Poster Presentation 14th Lorne Infection and Immunity 2024

Inhibition of interferon induction by P protein isoforms of rabies virus fixed and street strains (#120)

Kazuma Okada 1 2 , Junki Hirano 1 2 , Kentaro Uemura 1 2 , Chikako Ono 1 2 , Shuhei Taguwa 1 2 3 , Yoshiharu Matsuura 1 2
  1. Laboratory of Virus Control, Center for Infectious Disease Education and Research (CiDER), Osaka University, Suita, Osaka, Japan
  2. Research Institute for Microbial Diseases (RIMD), Osaka University, Suita, Osaka, Japan
  3. Center for Advanced Modalities and DDS (CAMaD), Osaka University, Suita, Osaka, Japan

The P gene of rabies virus (RABV), which plays a crucial role in immune evasion, encodes five proteins known as P protein isoforms (P1-5). These isoforms are essential for suppressing interferon (IFN) induction in muscle cells and contribute to neuroinvasiveness, the ability of the virus to invade the nervous system from peripheral tissues. However, previous studies in which the role of P2-5 as IFN antagonists was investigated were conducted using only the laboratory RABV (fixed) strain. While the wild RABV (street) strain typically exhibits original neuroinvasiveness, the function of P2-5 of the street strain in inhibiting IFN induction has not yet been studied. Therefore, in this study, we investigated the inhibitory activities of P1-5 on IFN induction using the myoblast cell line C2C12 by expressing the P proteins of both the fixed strain CVS and the street strain 5989. Cells were transfected with pIFNb-luc, which expresses firefly luciferase under the control of the IFN-β promoter, and with pRL-SV40, a control reporter vector expressing Renilla luciferase, along with each P1-5 expression vector from CVS and 5989 strains. At 24 hours after transfection, cells were stimulated by transfecting Poly(I:C) LMW, which is a dsRNA analog ranging from 0.2 kb to 1 kb, and Poly(I:C) HMW ranging from 1.5 kb to 8 kb. After 24 hours of incubation with Poly(I:C), the cells were subjected to dual luciferase assays. Cells expressing CVS-P1, P2 and 5989-P1 to P5 stimulated with Poly(I:C) LMW showed significantly lower IFN-β promoter activities than did cells transfected with an empty plasmid (control cells), but there was no significant difference between the control cells and cells expressing CVS-P3 to P5. In contrast, cells expressing 5989-P1 to P5, but not CVS-P1 to P5, stimulated with Poly(I:C) HMW showed significantly lower IFN-β promoter activities than did the control cells. These findings suggest that P2-5 of the street strain, unlike the fixed strain, retain a robust ability to inhibit IFN induction stimulated by both short and long dsRNAs.