Antigens present in the serum during the periods of acute parasitemia of Plasmodium lophurae of ducks, Plasmodium berghei of rats, and Babesia rodhaini of rats were detected by means of gelprecipitation tests and a tube bentonite flocculation (TBF) test, with globulins from sera of animals that had recovered from each of these infections.
These antigens, which are associated with globulins, were concentrated by salting with (NH4)2SO4 and ultracentrifugation. Antigens adsorbed to bentonite particles were used in the TBF test to detect and titrate antibody in the sera of animals that had recovered from the respective malarias or babesiosis. In addition to the homologous antigen-antibody reactions it was found that each of the antigens reacted, both in gel-precipitation and in TBF tests, with sera of animals that had recovered from each of the other infections. Sera from normal ducks or rats with a few exceptions did not react with the antigen-bentonite preparations.
With bentonite sensitized with globulin from rats recovered from P. berghei and from rats recovered from B. rodhaini, antigens were detected with both materials in the sera of rats with acute P. berghei and rats with acute B. rodhaini infections. Sera from normal rats did not react.
On the basis of these observations cross-reacting serum antigens and antibodies are being sought in other erythrocytic infections such as those with Eperythrozoon, Haemobartonella, Anaplasma, and in the sera of human volunteers infected with Plasmodium jalciparum. The TBF test is also being evaluated as a possible serodiagnostic test for latent malaria.