In silico homology modeling of dengue virus non-structural 4B (NS4B) protein and its molecular docking studies using triterpenoids.

BACKGROUND: Dengue fever has become a significant worldwide health concern, because of its high morbidity rate and the potential for an increase in mortality rates due to lack of adequate treatment. There is an immediate need for the development of effective medication for dengue fever. METHODS: Homology modeling of dengue virus (DENV) non-structural 4B (NS4B) protein was performed by SWISS-MODEL to predict the 3D structure of the protein. Structure validation was conducted using PROSA, PROCHECK, Ramachandran plot, and VERIFY-3D. MOE software was used to find out the in-Silico inhibitory potential of the five triterpenoids against the DENV-NS4B protein. RESULTS: The SWISS-MODEL was employed to predict the three-dimensional protein structure of the NS4B protein. Through molecular docking, it was found that the chosen triterpenoid NS4B protein had a high binding affinity interaction. It was observed that the NS4B protein binding energy for 15-oxoursolic acid, betulinic acid, ursolic acid, lupeol, and 3-o-acetylursolic acid were - 7.18, - 7.02, - 5.71, - 6.67 and - 8.00 kcal/mol, respectively. CONCLUSIONS: NS4B protein could be a promising target which showed good interaction with tested triterpenoids which can be developed as a potential antiviral drug for controlling dengue virus pathogenesis by inhibiting viral replication. However, further investigations are necessary to validate and confirm their efficacy.

Structural biology of flavivirus NS1 protein and its antibody complexes.

The genus of flavivirus includes many mosquito-borne human pathogens, such as Zika (ZIKV) and the four serotypes of dengue (DENV1-4) viruses, that affect billions of people as evidenced by epidemics and endemicity in many countries and regions in the world. Among the 10 viral proteins encoded by the viral genome, the nonstructural protein 1 (NS1) is the only secreted protein and has been used as a diagnostic biomarker. NS1 has also been an attractive target for its biotherapeutic potential as a vaccine antigen. This review focuses on the recent advances in the structural landscape of the secreted NS1 (sNS1) and its complex with monoclonal antibodies (mAbs). NS1 forms an obligatory dimer, and upon secretion, it has been reported to be hexametric (trimeric dimers) that could dissociate and bind to the epithelial cell membrane. However, high-resolution structural information has been missing about the high-order oligomeric states of sNS1. Several cryoEM studies have since shown that DENV and ZIKV recombinant sNS1 (rsNS1) are in dynamic equilibrium of dimer-tetramer-hexamer states, with tetramer being the predominant form. It was recently revealed that infection-derived sNS1 (isNS1) forms a complex of the NS1 dimer partially embedded in a High-Density Lipoprotein (HDL) particle. Structures of NS1 in complexes with mAbs have also been reported which shed light on their protective roles during infection. The biological significance of the diversity of NS1 oligomeric states remains to be further studied, to inform future research on flaviviral pathogenesis and the development of therapeutics and vaccines. Given the polymorphism of flavivirus NS1 across sample types with variations in antigenicity, we propose a nomenclature to accurately define NS1 based on the localization and origin.

Host serine protease ACOT2 assists DENV proliferation by hydrolyzing viral polyproteins.

Dengue fever is a mosquito-borne tropical disease caused by the dengue virus (DENV). The replication of DENV relies on the processing of its genome-encoded polyprotein by both viral protease NS3 (NS3pro) and host proteases. However, the impact of host proteases on DENV proliferation is not well understood. In this study, we utilized fluorophosphonate-based probes (FPs) to investigate the up-regulation of host serine proteases during DENV infection in detail. Among the identified proteases, acyl-CoA thioesterase 2 (ACOT2), an enzyme that hydrolyzes acyl-CoA molecules to generate fatty acids and free CoA, exhibited cleavage activity against DENV polypeptide substrates. Enzymatic assays and virological experiments confirmed that ACOT2 contributes to DENV propagation during the replication stage by cleaving the viral polyprotein. Docking models provided insights into the binding pocket of viral polypeptides and the catalytic mechanism of ACOT2. Notably, this study is the first to demonstrate that ACOT2 functions as a serine protease to hydrolyze protein substrates. These findings offer novel insights into DENV infection, host response, as well as the potential development of innovative antiviral strategies.IMPORTANCEDENV, one of the major pathogens of Dengue fever, remains a significant public health concern in tropical and subtropical regions worldwide. How DENV efficiently hijacks the host and accesses its life cycle with delicate interaction remains to be elucidated. Here, we deconvoluted that the host protease ACOT2 assists the DENV replication and characterized the ACOT2 as a serine protease involved in the hydrolysis of the DENV polypeptide substrate. Our results not only further the understanding of the DENV life cycle but also provide a possibility for the usage of activity-based proteomics to reveal host-virus interactions.

Prevalence of antibodies to dengue virus, hepadnavirus and rotavirus in non-human primates

The aim of this study was to determine the prevalence of several viral antibodies in non-human primates from two zoological gardens from Venezuela. Only two out of 66 sera were positive for antibodies to dengue virus by hemagglutination inhibition. Six out of 62 sera exhibited antibodies against Hepatitis B virus (HBV) core antigen. Viral DNA was detected by nested PCR in one positive serum and in three negative without serological evidence of HBV infection. Sequence analysis showed the circulation of HBV genotype F, predominant in Venezuela. Antibodies against rotavirus antigens were found in 87 percent (20/23) of Old World primates and in 50 percent (13/26) of New World primates. Both the prevalence of antibodies and the mean O.D. value by ELISA were significantly lower in New World primate sera. These results suggest that non-human primates do not seem to represent an important reservoir for dengue virus infection, highly endemic in Venezuela. Anthropozoonotic infection of HBV seems to occur among primates not only from the Old but also from the New World, reinforcing the importance of vaccination of species at risk. This study also suggests a lower frequency of infection by rotavirus of non-human primates from the New World, compared to primates from the Old World.

En este estudio se determinó la prevalencia de anticuerpos contra varios virus en primates no humanos de dos parques zoológicos de Venezuela. Sólo dos de 66 sueros fueron positivos, por inhibición de la hemaglutinación, para anticuerpos contra virus dengue. Seis de 62 sueros presentaron anticuerpos contra la cápside del virus de la hepatitis B virus (VHB). Se detectó el ADN viral, mediante PCR en dos rondas, en uno de éstos y en tres sueros sin evidencia serológica de infección por VHB. El análisis de la secuencia mostró la circulación del VHB genotipo F, predominante en Venezuela. Un 87 por ciento (20/23) de los sueros de primates del Viejo Mundo y un 50 (13/26) de los del Nuevo Mundo mostraron anticuerpos contra antígenos de rotavirus. Tanto la prevalencia de anticuerpos como los valores promedio de D.O. por ELISA fueron significativamente menores en sueros de primates del Nuevo Mundo. Los primates no humanos no parecen jugar un papel importante como reservorio de la infección por virus dengue, altamente prevalente en el país. La infección por cepas humanas del VHB en primates sugiere infección antroponótica y la importancia de vacunar las especies a riesgo. Los resultados sugieren igualmente una menor frecuencia de infección por rotavirus en primates del Nuevo Mundo.