Direct and indirect interactions in the recognition between a cross-neutralizing antibody and the four serotypes of dengue virus

Impact of secondary infections on dengue presentation: A cross-sectional study in a tertiary care hospital in Uttar Pradesh, India

BACKGROUND

Recently, a wide range variety of manifestations, including a self‑limiting to severe illness, has been increasingly reported in dengue. Few studies attract attention to severe dengue, mainly observed in secondary infection. With this background, this study aims to provide a comprehensive overview to differentiate primary from secondary dengue using serology (IgG) and the possible association of severity of illness in secondary dengue.

METHODS

Present retrospective cross-sectional study was conducted at a North Indian tertiary care center from September 2021 to January 2022. Clinical data of confirmed dengue patients from the medicine department were collected and assigned as primary and secondary dengue.

RESULTS

Of the 220 dengue patients, 22 (10 %) had secondary dengue infection. Hemorrhagic manifestations were reported in 58/220 (26.4 %) cases while 7/22 (31.8 %) in secondary dengue. Prevalent hemorrhagic manifestations in secondary dengue include purpura (27.3 %), vaginal bleeding (4.5 %), melaena (9.1 %), and epistaxis (4.5 %). In addition, 42 (19.1 %) patients had pancytopenia, and 8 (36.6 %) cases were of secondary dengue. Hepatic dysfunction was noted in 164 (74.5 %) cases. Notably, all secondary dengue cases (22;100 %) had hepatic dysfunction and severe in 9 (40.9 %) cases. In addition, in secondary dengue patients, evidence of plasma leakages such as hypoproteinemia 7 (31.8 %) and ascites (35 %) were statistically more frequent. Overall, two deaths (0.9 %) were reported, and were one in each group.

CONCLUSIONS

Many parameters, including hemorrhagic manifestation (melaena), hematological characteristic (pancytopenia), evidence of plasma leakage (hypoproteinemia and ascites), gastrointestinal (GB wall thickening and hepatic dysfunction) and reduction in mean hemoglobin and platelet count were found to be statistically significant in secondary dengue infection. Additionally, early classification of secondary dengue may help to anticipate its severity and allow for early strategic intervention/management to lower morbidity and mortality.

Microwave resonator-based sensor system for specific antibody detection

An antibody-detecting sensor is described that is based on a microwave electrodynamic resonator. A polystyrene film with immobilized bacteria deposited on a lithium niobate plate was placed at one end of the resonator and was used as the sensing element. The second end was electrically shorted. The frequency and depth of the reflection coefficient S11 for three resonances in the range 6.5-8.5 GHz were used as an analytical signal to examine antibody interactions with bacteria and determine the time required for cell immobilization. The sensor distinguished between situations in which bacteria interacted with specific antibodies and those in which no such interaction occurred (control). Although the cell-antibody interaction changed the frequency and depth of the second and third resonance peaks, the parameters of the first resonance peak did not change. The interaction of cells with nonspecific antibodies did not change the parameters of any of the peaks. These results are promising for use in the design of methods to detect specific antibodies, which can supplement the existing methods of antibody analysis.

The Evolution of Molecular Recognition: From Antibodies to Molecularly Imprinted Polymers (MIPs) as Artificial Counterpart

Molecular recognition is a useful property shared by various molecules, such as antibodies, aptamers and molecularly imprinted polymers (MIPs). It allows these molecules to be potentially involved in many applications including biological and pharmaceutical research, diagnostics, theranostics, therapy and drug delivery. Antibodies, naturally produced by plasma cells, have been exploited for this purpose, but they present noticeable drawbacks, above all production cost and time. Therefore, several research studies for similar applications have been carried out about MIPs and the main studies are reported in this review. MIPs, indeed, are more versatile and cost-effective than conventional antibodies, but the lack of toxicity studies and their scarce use for practical applications, make it that further investigations on this kind of molecules need to be conducted.

