Wild-type rabies virus phosphoprotein is associated with viral sensitivity to type I interferon treatment.

Rabies virus (RABV) is a single-stranded, negative-sense RNA virus that causes a fatal neurological disease in humans and animals. Our previous studies have shown that lab-adapted, but not wild-type (wt), RABV enhances innate immune responses including type I interferon (IFN) and chemokines. To determine if treatment with type I IFN can inhibit RABV infection, mouse neuroblastoma and baby hamster kidney cells were treated with IFN-α before being infected with lab-adapted or wt RABV. It was found that lab-adapted, but not the wt, RABV was able to replicate in IFN-α-pretreated cells. To determine the genes in wt RABV that confer sensitivity to IFN-α treatment, the P and the glycoprotein (G) genes from the wt RABV were used to replace the respective genes in the lab-adapted RABV. The results revealed that it is the P, not the G, gene that is associated with IFN sensitivity. Further studies have identified the regions containing the self-association domain (residues 59-139) and the C-terminal (residue 175-297) region on the P that might be associated with IFN sensitivity. The expression of ISGs, such as ISG15, ISG56, PKR, OAS-1G, was also investigated and found to be greatly increased in wt, but not in lab-adapted RABV-infected cells. It is possible that the P protein from the lab-adapted RABV can interfere with the downstream events in the interferon-signaling cascade.

Rabies virus-induced apoptosis involves caspase-dependent and caspase-independent pathways.

Previously, it has been shown that the laboratory attenuated rabies virus CVS-B2C, but not the wild-type virus SHBRV, induces apoptosis in mice and the induction of apoptosis is mediated by viral glycoprotein. Induction of apoptosis by CVS-B2C limits the spread of the virus in the CNS. In the present study, we characterized the pathways by which CVS-B2C induces apoptosis. BSR cells were infected with CVS-B2C or SHBRV and harvested at different time points for detection of apoptosis by immunofluorescence and flow cytometry. Apoptosis was detected only in cells infected with CVS-B2C, but not SHBRV. Caspase activity and expression of several apoptotic proteins were analyzed by fluorometric assay and Western blotting. Activation of caspase-8 and -3, but not of caspase-9, was observed in CVS-B2C-infected cells. In addition, the level of expression of Apaf-1 did not change. Furthermore, PARP was cleaved confirming activation of downstream caspases. All these data suggest that CVS-B2C infection activates the extrinsic, but not the intrinsic, apoptotic pathway. In addition, AIF, a caspase-independent apoptotic protein was up-regulated and translocated from the cytoplasm to the nucleus post-infection, suggesting that apoptosis induced by CVS-B2C also involves the activation of a caspase-independent pathway.

Evaluating a surveillance system: live-bird market surveillance for highly pathogenic avian influenza, a case study.

INTRODUCTION: Highly pathogenic avian influenza H5N1 was first reported in poultry in Nigeria in February 2006. The only human case that occurred was linked to contact with poultry in a live bird market (LBM). LBM surveillance was instituted to assess the degree of threat of human exposure to H5N1. The key indicator was detection of H5N1 in LBMs. We evaluated the surveillance system to assess its operations and attributes. METHODS: We used the US Centers for Disease Control and Prevention (CDC) updated guidelines for evaluating public health surveillance systems. We reviewed and analyzed passive surveillance data for HPAI (January 2006-March 2009) from the Avian Influenza National Reference Laboratory, and live bird market surveillance data from the Food and Agriculture Organization of the United Nations, Nigeria. We interviewed key stakeholders and reviewed reports of live bird market surveillance to obtain additional information on the operations of the system. We assessed the key system attributes. RESULTS: A total of 299 cases occurred in 25 (72%) states and the Federal Capital Territory (FCT). The system detected HPAI H5N1 virus in 7 (9.5%) LBMs; 2 (29%) of which were from 2 (18.2%) states with no previous case. A total of 17,852 (91.5%) of samples arrived at the laboratory within 24 hours but laboratory analysis took over 7 days. The sensitivity and positive predictive value (PPV) were 15.4% and 66.7% respectively. CONCLUSION: The system is useful, flexible, complex and not timely, but appears to be meeting its objectives. The isolation of HPAI H5N1 virus in some of these markets is an indication that the markets are possible reservoirs of the virus in Nigeria. We recommend that the Federal Government of Nigeria should dedicate more funds for surveillance for HPAI as this will aid early warning and reduce the risk of a pandemic.

Attenuated rabies virus activates, while pathogenic rabies virus evades, the host innate immune responses in the central nervous system.

Rabies virus (RV) induces encephalomyelitis in humans and animals. However, the pathogenic mechanism of rabies is not fully understood. To investigate the host responses to RV infection, we examined and compared the pathology, particularly the inflammatory responses, and the gene expression profiles in the brains of mice infected with wild-type (wt) virus silver-haired bat RV (SHBRV) or laboratory-adapted virus B2C, using a mouse genomic array (Affymetrix). Extensive inflammatory responses were observed in animals infected with the attenuated RV, but little or no inflammatory responses were found in mice infected with wt RV. Furthermore, attenuated RV induced the expression of the genes involved in the innate immune and antiviral responses, especially those related to the alpha/beta interferon (IFN-alpha/beta) signaling pathways and inflammatory chemokines. For the IFN-alpha/beta signaling pathways, many of the interferon regulatory genes, such as the signal transduction activation transducers and interferon regulatory factors, as well as the effector genes, for example, 2'-5'-oligoadenylate synthetase and myxovirus proteins, are highly induced in mice infected with attenuated RV. However, many of these genes were not up-regulated in mice infected with wt SHBRV. The data obtained by microarray analysis were confirmed by real-time PCR. Together, these data suggest that attenuated RV activates, while pathogenic RV evades, the host innate immune and antiviral responses.