Faculty Bibliography

BACKGROUND:A goal of T-cell HIV vaccines is to define the correlation between a vaccine-induced immune response and protection from HIV infection. We conducted a phase 2 trial to determine if a canarypox vaccine candidate (vCP1452) administered with rgp120 subunit protein would "qualify" for a trial to define a correlate of efficacy. METHODS:A total of 330 healthy volunteers were enrolled into 4 groups: 120 received vCP1452 alone (0, 1, 3, and 6 months), 120 received vCP1452 with 2 different regimens of rgp120 coadministration, and 90 received placebo. HIV-specific antibody responses were measured by enzyme-linked immunoassay (ELISA) and neutralizing activity. T-cell responses were measured by chromium release and interferon-gamma (IFNgamma) enzyme-linked immunospot (ELISpot) assay. RESULTS:Significant neutralizing antibody responses to the HIV MN strain were detected in all vaccine groups, with net responses ranging from 57% (95% confidence interval [CI]: 40% to 71%) to 94% (95% CI: 85% to 99%). Net cumulative HIV-specific CD8 IFNgamma ELISpot assay responses were 13% (95% CI: -1% to 26%) for recipients of vCP1452 alone and 16% (95% CI: 2% to 29%) for recipients of vCP1452 plus rgp120. CONCLUSIONS:Overall, the HIV-specific CD8 cytotoxic T lymphocyte (CTL) response was not sufficient to qualify the regimen for a subsequent trial designed to detect an immune correlate of protection requiring a minimum CD8 CTL frequency of 30%.

The importance of host cellular immune responses, particularly CD8(+) cytotoxic T-lymphocyte (CTL) responses, in control of human immunodeficiency virus type 1 (HIV-1) infection has been demonstrated in many clinical studies. These studies, along with vaccination challenge studies in rhesus macaques, indicate the importance of cellular immune responses against HIV-1. Toward this end, we evaluated anti-HIV-1 cellular immune responses in a cohort of 54 subjects who were chronically infected with HIV-1. By validation of IFN-gamma ELISpot assay, we established a dual cut-off criterion for scoring a positive response. The magnitude and frequency of cellular immune responses were measured against HIV-1 antigens (Gag, Pol, Nef, Rev, and Tat), using synthetic peptides as antigens in ELISpot assay. Here we showed that HIV-1 Gag, Pol, and Nef were frequent targets of T cell responses in these subjects, whereas Tat and Rev were less frequently recognized. We further evaluated the possible association between host cellular immune responses and corresponding plasma viral loads in this cohort. By performing ranking correlation analysis, we demonstrated a positive correlation between host viral loads and ELISpot responses of HIV Gag and Pol in untreated subjects. For the subjects under antiviral regimens, however, we did not find any significant association. Our findings suggest that the high levels of ELISpot responses in chronically infected subjects were reflective of their persistent viral infection.

The HIV/AIDS pandemic continues to challenge the African American community with disproportionate rates of infection, particularly among young women ages 25 to 34 years. Development of a preventive HIV vaccine may bring a substantial turning point in this health crisis. Engagement of the African American community is necessary to improve awareness of the effort and favorably influence attitudes and referent norms. The Theory of Reasoned Action (TRA) may be a useful framework for exploration of community engagement outcomes including future attendance, community mobilization, and study participation. Within the context of HIV vaccine outreach, we conducted a cross-sectional survey in early 2007 with 175 African-American adults (>/= 18 years). Confirmatory factor analysis and structural equation modeling were performed and the findings support the potential of the model in understanding behavioral intentions toward HIV vaccine research.

OBJECTIVE:To understand the mechanisms underlying the differential targeting of T-cell responses during HIV-1 disease progression. DESIGN/METHODS:We performed a cross-sectional analysis of HIV specific CD8 T-cell responses in peripheral blood mononuclear cells (PBMC) obtained from 21 subjects with well characterized acute or early infection and 88 subjects with chronic HIV-1 infection. We also performed a longitudinal analysis of T-cell responses in five early infected subjects one of whom was studied extensively over a 4-year-period. METHODS:PBMC were stimulated with pools of peptides encompassing all of the HIV-1 proteins in an interferon-gamma ELISpot assay. A mean entropy score was calculated for each peptide in the HIV-1 genome. RESULTS:The early infected group preferentially targeted variable peptides with higher entropy while responses towards more conserved peptides with lower entropy predominated in the group with chronic infection. In five early infected subjects followed longitudinally, responses to variable proteins declined while those to conserved proteins increased over time. In the subject who was followed for 4 years, epitopes in Vif and Nef were targeted early and escape occurred in three of these four epitopes. During the chronic phase of his infection, the early responses waned with an associated increase in breadth of T-cell responses mainly to Gag and Pol epitopes. CONCLUSION/CONCLUSIONS:Taken together, these data demonstrate that HIV-specific CD8 T cells are directed preferentially to the variable peptides in early infection but diminish in frequency during chronic disease, in large part due to cytotoxic T lymphocyte escape.

