Novel Recombinant Food Safety Vaccines against Salmonella and ...

590V.A. Kuttappan et alelicited protection against S. Typhimurium in some treatment groups.Thus, novel food safety vaccines have the advantages of reducingcolonization of these pathogens in host tissues, harmless to host,compatible with other control measures, no food residues, and easy –cost effective way of administration.Keywords: Salmonella, campylobacter, food borne diseases,recombinant vaccines, poultry.1. IntroductionAccording to WHO, around 1.8 million people died in 2005 due to consumption ofcontaminated food and drinking water,and associatedfood borne illness (Newell et al.,2010). Salmonellosis and campylobacteriosis are two major food borne diseasesoccurring in many regions of the world and most common sources for these organismsare identified as poultry meat and eggs. Salmonella and Campylobacterare seen ingastrointestinal and/or reproductive tract of birds as commensal organisms whichcould contaminate meat or egg products leading to diseases in human beings. Like anyother bacteria, these organisms can also be controlled by adding antibiotics in poultrydiets. However, growing concerns over the use of antibiotics in food animals due to thepossibility of antibiotic residues and concerns about the development of antibioticresistant strains of pathogenic organisms have encouraged producers to seekalternative means of control. The main objective of this manuscript is to discuss aboutpotential use of novel vaccine strategies, based on the results from our laboratory, toimprove food safety in poultry industries.2. Strategies to Develop Effective Food Safety VaccinesVaccines are typically developed against antigenic regions or epitopes present ontarget organisms. When administered to host organism, the immune system of the hostwill recognize these epitopes, become activated and prevent or reduce the spread oftarget pathogenic organisms. However, developing vaccines becomes challengingwhen there exist multiple serovars of pathogenic organisms expressing individualepitopes that elicit little or no cross-protection against other serovars. For example,there are more than 200 serotypes of Salmonella, with different antigens, capable ofinfecting both domestic animals and human beings (Hargis et al., 2010; EFSA 2010).Firstly, an effective food safety vaccine should make use of highly conserved anduniversal epitopes on target organism resulting in broad spectrum protection againstvarious serovars.Secondly, food borne illness causing organisms like Salmonella andCamplyobacterare non-invasive and colonize poultry guts without causing anyapparent disease conditions. So, conventional vaccines administered parenterally or asinjection have little significance in controlling these organisms, as these vaccines will

592V.A. Kuttappan et alday old chicks, and 21d later followed by Campylobacter jejuni challenge. Among thevarious vaccine candidates tested, CjO113-vaccinated chicks had no C. jejunirecoveredfrom ileum samples, and had higher sIgAand serum IgGantibodies when compared toother groups (Layton et al., 2011). This observation was in accordance with the studyconducted by Godlewska et al. (2009) reporting an increased humoral response withCjO113 vaccination obtained from aSalmonella plasmid vector.Similarly, Bacillus subtilis(BS) is another vector used in our laboratory fordeveloping recombinant vaccines against both Salmonella and Campylobacter. Studieswere conducted by vaccinating chickens with Bacillus subtilis(PY79)-vectoredCjO113 vaccine co-expressing CD154in comparison to saline control and B. subtilisback bone. Two doses of vaccine (10 6 or 10 8 ) were tested with a primary vaccinationon 1d of age followed by two boosts at 10d and 21d of age.The birds were challengedwith C. jejuni(1.5 X 10 8 /bird) at 24d and ileal recovery was tested at different timepoints (Figure 1). Birds vaccinated with the BS-vectored CjO113 showed lower ilealrecovery of C. jejuni (Figure 1A) and higher serum IgG (Figure 1B) when compared tosaline control and BS backbone. In another study, a live BS vectored vaccineexpressing NNP (19 aminoacid synthetic peptide sequence) and HMGB1 was testedagainst saline control, BS backbone and NNP-conjugated with keyhole limpethemocyanin (KLH, Gen-Script Corp.) administered along with chitosan adjuvant toevaluate protection against SalmonellaTyphimurium. Birds were vaccinated on 1d(primary vaccination) and boosted on 10d followed by S. Typhimurium challenge(10 8 cfu/chick) on 14d of age. Blood samples were collected from these birds on 17dand 21d of age. The study showed that administration of both BS vectored vaccine andconjugated-NNP resulted in lower recovery of S. Typhimurium when compared tosaline control and BS backbone (Figure 2).Figure 1: Ileal recovery of Campylobacter jejuni(A) and Cj0113-specific serumIgG(Sample/positive ratio) levels (B)from chickens vaccinated with salinecontrol, Bacillus subtilis backbone (BSBB), Bacillus (Py79)-vectoredCjO113 co-expressing CD154 vaccines (10 6 or 10 8 ).

