Iron is a vital nutrient for virtually all forms of life. The requirement for iron is based on its role in cellular processes ranging from energy generation and DNA replication to oxygen transport and protection against oxidative stress. Bacterial pathogens are not exempt from this iron requirement, as these organisms must acquire iron within their vertebrate hosts in order to replicate and cause disease.

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The battle for iron between bacterial pathogens and their vertebrate hosts.

Salmonella constitutes a genus of zoonotic bacteria of worldwide economic and health importance. The current view of salmonella taxonomy assigns the members of this genus to two species: S. enterica and S. bongori. S. enterica itself is divided into six subspecies, enterica , salamae , arizonae , diarizonae , indica , and houtenae , also known as subspecies I, II, IIIa, IIIb, IV, and VI, respectively. Members of Salmonella enterica subspecies enterica are mainly associated with warm-blooded vertebrates and are usually transmitted by ingestion of food or water contaminated by infected faeces. The pathogenicity of most of the distinct serotypes remains undefined, and even within the most common serotypes, many questions remain to be answered regarding the interactions between the organism and the infected host.

Salmonellosis manifests itself in three major forms: enteritis, septicaemia, and abortion, each of which may be present singly or in combination, depending on both the serotype and the host involved. Although currently over 2300 serovars of Salmonella are recognized, only about 50 serotypes are isolated in any significant numbers as human or animal pathogens and they all belong to subspecies enterica . Of these, most cause acute gastroenteritis characterized by a short incubation period and a severe systemic disease in man or animals, characterized by septicaemia, fever and/or abortion, and such serotypes are often associated with one or few host species.

It is the intention of this review to present a summary of current knowledge of these host-adapted serotypes of S. enterica . The taxonomic relationships between the serotypes will be discussed together with a comparison of the pathology and pathogenesis of the disease that they cause in their natural host(s). Since much of our knowledge on salmonellosis is based on the results of work on Typhimurium, this serotype will often be used as the baseline in discussion. It is hoped that an appreciation of the differences that exist in the way these serotypes interact with the host will lead to a greater understanding of the complex host–parasite relationship that characterizes salmonella infections.

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Host adapted serotypes of Salmonella enterica.

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Prostaglandins and reproduction in female farm animals.

The food contaminant deoxynivalenol, decreases intestinal barrier permeability and reduces claudin expression.

To determine the physiological significance of tumor necrosis factor a (TNFa) in the regulation of luteolytic prostaglandin (PG) F2a release by the bovine endometrium, the effect of TNFa on PGF2a output by the endometrial tissues in vitro was investigated and compared with the effect of oxytocin (OT). Furthermore, the presence of specific receptors for TNFa in the bovine endometrium during the estrous cycle was determined. Endometrial slices (20‐30 mg) taken from six stages of the estrous cycle (estrus: Day 0; early I: Days 2‐3; early II: Days 5‐ 6; mid-: Days 8‐12; late: Days 15‐17; and follicular: Days 19‐ 21), as determined by macroscopic examination of the ovaries and uterus, were exposed to TNFa (0.06‐6 nM) and/or OT (100 nM). OT stimulated PGF2a output at the follicular stage and at estrus (P , 0.001), but not at the late luteal stage. On the other hand, the stimulatory effects of TNFa on PGF2a output were observed not only at the follicular stage but also at the late luteal stage (P , 0.001). When the endometrial tissues at late luteal stage were simultaneously exposed to TNFa (0.6 nM) and OT (100 nM), the stimulatory effect on PGF2a output was higher than the effect of TNFa or OT alone (P , 0.05). Specific binding of TNFa to the bovine endometrial membranes was observed throughout the estrous cycle. The concentration of TNF-a receptor at the early I luteal stage was less than the concentrations at other luteal stages (P , 0.01). The dissociation constant (Kd) values of the endometrial membranes were constant during the estrous cycle. The overall results lead us to hypothesize that TNFa may be a trigger for the output of PGF2a by the endometrium at the initiation of luteolysis in cattle.

https://bioone.org/journals/Biology-of-Reproduction/volume-62/issue-5/biolreprod62.5.1109/Is-Tumor-Necrosis-Factor-%ce%b1-a-Trigger-for-the-Initiation/10.1095/biolreprod62.5.1109.pdf

Is Tumor Necrosis Factor α a Trigger for the Initiation of Endometrial Prostaglandin F2α Release at Luteolysis in Cattle

Objective—To identify important pathogens and characterize their serologic and pathologic effects in porcine circovirus type 2 (PCV2)-infected pigs in relation to pig age and type of swine production system. Design—Cross-sectional study. Animals—583 conventionally reared pigs. Procedures—3- (n = 157), 9- (149), 16- (152), and 24-week-old (125) pigs from 41 different 1-, 2-, and 3-site production systems (5 pigs/age group/farm) were euthanized and necropsied. Pigs with and without PCV2 infection were identified (via PCR assay); infection with and serologic responses to other pathogens and pathologic changes in various tissues (including lungs) were assessed. Logistic regression models were constructed for effects overall and within each age group and type of production system. Results—Compared with PCV2-negative pigs, PCV2-positive pigs were more likely to have swine influenza virus (SIV) type A and Mycoplasma hyopneumoniae infections and sample-to-positive (S:P) ratios for SIV H1N1 from 0.50 to 0.99; also...

