Well-Characterized Monoclonal Antibodies Against Cell Wall Antigen of Aspergillus Species Improve Immunoassay Specificity and Sensitivity

Center of Laboratory, Zhujiang Hospital, Southern Medical University, Guangzhou, China; Department of Pathology, School of Basic Medical Science, Southern Medical University Guangzhou, China; Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China; Department of Microbiology, The University of Hong Kong, Hong Kong Special Administrative Region, China

^* To whom correspondence should be addressed. Email: linche{at}pub.guangzhou.gd.cn.

	Abstract

The diagnosis of invasive aspergillosis (IA) based on the detection of Aspergillus galactomannan (GM) is complicated by the presence of cross-reactive GM epitopes in patient specimens. Presently, we have developed a novel and specific Aspergillus antigen capture enzyme-linked immunosorbent assay (ELISA) by selection of two well-characterized monoclonal antibodies from 17 candidate antibodies. The epitopes recognized by the monoclonal antibodies were present on the cell wall of hyphae and conidia of Aspergillus species, which were circulating or excreted as immunodominant antigens during the acute phase of IA established in the animal models. Detection of experimental Aspergillus-mediated antigenemia was suitably sensitive and was comparable to a commercial GM detection ELISA kit (Platelia Aspergillus). Moreover, the specificity of this assay was 100% when tested against 382 normal serum and 120 normal urine specimens. Cross-reactivity with other common opportunistic fungi such as Penicillium and Candida species, and with purified GM protein derived from Aspergillus, was not evident. Therefore, this chemical nature of epitopes captured in this assay is most likely not associated with the GM structure, implicating this newly developed Aspergillus antigen capture ELISA assay as a promising tool for the diagnosis of IA without the risk of false-positive results that are problematic in current GM antigen assays.