Abstract:

Objective  To evaluate the reactivity of adult hookworm antigens to serum from patients with hookworm disease, and analyze in the serum class- or subclass-specific antibodies that show superior antigen recognition. Methods Sera from healthy participants, patients infected by Necator americanus and those with other parasitic infections were processed for ELISA, which used raw antigens extracted from adult worms of Necator americanus as the coating antigen, and different classes or subclasses of anti-human antibody labeled with HRP as the secondary antibody. The sensitivity and specificity of the assay with various secondary antibodies were compared. Results The ELISA using IgM, IgD，IgE, IgG, IgG1, IgG2, IgG3, or IgG4 as the secondary antibody showed a sensitivity of 41.84%, 2.04%, 1.02%, 92.93%, 19.39%, 25.51%, 17.35%, and 88.78%, respectively; specificity of 77.61% 97.01%, 92.54%, 79.10%, 95.52%, 92.53%, 92.53%, and 92.53%, respectively; and diagnostic efficiency of 56.36%, 40.61%, 38.18%, 87.88%, 50.30%, 52.7%, 47.88%, and 90.30%, respectively. The sensitivity when using IgG4 and IgG as the secondary antibody had far exceeded that when using IgM, IgD, IgE, and other three subclasses of IgG （P<0.05）. There was no difference in sensitivity between tests using IgG4 and IgG（χ2=1.61, P＞0.05）. However, the test using IgG4 revealed significantly higher specificity than that using IgG（χ2=4.97, P＜0.05）. Conclusion  Use of IgG4 as the enzyme-linked secondary antibody shows advantages in overall diagnostic efficiency over other classes/subclasses in ELISA.

Key words: Necator americanus, Adult worm antigen, Antibody, ELISA, IgG4