BackgroundIn India, dengue disease is emerging as the most important vector borne public health problem due to rapid and unplanned urbanization, high human density and week management of the disease. Clinical cases are grossly underreported and not much information is available on prevalence and incidence of the disease.MethodologyA cross sectional, stratified, facility based, multistage cluster sampling was conducted between May 4 and June 27, 2017 in Pune city. A total of 1,434 participants were enrolled. The serum samples were tested for detection of historical dengue IgG antibodies by ELISA using the commercial Panbio Dengue IgG Indirect ELISA kit. Anti-dengue IgG-capture Panbio ELISA was used for detection of high titered antibodies to detect recent secondary infection. We used this data to estimate key transmission parameters like force of infection and basic reproductive number. A subset of 120 indirect ELISA positive samples was also tested for Plaque Reduction Neutralizing Antibodies for determining serotype-specific prevalence.FindingsOverall, 81% participants were infected with dengue virus (DENV) at least once if not more. The positivity was significantly different in different age groups. All the adults above 70 years were positive for DENV antibodies. Over 69% participants were positive for neutralizing antibodies against all 4 serotypes suggesting intense transmission of all DENV serotypes in Pune. Age-specific seroprevalence was consistent with long-term, endemic circulation of DENV. There was an increasing trend with age, from 21.6% among <36 months to 59.4% in age group 10–12 years. We estimate that 8.68% of the susceptible population gets infected by DENV each year resulting into more than 3,00,000 infections and about 47,000 to 59,000 cases per year. This transmission intensity is similar to that reported from other known hyper-endemic settings in Southeast Asia and the Americas but significantly lower than report from Chennai.ConclusionsOur study suggests that Pune city has high disease burden, all 4 serotypes are circulating, significant spatial heterogeneity in seroprevalence and suboptimal immunity in younger age groups. This would allow informed decisions to be made on management of dengue and introduction of upcoming dengue vaccines in the city.

Arthropod-borne viruses of the alphavirus and flavivirus genera are human pathogens of significant concern, and currently, no specific antiviral treatment is available for these viruses. In this study, the antiviral mechanisms of natural small molecules against Dengue virus (DENV) and Chikungunya virus (CHIKV) have been investigated. Herbacetin (HC) and Caffeic acid phenethyl ester (CAPE) showed depletion of polyamine levels in Vero cells as demonstrated by thin-layer chromatography (TLC). As polyamines are known to play a role in viral replication and transcription, HC and CAPE were expected to inhibit virus replication by reducing polyamine levels. To test this hypothesis, HC and CAPE were evaluated for antiviral activities using a cell-based virus yield assay by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), plaque reduction assay, and immunofluorescence assay (IFA). HC and CAPE displayed potent inhibition with EC50 of 463 nM and 0.417 nM for CHIKV and 8.5 uM and 1.15 uM for DENV, respectively. Interestingly, however, the addition of exogenous polyamines did not completely rescue the virus titer in both CHIKV and DENV infected cells and this indicated additional antiviral mechanisms for HC and CAPE. Further, in silico analysis indicated that HC and CAPE directly target the viral methyltransferases (MTase) of CHIKV and DENV. A high throughput ELISA-based assay that quantifies m7GMP-nsP1 adduct was employed to validate inhibition of CHIKV nsP1 MTase and IC50 was calculated to be 0.009 uM and 0.08 uM for CAPE and HC respectively. Altogether, the identification of natural small molecules as antivirals opens the door for the development of antiviral therapies for the treatment of CHIKV and DENV infections.

Arboviruses have the potential to spread quickly and cause a global health emergency. These are RNA viruses that use RNA-dependent RNA polymerase (RdRp) for their replication. RdRp lacks proofreading activity, leading to high error rates, low replicative fidelity, and more genetic variability. In addition, shorter generation time and faster evolutionary rate of these viruses lead to re-emergence and recurrence of arboviral infections due to the emergence of new variants and the development of antiviral resistance. During the replication inside the host cell through protein-protein interactions (PPIs), these viruses interact with several host factors and utilize the host cellular machinery for their benefit. Besides this, viruses employ several transmission strategies to combat host innate and adaptive immune responses by manipulating the signaling and metabolic pathways of the hosts. Hence, antiviral therapies targeting host-virus PPIs can provide an alternative broad-spectrum strategy against RNA viruses. The approach of targeting virus-specific proteins for developing antivirals is expected to solve the problem of antiviral drug resistance and combat emerging new variants of these viruses. This review focuses on host-virus PPIs of arboviral infections that directly affect the host immune signaling and metabolic pathways. Better understanding of these mechanisms will develop new therapeutic tools to treat viral infections.

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