A peptidorhamnomannan from the mycelium of Pseudallescheria boydii is a potential diagnostic antigen of this emerging human pathogen

The ascomycete Pseudallescheria boydii is an emerging human pathogen freque ntly found in soil and polluted water. A peptidopolysaccharide antigen has been isolated from mycelial forms of P, boydii. and characterized using che mical and immunological methods. Monosaccharide composition, methylation an alysis, and H-1- and C-13-NMR spectra indicated the presence of a rhamnoman nan with a structure distinct from those of similar components isolated fro m other fungi, containing Rhap(1 --> 3)Rhap epitopes on side chains which m ay be linked (1 --> 3) to (1 --> 6)-linked mannose, The peptido-rhamnomanna n from P. boydii reacted poorly with an antiserum raised against whole cell s of Sporothrix schenckii and strongly with one against P. boydii hyphae, T hese characteristics and immunological differences suggest that this major rhamnose-containing antigen of P, boydii may be useful for the specific dia gnosis of infections attributable to this fungus.