Further Studies on the Soluble Form (Gs) of Rabies Virus Glycoprotein (G): Molecular Structure of Gs Protein and Possible Mechanism of the Shedding

Abstract

In this study, we investigated the antigenic structures and maturation of some C‐terminal‐deficient derivatives of rabies virus glycoprotein (G). The Gs protein, a soluble form of G protein shed from infected cells, displayed antigenicity to most of our conformational epitope‐specific anti‐G mAbs, but took the 1‐30‐44 epitope‐deficient conformation (termed GC form). (The 1‐30‐44 epitope was acid‐sensitive and dependent on two separate regions, the Lys‐202‐containing and Asn‐336‐containing regions; Kankanamge et al., Microbiol. Immunol., 47: 507–519). Intact G proteins took the 1‐30‐44 epitope‐positive form (referred to as GB form) on the cell surface, but not inside the cell. A deletion mutant G(1–429) (termed GATC), lacking the transmembrane (TM) and cytoplasmic domains, was shown to be accumulated in the rough endoplasmic reticulum (rER) with BiP and did not seem to be shed. Another C‐terminal‐deficient mutant G(1–462) (termed CT1) was deprived of the whole cytoplasmic domain except for a basic amino acid left at the C‐terminus, but was transported to the cell surface, where it showed pH‐dependent cell fusion activity and almost full antigenicity to most of the anti‐G mAbs with the exception of very weak antigenicity to mAb #1‐30‐44. No Gs protein could be detected in the CT1‐producing cultures. Based on these results, we think that the cytoplasmic domain was not necessary for the G protein to be transported to the cell surface, but was necessary to keep its 1‐30‐44 epitope‐positive GB conformation. Gs proteins might have lost the C‐terminal regions during the maturation process after being exported from the rER.

Household exposure and animal-bite surveillance following human rabies detection in Southern Ghana

“…Further investigation by the team revealed that symptoms were seen on 25th September, 2012. Humans can begin to shed rabies virus in saliva and tears 2 weeks before onset of symptoms [10]. The patient was therefore considered to be potentially infectious during September 11th - 29th, the period from 2 weeks before onset of symptoms until his death.…”

Investigation to determine staff exposure and describe animal bite surveillance after detection of a rabid zebra in a safari lodge in Kenya, 2011

“…The viral shedding period is known in dogs, cats, and ferrets, and is usually three to seven days before onset of clinical manifestations of rabies and throughout the course of the disease. Longer shedding periods of 10-14 days prior to the onset of symptoms have been observed with certain canine rabies virus variants in experimental infections, but these are the exception [ 8 ]. Viral excretion in other animals is highly variable, for example, in one study in bats viral shedding for 12 days before evidence of illness was documented[ 9 ].…”

The human alpha7 nicotinic acetylcholine receptor is a host target for the rabies virus glycoprotein

“…α7 and α4β2 nAChRs are expressed along axons, dendrites, and cell bodies, in addition to pre- and post-synaptic locations ( Zarei et al., 1999 ; Jones and Wonnacott, 2004 ; Zhong et al., 2008 ). A soluble form of RVG, which lacks the C-terminal anchoring region of the glycoprotein, has been detected in the media of rabies-infected cultured cells ( Morimoto et al., 1993 ; Thirapanmethee et al., 2005 ). As the hippocampal synaptic cleft (~20 nm ( Schikorski and Stevens, 1997 )) is too small to accommodate the rabies virion (60 x 180 nm ( Rupprecht, 1996 )), it is likely that soluble RVGs, if these are produced in vivo , target pre- and post-synaptic α7 nAChRs within the hippocampus ( Fabian-Fine et al., 2001b ).…”