Study On Variation Of 3A Gene From The O/GS/WW/92 Strain Of Swine Foot-and-Mouth Disease Virus Propagated Successionally In Different Host Cells And Animals

FMDV derived from different host animals, its 3A protein is different. Compared with bovine FMDV, swine FMDV nonstructural protein 3A was altered 10 amino acids in 93-102 sites. In this Lab, it was find that O/GS/WW/92 strain3A altered 4 amino acids in amino acids sequence 93-102 sites, meanwhile the virus has apparent tendentiousness in tropism to swine and bovine. It reported that the origin of porcine FMDV was from OMII vaccine strain. However, this result was just from the analysis of VP1 nucleotide sequences, there is no experiment model about 3 A to support this theory directly.Analyzing the homogeneity between O/GS/WW/92 and OMII, we find they have a close genetics relationship and the homogeneity of VP1 and 3A are 97.7% and 98.9% respectively, the protein 3 A of O/GS/WW/92 strain successionally deleted 4 amino acids in 93-102 sites. So we conjecture it is possible that the O/GS/WW/92 derived from OMII. Therefore, we selected O/GS/WW/92 as the sample, passaged in different host cells and animal, to preview the genetic relation between O/GS/WW/92 and OMII under the Lab condition.The results showed that: 1) O/GS/WW/92 were passaged by different hosts (passaged 110 generations in BHK-21 cell, 65 generations in PK-15 cell, 9 generations in swine), 3A protein didn't alter similarity to naturally.2) O/GS/WW/92 grew well in BHK-21 and PK-15 cells, but replicated poorly in MD-BK cell. 3) With the increase of passaged generations, LD₅0 and TCID50 also rise.4) Nucleotide sequence of VP1 gene take place a series of substitution.Thus it can be seen, FMDV altered 4 amino acids were addicted strongly to swine, but were attenuated to bovine, O/GS/WW/92 was likely to an transition strain from bovine virus to swine virus, FMDV major immunological gene VP1 mutated randomly and no-directionally, but generally this mutation will keep stabilization to antigenicity.