The Effects of Schistomiasis on the protective potential of Candidate HIV SAAVI DNA-MVA Vaccines in Papio Anubis

Abstract

Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) have no cure and HIV vaccine remains the only remedy. The effect of chronic Schistosomiasis on the efficacy of vaccines currently in clinical use and future HIV vaccines is not known. Several candidate HIV vaccines have been tested or are in ongoing clinical trials, but it is not clear how they might perform in the presence of ongoing helminthic infections. The overall objective of this study was to investigate whether Schistosomiasis compromises the protective potential of candidate HIV vaccines. Four naïve baboons were infected with Schistosoma mansoni cercariae and allowed to develop chronic infections before vaccination with HIV vaccines (SAAVI-DNA and MVA vaccines). A control group of Schistome-free four baboons were vaccinated in a similar manner. The protective potential of the HIV vaccines was assessed by measuring HIV-specific cellular immune responses by IFN-ƴ Elispot assay and ELISA techniques. Immunogenicity data between Schistosome–free/infected vaccinated baboons was compared to show whether Schistosomiasis impacts on the protective potential of HIV vaccination. Graph pad prism software was used for data analysis. Peak HIV responses were elevated in all DNA vaccinated animals one week after boosting with MVA. The mean cumulative HIV responses were higher, though not significant, at P=0.2 in Schistosome-infected baboons (2242±874sfu/106 PBMC) compared to the control group (665±203 sfu/106 PBMC). Responses to individual HIV peptides were present in all animals for Gag whilst only one animal had a response to Tat. The highest magnitude of mean response was directed to Pol in both groups but there was no statistical difference between them. Similarly, there was no statistical difference in the mean responses to any of the other 3 vaccine Immunogens. The antibody response to both Schistosome crude antigens (SEA and SWAP) and HIV Gag peptides was highly elicited in Schistosomiasis. These data suggest that Schistosomiasis positively impacts on the protective potential of HIV vaccination thus elimination of Schistosomiasis is not necessary before administration of the HIV vaccine.