Abstract
Here, we engineered two FMD viruses with histidine residues inserted into or fused to the FMDV capsid. Both 6xHis viruses exhibited growth kinetics, plaque morphologies and antigenic characteristics similar to wild-type virus. The 6xHis tag allowed one-step purification of the mutant virions by Co2+ affinity columns. Electron microscopy and biochemical assays showed that the 6xHis FMDVs readily assembled into antigen: adjuvant complexes in solution, by conjugating with Ni2+-chelated nanolipoprotein and monophosphoryl lipid A adjuvant (MPLA:NiNLP). Animals Immunized with the inactivated 6xHis-FMDV:MPLA:NiNLP vaccine acquired enhanced protective immunity against FMDV challenge compared to virions alone. Induction of anti-6xHis and anti-FMDV neutralizing antibodies in the immunized animals could be exploited in the differentiation of vaccinated from infected animals needed for the improvement of FMD control measures. The novel marker vaccine/nanolipid technology described here has broad applications for the development of distinctive and effective immune responses to other pathogens of importance.
•6xHis-tags in A24 FMDV enable purification and biding to adjuvants via metal ions.•6xHis A24 FMDV:MPLA:NiNLP vaccine enhanced protective immunity against FMDV.•Surface exposed capsid tags allow distinction of infected from vaccinated animals.