Salmonella typhimurium and Campylobacter jejuni pose significant risks to human health and poultry are a major vector for infection. Comparative in vivo infection models were performed to compare the avian host immune response to both bacterial species. Forty-five commercial broiler chickens were orally challenged with either C. jejuni or S. typhimurium whilst 60 similar control birds were mock challenged in parallel. Birds were sacrificed at 0, 6, 20 and 48 h post-infection and cloacal swabs, blood and tissue samples taken. Peripheral blood leukocytes were isolated for flow cytometric analyses and RNA was extracted for gene expression profiling. Colonisation patterns were markedly different between the two bacterial species, with systemic colonisation of Campylobacter outside the gastrointestinal tract. Salmonella infection induced significant changes in circulating heterophil and monocyte/macrophage populations, whilst Campylobacter infection had no effect on the heterophil numbers but caused a significant early increase in circulating monocytes/macrophages. Toll-like receptor 1 (TLR1) gene expression was decreased, and avian beta-defensin (AvBD) gene expression (AvBD3, AvBD10 and AvBD12) was significantly increased in response to Salmonella infection (P < 0.05). In contrast, Campylobacter infection induced increased TLR21 gene expression but significantly reduced expression of seven antimicrobial peptide (AMP) genes (AvBD3, AvBD4, AvBD8, AvBD13, AvBD14, CTHL2 and CTHL3; P < 0.05). Considered together, microbiological, cellular and gene expression profiles indicate that the innate immune system responds differently to Salmonella and to Campylobacter infection. Furthermore, reduction in the expression of AMPs may play a role in the persistence of high level colonisation of the host by Campylobacter.

Recent analysis of the bovine genome revealed an expanded suite of β-defensin genes that encode what are referred to as antimicrobial or host defense peptides (HDPs). Whereas primate genomes also encode α- and θ-defensins, the bovine genome contains only the β-defensin subfamily of HDPs. β-Defensins perform diverse functions that are critical to protection against pathogens but also in regulation of the immune response and reproduction. As the most comprehensively studied subclass of HDPs, β-defensins possess the widest taxonomic distribution, found in invertebrates as well as plants, indicating an ancient point of origin. Cross-species comparison of the genomic arrangement of β-defensin gene repertoire revealed them to vary in number among species presumably due to differences in pathogenic selective pressures but also genetic drift. β-Defensin genes exist in a single cluster in birds, but four gene clusters exist in dog, rat, mouse, and cow. In humans and chimpanzees, one of these clusters is split in two as a result of a primate-specific pericentric inversion producing five gene clusters. A cluster of β-defensin genes on bovine chromosome 13 has been recently characterized, and full genome sequencing has identified extensive gene copy number variation on chromosome 27. As a result, cattle have the most diverse repertoire of β-defensin genes so far identified, where four clusters contain at least 57 genes. This expansion of β-defensin HDPs may hold significant potential for combating infectious diseases and provides opportunities to harness their immunological and reproductive functions in commercial cattle populations.

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After calving, the bovine endometrium undergoes marked morphological and functional changes that are necessary for subsequent re-breeding. Regulation and integration of these key events are largely uncharacterised. Here, endometrial swabs and biopsies were taken at 15, 30 and 60 days postpartum (DPP) from 13 healthy primiparous cows, 10 of which subsequently conceived, with a view to characterising innate and inflammatory gene expression profiles. Endometrial biopsies exhibited severe inflammation (>75 leukocytes per high-power field) at 15 DPP, which had begun to resolve by 30 DPP and had completely resolved by 60 DPP. The severe inflammation at 15 DPP coincided with uterine infection in all cows and a significant increase (P < 0.05) in the expression of all of 16 genes investigated, including CD45, IL8, IL6, IL1, TNF, TAP, SAA3 and HP at 15 DPP, relative to 60 DPP. All of these parameters had begun to return to normal physiological levels at 30 DPP. Systemically, serum protein concentrations of IL-8 were elevated at 15 DPP compared with 60 DPP (78 pg mL–1 vs 48 pg mL–1; P = 0.02). These results indicate that endometrial inflammation, leukocyte infiltration and increased expression of pro-inflammatory, antimicrobial and acute-phase protein genes are expected features of the postpartum period, critical to bacterial clearance and uterine involution.

Bovine beta-defensin 126 (BBD126) exhibits preferential expression for the cauda epididymis of males, where it is absorbed onto the tail and postacrosomal region of the sperm. The aim of this study was to examine the role of BBD126 in bull sperm function. Fresh and frozen-thawed semen were incubated in the presence of different capacitating agents as well as with phosphatidylinositol-specific phospholipase C. These treatments, which have been successful in releasing beta-defensin 126 from macaque sperm, proved to be ineffective in bull sperm. This finding suggests that the protein behaves in a different manner in the bovine. The lack of success in removing BBD126 led us to use corpus epididymis sperm, a model in which the protein is not present, to study its functional role. Corpus sperm were incubated with cauda epididymal fluid (CEF) in the absence or presence of BBD126 antibody or with recombinant BBD126 (rBBD126). Confocal microscopy revealed that rBBD126 binds to corpus sperm with the same pattern observed for BBD126 in cauda sperm, whereas an aberrant binding pattern is observed when sperm are subject to CEF incubation. Addition of CEF increased motility as well as the number of corpus sperm migrating through cervical mucus from estrus cows. However, it decreased the ability of sperm to fertilize in vitro matured oocytes. The presence of the antibody failed to abrogate these effects. Furthermore, when rBBD126 was added in the absence of other factors and proteins from the CEF, an increase in motility was also observed and no negative effects in fertility were seen. These results suggest that BBD126 plays a key role in the acquisition of sperm motility in the epididymis.