HIV vaccine breakthrough?
Since the AIDS pandemic began in the early 1980’s, a vaccine and a cure for this disease have remained elusive. Secretary of Health and Human Services Margaret Heckler during the Reagan administration commented that a vaccine was imminent, however vaccine development has been stymied by the ability of the virus to mutate. A previous summary of the problems encountered during HIV vaccine development can be seen here, and a discussion of some of the reasons “why” were presented in the comment thread to this summary. Needless to say, with 34 million people worldwide (roughly 1 in 200 people) with HIV infection, there remains a huge need to develop effective methods of prevention and treatment.
A posting from io9.com details some recent successes in Phase I human clinical trials for testing a new vaccine designed to confer protection to HIV infection. Anytime a pharmaceutical is brought to market, a number of non-human and human trials must be completed to demonstrate the efficacy of the treatment as well as the safety of the treatment. With this vaccine candidate, researchers at the University of Western Ontario in Canada have been examining the effectiveness of a “killed” whole virus at conferring protection. The vaccine SAV001-H was initially genetically engineered to diminish its infectious potential then inactivated by heat, radiation, or chemicals. At this point, if a suitable animal model system is available, candidate vaccines are tested extensively for safety and effectiveness.
As noted in class, HIV does present a problem, as the animal models for infection are not very good. Consequently, vaccine research for HIV is difficult to accomplish. This report summarizes the results of a Phase I clinical trial, which was designed to examine the safety of the vaccine in humans. A cohort of HIV infected volunteers, ages 18 to 50 were enrolled, and injected with the killed vaccine. Signs and symptoms associated with adverse effects were monitored in the subjects, and were found to be minimal to non-existent. This is great news on its own, as the vaccine appears to be completely safe in humans. Additionally, researchers addressed the other aspect of the study, the efficacy of the vaccine by examining levels of anti-HIV antibody that were produced in the subjects. The subjects for the study were already HIV positive, however specific antibody production to vaccine components were detected in some patients. The study was a double-blind study (both the researcher and the subject do not know whether they are in the control or experimental group) and so researchers need to wait until the end of the study to see if these results are consistent with protective antibody production in patients.
The next step is to demonstrate that the vaccine antibody production actually confers protection to infection, and in an upcoming Phase II clinical study a cohort of HIV negative high risk volunteers will be enrolled. A number of vaccine candidates have gone to trial previously, but none have been found to be particularly effective. Previous vaccines have all used single antigens from HIV, DNA-based genetic vaccines, or recombinant carriers expressing HIV antigens. This attempt is the first one to use whole HIV in a vaccine preparation, in a manner that is analogous to the one used for polio. The investigators are hopeful that this alternative vaccine preparation method will yield better outcomes that previous attempts to prevent HIV infection.