Temporal development of cross-neutralization between HTLV-III B and HTLV-III RF in experimentally infected chimpanzees.

Sera from chimpanzees inoculated respectively with HTLV-III B, LAV, HTLV-III RF and brain tissue from an AIDS patient were analysed for neutralizing activity by two methods: a cell fusion inhibition test (CFI) using HTLV-III B infected cells as inoculum and CD4+ cells as target and a replication inhibition test (RIT) using cell-free HTLV-III B as well as HTLV-III RF as inoculum and also CD4+ cells as target. All chimpanzees seroconverted for HTLV-III B antibodies within 2 months after inoculation and the ten sera included in the study recognized the HTLV-III B core proteins p17 and p24 and the transmembrane protein gp41 by immunoblotting. The HTLV-III B external envelope gp120 was recognized by eight sera with antibodies active in the CFI (CFI-Ab) or in the RIT (VN-Ab) using HTLV-III B as inoculum, while neither of two sera without such reactivity did. HTLV-III B CFI-Ab and HTLV-III B VN-Ab concurred in nine of ten serum samples. LAV and HTLV-III B infection induced HTLV-III B CFI-Ab and HTLV-III B VN-Ab within 9 months after inoculation in all four chimpanzees tested. However, only the serum of one of the four animals also neutralized HTLV-III RF. HTLV-III RF inoculation evoked only HTLV-III RF VN-Ab within nine months. Between 11 and 18 months neutralizing activity to both HTLV-III B and HTLV-III RF was found in all four sera of chimpanzees inoculated with HTLV-III B, LAV or HTLV-III RF.(ABSTRACT TRUNCATED AT 250 WORDS)