Mice immunized with attenuated strains of P. berghei, derived from a virulent mouse-adapted strain, were resistant to challenge of the parent strain and of newly isolated gametocyte-producing strains. The majority of the mice fully recovered, as shown by absence of relapse after splenectomy and negative subinoculation tests.
In addition, a newly isolated strain was as easily attenuated as the mouse- and rat-adapted strains and protected mice. After challenge, mice frequently had anemia, though parasitemia was usually slight. These results are discussed with reference to hypotheses of antigenic constitution and the production of autoantibodies.
Present address: Department of Parasitology, Hadassah Medical School, The Hebrew University, Jerusalem, Israel.