Melanization of Cryptococcus neoformans in murine infection

Cryptococcus neoformans is a fungus that is pathogenic in humans and that c an produce melanin in vitro. Melanization is associated with virulence, but there is no evidence that melanin is made during infection. Melanins are d ifficult to study because they are amorphous and insoluble. Melanin-binding peptides from a phage display library were used to demonstrate that C. neo formans makes melanin-like compounds in tissue. Melanin-binding peptides we re characterized by a high proportion of positively charged and aromatic re sidues. Two other methods, demonstration of an antibody response to melanin in mice infected with C. neoformans and analysis of yeast cell walls in in fected tissue by light microscopy, were used to support these findings. The demonstration that C. neoformans melanizes in tissue has important implica tions for pathogenesis and drug discovery.