Investigations on protective abilities of Trichostrongylus colubriformis antigens precipitated by antibodies from rabbits vaccinated with infective larvae somatic extracts

Adult New-Zealand rabbits were vaccinated subcutaneously with three doses of 100 µg of immunocomplexes formed by serum immunoglobulins of rabbits vaccinated with infective larvae somatic extracts (L3SE) and adult nematode phosphate buffered saline- soluble proteins (ASE, group II) or L3SE (group I). Injections of the immunogens were accompanied with beryllium hydroxide, Be(OH)₂ as an adjuvant. Vaccinated rabbits and also those of group III were infected orally with 10,000 infective larvae of T. colubriformis 14 days after antigen injection and necropsied in groups of four on day 4, 8 and 21 after challenge (DACh). Worm burdens found in vaccinated rabbits were significantly lower than in group III only on day 4 (groups I and II) and 8 (group II) after challenge. The degree of protection oscillated at that time between 47-59%. Mesenteric lymph node leukocyte responses were measured using a leukocyte migration inhibition assay. The most significant MLN leukocyte response occurred in all groups on 21 DACh. However, in group II a marked leukocyte reaction started already on 4 DACh. In ELISA tests IgA antibodies specific to ASE reached the highest level in the bile and serum of group II. The mucosal IgG response was the highest in group I until 8 DACh but in group II and III on 21 DACh.