Characterization of three co-circulating genotypes of the small hydrophobic protein gene of mumps virus.

Eighteen virus isolates and 22 serum samples collected between 1971 and 1997 from patients with mumps were genotyped by PCR with specific primer pairs for the A, C and D genotypes of the small hydrophobic (SH) protein gene. All serum samples were subjected to nucleotide sequence analysis of the gene, and the deduced 57-amino-acid sequences were aligned with previously published sequences from the USA, Canada, Portugal, the UK, France, Germany, Switzerland, Denmark, Sweden, Russia, China and Japan. The existence of six genotypes of the SH protein gene, named A to F, was confirmed. In the Stockholm area, co-circulation of genotypes A, C and D at different times was found. There was a striking difference in genotype between the virus isolates and the serum samples. The 18 virus isolates represented genotypes C and D, whereas the 22 serum samples contained genotype A. In most cases, the amino acid sequences of the 22 genotype A specimens were identical to the previously described SBL-1 strain of genotype A. Genotypes C and D were always associated with meningitis, and in some cases parotitis, whereas infection with genotype A most often resulted in parotitis and seldom in meningitis.