A canarypox vaccine expressing multiple human immunodeficiency virus type 1 genes given alone or with rgp120 elicits broad and durable CD8+ cytotoxic T lymphocyte responses in seronegative volunteers

Induction of CD8+ cytotoxic T cells is considered one of the important correlates for the protective efficacy of candidate human immunodeficiency virus type 1 (HIV-1) vaccines. To induce CD8+ cytotoxic T lymphocytes (CTLs) along with neutralizing antibody and CD4+ T cell help, a live canarypox virus construct expressing gp120, transmembrane gp41, the gag and protease genes, and sequences containing CTL epitopes in nef and pol was given simultaneously with, or followed by, rgp120 SF2. CD8+ CTLs were detected in 61% of volunteers at some time during the trial. Three to 6 months after the last immunization, the gene-specific responses were gag, 26/81; env, 17/77; nef, 12/77; and pol, 3/16. Simultaneous immunization with the canarypox vector and the subunit, beginning with the initial immunization, resulted in earlier antibody responses. In summary, a strategy of immunization with a canarypox vector expressing multiple genes of HIV-1 given with gp120 results in durable CD8+ CTL responses to a broad range of epitopes.

Early and persistent human immunodeficiency virus type 1 (HIV-1)-specific T helper dysfunction in blood and lymph nodes following acute HIV-1 infection

Without potent antiretroviral therapy, most human immunodeficiency virus type 1 (HIV-1)-infected persons experience a progressive decline in CD4+ T cells and impairment in T helper function. It is unclear how soon after infection T cell dysfunction occurs. T helper responses were examined in blood and lymphoid tissue of 39 untreated patients with acute HIV-1 infection. Within the first 3 months, lymphoproliferative responses to mitogen, recall antigens, and HIV-1 antigens were impaired. After 6-9 months, responses to phytohemagglutinin and recall antigens improved. However, HIV-1-specific lymphoproliferation remained largely undetectable throughout 2 years of infection, and results were similar upon evaluation of lymphoid cells. Rare patients with HIV-1-specific responses had significantly lower plasma HIV-1 RNA levels than did nonresponders. These results indicate that T helper dysfunction occurs early after HIV-1 acquisition and that untreated individuals rarely recover HIV-specific helper responses; these findings lend support for early therapeutic intervention to prevent the destruction and further impairment of the T helper cells.

Dendritic cell-T-cell interactions support coreceptor-independent human immunodeficiency virus type 1 transmission in the human genital tract

Worldwide, human immunodeficiency virus (HIV) is transmitted predominantly by heterosexual contact. Here, we investigate for the first time, by examining mononuclear cells obtained from cervicovaginal tissue, the mechanisms whereby HIV type 1 (HIV-1) directly targets cells from the human genital tract. In contrast to earlier findings in mucosal models such as human skin, we demonstrate that the majority of T cells and macrophages but none or few dendritic cells (DC) express the HIV-1 coreceptor CCR5 in normal human cervicovaginal mucosa, whereas all three cell types express the coreceptor CXCR4. To understand the role of coreceptor expression on infectivity, mucosal mononuclear cells were infected with various HIV-1 isolates, using either CCR5 or CXCR4. Unstimulated T cells become rapidly, albeit nonproductively, infected with R5- and X4-tropic variants. However, DC and T cells form stable conjugates which permit productive infection by viruses of both coreceptor specificities. These results indicate that HIV-1 can exploit T-cell-DC synergism in the human genital tract to overcome potential coreceptor restrictions on DC and postentry blocks of viral replication in unactivated T cells. Thus, mononuclear cells infiltrating the genital mucosa are permissive for transmission of both R5- and X4-tropic HIV-1 variants, and selection of virus variants does not occur by differential expression of HIV-1 coreceptors on genital mononuclear cells.

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.

