Decreased Reactivity of SSPE Strains of Measles Virus with Antibody

Abstract

Six strains of measles virus isolated from five patients with subacute sclerosing panencephalitis (SSPE) were found to be less reactive in neutralization tests than classical wild or vaccine strains. This difference in reactivity was observed with sera from patients convalescing from measles, from patients with SSPE, and from rabbits immunized with SSPE, wild, or vaccine strains. Variants, which in neutralization tests reacted like the SSPE strains, were isolated from classical wild and vaccine strains. These findings support the hypothesis that SSPE strains are variants that emerge from classical measles virus under selective pressures in the patients. Although poorly reactive virus that is isolated from a patient with SSPE may simply represent the most persistent genome of measles virus, it is also possible that the viral characteristic that determines decreased reactivity with antibody, or some associated trait, allows this variant to produce SSPE.