Foot-and-mouth disease virus O1Lombardy is biochemically related to O2 isolates.

The capsid protein VP1-encoding RNA regions of the foot-and-mouth disease virus isolates O1Lombardy/1946 and O2Brescia/1947 were sequenced and found to be closely related to each other and to O2Normandy/1949, despite some sequence differences. The O1Lombardy sequence was expected to be more closely related to those of the subtype O1 isolates of 1965 and later (e.g., O1Kaufbeuren/1966), but this was not the case. The serological subtyping of both the Lombardy and the Kaufbeuren isolate as O1 strains was possibly due to identical VP1 C-terminal sequences, since all the subtype O2 isolates differ here from the O1 isolates at residue 209. Considerable dissimilarity of other O1Lombardy and O2Brescia genome parts to those of O1Kaufbeuren was qualitatively shown by analyzing the sizes of RNase-treated hybrids formed with virus RNA and defined subgenomic fragments of O1Kaufbeuren-specific antisense cRNA. These hybrids were fragmented into oligonucleotides, but others containing O1Kaufbeuren virus RNA were protected.