Cross-reacting antibodies enhance dengue virus infection in humans

Heteropsine inhibits dengue virus infection, suppresses cytokine/chemokine gene expressions, and attenuates nuclear translocation of nuclear factor-kappaB in liver cell lines

Dengue virus (DENV) infection remains a major global health threat. Its incidence is increasing, with frequent outbreaks affecting millions of people each year. Although vaccines are available, their limited effectiveness and the absence of targeted antiviral therapies highlight the critical need for alternative treatment approaches. In this study, we investigated the antiviral activity of bidebiline A and heteropsine, two dimeric aporphine alkaloids isolated from Trivalvaria costata, against DENV-infected Huh7 liver cells. Our findings reveal that heteropsine inhibits DENV production and infection in Huh7 cells more effectively than bidebiline A. Heteropsine also exerts antiviral activity in endothelial and lung cell lines. Mechanistic studies, including time-of-addition assays and molecular docking, elucidate that heteropsine targets early steps during cellular infection, possibly by binding to domain III of the dengue virus envelope protein (EDIII). Viral binding and internalization assays confirmed that heteropsine disrupts viral entry. Furthermore, heteropsine suppresses DENV-induced immunopathogenesis by downregulating the expression of cytokine/chemokine genes (TNF-α, IL-6, RANTES, and IP-10) and attenuating nuclear translocation of the p65 subunit of the nuclear factor-kappaB (NF-κB) transcription factor. These findings highlight the importance of heteropsine as a promising antiviral candidate with the potential for further development to address the urgent need for effective dengue therapeutics.

Multivalent administration of dengue E dimers on liposomes elicits type-specific neutralizing responses without immune interference

The four serotypes of dengue virus (DENV1-4) are a major health concern putting 50% of the global population at risk of infection. Crucially, DENV vaccines must be tetravalent to provide protection against all four serotypes because immunity to only one serotype can enhance infections caused by heterologous serotypes. Uneven replication of live-attenuated viruses in tetravalent vaccines can lead to disease enhancement instead of protection. Subunit vaccines are a promising alternative as the vaccine components are not dependent on viral replication and antigen doses can be controlled to achieve a balanced response. Here, we show that a tetravalent subunit vaccine of dengue envelope (E) proteins computationally stabilized to form native-like dimers elicits type-specific neutralizing antibodies in mice against all four serotypes. The immune response was enhanced by displaying the E dimers on liposomes embedded with adjuvant, and no interference was detected between the four components.

Toward a deeper understanding of dengue: novel method for quantification and isolation of envelope protein epitope-specific antibodies

The dengue viruses (DENV) envelope (E) protein is the main target of the antibody (Ab) response. Abs target different epitopes on the E-protein, including sE-dimer, E domain III (EDIII), and fusion loop (FL). Anti-EDIII Abs are mainly serotype-specific, whereas anti-FL Abs can induce antibody-dependent enhancement (ADE) in vitro. Abs targeting sE-dimer epitopes can cross-neutralize different DENV serotypes. However, the involvement of each Ab subset in disease pathogenicity and/or protection remains unclear. We aimed to optimize the quantification and purification of DENV E-protein epitope-specific Abs from human samples. C-terminal biotinylated DENV2 E recombinant proteins (EDIII, soluble E [sE], and sE-dimer) were coupled to color-coded magnetic microspheres for a multiplex immunoassay (MIA), testing different antigen concentrations. Assay performance was evaluated using well-characterized anti-DENV monoclonal antibodies (mAbs) and total IgG from DENV seronegative and seropositive human plasma. Specific FL epitopes were blocked with mouse mAb clone 4G2 to quantify anti-FL- and sE-dimer-specific Abs, measuring antigen-antibody reactions as median fluorescence intensity (MFI). For isolation of E-protein epitope-specific antibodies, sE-proteins were conjugated to streptavidin resin beads. Total IgG from human plasma was incubated with immobilized EDIII to elute anti-EDIII Abs. The flow-through was incubated with sE-dimer resin beads to elute sE-dimer specific Ab enriched fraction, and the flow-through was applied to immobilized sE to elute anti-FL Abs. In conclusion, we have developed a serological assay to detect E-protein epitope-specific Abs in DENV-infected humans. Additionally, we successfully isolated anti-EDIII, anti-FL, and an enriched fraction of sE-dimer specific Abs from human samples.IMPORTANCEThe development of effective dengue virus (DENV) vaccines has been hampered by limited insights into the immunological mechanisms of protection. Our study addresses this gap by introducing a refined multiplex microsphere-based immunoassay (MIA) to quantify and isolate antibodies (Abs) targeting specific E-protein epitopes, such as E domain III (EDIII), the fusion loop (FL), and the sE-dimer specific Abs. This method provides detailed epitope-specific Ab profiling with high sensitivity and requires minimal sample volumes. The ability to isolate specific Ab subsets from human plasma also enables detailed investigations into their roles in protection or pathogenesis, paving the way for more effective dengue interventions.

Development of New Live-Attenuated Vaccine Candidates Lacking Antibody-Dependent Enhancement (ADE) Against Dengue

Dengue virus (DENV) threatens public health, especially in regions with tropical and subtropical climates. In 2024, the World Health Organisation reported 3.4 million confirmed dengue cases, with 16,000 severe cases and 3000 dengue-associated fatalities. The first licensed dengue vaccine, CYD-TDV (Dengvaxia®,Sanofi-Pasteur, Paris, France), is recommended by the WHO only for individuals aged 9-45 years with a prior history of dengue infection. However, being vaccinated with Dengvaxia® increases the risk of developing severe dengue infections in seronegative individuals. Recently, a second licensed dengue vaccine, Qdenga®,Takeda, Singen, Germany), was approved and recommended by the WHO to be administered only in highly dengue-endemic countries, as it was not shown to elicit a robust immune response against DENV-3 and DENV-4 serotypes in dengue seronegative individuals. Due to an imbalance in immune response against all four DENV serotypes, there is a higher risk of developing the antibody-dependent enhancement (ADE) effect, which could lead to severe dengue. This review has identified mutations throughout the DENV genome that were demonstrated to attenuate the virulence of DENV in either in vitro or in vivo studies. Several amino acid residues within the DENV prM and E proteins were identified to play important roles in ADE and modifying these ADE-linked residues is important in the rational design of novel live-attenuated dengue vaccine candidates. This review provides current insights to guide the development of a novel live-attenuated tetravalent dengue vaccine candidate that is effective against all DENV serotypes and safe from ADE. The efficacy and safety of the live-attenuated vaccine candidate should be further validated in in vivo studies.

