Vaccination against ETEC in pigs

Enterotoxigenic Escherichia coli (ETEC) that bear F4 fimbriae on their surface (F4+ ETEC) are a major cause of postweaning diarrhoea (PWD) in pigs. The F4 fimbriae enable the bacteria to colonize the small intestine and subsequently, to produce enterotoxins causing diarrhoea. Consequently, an F4-specific secretory IgA response at the intestinal mucosa that neutralizes the fimbriae is desired for protection against postweaning diarrhoea

Oral β-glucans modulate systemic antigen responses in dogs and pigs

The cell wall glucans of yeasts and fungi consist of a linear backbone of -1,3-linked glucosylunits with -1,6-linked side chains (1, 2). Although a lot is already known about the mechanism of action of -1,3/1,6-glucans on the innate immune system (3, 4), there is still a lot to be learned about their effects on the adaptive immune system in mammals. We aimed to determine if oral supplementation could modulate a systemic immune response. The latter was examined in pigs using a model antigen, but also in dogs analyzing the response against a parenteral vaccine. In three experiments using newly weaned pigs, Macrogard, a β-1,3/1,6-glucan from Saccharomyces cerevisiae, was administered in the feed during three different time periods (one, two and three weeks) and the adjuvant effect of this β-glucan was determined on a systemic immunisation with thyroglobulin. A first immunisation occurred during β-glucan supplementation, while the second one occurred after ceasing the administration. Macrogard exerted significantly higher thyroglobulin-specific primary immunoglobulin (Ig) M and secondary IgA antibody responses in serum. However, Macrogard suppressed the thyroglobulin-specific proliferation of peripheral blood mononuclear cells. A higher dose of Macrogard significantly increased thyroglobulin-specific IgM but not IgA responses, and the animals itself showed hyperaemia. Suppression of the T-lymphocyte proliferation might account for the absence of the switch from IgM to IgA. Weight gain and feed conversion were also determined, without significant differences between groups. In another study, also dogs were orally given Macrogard in tablets, daily for four weeks. At the end of this period, the total serum IgA level decreased significantly in the group treated with the glucan compared to that in the control group as well as compared to the concentrations before supplementation. In contrast, the total serum IgM level rose significantly, whereas no effect on the IgG level occurred. Similar changes were seen in Bordetella-specific IgA and IgM titres following vaccination during the supplementation period. The IgA concentration also became significantly lower in the saliva and tears of the glucan group than in the placebo group. The effects disappeared one week after the cessation of the supplementation. There seems to be a temporary decrease in the switch from IgM to IgA due to oral Macrogard supplementation in dogs probably by its suppression of T-lymphocyte proliferation as seen in pigs. In conclusion, oral β-glucans are able to modulate the humoral as well as the cellular immunity against a systemically administered antigen

Oral β-1,3/1,6-glucans as immunmodulators in pigs

The cell wall glucans of yeasts and fungi consist of a linear backbone of -1,3-linked glucosylunits with -1,6-linked side chains (1). Although a lot is already known about the mechanism of action of -1,3/1,6-glucans on the innate immune system (2), there is still a lot to be learned about their effects on the adaptive immune system in mammals. We aimed to determine if oral supplementation could modulate a systemic immune response. The latter was examined in pigs using a model antigen. In three experiments using newly weaned pigs, Macrogard, a β-1,3/1,6-glucan from Saccharomyces cerevisiae, was administered in the feed during three different time periods (one, two and three weeks) and the adjuvant effect of this β-glucan was determined on a systemic immunisation with thyroglobulin. A first immunisation occurred during β-glucan supplementation, while the second one occurred after ceasing the administration. Macrogard exerted significantly higher thyroglobulin-specific primary immunoglobulin (Ig) M and secondary IgA antibody responses in serum. However, Macrogard suppressed the thyroglobulin-specific proliferation of peripheral blood mononuclear cells. A higher dose of Macrogard significantly increased thyroglobulin-specific IgM but not IgA responses, and the animals itself showed hyperaemia. Suppression of the T-lymphocyte proliferation might account for the absence of the switch from IgM to IgA. Weight gain and feed conversion were also determined, without significant differences between groups. In conclusion, oral β-glucans are able to modulate the humoral as well as the cellular immunity against a systemically administered antigen

