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Pathogenesis of fusion deficient recombinant mouse hepatitis viruses
L De Groot1, J D Piñón, J Phillips
1Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA.
Abstract:
In this study we have demonstrated that recombinant viruses carrying the amino acid mutations Q1067H, Q1094H, and L1114R were unable to induce fusion at neutral pH, replicated more efficiently in L2 cells, and that infection was delayed by ammonium chloride. These results suggest that the R120/R121 recombinants most likely use the endosomal pathway to enter cells. In this sense they are similar to the pH-dependent MHV-4 variant OBLV60. We were able to observe an attenuated virulence in vivo, despite the fact that our R120/R121 recombinants replicated to comparable (IC) or higher (IN) titers than the S4R29 recombinant in the brain. Preliminary results showed that the level of inflammation observed in infected mice is consistent with the attenuated virulence, but they cannot be explained by the high titers of replication.
Insights
Recombinant viruses with specific mutations show altered cell entry pathways and reduced virulence in vivo. These findings suggest a link between viral entry mechanisms and disease severity, impacting viral pathogenesis research.
Area of Science:
- Virology
- Molecular Biology
- Pathogenesis
Background:
- Understanding viral entry mechanisms is crucial for developing effective antiviral strategies.
- Specific mutations in viral proteins can significantly alter viral behavior and infectivity.
Purpose of the Study:
- To investigate the cell entry pathway and virulence of recombinant viruses with defined amino acid mutations.
- To correlate viral replication, entry mechanisms, and in vivo pathogenesis.
Main Methods:
- Generation of recombinant viruses with Q1067H, Q1094H, and L1114R mutations.
- Assessing viral fusion at neutral pH and replication in L2 cells.
- Evaluating infection delay by ammonium chloride treatment.
- Determining viral titers and virulence in vivo in a mouse model.
Main Results:
- Mutant viruses failed to induce fusion at neutral pH and showed delayed infection in the presence of ammonium chloride, indicating endosomal pathway entry.
- Recombinant viruses replicated efficiently in L2 cells and exhibited attenuated virulence in vivo.
- High viral titers in the brain did not fully explain the observed attenuated virulence or reduced inflammation.
Conclusions:
- The R120/R121 recombinants likely utilize the endosomal pathway for cell entry, similar to pH-dependent variants.
- Attenuated virulence in vivo is observed despite efficient viral replication, suggesting complex interactions between entry, replication, and host response.
- Further research is needed to elucidate the mechanisms underlying the reduced inflammation and attenuated virulence.