Protection against human immunodeficiency virus type 1 infection in persons with repeated exposure: evidence for T cell immunity in the absence of inherited CCR5 coreceptor defects

It has been hypothesized that protection against human immunodeficiency virus (HIV)-1 infection may result from either acquired host immunity, inheritance of a dysfunctional CCR5 HIV-1 coreceptor, or a low or attenuated virus inoculum. Thirty-seven HIV-1-uninfected persons engaging in repeated high-risk sexual activity with an HIV-1-infected partner were prospectively studied to determine the contribution of these factors in protecting against HIV-1 transmission. More than one-third (13/36) demonstrated HIV-1-specific cytotoxicity, and this activity significantly correlated with the wild type CCR5 genotype (P=.03). Only 1 subject (3%) demonstrated the homozygous CCR5 32-bp deletion (Delta32/Delta32). Median plasma HIV-1 RNA levels from 18 HIV-1-infected sex partners were not statistically different from those of matched infected control patients. These results indicate that inheritance of the Delta32 CCR5 mutation does not account for the majority of persistently HIV-1-resistant cases, and the presence of cellular immunity in these persons suggests either undetected infection or protective immunity.

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.

Preventing discrimination against volunteers in prophylactic HIV vaccine trials: lessons from a phase II trial

CONTEXT

Preventive HIV vaccines can temporarily cause uninfected individuals to have positive results on HIV testing. As preparations are underway to mount larger efficacy trials, the social risks of trial participation should be studied.

OBJECTIVE

To describe frequency of HIV testing and discrimination among participants in a preventive phase II HIV vaccine trial.

PARTICIPANTS

266 vaccine trial volunteers were eligible; 247 participated in a confidential survey.

RESULTS

63 volunteers (26% of respondents) reported 185 HIV tests during the prior 12 to 24 months; most tests were for other research studies, health care, insurance, incarceration, or employment. Only 5 volunteers reported having positive HIV test results. Volunteers reported 99 adverse social incidents or problems, 53 of which were related to the trial. The most common type of event occurred when volunteers disclosed their trial participation and were mistakenly presumed to be infected with HIV. Few reported difficulty obtaining insurance, job loss, and inadvertent disclosure of their participation in the trial.

CONCLUSION

In this vaccine trial, few serious social harms were reported. Those who conduct HIV tests for insurance, employment, health care, or other reasons should be made aware that HIV vaccines can cause false-positive HIV test results. Those planning future trials must continue to provide needed support to volunteers. Social harms should be monitored with the same vigilance accorded to physical harms.

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.

Immune responses to human immunodeficiency virus (HIV) type 1 induced by canarypox expressing HIV-1MN gp120, HIV-1SF2 recombinant gp120, or both vaccines in seronegative adults. NIAID AIDS Vaccine Evaluation Group

A safety and immunogenicity trial was conducted in vaccinia-immune and vaccinia-naive human immunodeficiency virus (HIV)-uninfected adults who were randomized to receive 10(6) or 10(7) TCID50 of canarypox (ALVAC) vector expressing HIV-1MN gp160 or 10(5.5) TCID50 of ALVAC-rabies virus glycoprotein control at 0 and 1 or 2 months and ALVAC-gp160 or 50 microg of HIV-1SF2 recombinant (r) gp120 in microfluidized emulsion at 9 and 12 months; others received rgp120 at 0, 1, 6, and 12 months. All vaccines were well-tolerated. Neither vaccinia-immune status before vaccination nor ALVAC dose affected HIV immune responses. HIV-1MN and HIV-1SF2 neutralizing antibodies were detected more often (100%) in ALVAC-gp160/rgp120 recipients than in recipients of ALVAC-gp160 (<65%) or rgp120 (89%) alone. ALVAC-gp160/rgp120 also elicited more frequent HIV V3-specific and fusion-inhibition antibodies, antibody-dependent cellular cytotoxicity, lymphoproliferation, and cytotoxic CD8+ T cell activity than did either vaccine alone. Trials with ALVAC expressing additional HIV components and rgp120 are underway.

