A simplified procedure for studies of intestinal immunity in rabbits

Oral immunization of mice with plant-derived fimbrial adhesin FaeG induces systemic and mucosal K88ad enterotoxigenic Escherichia coli-specific immune responses

The importance of adhesins in pathogenicity has resulted in them being useful targets in the defense against bacterial infections. To produce edible vaccines against piglet diarrhea caused by enterotoxigenic Escherichia coli (ETEC), plants were genetically engineered to produce recombinant fimbrial adhesin FaeG. To evaluate the efficacy of the edible vaccine FaeG in mice, the soluble protein extracts were examined by about 15 microg recombinant FaeG for each oral immunization dose per mouse. After four doses of vaccination, both IgG and IgA antibodies specific to K88ad fimbriae were elicited in serum, and specific IgA antibodies were also evoked in feces of the immunized mice. Moreover, visible K88ad ETEC agglutination by the specific serum from the immunized mice was observed, implying the antibody was highly specific and effective. Results from an in vitro villous-adhesion assay further confirmed that serum antibodies of the immunized mice could inhibit K88ad ETEC from adhering to pig intestinal receptors, further demonstrating the oral immune efficacy of the plant-derived FaeG. This study provides a promising, noninvasive method for vaccinating swine by feeding supplements of transgenic plant. Moreover, the low cost and ease of delivery of this edible ETEC vaccine will facilitate its application in economically disadvantaged regions.

Multiple intestinal 'loops' provide an in vivo model to analyse multiple mucosal immune responses

Mucosal immunity plays an important role in preventing disease but the induction of protective mucosal immune responses remains a significant challenge. We describe a novel in vivo model to analyze the induction of multiple mucosal immune responses in the small intestine. A sterile segment of intestine ('intestinal-segment'; 2-3 m long) was surgically prepared in the jejunum of 4-6-month-old lambs. This 'intestinal-segment' was then subdivided into consecutive segments, designated as 'loops' (15-20 cm long), that included a Peyer's patch (PP), or 'interspaces' (15-70 cm long), that lacked a visible PP. All 'loops' were sterile when collected 1-4 weeks post-surgery and there was no macroscopic or histological evidence of altered lymph or blood flow. Flow cytometric analysis of cells isolated from PP, mucosal epithelium (IEL) and the lamina propria (LPL) revealed no significant alterations in the cell populations present in 'loop' tissues. The functional integrity of M-cell antigen uptake in sterile intestinal 'loops' was evaluated by comparing the immune response induced by varying doses of soluble versus particulate porcine serum albumin (PSA formulated in alginate microspheres). A dose-dependent, PSA-specific antibody-secreting cell response was restricted to PP present in 'loops' injected with particulate PSA. These observations suggested that PP present in sterile 'loops' were functional and this conclusion was confirmed by detecting cholera toxin-specific antibody-secreting cells and secreted antibody in PP and intestinal contents, respectively, of immunized 'loops.' Thus, each 'loop' provided an independent site to analyze antigen-uptake and the induction of mucosal immune responses by a variety of antigen or vaccine formulations.

The complete cDNA sequences of IL-2, IL-4, IL-6 AND IL-10 from the European rabbit (Oryctolagus cuniculus)

The cDNAs for four rabbit cytokine genes [interleukin 2 (IL-2), IL-4, IL-6 and IL-10] have been cloned from primary lymphocytes by polymerase chain reaction (PCR) methods. IL-2 and IL-10 are both highly conserved between rabbit and other species. IL-4 and IL-6 are less strongly conserved, at both nucleotide and amino acid levels, and exhibit structural differences. An extension of the coding region of rabbit IL-6 relative to all other reported IL-6 genes results from a mutation in the usual stop codon which allows translation to continue for a further 27 amino acids. Analysis of IL-6 from four other lagomorph species suggests that this mutation is specific to the European rabbit. Sequence and structural differences of IL-4 and IL-6, while presumably not altering function, may render them highly species-specific. Several alternatively spliced variants of IL-2 and IL-4 are also reported.

Ileal and jejunal Peyer's patches play distinct roles in mucosal immunity of sheep

The majority of pathogens enter the body through mucosal surfaces and it is now evident that mucosal immunity can provide effective disease protection. However, the induction of mucosal immunity will require efficient targeting of mucosal vaccines to appropriate mucosa-associated lymphoid tissue. An animal model, based upon the surgical preparation of sterile intestinal 'loops' (blind-ended segments of intestine), was developed to evaluate mucosal and systemic immune responses to enteric vaccines in ruminants. The effectiveness of end-to-end intestinal anastomoses was evaluated and fetal surgery did not disrupt normal intestinal function in lambs up to 6-7 months after birth. The immunological competence of Peyer's patches (PP) within the intestinal 'loops' was evaluated with a human adenovirus 5 vector expressing the gD gene of bovine herpesvirus-1. This vaccine vector induced both mucosal and systemic immune responses when injected into intestinal 'loops' of 5-6-week-old lambs. Antibodies to the gD protein were detected in the lumen of intestinal 'loops' and serum and PP lymphocytes proliferated in response to gD protein. The immune competence of ileal and jejunal PP was compared and these analyses confirmed that jejunal PP are an efficient site for the induction of mucosal immune responses. This was confirmed by the presence of gD-specific antibody-secreting cells in jejunal but not ileal PP. Systemic but not mucosal immune responses were detected when the vaccine vector was delivered to the ileal PP. In conclusion, this model provided an effective means to evaluate the immunogenicity of potential oral vaccines and to assess the immunological competence of ileal and jejunal Peyer's patches.