No abstract

Strains of the murine coronavirus mouse hepatitis virus type 4 (MHV-4) which contained a mutation in the E2 peplomer glycoprotein were obtained by selection for resistance to neutralization by monoclonal antibodies. Characterization of six variants representing two independent epitopes on E2, E2B and E2C, by in vitro neutralization and antibody-binding assays demonstrated that selection for an alteration in epitope E2B also resulted in changes in epitope E2C and vice versa. We observed a mutation frequency of approximately 10-4.3 to 10-4.6, which is consistent with the expected occurrence of single point mutations. The variant virus strains were attenuated with respect to neurovirulence when compared with wild-type MHV-4. Mice normally develop encephalomyelitis and die after wild-type MHV-4 infection. Mice receiving 2to 3-log-higher doses of the variant strains survived and developed demyelinating disease. As the disease progressed, evidence of remyelination and ongoing demyelination was observed up to 65 days after infection. Virus reisolated 15 days after infection retained the variant phenotype. The data indicate that the E2 glycoprotein plays a central role in determining the cellular tropism and virulence of MHV-4 in the mouse.

SUMMARYThe genes of herpes simplex virus type 1 (HSV-1) can be divided into at least three temporally regulated groups termed immediate early (IE), early and late. We have Studied in detail the expression of a member of the late class of genes, US11, which encodes a polypeptide of apparent molecular weight 21K. Highly specific and sensitive probes were used to monitor US1 t RNA and protein synthesis during HSV-1 infection of tissue culture cells in the presence and absence of phosphonoacetic acid, an inhibitor of viral DNA replication. The results were compared with a similar study of the products of a delayed early gene, US6, encoding glycoprotein D (gD). It was found that the patterns of RNA and protein synthesis from US11 were significantly different to those of gD. US11 products appeared later and accumulated until late in infection, while gD RNA was significantly reduced at late times. In the presence of the inhibitor of DNA synthesis, USll gene expression was reduced 50-to 100-fold while gD expression was reduced five-to tenfold. We conclude that US11 behaves as a true late gene during HSV-1 infection. However, the use of sensitive assays, which allowed the detection of very low levels of USI 1 gene products under conditions designed to eliminate DNA replication, brings into question the absolute requirement for DNA replication for the expression of a true late HSV-1 gene. These results are discussed in terms of current models for the regulation of late gene expression.

Sheep pulmonary adenomatosis (SPA) is a naturally occurring contagious lung tumour of sheep which has been associated aetiologically with a type D-and Brelated retrovirus (Jaagsiekte retrovirus; JSRV). To improve understanding of the aetio-pathogenesis of SPA, the distribution and the sites of JSRV replication in sheep with naturally or experimentally induced SPA or in unaffected controls were identified. New immunological reagents were produced and a blocking enzymelinked immunosorbent assay (B-ELISA) and an immunohistochemical technique for the detection of JSRV major capsid protein at the tissue and cellular levels were developed. JSRV was detected only in the respiratory tract of sheep affected by pulmonary adenomatosis and specifically in the transformed epithelial cells of the alveoli of SPA-affected sheep.

Several studies have implicated a potential role for histamine H(3) receptors in pain processing, although the data are somewhat conflicting. In the present study we investigated the effects of the novel potent and highly selective H(3) receptor antagonists GSK189254 (6-[(3-cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy]-N-methyl-3-pyridinecarboxamide hydrochloride) and GSK334429 (1-(1-methylethyl)-4-([1-[6-(trifluoromethyl)-3-pyridinyl]-4-piperidinyl]carbonyl)hexahydro-1H-1,4-diazepine) in two rat models of neuropathic pain, namely the chronic constriction injury (CCI) model and the varicella-zoster virus (VZV) model. Both GSK189254 (0.3, 3 and/or 10mg/kg p.o.) and GSK334429 (1, 3 and 10mg/kg p.o.) significantly reversed the CCI-induced decrease in paw withdrawal threshold (PWT) measured using an analgesymeter and/or von Frey hairs. In addition, GSK189254 (3mg/kg p.o.) and GSK334429 (10mg/kg p.o.) both reversed the VZV-induced decrease in PWT using von Frey hairs. We also investigated the potential site of action of this analgesic effect of H(3) antagonists using autoradiography. Specific binding to H(3) receptors was demonstrated with [(3)H]-GSK189254 in the dorsal horn of the human and rat spinal cord, and in human dorsal root ganglion (DRG), consistent with the potential involvement of H(3) receptors in pain processing. In conclusion, we have shown for the first time that chronic oral administration of selective H(3) antagonists is effective in reversing neuropathic hypersensitivity in disease-related models, and that specific H(3) receptor binding sites are present in the human DRG and dorsal horn of the spinal cord. These data suggest that H(3) antagonists such as GSK189254 and GSK334429 may be useful for the treatment of neuropathic pain.