AEGiS-14IAC: Vaccinia virus stimulated ELISPOT assays in HIV-1 exposed infants.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Vaccinia virus stimulated ELISPOT assays in HIV-1 exposed infants.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. A10084)

Slyker JA, Lohman BL, Rowland-Jones S, Richardson B, Mbori-Ngacha D, Obimbo E, Bwayo JJ, John-Stewart G
University of Washington, Seattle, United States

BACKGROUND: Vaccinia virus stimulated enzyme-linked immunospot (ELISPOT) assays are an attractive alternative to HLA-matched peptide assays because neither HLA type nor viral epitopes need to be identified. Vaccinia ELISPOT may be a useful tool for examining HIV specific cytotoxic T lymphocyte (CTL) responses of HIV-1 infected or exposed infants.

METHODS: Blood was obtained from a cohort of HIV-1 infected and exposed uninfected infants in Kenya. Peripheral blood mononuclear cells (PBMC) were isolated at serial time points, stimulated with vaccinia expressing HIV-1 A clade env (vvenv) or gag (vvgag), or HLA-matched HIV-1 env and gag peptides, and used in ELISPOT assays. Responses to peptides and vaccinia were compared using Chi-square, McNemar's, and t-tests.

RESULTS: 404 ELISPOT assays were performed using both vaccinia constructs and peptides, 54 in HIV-1 positive infants and 350 in HIV-1 exposed uninfected infants. Positive responses to vvgag and vvenv were detected more frequently in HIV-1 infected than in uninfected infants at all time points (eg. month 1, 42.9% vs 4.6%, p = 0.01). In infected infants at 1 month, 67% of the vvgag assays had concordant results with gag peptides, and similar trends were observed at all time points for vvenv and vvgag. In HIV-1 uninfected infants, vvenv results were concordant with env peptide results at all time points, but results from vvgag were discordant with gag peptides at months 3, 9, and 12. Env peptide and vvenv assays detected similar HIV-specific CTL frequencies, but gag peptide assays detected higher frequencies than vvgag (437 vs 88 HIV-1 specific SFU/million PBMC, p < 0.001). The vvenv construct yielded results and frequencies similar to env peptide assays. The vvgag construct appears to be less sensitive in distinguishing positive results and in quantifying HIV specific CTL than gag peptides.

CONCLUSION: The vvenv construct is a useful tool for examining CTL responses in large population-based studies.

Keywords: AEGIS, HIV-1, Vaccinia virus, HIV Infections, T-Lymphocytes, Cytotoxic, Vaccinia, HIV Seropositivity, Enzyme-Linked Immunosorbent Assay, HLA Antigens, Case-Control Studies, Kenya, Infant, Human, immunology

020707
A10084