From Antibodies to Immunity: Assessing Correlates of Flavivirus Protection and Cross-Reactivity

Flaviviruses are arthropod-borne RNA viruses that can cause a wide range of human diseases, from mild symptoms to severe illness with multiorgan failure and death. Effective prevention of these diseases relies on identifying reliable vaccine targets, typically measured by correlates of protection (CoPs), which help indicate host immunity after vaccination. Current vaccines primarily focus on neutralizing antibodies (nAbs) against the viral envelope E protein, though emerging evidence suggests other potential targets may also be effective in disease prevention. Additionally, there is growing evidence of cross-protection between different flaviviruses when immunity to one virus is achieved, although this can be limited by antibody-dependent enhancement. This review examines the current understanding of flavivirus immunity, CoPs, and the potential for cross-protection in the context of existing vaccine strategies.

Spatiotemporal dispersion of DENV-1 genotype V in Western Colombia

Dengue virus (DENV) is a significant public health concern in Colombia, with increased transmission of DENV type 1 (DENV-1) in the departments of Risaralda and Valle del Cauca in the Central-West region of the country following a large outbreak in 2019. However, little is known about the source, genetic diversity, and evolution of circulating viruses. We obtained serum samples from individuals with acute DENV infection and analysed DENV-1 genetic diversity, phylodynamics, and phylogeography. We found that most viruses belonged to DENV-1 genotype V, and phylogenetic analysis revealed three distinct clades, each of which was most closely related to viruses from neighbouring departments of Colombia sampled over the last 5-10 years. Thus, the 2019 outbreak and subsequent DENV-1 circulation was not due to the introduction of a new lineage to the country but rather reflected local DENV-1 V dispersion and evolution. We identified amino acid positions under positive selection in structural proteins and NS1, which may have a role in immune evasion and pathogenesis. Overall, our analysis of DENV-1 V diversity, evolution, and spread within Colombia highlights the important role of genomic surveillance in understanding virus dynamics during endemic circulation and outbreaks.

Immunological drivers of zoonotic virus emergence, evolution, and endemicity

The disruption of natural ecosystems caused by climate change and human activity is amplifying the risk of zoonotic spillover, presenting a growing global health threat. In the past two decades, the emergence of multiple zoonotic viruses has exposed critical gaps in our ability to predict epidemic trajectories and implement effective interventions. RNA viruses, in particular, are challenging to control due to their high mutation rates and ability to adapt and evade immune defenses. To better prepare for future outbreaks, it is vital that we deepen our understanding of the factors driving viral emergence, transmission, and persistence in human populations. Specifically, deciphering the interactions between antibody-mediated immunity and viral evolution will be key. In this perspective, we explore these dynamic relationships and highlight research priorities that may guide the development of more effective strategies to mitigate the impact of emerging infectious diseases.

Dengue virus non-structural protein 1 binding to thrombin as a dengue severity marker: Comprehensive patient analysis in south Taiwan

BACKGROUND

Previously we identified a complex of non-structural protein (NS) 1 - Thrombin (NST) in dengue infected patients. Here, we investigated how the concentration of NS1 and NST differ in various dengue severity levels as well as their demographic and clinical features. Several comorbid (hypertension, diabetes, and chronic renal failure) often found in dengue patients were also measured and analyzed.

METHODS

A total of 86 dengue patients (52 not severe and 34 severe), were enrolled and had their blood taken. Blood samples were further verified for clinical blood parameters, including liver and renal function tests and serologic assays (NS1 and NST). Patients' severity was grouped based on WHO 2009 classification, which separates patients into dengue without warning signs (DNWS), dengue with warning signs (DWWS), and severe dengue (SD). DWWS is explained as DNWS with warning signs (persistent abdominal pain, persistent vomiting, liver enlargement, bleeding (any kind), fatigue, and restlessness). SD are those with severe plasma leakage, severe bleeding, or severe organ impairment. Multivariate regression analysis was used to predict the role of NST on the dengue severity development and receiver operating characteristic (AUROC) test was utilized to evaluate separability.

RESULTS

The analysis revealed that NS1 significantly impacts the disease outcome (p 0.018, OR = 2.467 (1.171-5.197)) but not beyond the effect through NST (p 0.108, OR = 0.085 (0.004-1.719)). We also prove that NST was a better severity biomarker compared to NS1, as it can predict progression from DNWS to DWWS (AUC: NS1 = 0.771∗∗, NST = 0.81∗∗) and SD (AUC: NS1 = 0.607, NST = 0.754∗) significantly.

CONCLUSIONS

This finding suggests the importance of NST in mediating the NS1 effect to promote dengue severity progression and its promising capability as an acute stage dengue severity biomarker.

Distinct features of a peripheral T helper subset that drives the B cell response in dengue virus infection

Dengue-virus-induced humoral immunity can increase the risk of severe disease, but the factors influencing this response are poorly understood. Here, we investigate the contribution of CD4+ T cells to B cell responses in human dengue infection. We identify a dominant peripheral PD-1+ T cell subset that accumulates in severe patients and could induce B cell differentiation via interleukin-21 (IL-21)-related pathway. Single-cell analyses reveal heterogeneity within PD-1+ cells, demonstrating the coexistence of subsets with "helper" (IL-21+) or "cytotoxic" characteristics. The IL-21+ subset displays a distinct clonotypic and transcriptomic signature compared to follicular helper T cells and persists as a memory in lymph nodes. Notably, we show that the IL-21+ subset seems to majorly drive the extrafollicular B cell responses in dengue. Our study establishes the peripheral IL-21+ subset as a potential determinant of the humoral response to dengue virus infection. These findings provide important insights into the T-cell-dependent regulation of humoral responses and can inform the design of effective dengue vaccines.

Development of nucleic acid-based vaccines against dengue and other mosquito-borne flaviviruses: the past, present, and future

Due to their widespread geographic distribution and frequent outbreaks, mosquito-borne flaviviruses, such as DENV (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV), yellow fever virus (YFV), and West Nile virus (WNV), are considered significant global public health threats and contribute to dramatic socioeconomic imbalances worldwide. The global prevalence of these viruses is largely driven by extensive international travels and ecological disruptions that create favorable conditions for the breeding of Aedes and Culex species, the mosquito vectors responsible for the spread of these pathogens. Currently, vaccines are available for only DENV, YFV, and JEV, but these face several challenges, including safety concerns, lengthy production processes, and logistical difficulties in distribution, especially in resource-limited regions, highlighting the urgent need for innovative vaccine approaches. Nucleic acid-based platforms, including DNA and mRNA vaccines, have emerged as promising alternatives due to their ability to elicit strong immune responses, facilitate rapid development, and support scalable manufacturing. This review provides a comprehensive update on the progress of DNA and mRNA vaccine development against mosquito-borne flaviviruses, detailing early efforts and current strategies that have produced candidates with remarkable protective efficacy and strong immunogenicity in preclinical models. Furthermore, we explore future directions for advancing nucleic acid vaccine candidates, which hold transformative potential for enhancing global public health.

