Protection from spontaneous lymphoma development in SJL/J(v+) mice neonatally injected with dualtropic SJL-151 virus.

In previous studies dualtropic type C retroviruses were isolated from spontaneous B-cell lymphomas that appear with a high incidence in SJL/J(v+) mice. In this report the possible in vivo pathogenic effect of one cloned dualtropic isolate, designated SJL-151, was investigated. SJL/J(v+) and CBA/J mice, neonatally injected with SJL-151 alone or in combination with SJL-ecotropic virus, were initially studied for virus recovery 4-8 weeks after infection by spleen cell cocultivation with mouse SC-1 and mink ML indicator cells. Whereas ecotropic virus was easily detected in treated mice, dualtropic virus was recovered only from the spleen cells of animals coinfected with SJL-ecotropic and SJL-151 viruses. With a panel of monoclonal antibodies the recovered dualtropic viruses showed an antigenic profile similar to that of the originally injected SJL-151 virus. Whereas virus-injected mice did not show lymphoma induction or acceleration, a remarkable decrease in spontaneous lymphoma incidence was observed in the SJL/J(v+) mice receiving SJL-151 virus alone. A virus-specific antibody response was detectable in these mice, but a similar serum reactivity was also demonstrated in SJL/J(v+) mice coinfected with SJL-ecotropic virus and SJL-151 virus, which subsequently developed lymphomas with the usual high incidence, thus rendering an antibody-mediated protective mechanism untenable. The possibility of viral interference, as an alternative mechanism for lymphoma prevention, is discussed in view of the findings that persistence of SJL-151 virus or de novo generation of dualtropic virus did not occur in aged SJL/J(v+) mice injected neonatally with SJL-151 virus alone.