Production of species-specific murine monoclonal antibodies against Cryptococcus neoformans which recognize a noncapsular exoantigen.

Three monoclonal antibodies (MAbs), designated 7C5, 7C9, and 5G8, against a cytoplasmic antigen of Cryptococcus neoformans were produced. MAbs 7C5 and 7C9 recognize culture filtrate antigen (exoantigen) of both encapsulated and nonencapsulated isolates of this pathogen, which suggests that they do not recognize capsular polysaccharide material. This is supported by immunofluorescence data which show reactivity of all 3 MAbs to cytoplasm and cell membranes only. MAb 7C9 also recognized C. neoformans var. gattii antigens but no other fungal pathogens tested in an enzyme-linked immunosorbent assay, while 7C5 and 5G8 recognized antigens of the cross-reactive pathogen Trichosporon beigelii but did not recognize either C. neoformans var. gattii isolates or any other fungal antigens. By Western blot (immunoblot), 7C9 detected antigen at 110 to 120, 65 to 70, 45 to 50, and 36 to 38 kDa; in addition to the latter band, the other two MAbs recognized a band at approximately 30 kDa. All three MAbs were of the immunoglobulin G1 subclass. The two MAbs which are capable of reacting with noncapsular culture supernatant antigen have possible uses in serodiagnosis, particularly in AIDS patients infected with C. neoformans, since in this group the present latex agglutination test has some limitations.