Inflammatory responses in the nervous system of mice infected with a street isolate of rabies virus

Rabies virus causes severe encephalitis that is invariably fatal for the victim. However, the contribution of the virus and the host to damage of the CNS is unclear. In order to investigate this we studied the neuropathology and CNS gene expression patterns in a murine model of rabies using a 'street' isolate RV61. This virus was derived from a human case of disease. In this model, infection of the CNS progresses rapidly following inoculation in the periphery, leading to extensive virus replication in the brain and the development of disease. However, previous studies have found little evidence of inflammation and lymphocyte infiltration in many regions of the CNS of infected mice. During the current study virus replication was detected in the dorsal root ganglia (DRG), spinal cord, brain and salivary gland at 11 days postinfection (dpi). Mononuclear cell infiltration was observed in the DRG and to a lesser extent, the spinal cord. Immunolabelling demonstrated that T-lymphocytes were the dominant population of infiltrating cells. Murine innate immune response gene transcripts were detected in the brain as early as 5 dpi. At 11 dpi, coincidentwith the onset of disease, elevated levels of mRNA transcripts were recorded for type-1 (alpha and beta) and type-2 interferon (gamma) and certain chemokines (CCL5 and CXCL10) with chemotactic properties for T-cells. We suggest that damage to the DRG and spinal cord could be due to a combination of both virus infection and the infiltration of T-cells.

The necrotic gene in Drosophila corresponds to one of a cluster of three serpin transcripts mapping at 43A1.2

Mutants of the necrotic (nec) gene in Drosophila melanogaster die in the late pupal stage as pharate adults, or hatch as weak, but relatively normal-looking, flies. Adults develop black melanized spots on the body and leg joints, the abdomen swells with hemolymph, and flies die within 3 or 4 days of eclosion. The TOLL-mediated immune response to fungal infections is constitutively activated in nec mutants and pleiotropic phenotypes include melanization and cellular necrosis. These changes are consistent with activation of one or more proteolytic cascades. The nec gene corresponds to Spn43Ac, one of a cluster of three putative serine proteinase inhibitors at 43A1.2, on the right arm of chromosome 2. Although serpins have been implicated in the activation of many diverse pathways, lack of an individual serpin rarely causes a detectable phenotype. Absence of Spn43Ac, however, gives a clear phenotype, which will allow a mutational analysis of critical features of the molecular structure of serpins.

The Drosophila embargoed gene is required for larval progression and encodes the functional homolog of schizosaccharomyces Crm1

The CRM1 (Exportin 1) protein is a receptor for leucine-rich nuclear export signal sequences. We have molecularly characterized the Drosophila melanogaster embargoed (emb) gene and find that it encodes a product with 49 and 71% sequence identity to the fission yeast Schizosaccharomyces pombe and human CRM1 proteins, respectively. We show that expression of the emb cDNA is sufficient to suppress the growth phenotype of both conditional-lethal and null S. pombe crm1(-) mutant strains, suggesting that emb encodes the functional homologue of the S. pombe Crm1 protein. Through mutagenesis screens we have recovered a series of recessive lethal emb mutations. There is a substantial maternal contribution of emb mRNA and animals hemizygous for our emb alleles can develop to second instar larvae but persist at this stage and consistently fail to undergo the molt to the third instar stage. We see a nuclear accumulation of endogenous actin in the intestinal epithelial cells of the emb mutant larvae, consistent with a role for the emb gene product in nuclear export of actin protein.