The Cellular Responses Induced by the Capsular Polysaccharide of Cryptococcus neoformans Differ Depending on the Presence or Absence of Specific Protective Antibodies

A.      Vecchiarelli

doi:10.2174/1566524054022585

Abstract

The capsule of Cryptococcus neoformans, the principal virulence factor of this fungus, is composed primarily of polysaccharide. The predominant component of the polysaccharide capsule is glucuronoxylomannan (GXM), a compound with potent immunoregulatory properties. GXM is bound and internalized by natural immune cells affecting innate and subsequent adaptive immune response. The cellular pattern recognition receptors involved in GXM binding include toll-like receptor (TLR)4, CD14, TLR2, CD18, Fc gamma receptor II (FcγRII). This multiple cross-linking leads to a suppressive outcome that is arrested and even reversed by protective antibodies to GXM. This review analyzes the immunosuppressive effects induced by capsular material, considering its pattern recognition receptors, and dissects the mechanism of monoclonal antibody shifting to immunoactivation.

Keywords: c. neoformans, antibodies, host response, capsular polysaccharide, immune response, virulence factors, immunosuppression, humoral immunity