Modulation of immunologic responses to HIV-1MN recombinant gp160 vaccine by dose and schedule of administration. National Institute of Allergy and Infectious Diseases AIDS Vaccine Evaluation Group

The safety and immunogenicity of HIV-1MN recombinant gp160 (MN rgp160) vaccine in healthy, uninfected volunteers was tested in a double-blind study with a factorial design. By random assignment, 20 volunteers received three 200 micrograms doses of MN rgp160 and four volunteers received placebo at days 0, 28, and 168 or 0, 56, and 224. Of the 24 volunteers, 16 received 200 micrograms or 800 micrograms of MN rgp160 and two received placebo at day 532 (month 18). The vaccine was safe. It induced T cell memory measured by Th1 cytokine production and lymphocyte proliferation, and serum anti-MN rgp160 IgG (all subclasses) and IgA antibodies. Fifteen of 20 vaccinees developed neutralizing antibody. The regimen including immunizations on days 0, 28, and 168 followed by the 800 micrograms fourth dose was most immunogenic.

Cytotoxic T cell and neutralizing antibody responses to human immunodeficiency virus type 1 envelope with a combination vaccine regimen. AIDS Vaccine Evaluation Group

Effective human immunodeficiency virus (HIV) vaccination may require induction of neutralizing antibodies (NAs) and CD8+ cytotoxic T lymphocytes (CTL) to prevent transmission and control early infection. Recombinant envelope proteins induce NAs but rarely CD8+ CTL responses, and vaccinia vectors containing HIV-1 envelope elicit CD8+ cytotoxicity but few NAs. To benefit from both approaches, 56 vaccinia-naive subjects were randomized to a regimen of priming with recombinant vaccinia gp160LAI and boosting with recombinant gp120SF-2, gp120LAI, gp120MN, or gp160MN. Of 51 persons for whom assays were done, 26 demonstrated envelope-specific CTL. Boosting with gp120, compared with gp160, elicited significantly more NAs and CD4-blocking antibodies. Neutralization of the homologous and heterologous HIV-1 laboratory strains occurred in all subjects receiving vac/env and gp120 and was detectable in 91% of the subjects for >6 months. Thus, vaccine regimens in which one component elicits primarily CTL and the other NAs offer promise for the development of an effective HIV-1 vaccine strategy.

Analysis of intercurrent human immunodeficiency virus type 1 infections in phase I and II trials of candidate AIDS vaccines. AIDS Vaccine Evaluation Group, and the Correlates of HIV Immune Protection Group

Among 2099 uninfected subjects in phase I and II trials of candidate AIDS vaccines, 23 were diagnosed with intercurrent human immunodeficiency virus type 1 (HIV-1) infection. High-risk sexual exposures accounted for 17 infections, and intravenous drug use accounted for 6. Four subjects received placebo, 13 received a complete immunization schedule (> or = 3 injections), and 6 were partially immunized (< or = 2 injections). There was no significant difference between vaccine recipients and control groups in incidence of HIV-1 infection, virus load, CD4 lymphocyte count, or V3 loop amino acid sequence. In summary, 19 vaccinated subjects acquired HIV-1 infection during phase I and II trials, indicating that immunization with the products described is < 100% effective in preventing or rapidly clearing infection. Laboratory analysis suggested that vaccine-induced immune responses did not significantly affect the genotypic or phenotypic characteristics of transmitted virus or the early clinical course of HIV-1 infection.

Cytotoxic-T-cell responses, viral load, and disease progression in early human immunodeficiency virus type 1 infection

BACKGROUND

Early in human immunodeficiency virus type 1 (HIV-1) infection there is a decline in viral replication that has been attributed to host immunity, but the components of this response, particularly the ability of cytotoxic T lymphocytes to control viral burden and influence the outcome of disease, are poorly understood.

