Varicella zoster virus (VZV) is an exclusively human neurotropic alpha-herpesvirus. Primary infection causes varicella (chickenpox), after which virus becomes latent in cranial nerve ganglia, dorsal root ganglia, and autonomic ganglia along the entire neuraxis. Years later, in association with a decline in cell-mediated immunity in elderly and immunocompromised individuals, VZV reactivates and causes a wide range of neurologic disease, including herpes zoster, postherpetic neuralgia, vasculopathy, myelopathy, retinal necrosis, cerebellitis and zoster sine herpete (Fig. 1). Importantly, many of these complications occur without rash. This article discusses the clinical manifestations, treatment, and prevention of VZV infection and reactivation; pathogenesis of VZV infection; and current research focusing on VZV latency, reactivation, and animal models. Clinical manifestations of primary varicella zoster virus infection VaricellaInitial infection with VZV results in chickenpox (varicella), which is typically seen in children 1 to 9 years of age [1]. Primary infection in adults is usually more severe and may be accompanied by interstitial pneumonia. Infection in immunocompromised individuals often causes severe, disseminated disease. Climate seems to affect the epidemiology of varicella. In most temperate climates, more than 90% of people are infected before adolescence [2-5] with an incidence of 13 to 16 cases per 1000 people per year [6][7][8]. In tropical climates, VZV infection occurs later in life and adults are more susceptible than children [9][10][11]. Varicella has a peak incidence in the late winter and spring [10,[12][13][14], and epidemics tend to occur every 2 to 5 years [12][13][14].Varicella is characterized by fever concurrent with a self-limiting rash on the skin and sometimes mucosa. Headache, malaise, and loss of appetite are also seen. The rash begins as macules, rapidly progresses to papules, followed by a vesicular stage and crusting of lesions. Crusts slough off after 1 to 2 weeks. VZV is highly infectious and transmission occurs by direct contact with skin lesions or by respiratory aerosols from infected individuals. Central nervous system complications include self-limiting cerebellar ataxia in 1 in 4000 cases [15], meningitis, meningoencephalitis, and vasculopathy [16]. Strokes may occur months after varicella

Dengue virus type 2 (DEN2), a member of the Flaviviridae family, is a re-emerging human pathogen of global significance. DEN2 nonstructural protein 3 (NS3) has a serine protease domain (NS3-pro) and requires the hydrophilic domain of NS2B (NS2BH) for activation. NS3 is also an RNA-stimulated nucleoside triphosphatase (NTPase)/RNA helicase and a 5-RNA triphosphatase (RTPase). In this study the first biochemical and kinetic properties of full-length NS3 (NS3 FL )-associated NTPase, RTPase, and RNA helicase are presented. The NS3 FL showed an enhanced RNA helicase activity compared with the NS3-pro-minus NS3, which was further enhanced by the presence of the NS2BH (NS2BH-NS3 FL ). An active protease catalytic triad is not required for the stimulatory effect, suggesting that the overall folding of the N-terminal protease domain contributes to this enhancement. In DEN2-infected mammalian cells, NS3 and NS5, the viral 5-RNA methyltransferase/ polymerase, exist as a complex. Therefore, the effect of NS5 on the NS3 NTPase activity was examined. The results show that NS5 stimulated the NS3 NTPase and RTPase activities. The NS5 stimulation of NS3 NTPase was dose-dependent until an equimolar ratio was reached. Moreover, the conserved motif, 184 RKRK, of NS3 played a crucial role in binding to RNA substrate and modulating the NTPase/RNA helicase and RTPase activities of NS3.The mosquito-borne Flavivirus genus, in the Flaviviridae family, includes human pathogens of global distribution and prevalence (for reviews, see Refs. 1-3), and Dengue viruses (DEN) 1 types 1-4 cause the most common infection encountered in humans (4). The diseases caused by DEN infections include from dengue fever, usually a self-limiting disease, to more severe forms, dengue hemorrhagic fever and dengue shock syndrome. These diseases pose a significant threat to humans living in DEN-infected Aedes aegypti mosquitoes endemic in areas that inhabit two-thirds of world population (5) DEN genome is a single-stranded RNA (10,723 nt in length for DEN2 New Guinea C strain used in this study (6)) of positive polarity. The viral RNA contains a long open reading frame coding for a polyprotein precursor. The polyprotein is processed into mature structural proteins, capsid (C), precursor membrane (prM), and envelope (E) and at least seven nonstructural proteins, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5, by cellular signal peptidase and viral serine protease in the endoplasmic reticulum (for review, see Ref. 7). The 5Ј-end of the viral RNA is modified by a type I cap structure (m 7 GpppN; 2Ј-OH moiety of N is methylated). DEN2 NS3 is a multifunctional protein of about 69 kDa. It includes a serine catalytic triad within the N-terminal 185 amino acid residues. The protease domain is activated by the hydrophobic protein NS2B which serves as a cofactor for the protease and forms a complex in the infected cells (8 -12). NS2B has three hydrophobic regions flanking a conserved hydrophilic domain. The hydrophilic domain of NS2B (NS2BH) alone is sufficient for protease act...

