Production and characterization of monoclonal antibodies reactive with themycelial and yeast phases of Penicillium marneffei

A definitive tissue diagnosis of Penicillium marneffei is hampered by a mic roscopic similarity to the yeast form of Histoplasma capsulatum and Cryptoc occus neoformans. In order to obtain a better discrimination for accurate d iagnosis, monoclonal antibodies (MAbs) were produced from hybridomas raised from Balb/c mice immunized with mycelial culture filtrate, By indirect imm unofluorescent or immunoblot analyses, one immunoglobulin (Ig) G(1) (3C2) M Ab and three IgM (8B11, 3B9 and 8C3) MAbs were found to react strongly with P. marneffei antigens. In the immunoblots, the MAbs 8B11 and 3B9 reacted m ost strongly with a high molecular weight component (> 200 kDa) produced du ring either the mycelial or yeast phase of fungal growth. The immunoreactiv e epitopes for these two IgM MAbs were most likely associated with carbohyd rate moieties, judging from their susceptibility to periodate oxidation and concanavalin A binding. This is in contrast to the immunoreactive epitopes for the MAbs 8C3 and 3C2, which were resistant to destruction by periodate treatment and did not bind to the lectin. Judging from immunofluorescent i ntensity, the three IgM MAbs could react strongly with the yeast cells pres ent in the tissue biopsies of patients with P. marneffei infection.