METHODS

We prospectively studied 33 patients with primary HIV-1 infection for HIV-specific activated cytotoxic T lymphocytes and memory cytotoxic T lymphocytes and compared these lymphocyte responses with changes in viral load and clinical status over the subsequent 18 to 24 months.

RESULTS

Soon after infection, activated HIV-specific cytotoxic T lymphocytes, mediated primarily by CD8+ cells, were detected in 17 of 23 patients (74 percent). Memory cytotoxic T lymphocytes were found in 6 of 6 patients tested (100 percent) during the first three months of infection and in 17 of 21 patients (81 percent) tested during the first six months. The frequencies of memory cytotoxic T lymphocytes varied markedly over time, but overall they declined over the first 6 to 8 months and then stabilized over the next 12 to 18 months. The patients with higher frequencies of Env-specific memory cytotoxic T lymphocytes had a median level of plasma HIV-1 RNA about one third that of the patients with lower frequencies, (median number of RNA copies per milliliter, 22,000 vs. 62,000; P=0.006). Patients with low frequencies of Env-specific memory cytotoxic T lymphocytes (or none) in early infection had a more rapid decline to less than 300 CD4+ cells per cubic millimeter (P = 0.05).

CONCLUSIONS

In early HIV-1 infection, the induction of memory cytotoxic T lymphocytes, particularly those specific for Env, helps control viral replication and is associated with slower declines in CD4+ cell counts. Host cytolytic effector responses appear to delay the progression of HIV-1 disease.

Safety profile of phase I and II preventive HIV type 1 envelope vaccination: experience of the NIAID AIDS Vaccine Evaluation Group

The NIAID-sponsored AIDS Vaccine Evaluation Group was established in 1988 to perform phase I/II clinical trials with candidate preventive HIV-1 vaccines. This report includes safety data from 1398 HIV-negative, healthy volunteers who were enrolled into 25 phase I and 1 phase H multicentered, randomized, double-blind studies evaluating seven recombinant HIV-1 envelope vaccines, two V3 loop synthetic peptide vaccines, and two live poxvirus-vectored recombinant envelope vaccines. All studies but three were placebo controlled; the placebo was either the adjuvant alone or, in studies of recombinant poxvirus vaccines, it was the vector with no gene insert or a non-HIV gene insert. All candidate vaccines were generally well tolerated. The only adverse effects that were clearly related to vaccination were occasional acute local and systemic reactions that were associated with the adjuvants. Three adjuvants in particular were associated with moderate to severe local reactions: alum plus deoxycholate (ImmunoAg), MTP-PE (Biocine Corp.), and QS21 (Genentech, Inc.). MTP-PE was also associated with self-limited severe systemic reactions. There were no serious adverse laboratory toxicities and no evidence of significant immunosuppressive events after receipt of the candidate vaccines. A few volunteers experienced symptoms that might relate to an underlying immunopathologic mechanism (rash, hemolytic anemia, arthralgia), but their presentations were mild and their incidence was low. Eleven volunteers were diagnosed with malignancies during or after their participation, which was within the 95% confidence interval of the number of cases predicted by the National Cancer Institute SEER (Program for cancer surveillance, epidemiology, and end result reporting) database. In conclusion, the envelope-based recombinant or synthetic candidate HIV-1 vaccines appear to be safe and this work has prepared the way for the testing of increasingly complex candidate HIV-1 vaccines.

Divergent patterns of progression to AIDS after infection from the same source: human immunodeficiency virus type 1 evolution and antiviral responses

