AEGiS-11IAC: Efficacy evaluation of conventional dual-subtype HIV vaccine.

11th International AIDS Conference

Vancouver, British Columbia — July 7-12, 1996

Efficacy evaluation of conventional dual-subtype HIV vaccine.

Int Conf AIDS 1996 Jul 7-12; 11:4 (abstract no. Mo.A.101)
Yamamoto JK, Mison M, Elyar J, Tellier MC, Pu R; Univ. of Florida, Dept. of Pathobiology, College of Vet. Med., Gainesville, FL. Fax: 904-392-7128.

OBJECTIVE: To evaluate the immunogenicity and prophylactic efficacy of dual-subtype infected cell vaccine against homologous and heterologous FIV subtype challenges in domestic cats.

METHODS: Dual-subtype FIV vaccine was developed from two singly-infected (subtype A or D) cell lines that were inactivated and mixed with threonyl-MDP adjuvant. Specific pathogen free (SPF) cats were immunized SC with either dual-subtype or single-subtype vaccines at a monthly interval (4X). All cats were challenged IP 4 wks after the final immunization with either 500 ID50 of heterologous subtype B strain or 50 ID50 of homologous subtype A or D strains. All cats were monitored for antiviral immunity and virus infection. Virus infection was determined by virus isolation, proviral PCR, and by monitoring changes in FIV-specific antibody profile.

RESULTS: Significant levels of antiviral antibodies (including virus neutralizing antibodies) and FIV-specific cytotoxic T lymphocyte (CTL) activity were detected after immunization with conventional vaccines. Cross-subtype CTL activities were detected in a number of these cats. As of 24 wks post-challenge (pc), 3 of 5 (60%) cats receiving dual-subtype vaccine were protected from high-dose challenge with heterologous subtype B. All cats (n=6) vaccinated with either single-subtype A or D vaccines were not protected from similar subtype B challenge. Further, all cats immunized with single-subtype A vaccine (n=2) were protected against homologous FIV strain, but those immunized with single-subtype D vaccine (n=2) were not protected against homologous FIV strain. Results from the immunogenicity study indicate that the level of Subtype D virus antigens in the single- and dual-subtype vaccines was at least 6-fold lower than the level of Subtype A virus antigens. Thus, vaccine efficacy can be broadened by adding low doses of other FIV subtype antigens to the prototype subtype A vaccine.

CONCLUSIONS: The single-subtype vaccines do not protect cats against heterologous subtype challenges. More importantly, dual-subtype FIV vaccine provided broad-spectrum protection against a heterologous subtype.

Keywords: AEGIS, Immunodeficiency Virus, Feline, AIDS Vaccines, Viral Vaccines, Vaccines, Inactivated, Antibodies, Viral, Evaluation Studies, Vaccines, Synthetic, T-Lymphocytes, Cytotoxic, Vaccines, Vaccines, DNA, DNA Primers, Polymerase Chain Reaction, Specific Pathogen-Free Organisms, Cats, Animal, ICA11

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