DNA Switch: Toehold-Mediated DNA Isothermal Amplification for Dengue Serotyping

The inherent ability of nucleic acids to recognize a complementary pair has gained wide popularity in DNA sensor applications. DNA molecules can be produced in bulk and easily incorporated with various nanomaterials for sensing applications. More complex designs and sophisticated DNA sensors have been reported over the years to allow DNA detection in a faster, cheaper, and more convenient manner. Here, we report a DNA sensor designed to function like a switch to turn “on” silver nanocluster (AgNC) generation in the presence of a specific DNA target. By defining the probe region sequence, we are able to tune the color of the AgNC generated in direct relation to the different targets. As a proof of concept, we used dengue RNA-dependent RNA polymerase conserved sequences from all four serotypes as targets. This method was able to distinguish each dengue serotype by generating the serotype-respective AgNCs. The DNA switch was also able to identify and amplify the correct target in a mixture of targets with good specificity. This strategy has a detection limit of between 1.5 and 2.0 µM depending on the sequence of AgNC. The DNA switch approach provides an attractive alternative for single-target or multiplex DNA detection.

Structural basis for cross-reactivity and conformation fluctuation of the major beech pollen allergen Fag s 1

Fag s 1 is a member of the Pathogen Related protein family 10 (PR-10) and can elicit cross-reaction with IgE antibodies produced against the birch pollen allergen Bet v 1. The Nuclear Magnetic Resonance (NMR) structure of Fag s 1 is presented along with its dynamic properties. It shares 66% identity with Bet v 1 and exhibits the expected three α-helices and seven β-sheets arranged as a semi-beta barrel and exposing the residues mapped as the Bet v 1 IgE epitope. The structural dynamics of Fag s 1 were monitored on the fast and intermediate timescales, using relaxation rates. The complex dynamics of Fag s 1 are closely related to the internal cavity, and they modulate IgE and ligand binding.

Characterization and epitope mapping of Dengue virus type 1 specific monoclonal antibodies

BACKGROUND

Dengue virus (DV) infection causes a spectrum of clinical diseases ranging from dengue fever to a life-threatening dengue hemorrhagic fever. Four distinct serotypes (DV1-4), which have similar genome sequences and envelope protein (E protein) antigenic properties, were divided. Among these 4 serotypes, DV1 usually causes predominant infections and fast diagnosis and effective treatments are urgently required to prevent further hospitalization and casualties.

METHODS

To develop antibodies specifically targeting and neutralizing DV1, we immunized mice with UV-inactivated DV1 viral particles and recombinant DV1 E protein from residue 1 to 395 (E395), and then generated 12 anti-E monoclonal antibodies (mAbs) as the candidates for a series of characterized assays such as ELISA, dot blot, immunofluorescence assay, western blot, and foci forming analyses.

RESULTS

Among the mAbs, 10 out of 12 showed cross-reactivity to four DV serotypes as well as Japanese encephalitis virus (JEV) in different cross-reactivity patterns. Two particular mAbs, DV1-E1 and DV1-E2, exhibited strong binding specificity and neutralizing activity against DV1 and showed no cross-reactivity to DV2, DV3, DV4 or JEV-infected cells as characterized by ELISA, dot blot, immunofluorescence assay, western blot, and foci forming analyses. Using peptide coated indirect ELISA, we localized the neutralizing determinants of the strongly inhibitory mAbs to a sequence-unique epitope on the later-ridge of domain III of the DV1 E protein, centered near residues T346 and D360 (346TQNGRLITANPIVTD360). Interestingly, the amino acid sequence of the epitope region is highly conserved among different genotypes of DV1 but diverse from DV2, DV3, DV4 serotypes and other flaviviruses.

CONCLUSIONS

Our results showed two selected mAbs DV1-E1 and DV1-E2 can specifically target and significantly neutralize DV1. With further research these two mAbs might be applied in the development of DV1 specific serologic diagnosis and used as a feasible treatment option for DV1 infection. The identification of DV1 mAbs epitope with key residues can also provide vital information for vaccine design.

Meta-Analysis of Dengue Severity during Infection by Different Dengue Virus Serotypes in Primary and Secondary Infections

INTRODUCTION

Dengue virus (DENV) infection is currently a major cause of morbidity and mortality in the world; it has become more common and virulent over the past half-century and has gained much attention. Thus, this review compared the percentage of severe cases of both primary and secondary infections with different serotypes of dengue virus.

METHODS

Data related to the number of cases involving dengue fever (DF), dengue hemorrhagic fever (DHF), dengue shock syndrome (DSS) or severe dengue infections caused by different serotypes of dengue virus were obtained by using the SCOPUS, the PUBMED and the OVID search engines with the keywords "(dengue* OR dengue virus*) AND (severe dengue* OR severity of illness index* OR severity* OR DF* OR DHF* OR DSS*) AND (serotypes* OR serogroup*)", according to the MESH terms suggested by PUBMED and OVID.

