Development of an antigen-specific ELISPOT to detect intestinal antibody responses to the swine whipworm, Trichuris suis

The swine whipworm, Trichuris suis, is a parasite present throughout the United States and is of concern to the swine industry worldwide because it is very pathogenic to growing pigs. The economic threat posed by T. suis and other intestinal parasite infections has created a strong interest in the development of parasite vaccines for the swine industry. Use of a vaccine either alone or with anthelmintics should reduce the economic losses. However, before effective parasite vaccines can be created, the swine gastrointestinal immune response to parasite antigens must be understood. In this study, an enzyme-linked immunospot (ELISPOT) assay was developed to measure total and antigen-specific IgG and IgA antibody secreting cells (ASC) from gut-associated lymphoid tissues (GALT) [mesenteric lymph node explants from jejunal region of small intestine (SI-MLN) and cecum in large intestine (C-MLN); and ileocecal Peyer's patches (IC-PP)] and lamina propria from the proximal colon removed from T. suis infected pigs. Tbe local antibody responses were compared to peripheral antibody responses found in the spleen and submandibular lymph nodes. The hypotheses to be tested was that parasite antigen-specific antibody secreting cells would be greatest in lymphoid tissue draining the site of infection compared to peripheral lymphoid tissues and that 19A ASC would predominate over IgG ASC in the lamina propria of T. suis infected pigs. The total IgG and IgA ASC frequencies for the spleen, SI-MLN, and ICPP did not significantly change (P> 0.05) over time. For C-MLN, there was a significant increase (p< 0.05) of total IgG ASC during a primary infection with T. suis. Antigen-specific IgG ASC were greatest at the GALT site closest to the infection, CMLN, whereas, antigen-specific IgA ASC predominated in the proximal colonic: lamina propria. Host protection to T. suis develops after anthelmintic: treatment of a primary exposure to parasite. The ELISPOT assay provided valuable information on the localization and compartmentalization of the swine gastrointestinal immune response to T. suis which resides in the cecum and proximal colon. In the future, this technique may be useful for monitoring gastrointestinal immune parameters of pigs exposed to a T. sllis vaccine.