Human serum IgE reacts with a Metarhizium anisopliae fungal catalase.
BACKGROUND
Previous studies have demonstrated that Metarhizium anisopliae extract can induce responses characteristic of human allergic asthma in a mouse model. The study objectives were (1) to identify and characterize the M. anisopliae mycelia extract (MYC) proteins that are recognized by mouse serum IgE, (2) to determine if human serum IgE reacts with these proteins, and (3) to determine if these IgE-reactive proteins are found in other fungi.


METHODS
Asthmatic human serum IgE, M. anisopliae crude antigen (MACA) immunized mouse serum IgE, and anti-catalase antibodies were used to probe one- and two-dimensional gel electrophoresis blots of MYC.


RESULTS
Mass spectrometry analysis identified catalase as a mouse IgE-reactive protein. This identification was confirmed by assaying catalase activity in the extract and extract immunoblots probed with anti-catalase antibody. Six adult asthmatic sera contained IgE, but not IgG, that was reactive with mycelia extract proteins. A similar protein profile was seen when blots were probed with either mouse anti-MACA IgE or anti-bovine liver catalase antibodies. Furthermore, these mouse anti-MACA and anti-catalase antibodies were cross-reactive with other mold extracts (skin prick testing mix) and Aspergillus niger catalase.


CONCLUSIONS
Some human asthmatics have developed IgE that reacts with an M. anisopliae catalase, most likely due to cross-reactivity (minimal IgG development). The cross-reactivity among fungal catalases suggests that IgE-reactive catalase might be useful for exposure assessment. Additionally, the similarity of protein profiles visualized with both human and mouse serum IgE suggests that allergy hazard identification can be facilitated using a mouse model.
Ward
Marsha D W
MD
United States Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711, USA. ward.marsha@epa.gov
Donohue
Maura J
MJ
Chung
Yong Joo
YJ
Copeland
Lisa B
LB
Shoemaker
Jody A
JA
Vesper
Stephen J
SJ
Selgrade
MaryJane K
MK
D000328:Adult; D000818:Animals; D000946:Antigens, Fungal / Q000276:immunology / Q000378:metabolism*; D001249:Asthma / Q000097:blood / Q000276:immunology* / Q000382:microbiology; D002374:Catalase / Q000276:immunology / Q000378:metabolism*; D002417:Cattle; D005260:Female; D006801:Humans; D007117:Immunization, Secondary; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D052981:Metarhizium / Q000201:enzymology / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D025282:Mycelium / Q000378:metabolism; D011485:Protein Binding
D000946:Antigens, Fungal; D007073:Immunoglobulin E; D002374:Catalase