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Summary Dengue virus belongs to the family Flaviviridae and is a major emerging pathogen for which the development of vaccines and antiviral therapy has seen little success. The NS3 viral protease is a potential target for antiviral drugs since it is required for virus replication. The goal of this study was to identify novel dengue virus (type 2; DEN2V) protease inhibitors for eventual development as effective anti-flaviviral drugs. The EUDOC docking program was used to computationally screen a small-molecule library for compounds that dock into the P1 pocket and the catalytic site of the DEN2V NS3 protease domain apo-structure (Murthy et al., 1999) and the Bowman-Birk inhibitor-bound structure (Murthy et al., 2000). The top 20 computer–identified hits that demonstrated the most favorable scoring “energies” were selected for in vitro assessment of protease inhibition. Preliminary protease activity assays demonstrated that more than half of the tested compounds were soluble and exhibited in vitro inhibition of the DEN2V protease. Two of these compounds also inhibited viral replication in cell culture experiments, and thus are promising compounds for further development.

West Nile virus and dengue virus are mosquito-borne flaviviruses that cause a large number of human infections each year. No vaccines or chemotherapeutics are currently available. These viruses encode a serine protease that is essential for polyprotein processing, a required step in the viral replication cycle. In this study, a high-throughput screening assay for the West Nile virus protease was employed to screen ϳ32,000 smallmolecule compounds for identification of inhibitors. Lead inhibitor compounds with three distinct core chemical structures (1 to 3) were identified. In a secondary screening of selected compounds, two compounds, belonging to the 8-hydroxyquinoline family (compounds A and B) and containing core structure 1, were identified as potent West Nile virus (WNV) and the four serotypes of dengue virus (DENV1 to DENV4) have recently emerged as significant human pathogens that cause millions of infections each year and result in considerable morbidity and mortality (16,26). WNV was introduced into the Western Hemisphere during an outbreak in the United States in 1999. In the following years, WNV has spread throughout much of North America and has become a major public health concern (reviewed in reference 7). Most WNV infections are asymptomatic; however, about 20% of cases are associated with mild flu-like symptoms. A small fraction of these cases progresses to moresevere clinical manifestations, including encephalitis and/or flaccid paralysis. Currently, there are no approved vaccines or antiviral therapeutics available for WNV-infected humans.The WNV genome consists of approximately 11 kb of RNA of positive polarity, which encodes a single polyprotein that is processed co-and posttranslationally by the host signal peptidase and the viral serine protease into at least 10 proteins. The three structural proteins, capsid (C), prM, and envelope (E), arise from the N terminus of the polyprotein, and the seven nonstructural (NS) proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) arise from the C-terminal portion during processing at the endoplasmic reticulum of the host cell (7, 23).The active form of the viral serine protease consists of a complex of two proteins, NS2B and NS3. NS3 is a multifunctional protein. The amino-terminal domain contains the serine protease catalytic triad, consisting of amino acid residues H51, D75, and S135 (5). This domain interacts with NS2B, a required cofactor, to form the active serine protease (3,8,9,14,15,33,35). Fine mapping of the minimal domain of NS3 has revealed that the amino-terminal 167 residues are sufficient for cis-cleavage at the NS2B-NS3 junction (22).The two-component NS2B/NS3 viral serine protease activity plays a key role in flaviviral polyprotein processing. This is an obligatory step prior to viral RNA replication, thus identifying the viral serine protease as an excellent therapeutic target. The protease cleavage sites in the polyprotein have a pair of basic amino acids (R and K) at the P2 and P1 (occasionally there is a Q at P2) positions, followed ...