Current status of the development of dengue vaccines

Dengue fever is caused by the mosquito-borne dengue virus (DENV), which is endemic in more than 100 countries. Annually, there are approximately 390 million dengue cases, with a small subset manifesting into severe illnesses, such as dengue haemorrhagic fever or dengue shock syndrome. Current treatment options for dengue infections remain supportive management due to the lack of an effective vaccine and clinically approved antiviral. Although the CYD-TDV (Dengvaxia®) vaccine with an overall vaccine efficacy of 60 % has been licensed for clinical use since 2015, it poses an elevated risk of severe dengue infections especially in dengue-naïve children below 9 years of age. The newly approved Qdenga vaccine was able to achieve an overall vaccine efficacy of 80 % after 12 months, but it was not able to provide a protective effect against DENV-3 in dengue naïve individuals. The Butantan-DV vaccine candidate is still undergoing phase 3 clinical trials for safety and efficacy evaluations in humans. Apart from live-attenuated vaccines, various other vaccine types are also currently being studied in preclinical and clinical studies. This review discusses the current status of dengue vaccine development.

Prognostic factors in severe dengue patients: A multi-center retrospective cohort study

BACKGROUND/PURPOSE

Early detection of severe dengue (SD) and appropriate management are crucial in reducing the case fatality rate. The objective of this study was to investigate the clinical characteristics of SD and identify independent risk factors associated with mortality among SD patients.

METHODS

A retrospective study was conducted at two medical center hospitals between 2002 and 2019, involving patients aged ≧18 years with laboratory-confirmed SD.

RESULTS

This study included 294 patients with SD, of whom 203 (69%) survived and 91 (31%) died. Among the 294 SD patients, 103 (35%) experienced acute kidney injury, 54 (18.4%) had pneumonia, and 19 (6.5%) had bacteremia. Among the 286 patients with available alanine aminotransferase (ALT) data, 41 (14.3%) experienced severe hepatitis (ALT>1000U/L). The median time from illness onset to death among the 91 SD patients who died was 5 days. Multivariable regression analysis revealed increasing odds of death associated with older age (odds ratio [OR], 1.037; 95% confidence interval [CI], 1.009-1.066), altered consciousness (OR, 8.591; 95% CI, 2.914-25.330), gastrointestinal bleeding (OR, 1.939; 95% CI, 1.037-3.626), and leukocytosis (OR, 2.504; 95% CI, 1.124-5.578) upon arrival, as well as organ impairment during hospitalization, including acute kidney injury (OR, 2.627; 95% CI, 1.373-5.028), severe hepatitis (OR, 5.324; 95% CI, 2.199-12.889), and pneumonia (OR, 2.250; 95% CI, 1.054-4.802).

CONCLUSIONS

Our findings underscore the importance of early recognition and intervention by frontline physicians in identifying SD patients at high risk of mortality. This information can significantly contribute to reducing fatalities and improving the overall management of SD cases.

A low pre-existing anti-NS1 humoral immunity to DENV is associated with microcephaly development after gestational ZIKV exposure

BACKGROUND

Gestational Zika virus (ZIKV) infection is associated with the development of congenital Zika syndrome (CZS), which includes microcephaly and fetal demise. The magnitude and quality of orthoflavivirus-specific humoral immunity have been previously linked to the development of CZS. However, the role of ZIKV NS1-specific humoral immunity in mothers and children with prenatal ZIKV exposure and CZS remains undefined. In addition, considering that most of the at-risk population lives in dengue virus (DENV)-endemic areas, it is not clear what is the association between pre-existing DENV NS1-specific humoral immunity and CZS.

METHODS

Here, we studied 328 mothers and children with a clinical diagnosis and seropositivity for ZIKV infection during pregnancy, included during the 2015-2016 ZIKV epidemic in Colombia. We also performed clinical evaluation and pediatric neurological follow-up. The relative levels of circulating NS1-specific IgM and IgG against ZIKV and DENV were evaluated in mothers and children, and the association with the development of microcephaly was analyzed.

RESULTS

DENV and ZIKV IgG-NS1 antibodies in pregnant women were placentally transferred, and this passage and its duration in children depended on the maternal levels of the antibodies. We reported that higher concentrations of pre-existing DENV, but not ZIKV IgG-NS1 antibodies, were associated with a reduced risk of CZS-related microcephaly. Also, we observed that the IgM-NS1 response in infants is long-term and has a minor association with poor outcomes.

CONCLUSIONS

The development of microcephaly in children prenatally exposed to ZIKV is associated with low plasma levels of placentally transferred, pre-existing DENV IgG-NS1 antibodies. These data are compatible with a protective role of anti-NS1 IgG antibodies against ZIKV infection during pregnancy and highlight the promising role of NS1 as an orthoflavivirus vaccine target in high-risk populations.

Deep immunoglobulin repertoire sequencing depicts a comprehensive atlas of spike-specific antibody lineages shared among COVID-19 convalescents

Neutralizing antibodies are a key component in protective humoral immunity against SARS-CoV-2. Currently, available technologies cannot track epitope-specific antibodies in global antibody repertoires. Thus, the comprehensive repertoire of spike-specific neutralizing antibodies elicited by SARS-CoV-2 infection is not fully understood. We therefore combined high-throughput immunoglobulin heavy chain (IgH) repertoire sequencing, and structural and bioinformatics analysis to establish an antibodyomics pipeline, which enables tracking spike-specific antibody lineages that target certain neutralizing epitopes. We mapped the neutralizing epitopes on the spike and determined the epitope-preferential antibody lineages. This analysis also revealed numerous overlaps between immunodominant neutralizing antibody-binding sites and mutation hotspots on spikes as observed so far in SARS-CoV-2 variants. By clustering 2677 spike-specific antibodies with 360 million IgH sequences that we sequenced, a total of 329 shared spike-specific antibody clonotypes were identified from 33 COVID-19 convalescents and 24 SARS-CoV-2-naïve individuals. Epitope mapping showed that the shared antibody responses target not only neutralizing epitopes on RBD and NTD but also non-neutralizing epitopes on S2. The immunodominance of neutralizing antibody response is determined by the occurrence of specific precursors in human naïve B-cell repertoires. We identified that only 28 out of the 329 shared spike-specific antibody clonotypes persisted for at least 12 months. Among them, long-lived IGHV3-53 antibodies are likely to evolve cross-reactivity to Omicron variants through accumulating somatic hypermutations. Altogether, we created a comprehensive atlas of spike-targeting antibody lineages in COVID-19 convalescents and antibody precursors in human naïve B cell repertoires, providing a valuable reference for future vaccine design and evaluation.