Novel Recombinant Food Safety Vaccines against Salmonella 593Figure 2: Recovery of S.Typhimurium from birds vaccinated with saline control, B.subtilis backbone (BS Py79), live B. subtilis NNP co-expressing HMGB1,and NNP-conugated with KLH administered with chitosan.4. ConclusionTwo major concerns regarding developing food safety vaccines against Salmonella andCampylobacter in poultry are the prevalence of a large number of serovars of theseorganisms, which limits the spectrum of protection from any conventional vaccinestrategies, and colonization in gastrointestinal tract of poultry without causing anydisease, thus mucosal immunity has to be given prime importance. Studies from ourlaboratory showed that Salmonella- or Bacillus- vectored vaccines expressing highlyconserved antigenic regions of food safety target organisms could enhance both themuscoal (sIgA) and humoral (serum IgG) immunity, resulting in reduced colonizationof these pathogenic organisms. In addition, vectored vaccines with co-expression ofimmune stimulatory molecules like CD154 and/or HMGB1 may be a valuabletechnique to fortify the immune response.References[1] AMiga, S Masters, M Gonzalez, and RJ Noelle (2000),The role of CD40–CD154 interactions in the regulation of cell mediated immunity. Immunol.Invest.29, 2, pp. 111–114.[2] B M Hargis, D J Caldwell and J A Byrd (2010), Microbial pathogens: Livepoultry considerations. In Poultry Meat Processing(Owens, CM, CZAlvarado, and AR Sams, Eds), CRC Press, Boca Raton, FL.

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Novel Recombinant Food Safety Vaccines against Salmonella 595[14] SL Layton, DR Kapzcynski, S Higgins, J Higgins, AD Wolfenden, KALiljebjelke, WG Bottje, D Swayne, LR Berghman, YM Kwon, B M Hargis,and K Cole (2009) Vaccination of chickens with recombinant Salmonellaexpressing M2e and CD154 epitopes increases protection and decreases viralshedding after low pathogenic avian influenza challenge. Poult. Sci.88, 11, pp.2244-2252.[15] SL Layton, MJ Morgan, K Cole, YM Kwon, DJ Donoghue, BM Hargis, and NR Pumford (2011), Evaluation of Salmonella-vectored Campylobacter peptideepitopes for reduction of Campylobacter jejuni in broiler chickens. ClinicalVaccine Immunol18, 3, pp. 449-454.[16] SShivaramaiah, JR Barta, SL Layton, C Lester, YM Kwon, LR Berghman,BM Hargis and G Tellez (2010), Development and evaluation of an aroA /htrASalmonella enteritidis vector expressing Eimeria maxima TRAP familyprotein EmTFP250 with CD 154 (CD 40L) as candidate vaccines againstCoccidiosis in broilers. Int. J PoultSci9, 11, pp. 1031-1037.[17] TA Barr, AL McCormick, J Carlring, and AW Heath (2003), A potentadjuvant effect of CD40 antibody attached to antigen. Immunology109,1, pp.87–92.[18] Y Xu, and G Song (2004),The role of CD40–CD154 interaction in cellimmunoregulation. J. Biomed. Sci.11, 4, pp. 426–438.

596V.A. Kuttappan et al