Effect of cyclophosphamide on the infection of mice with Tahyna virus

Juvenile SPF randombred ICR mice were given intraperitoneally (i.p.) a single dose of cyclophosphamide (CPA - 80 mg/kg), and 10(3.7) SMicLD 50 of Tahyna virus (California group, Bunyaviridae) one day later. The mice survived, but low concentrations of the virus were recovered from their brains 21 days after infection. No virus was detected in the brains of the animals infected but CPA-untreated. A lower body weight gain and a twofold decrease of virus neutralizing (VN) antibody titre were also observed in the CPA-treated mice. When mice were infected i.p. with 10(4.5) SMicLD50 of the virus, and CPA given 2 days (130 mg/kg) and 5 days (160 mg/Kg) later, the animals died of an acute encephalitis (with a mean virus titre at death of 10(7.3) SMicLD50/g brain), while all the infected but saline-treated animals survived, with no virus recovered from their brains. VN antibody was absent in the CPA-treated infected mice compared to high titres of antibodies detected in the CPA-untreated, infected animals.