HIV type 1 vaccine-induced T cell memory and cytotoxic T lymphocyte responses in HIV type 1-uninfected volunteers

T cell memory to human immunodeficiency virus type 1 (HIV-1) antigens and anti-HIV-1 cytotoxic T lymphocyte (CTL) activity were assessed after administration of live canarypox virus (ALVAC) expressing HIV-1 env, gag, and protease (vCP205) vaccine given alone, vCP205 given with SF-2 recombinant gp120 (rgp120) vaccine, and placebos at 0, 1, 3, and 6 months. Healthy, HIV-1-uninfected subjects reporting high-risk and low-risk behavior for HIV-1 were enrolled. Anti-HIV-1 Env CD8(+) CTLs (HIV-1(MN) and/or HIV-1 subtype B and C primary isolate sequences) were detected in 12 (60%) and anti-HIV-1 Gag CD8(+) CTLs in 7 (35%) of the 20 vCP205 vaccine recipients tested by CTL assay 3.5 months after the final immunization. Fourteen days after the fourth immunization, lymphocyte proliferation in response to HIV-1 Gag antigen was detected in 14 (48%) of 29 vCP205 vaccine recipients, but secreted cytokine levels to HIV-1 Gag antigen were not above unstimulated levels. Coadministration of SF-2 rgp120 vaccine with vCP205 vaccine enhanced lymphocyte proliferation in response to HIV-1 envelope glycoprotein and broadened the envelope-stimulated cytokine secretion pattern, so that it consisted of both Th1 and Th2 cytokines compared with only interferon gamma (IFN-gamma) after vCP205 vaccine given alone. There was a possible association between HIV-1 envelope glycoprotein-stimulated interleukin 2 secretion and CD8(+) CTLs against HIV-1 envelope glycoprotein, and an inverse relation between lymphocyte proliferation and CTLs against HIV-1 Gag antigens. Thus, a durable anti-HIV-1 CD8(+) CTL response was detected after immunization with the live canarypox virus vaccine and preexisting helper T cell memory responses did not necessarily predict later CD8(+) CTL activity.     

Enhanced immunity to human immunodeficiency virus (HIV) envelope elicited by a combined vaccine regimen consisting of priming with a vaccinia recombinant expressing HIV envelope and boosting with gp160 protein.

Transmission studies have suggested that an optimal human immunodeficiency virus type 1 (HIV-1) vaccine should induce both neutralizing antibodies and cytolytic T cells to eliminate free virus and infected cells. A phase I trial in healthy HIV-1-seronegative persons was conducted with a combination HIV-1 vaccine regimen (strain IIIB) consisting of priming with a recombinant vaccinia (vac/env) virus expressing HIV-1 envelope and boosting with a gp160 glycoprotein derived from a recombinant baculovirus (rgp160). T-cell and antibody responses detected after immunization with either vac/env alone or rgp160 alone were generally of low magnitude and transient, and no subject developed neutralizing antibodies. In contrast, recipients of the combination regimen demonstrated in vitro T-cell proliferative responses to homologous HIV-1 antigens that were 3- to 10-fold higher than responses with either vaccine alone, and these responses were sustained for > 18 months in 75% of recipients. Moreover, both CD8+ and CD4+ cytolytic T cells were detected. Antibody responses (titer, 1:800 to 1:102,400) to homologous HIV envelope developed in all recipients of the combination regimen, and neutralizing antibodies were detected in 7 of 13. Thus, immunization with a live virus vaccine followed by boosting with a soluble protein offers promise for inducing the broad immunity needed in an HIV vaccine.     

Augmentation of HIV-1-specific T helper cell responses in chronic HIV-1 infection by therapeutic immunization

OBJECTIVE: To determine whether therapeutic immunization with a whole inactivated HIV-1 immunogen augments HIV-1-specific T helper cell responses in chronically infected individuals receiving suppressive antiretroviral therapy (ART). DESIGN: An investigator-initiated, single center, double-blind, placebo-controlled, randomized trial. METHODS: Subjects selected for study were HIV-1-infected adults on ART with an HIV-1-RNA plasma viral load of less than 500 copies/ml for at least 6 months, and a CD4 cell count greater than 250 cells/mm3 before starting ART. Study subjects were randomly assigned to receive either immunogen (inactivated envelope-depleted HIV-1 coupled with incomplete Freund's adjuvant; IFA), versus placebo (IFA alone). The primary outcome was significant CD4 cell lymphoproliferative responses to HIV-1 proteins. Secondary endpoints included HIV-1-specific CD8 T cell responses, CD4 cell count/percentage, HIV-1-RNA plasma viral load, and delayed-type hypersensitivity (DTH) responses. RESULTS: The augmentation of HIV-1-specific T helper cell responses was achieved in five out of five vaccine recipients and none out of four controls (P = 0.008, Fisher's exact test). There were no significant changes in the breadth or magnitude of cytotoxic T lymphocyte responses, CD4 cell count/percentages, or DTH test responses. CONCLUSION: HIV-1-specific T helper cell responses can be successfully increased by therapeutic immunization in individuals with chronic infection on suppressive ART. Further studies will be needed to determine whether the augmentation of these responses correlate with long-term clinical benefits.     

