Location: Virus and Prion Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Identify the transmission, genetic, and pathogenic mechanisms of the organisms associated with PRDC, concentrating on the bacterial pathogens and their interactions with each other and select swine viruses. Subobjective 1.1: Identify potential virulence factors of H. parasuis through comparative genomics. Subobjective 1.2: Bacterial response to host conditions. Subobjective 1.3: Evaluate ability of PRDC bacterial pathogens to inhibit Influenza A virus vaccine efficacy and/or exacerbate Influenza A virus-associated disease. Objective 2: Identify potential candidates for novel diagnostic assays, vaccines, and biotherapeutics for bacterial pathogens associated with PRDC. Subobjective 2.1. Develop PCR, ELISA, and/or other assays for detection of bacterial pathogens associated with PRDC. Subobjective 2.2. Identify, develop and/or test the efficacy of potential vaccine candidates to control bacterial pathogens associated with PRDC. Subobjective 2.3. Identify potential biotherapeutic candidates to control bacterial pathogens associated with PRDC. Objective 3: Investigate emerging and potential zoonotic bacterial pathogens that could impact the swine industry and design measures to diagnose, prevent, control and eliminate the threat posed to the swine industry. Subobjective 3.1. Evaluate the relationship between highly pathogenic Asian strains of PRRSV and S. suis infection in swine. Subobjective 3.2: Identification of measures that may prevent, control, or eliminate livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) Sequence Type 398 (ST398) in swine.
1b. Approach (from AD-416):
Use comparative genomic methods, microarray analysis, and co-infection studies to explore pathogenic mechanisms of bacteria associated with the porcine respiratory disease complex and their interactions with each other and swine viruses. Assess the usefulness of selected genes or proteins identified in comparative genomic analyses for DNA-based identification and classification, serological detection of infection, and potentially as vaccine candidates. Strategies for improved heterologous protection will be tested using live attenuated vaccines, as will the use of immunomodulators, such as granulocyte colony stimulating factor (G-CSF), for therapeutic, prophylactic, and metaphylactic use to prevent and combat infectious disease and thus reduce antimicrobial usage to treat clinical and subclinical disease. Investigate emerging and potential zoonotic bacteria that could impact the swine industry. Investigations will focus on pathogen strain characteristics and differences, interactions of bacterial and viral pathogens with the swine host and the microbial ecosystems of the pig. Pathology of both zoonotic and endemic bacterial pathogens of swine will be utilized for the purpose of understanding disease pathogenesis and developing effective diagnostic assays and strategies to control these pathogens and diseases in swine and potentially in humans.
3. Progress Report:
We continued genomic sequencing efforts for Haemophilus parasuis (HPS). We now have annotated draft genomes for 10 strains of HPS, and are in the process of comparing the relative virulence of all these isolates in both animal model systems and in vitro assays. This will provide meaningful data on which to base genomic comparisons. These efforts support subobjective 1.1. We constructed a HPS DNA microarray using genome sequence information from isolate SH0165 and other isolates that we have sequenced and confirmed its functionality. Working with a collaborator at the University of California, Santa Barbara Westmont College, we used our Bordetella-specific microarray to identify the genes regulated by a newly identified two-component transactional regulatory system shared between both B. bronchiseptica and B. pertussis. These efforts support subobjective 1.2. Viral infection is thought to predispose the host to secondary infection with bacteria. We have continued to investigate when and how swine influenza virus by itself and as a component of vaccine associated enhanced respiratory disease predisposes pigs to secondary bacterial pneumonia. These efforts support subobjective 1.3. We cloned and expressed recombinant P2 and P5 proteins from a virulent and avirulent isolate of HPS. The respective P2 and P5 alleles are highly divergent and represent different major clades in a phylogeny based on the DNA sequence. We began evaluating the immunogenicity of different HPS outer membrane proteins that may be of value in diagnostic assays and/or as vaccines. We initiated construction of a novel suicide vector for the purpose of generating markerless mutations in HPS. We completed cloning the bsp22 gene from B. bronchiseptica that encodes a Type 3 secretion needle protein that was shown to be immunogenic in mice, and a recombinant replication-defective adenovirus vaccine vector expressing the protein has been generated for testing in pigs. These efforts support subobjectives 2.1.and 2.2. We also completed initial experiments evaluating protection provided by the administration of Granulocyte-Colony Stimulating Factor, a compound that enhances immunity against bacterial infections by increasing the number of circulating neutrophils. These efforts support subobjective 2.3. We completed a swine experiment designed to compare 2 Asian isolates of porcine reproductive and respiratory syndrome virus obtained from the porcine high fever disease outbreaks to high and low virulence isolates obtained from the United States for their alteration of innate immune functions and their ability to predispose to secondary bacterial infections in swine. This experiment supports subobjective 3.1. We completed studies investigating the ability of ST398 methicillin-resistant S. aureus (MRSA) swine isolates to form biofilms and mechanisms to disperse or eliminate biofilms that could be used or evaluated in vivo in the future. In collaboration with scientists at the New Jersey Dental School, we tested the ability of an exopolysaccharide prepared from a nonpathogenic bacterium to inhibit biofilm formation by ST398 MRSA swine isolates. These efforts support subobjective 3.2.
Brockmeier, S.L., Loving, C.L., Nelson, E.A., Miller, L.C., Nicholson, T.L., Register, K.B., Grubman, M.J., Brough, D.E., Kehrli, Jr., M.E. 2012. The presence of alpha interferon at the time of infection alters the innate and adaptive immune responses to porcine reproductive and respiratory syndrome virus. Clinical and Vaccine Immunology. 19(4):508-514.