The capsid protein of vesicular exanthema of swine virus serotype A48: relationship to the capsid protein of other animal caliciviruses

Vesicular exanthema of swine virus (VESV), the prototype calicivirus, is the etiologic agent of the porcine disease vesicular exanthema of swine (VES). VES is characterized by vesicle formation on the extremities, mouth and snout and causes abortions and stillbirths if infection occurs during pregnancy. VESV is considered an exotic agent in the US, following its eradication in 1956. The single capsid protein gene of VESV serotype A48 was cloned and sequenced. The capsid amino acid sequence was 69% similar to the San Miguel sea lion virus serotype 1 (SMSV 1) and 89% similar to the SMSV serotype 4 (SMSV 4) capsid proteins. The six functional regions (A-F) previously identified in SMSV 1, SMSV 4, feline calicivirus and rabbit hemorrhagic disease virus capsid proteins were present in VESV A48. Two sets of PCR primers were designed which directed amplification of the 5' end (A region) and the hypervariable (E region) sequences of the capsid protein precursor gene of these viruses, as well as seven additional SMSV serotypes. Alignment and phylogenetic analysis of the N-terminal sequences demonstrated the close relationship of these viruses. Alignment of the hypervariable region amino acid sequences of the ten viruses confirmed that a great variety of sequence exists in this region; however, a consensus sequence (NxT(N/H)F(K/R)GxYI(C/M)GxLx(T/R)) was derived which is also present in the feline calicivirus capsid protein. Comparison of the E region sequences provides further evidence that this area of animal calicivirus capsid protein may contain the major antigenic determinants.