A DNA/rMVA vaccine strategy is structured to bring about both T-cell and antibody responses. The primary vaccination is DNA based and will express only HIV proteins as a way to produce an HIV-focused immune response. An rMVA vaccine strategy expresses both HIV and MVA proteins and may amplify the focused response of a DNA vaccination. Participants in this study will receive either a combined DNA/rMVA vaccine strategy, in which they receive both types of vaccines; an rMVA vaccine strategy, in which they receive only the rMVA vaccine; or a placebo. The DNA and rMVA are physically two different vaccinations given at separate times, but in the DNA/rMVA group, they will be used together to make up one preventive regimen. Both vaccine components express noninfectious virus-like particles.