Cocculus hirsutus-Derived Phytopharmaceutical Drug Has Potent Anti-dengue Activity.

Dengue is a serious public health concern worldwide, with ∼3 billion people at risk of contracting dengue virus (DENV) infections, with some suffering severe consequences of disease and leading to death. Currently, there is no broad use vaccine or drug available for the prevention or treatment of dengue, which leaves only anti-mosquito strategies to combat the dengue menace. The present study is an extension of our earlier study aimed at determining the in vitro and in vivo protective effects of a plant-derived phytopharmaceutical drug for the treatment of dengue. In our previous report, we had identified a methanolic extract of aerial parts of Cissampelos pareira to exhibit in vitro and in vivo anti-dengue activity against all the four DENV serotypes. The dried aerial parts of C. pareira supplied by local vendors were often found to be mixed with aerial parts of another plant of the same Menispermaceae family, Cocculus hirsutus, which shares common homology with C. pareira. In the current study, we have found C. hirsutus to have more potent anti-dengue activity as compared with C. pareira. The stem part of C. hirsutus was found to be more potent (∼25 times) than the aerial part (stem and leaf) irrespective of the extraction solvent used, viz., denatured spirit, hydro-alcohol (50:50), and aqueous. Moreover, the anti-dengue activity of stem extract in all the solvents was comparable. Hence, an aqueous extract of the stem of C. hirsutus (AQCH) was selected due to greater regulatory compliance. Five chemical markers, viz., Sinococuline, 20-Hydroxyecdysone, Makisterone-A, Magnoflorine, and Coniferyl alcohol, were identified in fingerprinting analysis. In a test of primary dengue infection in the AG129 mice model, AQCH extract at 25 mg/kg body weight exhibited protection when administered four and three times a day. The AQCH was also protective in the secondary DENV-infected AG129 mice model at 25 mg/kg/dose when administered four and three times a day. Additionally, the AQCH extract reduced serum viremia and small intestinal pathologies, viz., viral load, pro-inflammatory cytokines, and vascular leakage. Based on these findings, we have undertaken the potential preclinical development of C. hirsutus-based phytopharmaceutical, which could be studied further for its clinical development for treating dengue.

Next generation designer virus-like particle vaccines for dengue.

INTRODUCTION: A safe and efficacious vaccine for dengue continues to be an unmet public health need. The recent licensing of a dengue vaccine (Dengvaxia) developed by Sanofi has brought to the fore the safety issue of vaccine-induced infection enhancement. AREAS COVERED: This article focuses on two new yeast-produced tetravalent dengue envelope domain III-displaying virus-like particulate vaccine candidates reported in early 2018 and reviews the rationale underlying their design, and pre-clinical data which suggest that these may offer promising alternate options. EXPERT COMMENTARY: These are the only vaccine candidates so far to have demonstrated the induction of primarily serotype-specific neutralizing antibodies to all dengue virus serotypes in experimental animals. Interestingly, these antibodies lack infection-enhancing potential when evaluated using the AG129 mouse model.

Dengue envelope-based 'four-in-one' virus-like particles produced using Pichia pastoris induce enhancement-lacking, domain III-directed tetravalent neutralising antibodies in mice.

Dengue is a significant public health problem worldwide, caused by four antigenically distinct mosquito-borne dengue virus (DENV) serotypes. Antibodies to any given DENV serotype which can afford protection against that serotype tend to enhance infection by other DENV serotypes, by a phenomenon termed antibody-dependent enhancement (ADE). Antibodies to the viral pre-membrane (prM) protein have been implicated in ADE. We show that co-expression of the envelope protein of all four DENV serotypes, in the yeast Pichia pastoris, leads to their co-assembly, in the absence of prM, into tetravalent mosaic VLPs (T-mVLPs), which retain the serotype-specific antigenic integrity and immunogenicity of all four types of their monomeric precursors. Following a three-dose immunisation schedule, the T-mVLPs elicited EDIII-directed antibodies in mice which could neutralise all four DENV serotypes. Importantly, anti-T-mVLP antibodies did not augment sub-lethal DENV-2 infection of dengue-sensitive AG129 mice, based on multiple parameters. The 'four-in-one' tetravalent T-mVLPs possess multiple desirable features which may potentially contribute to safety (non-viral, prM-lacking and ADE potential-lacking), immunogenicity (induction of virus-neutralising antibodies), and low cost (single tetravalent immunogen produced using P. pastoris, an expression system known for its high productivity using simple inexpensive media). These results strongly warrant further exploration of this vaccine candidate.

