Tumor development after polyoma infection in athymic nude mice.

Nude (nu/nu) mice in a CBA/H background show an age-dependent ssuceptibility to tumor development after polyoma virus infection (strain LID-1) when compared with nu/ + or CBA/H mice, which is apparent when 15- or 30-day-old mice are used: tumor incidence was 83 to 90% in nudes and 0 to 10% in controls. Latent perids for tumor development were also shortened in nudes. However, with increasing age nude mice become partially resistant and only 25% develop tumors when infected at 120 days of age. This partial resistance could be transferred with spleen cells to newborn mice. The cells in spleen responsible for this transfer can be eliminated by lysis with anti-Ig and complement or by pre-treatment of the donor with 100 mg/kg of cyclophosphamide and were not affected by treatment in vitro with anti-Thy.1.2 or procedures that remove adherent cells and/or macrophages. When the cells in 15-day-old nu/ + spleen were studied, both anti-Ig or anti-Thy.1.2 treatment eliminated tranfer of resistance to newborn. Virus replication in tissues of nude mice was increased 5 days after infection when compared with nu/ + but became comparable by day 15 after infection. Hemagglutination-inhibition antibodies in serum of nude and nu/ + had comparable titers when measured early after infection but higher titers were observed in nu/ + later after infection.