Safety and immunogenicity of a genetically engineered human immunodeficiency virus vaccine

A phase 1 trial of a candidate human immunodeficiency virus type 1 (HIV-1) vaccine was done in 25 healthy seronegative subjects. The antigen, env2-3 (SF2), was a nonglycosylated polypeptide representing the gp120 region of the env gene of the HIV-1(SF2) isolate. It was produced in genetically engineered yeast as a denatured molecule incapable of binding CD4. A synthetic lipophilic muramyl tripeptide (MTP-PE) was used as an adjuvant. Ten subjects received adjuvant alone and 15 received 50- or 250-micrograms doses of env2-3 (SF2) administered intramuscularly in two immunization regimens. In general, adjuvant and vaccine were well tolerated. Antibody responses to both the homologous antigen, env2-3 (SF2), and antigens from other highly divergent HIV isolates were elicited in the majority of vaccine recipients. However, antibody titers were low, without neutralizing activity. In 9 of 11 subjects who received the complete vaccine immunization series, a significant specific T lymphocyte response was observed.     

Cross-clade T lymphocyte-mediated immunity to HIV type 1: implications for vaccine design and immunodetection assays

Identifying immunodominant regions of HIV-1 that are recognized by CD8(+) T lymphocytes in infected individuals may be important for the design and evaluation of candidate HIV-1 vaccines, particularly for developing countries. In this study, cryopreserved peripheral blood mononuclear cells (PBMCs) from 15 chronically HIV-1-infected U.S. volunteers were screened for HIV-1 Gag-specific T lymphocyte interferon gamma production in an enzyme-linked immunospot (ELISpot) assay matrix format, using overlapping HIV-1 subtype A, B, and C Gag peptide pools. In the initial matrix screen, responses to HIV-1 subtype B Gag were detected in 11 of 15 (73%) of seropositive individuals and in none of 4 HIV-1-seronegative controls. There were differences in both the breadth and magnitudes of the responses observed in the matrix assay. Responses varied in breadth, ranging from broad responses (more than four peptides) of moderate magnitude (<100 spot-forming cells [SFCs]/10(5) PBMCs) to narrowly focused (two or fewer peptides), more potent responses (>150 SFC/10(5) PBMCs). Responses to A, B, and C clade peptides of HIV-1 Gag revealed that all responders to subtype B peptides were also found to recognize corresponding peptides from at least one of the other clades. The ability to recognize cross-clade peptides with one or two amino acid substitutions relative to the B clade peptide was both peptide and patient dependent. Overall, our results show that the ELISpot matrix algorithm described here may be an efficient approach for characterizing cross-clade CD8(+) T cell responses in either seropositive individuals or in seronegative HIV-1 vaccine recipients.     

Cell-mediated immune responses to autologous virus in HIV-1-seropositive individuals after treatment with an HIV-1 immunogen

OBJECTIVE: We hypothesized that cell mediated immune responses to an HIV-1 immunogen (whole-killed, gp120-depleted HIV-1 in IFA, REMUNE) would include those to autologous virus. METHODS: Five chronically HIV-1 infected individuals were examined for HIV-specific immune responses to their own virus (autologous viral antigen) after treatment with an HIV-1 immunogen. RESULTS: Subjects had low proliferative responses to HIV and p24 antigens prior to immunization and mounted strong lymphocyte proliferative responses to the immunizing HIV-1 virus, native p24, and autologous viral antigen post immunization. Similarly, subjects produced low amounts of interferon-gamma in response to HIV and p24 antigens prior to immunization and increased their interferon-gamma production in response to HIV-1, native p24, and to autologous antigen post-immunization. Furthermore, beta-chemokine responses measured as migratory inhibitory protein-1beta production were low at baseline in response to HIV-1 and native p24 antigens and were enhanced post immunization to HIV-1, native p24, and autologous antigen. CONCLUSIONS: In this study HIV-specific immune responses to autologous virus were observed after treatment with an HIV-specific immunogen.     

