The research outlined in this thesis is mainly designed to develop a technology of producing a DNA prime-protein boost vaccine against HIV-1 infection. To reach this aim 1.7kb fragments encoding gp120 antigens deriving from two groups of British HIV-1 infected persons (one consisting of homosexual individuals from Edinburgh, Newcastle and Belfast and the other consisting of haemophiliac patients from Edinburgh who became infected from a common batch of Factor VIII) were PCR amplified and subsequently subcloned into a cloning vector (pGEM T). A mammalian expression vector (pSRHS) was modified in order to include a polylinker to allow the transfer of the 1.7-kb fragments from pGEM T to pSRHS. The recombinant clones were identified and the gp120 genes were expressed in mammalian cells (COS cells) by lipofectin protocol. The functional clones (i.e. those that contained intact open reading frames), were selected and their associated gp120 antigens were quantified by an 'in house' ELISA method. Equivalent amounts of the gp120 antigens were used in an anti-gp120 ELISA to estimate the extent of recognition by the IgG antibodies from autologous and heterologous sera. The nucleic sequences of the functional clones were obtained and some properties such as their predicted NSI/SI phenotype, co-receptor usage and glycosylation sites were analysed. The phylogenetic relationship between the sequences derived from both cohorts was computed and the extent of gp120 antigen recognition by the IgG antibodies from the autologous and heterologous sera was analysed in conjunction with their degree of relatedness. As a conclusion of this study, a high degree of cross-reactivity was noted between antigens and sera, the extent of the recognition of the antigens by the sera was given by the patients' immune status. No significant difference in recognition of the gp120 antigens by sera was observed. This result points towards the potential usage of a cocktail of such DNAs and their corresponding gp120 antigens as a DNA prime-protein boost vaccine.