Efficacy of genotype-matched vaccine against re-emerging genotype V Japanese encephalitis virus

Japanese encephalitis (JE), caused by the Japanese encephalitis virus (JEV), is a highly threatening disease with no specific treatment. Fortunately, the development of vaccines has enabled effective defense against JE. However, re-emerging genotype V (GV) JEV poses a challenge as current vaccines are genotype III (GIII)-based and provide suboptimal protection. Given the isolation of GV JEVs from Malaysia, China, and the Republic of Korea, there is a concern about the potential for a broader outbreak. Under the hypothesis that a GV-based vaccine is necessary for effective defense against GV JEV, we developed a pentameric recombinant antigen using cholera toxin B as a scaffold and mucosal adjuvant, which was conjugated with the E protein domain III of GV by genetic fusion. This GV-based vaccine antigen induced a more effective immune response in mice against GV JEV isolates compared to GIII-based antigen and efficiently protected animals from lethal challenges. Furthermore, a bivalent vaccine approach, inoculating simultaneously with GIII- and GV-based antigens, showed protective efficacy against both GIII and GV JEVs. This strategy presents a promising avenue for comprehensive protection in regions facing the threat of diverse JEV genotypes, including both prevalent GIII and GI as well as emerging GV strains.

Predicting the infecting dengue serotype from antibody titre data using machine learning

The development of a safe and efficacious vaccine that provides immunity against all four dengue virus serotypes is a priority, and a significant challenge for vaccine development has been defining and measuring serotype-specific outcomes and correlates of protection. The plaque reduction neutralisation test (PRNT) is the gold standard assay for measuring serotype-specific antibodies, but this test cannot differentiate homotypic and heterotypic antibodies and characterising the infection history is challenging. To address this, we present an analysis of pre- and post-infection antibody titres measured using the PRNT, collected from a prospective cohort of Thai children. We applied four machine learning classifiers and multinomial logistic regression to the titre data to predict the infecting serotype. The models were validated against the true infecting serotype, identified using RT-PCR. Model performance was calculated using 100 bootstrap samples of the train and out-of-sample test sets. Our analysis showed that, on average, the greatest change in titre was against the infecting serotype. However, in 53.4% (109/204) of the subjects, the highest titre change did not correspond to the infecting serotype, including in 34.3% (11/35) of dengue-naïve individuals (although 8/11 of these seronegative individuals were seropositive to Japanese encephalitis virus prior to their infection). The highest post-infection titres of seropositive cases were more likely to match the serotype of the highest pre-infection titre than the infecting serotype, consistent with antigenic seniority or cross-reactive boosting of pre-infection titres. Despite these challenges, the best performing machine learning algorithm achieved 76.3% (95% CI 57.9-89.5%) accuracy on the out-of-sample test set in predicting the infecting serotype from PRNT data. Incorporating additional spatiotemporal data improved accuracy to 80.6% (95% CI 63.2-94.7%), while using only post-infection titres as predictor variables yielded an accuracy of 71.7% (95% CI 57.9-84.2%). These results show that machine learning classifiers can be used to overcome challenges in interpreting PRNT titres, making them useful tools in investigating dengue immune dynamics, infection history and identifying serotype-specific correlates of protection, which in turn can support the evaluation of clinical trial endpoints and vaccine development.

Protective Role of NS1-Specific Antibodies in the Immune Response to Dengue Virus Through Antibody-Dependent Cellular Cytotoxicity

BACKGROUND

Dengue virus (DENV) nonstructural protein 1 (NS1) has multiple functions within infected cells, on the cell surface, and in secreted form, and is highly immunogenic. Immunity from previous DENV infections is known to exert both positive and negative effects on subsequent DENV infections, but the contribution of NS1-specific antibodies to these effects is incompletely understood.

METHODS

We investigated the functions of NS1-specific antibodies and their significance in DENV infection. We analyzed plasma samples collected in a prospective cohort study prior to symptomatic or subclinical secondary DENV infection. We measured binding to purified recombinant NS1 protein and to NS1-expressing CEM cells, antibody-mediated natural killer (NK) cell activation by plate-bound NS1 protein, and antibody-dependent cellular cytotoxicity (ADCC) of NS1-expressing target cells.

RESULTS

We found that antibody responses to NS1 were highly serotype cross-reactive and that subjects who experienced subclinical DENV infection had significantly higher antibody responses to NS1 in preinfection plasma than subjects who experienced symptomatic infection. We observed strong positive correlations between antibody binding and NK activation.

CONCLUSIONS

These findings demonstrate the involvement of NS1-specific antibodies in ADCC and provide evidence for a protective effect of NS1-specific antibodies in secondary DENV infection.

The role of antibody-dependent enhancement in dengue vaccination

Dengue is the most rapidly spreading vector-borne disease worldwide, with over half the global population at risk for an infection. Antibody-dependent enhancement (ADE) is associated with increased disease severity and may also be attributable to the deterioration of disease in vaccinated people. Two dengue vaccines are approved momentarily, with more in development. The increasing use of vaccines against dengue, combined with the development of more, makes a thorough understanding of the processes behind ADE more important than ever. Above that, due to the lack of treatment options, this method of prevention is of great importance. This review aims to explore the impact of ADE in dengue vaccinations, with the goal of enhancing potential vaccination strategies in the fight against dengue.

Fc-FcγR interactions during infections: From neutralizing antibodies to antibody-dependent enhancement

Advances in antibody technologies have resulted in the development of potent antibody-based therapeutics with proven clinical efficacy against infectious diseases. Several monoclonal antibodies (mAbs), mainly against viruses such as SARS-CoV-2, HIV-1, Ebola virus, influenza virus, and hepatitis B virus, are currently undergoing clinical testing or are already in use. Although these mAbs exhibit potent neutralizing activity that effectively blocks host cell infection, their antiviral activity results not only from Fab-mediated virus neutralization, but also from the protective effector functions mediated through the interaction of their Fc domains with Fcγ receptors (FcγRs) on effector leukocytes. Fc-FcγR interactions confer pleiotropic protective activities, including the clearance of opsonized virions and infected cells, as well as the induction of antiviral T-cell responses. However, excessive or inappropriate activation of specific FcγR pathways can lead to disease enhancement and exacerbated pathology, as seen in the context of dengue virus infections. A comprehensive understanding of the diversity of Fc effector functions during infection has guided the development of engineered antiviral antibodies optimized for maximal effector activity, as well as the design of targeted therapeutic approaches to prevent antibody-dependent enhancement of disease.

