Bla g 3: a novel allergen of German cockroach identified using cockroach-specific avian single-chain variable fragment antibody.
BACKGROUND
The IgE response to cockroach allergens is thought to be associated with asthma. German cockroach (GCr) allergen extract is a complex mixture of allergens, and the identification and characterization of immunodominant allergens is important for the effective diagnosis and treatment of GCr-induced asthma.


OBJECTIVE
To characterize a novel GCr allergen homologous to the American cockroach allergen Per a 3.


METHODS
GCr-specific avian monoclonal antibodies were used for direct immunoprecipitation of specific targets from whole-body GCr extract. Precipitated protein was identified by mass spectrometry and sequence analysis. Putative recombinant protein also was expressed, purified, and used for determination of allergenicity, determined by IgE enzyme-linked immunosorbent assay with serum from 61 GCr-allergic patients. The identified target also was analyzed for heat stability using a bead-based assay.


RESULTS
The immunoprecipitated target of monoclonal antibody 2A1 was identified as a novel allergen of GCr homologous to American cockroach allergen Per a 3. This homolog, designated Bla g 3, has an apparent mass of 78 kDa, can be measured in GCr extract using antibody 2A1, and is a heat-stable protein. Screening of 61 serum samples from GCr-allergic patients showed a 22% prevalence of Bla g 3-specific IgE.


CONCLUSIONS
Bla g 3 is a GCr allergen with structural homology to American cockroach allergen Per a 3.
Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic, and Allergenic Products, US Food and Drug Administration, Bethesda, Maryland.
Taruna
T
Khurana
Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic, and Allergenic Products, US Food and Drug Administration, Bethesda, Maryland.
Maggie
M
Collison
Allergy and Molecular Immunology Laboratory, Department of Biological Sciences, National University of Singapore, Singapore.
Fook Tim
FT
Chew
Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic, and Allergenic Products, US Food and Drug Administration, Bethesda, Maryland. Electronic address: jay.slater@fda.hhs.gov.
Jay E
JE
Slater
D000328:Adult; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001249:Asthma / Q000276:immunology*; D020048:Blattellidae / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006433:Hemocyanins / Q000276:immunology; D006801:Humans; D008969:Molecular Sequence Data; D010526:Periplaneta / Q000276:immunology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D057127:Single-Chain Antibodies / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics
D000485:Allergens; C587294:Bla g 3 allergen; Periplaneta americana; D011994:Recombinant Proteins; D057127:Single-Chain Antibodies; D006433:Hemocyanins