Examining the Role of Genetics in Determining the Immune Response to an HIV Vaccine in HIV-Uninfected Adult Twins

Genetics may play a role in the immune response to HIV vaccines. It remains unknown, however, exactly what the genetic influence on the immune response may be. This study will examine how genes affect the strength of an immune response produced by HIV vaccines and how genes influence different immune responses. In this study, participants will receive two HIV vaccines-a DNA HIV vaccine (VRC-HIVDNA016-00-VP) and a recombinant adenoviral serotype 5 (rAd5) vector HIV vaccine (HIVADV014-00-VP). Both of these vaccines are experimental, but have been used in previous clinical trials without any serious side effects. Comparing immunological responses in HIV vaccine trials can be complicated by various genetic and environmental factors. This study will enroll pairs of twins who grew up in common childhood environments. This will provide researchers with participants who have similar backgrounds so that the role of genetics can be examined while controlling for other environmental variables. The purpose of this study is to examine how genes may influence the immune response to a DNA HIV vaccine followed by a rAd5 HIV vaccine. This study will enroll pairs of healthy, HIV-uninfected monozygotic and dizygotic adult twins. Participants will receive the DNA vaccine at baseline and Months 1 and 2, and the rAd5 vaccine at Month 6. Both vaccines will be injected into the upper arm. At all vaccination study visits, participants will undergo a medical history and medication history review, physical exam, and blood collection. Participants will also complete questionnaires and a social impact assessment. They will receive counseling on HIV testing, risk reduction, and pregnancy prevention. After receiving the vaccine, participants will remain in the clinic for at least 30 minutes for observation and monitoring of side effects. For 3 days after each vaccination, participants will record their temperature and side effects in a symptom log. In addition to the vaccine study visits, additional study visits will occur at Weeks 2, 6, and 10; 1, 3, and 7 days after the Month 6 visit; and Months 7, 9, 12, and 18. Various study procedures, including a physical exam, blood collection, and counseling, will be repeated at these visits. At the end of 18 months, participants will be contacted by study researchers once a year for 3 ½ years for follow-up health monitoring.