Human T-cell lymphotropic virus type III (HTLV-III) core antigens: synthesis in Escherichia coli and immunoreactivity with human sera.

Fragments of human T-cell lymphotropic virus type III (HTLV-III) proviral DNA carrying the gene for the core antigen (gag) was cloned in the plasmid REV. Several of the recombinants direct high levels of synthesis of the antigens. One clone, pG1, produced a hybrid protein containing 13 amino acid residues of the carboxyl terminus of the 17 kD virion protein, the entire p24, the major core protein of HTLV-III, and 74 amino acid residues of the amino terminal of the 15 kD core ribonucleoprotein. A second clone, pG2, was similar to pG1 except that it contained no p17 sequences and was missing the amino-terminal 77 amino acid residues of the p24. A third clone, pG3, was similar to pG2, except that all but 56 amino acids of the carboxyl terminus of p24 were removed. All three proteins were found to be strongly immunoreactive with anti-HTLV-III antibodies present in sera from patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC). In addition, pG1 and pG2, but not pG3, reacted with a monoclonal antibody (M26) specific for the p24 virion core protein. Whereas all three reacted with an anti-p15 monoclonal antibody, none of the clones reacted with an anti-p17 monoclonal antibody. These results provide direct evidence to support the predicted assignment of the coding region of the gag gene of HTLV-III. The product from pG2 was purified and was found to be potentially useful for the detection of anti-p24 antibodies in sera from patients with AIDS or ARC and from individuals at risk from AIDS.