Monoclonal antibody to dengue capsid protein: its application in dengue studies

In vitro and in vivo neutralization of Dengue virus by a single domain antibody

To alleviate the contribution of antibody dependent enhancement in DenV pathogenesis, we obtain a DenV neutralizing single domain antibody (sdAb) from an in-house constructed phage display library of camelid VHH. The anti-DenV sdAb specifically reacts with the envelope (E) protein of DenV with a Kd value of 2x108. Molecular dynamic simulations and docking analysis show that the sdAb interacts with the DenV(E) protein via domain II (EDII) and interferes with the virus internalization process. The anti-DenV(E) sdAb potently inhibits the infectivity of a DenV(E) protein expressing pseudovirus as well as that of a virulent DenV in vitro. A mouse adapted DenV2 induces 100% mortality in the infected IFNRKO mice, but the animals injected with the sdAb neutralized virus remain fully protected. Furthermore, the therapeutically administered anti-DenV(E) sdAb slows down the disease progression and enhances the survival of DenV infected animals. In conclusion, we report an anti-DenV(E) sdAb as a potential therapy to manage DenV pathogenesis.

Natural antibody responses to the capsid protein in sera of Dengue infected patients from Sri Lanka

This study aims to characterize the antigenicity of the Capsid (C) protein and the human antibody responses to C protein from the four dengue virus (DENV) serotypes. Parker hydrophilicity prediction, Emini surface accessibility prediction and Karplus & Schulz flexibility predictions were used to bioinformatically characterize antigenicity. The human antibody response to C protein was assessed by ELISA using immune sera and an array of overlapping DENV2 C peptides. DENV2 C protein peptides P1 (located on C protein at 2–18 a.a), P11 (79–95 a.a) and P12 (86–101 a.a) were recognized by most individuals exposed to infections with only one of the 4 DENV serotypes as well as people exposed to infections with two serotypes. These conserved peptide epitopes are located on the amino (1–40 a.a) and carboxy (70–100 a.a) terminal regions of C protein, which were predicted to be antigenic using different bioinformatic tools. DENV2 C peptide P6 (39–56 a.a) was recognized by all individuals exposed to DENV2 infections, some individuals exposed to DENV4 infections and none of the individuals exposed to DENV1 or 3 infections. Thus, unlike C peptides P1, P11 and P12, which contain epitopes, recognized by DENV serotype cross-reactive antibodies, DENV2 peptide P6 contains an epitope that is preferentially recognized by antibodies in people exposed to this serotype compared to other serotypes. We discuss our results in the context of the known structure of C protein and recent work on the human B-cell response to DENV infection.

Modification of S-Adenosyl-l-Homocysteine as Inhibitor of Nonstructural Protein 5 Methyltransferase Dengue Virus Through Molecular Docking and Molecular Dynamics Simulation

Dengue fever is still a major threat worldwide, approximately threatening two-fifths of the world's population in tropical and subtropical countries. Nonstructural protein 5 (NS5) methyltransferase enzyme plays a vital role in the process of messenger RNA capping of dengue by transferring methyl groups from S-adenosyl-l-methionine to N7 atom of the guanine bases of RNA and the RNA ribose group of 2'OH, resulting in S-adenosyl-l-homocysteine (SAH). The modification of SAH compound was screened using molecular docking and molecular dynamics simulation, along with computational ADME-Tox (absorption, distribution, metabolism, excretion, and toxicity) test. The 2 simulations were performed using Molecular Operating Environment (MOE) 2008.10 software, whereas the ADME-Tox test was performed using various software. The modification of SAH compound was done using several functional groups that possess different polarities and properties, resulting in 3460 ligands to be docked. After conducting docking simulation, we earned 3 best ligands (SAH-M331, SAH-M2696, and SAH-M1356) based on ΔG_binding and molecular interactions, which show better results than the standard ligands. Moreover, the results of molecular dynamics simulation show that the best ligands are still able to maintain the active site residue interaction with the binding site until the end of the simulation. After a series of molecular docking and molecular dynamics simulation were performed, we concluded that SAH-M1356 ligand is the most potential SAH-based compound to inhibit NS5 methyltransferase enzyme for treating dengue fever.

