Characterization of encephalomyocarditis virus isolated from aborted swine fetuses

SUMMARY Characteristics of 2 encephalomyocarditis virus (emcv) isolates (MN-25 and MN-30) recovered from aborted swine fetuses were examined along with 2 other swine isolates (NVSL-MDV and NVSL-PR) and a reference ATCC strain (VR-129). All 5 emcv isolates were found to be serologically related by cross testing, using serum neutralization and fluorescent antibody assays. Hemagglutination (ha) properties of the 5 isolates were compared, using 5 diluents. The MN-25 and NVSL-MDV strains had ha activity with guinea pig rbc in all 5 diluents, whereas MN-30, NVSL-PR, and VR-129 had ha activity only in KCl-borate buffer. The ha ability with rbc of various animal species was examined, using KCl-borate diluent. All virus isolates had high ha titer (1:512 to 1:2,048) with guinea pig, rat, and horse rbc and lower ha titer (1:16 to 1:64) with sheep rbc. The MN-25 and NVSL-MDV isolates agglutinated dog rbc, whereas MN-30, NVSL-PR, and VR-129 strains did not. Viral replication was evident in 8 of 10 cell lines tested, although infectivity titers of each virus varied by cell line used. Plaque-forming ability was similar for all 5 isolates, but plaque size was different by virus and cell culture used. Virus isolates were found to be stable after being heated at 56 C and subjected to a wide range of pH. A viral polypeptide pattern difference for all 5 isolates was not found by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was concluded that MN-25 and MN-30 are serologically related and have similar viral characteristics as those of previous emcv isolates and the reference ATCC strain, although differences in ha ability could be observed.