Evaluation of antibody against Aspergillus fumigatus thioredoxin reductase GliT for diagnosis of invasive aspergillosis

Objective To establish an ELISA-based method to detect IgG antibody against Aspergillus fumigatus thioredoxin reductase GliT(TRG) and estimate the diagnostic value of anti-TRG antibody for invasive aspergillosis(IA).Methods In this study 42 non-agranulocytosis patients and 34 agranulocytosis patients were included.The control sera were obtained from healthy individuals(n=200) and non-IA patients with infections of other fungi or bacteria documented by blood culture.An ELISA method for detection of anti-TRG antibody levels in sera was set up using the recombinant TRG as coating antigen.The anti-TRG antibody levels in sera of IA patients were detected by ELISA.The sensitivity and specificity of the assay were compared with GM test.A rabbit IA model was used to estimate the antibody response of TRG.Results The cutoff value of the ELISA was 0.514.In non-agranulocytosis IA patients,the median absorbance value of anti-TRG antibody was 0.827(interquartile range 0.571-1.234),and the sensitivity was 81.0%(34/42).In agranulocytosis IA patients,the median absorbance value of anti-TRG antibody was 0.445(interquartile range 0.250-0.924),and the sensitivity was 41.2%(14/34).The median absorbance value of anti-TRG antibody in IA patients was significantly higher than that of non-IA patients or healthy individuals(P0.01).In non-agranulocytosis IA patients,the sensitivity of the anti-TRG antibody test for diagnosing IA(81.0%) was superior to GM assay(52.3%)(P0.01),while in agranulocytosis IA patients GM assay was superior to anti-TRG antibody test(P0.01).By combining GM assay with anti-TRG ELISA,the diagnostic sensitivity for non-agranulocytosis and agranulocytosis patients increased to 88.1%(37/42) and 91.2%(31/34) respectively.The kinetic analysis for anti-TRG antibody level showed a constant rise in the early stage of IA,and then fell to normal level if the patient responded to anti-fungal therapy.The anti-TRG antibody in the serum of rabbit IA model was detectable on the 7 day after infection with Aspergillus fumigatus and the antibody level increased constantly.Conclusion The anti-TRG antibody should be a potential marker for auxiliary diagnosis of IA in non-agranulocytosis patients.