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.     

Immune activation and virologic response to immunization in recent HIV type 1 seroconverters.

Antigenic stimulation from invasive bacterial infections, and the vaccines designed to prevent them, may promote T cell activation and enhancement of HIV-1 replication. Changes in viral load have been correlated with antigen-specific responses. We prospectively determined the impact of immunization with 23-valent pneumococcal vaccine (PVAX) and Haemophilus influenzae type b (Hib)-modified diphtheria toxoid CRM197 (DT) vaccine on HIV-1 replication in recent HIV-1 seroconverters (n = 14; median, 5.5 months from infection; median CD4+ T cells, 535 microl), and correlated results with vaccine-related immune activation. Specific antibody responses, markers of CD4+ T cell activation (transferrin and interleukin 2 receptors), and viral burden were measured at weeks -2 (pre), 0, 1, 2, 6, and 12 after immunization. By week 2, levels of IgG had increased significantly over baseline in both HIV-1-infected patients and HIV-1-seronegative control subjects (n = 9) for each antigen (geometric mean fold rise: PVAX, 10.1 versus 5.3; Hib, 16.0 versus 11.7; and DT, 26.2 versus 24.5, respectively). Despite these vigorous responses to both polysaccharide and protein antigens, HIV-1-infected patients showed limited evidence of CD4+ T cell activation at 1 week, no consistent rise in HIV-1 burden at any point, and no decline in CD4+ T cell number over time. We conclude that recent HIV-1 seroconverters show vigorous humoral responses to vaccine antigens and limited early evidence of T cell activation, but no substantial or sustained increase in viral replication or decline in CD4+ T cell number. Thus, respiratory bacterial vaccines appear immunogenic and safe early in HIV-1 infection.     

Safety of 2 recombinant human immunodeficiency virus type 1 (HIV-1) envelope vaccines in neonates born to HIV-1-infected women.

To determine the safety of 2 candidate vaccines against human immunodeficiency virus type 1 (HIV-1), a randomized, placebo-controlled, multicenter trial compared low, medium, and high doses of the vaccines or an adjuvant among infants born to HIV-infected women. No local or systemic reactions of grade 2 or greater were reported 48 h after the subjects underwent immunization. Grade 3 or 4 chemistry toxicities occurred in 5 (3%) and grade 3 or 4 hematologic toxicities in 17 (11%) of 154 vaccinated subjects (not significantly different from 29 adjuvant recipients). CD4(+) cell percentages of < or = 20% occurred at least once in 9 vaccinated subjects and 1 control subject. Sustained CD4(+) cell percentages of < or = 20% occurred in 4 HIV-infected children. Fourteen infants (8%) were confirmed to be HIV-infected; median CD4(+) cell counts among these children were 2074, 1674, 1584, and 821 cells/mm(3) at birth and weeks 24, 52, and 104, respectively. Thus, both vaccines were safe and well tolerated in neonates, and there was no evidence of accelerated immunologic decline in HIV-infected infants.     

Human immunodeficiency virus type 1 (HIV-1) gp120-specific antibodies in neonates receiving an HIV-1 recombinant gp120 vaccine.

Infants born to human immunodeficiency virus type 1 (HIV-1)-infected mothers were immunized at birth and at ages 4, 12, and 20 weeks with low-, medium-, or high-dose recombinant gp120 vaccine with MF59 adjuvant (HIV-1(SF-2); n=52) or with MF59 alone as a placebo (n=9). An accelerated schedule (birth and ages 2, 8, and 20 weeks) was used for an additional 10 infants receiving the defined optimal dose and for 3 infants receiving placebo. At 24 weeks, anti-gp120 ELISA titers were greater for vaccine-immunized than for placebo-immunized infants on both schedules, and 87% of vaccinees had a vaccine-induced antibody response. At 12 weeks, antibody titers of infants on the accelerated vaccine schedule exceeded those of infants receiving placebo (4949 vs. 551; P=.01), and 63% of the vaccinees met the response criteria. Thus, an accelerated schedule of gp120 vaccinations generated an antibody response to HIV-1 envelope distinct from transplacental maternal antibody by age 12 weeks. These results provide support for further studies of vaccine strategies to prevent mother-to-infant HIV-1 transmission.     

