating in phase I/II AVEG trials. Our findings indicate that this approach makes it possible to overcome some of the previous technical difficulties involved in the analysis of CTL responses in immunocompetent vaccine recipients and thereby facilitates the identification of potentially effective candidate HIV-1 vaccines.

HIV-infected macrophages as efficient stimulator cells for detection of cytotoxic T cell responses to HIV in seronegative and seropositive vaccine recipients.

The induction of CD8+ CTL responses is a goal of most HIV-1 vaccine trials, but such potentially protective effector responses have been difficult to evaluate, particularly in these vaccine prevention trials, due to technical obstacles. We report a method to evaluate CTL responses based on the ability to infect autologous macrophages with a monocytotropic strain of HIV-1, and to use these cells as efficient stimulators. This approach does not require the addition of exogenous cytokines, allows detection of class I-restricted CTLs against multiple HIV-1 gene products, and circumvents the problem, often detected using other stimulator cells, of high levels of lytic activity against target cells expressing vaccinia and/or EBV antigens. Adherent monocyte-derived macrophages were infected with HIV-1 Ba-L, and used within 2-3 weeks as autologous stimulators. Fresh PBMCs were cultured with the infected macrophages, harvested after 1 week, replated with fresh infected macrophages and filler cells, and tested after 5-7 days for cytolytic activity. CD8+ CTL responses specific for HIV-1 envelope were detected at an E:T ratio as low as 5:1 in two of four HIV-1-uninfected recipients of an HIV vaccine regimen that included a recombinant live vaccinia virus. Cytotoxic T lymphocyte activity could be detected > 1 year following vaccination. Similar lytic activity was detected with cryopreserved responder cells. In two HIV-1-infected individuals participating in a blinded therapeutic vaccination trial, the use of infected macrophages as in vitro stimulators permitted detection of the presence of envelope and gag-specific CTLs. No responses were observed in nonimmunized, uninfected controls. Thus, HIV-1-infected macrophages can stimulate in vitro the repertoire of primed HIV-reactive CD8+ precursors from seronegative and seropositive participants in HIV-1 vaccine trials, and should facilitate the identification of potentially effective candidate HIV vaccines.

Advancing AIDSVAX to phase 3. Safety, immunogenicity, and plans for phase 3.

AIDSVAX (VaxGen, Inc., South San Francisco, CA), a possible vaccine to protect against human immunodeficiency virus type 1 (HIV-1) infection, is being tested for efficacy in phase 3 studies. It has been tested for potential efficacy in chimpanzees, and tested for safety and immunogenicity in human clinical studies. Four candidate vaccines, each with a different envelope protein antigen or combination of antigens, have been produced in alum formulations. In both design and clinical testing, AIDSVAX has an excellent safety profile. Because these highly purified proteins were prepared using recombinant DNA technology, there is no possibility of these vaccines causing HIV infection. Having been administered to over 1200 people, the only side effects attributable to AIDSVAX have been local pain and inflammation at the injection site. After immunization, essentially all recipients developed a robust antibody response, including binding and neutralizing antibodies. The neutralizing antibodies peaked after a 12-month boost. Excellent memory is induced. Two phase 3 trials of two bivalent formulations will evaluate their efficacy. One trial will use a bivalent subtype B formulation. This trial in North America will involve 5000 men who have sex with men and heterosexual women at high risk. The other study will use a bivalent subtype B/subtype E formulation. This trial in Thailand and will involve 2500 intravenous drug users. Both studies will be randomized, double-blinded and placebo controlled. The volunteers will be followed for 3 years. The end points of the studies are infection, as defined by seroconversion to standard diagnostic tests, and viral load, as defined by commercial polymerase chain reaction (PCR) tests.

HIV-1MN recombinant glycoprotein 160 vaccine-induced cellular and humoral immunity boosted by HIV-1MN recombinant glycoprotein 120 vaccine. National Institute of Allergy and Infectious Diseases AIDS Vaccine Evaluation Group.

We evaluated prime-boost immunization with two recombinant envelope glycoprotein subunit vaccines (HIV-1MN recombinant gp160 vaccine in alum adjuvant [MN rgp160] and HIV-1MN recombinant gp120 vaccine in alum adjuvant [MN rgp120]) for safety and immunogenicity in healthy, HIV-1-uninfected adults. The rationale was to combine the helper T cell memory and binding antibody responses typically induced by rgp160 vaccines with the superior neutralizing antibody responses induced by rgp120 vaccines. In a double-blinded, controlled trial, volunteers were randomly assigned to receive MN rgp160 or adjuvant placebo, and a subset later received MN rgp120. The two vaccines were safe, but reactions to MN rgp160 and its adjuvant placebo exceeded those to MN rgp120. MN rgp160 induced IgG binding antibodies, including all IgG subclasses, to MN rgp160 in all vaccine recipients. HIV-1MN-neutralizing and anti-V3 MN peptide-binding antibodies were observed in a majority of volunteers after the fourth MN rgp160 immunization, but at lower levels compared with immunization with MN rgp120 in historical controls. HIV-1-binding, neutralizing, and fusion inhibition antibodies were boosted to the highest levels among MN rgp160 recipients after MN rgp120 booster injections. MN rgp120 boosting appeared to alter the distribution of MN rgp160 vaccine-induced, anti-MN rgp160 IgG subclass antibodies. MN rgp160 induced helper T cell memory, measured by lymphocyte proliferation, Thl and Th2 cytokine production, and skin testing. Strategies including both subunit vaccines may help maximize antibody and helper T cell memory responses to HIV-1 envelope glycoprotein.

Studies of high doses of a human immunodeficiency virus type 1 recombinant glycoprotein 160 candidate vaccine in HIV type 1-seronegative humans. The AIDS Vaccine Clinical Trials Network.

We examined the safety and immunogenicity of a baculovirus-derived recombinant HIV-1 envelope glycoprotein vaccine candidate, rgp160 (VaxSyn; MicroGeneSys, Meriden, CT), administered at doses of 160 or 640 micrograms to 56 healthy, HIV-1-seronegative adults, in a randomized, double-blind, placebo-controlled study. Immunizations were given intramuscularly at 0, 1, 6, and 12 months. Both doses were generally well tolerated, although self-limited local reactions were frequent. No other clinical or laboratory toxicities were noted, and no effects on CD4 or CD8 lymphocyte counts or percentages were noted. Serum antibody responses to HIV proteins were detected by Western blot (WB) in 19 of 20 and in 19 of 19 recipients of four doses of 160 and 640 micrograms, respectively. Western blot responses developed more rapidly in the 640-micrograms group. High rates of EIA antibody responses to HIV-1 lysate were also present in both groups, and developed more rapidly in the 640-micrograms group. Enzyme immunoassay antibody responses to the immunogen (rgp160) were also frequent, but were infrequent to V3 to gp41 peptides. Neutralizing antibodies against the homologous HIV-1 LAI isolate were seen in 3 of 20 subjects (GMT = 11) who received four doses of 160 micrograms, and in 10 of 19 subjects who received four doses of 640 micrograms (GMT = 32). Fusion inhibiting antibody was not detected. CD4 blocking activity was seen in 3 of 19 subjects who received four doses of 640 micrograms. Complement-mediated antibody-dependent enhancement was found in sera from 11 of 19 volunteers in the 640-micrograms group. Lymphocyte proliferative responses to the immunogen were detected in 4 of 4 subjects tested, but no cytotoxic T cell activity was noted in 11 subjects. Administration of the 640-micrograms dose of this rgp160 vaccine candidate relative to the lower doses was associated with increased immunogenicity, including higher rates of homologous neutralizing antibody responses, although at low titer.