Ascorbic acid inhibits human insulin aggregation and protects against amyloid induced cytotoxicity.

Protein aggregation into oligomers and fibrils are associated with many human pathophysiologies. Compounds that modulate protein aggregation and interact with preformed fibrils and convert them to less toxic species, expect to serve as promising drug candidates and aid to the drug development efforts against aggregation diseases. In present study, the kinetics of amyloid fibril formation by human insulin (HI) and the anti-amyloidogenic activity of ascorbic acid (AA) were investigated by employing various spectroscopic, imaging and computational approaches. We demonstrate that ascorbic acid significantly inhibits the fibrillation of HI in a dose-dependent manner. Interestingly ascorbic acid destabilise the preformed amyloid fibrils and protects human neuroblastoma cell line (SH- SY5Y) against amyloid induced cytotoxicity. The present data signifies the role of ascorbic acid that can serve as potential molecule in preventing human insulin aggregation and associated pathophysiologies.

Recombinant Dengue Virus 4 Envelope Glycoprotein Virus-Like Particles Derived from Pichia pastoris are Capable of Eliciting Homotypic Domain III-Directed Neutralizing Antibodies.

Dengue is a viral pandemic caused by four dengue virus serotypes (DENV-1, 2, 3, and 4) transmitted by Aedes mosquitoes. Reportedly, there has been a 2-fold increase in dengue cases every decade. An efficacious tetravalent vaccine, which can provide long-term immunity against all four serotypes in all target populations, is still unavailable. Despite the progress being made in the live virus-based dengue vaccines, the World Health Organization strongly recommends the development of alternative approaches for safe, affordable, and efficacious dengue vaccine candidates. We have explored virus-like particles (VLPs)-based nonreplicating subunit vaccine approach and have developed recombinant envelope ectodomains of DENV-1, 2, and 3 expressed in Pichia pastoris These self-assembled into VLPs without pre-membrane (prM) protein, which limits the generation of enhancing antibodies, and elicited type-specific neutralizing antibodies against the respective serotype. Encouraged by these results, we have extended this work further by developing P. pastoris-expressed DENV-4 ectodomain (DENV-4 E) in this study, which was found to be glycosylated and assembled into spherical VLPs without prM, and displayed critical neutralizing epitopes on its surface. These VLPs were found to be immunogenic in mice and elicited DENV-4-specific neutralizing antibodies, which were predominantly directed against envelope domain III, implicated in host-receptor recognition and virus entry. These observations underscore the potential of VLP-based nonreplicative vaccine approach as a means to develop a safe, efficacious, and tetravalent dengue subunit vaccine. This work paves the way for the evaluation of a DENV E-based tetravalent dengue vaccine candidate, as an alternative to live virus-based dengue vaccines.

Virus-like particles derived from Pichia pastoris-expressed dengue virus type 1 glycoprotein elicit homotypic virus-neutralizing envelope domain III-directed antibodies.

