Serological Cross-reactivity Between Envelope Gene Products of Type I and Type II Human T-cell Leukemia Virus

People exposed to type I human T-cell leukemia virus (HTLV-I) develop antibodies to an antigen at the surface of virus-infected cells, designated human T-cell leukemia virus membrane antigen (HTLV-MA). In an earlier study, we demonstrated that the major component of HTLV-MA is gp61, a glycoprotein encoded by the HTLV env gene. In the current study, we found that human antibodies that react with HTLV-MA on cells infected with HTLV-I react equally well with HTLV-MA on C3-44/MO, a target cell infected with type II HTLV. A glycoprotein with an approximate size of 67 kDa, gp67, was identified in C3-44/MO using immunoprecipitation and NaDodSO4/PAGE analysis. The positions of serine and cysteine residues were determined in the amino terminus of gp67 by radiolabel sequencing analysis. Comparison with the amino acid sequence deduced from the primary nucleotide sequence of HTLV-IIMO virus reveals that gp67 is also encoded, at least in part, by the env gene. The gp67 of HTLV-IIMO, like the env gene product of HTLV-ICR, gp61, is recognized both by antibodies from a HTLV-IIMO-infected patient with a variant form of hairy cell leukemia, and by antibodies from patients with HTLV-I-associated adult T-cell leukemia/lymphoma. These results indicate that, despite the divergence between HTLV-I and HTLV-II, the major env gene products of the two types of HTLV are conserved to the degree that they are serologically cross-reactive.