T-cell epitope content comparison (EpiCC) of swine H1 influenza A virus hemagglutinin.

BACKGROUND: Predicting vaccine efficacy against emerging pathogen strains is a significant problem in human and animal vaccine design. T-cell epitope cross-conservation may play an important role in cross-strain vaccine efficacy. While influenza A virus (IAV) hemagglutination inhibition (HI) antibody titers are widely used to predict protective efficacy of 1 IAV vaccine against new strains, no similar correlate of protection has been identified for T-cell epitopes. OBJECTIVE: We developed a computational method (EpiCC) that facilitates pairwise comparison of protein sequences based on an immunological property-T-cell epitope content-rather than sequence identity, and evaluated its ability to classify swine IAV strain relatedness to estimate cross-protective potential of a vaccine strain for circulating viruses. METHODS: T-cell epitope relatedness scores were assessed for 23 IAV HA sequences representing the major H1 swine IAV phylo-clusters circulating in North American swine and HA sequences in a commercial inactivated vaccine (FluSure XP® ). Scores were compared to experimental data from previous efficacy studies. RESULTS: Higher EpiCC scores were associated with greater protection by the vaccine against strains for 23 field IAV strain vaccine comparisons. A threshold for EpiCC relatedness associated with full or partial protection in the absence of cross-reactive HI antibodies was identified. EpiCC scores for field strains for which FluSure protective efficacy is not yet available were also calculated. CONCLUSION: EpiCC thresholds can be evaluated for predictive accuracy of protection in future efficacy studies. EpiCC may also complement HI cross-reactivity and phylogeny for selection of influenza strains in vaccine development.

Two clinical isolates of Mycoplasma hyosynoviae showed differing pattern of lameness and pathogen detection in experimentally challenged pigs.

Mycoplasma (M.) hyosynoviae is known to colonize and cause disease in growing-finishing pigs. In this study, two clinical isolates of M. hyosynoviae were compared by inoculating cesarean-derived colostrum-deprived and specific-pathogen-free growing pigs. After intranasal or intravenous inoculation, the proportion and distribution pattern of clinical cases was compared in addition to the severity of lameness. Tonsils were found to be the primary site of colonization, while bacteremia was rarely detected prior to the observation of clinical signs. Regardless of the clinical isolate, route of inoculation, or volume of inocula, histopathological alterations and tissue invasion were detected in multiple joints, indicating an apparent lack of specific joint tropism. Acute disease was primarily observed 7 to 10 days post-inoculation. The variability in the severity of synovial microscopic lesions and pathogen detection in joint cavities suggests that the duration of joint infection may influence the diagnostic accuracy. In summary, these findings demonstrate that diagnosis of M. hyosynoviae-associated arthritis can be influenced by the clinical isolate, and provides a study platform to investigate the colonization and virulence potential of field isolates. This approach can be particularly relevant to auxiliate in surveillance and testing of therapeutic and/or vaccine candidates.

In vivo evaluation of vaccine efficacy against challenge with a contemporary field isolate from the α cluster of H1N1 swine influenza virus.

Influenza A virus vaccines currently contain a mixture of isolates that reflect the genetic and antigenic characteristics of the currently circulating strains. This study was conducted to evaluate the efficacy of a trivalent inactivated swine influenza virus vaccine (Flusure XP) in pigs challenged with a contemporary α-cluster H1N1 field isolate of Canadian swine origin. Pigs were allocated to vaccinated, placebo, and negative-control groups and monitored for respiratory disease for 5 d after challenge. On the challenge day and 5 d after challenge the serum of the vaccinated pigs had reciprocal hemagglutination inhibition antibody titers 40 for all the vaccine viruses but ≤ 20 for the challenge virus. Gross lesions were present in the lungs of all pigs that had been inoculated with the challenge virus, but the proportion of lung tissue consolidated did not differ significantly between the placebo and vaccinated pigs. However, the amount of virus was significantly reduced in the nasal secretions, lungs, and bronchoalveolar lavage fluid in the vaccinated pigs compared with the placebo pigs. These results indicate that swine vaccinated with Flusure XP were partially protected against experimental challenge with a swine α-cluster H1N1 virus that is genetically similar to viruses currently circulating in Canadian swine.

Les vaccins actuels contre l'influenza A contiennent un mélange d'isolats qui reflète les caractéristiques génétiques et antigéniques des souches actuellement en circulation. La présente étude a été réalisée afin d'évaluer l'efficacité d'un vaccin inactivé trivalent contre le virus de l'influenza porcin (Flusure XP) chez des porcs challengés avec un isolat terrain du virus de l'influenza de la grappe α du type H1N1 provenant d'un porc d'origine canadienne. Des porcs ont été répartis dans un des trois groupes suivants : vacciné, placebo ou témoin négatif; et examinés pour problèmes respiratoires pendant 5 jours après le challenge. Le jour du challenge et le 5e jour suivant le challenge, on retrouvait dans le sérum des porcs vaccinés des titres réciproques d'anticorps hémagglutinants 40 pour tous les virus vaccinaux mais ≤ 20 pour le virus ayant servi au challenge. Des lésions macroscopiques étaient présentes dans les poumons de tous les porcs qui avaient été inoculés avec le virus servant pour le challenge, mais il n'y avait pas de différence significative dans la proportion de tissu pulmonaire consolidé entre le groupe vacciné et le groupe placebo. Toutefois, la quantité de virus était réduite de manière significative dans les sécrétions nasales, les poumons et le liquide des lavages broncho-alvéolaires des porcs vaccinés comparativement aux porcs du groupe placebo. Ces résultats indiquent que les porcs vaccinés avec Flusure XP étaient partiellement protégés contre une infection expérimentale avec un virus H1N1 porcin de la grappe α qui est génétiquement similaire aux virus qui circulent actuellement chez les porcs canadiens.(Traduit par Docteur Serge Messier).

A novel signature-tagged mutagenesis system for Streptococcus suis serotype 2.

Streptococcus suis is an economically important, zoonotic pathogen causing death and disease in swine. The objectives of this study were to develop a signature-tagged mutagenesis (STM) system for S. suis serotype 2 and to identify genes required for in vivo virulence. Identification of such candidate genes may lead to a better understanding of the pathogenesis of S. suis and may provide substrate for the discovery of new vaccines. A novel STM approach was designed to allow for a higher throughput assay of mutants using the Luminex xMAP system. Additionally, to speed the identification process, a direct genomic DNA sequencing method was developed that overcomes the problems associated with the presence of repetitive insertion sequences. Approximately 2600 mutants were screened through both mouse and caesarian-derived, colostrum-deprived (CDCD) pig models. The disrupted ORF was identified for each potential attenuated mutant, and mutants with distinct and unique mutated ORFs were analyzed individually for attenuation in mouse and CDCD pig models. A variety of genes were identified, including previously known genes essential to the virulence of other organisms, genes involved in capsule biosynthesis, a regulator of suilysin expression, and several conserved or predicted genes. Of the 22 mutants identified as attenuated in either animal model, eight insertion mutants caused no mortality in both mouse and pig models.