Rapid Detection Strategies for the Global Threat of Zika Virus: Current State, New Hypotheses, and Limitations

The current scenario regarding the widespread Zika virus (ZIKV) has resulted in numerous diagnostic studies, specifically in South America and in locations where there is frequent entry of travelers returning from ZIKV-affected areas, including pregnant women with or without clinical symptoms of ZIKV infection. The World Health Organization, WHO, announced that millions of cases of ZIKV are likely to occur in the USA in the near future. This situation has created an alarming public health emergency of international concern requiring the detection of this life-threatening viral candidate due to increased cases of newborn microcephaly associated with ZIKV infection. Hence, this review reports possible methods and strategies for the fast and reliable detection of ZIKV with particular emphasis on current updates, knowledge, and new hypotheses that might be helpful for medical professionals in poor and developing countries that urgently need to address this problem. In particular, we emphasize liposome-based biosensors. Although these biosensors are currently among the less popular tools for human disease detection, they have become useful tools for the screening and detection of pathogenic bacteria, fungi, and viruses because of their versatile advantageous features compared to other sensing devices. This review summarizes the currently available methods employed for the rapid detection of ZIKV and suggests an innovative approach involving the application of a liposome-based hypothesis for the development of new strategies for ZIKV detection and their use as effective biomedicinal tools.

Development and Characterization of Monoclonal Antibodies to Yellow Fever Virus and Application in Antigen Detection and IgM Capture Enzyme-Linked Immunosorbent Assay

Yellow fever (YF) is an acute hemorrhagic viral infection transmitted by mosquitoes in Africa and South America. The major challenge in YF disease detection and confirmation of outbreaks in Africa is the limited availability of reference laboratories and the persistent lack of access to diagnostic tests. We used wild-type YF virus sequences to generate recombinant envelope protein in an Escherichia coli expression system. Both the recombinant protein and sucrose gradient-purified YF vaccine virus 17D (YF-17D) were used to immunize BALB/c mice to generate monoclonal antibodies (MAbs). Eight MAbs were established and systematically characterized by indirect enzyme-linked immunosorbent assay (ELISA), Western blot analysis, and immunofluorescence assay (IFA). The established MAbs showed strong reactivity with wild-type YF virus and recombinant protein with no detectable cross-reactivity to dengue virus or Japanese encephalitis virus. Epitope mapping showed strong binding of three MAbs to amino acid positions 1 to 51, while two MAbs mapped to amino acid positions 52 to 135 of the envelope protein. The remaining three MAbs did not show reactivity to envelope fragments. The established MAbs exert no neutralization against wild-type YF and 17D viruses (titer of <10 for both strains). The applicability of MAbs 8H3 and 3F4 was further evaluated using IgM capture ELISA. A total of 49 serum samples were analyzed, among which 12 positive patient and vaccinee samples were correctly identified. Using serum samples that were 2-fold serially diluted, the IgM capture ELISA was able to detect all YF-positive samples. Furthermore, MAb-based antigen detection ELISA enabled the detection of virus in culture supernatants containing titers of about 1,000 focus-forming units.

Dengue laboratory diagnosis: still some room for improvement

Dengue is the most important and widely distributed arthropod-borne viral disease affecting humans. The number of dengue virus infections has steadily grown and more than 100 countries survey dengue incidence every year. Due to the lack of an approved antiviral treatment or licensed preventative vaccine, accurate and opportune diagnosis is commended for efficient dengue epidemiological surveillance, to propose control measures in order to curtail outbreaks timely and treat patients satisfactorily. In this review, the basis, application and indications for different diagnostic tests are described, and their advantages and limitations considered. At the end of this piece, we speculate what the future may hold for the diagnosis of dengue infections.