gag 126 gag 107 and gag 141 were expressed in e coli separately clone 29 was used as a template and oligonucleotides corresponding to the 5 39 and 3 39 ends of the published sequence were used in a polymerase chain reaction to generate a complete sequence of the gag protein p24 the 5 39 end contained an ecori site and the 3 39 end contained a bamhi site the reaction product was digested with ecori and bamhi and then ligated into pmlb1113 a recombinant p24 protein gag 24 5 was expressed in e coli the characterization of the recombinant p24 peptides is presented in fig4 the various recombinant p24 peptides were used as antigen in elisa 39 s and in western blots to determine whether or not a given monoclonal antibody bound a given peptide the reactivity pattern of any one monoclonal antibody with the panel of p24 peptides allowed a localization of the recognized epitope to one of four regions as shown in table 4 and fig5 and 6 table 4______________________________________immunochemical analysis of anti 24 mabsusing recombinant peptides gag gag gag gag gag mabmab 24 5 8 126 107 141 group______________________________________5 b4 b5 d9 c5 e2 d5 f12 b6 c10 c6 e11 a6 f6 a7 d4 b7 e1 b7 e10 d7 f3 b8 e7 a9 b7 d9 d5 a10 b2 b10.