Evaluation of Trichinella spiralis larva group 1 antigens for serodiagnosis of human trichinellosis.

To identify Trichinella antigens suitable for high-specificity and high-sensitivity serodiagnosis of human trichinellosis, we evaluated assays using four antigens: (i) crude first-stage larval extract (CLE), (ii) O-deglycosylated CLE, (iii) tyvelose-bearing antigens (Trichinella spiralis larva group 1 [TSL-1] antigens) purified by US4 affinity chromatography and coupled directly to enzyme-linked immunosorbent assay (ELISA) plates (pTSL-1 antigens), and (iv) TSL-1 antigens immobilized on ELISA plates with the monoclonal antibody (MAb) US4 (cTSL-1 antigens). Assays using these antigens were compared by analysis of sera from healthy individuals (n = 224) (group 1), individuals with noninfectious intestinal pathologies (n = 114) (group 2), individuals with other parasitic infections (n = 107) (group 3), and individuals with confirmed trichinellosis (n = 42) (group 4). Our results indicate that capture ELISA using cTSL-1 antigens is the most effective method for serodiagnosis of human trichinellosis; this was the only method showing 100% specificity and 100% sensitivity at the patent stage of the infection, and it was also the most sensitive for sera obtained prior to patency in indirect immunofluorescence (IIF). Indirect ELISA with pTSL-1 antigens was also 100% specific but was slightly less sensitive, particularly with sera obtained before IIF patency. Inhibition ELISA with MAb US4 indicated (i) that in Trichinella-infected patients the immune response to TSL-1 antigens is directed mostly against tyvelose-containing epitopes (mean of 84.2% of total anti-TSL-1 immunoglobulin G1 [IgG1] antibody response [range, 51.3 to 97.6%]) and (ii) that in most individuals a large proportion of anti-CLE IgG1 antibodies (mean, 49.5%; range, 7.3 to 92.6%) are directed against tyvelose epitopes.