First generation adenoviral vectors and-recombinant adenovirus-based HIV vaccines which contain HIV-1 gag, HIV-1 pol and/or HIV-1 nef polynucleotide pharmaceutical products, and biologically relevant modifications thereof are described. The adenovirus vaccines, when directly introduced into living vertebrate tissue, express the relevant proteins, inducing a cellular immune response which specifically recognizes HIV-1. The exemplified polynucleotides of the present invention are synthetic DNA molecules encoding HIV-1 Gag, HIV-1 Pol, HIV-1 Nef, and derivatives thereof. The adenoviral vaccines of the present invention, alone or in combination, will offer a prophylactic advantage to previously uninfected individuals and/or provide a therapeutic effect by reducing viral load levels within an infected individual, thus prolonging the asymptomatic phase of HIV-1 infection.