Epitope selection and their placement for increased virus neutralization in a novel vaccination strategy for porcine epidemic diarrhea virus utilizing the Hepatitis B virus core antigen

Abstract

Porcine epidemic diarrhea virus (PEDV) is a member of the Alphacoronaviridae genus within the Coronaviridae family. It is the causative agent of porcine epidemic diarrhea, a disease that can have mortality rates as high as 100% in suckling piglets. PEDV causes severe economic loss, and has been in existence for decades. A panzootic starting in 2010 renewed interest in the development of a universal vaccine toward PEDV. This report details several design changes made to a Hepatitis B virus core antigen (HBcAg)-based recombinant vaccine strategy, and their effect in vivo. Initially, several multi-antigen vaccine candidates were able to elicit antibodies specific to three out of four B-cell epitopes inserted into the chimeric proteins. However, a lack of virus neutralization led to a redesign of the vaccines. The focus of the newly redesigned vaccines was to elicit a strong immune response to the YSNIGVCK amino acid motif from PEDV. Genetically modified new vaccine candidates were able to elicit a strong antibody (Ab) response to the YSNIGVCK epitope, which correlated with an increased ability to neutralize the CO strain of PEDV. Additionally, the location of the inserted PEDV epitopes within the vector protein was shown to affect the immune recognition toward the native HBcAg during vaccination.

Ensembles of Hydrophobicity Scales as Potent Classifiers for Chimeric Virus-Like Particle Solubility – An Amino Acid Sequence-Based Machine Learning Approach

“…The foreign peptide is typically introduced genetically into the VLP at the N-terminus, C-terminus, or preferably in the major immunodominant region (MIR) (Karpenko et al, 2000;Pumpens and Grens, 2001). However, insertion of a foreign epitope often results in insoluble, misassembled or aggregated capsids, lacking the desired immunogenicity (Karpenko et al, 2000;Billaud et al, 2005;Gillam and Zhang, 2018). The process of identifying soluble cVLP constructs is highly empirical and time-consuming (Chackerian, 2007).…”

Designs of Antigen Structure and Composition for Improved Protein-Based Vaccine Efficacy

“…More interesting, however, is the positive effect that increasing hapten density has had on the occurrence of CIES, presumably through the crowding of carrier-specific BCR epitopes (138). Interruption, removal, or blocking of AIRs in chimeric VLP formulations via recombinant and/or chemical means has been shown to improve immunogenicity toward target epitopes and minimize immunogenicity toward carrier protein, further corroborating this presumption (122,139,140). However, chemical modification, such as PEGylation, is largely non-specific, thus resulting in unpredictable outcomes for vaccines.…”

“…If epitope insertions can be made within AIRs without negatively influencing protein folding, it ultimately results in B cell responses being redirected away from the previous AIR and toward the introduced epitope. This concept was demonstrated by Gillam et al when they reported increased antibody titers to recombinantly inserted YSNIGVCK epitope and decreased titers to hepatitis B core antigen (HBcAg) VLP when evaluating a porcine epidemic diarrhea PBV in mice (122). A maximal insert size exists for all AIRs in which proper protein folding can still be accommodated.…”

“…The majority of CP in APCs is due to antigen stability and slowed lysosomal digestion, though other factors, such as the vacuolar pathway, cell maturation stage, and immunostimulatory environment, do play a role (170)(171)(172)(173)(174)(175)(176)(177). PBVs can be engineered to improve stability, as has been demonstrated by the introduction of inter-capsomeric disulfide bonds within HBcAg VLPs and MS2 bacteriophage VLPs (122,(178)(179)(180). The effect that this engineered stability has on MHC pathway, however, has not been thoroughly investigated, though it appears that stabilization of antigen promotes CP and the activation of T C cells as destabilization has been shown to reduce cross-presentation efficiency (181).…”

Epitope-based vaccine as a universal vaccination strategy against Toxoplasma gondii infection: A mini-review

“…LGPVKLSAEGPT, TAAKTHTVRGFKV, SYFAADRLVP SAG1, GRA2, GRA7 [41] KLFETTDMY, VRQEAIARALARAAA Anopheles mosquito salivary proteins [70] GNIEGQWALKNHSLVSLSEQVLVSCDNIDD CPA (Cysteine peptidase A) [59] YSNIGVCK [71] QTLIAIHTLAIRYAN Paracoccidioides brasiliensis gp43 antigen [72] RPPIFIRRL, sSVRDRLARL EBNA3 [19] Residues 137-160 and 197-211 VP1 gene of foot-and-mouth disease virus [73] (TAKDGMEYYNKMGELYKQ, (RCLLGFKEVGGKCVPASI) Plasmodium knowlesi merozoite surface protein-142 [7] TCPDKKSTA SAG1 (59-67) [9] KSFKDILPK, STFWPCLLR, AVVSLLRLLK, SSAYVFSVK, AMLTAFFLR) SAG1, SAG2, GRA5, SRS52A, GRA6 [17] appropriate adjuvants that can be used along with epitope-based vaccination strategies and establishing optimal immunization protocols along with evaluation criteria.…”