Barney S. Graham, MD, PhD, and colleagues from the National Institutes of Health IH Vaccine Research Center in Maryland, the Fred Hutchinson Cancer Research Center in Seattle, and GenVec Incorporated tested two possible HIV vaccines with the hope of producing an immune response in healthy, uninfected adults. One was a plasmid DNA-based vaccine expressing genes from three dominant HIV subtypes, and the second used recombinant adenovirus serotype 5 (rAd5) as a vector to deliver similar HIV strains.
"Both approaches operate by gene delivery of customized vaccine antigens that are produced by host cells to initiate an immune response. DNA is simple and does not have the problem of anti-vector immunity. However, DNA may be less potent than vector-based gene delivery strategies. Replication-defective rAd5 has the advantage of targeted, efficient gene delivery and high potency, but may be susceptible to anti-vector immunity," said Graham.
Both vaccines were tested in healthy uninfected adult volunteers. The DNA vaccine was found safe and well-tolerated. By week 12 following immunization, 97.5% of vaccinees experienced positive CD4 T cell responses and 40% experienced positive CD8 T cell responses.
The recombinant vector vaccine was also well-tolerated, but higher doses led to some adverse events such as pain and fever. By week 4 following immunization, 93.3% of vaccinees experienced positive CD4 T cell responses, and 60% experienced positive CD8 T cell responses.
"HIV-specific CD8 cell responses clear virus infected cells, and appear during the declining viremia following acute infection," explained Graham. "HIV-specific CD4 responses also peak early in infection; however
Source:Infectious Diseases Society of America