Candidate human immunodeficiency virus (HIV)-1 vaccines that elicit cytotoxic T lymphocytes may modulate HIV infection, requiring a prototype evaluation to assess participants who become infected with HIV. Of 1497 participants in canarypox HIV-1 vaccine prime-boost trials, 28 (1.9%) acquired HIV-1 infection after vaccination. Median plasma HIV-1 RNA levels (vaccinees, 4.78 log10 copies/mL; placebo recipients, 4.27 log10 copies/mL) and CD4 cell counts (vaccinees, 552 cells/mm3; placebo recipients, 657 cells/mm3) before administration of antiretroviral therapy (ART) and time to a composite end point (plasma HIV-1 RNA level >55,000 copies/mL, CD4 cell count <350 cells/mm3, or initiation of ART) did not differ significantly between vaccinees and placebo recipients (P =.4, P =.1, and P =.7, respectively). Persons who acquire HIV-1 infection while enrolled in HIV-1 vaccine trials can be successfully followed after infection, to determine whether vaccines alter the course of HIV-1 infection.

This study was undertaken to resolve existing controversies with respect to the detection of IgA HIV-1-specific mucosal antibodies in infected individuals. External secretions, including tears, nasal, rectal, and vaginal washes, saliva, semen, urine, and sera were obtained from 50 HIV-1-infected individuals and 20 controls using collection procedures that minimize the irritation of mucosal surfaces. Levels of total and antigen (gp120 and gp160)-specific antibodies of the IgG and IgA isotypes were measured by assays that proved reliable in a large multicenter study: quantitative ELISA and chemiluminescence-enhanced Western blot analyses. Although the levels of total IgG and IgA were increased or remained unchanged in body fluids of HIV-1-infected individuals as compared to the controls, HIV-1-specific IgA antibodies were either absent or present at low levels even in secretions with characteristically high relative contents of total IgA vs. IgG (saliva, tears, and rectal and nasal washes). In these secretions, HIV-1-specific IgG antibodies dominated. In assessing levels and frequency of detection of IgG antibodies, both female and male genital tract secretions, urine, and nasal wash were preferable to parotid saliva and especially to rectal wash. External secretions contained IgG antibodies to gp160> gp120> gp41 and p24; when present, IgA antibodies were predominantly directed at gp160. Analyses of peripheral blood antibody-secreting cells (ASC) isolated from the same individuals paralleled these serological findings: gp160-specific IgG-secreting ASC were dominant. Therefore, in striking contrast to other mucosally encountered microbial infections, HIV-1 does not induce vigorous specific IgA responses in any body fluid examined or in ASC in peripheral blood.

African-Americans (AFAM) and Hispanics (HIS) represent only 13% and 12% of the U.S. population but 54% and 19%, respectively, of annually incident HIV-1 infections in the United States. The 88 patients in the current study were from U.S. racial or ethnic minority groups (72% African-American, 17% Hispanic), female (85%), and adolescent (mean age 20 years). Their HLA allele distributions were distinct from patterns in U.S. whites. Overall, HIV-1-specific T cell responses were observed in 91% of participants: 75% recognized peptides in Gag, 67% Pol, 57% Nef, and 41% Env. The patients recognized 87 (36%) of 244 Gag, Pol, Env, or Nef peptides tested. Similar to what has been seen in white cohorts, epitope-rich peptide clusters were identified within conserved functional domains in Gag matrix, Gag capsid, Pol reverse transcriptase, and Nef. Peptides representing variable regions from within the B subtype or with more changes from the B subtype consensus sequence were less likely to stimulate a positive T cell response. A small percentage (17%) of unique T cell responses was found in this cohort that displayed no previously known T cell epitopes. Dominant responses generally overlapped with epitope-rich regions in HIV-1 described previously for whites, although many of these peptides were likely restricted by HLA class I alleles not previously associated with these epitopes. Hence host genetic variation among different racial groups may have less impact on the utility of candidate HIV-1 vaccines than previously suspected.