An update on the ocular manifestations of dengue

Dengue is the most common arboviral disease. It is typically spread by the bite of an infected female Aedes aegypti or Aedes albopictus mosquitoes. Dengue is endemic in subtropical and tropical regions, but its geographic reach keeps expanding. Ophthalmic manifestations of dengue are common and may present with a wide spectrum of ophthalmic findings. These may range from conjunctival petechiae, retinal hemorrhage, retinal vasculitis to panophthalmitis. Some of these may be vision threatening and may require urgent ophthalmic evaluation. The precise pathophysiologic mechanisms involved in dengue infection involve a complex interplay between host immune responses, virus, and host genes. There is no specific treatment for ocular dengue. Therefore, treatment is supportive. Despite the lack of proven efficacy, corticosteroids have been used in vision-threatening dengue-related ocular complications. Dengue must be considered in endemic areas, and a careful travel history needs to be elicited in nonendemic areas.

7D, a small molecule inhibits dengue infection by increasing interferons and neutralizing-antibodies via CXCL4:CXCR3:p38:IRF3 and Sirt1:STAT3 axes respectively

There are a limited number of effective vaccines against dengue virus (DENV) and significant efforts are being made to develop potent anti-virals. Previously, we described that platelet-chemokine CXCL4 negatively regulates interferon (IFN)-α/β synthesis and promotes DENV2 replication. An antagonist to CXCR3 (CXCL4 receptor) reversed it and inhibited viral replication. In a concurrent search, we identified CXCR3-antagonist from our compound library, namely 7D, which inhibited all serotypes of DENV in vitro. With a half-life of ~2.85 h in plasma and no significant toxicity, 7D supplementation (8 mg/kg-body-weight) to DENV2-infected IFNα/β/γR-/-AG129 or wild-type C57BL6 mice increased synthesis of IFN-α/β and IFN-λ, and rescued disease symptoms like thrombocytopenia, leukopenia and vascular-leakage, with improved survival. 7D, having the property to inhibit Sirt-1 deacetylase, promoted acetylation and phosphorylation of STAT3, which in-turn increased plasmablast proliferation, germinal-center maturation and synthesis of neutralizing-antibodies against DENV2 in mice. A STAT3-inhibitor successfully inhibited these effects of 7D. Together, these observations identify compound 7D as a stimulator of IFN-α/β/λ synthesis via CXCL4:CXCR3:p38:IRF3 signaling, and a booster for neutralizing-antibody generation by promoting STAT3-acetylation in plasmablasts, capable of protecting dengue infection.

Preclinical Development of a Novel Zika Virus-like Particle Vaccine in Combination with Tetravalent Dengue Virus-like Particle Vaccines

Declared as a Public Health Emergency in 2016 by the World Health Organization (WHO), the Zika virus (ZIKV) continues to cause outbreaks that are linked to increased neurological complications. Transmitted mainly by Aedes mosquitoes, the virus is spread mostly amongst several tropical regions with the potential of territorial expansion due to environmental and ecological changes. The ZIKV envelope protein's domain III, crucial for vaccine development due to its role in receptor binding and neutralizing antibody targeting, was integrated into sterically optimized AP205 VLPs to create an EDIII-based VLP vaccine. To increase the potential size of domains that can be accommodated by AP205, two AP205 monomers were fused into a dimer, resulting in 90 rather than 180 N-/C- termini amenable for fusion. EDIII displayed on AP205 VLPs has several immunological advantages, like a repetitive surface, a size of 20-200 nm (another PASP), and packaged bacterial RNA as adjuvants (a natural toll-like receptor 7/8 ligand). In this study, we evaluated a novel vaccine candidate for safety and immunogenicity in mice, demonstrating its ability to induce high-affinity, ZIKV-neutralizing antibodies without significant disease-enhancing properties. Due to the close genetical and structural characteristics, the same mosquito vectors, and the same ecological niche of the dengue virus and Zika virus, a vaccine covering all four Dengue viruses (DENV) serotypes as well as ZIKV would be of significant interest. We co-formulated the ZIKV vaccine with recently developed DENV vaccines based on the same AP205 VLP platform and tested the vaccine mix in a murine model. This combinatory vaccine effectively induced a strong humoral immune response and neutralized all five targeted viruses after two doses, with no significant antibody-dependent enhancement (ADE) observed. Overall, these findings highlight the potential of the AP205 VLP-based combinatory vaccine as a promising approach for providing broad protection against DENV and ZIKV infections. Further investigations and preclinical studies are required to advance this vaccine candidate toward potential use in human populations.

pr-independent biogenesis of infectious mature Zika virus particles

Flavivirus assembly at the endoplasmic reticulum is driven by the structural proteins envelope (E) and premembrane (prM). Here, contrary to the established paradigm for flavivirus assembly, we demonstrate that the biogenesis of flavivirus particles does not require an intact prM nor proteolytic activation. The expression of E preceded by a truncated version of prM (M-E) was sufficient for the formation of non-infectious Zika virus subviral particles and pseudo-infectious reporter virions. Subviral particles encoded by a ZIKV M-E DNA vaccine elicited a neutralizing antibody response that was insensitive to the virion maturation state, a feature of flavivirus humoral immunity shown to correlate with protection. M-E vaccines that uniformly present structural features shared with mature virions offer a higher quality and broadly applicable approach to flavivirus vaccination.

Dengue virus: pathogenesis and potential for small molecule inhibitors

Dengue, caused by dengue virus (DENV), is now endemic in nearly 100 countries and infection incidence is reported in another 30 countries. Yearly an estimated 400 million cases and 2200 deaths are reported. Effective vaccines against DENV are limited and there has been significant focus on the development of effective antiviral against the disease. The World Health Organization has initiated research programs to prioritize the development and optimization of antiviral agents against several viruses including Flaviviridae. A significant effort has been taken by the researchers to develop effective antivirals against DENV. Several potential small-molecule inhibitors like efavirenz, tipranavir and dasabuvir have been tested against envelope and non-structural proteins of DENV, and are in clinical trials around the world. We recently developed one small molecule, namely 7D, targeting the host PF4-CXCR3 axis. 7D inhibited all 4 serotypes of DENV in vitro and specifically DENV2 infection in two different mice models. Although the development of dengue vaccines remains a high priority, antibody cross reactivity among the serotypes and resulting antibody-dependent enhancement (ADE) of infection are major concerns that have limited the development of effective vaccine against DENV. Therefore, there has been a significant emphasis on the development of antiviral drugs against dengue. This review article describes the rescue effects of some of the small molecule inhibitors to viral/host factors associated with DENV pathogenesis.

A Comprehensive Review on Porcine Reproductive and Respiratory Syndrome Virus with Emphasis on Immunity

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in pig production worldwide and responsible for enormous production and economic losses. PRRSV infection in gestating gilts and sows induces important reproductive failure. Additionally, respiratory distress is observed in infected piglets and fattening pigs, resulting in growth retardation and increased mortality. Importantly, PRRSV infection interferes with immunity in the respiratory tract, making PRRSV-infected pigs more susceptible to opportunistic secondary pathogens. Despite the availability of commercial PRRSV vaccines for more than three decades, control of the disease remains a frustrating and challenging task. This paper provides a comprehensive overview of PRRSV, covering its history, economic and scientific importance, and description of the viral structure and genetic diversity. It explores the virus's pathogenesis, including cell tropism, viral entry, replication, stages of infection and epidemiology. It reviews the porcine innate and adaptative immune responses to comprehend the modulation mechanisms employed by PRRS for immune evasion.

