Genetic variation in the HN and SH genes of mumps viruses: a comparison of strains from mumps cases with and without neurological symptoms

Abstract

Background: It is known that mumps virus (MuV) strains may vary in their neurovirulent capacity, and certain MuV strains may be highly neurotropic. In animal models and epidemiological studies, mutations at specific amino acids (aa) have been proposed to be associated with neurovirulence. To assess whether these genetic variations can be observed in clinical samples from patients and if they correlate with neurovirulence as determined by clinical symptoms, 39 mumps patients with or without neurological symptoms were investigated.

Principal findings: Respiratory samples, oral fluids, throat swabs, and neurological and cerebrospinal fluid samples were tested by RT-PCR and products sequenced. Sequences of the entire small hydrophobic (SH) gene and the partial hemagglutinin-neuraminidase (HN) gene were compared.

Conclusions: The results showed there was no significant difference between the samples of the two groups of patients at the aa sites in either the HN protein or the SH protein, which have previously been hypothesized to be associated with neurovirulence or antigenicity. The occurrence of neurological symptoms of mumps does not appear to be due to a single point mutation in either the HN or SH gene.

Figure 1. Alignment of the inferred partial aa sequences of the HN gene.

The potential glycosylation sites are shown in shadow and the potential neurovirulence sites are marked in boxes. Period (.) denotes identity with the uppermost sequence; (-) denotes areas that were not determined; (*) represents Genotype-strain ID.

Figure 2. Alignment of the inferred aa sequences of the SH gene.

The potential neurovirulence sites are marked in boxes. Period (.) denotes identity with the majority sequence; (-) denotes areas that were not determined; (*) represents Genotype-strain ID.