The rate of progression to AIDS in human immunodeficiency virus type 1 (HIV-1)-infected individuals is determined by a complex series of interactions between the host and virus. Here we evaluate virologic properties and host responses in two men near-simultaneously infected with HIV-1 from the same sexual partner--one individual progressed to AIDS in less than 2 years, and the other remains asymptomatic 3 years postinfection. Distinct neutralizing antibody and cellular immune responses were evident, with the slower progressor exhibiting generally stronger and broader responses, except for cytotoxic T-lymphocyte responses early in infection. Virtually identical, homogeneous virus populations were found in both patients in the first sample obtained; however, a second unrelated HIV-1 virus population was also found in the fast progressor. Whether the second population emanated from an additional source of infection or the two were transmitted from the original source could not be determined. The virus population in the slower progressor turned over and diversified rapidly, whereas both virus populations in the rapid progressor evolved at a much slower rate. In addition, the character of mutational changes underlying these diversities appeared to be distinct, with a bias for diversifying selection developing in the slower progressor and a reciprocal bias towards purifying selection maintained in both populations in the fast progressor. Thus, the rapid evolution that is a hallmark of HIV replication may be a reflection of strong host resistance against emerging virus variants and a longer period of asymptomatic infection. Furthermore, rapid progression was not linked to a collapse of any appreciable immune response following attainment of some threshold of antigenic diversity but rather to a failure to drive this diversification and a condition of relatively unimpeded expansion of variants with optimized replicative capacity within the host.

Neutralization of a clade B primary isolate by sera from human immunodeficiency virus-uninfected recipients of candidate AIDS vaccines

The inability of antibodies induced by experimental human immunodeficiency virus type 1 (HIV-1) vaccines to neutralize HIV-1 primary isolates may be due to a failure to elicit such antibodies, antigenic differences between the vaccine and the strains tested, insensitivity of the assays used, or to a combination of factors. New neutralization assays were used to determine the ability of candidate AIDS vaccines to generate neutralizing antibodies for clade B primary isolate BZ167, which is closely related in portions of its envelope to the immunizing strains. Sera from HIV-uninfected volunteers in vaccine trials were tested, and neutralizing activity was found in recipients of recombinant (r) gp120MN or of rgp160MN-containing canarypox boosted with rgp120SF-2. Detection of antibodies that neutralize primary isolate BZ167 correlated with neutralizing activity for homologous vaccine strains. These data demonstrate that certain candidate AIDS vaccines can elicit antibodies that neutralize a primary isolate of HIV-1.

Clade B-based HIV-1 vaccines elicit cross-clade cytotoxic T lymphocyte reactivities in uninfected volunteers

A fundamental goal of current strategies to develop an efficacious vaccine for AIDS is the elicitation of broadly reactive cytotoxic T lymphocyte (CTL) reactivities capable of destroying virally infected targets. Recent application of recombinant canarypox ALVAC/HIV-1 vectors as vaccine immunogens in HIV-1,-noninfected volunteers has produced CTL responses in a significant number of vaccinees. Using a newly developed targeting strategy, we examined the capacity of vaccine-induced CTL to lyse autologous targets infected with a diverse group of viral isolates. CTL derived from recipients of a canarypox ALVAC/HIV-1 gp160 (MN) vaccine were found capable of lysing autologous CD4+ lymphoblasts infected with the prototypic LAI strain of HIV-1. When tested against autologous targets infected with primary HIV-1 isolates representing genetically diverse viral clades, CTL from ALVAC/gp160 recipients showed both a broad pattern of cytolysis in which viruses from all clades tested were recognized as well as a highly restricted pattern in which no primary isolates, including clade B, were lysed. Differences in the HLA haplotypes of the volunteers immunized with the envelope vector might be a major determinant of the relative breadth of their CTL response. In contrast to ALVAC/gp160 vaccinees, recipients of the ALVAC/HIV-1 immunogen containing envelope as well as gag and protease genes consistently had CTL reactivities effective against a spectrum of primary isolate-infected targets. These studies demonstrate for the first time that clade B-based canarypox vaccines can elicit broad CTL reactivities capable of recognizing viruses belonging to genetically diverse HIV-1 clades. The results also reinforce the impact of viral core elements in the vaccine as well as the pattern of major histocompatibility complex class I allelic expression by the vaccine recipient in determining the relative breadth of the cellular response.

