Dengue virus, a member of the family Flaviviridae of positive-strand RNA viruses, has seven non-structural proteins: NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5. Except for enzymic activities contained within NS3 and NS5, the roles of the other proteins in virus replication and pathogenesis are not well defined. In this study, a physical interaction between NS4B and the helicase domain of NS3 was identified by using a yeast two-hybrid assay. This interaction was further confirmed by biochemical pull-down and immunoprecipitation assays, both with purified proteins and with dengue virus-infected cell lysates. NS4B co-localized with NS3 in the perinuclear region of infected human cells. Furthermore, NS4B dissociated NS3 from single-stranded RNA and consequently enhanced the helicase activity of NS3 in an in vitro unwinding assay. These results suggest that NS4B modulates dengue virus replication via its interaction with NS3. INTRODUCTIONDengue fever and its more severe form, dengue haemorrhagic fever, are mosquito-borne viral diseases that are caused by one of the four antigenically distinct serotypes of Dengue virus, DENV-1-DENV-4. Dengue fever affects 50-100 million people in the tropical and subtropical regions annually (Gubler, 1998(Gubler, , 2002. Contemporary demographical and lifestyle trends, such as population explosion and urbanization, have led to the spread of this disease to nonendemic regions. The pathogenesis of dengue fever remains poorly characterized and there are no antivirals or vaccines available to counter this emerging disease.Dengue virus belongs to the family Flaviviridae that consists of enveloped, positive-sense, single-stranded RNA (ssRNA) viruses, such as those that cause yellow fever, Japanese encephalitis, West Nile fever and hepatitis C. Its RNA genome is encapsulated in an icosahedral nucleocapsid (30 nm) that is enveloped in a lipid bilayer (10 nm) (Kuhn et al., 2002) consisting of the membrane and envelope proteins. The 11 kb, capped RNA genome encodes a single polyprotein that is processed co-and post-translationally by host signalases, as well as the virus-encoded serine protease, into the three structural and seven non-structural proteins (NS) in the order C (Core)-prM (pre-Membrane)-E (Envelope)-NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5 (Chambers & Rice, 1987;Lindenbach & Rice, 2003).The polymerase, helicase and protease enzymic activities encoded by the dengue virus genome ensure virus replication and polyprotein processing. NS3 (618 aa) is a multifunctional protein with protease, helicase, NTPase and 59-terminal RNA triphosphatase activities (Arias et al., 1993;Benarroch et al., 2004;Falgout et al., 1991;Li et al., 1999;Zhang et al., 1992), whilst NS5 (900 aa) has RNAdependent RNA polymerase and methyltransferase activities (Ackermann & Padmanabhan, 2001;Chu & Westaway, 1987;Egloff et al., 2002;Kapoor et al., 1995;Tan et al., 1996). These two proteins form a functional complex that is vital for flavivirus replication (Brooks et al., 2002;Johansson et al., 2001;Yon et al., 2005). The role...

Background: Dengue and Dengue hemorrhagic fever have emerged as some of the most important mosquito-borne viral diseases in the tropics. The mechanisms of pathogenesis of Dengue remain elusive. Recently, virus-induced apoptosis mediated by the Unfolded Protein Response (UPR) has been hypothesised to represent a crucial pathogenic event in viral infection. In an attempt to evaluate the contribution of the UPR to virus replication, we have characterized each component of this signalling pathway following Dengue virus infection.

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Outbreaks of dengue disease are constant threats to tropical and subtropical populations but range widely in severity, from mild to haemorrhagic fevers, for reasons that are still elusive. We investigated the interferon (IFN) response in infected human cell lines A549 and HepG2, using two strains (NGC and TSV01) of dengue serotype 2 (DEN2) and found that the two viruses exhibited a marked difference in inducing type I IFN response. While TSV01 infection led to activation of type I antiviral genes such as EIF2AK2 (PKR), OAS, ADAR and MX, these responses were absent in NGC-infected cells. Biochemical analysis revealed that NGC but not TSV01 suppressed STAT-1 and STAT-2 activation in response to type I IFN (a and b). However, these two strains did not differ in their response to type II IFN (c). Although unable to suppress IFN signalling, TSV01 infection caused a weaker IFN-b induction compared with NGC, suggesting an alternative mechanism of innate immune escape. We extended our study to clinical isolates of various serotypes and found that while MY10245 (DEN2) and MY22713 (DEN4) could suppress the IFN response in a similar fashion to NGC, three other strains of dengue [EDEN167 (DEN1), MY02569 (DEN1) and MY10340 (DEN2)] were unable to suppress the IFN response, suggesting that this difference is strain-dependent but not serotype-specific. Our report indicates the existence of a strain-specific virulence factor that may impact on disease severity.

Cancer pain is one of the most common, feared, debilitating, and often undertreated symptoms among cancer patients. It needs attention since it has a significant impact on the quality of life (QoL) of the patients. Also, since cancer has emerged as a major health problem in developing countries, there is a need to strengthen preventive strategies for effective cancer pain management and provide comfort to cancer patients. Nonetheless, various barriers limit developing countries toward optimal cancer pain management. To bridge the gap between adequate pain management and burden of cancer pain in developing countries, a comprehensive understanding of the limitations faced and the prevalence of cancer pain should be addressed. The aim of this literature review is to provide a deeper understanding on the factors associated with cancer pain as well as barriers toward optimal cancer pain management in developing countries. Some of the barriers addressed were administrative, judicial, economic, and professional barriers. Also, estimates on the prevalence of cancer pain and detrimental effects of pain on the QoL of cancer patients have been addressed. In summary, pain, which is one of the most debilitating symptoms of cancer, remains uncontrolled and undertreated in developing countries. It has a profound impact on the patient’s QoL and can have physical, psychological, and social consequences; therefore, it needs to be managed urgently and appropriately. Most importantly, optimal treatment of cancer pain should be highlighted as a priority in developing countries and concerted efforts should be made to eliminate different barriers discussed in this review for effective and humane care.