Project description:The capability of the U.S. Food and Drug Administration Enteric Viruses tiling microarray (FDA-EVIR) was assessed for rapid molecular identification of human norovirus (NoV) and hepatitis A virus (HAV) extracted from artificially inoculated fresh produce. Two published viral extraction strategies, total RNA extraction or virus particle isolation, were employed to prepare the viral targets. We also assessed the amount of viral RNA extracted from celery by three commercially-available kits and how well that RNA performed on the FDA-EVIR. Our results confirm that FDA-EVIR can correctly identify common enteric viruses isolated from fresh produce and is capable of identifying single and mixed species of viruses, as well as distinguishing among genotypes. Extending microarray methods to other food matrices should provide important support to surveillance and outbreak investigations.
Project description:Murine norovirus is genetically similar to human norovirus, and offers both an efficient in vitro cell culture system and animal model by which to investigate the molecular basis of replication. Here, we present a detailed global view of host alterations to cellular pathways that occur during the progression of a norovirus infection. This was accomplished for both RAW264.7 (RAW) cells, an immortalized cell line widely used in in vitro replication studies, and primary bone marrow-derived macrophages (BMDM), representing a permissive in vivo target cell in the host. Murine norovirus replicated in both cell types, although detected genome copies were approximately one log lower in BMDM compared to RAW cells. RAW and BMDM cells shared an IRF3/7-based IFN response that occurred early in infection. In RAW264.7 cells, transcriptional upregulation and INF-ß expression were not coupled, in that a significant delay in the detection of secreted INF-ß was observed. In contrast, primary BMDM showed an early upregulation of transcripts and immediate release of INF-ß that might account for lower virus yield. Differences in the transcriptional pathway responses included a marked decrease in expression of key genes in the cell cycle and lipid synthesis pathways in RAW264.7 cells compared to that of BMDM. Our comparative analysis indicates the existence of varying host responses to virus infection in populations of permissive cells. Awareness of these differences at the gene level will be important in the application of a given permissive cell culture system to the study of norovirus immunity, pathogenesis, and drug development.
Project description:Capability of FDA-EVIR Microarray for Detection of Norovirus and Hepatitis A Virus in Inoculated Tomatoes, Green Onions, and Celery
Project description:Passive immunoprophylaxis or immunotherapy with norovirus-neutralizing monoclonal antibodies (MAbs) could be a useful treatment for high-risk populations, including infants and young children, the elderly, and certain patients who are debilitated or immunocompromised. In order to obtain antinorovirus MAbs with therapeutic potential, we stimulated a strong adaptive immune response in chimpanzees to the prototype norovirus strain Norwalk virus (NV) (genogroup I.1). A combinatorial phage Fab display library derived from mRNA of the chimpanzees' bone marrow was prepared, and four distinct Fabs reactive with Norwalk recombinant virus-like particles (rVLPs) were recovered, with estimated binding affinities in the subnanomolar range. Mapping studies showed that the four Fabs recognized three different conformational epitopes in the protruding (P) domain of NV VP1, the major capsid protein. The epitope of one of the Fabs, G4, was further mapped to a specific site involving a key amino acid residue, Gly365. One additional specific Fab (F11) was recovered months later from immortalized memory B cells and partially characterized. The anti-NV Fabs were converted into full-length IgG (MAbs) with human γ1 heavy chain constant regions. The anti-NV MAbs were tested in the two available surrogate assays for Norwalk virus neutralization, which showed that the MAbs could block carbohydrate binding and inhibit hemagglutination by NV rVLP. By mixing a single MAb with live Norwalk virus prior to challenge, MAbs D8 and B7 neutralized the virus and prevented infection in a chimpanzee. Because chimpanzee immunoglobulins are virtually identical to human immunoglobulins, these chimpanzee anticapsid MAbs may have a clinical application.