Antigens of Histoplasma capsulatum. I. Serologic Differences between Histoplasmins Derived from Albino and Brown Filamentous Isolates

Recent studies indicate that Histoplasma capsulatum may be separated culturally into two distinct morphologic types, albino (A) and brown (B), at the time of primary isolation from clinical materials, and that the B variety appears to be the more virulent for the experimental animal. It is probable that the diagnostic antigens presently used may have been derived from the less virulent A filamentous form since A displaces B unless separated at the time of primary isolation. The antigens of histoplasmins prepared from primary isolates of A and B were compared with each other, and with antigens from standard HKC-43 histoplasmin, using DEAE-cellulose, gel-column chromatography and agar-precipitin analysis. Preliminary studies of the chromatography profiles did not reveal distinct qualitative or even quanitative differences between A- and B-derived histoplasmins. However, the gel-precipitin analyses verify the presence of an antigen unique to the B-derived histoplasmin. Since the B antigen appears also to be strain specific, these results suggest the need to develop specific diagnostic antigens derived from the B as well as the A varieties for the serologic study of histoplasmosis.