Changes in Mumps Virus Gene Sequence Associated with Variability in Neurovirulent Phenotype

Abstract

Mumps virus is highly neurotropic and, prior to widespread vaccination programs, was the major cause of viral meningitis in the United States. Nonetheless, the genetic basis of mumps virus neurotropism and neurovirulence was until recently not understood, largely due to the lack of an animal model. Here, nonneurovirulent (Jeryl Lynn vaccine) and highly neurovirulent (88-1961 wild type) mumps virus strains were passaged in human neural cells or in chicken fibroblast cells with the goal of neuroadapting or neuroattenuating the viruses, respectively. When tested in our rat neurovirulence assay against the respective parental strains, a Jeryl Lynn virus variant with an enhanced propensity for replication (neurotropism) and damage (neurovirulence) in the brain and an 88-1961 wild-type virus variant with decreased neurotropic and neurovirulent properties were recovered. To determine the molecular basis for the observed differences in neurovirulence and neuroattenuation, the complete genomes of the parental strains and their variants were fully sequenced. A comparison at the nucleotide level associated three amino acid changes with enhanced neurovirulence of the neuroadapted vaccine strain: one each in the nucleoprotein, matrix protein, and polymerase and three amino acid changes with reduced neurovirulence of the neuroattenuated wild-type strain: one each in the fusion protein, hemagglutinin-neuraminidase protein, and polymerase. The potential role of these amino acid changes in neurotropism, neurovirulence, and neuroattenuation is discussed.Mumps virus is a 15.3-kb enveloped, nonsegmented, negative-strand RNA virus in the Paramyxoviridae family. The mumps virus genome organization is 3Ј NP-P-M-F-SH-HN-L 5Ј, in which the abbreviations represent the genes encoding the following proteins: NP, nucleoprotein; P, phosphoprotein; M, matrix protein; F, fusion protein; SH, small hydrophobic protein; HN, hemagglutinin-neuraminidase protein; and L, polymerase (16). The virus causes mumps, an acute communicable viral disease typical of childhood. Mumps virus is transmitted through oropharyngeal secretions, with primary virus replication in the respiratory mucosa. Following the development of viremia, mumps virus infects a number of targets, including the central nervous system (CNS), and was a common cause of viral meningitis in the prevaccine era (6). The most common neurological manifestation of CNS infection is aseptic meningitis (23, 37). More rarely, clinical manifestations involve encephalitis (31, 38), cerebellar ataxia (12), and transverse myelitis and poliomyelitis-like disease (29,33). While symptoms are typically transient, CNS infection can produce significant morbidity (in such manifestations as, e.g., deafness [20,36,57]) and mortality, particularly in the case of encephalitis (38). Despite the clinical significance of mumps virus and the widespread international use of a number of mumps virus vaccines, little is known about the genetic basis for mumps virus attenuation or virulence.In this study, we sought to iden...

Genetic Variation in the HN and SH Genes of Mumps Viruses: A Comparison of Strains from Mumps Cases with and without Neurological Symptoms

“…In the HN protein of the Kilham strain (GB. AY502062), histidine and serine were found at aa354 and 356, which might be associated with mumps neurovirulence [20]. Such changes, however, were not found in any strain investigated in this study (Figure 1), except for proline and glutamic acid, which were at aa354 and 356, respectively, of some historic strains, which belonged to genotype A (Figure 1).…”

“…Strain 88-1961, a wild-type strain isolated from a patient with neurological symptoms, caused severe, devastating neurological damage (e.g., hydrocephalus) in the rat neurovirulence assay [12]. The serine→asparagine substitution at aa466 in the HN of strain 88-1961 (Table 1), which is predicted to result in a loss of N glycosylation site (aa464 to aa466) had the potential to affect virus tropism and virulence, and was associated with an aa change in the L protein with MuV neuroattenuation [20], [36], [37]. However, in the present study, the above-mentioned substitutions in the HN gene were not found in the 39 sequences generated in the P and N groups.…”

“…Variations in amino acid (aa) at locations of the HN protein (aa335, 354, 356, 360, 464, and 466) and SH protein, (aa29 and aa48) were proved to be associated with MuV neurovirulence [13], [14], [15], [16], [17], [18], [19], [20], [21], and the related information is summarized in Table 1. The HN protein is also the major immunogenic protein [22], and the N-linked glycosylation sites (N-X-T or N-X-S) play important roles in maintaining the structure and antigenic properties of the extracellular domain [23].…”

Three cases of mumps virus and enterovirus coinfection in children with enteroviral meningitis

“…Previous studies have indicated that amino acid substitutions at positions 335, 354, 356, 360, 464, and 466 in the HN region, and in positions 29 and 48 in the SH region, resulted in neuro-virulence of the virus. [19,42,43] The HN region is the main immunogenic part of the mumps genome and contains glycosylation sites in 3 epitope domains (aa265-288, aa329-340, aa352-360). [19] The SH region is the most variable part of the genome and is used for genotyping as well as for phylogenetic analysis of the virus.…”

Techniques Employed in Production of Traditional Vaccines Commonly Used by Military Forces: A Review

“…The controversial Urabe strain for mumps, whose use stopped as a vaccinating strain because of developing meningitis and encephalitis (19), was produced by attenuating the pathogen in chick fibroblast (5,20). This is while the Jeryl Lynn strain of mumps is produced owing to this concept by inoculating it into specific pathogen free (SPF) chicken embryonic fibroblasts (21) and cell cultures of chick embryo (20,22).…”