Polyomavirus persists in CD4/8 double-knockout, but not in CD4 or CD8 single-knockout mice.

The effects of incomplete immunocompetence on possible persistence and reactivation of polyomavirus in adult mice were investigated by a polyomavirus-specific polymerase chain reaction (PCR). The presence of virus DNA was followed between 4 days and 2 months postinfection (p.i.) in polyomavirus-infected normal adult A/Sn mice and CD4-/- and CD8-/- single-knockout, as well as CD4-/-8-/- double-knockout BALB/c or C57BL/6 mice. The same study was performed in A/Sn mice immunosuppressed by thymectomy (THX), cytosine-beta-D-arabinofuranoside (Ara-C) treatment, and total body irradiation (TBI). Primary polyomavirus infection of CD4-/- or CD8-/- single-knockout mice was similar to that obtained in normal adult mice when followed by PCR. Viral DNA was detected in a limited number of organs during 4 weeks p.i., but was no longer observed after 1-2 months. In contrast, the virus could be detected in most organs of CD4-/-8-/- double-negative mice and in THX-, Ara-C-, and TBI-treated adult mice and was still present 1-2 months p.i. In polyomavirus-infected normal adult mice a later immunosuppression did not lead to reactivation of the virus. Furthermore, if a second challenge of polyomavirus was administered 4 weeks after primary infection in both normal or recently immunosuppressed mice no viral DNA could be detected by PCR.