A recent paper in Journal of Immunology suggests that a platform for an HIV vaccine developed by Yerkes National Primate Research Center scientists wonâ€™t run into the same problems as another HIV vaccine.Â Postdoc Sunil Kannanganat is the first author of the JI paper, with Emory Vaccine Center researcher Rama Amara as senior author.
Many HIV vaccines have been built by putting genes from HIV into the backbone of another virus. Some have used a modified cold virus (adenovirus 5). The vaccine developed at Yerkes uses modified vaccinia Ankara (MVA), a relative of smallpox and chicken pox.
Harriet Robinson, former head of microbiology and immunology at Yerkes and also an author on the JI paper, worked with colleagues at CDC and NIH to develop the MVA vaccine. Emory licensed the technology to the firm GeoVax, where Robinson is now chief scientific officer.
In September 2007, the STEP trial, which used an adenovirus 5 backbone vaccine, was halted because the vaccine seemed to increase the risk of HIV infection in some patients with preexisting immunity to adenovirus 5. This raised the question that preexisting immunity might hamper effectiveness of an MVA-based vaccine, since many people around the world have been vaccinated against smallpox.Â Later analyses of data from the STEP trial havenâ€™t resolved this question, however.
The Journal of Immunology paper reports on experiments with monkeys that had immunity to vaccinia virus, were later immunized with an MVA-SIV vaccine, and then challenged with SIV. Preexisting vaccinia immunity DID decrease T cell responses but antibody responses and control of viral levels after SIV exposure were preserved.
Of course, the real test for the MVA vaccine is still to come, in the form of clinical trials that measure efficacy. It has already successfully completed phase I trials for safety and capacity to stimulate the immune system.