Cryptococcus neoformans is an encapsulated fungus that causes
meningoencephalitis in 5-10% of patients with
AIDS. While the immune response that controls
infection is predominantly cell-mediated, Ab-mediated immunity is being studied for
therapeutic use. mAbs to
glucuronoxylomannan (GXM), the predominant constituent of the
polysaccharide capsule are protective in a variety of murine
infection models. However, the mechanism of Ab action in this
infection is unknown. We review the literature on the effect of Ab in cryptococcal
infection and potential mechanisms of action. The mechanism is likely multifactorial, involving enhancement at several branches of the immune response, including opsonization, antigen presentation and altered effector cell function. Removal of the toxic and immunosuppressive effects of GXM may be an important component of the mechanism of Ab action. Changes in pathology in response to
monoclonal antibody (mAb) administration suggest that alterations in
cytokine production may mediate mAb effects. In summary, specific Ab can modulate the course of cryptococcal
infection to the benefit or detriment of the host, but significant questions remain concerning the mechanism of action and the relative importance of antibody-mediated immunity in normal and immunocompromised hosts.