Nadir CD4+ T-cell count and numbers of CD28+ CD4+ T-cells predict functional responses to immunizations in chronic HIV-1 infection

OBJECTIVE: To ascertain whether delaying the initiation of highly active antiretroviral therapy (HAART) compromises functional immune reconstitution in HIV-1 infection in persons who regain 'normal' CD4 T-cell counts after suppressive antiretroviral therapies. DESIGN: Prospective open-label study carried out at two University-affiliated HIV-outpatient clinics in the USA. SUBJECTS AND METHODS: Response to immunization was used as a model for in vivo functional immune competence in 29 HIV-1 infected patients with CD4 T-cell counts > 450 x 106 cells/l and HIV-RNA < 400 copies/ml for > 12 months after HAART and nine HIV-1 seronegative controls. After immunization with tetanus toxoid, diphtheria-toxoid, and keyhole limpet hemocyanin, immune response scores (IRS) were calculated using postimmunization antibody concentrations, lymphocyte proliferation, and delayed-type hypersensitivity responses to vaccine antigens. RESULTS: Despite normal numbers of circulating CD4 T-cells, the CD4 T-cell nadir before HAART initiation predicted the immune response to immunization (rho = 0.5; P < 0.005) while current CD4 T-cell count did not. Likewise, CD4 T-lymphocyte expression of the co-stimulatory molecule CD28 was also an independent predictor of response to immunization (rho = 0.5; P < 0.005). CONCLUSIONS: Even among persons who controlled HIV replication and normalized CD4 T-cell counts with HAART, pretreatment CD4 T-cell count and numbers of circulating CD4+CD28+ T-cells at immunization, but not current CD4 T-cell count, predict the ability to respond to vaccination. Delaying the initiation of HAART in chronic HIV-1 infection results in impaired functional immune restoration despite normalization of circulating CD4 T-cell numbers.     

Human immunodeficiency virus (HIV-1) gp160-specific lymphocyte proliferative responses of mononuclear leukocytes from HIV-1 recombinant gp160 vaccine recipients

The lymphocyte proliferative responses were studied of 12 volunteers enrolled in a phase I trial of a baculovirus-expressed recombinant human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (rgp160) vaccine. Six subjects received rgp160 and three subjects each received recombinant hepatitis B vaccine or placebo at 0, 1, and 6 months. rgp160 and a control preparation, baculovirus-expressed recombinant HIV-1 p24, were used as in vitro antigens. At day 56, all rgp160 recipients had stimulation indexes (rgp160/rp24) greater than 3.0, and five of six had differences in counts per minute (cpm) greater than 1000. Stimulation indexes were less than 2.0 and cpm differences were less than 150 in all six who did not receive rgp160. Lymphocyte proliferative responses were first noted 2 weeks to 5 months before initial Western blot reactivity and persisted for greater than or equal to 540 days, even among subjects who lost detectable antibody. Thus, the HIV-1 rgp160 vaccine induces persistent cellular immune recognition as demonstrated by lymphocyte proliferation.     

Efficacy of influenza vaccination in HIV-infected persons. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: Although influenza vaccination is recommended in persons infected with HIV-1, its efficacy is unknown. OBJECTIVE: To assess the immunogenicity, efficacy, and risks associated with influenza vaccination in persons infected with HIV-1. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Outpatient military clinic. PATIENTS: 102 patients with HIV-1 infection. INTERVENTION: Influenza vaccine (n = 55) or saline placebo (n = 47). MEASUREMENTS: Influenza antibody titers, CD4+ cell counts, and plasma HIV-1 RNA levels at baseline, 1 month after immunization, and 3 months after immunization; viral cultures from persons presenting with respiratory illness; and respiratory symptom interview. RESULTS: Twenty-three placebo recipients (49%) and 16 vaccine recipients (29%) reported respiratory symptoms (P = 0.04). Ten placebo recipients but no vaccine recipients had laboratory-confirmed symptomatic influenza (P < 0.001) (protective efficacy, 100% [95% CI, 73% to 100%]). No effect on plasma HIV-1 RNA levels or CD4+ cell counts was noted. CONCLUSION: Influenza vaccination is highly effective in HIV-1-infected persons and does not seem to be associated with substantial changes in viral load or CD4 cell count.     

