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Human rhinovirus mutants resistant to low pH
1Institute of Biochemistry, University of Vienna, Austria.
Abstract:
Mutants of human rhinovirus serotype 14 (HRV14) with increased resistance to treatment at low pH were obtained by repeated cycles of exposure to pH 4.5 and propagation in HeLa cells. Whereas wild-type virus lost more than 5 logs of infectivity upon incubation at pH 4.3, the three isolates examined were essentially unaffected. Conformational change of the viral capsid upon exposure to low pH was assessed as an increase of hydrophobicity by partition between an aqueous phase and a Triton X-114 phase; the mutants required exposure to a much lower pH to accumulate in the Triton phase than wild-type HRV14. The sequence of the capsid region was determined for three isolates; two isolates were found to have the changes Thr17 to lie in VP2 and Asn 100 to lie in VP1. The third isolate also had the change Thr17 to Ile in VP2; however, in VP1, Asp101 was replaced by Glu. Separate introduction of the mutations into full length cDNA clones of the wild-type sequence of HRV14 showed that only the changes in VP1 were necessary for the increased stability at pH 4.5. The implications of the mutations for the three-dimensional structure of the viral capsid are discussed.
Insights
Human rhinovirus 14 (HRV14) mutants show enhanced stability at low pH. Specific mutations in the VP1 protein significantly increase viral resistance to acid treatment, impacting capsid structure.
Area of Science:
- Virology
- Structural Biology
- Molecular Biology
Background:
- Human rhinovirus serotype 14 (HRV14) is a common human pathogen.
- Viral stability at low pH is crucial for infectivity and transmission.
- Understanding capsid protein mutations can reveal mechanisms of viral stability.
Purpose of the Study:
- To isolate and characterize HRV14 mutants with increased resistance to low pH.
- To identify the specific mutations responsible for enhanced acid stability.
- To investigate the structural implications of these mutations on the viral capsid.
Main Methods:
- Repeated exposure of wild-type HRV14 to low pH (4.5) and propagation in HeLa cells to generate resistant mutants.
- Assessing viral infectivity and conformational changes (hydrophobicity) at low pH.
- Determining the capsid protein sequences of resistant isolates.
- Introducing identified mutations into wild-type HRV14 cDNA clones to confirm their role in stability.
Main Results:
- Three HRV14 mutants resistant to low pH were isolated.
- Mutants retained infectivity at pH 4.3, unlike wild-type HRV14.
- Mutations identified in VP1 and VP2 capsid proteins.
- VP1 mutations alone were sufficient to confer increased stability at low pH.
- Mutations altered the pH threshold for viral capsid conformational changes.
Conclusions:
- Specific mutations in the VP1 capsid protein of HRV14 are critical for conferring resistance to low pH.
- These mutations likely stabilize the viral capsid structure, preventing conformational changes at acidic pH.
- The findings provide insights into the structural basis of HRV stability and potential targets for antiviral strategies.