Related Experiment Videos
Molecular differences between wild-type Japanese encephalitis virus strains of high and low mouse neuroinvasiveness
1Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0605, USA.
Abstract:
Japanese encephalitis (JE) virus strain P3 was highly neurovirulent and neuroinvasive in weanling mice whereas two other JE virus strains, SA14/USA and S892, were only neurovirulent. Infectivity titrations of brains and sera showed that P3 virus multiplied faster and reached a higher infectivity titre than S892 virus following inoculation of viruses by the intraperitoneal (i.p.) route. The p.f.u./LD50 was 10(1.7) and 10(6.2) for P3 and S892 viruses respectively, following i.p. inoculation, while JE virus strain SA14/USA did not kill mice when inoculated by this route (i.e. > or = 10(6.3) p.f.u./LD50). Nevertheless, the genomic similarity between P3 virus and strains SA 14/USA and S892 was more than 97.8 percent at the nucleotide level and 99 percent at the amino acid level. Compared with S892 and SA14/USA viruses, P3 virus had 33 and 21 amino acid differences, respectively. The structural protein genes of P3 virus were more divergent than non-structural protein genes. Nine unique amino acids were found in the envelope protein gene. None of these amino acid differences were shared with other wild-type JE virus strains. Although we cannot identify the precise molecular determinants of virulence of JE virus, there were no unique amino acids in M, NS1, NS2A, NS3, NS4A and NS4B proteins of P3 virus compared with other wild-type viruses. Therefore, it appears that these proteins make no significant contribution to the high neuroinvasiveness of P3 virus. The structural proteins, and non-structural proteins NS2B and NS5 may be involved in increasing neurovirulence and neuroinvasiveness of P3 virus. P3 virus differed by several nucleotides in the 3' non-coding region while no nucleotide difference was found in the 5' non-coding region.
Insights
Japanese encephalitis (JE) virus strain P3 shows high neurovirulence and neuroinvasiveness in mice. Genetic analysis reveals unique amino acid differences in structural proteins, potentially explaining P3
Area of Science:
- Virology
- Molecular Biology
- Neuroscience
Background:
- Japanese encephalitis (JE) virus causes significant neurological disease.
- Understanding the genetic basis of JE virus virulence is crucial for developing effective countermeasures.
- Previous studies have identified varying degrees of neurovirulence among JE virus strains.
Purpose of the Study:
- To investigate the molecular determinants of neurovirulence and neuroinvasiveness in a highly virulent JE virus strain (P3).
- To compare the genetic makeup of JE virus strain P3 with less virulent strains (SA14/USA and S892).
- To identify specific viral proteins or genetic regions associated with enhanced pathogenicity.
Main Methods:
- Inoculation of weanling mice with different JE virus strains (P3, SA14/USA, S892) via the intraperitoneal route.
- Infectivity titrations of brains and sera to assess viral replication and dissemination.
- Genomic sequencing and comparative analysis of nucleotide and amino acid sequences, focusing on structural and non-structural proteins, and non-coding regions.
Main Results:
- JE virus strain P3 demonstrated significantly higher neurovirulence and neuroinvasiveness compared to SA14/USA and S892 strains in mice.
- P3 virus exhibited faster multiplication and higher infectivity titers in vivo.
- Despite high genomic similarity (>97.8% nucleotide, >99% amino acid), P3 had distinct amino acid differences, particularly in structural protein genes, including nine unique amino acids in the envelope protein.
Conclusions:
- The high neuroinvasiveness of JE virus strain P3 is not attributable to unique amino acids in M, NS1, NS2A, NS3, NS4A, and NS4B proteins.
- Structural proteins, along with non-structural proteins NS2B and NS5, are potential contributors to the increased neurovirulence and neuroinvasiveness of P3 virus.
- Differences in the 3' non-coding region may also play a role in the distinct pathogenic profile of P3 virus.