Examining the Affinity and Antigenic Changes of Foot-and-Mouth Disease Virus with Vaccinal Viruses in Khorasan Razavi Province from 2021 to 2022

Foot-and-mouth disease is one of the most important viral diseases affecting livestock. Types O, A, and Asia 1 of the foot-and-mouth virus have been endemic in Iran for a long time.

The current research investigated the molecular epidemiology, affinity, and changes in antigenicity of the foot-and-mouth virus in relation to vaccine viruses in Razavi Khorasan province from 2021 to 2022.

In this study, 51 samples taken from suspected animals exhibiting clinical symptoms between 2021 and 2022in the province were analyzed by ELISA, real-time RT-PCR and RT-PCR tests, and cell culture. The affinity of antigenicity of five circulating viruses with the vaccine virus (R-value) produced by the Razi Vaccine Research and Serum Institute was calculated.

The results showed that 34.52% of suspected samples were positive, with 33.33% belonging to sheep and 35.72% belonging to cattle; all samples were type O. By cell culture in 2021, seven samples from cows and two samples from sheep were isolated, while in 2022, five samples from cows and two samples from sheep were isolated. Determining the nucleotide sequence of five samples of the viruses showed that the virus O/IRN/KHO/1/2022 has the most similarity (98.5%) with the virus O/IRN/KHO/3/2022, whereas the virus O/IRN/KHO/7/2022 had the least similarity (90.7%) with the virus O/IRN/KHO/4/2022. Also, the similarity of the nucleic acids of all the isolated viruses with the virus used in the vaccine MN539142.1/O/IRN/93/2016 was more than 87.5% in all five cases, and the antigenic similarity coefficient of the circulating virus with the virus vaccine was greater than 0.3.

The vaccine from the Razi Vaccine Research and Serum Institute demonstrated the ability to produce protective antibodies and establish the necessary immunity against foot-and-mouth disease viruses circulating in Razavi Khorasan Province between 2021 and 2022.