The Glycoprotein and the Matrix Protein of Rabies Virus Affect Pathogenicity by Regulating Viral Replication and Facilitating Cell-to-Cell Spread

Abstract

While the glycoprotein (G) of rabies virus (RV) is known to play a predominant role in the pathogenesis of rabies, the function of the RV matrix protein (M) in RV pathogenicity is not completely clear. To further investigate the roles of these proteins in viral pathogenicity, we constructed chimeric recombinant viruses by exchanging the G and M genes of the attenuated SN strain with those of the highly pathogenic SB strain. Infection of mice with these chimeric viruses revealed a significant increase in the pathogenicity of the SN strain bearing the RV G from the pathogenic SB strain. Moreover, the pathogenicity was further increased when both G and M from SB were introduced into SN. Interestingly, the replacement of the G or M gene or both in SN by the corresponding genes of SB was associated with a significant decrease in the rate of viral replication and viral RNA synthesis. In addition, a chimeric SN virus bearing both the M and G genes from SB exhibited more efficient cell-to-cell spread than a chimeric SN virus in which only the G gene was replaced. Together, these data indicate that both G and M play an important role in RV pathogenesis by regulating virus replication and facilitating cell-to-cell spread.Rabies virus (RV), the etiological agent of one of the oldest recognized infectious diseases, almost always causes a fatal encephalomyelitis in several species of mammals, including humans (4). RV, the prototype of the Lyssavirus genus of the family Rhabdoviridae, is an enveloped, nonsegmented, negative-stranded RNA virus. RV has a simple genome of about 12 kb encoding five proteins: the nucleoprotein (N), the phosphoprotein (P), the matrix protein (M), the glycoprotein (G), and the RNA-dependent RNA polymerase (L). The viral RNA, which is always encapsidated by N, forms the ribonucleoprotein (RNP), which is the template for viral replication and transcription (2). The RNP together with P and L forms the viral replication complex, which is surrounded by the host cell-derived membrane that also contains G. M has been proposed to bridge the RNP and the cytoplasmic domain (CD) of RV G to form the bullet-shaped virion (22).The RV G, which is organized as a trimer, is the sole protein exposed on the surface of the virion. RV G interacts with cellular receptors (14,17,32,33), mediates pH-dependent fusion, and promotes viral entry from a peripheral site into the nervous system (19). Moreover, RV G is involved in the transsynaptic spread within the central nervous system (3, 7, 16). Although RV pathogenicity is a multigenic trait (10), RV G is the major contributor to the pathogenicity of a particular RV (5,6,10,15,21,23,29,30,34). The efficient interaction of RV G with putative host cellular receptors can promote effective virus uptake, resulting in increased virulence. Pathogenic RVs reportedly use different receptors and routes of entry than nonpathogenic derivatives (3,16). Differences in the distributions of various RV strains in the brain are determined at least in part by the RV G (35), and the RV G's of p...

Intergenotypic Replacement of Lyssavirus Matrix Proteins Demonstrates the Role of Lyssavirus M Proteins in Intracellular Virus Accumulation

“…One virus protein that has been identified as an important factor of pathogenicity in rabies virus infections is the RABV M protein (12,39). Whereas previous studies compared attenuated and nonattenuated genotype 1 RABV, in the present study the M proteins of lyssaviruses with different host tropisms were compared to assess the contribution of M to virus replication and virus-host interactions.…”

“…One viral protein that has been noticed as an important RABV pathogenicity determinant is the matrix protein M (12,39). M is essential for virus assembly and release (32) and is able to support virus budding even in the absence of G (31).…”

PPEY Motif within the Rabies Virus (RV) Matrix Protein Is Essential for Efficient Virion Release and RV Pathogenicity

“…Considering that M is important for the switch from transcription to replication, the inefficient release of virions from the cell most likely results in a difference in intracellular levels of viral proteins, which may contribute to the observed changes in RNA levels. Previously, similar changes were seen for RVs where a G and/or M protein from a heterologous RV strain with only modest sequence conservation was introduced; this resulted in decreased budding efficiency and changes in viral RNA synthesis (43). It would be interesting to analyze RNA production for the VSV PPPY mutants in a similar system to the one used here for RV.…”

Molecular Basis of Neurovirulence of Flury Rabies Virus Vaccine Strains: Importance of the Polymerase and the Glycoprotein R333Q Mutation

“…Recent evidence indicated that the RV polymerase complex also impacted virulence (58). The viral replication rate is controlled directly by the polymerase complex in tissue culture and has been shown to correlate inversely with the pathogenicity of RV (9,35,41). Analysis of the silver-haired bat-associated RV 18 (SHBRV-18) strain showed that the RV polymerase likely contributed to RV neuroinvasiveness (12).…”