Longitudinal analysis of quantitative virologic measures in human immunodeficiency virus-infected subjects with > or = 400 CD4 lymphocytes: implications for applying measurements to individual patients. National Institute of Allergy and Infectious Diseases AIDS Vaccine Evaluation Group

The natural variability of quantitative virologic measures among human immunodeficiency virus (HIV) type 1-infected persons was prospectively studied in 29 untreated persons with >600 CD4 cells/microL and in 15 persons receiving zidovudine monotherapy who had 400-550 CD4 cells/microL at study entry. Cell- and plasma-associated infectious HIV-1, provirus, and virion RNA were determined monthly as were numbers of CD4 and CD8 cells. HIV-1 replication varied widely among subjects with similar CD4 cell counts. The within-individual variability was significantly less than the variability between subjects for all virologic measures. Plasma virion HIV-1 RNA levels had the least variability. A mathematical model was devised to assess whether a potential therapeutic intervention significantly alters peripheral HIV-1 load. The model indicated that three measurements of plasma RNA would be outside the 95th percentile for the expected change in an individual due to natural variability. This approach can be used to accurately assess a therapeutic intervention among persons with low plasma HIV-1 titers.

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.

Antagonism of vaccine-induced HIV-1-specific CD4+ T cells by primary HIV-1 infection: potential mechanism of vaccine failure

Prior immunity to HIV-1 elicited by vaccination may modify subsequent responses upon exposure to infectious HIV-1. An HIV-1-uninfected person entered in a vaccine trial that included immunizations to HIV-1(LAI) envelope with a recombinant vaccinia vector and recombinant protein developed envelope-specific CD4+ T cell responses, including proliferative and cytolytic responses, but was not protected from a high risk HIV-1 exposure. CD4+ T cell clones derived from blood at the peak of vaccine-induced immunity recognized and lysed autologous target cells expressing four distinct regions within the HIV-1(LAI) envelope region; three of these CTL clones also recognized targets expressing envelope from a similar viral subtype, HIV-1(MN). The epitope specificity of CD4+ clone 9G8, recognizing both HIV-1(LAI) and HIV-1(MN) envelope, was within the 571-590 amino acid envelope region. Sequence analysis of the first infectious autologous strain revealed two amino acid mutations within this region. The 9G8 CTL clone induced by immunization failed to recognize targets expressing the corresponding CTL epitope from the infecting virus. Moreover, a peptide based on the epitope sequence of the infecting isolate antagonized the vaccine-induced CTL clone such that the CTL clone was no longer able to recognize the vaccine strain or HIV-1(MN) epitope. These findings suggest a potentially novel mechanism associated with vaccine failure whereby the infecting virus may not only escape from CTL activity, but also alter the ability of CTL to recognize other variants in an individual.

Antagonism of vaccine-induced HIV-1-specific CD4+ T cells by primary HIV-1 infection: potential mechanism of vaccine failure

Prior immunity to HIV-1 elicited by vaccination may modify subsequent responses upon exposure to infectious HIV-1. An HIV-1-uninfected person entered in a vaccine trial that included immunizations to HIV-1(LAI) envelope with a recombinant vaccinia vector and recombinant protein developed envelope-specific CD4+ T cell responses, including proliferative and cytolytic responses, but was not protected from a high risk HIV-1 exposure. CD4+ T cell clones derived from blood at the peak of vaccine-induced immunity recognized and lysed autologous target cells expressing four distinct regions within the HIV-1(LAI) envelope region; three of these CTL clones also recognized targets expressing envelope from a similar viral subtype, HIV-1(MN). The epitope specificity of CD4+ clone 9G8, recognizing both HIV-1(LAI) and HIV-1(MN) envelope, was within the 571-590 amino acid envelope region. Sequence analysis of the first infectious autologous strain revealed two amino acid mutations within this region. The 9G8 CTL clone induced by immunization failed to recognize targets expressing the corresponding CTL epitope from the infecting virus. Moreover, a peptide based on the epitope sequence of the infecting isolate antagonized the vaccine-induced CTL clone such that the CTL clone was no longer able to recognize the vaccine strain or HIV-1(MN) epitope. These findings suggest a potentially novel mechanism associated with vaccine failure whereby the infecting virus may not only escape from CTL activity, but also alter the ability of CTL to recognize other variants in an individual.