Epidemiologic assessment of porcine circovirus type 2 coinfection with other pathogens in swine.

The pig has proven to be a valuable model for biomedical research. Physiologic, anatomic, and pathologic similarities between pigs and humans create numerous research applications using the pig. Recent changes in the pork industry have created the need for research with direct applications to commercial pork production. The pig is a valuable research resource and will continue to be important in various research programs.

Research Applications using Pigs

This study was designed to investigate the effects of weaning age on specific components of the adaptive immune system in pigs. Twenty-three crossbred pigs were randomly assigned to 1 of 3 treatments: weaning at 14 (14D, n = 8), 21 (21D, n = 7), or 28 (28D, n = 8) d of age. Peripheral blood samples, obtained when pigs were 13, 15, 20, 22, 27, 29, and 35 d of age, were analyzed for peripheral blood cell percentages and concentrations of neutrophils, lymphocytes, T cell subsets, mature B cells, and plasma cortisol concentrations. For each of the 3 groups, weaning increased plasma cortisol concentrations (P < 0.001) and reduced BW percentage change (P < 0.017). Lymphocyte concentrations displayed a treatment effect for the 14D (P = 0.074) and 28D (P = 0.014) groups. Albeit inconsistent, lymphocyte concentrations were less in weaned pigs on the day after weaning than in pigs remaining on the sow or weaned at a younger age. Specifically, mature B cells (CD21(+)) and CD4(+)CD8(+) cells decreased (P < 0.05) after weaning at 28 d of age. Other differences occurred among treatments; however, the differences apparently were not associated with weaning. Based upon the immunological measures used in the present study, there was not an explicit benefit to the adaptive immune system for any weaning age. Early weaning did not negatively affect the adaptive immunological competence of pigs as determined by changes in populations of immune cells.

Effects of stress associated with weaning on the adaptive immune system in pigs.

Angiogenesis is an essential process during follicular development and corpora lutea (CL) formation. Recent studies have shown that vascular endothelial growth factor (VEGF) is an essential regulator of ovarian angiogenesis. Several lines of evidence have indicated that the production of VEGF is regulated by hypoxia inducible factor-1alpha (HIF-1alpha), especially under hypoxic conditions, but the expression of HIF-1alpha has not been well characterized in the porcine ovary. The present study examined the expression of HIF-1alpha mRNA and its localization in porcine ovaries at different stages of the estrous cycle. Northern blot analyses of total CL RNA indicated hybridization of the porcine HIF-1alpha probe to transcripts of approximately 3.8 kb. The mRNA expression of HIF-1alpha was highest in CL during the early luteal phase, followed by a decrease during the mid- and late-luteal phases. Using in situ hybridization, abundant HIF-1alpha mRNA was evident in follicles and CL. Within non-atretic follicles, HIF-1alpha mRNA was highly expressed in the granulosa cell layer, while weaker labeling was evident in the theca interna. These results suggest that HIF-1alpha may play a role in the regulation of cellular metabolism and blood supply during follicular growth and CL formation.

Expression and localization of hypoxia inducible factor-1alpha mRNA in the porcine ovary.

The etiologic agent of chancroid is Haemophilus ducreyi. To fulfill its obligate requirement for heme, H. ducreyi uses two TonB-dependent receptors: the hemoglobin receptor (HgbA) and a receptor for free heme (TdhA). Expression of HgbA is necessary for H. ducreyi to survive and initiate disease in a human model of chancroid. In this study, we used a swine model of H. ducreyi infection to demonstrate that an experimental HgbA vaccine efficiently prevents chancroid, as determined by several parameters. Histological sections of immunized animals lacked typical microscopic features of chancroid. All inoculated sites from mock-immunized pigs yielded viable H. ducreyi cells, whereas no viable H. ducreyi cells were recovered from inoculated sites of HgbA-immunized pigs. Antibodies from sera of HgbA-immunized animals bound to and initiated antibody-dependent bactericidal activity against homologous H. ducreyi strain 35000HP and heterologous strain CIP542 ATCC; however, an isogenic hgbA mutant of 35000HP was not killed, proving specificity. Anti-HgbA immunoglobulin G blocked hemoglobin binding to the HgbA receptor, suggesting a novel mechanism of protection through the limitation of heme/iron acquisition by H. ducreyi. Such a vaccine strategy might be applied to other bacterial pathogens with strict heme/iron requirements. Taken together, these data suggest continuing the development of an HgbA subunit vaccine to prevent chancroid.

Glen W. Almond

Papers

Epidemiologic assessment of porcine circovirus type 2 coinfection with other pathogens in swine.

Research Applications using Pigs

Effects of stress associated with weaning on the adaptive immune system in pigs.

Expression and localization of hypoxia inducible factor-1alpha mRNA in the porcine ovary.

Immunization with the Haemophilus ducreyi Hemoglobin Receptor HgbA Protects against Infection in the Swine Model of Chancroid