Western blot analyses and LD50 determinations of Toxoplasma gondii isolates

Western blot analysis of tachyzoite detergent extracts revealed striking similarities and only minor differences in the antigenic profiles of four isolates, including one new isolate of Toxoplasma gondii. At least nine common protein bands with molecular weights ranging from 14,000-108,000 were recognized by all antitoxoplasma antisera. Differences existed primarily between molecular weights 28,000 and 33,000. The LD50 determinations showed that strains of laboratory mice were affected differently by the various Toxoplasma isolates used in this study. Results indicate a need for further investigations into whether there are true strain differences of Toxoplasma gondii or simply different isolates of the same strain of this single species in the genus Toxoplasma.