Dengue Hemorrhagic Fever in Quang Nam Province (Vietnam) from 2020 to 2022-A Study on Serotypes Distribution and Immunology Factors

Background: Dengue hemorrhagic fever (DHF) is the most prevalent and fastest-growing vector-borne disease globally, with symptoms ranging from mild to severe and, in some cases, fatal. Quang Nam province in Vietnam can serve as a model for dengue epidemiological study, as it is an endemic region for DHF with a tropical climate, which significantly constrains the health system. However, there are very few epidemiological and microbiological reports on Dengue virus (DENV) serotypes in this region due to the limited availability of advanced surveillance infrastructure. Aims of the study: This study aims to (1) assess the PCR positivity rates among hospitalized patients with clinical Dengue presentation; (2) identify the circulating DENV serotypes; and (3) assess the impact of secondary DENV infections on outbreak severity by detecting the presence of DENV-specific IgG antibodies in the plasma of DENV-infected patients. Materials and methods: Blood samples from patients clinically diagnosed with DHF and admitted to Quang Nam General Hospital (2020-2022) were analyzed. RNA extraction was performed using the NKDNA/RNAprep MAGBEAD kit, followed by Multiplex Reverse Transcription real-time Polymerase Chain Reaction (MLP RT-rPCR) for DENV detection and serotype identification. Positive samples were further tested for DENV-specific IgG antibodies using an enzyme-linked immunosorbent assay (ELISA). Results: The PCR positivity rate among hospitalized patients was approximately 68% throughout the study period. A significant shift in DENV serotypes was observed, with DENV-2 initially dominant and later giving way to DENV-1. IgG was detected in nearly half of the MPL RT-rPCR-positive samples, indicating secondary DENV infections. Conclusions: Our study highlights persistent dengue prevalence and dynamic shifts in DENV serotypes in Quang Nam province, emphasizing the need for improved diagnostic strategies and timely sample collection. The significant serotype shifts and the presence of IgG in hospitalized patients suggest potential severe outcomes from recurrent DENV infections, possibly linked to antibody-dependent enhancement (ADE) effect, underscoring the importance of advanced surveillance, vector control, vaccination campaigns, and public education to predict and prevent future DHF epidemics.

An Engineered N-Glycosylated Dengue Envelope Protein Domain III Facilitates Epitope-Directed Selection of Potently Neutralizing and Minimally Enhancing Antibodies

The envelope protein of dengue virus (DENV) is a primary target of the humoral immune response. The domain III of the DENV envelope protein (EDIII) is known to be the target of multiple potently neutralizing antibodies. One such antibody is 3H5, a mouse antibody that binds strongly to EDIII and potently neutralizes DENV serotype 2 (DENV-2) with unusually minimal antibody-dependent enhancement (ADE). To selectively display the binding epitope of 3H5, we strategically modified DENV-2 EDIII by shielding other known epitopes with engineered N-glycosylation sites. The modifications resulted in a glycosylated EDIII antigen termed "EDIII mutant N". This antigen was successfully used to sift through a dengue-immune scFv-phage library to select for scFv antibodies that bind to or closely surround the 3H5 epitope. The selected scFv antibodies were expressed as full-length human antibodies and showed potent neutralization activity to DENV-2 with low or negligible ADE resembling 3H5. These findings not only demonstrate the capability of the N-glycosylated EDIII mutant N as a tool to drive an epitope-directed antibody selection campaign but also highlight its potential as a dengue immunogen. This glycosylated antigen shows promise in focusing the antibody response toward a potently neutralizing epitope while reducing the risk of antibody-dependent enhancement.

A pre-vaccination immune metabolic interplay determines the protective antibody response to a dengue virus vaccine

Protective immunity to dengue virus (DENV) requires antibody response to all four serotypes. Systems vaccinology identifies a multi-OMICs pre-vaccination signature and mechanisms predictive of broad antibody responses after immunization with a tetravalent live attenuated DENV vaccine candidate (Butantan-DV/TV003). Anti-inflammatory pathways, including TGF-β signaling expressed by CD68low monocytes, and the metabolites phosphatidylcholine (PC) and phosphatidylethanolamine (PE) positively correlate with broadly neutralizing antibody responses against DENV. In contrast, expression of pro-inflammatory pathways and cytokines (IFN and IL-1) in CD68hi monocytes and primary and secondary bile acids negatively correlates with broad DENV-specific antibody responses. Induction of TGF-β and IFNs is done respectively by PC/PE and bile acids in CD68low and CD68hi monocytes. The inhibition of viral sensing by PC/PE-induced TGF-β is confirmed in vitro. Our studies show that the balance between metabolites and the pro- or anti-inflammatory state of innate immune cells drives broad and protective B cell response to a live attenuated dengue vaccine.

An Update on the Entomology, Virology, Pathogenesis, and Epidemiology Status of West Nile and Dengue Viruses in Europe (2018-2023)

In recent decades, increases in temperature and tropical rainfall have facilitated the spread of mosquito species into temperate zones. Mosquitoes are vectors for many viruses, including West Nile virus (WNV) and dengue virus (DENV), and pose a serious threat to public health. This review covers most of the current knowledge on the mosquito species associated with the transmission of WNV and DENV and their geographical distribution and discusses the main vertebrate hosts involved in the cycles of WNV or DENV. It also describes virological and pathogenic aspects of WNV or DENV infection, including emerging concepts linking WNV and DENV to the reproductive system. Furthermore, it provides an epidemiological analysis of the human cases of WNV and DENV reported in Europe, from 1 January 2018 to 31 December 2023, with a particular focus on Italy. The first autochthonous cases of DENV infection, with the most likely vector being Aedes albopictus, have been observed in several European countries in recent years, with a high incidence in Italy in 2023. The lack of treatments and effective vaccines is a serious challenge. Currently, the primary strategy to prevent the spread of WNV and DENV infections in humans remains to limit the spread of mosquitoes.

Defining correlates of protection for mammalian livestock vaccines against high-priority viral diseases

Enhancing livestock biosecurity is critical to safeguard the livelihoods of farmers, global and local economies, and food security. Vaccination is fundamental to the control and prevention of exotic and endemic high-priority infectious livestock diseases. Successful implementation of vaccination in a biosecurity plan is underpinned by a strong understanding of correlates of protection-those elements of the immune response that can reliably predict the level of protection from viral challenge. While correlates of protection have been successfully characterized for many human viral vaccines, for many high-priority livestock viral diseases, including African swine fever and foot and mouth disease, they remain largely uncharacterized. Current literature provides insights into potential correlates of protection that should be assessed during vaccine development for these high-priority mammalian livestock viral diseases. Establishment of correlates of protection for biosecurity purposes enables immune surveillance, rationale for vaccine development, and successful implementation of livestock vaccines as part of a biosecurity strategy.