BACKGROUND: Four antigenically distinct serotypes (1-4) of dengue viruses (DENVs) cause dengue disease. Antibodies to any one DENV serotype have the potential to predispose an individual to more severe disease upon infection with a different DENV serotype. A dengue vaccine must elicit homotypic neutralizing antibodies to all four DENV serotypes to avoid the risk of such antibody-dependent enhancement in the vaccine recipient. This is a formidable challenge as evident from the lack of protective efficacy against DENV-2 by a tetravalent live attenuated dengue vaccine that has completed phase III trials recently. These trial data underscore the need to explore non-replicating subunit vaccine alternatives. Recently, using the methylotrophic yeast Pichia pastoris, we showed that DENV-2 and DENV-3 envelope (E) glycoproteins, expressed in absence of prM, implicated in causing severe dengue disease, self-assemble into virus-like particles (VLPs), which elicit predominantly virus-neutralizing antibodies and confer significant protection against lethal DENV challenge in an animal model. The current study extends this work to a third DENV serotype. RESULTS: We cloned and expressed DENV-1 E antigen in P. pastoris, and purified it to near homogeneity. Recombinant DENV-1 E underwent post-translational processing, namely, signal peptide cleavage and glycosylation. Purified DENV-1 E self-assembled into stable VLPs, based on electron microscopy and dynamic light scattering analysis. Epitope mapping with monoclonal antibodies revealed that the VLPs retained the overall antigenic integrity of the virion particles despite the absence of prM. Subtle changes accompanied the efficient display of E domain III (EDIII), which contains type-specific neutralizing epitopes. These VLPs were immunogenic, eliciting predominantly homotypic EDIII-directed DENV-1-specific neutralizing antibodies. CONCLUSIONS: This work demonstrates the inherent potential of P. pastoris-expressed DENV-1 E glycoprotein to self-assemble into VLPs eliciting predominantly homotypic neutralizing antibodies. This work justifies an investigation of the last remaining serotype, namely, DENV-4, to assess if it also shares the desirable vaccine potential manifested by the remaining three DENV serotypes. Such efforts could make it possible to envisage the development of a tetravalent dengue vaccine based on VLPs of P. pastoris-expressed E glycoproteins of the four DENV serotypes.

Vitamin k3 inhibits protein aggregation: Implication in the treatment of amyloid diseases.

Protein misfolding and aggregation have been associated with several human diseases such as Alzheimer's, Parkinson's and familial amyloid polyneuropathy etc. In this study, anti-fibrillation activity of vitamin k3 and its effect on the kinetics of amyloid formation of hen egg white lysozyme (HEWL) and Aß-42 peptide were investigated. Here, in combination with Thioflavin T (ThT) fluorescence assay, circular dichroism (CD), transmission electron microscopy and cell cytotoxicity assay, we demonstrated that vitamin k3 significantly inhibits fibril formation as well as the inhibitory effect is dose dependent manner. Our experimental studies inferred that vitamin k3 exert its neuro protective effect against amyloid induced cytotoxicity through concerted pathway, modifying the aggregation formation towards formation of nontoxic aggregates. Molecular docking demonstrated that vitamin k3 mediated inhibition of HEWL and Aß-42 fibrillogenesis may be initiated by interacting with proteolytic resistant and aggregation prone regions respectively. This work would provide an insight into the mechanism of protein aggregation inhibition by vitamin k3; pave the way for discovery of other small molecules that may exert similar effect against amyloid formation and its associated neurodegenerative diseases.

Interplay of multiple interaction forces: Binding of tyrosine kinase inhibitor nintedanib with human serum albumin.

In this study, we have investigated the binding affinity of the newly approved tyrosine kinase inhibitor nintedanib (NIB) with human serum albumin under simulated physiological condition. The obtained results demonstrate that fluorescence intensity of human serum albumin (HSA) gets quenched by NIB and quenching occurs in static manner. Binding parameters calculated from modified Stern-Volmer equation shows that the drug binds to human serum albumin with a binding constant in the order of 10(3), with the number of binding sites approximately equal to one. Synchronous fluorescence data deciphered the change in the microenvironment of tryptophan (Trp) residue in HSA. Circular dichroism data showed an increase in helical content upon drug binding. Dynamic light scattering measurements deciphered the reduction in hydrodynamic radii of the protein, further differential scanning calorimetry results shows that nintedanib increase the thermostability of HSA. Molecular docking results demonstrated that major binding forces involved in the complex formation are hydrogen bonding and hydrophobic interaction.