Immune spleen cell-mediated protection against fatal Hantaan virus infection in infant mice.

To clarify the basis of the age-dependent susceptibility of infant mice to fatal meningoencephalitis caused by Hantaan virus, we investigated the ability of spleen cells from immune and nonimmune weanling BALB/c mice to confer protection to syngeneic infant mice. Intraperitoneal transfer of 10 X 10(7), 5 X 10(7), 2.5 X 10(7), and 1.2 X 10(7) immune spleen cells to infant mice 24 hr after intracerebral challenge with 100 50% lethal doses of Hantaan virus (strain 76-118) resulted in 100%, 70%, 64%, and 30% protection, respectively. Even as late as 48 hr after virus challenge, transfer of 10 X 10(7) immune spleen cells conferred complete protection. In contrast, nonimmune spleen cells offered no protection, even when cells were transferred 48 hr before virus challenge. The protective capacity of immune spleen cells was abolished following treatment with antibody to theta antigen and guinea pig complement, but was preserved after the depletion of B cells, a result suggesting that T cells play a crucial role in the resistance of mice to fatal Hantaan virus infection.