Analysis for prevalence and physical linkages amongst integrons, ISEcp1, ISCR1, Tn21 and Tn7 encountered in Escherichia coli strains from hospitalized and non-hospitalized patients in Kenya during a 19-year period (1992-2011)

Background: We determined the prevalence and evidence for physical linkage amongst integrons, insertion sequences, Tn21 and Tn7 transposons in a collection of 1327 E. coli obtained over a 19-year period from patients in Kenya. Results: The prevalence of class 1 integrons was 35%, class 2 integrons were detected in 3 isolates but no isolate contained a class 3 integron. Integron lacking the 3'-CS or those linked to sul3 gene or IS26 or those containing the ISCR1 were only detected in multidrug resistant (MDR) strains. The dfrAs were the most common cassettes and their prevalence was: -dfrA1( 28%), dfrA12( 20%), dfA17( 9%), dfrA7( 9%), and dfrA16( 5%). The aadA were the second most abundant cassettes and their prevalence was: -aadA1( 25%), aadA2( 21%), and aadA5( 14%). Other cassettes occurred in lower prevalence of below 5%. Prevalence of Tn21, ISEcp1, ISCR1 and IS26 was 22%, 10%, 15%, and 7% respectively. Majority of Tn21 containing integrons carried a complete set of transposition genes while class 2 integrons were borne on Tn7 transposon. The qnrA genes were detected in 34( 3%) isolates while 19( 1%) carried qnrB. All qnr genes were in MDR strains carrying integrons containing the ISCR1. Close to 88% of blaTEM-52 were linked to IS26 while = 80% of blaCTX-Ms and blaCMYs were linked to ISEcp1. Only a few studies have identified a blaCTX-M-9 containing an ISEcp1 element as reported in this study. Multiple genetic elements, especially those borne on incIl, incFII, and incL/M plasmids, and their associated resistance genes were transferrable en bloc to E. coli strain J53 in mating experiments. Conclusions: This is the first detailed study on the prevalence of selected elements implicated in evolution of resistance determinants in a large collection of clinical E. coli in Africa. Proliferation of such strains carrying multiple resistance elements is likely to compromise the use of affordable and available treatment options for majority of poor patients in Africa. There is therefore a need to monitor the spread of these highly resistant strains in developing countries through proper infection control and appropriate use of antimicrobials

Passive immunization against Histomonas meleagridis does not protect turkeys from an experimental infection

Histomonosis or blackhead is a disease of gallinaceous birds, caused by the protozoan Histomonas meleagridis. As recent regulatory action has removed almost all drugs against this disease from the European market, the development of new prophylactics has become crucial. Identification of the protective immune mechanism would facilitate the choice and development of a vaccination strategy to prevent histomonosis. In this study, turkeys were either actively or passively immunized and were then challenged to assess the role of antibody-mediated immunity in the protection form this disease. Active immunization was performed either by experimental infection and treatment or by intramuscular injection with lysed H. meleagridis. Passive immunization was attempted by intraperitoneal administration of pooled, concentrated, neutralizing antisera from immunized donor animals to naive turkeys. A significantly higher IgG response was observed after infection and treatment than after intramuscular injection, which in turn was higher than the responses of placebo and control birds. While active immunization of turkeys by intramuscular injection of dead H. meleagridis antigens appeared not to be protective against histomonosis, immunization by infection and treatment did induce protection. However, no significant level of protection could be observed in the passively immunized birds. These results suggest that serum antibodies to H. meleagridis may not be a key component in the protection against this parasite. It is, however, possible that the concentration of antibodies at the mucosal site is insufficient. Therefore, further investigation on mucosal immune responses is necessary