Use of coproantibody measurement to assess the influence of diet on local immune responses of sheep vaccinated against Haemonchus contortus

Systemic responses to challenge infection with Haemonchus contortus in immune Merino sheep

Some systemic responses to single-dose infection with 10,000 Haemonchus contortus infective larvae were examined in sheep already shown to have protective immunity against the parasite. The major haematological finding was a neutrophil leukocytosis that occurred after the infections became patent but not during the pre-patent period. There was no definitive eosinophilia and no discernible change in the erythrocyte parameters. Systemic hyperthermia was not conclusively evident during the pre-patent period. Enzyme-linked-immunosorbent assays (ELISA) were used to measure the secondary anti-helminth antibody response in serum during the pre-patent period when the establishment of patent infection is resisted. These ELISAs employed preparations from adult worms to represent the parasitic stages of the worm, preparations from infective larvae to represent the pre-parasitic stages of the worm, and exsheathing fluid, which is the soluble material obtained when H. contortus larvae undergo ecdysis and transform from the pre-parasitic to the parasitic phase. Antibody responses to the three preparations differed qualitatively, indicating the presence of three different but perhaps overlapping sets of antigens. The three peaks in antibody against exsheathing fluid may reflect the pulses of antigen delivered to sheep as the parasite undergoes its three moults within the host.

Immune responses of sheep to surface antigens of infective larvae of Ostertagia circumcincta

Immune responses to surface antigens of infective larvae of Ostertagia circumcincta were studied in 5-month old Finn-Dorset male lambs. The sheep were vaccinated subcutaneously with 2 doses of 25 micrograms/kg body weight of infective larvae surface or somatic extracts and Freund's or beryllium hydroxide adjuvants. It was found that only in lambs vaccinated with L3 surface extracts and beryllium hydroxide as an adjuvant did worm burdens differ significantly (P less than 0.01) from those of challenge controls (71.7% protection). Sheep vaccinated with the same antigenic preparation but administered with Freund's adjuvant or with beryllium adjuvant and somatic extracts demonstrated rather poor protection (32.4 and 30.5% respectively). All the vaccinated sheep showed a high IgG response to L3 surface antigens while significant levels of serum and bile IgA reacting with the surface extracts were only detected in those lambs vaccinated with L3 surface extracts and beryllium hydroxide. In immunofluorescence tests serum IgA of this group reacted with the whole surface of exsheathed larvae or with the site of opening of excretory pore while IgG antibodies reacted strongly with the anterior and posterior parts of the infective larvae. Both IgA and IgG responses to surface antigens were stage specific.

Interaction of parasitism and nutrition and their effects on production and clinical parameters in goats

Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial design experiment for 5 months to test the main effects and interaction of two levels of nutrition (growth + maintenance, NUT1; twice growth + maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500 and 2000 larvae administered every 2 weeks: W0, W500 W2000, respectively) on weight, feed intake, level of infection and packed cell volume (PCV). The rationale for the experimental design was based on the lack of information concerning the interaction between nutritional status and worm burden. Results indicated significant effects of worm burden levels on PCV, faecal egg contents (eggs per gram of feces (EPG)), actual worm numbers, feed intake and efficiency of feed utilization. Nutrition x worm burden interactions were also significant for PCV and EPG. However, the differences detected for PCV and actual worm numbers did not translate into large or consistent differences in body weight. Goats on NUT2, after an initial period, showed little difference in body weight, irrespective of worm burden. Within the NUT1 level, W0 kids weighed more than W500 or W2000 kids throughout the study. Although not statistically significant, this constitutes a trend towards an interaction between nutrition and worm burden. In both nutrition levels, there were no body weight differences between W500 and W2000 until the last 14 days. Feed intake was depressed in the first 3 months of the experiment for infected animals, but was subsequently followed by a compensatory reaction. Lower establishment rates, based on actual worm counts, were observed for the higher infection level, but in both infection levels establishment rates tended to decrease with time. Nutrition was found to be more important to counteract the consequences of a parasitic infection than to counteract the establishment of that same infection.

Surface antigens of Obeliscoides cuniculi inducing local and systemic humoral responses in infected rabbits

125I-radiolabelled surface proteins of various developmental stages of Obeliscoides cuniculi were used to analyze serum and gastrointestinal immunoglobulin responses of the host to primary infection with 10,000 larvae of the nematode, using a radioimmunoprecipitation method. Serum IgM, IgA, and IgG antibodies reacted mostly with infective larval and adult nematodal surface proteins. The highest binding activity was shown by IgG against the surface of infective larvae on days 56 and 86 after infection. Local (gastric mucosal) antibodies were also predominantly directed against surface antigens of infective larvae and adults, although considerable binding of the fourth-stage larval surface proteins by gastric mucosal IgG occurred 35 days after infection. Physicochemical analysis of the radiolabelled surface antigens revealed that the strongest antigenicity was found in proteins with molecular weights of 40,000 and 145,000. Nonspecific binding demonstrated in our tests by infective larval surface proteins was associated with particles with a molecular weight of 550,000.

Inhibition phenomena mechanisms in experimental obeliscoidosis in rabbits. II. Local and systemic antibody responses

A series of experiments was carried out using adult outbred Polish race rabbits of both sexes infected, during spring or autumn, with 10,000 larvae of Obeliscoides cuniculi, either fresh or stored at 4 degrees C. Extracts of mucosal proteins and bile were collected at postmortem 6 or 12 weeks after infection. Antibody levels were determined in antisera, bile and stomach mucosa by haemagglutination and precipitation tests. Local antibody responses were demonstrated in the stomach and bile, and reactions were obtained with the tissue fluids by haemagglutination and precipitation tests with worm antigens and ES products. Additionally, some specific immunological response was observed in the circulation during the primary infection. These results suggest a clear-cut relationship between increased levels of these antibodies and either larval inhibition or worm expulsion during O. cuniculi infections.