Detection of group and interspecies reactivities of mammalian C-type virus p30 proteins by an enzyme-linked immunosorbent assay (ELISA): enhancement of interspecies reactivity by denaturation.

The applicability of the enzyme immunoassay technique to the detection of group and interspecies determinants of C-type retroviral proteins was tested. For this purpose four groups of C-type retroviruses (MuLV, FeLV, SiSV/GaLV, and BaEV/RD114) were assayed for group-specific and interspecies reactivities of their p30 proteins by an enzyme-linked immunosorbent assay (ELISA). We found that the ELISA can detect group-specific as well as interspecies determinants with sensitivity and reproducibility in purified p30 proteins, disrupted viruses, and cell extracts if an anti-p30 interspecies antiserum is used. If monospecific antisera against MuLV p30, SiSV p30, or BaEV p30 were used, only group-specific reactivities were detected reproducibly, whereas the detectability of interspecies determinants depended on the antisera used and varied even with the same antisera. In assays in which the reactivity of native and denatured p30 proteins was compared the detectability of sodium dodecyl sulphate-denatured MuLV p30 was better than that of native MuLV p30 suggesting that some of the most broadly cross-reactive sequences are localized inside the protein molecule and are freed by the denaturation process. Antisera raised against native and denatured p30 proteins showed identical spectra of reactivity.