Antibody responses and lymphocyte proliferation in mice experimentally infected with Gnathostoma spinigerum

Abstract

G. spinigerum is a tissue invasive nematode commonly found in Thailand. The host-parasite relationships of this parasitic infection especially the immune responses are not completely understood. To study the antibody responses and lymphocyte proliferation, the mouse model experimentally infected with this parasite were tested before and after treated with anthelmintic drug (ivermectin) at different time point. The infective stage of advanced third stage larvae (L3s) obtained from natural infected eels was orally given to both groups of mice with 10 and 20 larvae. Ten days after infection, half of each group was treated with single oral dose of 0.4 mg/kg body weight ivermectin. The antibody levels (IgG, IgG1, IgG2a and IgE) from the sera could be detected within Day 10 post infection (PI) by ELISA. These antibodies level gradually increased, reached a plateau during Day 60 and 120 PI and then slightly decreased thereafter. From the overall kinetic responses, IgG1, IgG and IgE antibodies were the three top predominant isotypes. The level of IgG1 in the post drug treated (PRx) mice, infected with 10 larvae was statistic significantly decreased within Day 90 PRx. The IgE-Ab level of the 20 larvae infected mice was significantly lower within Day 90 after drug administration. While the IgG-Ab level still persisted and was not statistic significantly changed after treatment to the end of the experiment (6 month PRx). Poor response of IgG2a was noted in every time points of post infection and post drug treatment. These observations may lead to an application for immunodiagnosis and an evaluation of the effectiveness of chemotherapy. With regard to the lymphocyte proliferation, spleen cells from mice infected with 10 and 20 larvae were tested at Day 10, Day 50 and Day 180 PI. Altered reactivity (slightly depressed) to stimulation by Con A and unresponsiveness to specific stimulation by antigen were observed. The depressed responses were more obvious in animals with high does and chronic infection. This phenomenon was abolished by anthelmintic treatment, suggesting that the altered and depressed responses were reversible and associated with active infection. The results from this study help confirm the role of Th-2 response in regulating antibody production and T cell proliferation response to G.spinigerum. Further studies are required to characterize the specific mechanism that G.spinigerum used to suppress T cell proliferation.