THE ANTIBODY-RESPONSE TO FUNGAL MELANIN IN MICE

Melanins are associated with virulence in several important human path ogens, but little is known about the immune response to this ubiquitou s biologic compound. We hypothesized that melanin produced by the fung us Cryptococcus neoformans was immunogenic. C, neoformans melanin was purified from melanized fungal cells and was used to immunize C57BL/6, BALB/c, and T cell-deficient (nude) BALB/c mice. The Ab response was evaluated by ELISA, immunofluorescence, and agglutination, The results demonstrate that melanin can be immunogenic, and the humoral immune r esponse is T cell independent. Furthermore, the experiments demonstrat e 1) a sensitive ELISA for the measurement of Ab to melanin, 2) that m ice mount an intense Ab response to fungal melanin that includes Abs o f IgM and IgG isotypes, 3) that melanins from different sources have c ross-reactive epitopes, and 4) melanin in the cell wall of melanized y east cells reacts with Abs raised to L-dopa C, neoformans melanin. The biologic significance of Ab to melanin remains to be determined, but the development of Ab suggests that this amorphous insoluble polymer c an stimulate the immune system. The serologic techniques described her e may prove useful for the evaluation of Ab responses to melanin in a variety of diseases.