Co-expression of VP2, NS1 and NS2-Nt proteins by an MVA viral vector induces complete protection against bluetongue virus

Introduction

Bluetongue (BT), caused by bluetongue virus (BTV), is an important arthropod-borne livestock disease listed by the World Organization for Animal Health. Live-attenuated and inactivated vaccines have permitted to control BT but they do not simultaneously protect against the myriad of BTV serotypes. Recently, we identified the highly conserved BTV nonstructural protein NS1 and the N-terminal region of NS2 as antigens capable of conferring multiserotype protection against BTV.

Methods

Here, we designed Modified Vaccinia Ankara (MVA) viral vectors that expressed BTV-4 proteins VP2 or VP7 along with NS1 and NS2-Nt as well as MVAs that expressed proteins VP2, VP7 or NS1 and NS2-Nt.

Results

Immunization of IFNAR(-/-) mice with two doses of MVA-NS1-2A-NS2-Nt protected mice from BTV-4M infection by the induction of an antigen-specific T cell immune response. Despite rMVA expressing VP7 alone were not protective in the IFNAR(-/-) mouse model, inclusion of VP7 in the vaccine formulation amplified the cell-mediated response induced by NS1 and NS2-Nt. Expression of VP2 elicited protective non-cross-reactive neutralizing antibodies (nAbs) in immunized animals and improved the protection observed in the MVA-NS1-2A-NS2-Nt immunized mice when these three BTV antigens were co-expressed. Moreover, vaccines candidates co-expressing VP2 or VP7 along with NS1 and NS2-Nt provided multiserotype protection. We assessed protective efficacy of both vaccine candidates in sheep against virulent challenge with BTV-4M.

Discussion

Immunization with MVA-VP7-NS1-2A-NS2-Nt partially dumped viral replication and clinical disease whereas administration of MVA-VP2-NS1-2A-NS2-Nt promoted a complete protection, preventing viraemia and the pathology produced by BTV infection.

Super epitope dengue vaccine instigated serotype independent immune protection in-silico

Dengue becomes the most common life-threatening infectious arbovirus disease globally, with prevalence in the tropical and subtropical areas. The major clinical features include dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), a condition of hypovolemic shock. Four different serotypes of the dengue virus, known as dengue virus serotype (DENV)- 1, 2, 3 and 4 can infect humans. Only one vaccine is available in the market, named Dengvaxia by Sanofi Pasteur, but there is no desired outcome of this treatment due the antibody dependent enhancement (ADE) of the multiple dengue serotypes. As of now, there is no cure against dengue disease. Our goal in this work was to create a subunit vaccine based on several epitopes that would be effective against every serotype of the dengue virus. Here, computational methods like- immunoinformatics and bioinformatics were implemented to find out possible dominant epitopes. A total of 21 epitopes were chosen using various in-silico techniques from the expected 133 major histocompatibility complex (MHC)- I and major histocompatibility complex (MHC)- II epitopes, along with 95 B-cell epitopes which were greatly conserved. Immune stimulant, non-allergenic and non-toxic immunodominant epitopes (super epitopes) with a suitable adjuvant (Heparin-Binding Hemagglutinin Adhesin, HBHA) were used to construct the vaccine. Following the physicochemical analysis, vaccine construct was docked with Toll-like receptors (TLRs) to predict the immune stimulation. Consequently, the optimal docked complex that demonstrated the least amount of ligand-receptor complex deformability was used to conduct the molecular dynamics analysis. By following the codon optimization, the final vaccine molecule was administered into an expressing vector to perform in-silico cloning. The robust immune responses were generated in the in-silico immune simulation analysis. Hence, this study provides a hope to control the dengue infections. For validation of the immune outcomes, in-vitro as well as in-vivo investigations are essential.

IgG, IgM, and Nonstructural Protein 1 Response Profiles after Receipt of Tetravalent Dengue Vaccine TAK-003 in a Phase 2 Randomized Controlled Trial

The profiles of vaccine-induced dengue antibodies may differ from those produced following natural infection and could potentially interfere with the interpretation of diagnostic tests. We assessed anti-dengue IgG and IgM antibodies, and nonstructural protein 1 antigen profiles in the serum of adults who received a single dose of the tetravalent dengue vaccine TAK-003 as either an initially developed high-dose formulation or the standard approved formulation in a phase 2 study in Singapore (#NCT02425098). Immunoglobulin G and IgM profiles during the first 30 days postvaccination varied by baseline serostatus (microneutralization assay). Nonstructural protein 1 antigen was not detected in the serum of any participants. Vaccine-induced IgG and IgM antibodies can affect serological confirmation of subsequent dengue infection in vaccinees. These results highlight the limitations of using serological tests for dengue diagnosis, particularly in a postvaccination setting, and emphasize the need for more sensitive antigen- and molecular-based testing for accurate dengue diagnosis.

Serological immune biomarker for disease severity in dengue-infected pediatric hospitalized patients

Clinical manifestation of dengue disease ranges from asymptomatic, febrile fever without warning sign (DOS) to serious outcome dengue with warning sign (DWS) and severe disease (SD) leading to shock syndrome and death. The role of antibody response in natural dengue infection is complex and not completely understood. Here, we aimed to assess serological marker for disease severity. Antibody response of dengue-confirmed pediatric patients with acute secondary infection were evaluated against infecting virus, immature virus, and recombinant envelop protein. Immature virus antibody titers were significantly higher in DWS as compared to DOS (p = 0.0006). However, antibody titers against recombinant envelop protein were higher in DOS as compared to DWS, and antibody avidity was significantly higher against infecting virus in DOS. Serum samples of DOS patients displayed higher in vitro neutralization potential in plaque assay as compared to DWS, whereas DWS serum samples showed higher antibody-dependent enhancement in the in vitro enhancement assays. Thus, antibodies targeting immature virus can predict disease severity and could be used in early forecast of disease outcome using an enzyme-linked immunoassay assay system which is less laborious and cheaper than plaque assay system for correlates of protection and could help optimize medical care and resources.

