Foot-and-Mouth Disease Virus Lacking the Leader Protein and Containing Two Negative DIVA Markers (FMDV A24 LL3B3D) Is Fully Attenuated in Pigs

Authors: ESCHBAUMER, MICHAEL - Friedrich-Loeffler-institut; DILL, VERONIKA - Friedrich-Loeffler-institut; CARLSON, JOLENE - Friedrich-Loeffler-institut; Arzt, Jonathan; STENFELDT, CAROLINA - University Of Kansas; KRUG, PETER - US Department Of Agriculture (USDA); HARDHAM, JOHN - Zoetis; STEGNER, JACOB - Zoetis; Rodriguez, Luis; Rieder, Aida - Elizabeth

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2020
Publication Date: 2/17/2020
Citation: Eschbaumer, M., Dill, V., Carlson, J.C., Arzt, J., Stenfeldt, C., Krug, P., Hardham, J., Stegner, J.E., Rodriguez, L.L., Rieder, A.E. 2020. Foot-and-Mouth Disease Virus Lacking the Leader Protein and Containing Two Negative DIVA Markers (FMDV A24 LL3B3D) Is Fully Attenuated in Pigs. Pathogens. https://doi.org/10.3390/pathogens9020129.
DOI: https://doi.org/10.3390/pathogens9020129

Interpretive Summary: Foot and mouth disease (FMD) is a devastating and highly contagious viral disease of livestock that continues to circulate in large areas of Asia and Africa posting a risk to FMD-free countries. Vaccines available since the early 1900s, are made by growing large amounts of virus in cell culture, inactivating it using chemicals, purifying the virus and formulating using appropriate dilutions buffers and adjuvants to improve the immunity. Currently, vaccine manufacturing involves the use of infectious virus and virus escapes from production facilities have caused outbreaks in FMD-free countries. This is one reason that US regulations do not allow vaccine production using live FMD virus. A novel vaccine platform, was discovered by ARS scientists using genetic engineering to remove one of the viral proteins (called leader) that is critical for causing disease and transmission in infected animals. Additionally, researchers introduced genetic markers that allow to differentiate infected from vaccinated animals, a feature critical during disease eradication efforts. This novel virus is an ideal platform for safe vaccine production since the virus, while still capable of growing in cell culture, does not cause disease in animals. The present study showed that this novel vaccine virus was safe and was incapable of producing disease or virus shedding in pigs, the most susceptible animal to FMD virus. These results allow further development of this promising technology aimed at achieving US domestic FMD vaccine production.

Technical Abstract: Inactivated whole-virus vaccines are widely used for the control of foot-and-mouth disease (FMD). Their production requires the growth of large quantities of virulent FMD virus in biocontainment facilities, which is expensive and carries the risk of an inadvertent release of virus. Attenuated recombinant viruses lacking the leader protease coding region have been proposed as a safer alternative for the production of inactivated FMD vaccines (Uddowla et al., 2012, J Virol 86:11675-85). In addition to the leader deletion, the marker vaccine virus FMDV A24 LL3BPVKV3DYR encodes amino acid substitutions in the viral proteins 3B and 3D that allow the differentiation of infected from vaccinated animals and has been previously shown to be effective in cattle and pigs. In the present study, two groups of six pigs each were inoculated with live FMDV A24 LL3BPVKV3DYR virus either intradermally into the heel bulb (IDHB) or by intra-oropharyngeal (IOP) deposition. The animals were observed for 3 or 5 days after inoculation, respectively. Serum, oral and nasal swabs were collected daily and a thorough postmortem examination with tissue collection was performed at the end of the experiment. None of the animals had any signs of disease or virus shedding. Virus was reisolated from only one serum sample (IDHB group, sample taken on day 1) and one piece of heel bulb skin from the inoculation site of another animal (IDHB group, necropsy on day 3), confirming that FMDV A24 LL3BPVKV3DYR is highly attenuated in pigs.