Plasmodium berghei NK65 in the Inbred A/J Mouse: Immunity in the A/J Mouse Naturally Recovered from NK65C and Challenged with NK65E*

SYNOPSIS. Female retired breeder A/J mice were infected with Plasmodium berghei NK65C deme. Those animals which recovered were allowed to recrudesce and were inoculated again with NK65C. Twenty-one weeks after the original challenge, the mice were divided into 2 equal groups. One group was challenged with NK65C and the other with NK65E. Both demes of P. berghei were mosquito derived from NK65. NK65C appeared to give less protection to mice challenged with NK65E deme than to those challenged with the homologous NK65C deme. One mouse which had recovered from infection with NK65C deme died from the NK65E challenge. No definitive conclusions could be drawn regarding antigenic variation and virulence between demes E and C.