An improved method for determining neutralizing antibody against lymphocytic choriomeningitis virus in human sera

Human antibody neutralizing lymphocytic choriomeningitis virus is most reliably determined in mice as assay hosts. Whereas the previously recommended procedure yielding a neutralization index requires much serum, the method described here uses only 0.1 ml. An equal mixture of virus and serum is incubated and residual infectivity is titrated intracerebrally in mice. The neutralizing activity is given by the ratio of virus surviving after incubation with control serum and with the test serum respectively. This ratio is called the neutralization factor.