RESULTS

Approximately 31 studies encompassing 15,741 cases reporting on the dengue serotypes together with their severity were obtained, and meta-analysis was carried out to analyze the data. This study found that DENV-3 from the Southeast Asia (SEA) region displayed the greatest percentage of severe cases in primary infection (95% confidence interval (CI), 31.22-53.67, 9 studies, n = 598, I2 = 71.53%), whereas DENV-2, DENV-3, and DENV-4 from the SEA region, as well as DENV-2 and DENV-3 from non-SEA regions, exhibited the greatest percentage of severe cases in secondary infection (95% CI, 11.64-80.89, 4-14 studies, n = 668-3,149, I2 = 14.77-96.20%). Moreover, DENV-2 and DENV-4 from the SEA region had been found to be more highly associated with dengue shock syndrome (DSS) (95% CI, 10.47-40.24, 5-8 studies, n = 642-2,530, I2 = 76.93-97.70%), while DENV-3 and DENV-4 from the SEA region were found to be more highly associated with dengue hemorrhagic fever (DHF) (95% CI, 31.86-54.58, 9 studies, n = 674-2,278, I2 = 55.74-88.47%), according to the 1997 WHO dengue classification. Finally, DENV-2 and DENV-4 from the SEA region were discovered to be more highly associated with secondary infection compared to other serotypes (95% CI, 72.01-96.32, 9-12 studies, n = 671-2,863, I2 = 25.01-96.75%).

CONCLUSION

This study provides evidence that the presence of certain serotypes, including primary infection with DENV-3 from the SEA region and secondary infection with DENV-2, DENV-3, and DENV-4 also from the SEA region, as well as DENV-2 and DENV-3 from non SEA regions, increased the risk of severe dengue infections. Thus, these serotypes are worthy of special consideration when making clinical predictions upon the severity of the infection.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42015026093 (http://www.crd.york.ac.uk/PROSPERO).

Antibody Binding Modulates Conformational Exchange in Domain III of Dengue Virus E Protein

Domain III of dengue virus E protein (DIII) participates in the recognition of cell receptors and in structural rearrangements required for membrane fusion and ultimately viral infection; furthermore, it contains epitopes for neutralizing antibodies and has been considered a potential vaccination agent. In this work, we addressed various structural aspects of DIII and their relevance for both the dengue virus infection mechanism and antibody recognition. We provided a dynamic description of DIII at physiological and endosomal pHs and in complex with the neutralizing human antibody DV32.6. We observed conformational exchange in the isolated DIII, in regions important for the packing of E protein dimers on the virus surface. This conformational diversity is likely to facilitate the partial detachment of DIII from the other E protein domains, which is required to achieve fusion to the host cellular membranes and to expose the epitopes of many anti-DIII antibodies. A comparison of DIII of two dengue virus serotypes revealed many common features but also some possibly unexpected differences. Antibody binding to DIII of dengue virus serotype 4 attenuated the conformational exchange in the epitope region but, surprisingly, generated exchange in other parts of DIII through allosteric effects.

IMPORTANCE

Many studies have provided extensive structural information on the E protein and particularly on DIII, also in complex with antibodies. However, there is very scarce information regarding the molecular dynamics of DIII, and almost nothing is available on the dynamic effect of antibody binding, especially at the quantitative level. This work provides one of the very rare descriptions of the effect of antibody binding on antigen dynamics.

Comprehensive mapping of functional epitopes on dengue virus glycoprotein E DIII for binding to broadly neutralizing antibodies 4E11 and 4E5A by phage display

Here we investigated the binding of Dengue virus envelope glycoprotein domain III (DIII) by two broadly neutralizing antibodies (bNAbs), 4E11 and 4E5A. There are four serotypes of Dengue virus (DENV-1 to -4), whose DIII sequences vary by up to 49%. We used combinatorial alanine scanning mutagenesis, a phage display approach, to map functional epitopes (those residues that contribute most significantly to the energetics of antibody-antigen interaction) on these four serotypes. Our results showed that 4E11, which binds strongly to DENV-1, -2, and -3, and moderately to DENV-4, recognized a common conserved core functional epitope involving DIII residues K310, L/I387, L389, and W391. There were also unique recognition features for each serotype, suggesting that 4E11 has flexible recognition requirements. Similar scanning studies for the related bNAb 4E5A, which binds more tightly to DENV-4, identified broader functional epitopes on DENV-1. These results provide useful information for immunogen and therapeutic antibody design.