Safety of and Immune Response to a DNA HIV Vaccine Followed By Boosting With One of Two Serotypes of Adenoviral Vector HIV Vaccine in Healthy Adults

The worldwide HIV/AIDS epidemic may only be controlled through development and utilization of a safe and effective vaccine that will prevent HIV infection. Vaccines using a DNA plasmid to prime the response to an adenoviral vector boost are currently being developed. Due to high prevalence of pre-existing immunity to adenovirus serotype Ad5 in the developing world, this study will evaluate boosting with a different serotype, Ad35, as compared to boosting with the Ad5 serotype. This study will also test the effect of the order of administration of recombinant adenoviral vector HIV vaccines when administered without the DNA plasmid vaccine. Two arms of this study will evaluate the safety and immunogenicity of the experimental multiclade, multigene HIV DNA vaccine VRC-HIVDNA044-00-VP, followed by a similarly structured adenovirus vector vaccine boost (either VRC-HIVADV027-00-VP or VRC-HIVADV038-00-VP), in HIV uninfected adults. To determine the effect of pre-existing Ad5 or Ad35 immunity, the other two arms will test the safety and immunogenicity of receiving either VRC-HIVADV027-00-VP followed by VRC-HIVADV038-00-VP, or vice versa. Each volunteer will participate in the study for at least 6 months. Participants will be randomly assigned to one of four groups and will receive either an experimental vaccine or placebo at each vaccination visit. Group 1 participants will receive an injection of the adenoviral vector vaccine VRC-HIVADV027-00-VP at study entry and an injection of VRC-HIVADV038-00-VP at Month 3. Group 2 participants will receive an injection of the adenoviral vector vaccine VRC-HIVADV038-00-VP at study entry and an injection of VRC-HIVADV027-00-VP at Month 3. Group 3 participants will receive an injection of the VRC-HIVDNA044-00-VP vaccine at study entry and Months 1 and 2, followed by an injection of VRC-HIVADV027-00-VP at Month 6. Group 4 participants will receive an injection of the DNA HIV vaccine at study entry and Months 1 and 2, followed by an injection of VRC-HIVADV038-00-VP at Month 6. For Groups 1 and 2, there will be 9 study visits. For Groups 3 and 4, there will be 13 study visits. Medication history, assessment of intercurrent illness and adverse effects, and HIV and pregnancy prevention counseling will occur at all visits. A medical history, a physical exam, HIV testing and counseling and blood and urine collection will occur at selected visits. Participants will also be asked to complete social impact and HIV testing and history questionnaires at selected visits. As of 11/19/07 enrollment and vaccinations have been discontinued. Participants who have already been enrolled have been told which vaccinations they received and will be followed for a total of 5 years.