Vaccine protection against HIV-2 infection in cynomolgus monkeys

The aim of this study was to determine if protection against an infectious human immunodeficiency virus type 2 (HIV-2) challenge could be obtained in cynomolgus macaques by active immunization using whole killed virus vaccine. Four monkeys were immunized with killed HIV-2SBL-6669, two of them with five intramuscular (im) injections of viral preparation containing 100 or 300 micrograms protein emulsified in incomplete Freund's adjuvant (IFA) and the two remaining received four im injections of 25-50 micrograms viral protein in iscoms. Each of the four vaccinated cynomolgus monkeys, along with four unvaccinated controls, were challenged intravenously two weeks after the last booster with approximately 100 animal infectious doses (ID50) of live HIV-2SBL-6669. All four immunized monkeys developed antibodies to HIV-2 envelope and core proteins before challenge exposure to HIV-2, but only the two animals vaccinated with virus in IFA developed detectable neutralizing antibodies. The two monkeys immunized with killed virus in IFA have shown no evidence of infection nine months after challenge with live virus. When blood and lymph node cells from these animals were transfused into naive cynomolgus monkeys, the recipients remained free of infection. In contrast, virus was recovered repeatedly in all nonimmunized animals and in the two animals immunized with iscom-associated viral antigens, which had a low content of envelope gp125 antigen. The demonstration of vaccine-induced protection against HIV-2 in a nonhuman primate raises hope for effective immunization against HIV infections in humans as well.     

Safety and immunogenicity of an HIV-1 recombinant canarypox vaccine in newborns and infants of HIV-1-infected women

Pediatric AIDS Clinical Trials Group protocol 326 is a study of 2 formulations of recombinant canarypox ALVAC vaccine (vCP205) against human immunodeficiency virus type 1 (HIV-1). HIV-1-exposed infants were randomized to receive 1 of 2 formulations of vCP205 or placebo at birth and 4, 8, and 12 weeks. The vaccines were safe. Lymphoproliferative responses were detected at > or =2 time points in 44%-56% of vaccinees and none of the placebo recipients. A cytotoxic T lymphocyte response on at least 1 occasion was detected in 62.5% of infants in cohort 1 (10(6.08) median tissue culture dose [TCID(50)] vaccine formulation) and 44% of infants in cohort 2 (10(6.33) TCID(50) vaccine formulation). Rare mucosal immunoglobulin A responses and no measurable vaccine-elicited serum antibodies were detected. In children, vCP205 appeared to be safe and immunogenic.     

Safety and immunogenicity of Bacillus Calmette-Guerin vaccine in children born to HIV-1 infected women

This prospective cohort study was conducted to determine the complication of Bacillus Calmette-Guerin (BCG) vaccination given to newborn infants born to HIV-1 seropositive mothers and to compare the tuberculin reaction 9 months after BCG vaccination between HIV-1 infected and non infected children. Two hundred and twenty-three infants with BCG immunization at birth were examined. No BCG complication was noted. Tuberculin skin tests were performed on 126 children (56.5%). Eleven of them were excluded because of failure to have skin tests read at 48 hours. Of the 115 infants enrolled to this study, 15 (13%) had no BCG scar and 50 (43.5%) had no tuberculin reaction. Twenty-six children were classified as group 1 or HIV-1 infected children and 89 children were group 2 or HIV-1 non infected. Group 1 children had a smaller tuberculin skin response (X+SD) than group 2 (1.15 +/- 2.82 vs 4.64 +/- 4.29 mm; p < 0.0001). Mean weight + SD of group 1 children was also significantly less than those in group 2 (8,013 +/- 741 vs 8,540 +/- 984 g; p < 0.05). The proportion of children with non reactivity to the tuberculin test, a negative tuberculin test and no BCG scar in group 1 was significantly higher than that in group 2 (76.9% vs 33.7%, 92.3% vs 52.8% and 36.4% vs 6.7% respectively; p < 0.0001 for all). But, the proportion of non reactivity to the tuberculin test in children with or without BCG scar of each group was not different (p > 0.05). Positive tuberculin tests were 7.7% and 47.2% in group 1 and 2 respectively. None of the children with positive tuberculin tests had clinical evidence of tuberculosis. The findings of this study indicate that BCG vaccine given to newborn infants of HIV-1 seropositive mothers is safe. Although tuberculin skin responses of HIV-1 infected children are less than those of HIV-1 non-infected children, it is possible that BCG vaccine might protect these children from developing severe tuberculosis.     

