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A replication-defective variant of Sabin 3 poliovirus
1Microbiology Program, Pennsylvania State University, University Park 16802.
Abstract:
A variant of Sabin type 3 poliovirus, 265B, only produces 2-3% of the yields of control virus and has a protracted growth cycle in HeLa cells. Attachment and penetration do not appear to account for defective growth of 265B. Viral protein and RNA syntheses are reduced, and blockage of cell protein synthesis is delayed considerably as compared with the parent virus. Nucleotide sequence analysis failed to detect mutations in protein 2AProt or changes in the 5'-noncoding region that could account for growth properties of the virus. However, a Thr-to-Ala substitution was found in viral peptide 2B of 265B, and this alteration is probably responsible for the replication defect.
Insights
A Sabin type 3 poliovirus variant, 265B, shows significantly reduced yields and a delayed growth cycle. A specific mutation in viral peptide 2B is identified as the likely cause of this replication defect.
Area of Science:
- Virology
- Molecular Biology
- Cellular Biology
Background:
- Sabin type 3 poliovirus is a live-attenuated vaccine strain.
- Viral replication efficiency is crucial for vaccine efficacy and safety.
- Understanding poliovirus variants with altered growth properties is important for virological research.
Purpose of the Study:
- To investigate the reasons behind the defective growth of a Sabin type 3 poliovirus variant, designated 265B.
- To identify the genetic alterations responsible for the reduced viral yield and prolonged growth cycle of 265B in HeLa cells.
Main Methods:
- Comparative analysis of viral replication in HeLa cells.
- Assessment of viral attachment, penetration, protein synthesis, and RNA synthesis.
- Nucleotide sequence analysis of the viral genome, focusing on key proteins and non-coding regions.
Main Results:
- The 265B variant exhibited significantly lower viral yields (2-3% of control) and a protracted growth cycle.
- Defective growth was not attributed to attachment or penetration issues.
- Reduced viral protein and RNA synthesis, along with delayed host cell protein synthesis blockage, were observed.
- No mutations were found in protein 2AProt or the 5'-noncoding region.
- A threonine-to-alanine substitution in viral peptide 2B was identified in the 265B variant.
Conclusions:
- The identified Thr-to-Ala substitution in viral peptide 2B is the probable cause of the observed replication defect in the 265B poliovirus variant.
- This specific mutation impacts viral replication efficiency, leading to reduced yields and altered growth kinetics.