A 77-KILODALTON PROTEIN OF CRYPTOCOCCUS-NEOFORMANS, A MEMBER OF THE HEAT-SHOCK-PROTEIN-70 FAMILY, IS A MAJOR ANTIGEN DETECTED IN THE SERA OF MICE WITH PULMONARY CRYPTOCOCCOSIS

Heat shock proteins (HSPs) from several pathogenic microbes have been shown to be target molecules of humoral responses as well as cellular immune responses, However, little is known about target molecules in p ulmonary cryptococcosis, Western blotting analysis revealed that exper imentally induced pulmonary cryptococcosis in (BALB/c x DBA/2)F-1 mice was associated with the appearance of serum antibodies to a 77-kDa pr otein derived from Cryptococcus neoformans as well as to 18-, 22-, 25- , 36-, and 94-kDa proteins. Since the 77-kDa band also reacted with ra bbit polyclonal antibodies against 70-kDa HSP (HSP70) family members, the protein was predicted to be a member of the HSP70 family. We also purified HSP70 directly from a C. neoformans cell extract by Mono Q fa st protein liquid chromatography and ATP-agarose affinity column chrom atography and showed that it was positive in immunoblot analysis using either serum from C. neoformans-infected mice or rabbit anti-HSP70 an tibodies. N-terminal amino acid sequencing of this purified protein co nfirmed that the 77-kDa protein was a member of the HSP70 protein fami ly, A 66-kDa protein, which coincidentally purified with the HSP70 pro tein and was identified as a member of the HSP60 family by N-terminal amino acid sequencing, was not reactive with sera from C. neoformans-i nfected mice, Thus, a protein associated with the HSP70 family and der ived from C. neoformans was a major target molecule of the humoral res ponse in murine pulmonary cryptococcosis.