We studied the mammary immune response to different mammary pathogenic Escherichia coli (MPEC) strains in cows, hypothesising that the dynamics of response would differ. E. coli is a major aetiologic agent of acute clinical bovine mastitis of various degrees of severity with specific strains being associated with persistent infections. We compared challenge with three distinct pathogenic MPEC strains (VL2874, VL2732 and P4), isolated from different forms of mastitis (per-acute, persistent and acute, respectively). A secondary objective was to verify the lack of mammary pathogenicity of an environmental isolate (K71) that is used for comparison against MPEC in genomic and phenotypic studies. Twelve cows were challenged by intra-mammary infusion with one of the strains. Cellular and chemokine responses and bacterial culture follow-up were performed for 35 d. All cows challenged by any of the MPEC strains developed clinical mastitis. Differences were found in the intensity and duration of response, in somatic cell count, secreted cytokines (TNF-α, IL-6 and IL-17) and levels of milk leucocyte membrane Toll-like receptor 4 (TLR4). A sharp decrease of TLR4 on leucocytes was observed concomitantly to peak bacterial counts in milk. Intra-mammary infusion of strain K71 did not elicit inflammation and bacteria were not recovered from milk. Results suggest some differences in the mammary immune response to distinct MPEC strains that could be correlated to their previously observed pathogenic traits. This is also the first report of an E. coli strain that is non-pathogenic to the bovine mammary gland. © Proprietors of Journal of Dairy Research 2017.

Heterophil/lymphocyte (H/L ratio) statistics and total white blood cell counts (TWBC) determined by light microscopic examination of blood from isolator raised specific pathogen free (SPF) chicks indicated complex hemograms. Brachial vein blood (N =12) obtained at 6 wk was spread into films, air dried, post-fixed in MeOH and Wright’s stained. H/L 1 ratios were calculated by dividing all heterophil types, typical (HT) variant (HV) and classic (HC) by the number of small (resting) lymphocytes (Ls) H/L 1 = (HT + HV + HC)/(Ls). A second ratio (H/L 2) obtained by dividing heterophils by all lymphocytes (resting, reactive and atypical, (HT + HV + HC)/ (Ls + Lm) was calculated; as was the H/L 1-H/L 2 difference (ΔH/L). TWBC’s were determined from the same films. Sorting, non-random distribution of cells and atypia affected all H/L statistics. The mean H/L 1 ratio from standard differential counts (SDC) = 0.17 and H/L 2 = 0.16. Edge based ratios (EB) were  8 times the SDC values. Atypical cells were in all samples and more common in EB counts. The H/L ratios and ΔH/L calculated from SDC and EB values were significantly different (p<0.02). Collectively these observations support earlier conclusions regarding the lack of sensitivity of a single H/L ratio, without a TWBC, or consideration of atypia to estimate welfare. Furthermore, hemograms of SPF chickens reared in isolation may be complex. © Asian Network for Scientific Information, 2016.

Avian reovirus (ARV) is a disease-causing agent. The disease is prevented by vaccination with a genotype-specific vaccine while many variants of ARV exist in the field worldwide. Production of new attenuated vaccines is a long-term process and in the case of fast-mutating viruses, an impractical one. In the era of molecular biology, vaccines may be produced by using only the relevant protein for induction of neutralizing antibodies, enabling fast adjustment to the emergence of new genetic strains. Sigma C (SC) protein of ARV is a homotrimer that facilitates host-cell attachment and induce the production and secretion of neutralizing antibodies. The aim of this study was to identify the region of SC that will elicit a protective immune response. Full-length (residues 1-326) and two partial fragments of SC (residues 122-326 and 192-326) were produced in Escherichia coli. The SC fragment of residues 122-326 include the globular head, shaft and hinge domains, while eliminating intra-capsular region. This fragment induces significantly higher levels of anti-ARV antibodies than the shorter fragment or full length SC, which neutralized embryos infection by the virulent strain to a higher extent compared with the antibodies produced in response to the whole virus vaccine. Residues 122-326 fragment is assumed to be folded correctly, exposing linear as well as conformational epitopes that are identical to those of the native protein, while possibly excluding suppressor sequences. The results of this study may serve for the development of a recombinant subunit vaccine for ARV. © 2016 Elsevier Ltd.