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Sindbis virus mutations which coordinately affect glycoprotein processing, penetration, and virulence in mice
D L Russell1, J M Dalrymple, R E Johnston
1Department of Microbiology, North Carolina State University, Raleigh 27695-7615.
Abstract:
Rapid penetration of baby hamster kidney cells was used as a selective pressure for the isolation of pathogenesis mutants of the S.A.AR86 strain of Sindbis virus. Unlike most Sindbis virus strains, S.A.AR86 is virulent in adult as well as neonatal mice. Two classes of mutants were defined. One class was attenuated in adult mice inoculated intracerebrally as well as in neonatal mice inoculated either intracerebrally or subcutaneously. Sequence analysis of the glycoprotein genes of the parent virus and three such mutant strains revealed a single point mutation which resulted in an amino acid change at position 1 in the E2 glycoprotein. The change from a serine in S.A.AR86 to an asparagine in the mutants created a new site for N-linked glycosylation which appeared to be utilized. This mutation did not retard release of infectious particles; however, mutant virions contained the E2 precursor protein (PE2) rather than the E2 glycoprotein itself. The mutants also lost the ability to bind two E2-specific monoclonal antibodies, R6 and R13. A second class of mutants was attenuated in neonatal mice upon subcutaneous inoculation but remained virulent in adults and in neonates when inoculated intracerebrally. Sequence analysis of three such strains revealed the substitution of an arginine residue for a serine at position 114 in the E2 glycoprotein. Reactivity with monoclonal antibodies R6 and R13 was reduced, yet members of this mutant class were more susceptible than S.A.AR86 to neutralization by these antibodies.
Insights
Researchers identified Sindbis virus mutants with altered virulence. A mutation in the E2 glycoprotein affected viral pathogenesis and antibody neutralization, offering insights into Sindbis virus disease.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Sindbis virus (SINV) causes various diseases in humans and animals.
- The S.A.AR86 strain of SINV is virulent in both adult and neonatal mice.
- Understanding viral pathogenesis is crucial for developing effective treatments and vaccines.
Purpose of the Study:
- To isolate and characterize Sindbis virus mutants with altered virulence.
- To investigate the genetic basis of Sindbis virus pathogenesis.
- To identify specific viral proteins involved in virulence and host immune response.
Main Methods:
- Isolation of Sindbis virus mutants using baby hamster kidney cell penetration as a selective pressure.
- Virulence assays in adult and neonatal mice via intracerebral and subcutaneous inoculation.
- Sequence analysis of glycoprotein genes (E1, E2) to identify mutations.
- Assessment of viral particle release and E2 precursor protein (PE2) presence.
- Monoclonal antibody binding assays (R6, R13) and neutralization studies.
Main Results:
- Two classes of Sindbis virus mutants with distinct virulence phenotypes were identified.
- Class I mutants, with a serine-to-asparagine change at E2 glycoprotein position 1, exhibited attenuated virulence in both adult and neonatal mice.
- This mutation created a novel N-linked glycosylation site, altered virion composition (PE2 instead of E2), and abolished binding to specific monoclonal antibodies.
- Class II mutants, with an arginine-for-serine substitution at E2 glycoprotein position 114, showed reduced virulence in neonates (subcutaneous) but retained virulence in adults and neonates (intracerebral).
- Class II mutants had reduced reactivity with monoclonal antibodies R6 and R13 and were more susceptible to neutralization by these antibodies.
Conclusions:
- Mutations in the Sindbis virus E2 glycoprotein significantly impact viral virulence and host-specific pathogenesis.
- Alterations in E2 glycosylation and structure affect viral interactions with host immune factors, including monoclonal antibodies.
- The study provides valuable insights into the molecular mechanisms underlying Sindbis virus virulence and potential targets for therapeutic intervention.