Safety and immunogenicity of a candidate HIV-1 vaccine in healthy adults: recombinant glycoprotein (rgp) 120. A randomized, double-blind trial. NIAID AIDS Vaccine Evaluation Group

OBJECTIVE

To evaluate the safety and immunogenicity of recombinant glycoprotein (rgp) 120, a candidate vaccine for the human immunodeficiency virus (HIV), formulated with a novel adjuvant, MF59, with or without a biological response modifier, MTP-PE.

DESIGN

Multicenter, double-blind, randomized trial.

SETTING

University medical centers.

PARTICIPANTS

49 healthy, HIV-seronegative volunteers 18 to 60 years of age who were at low risk for HIV type 1 (HIV-1) infection.

INTERVENTIONS

In part A of the study, 32 participants were randomly assigned to receive either 15 micrograms of rgp 120 in MF59, 15 micrograms of rgp 120 in MF59 plus 50 micrograms of MTP-PE, 50 micrograms of rgp 120 in MF59, or 50 micrograms of rgp 120 in MF59 plus 50 micrograms of MTP-PE. Participants were vaccinated at 0, 1, 6, and 12 to 18 months. In part B, 17 participants were randomly assigned to receive five monthly injections of either 50 micrograms of rgp 120 in MF59 or MF59 alone followed by a booster injection at 12 to 18 months.

MAIN OUTCOME MEASURES

Local and systemic reactions; laboratory measures of hepatic, renal, immunologic, and bone marrow toxicity; and HIV-specific serologic and cell-mediated immune responses.

RESULTS

13 patients in part A received 50-micrograms doses of rgp 120; type-specific neutralizing antibody responses against the SF-2 strain of HIV-1 (HIV-1/SF-2) were induced in all 13. Nine of the 13 had crossreactive neutralizing activity against the MN strain of HIV-1 (HIV-1/MN), and 2 had crossreactive neutralizing activity against the IIIB strain of HIV-1 (HIV-1/IIIB). Twelve patients had typespecific fusion inhibition activity; only 1 had crossreactive fusion inhibition activity against HIV-1/MN. The monthly vaccination schedule used in part B resulted in decreased antibody titers, indicating that a rest period in the schedule is necessary for maximal immunogenicity. Lymphoproliferative responses against gp120 were induced in all vaccine recipients. The stimulation index to gp120 was persistently greater than 15 for 6 months after the last booster vaccination was given. CD8+ cytotoxic T-lymphocyte activity was detected in 1 of the 11 participants tested. Vaccine that contained MTP-PE caused a greater number of moderate or severe local and systemic reactions (of 16 participants, 4 had local reactions and 13 had systemic reactions) than did vaccine formulated with MF59 alone (of 16 participants, 7 had local reactions [P < 0.01] and 0 had systemic reactions [P < 0.001]).

CONCLUSIONS

The SF-2 rgp120 vaccine is safe and immunogenic. Three vaccinations with rgp120 in MF59 can induce type-specific and crossreactive neutralizing antibody against B-subtype laboratory strains of HIV-1. Human immunodeficiency virus-specific lymphoproliferative responses were induced in all vaccinated participants, and CD8+ cytotoxic T-lymphocyte activity was shown in one participant. A trend toward the augmentation of lymphoproliferative and humoral responses by MTP-PE was seen in the participants receiving 15 micrograms of rgp120. However, MTP-PE caused a statistically significant increase in the incidence of local and systemic side effects, which was felt to outweigh the small increase in immunogenicity provided by this biological response modifier in an otherwise well-tolerated vaccine.