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Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice
Published on: February 22, 2019
Comparative immunogenicity of M. hyopneumoniae NrdF encoded in different expression systems delivered orally via
Austen Y Chen1, Scott R Fry, Judy Forbes-Faulkner
1Department of Biological and Physical Sciences, University of Southern Queensland, Cnr Baker and West Street, Toowoomba, Qld 4350, Australia.
Abstract:
The Mycoplasma hyopneumoniae ribonucleotide reductase R2 subunit (NrdF) gene fragment was cloned into eukaryotic and prokaryotic expression vectors and its immunogenicity evaluated in mice immunized orally with attenuated Salmonella typhimurium aroA CS332 harboring either of the recombinant expression plasmids. We found that NrdF is highly conserved among M. hyopneumoniae strains. The immunogenicity of NrdF was examined by analyzing antibody responses in sera and lung washes, and the cell-mediated immune (CMI) response was assessed by determining the INF-gamma level produced by splenocytes upon in vitro stimulation with NrdF antigen. S. typhimurium expressing NrdF encoded by the prokaryotic expression plasmid (pTrcNrdF) failed to elicit an NrdF-specific serum or secretory antibody response, and IFN-gamma was not produced. Similarly, S. typhimurium carrying the eukaryotic recombinant plasmid encoding NrdF (pcNrdF) did not induce a serum or secretory antibody response, but did elicit significant NrdF-specific IFN-gamma production, indicating induction of a CMI response. However, analysis of immune responses against the live vector S. typhimurium aroA CS332 showed a serum IgG response but no mucosal IgA response in spite of its efficient invasiveness in vitro. In the present study we show that the DNA vaccine encoding the M. hyopneumoniae antigen delivered orally via a live attenuated S. typhimurium aroA can induce a cell-mediated immune response. We also indicate that different live bacterial vaccine carriers may have an influence on the type of the immune response induced.
Insights
Oral vaccination with a DNA vaccine encoding Mycoplasma hyopneumoniae NrdF antigen, delivered via attenuated Salmonella, successfully induced a cell-mediated immune response in mice, highlighting the potential of live bacterial carriers for vaccine development.
Area of Science:
- Veterinary Immunology
- Bacterial Genetics
- Vaccine Development
Background:
- Mycoplasma hyopneumoniae is a significant swine pathogen.
- The ribonucleotide reductase R2 subunit (NrdF) is a potential antigen for M. hyopneumoniae vaccines.
- Attenuated Salmonella typhimurium aroA CS332 is a candidate vector for oral vaccine delivery.
Purpose of the Study:
- To evaluate the immunogenicity of the Mycoplasma hyopneumoniae NrdF gene fragment.
- To assess the cell-mediated immune (CMI) response induced by oral vaccination with recombinant Salmonella strains.
- To investigate the influence of expression vectors on immune responses.
Main Methods:
- Cloning of the NrdF gene fragment into prokaryotic and eukaryotic expression vectors.
- Oral immunization of mice with attenuated Salmonella typhimurium aroA CS332 harboring recombinant plasmids.
- Analysis of serum and lung wash antibody responses (IgG, IgA).
- Assessment of cell-mediated immune response via IFN-gamma production from splenocytes.
Main Results:
- The NrdF gene is highly conserved among M. hyopneumoniae strains.
- Salmonella expressing NrdF from a prokaryotic vector failed to induce specific antibody or CMI responses.
- Salmonella expressing NrdF from a eukaryotic vector induced a significant NrdF-specific CMI response (IFN-gamma production) but not serum/secretory antibodies.
- The live vector Salmonella induced a serum IgG response but no mucosal IgA response.
Conclusions:
- Oral delivery of a DNA vaccine encoding M. hyopneumoniae antigen via live attenuated Salmonella can induce a cell-mediated immune response.
- The choice of expression vector influences the type of immune response elicited.
- Live bacterial vaccine carriers can impact the induced immune response profile.
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