IMMUNIZATION WITH A MOUSE MAMMARY-TUMOR VIRUS ENVELOPE PROTEIN EPITOPE PROTECTS AGAINST TUMOR-FORMATION WITHOUT INHIBITION OF THE VIRUS-INFECTION

BALB/c mice were immunized with the EP3 surface epitope of the mouse m ammary tumour virus (MMTV) gp52 envelope protein before systemic infec tion with MMTV(C3H) or MMTV(SW). Analysis of the successive stages of the virus infection showed that although these mice were protected aga inst mammary tumour formation, earlier stages of the infection were no t inhibited, as reflected by the persisting superantigen-induced activ ation and deletion of V beta-specific T cells. Transplacental transfer of maternal anti-EP3 immunoglobulins to newborns did not protect them from infection through the Peyer's patches. Preincubation of the MMTV s with an anti-EP3 serum before injection, however, successfully inhib ited the early stages of the infection. Results from this study show t hat to inhibit infection by MMTV efficiently, the virus must be neutra lized before its interaction with the cell membrane, and that the affi nity of the virus-membrane interaction is higher than that of the viru s-antibody interaction.