Location: Virus and Prion Research2012 Annual Report
1a. Objectives (from AD-416):
Evaluate swine influenza virus strain specific antigenic epitopes that might enable development of serological assays for pandemic H1N1 surveillance in swine. Evaluate selected antigenic epitopes and genetic factors of swine influenza virus that may lead to heterologous immunity elicited by influenza vaccines to enable development of improved vaccines with broader protective immunity against novel emerging influenza strains.
1b. Approach (from AD-416):
Conduct immunological investigations of influenza A virus components that lead to immune responses against specific epitopes that may enable serological surveillance for the 2009 A/H1N1 in swine and determine whether heterologous immunity against endemic swine influenza viruses interferes with serological surveillance methods. Collaborate in conducting animal studies to determine the pathogenesis and transmissibility of selected isolates of the wild-type novel A/HINI virus from animals and correlate with genetic and antigenic changes.
3. Progress Report:
Objective 1: 1. Identify antigenic epitopes which are unique to and fixed in the pH1N1 nucleoprotein (NP) protein and the matrix (M2) protein. 2. Develop a pH1N1- specific antibody detection ELISA based on the identified epitopes. All of the specific aims for Objective 1 have been completed. This was a very high risk objective given the known rate of mutation for RNA viruses like influenza and after extensive experimentation. Ultimately, as we predicted, it was not possible to overcome cross reactivity with other endemic swine influenza viruses to create a robust pH1N1 specific immunoassay using synthetic peptides. Given the number of reassortant viruses now circulating in swine globally, the research on this objective is now suspended as it is no longer relevant and all original work scheduled to be done is complete. Objective 2: 1. Evaluate T cell mediated immune responses induced by conventional inactivated swine influenza vaccines against emerging isolates of pandemic A/H1Nl from animals (e.g., Canadian, Chilean and Argentinean viruses). 2. Evaluate T cell mediated immune responses induced by a reverse genetics-derived modified live vaccine in pigs and other susceptible animal hosts against pandemic A/H1N1. 3. Evaluate T cell mediated immune responses induced by an adenovirus-vectored influenza virus vaccine in pigs. Towards furthering our understanding of heterologous, T cell mediated immune responses studied under Objective 2, Iowa State University (ISU) scientists collaborated with ARS scientists at the National Animal Disease Center (NADC) in Ames, Iowa in conducting a large study designed to investigate vaccine-associated enhanced respiratory disease (VAERD) in pigs that were primed with an swine influenza virus (SIV) vaccine and infected with pandemic H1N1 influenza (pH1N1). Variables included the form of SIV antigen used for vaccine (killed-adjuvanted, modified-live, or wild type virus) and the route of administration (intranasal or intramuscular). The primary objective of the study was to identify components of the cross-reactive immune response which correspond to protection versus disease enhancement, following heterologous infection with pH1N1. The researchers at ISU performed in vitro assays to quantify the priming of CD4+, CD8+, CD4+CD8+, and gamma delta T cells in a total of 112 pigs (lymph node cell suspensions and peripheral blood mononuclear cells). This research included analysis of flow cytometry data acquired from in vitro assays of blood and lymphoid cells stimulated with several antigens from approximately 2000 sample tests, each of which contains 4 T-cell subsets and 3 cell activation phenotypes. The NADC-ISU collaborative team has mapped a plan for publication of the many results from this study in two manuscripts, which are in progress. One manuscript will describe the outcome of pH1N1 challenge (viral replication, lung pathology, clinical disease) in pigs that were vaccinated with antigenically dissimilar killed or modified-live vaccines. The other manuscript will build on the first by characterizing immunological responses of pigs to the vaccines that either protected or caused VAERD.