Vaccines designed to bring forth CD8+ T cell responses in different racial and ethnic groups will require inclusion of T cell epitopes presented by various MHC class I molecules. This study was designed to identify new CD8+ T cell epitopes in HIV-infected African American and Hispanic youth as well as to determine the frequency of responses to both novel and previously described HIV-1 epitopes in a cohort of racially and ethnically diverse individuals. We found 8 MHC class I-restricted CD8+ T cell epitopes that had not been previously described, another 8 epitopes that were restricted by class I alleles not previously associated with these epitopes, and 8 additional epitopes that have been described previously. In a larger cohort, we demonstrated that 11 (69%) of these 16 newly described immunogens were recognized by individuals of different race or ethnicity. Most HIV-1-specific CD8+ T cell epitopes identified were either novel or restricted by alternative MHC class I alleles. Frequent recognition of several of these CTL epitopes in persons of diverse racial backgrounds bodes well for the development of a broadly reactive HIV-1 vaccine.

Foamy viruses (FVs) are classified in the family Retroviridae, but recent data have shown that they are not conventional retroviruses. Notably, several characteristics of their particle replication strategies are more similar to those of hepatitis B virus (HBV) than those of typical retroviruses. Compared to conventional retroviruses, which require only Gag proteins for budding and release of virus-like particles (VLPs), both FV and HBV require Env proteins. In the case of HBV, Env (S protein) alone is sufficient to form subviral particles (SVPs). Because FVs also depend on Env for budding, we tested whether FV Env alone could produce SVPs. The Env proteins of FV and murine leukemia virus (MuLV) were both released into cell culture supernatants and migrated into isopycnic gradients; however, unlike MuLV Env, FV Env displayed characteristics of SVPs. FV Env particles were of greater density than those of MuLV (1.11 versus 1.07 g/ml, respectively), which strongly suggested that the released proteins of FV Env were particulate. When we examined FV SVPs by immunoelectron microscopy, we found particles that were consistent in morphology, size, and staining with gold beads, similar to FV VLPs and unlike the particle-like structures of MuLV Env, which were more consistent with vesicles produced from nonspecific membrane "blebbing." Taken together, our results demonstrated that FV Env alone is sufficient for particle budding. This finding is unique among retroviruses and further demonstrated the similarities between FV and HBV.

OBJECTIVE:To evaluate the correlation between host genetic profiles and virological and immunological outcomes among HIV-1-seropositive participants from the Reaching for Excellence in Adolescent Care and Health (REACH) cohort. METHODS:HLA class I and chemokine coreceptor (CCR) alleles and haplotypes were resolved in 227 HIV-1-seropositive adolescents (ages 13-18 years; 75% females; 71% African-Americans) and 183 HIV-seronegative individuals, with quarterly follow-up visits between 1996 and 2000. Each HLA and CCR variant with consistent risk and protective effect on HIV-1 pathogenesis was assigned a score of -1 and +1, respectively. All individual markers and genetic scores were analyzed in relation to plasma viral load (VL) and CD4 T lymphocytes during a 6-12-month interval when no antiretroviral therapy was taken. RESULTS:HLA-B*57 alone was a strong predictor of VL (P < 0.0001), but composite genetic profiles found in over 50% of patients consistently outperformed the individual component markers in multivariable analyses with or without adjustment for gender, race, age, and membership of clinical patient groups. Adolescents (n = 37) with a favorable combination of VL (< 1000 copies/ml) and CD4 T cell counts (> 450 x 10(6) cells/l) consistently had more positive (+1 to +2) than negative (-1 to -4) HLA and CCR scores compared with those (n = 56) with an unfavorable combination (VL > 16,000 copies/ml and CD4 cells < 450 x 10(6) cells/l) or the remainder (n = 134) of the cohort (overall P < 0.0001). CONCLUSION/CONCLUSIONS:A generalizable genetic scoring algorithm based on seven HLA class I and CCR markers is highly predictive of viremia and immunodeficiency in HIV-1-infected adolescents.