Bacillus Calmette-Guérin immunization in infants born to HIV-1-seropositive mothers

During the prospective follow-up of 64 babies at risk for perinatal HIV-1 infection because their mothers were seropositive, and of 130 control babies whose mothers were seronegative, we studied the occurrence of complications of bacillus Calmette-Guérin (BCG) immunization and its ability to induce cutaneous reactivity to tuberculin. Babies born both to HIV-1-positive and HIV-1-negative mothers received BCG immunization during their first month of life according to the Expanded Programme on Immunization (EPI) recommendations. Local and regional complications of BCG vaccine were looked for at 3, 6 and 9 months after inoculation. A tuberculin skin test was performed at 6 or 9 months of age. Most babies born to HIV-1-positive mothers were later classified as infected or uninfected according to their clinical condition and/or serological status at 18 months of age. The mean duration of the follow-up was 36 months (range 30-40 months). No chronic or deep ulcerations at the site of injection or disseminated forms of BCG infection were observed. The frequency of BCG-related lymphadenitis in the group of HIV-1-infected children (24%) did not differ significantly from the group of uninfected children (19%; Fisher test: P = 0.73). In contrast, the tuberculin skin test responses were positive less often in the group of HIV-1-infected children (33%) than in the uninfected group (83%; Fisher test: P = 0.007). Because BCG vaccine appears to be safe--even when given to perinatally infected babies--continuation of the BCG immunization policies of the EPI is justified, especially in view of the growing incidence of tuberculosis as a complication of HIV infection.     

HIV-1 MN Env 15-mer peptides better detect HIV-1 specific CD8 T cell responses compared with consensus subtypes B and M group 15-mer peptides

OBJECTIVE: To compare the ability of three Env (15-mer) peptide sets derived from the HIV-1 MN, the subtype B consensus, and the group M consensus to detect HIV-1 specific interferon (IFN)-gamma responses in HIV-1 subtype B infected subjects. METHODS: Peripheral blood mononuclear cells were obtained from 17 HIV-1 subtype B seropositive and 5 HIV-1 seronegative subjects. Peptide matrices comprising each peptide set were used in IFN-gamma Elispot assays to screen for T cell epitopes. Following matrix deconvolution, individual peptides were analyzed by IFN-gamma intracellular cytokine-staining to confirm and characterize the responding cells. RESULTS: HIV specific IFN-gamma responses were detected in 17 of 17 HIV-1 seropositive and none of 5 HIV-1 seronegative subjects by Elispot. Within the 17 HIV-1 seropositives, 16, 14, and 11 subjects responded to MN, B consensus, and group M env peptides, respectively. Responses were confirmed by intracellular cytokine analysis in 14 subjects and were in the CD3CD8 compartment. Cross-recognition of 'equivalent' peptides (i.e., peptides mapping to the same sequence region from the three peptide sets) was observed in 9 of 17 subjects. Peptide set specific responses to individual peptides were also observed; 11, 1, and 1 subjects demonstrated peptide set specific responses to MN, B consensus, and consensus group M, respectively. CONCLUSION: MN derived Env peptides were better able to detect HIV-1 specific CD8 T cell responses, many of which were not detectable by the equivalent clade or group consensus peptides. No single peptide set detected all the IFN-gamma responses within an individual. These results demonstrate the importance of reagent selection for monitoring of HIV responses in HIV-1 infected individuals and subsequently vaccine recipients.     

Enhanced sensitivity of detection of cytotoxic T lymphocyte responses to HIV type 1 proteins using an extended in vitro stimulation period for measuring effector function in volunteers enrolled in an ALVAC-HIV phase I/II prime boost vaccine trial in Thailand

A phase I/II prime-boost vaccine trial in HIV-1-seronegative adults was conducted in Thailand using ALVAC-HIV (vCP1521) as a prime, boosting with either oligomeric gp160 TH023/LAI or Chiron HIV Thai subtype E (CM235) plus U. S. subtype B (SF2) gp120. Cytotoxic T lymphocyte (CTL) assays were conducted at one of the vaccine trial sites (Siriraj Hospital) at a single time point following the completion of immunization demonstrated that 8 of 50 (16%) vaccine recipients showed HIV-specific CTL by standard chromium release assay (CRA) after in vitro stimulation (IVS) for 2 weeks. Five additional vaccinees (13/50 = 26%) showed CTL responses after IVS for up to 4 weeks. Moreover, one volunteer with a positive CTL response to a single HIV antigen at Day 14 demonstrated a response to an additional HIV-1 antigen(s) after the longer IVS period. CTL activity was CD8+ restricted. Despite extension of the IVS up to 4 weeks, no CTL responses were detected in placebo recipients. These results imply that extension of the IVS period may increase the sensitivity of the CRA when measuring HIV-specific CTL in ALVAC-HIV prime-boost recipients without compromising specificity.