Unraveling the Genomic Evolution of Dengue Virus Serotype 1: A Case Study from Yantai, China

In August 2023, we identified a case of dengue fever in Yantai City, which was imported from Xishuangbanna, China. To investigate its evolutionary history and population dynamics, we utilized the metatranscriptomic method to obtain the virus' whole genome sequence. Together with 367 selected dengue virus whole genome sequences from the NCBI database, we constructed a time-scaled Maximum Clade Credibility (MCC) tree. We found that our sequence exhibited a high homology with a sequence of DENV1 (OR418422.1) uploaded by the Guangzhou Center for Disease Control and Prevention in 2023, with an estimated divergence time around 2019 (95% HPD: 2017-2023), coinciding with the emergence of SARS-CoV-2. The DENV strain obtained in this study belongs to genotype I of DENV1. Its ancestors experienced a global epidemic around 2005 (95% HPD: 2002-2010), and its progeny strains have spread extensively in Southeast Asia and China since around 2007 (95% HPD: 2006-2011). The Bayesian skyline plot indicates that the current population of DENV1 has not been affected by SARS-CoV-2 and is expected to maintain stable transmission. Hence, it is imperative to track and monitor its epidemiological trends and genomic variations to prevent potential large-scale outbreaks in the post-SARS-CoV-2 era.

Host Cell Proteases Involved in Human Respiratory Viral Infections and Their Inhibitors: A Review

Viral tropism is most commonly linked to receptor use, but host cell protease use can be a notable factor in susceptibility to infection. Here we review the use of host cell proteases by human viruses, focusing on those with primarily respiratory tropism, particularly SARS-CoV-2. We first describe the various classes of proteases present in the respiratory tract, as well as elsewhere in the body, and incorporate the targeting of these proteases as therapeutic drugs for use in humans. Host cell proteases are also linked to the systemic spread of viruses and play important roles outside of the respiratory tract; therefore, we address how proteases affect viruses across the spectrum of infections that can occur in humans, intending to understand the extrapulmonary spread of SARS-CoV-2.

Dengue virus transmission risk in blood donation: Evidence from Thailand

Individuals infected with dengue virus (DENV) often show no symptoms, which raises the risk of DENV transfusion transmission (TT-DENV) in areas where the virus is prevalent. This study aimed to determine the evidence of DENV infection in blood donors from different geographic regions of Thailand. A cross-sectional study was conducted on blood donor samples collected from the Thai Red Cross National Blood Center and four regional blood centers between March and September 2020. Screening for DENV nonstructural protein 1 (NS1), anti-DENV immunoglobulin G (IgG), and IgM antibodies was performed on residual blood from 1053 donors using enzyme-linked immunosorbent assay kits. Positive NS1 and IgM samples indicating acute infection were verified using four different techniques, including quantitative real-time (q) RT-PCR, nested PCR, virus isolation in C6/36 cells, and mosquito amplification. DENV IgG seropositivity was identified in 89% (938/1053) of blood donors. Additionally, 0.4% (4/1053) and 2.1% (22/1053) of Thai blood donors tested positive for NS1 and IgM, respectively. The presence of asymptomatic dengue virus infection in healthy blood donors suggests a potential risk of transmission through blood transfusion, posing a concern for blood safety.

Single-cell RNA sequencing reveals the expansion of circulating tissue-homing B cell subsets in secondary acute dengue viral infection

The roles of antibodies secreted by subsets of B cells in dengue virus (DENV) infection have been extensively studied, yet, the contribution of tissue-homing B cells to antiviral immunity remains unclear. In this study, we performed a comprehensive analysis of B cell subpopulations in peripheral blood samples from DENV-infected patients using single-cell RNA-sequencing (scRNA-seq) datasets and flow cytometry. We showed that plasma cells (PCs) and plasmablasts (PBs) were the predominant B cell populations during the acute phase of secondary natural DENV infection, but not in convalescent phase nor in healthy controls. Interestingly, these cells expressed proliferation, adhesion, and tissue-homing genes, including SELPLG, a homing marker of the skin, the initial infected site of DENV. Flow cytometry analysis confirmed a significant upregulation of cell surface expression of a cutaneous lymphocyte-associated antigen (CLA) encoded by SELPLG in PCs and PBs, compared to naive and memory B cells from the same patients. The analysis of an independent single-cell B-cell receptor sequencing (scBCR-seq) dataset of DENV-infected patients revealed that the peripheral blood PCs and PBs exhibited the highest clonal expansion in secondary DENV infection compared to other B cell subsets. These clonally expanded cells also expressed the highest levels of tissue-homing genes, including SELPLG. In addition, by utilizing a public scRNA-seq dataset of SARS-CoV2 infection, we demonstrated the upregulation of several tissue-homing genes in PCs and PBs. Our study provides evidence for the potential roles of tissue-homing B cell subsets in the context of immune responses against viral infections in humans.

Envelope-dimer epitope-like broadly protective antibodies against dengue in children following natural infection and vaccination

Cross-reactive antibodies (Abs) to epitopes that span envelope proteins on the virion surface are hypothesized to protect against dengue. Here, we measured Abs targeting the quaternary envelope dimer epitope (EDE) as well as neutralizing and binding Abs and evaluate their association with dengue virus (DENV) infection, vaccine response, and disease outcome in dengue vaccinated and unvaccinated children (n=252) within a longitudinal cohort in Cebu, Philippines (n=2,996). Abs targeting EDE were prevalent and strongly associated with broad neutralization of DENV1-4 in those with baseline multitypic immunity. Subsequent natural infection and vaccination boosted EDE-like, neutralizing, and binding Abs. EDE-like Abs were associated with reduced dengue risk and mediated the protective effect of binding and neutralizing Abs on symptomatic and severe dengue. Thus, Abs targeting quaternary epitopes help explain broad cross protection in those with multiple prior DENV exposures, making them useful for evaluation and development of future vaccines and therapeutics.

Vaccines Induce Homeostatic Immunity, Generating Several Secondary Benefits

The optimal immune response eliminates invading pathogens, restoring immune equilibrium without inflicting undue harm to the host. However, when a cascade of immunological reactions is triggered, the immune response can sometimes go into overdrive, potentially leading to harmful long-term effects or even death. The immune system is triggered mostly by infections, allergens, or medical interventions such as vaccination. This review examines how these immune triggers differ and why certain infections may dysregulate immune homeostasis, leading to inflammatory or allergic pathology and exacerbation of pre-existing conditions. However, many vaccines generate an optimal immune response and protect against the consequences of pathogen-induced immunological aggressiveness, and from a small number of unrelated pathogens and autoimmune diseases. Here, we propose an "immuno-wave" model describing a vaccine-induced "Goldilocks immunity", which leaves fine imprints of both pro-inflammatory and anti-inflammatory milieus, derived from both the innate and the adaptive arms of the immune system, in the body. The resulting balanced, 'quiet alert' state of the immune system may provide a jump-start in the defense against pathogens and any associated pathological inflammatory or allergic responses, allowing vaccines to go above and beyond their call of duty. In closing, we recommend formally investigating and reaping many of the secondary benefits of vaccines with appropriate clinical studies.

Viral Epitope Scanning Reveals Correlation between Seasonal HCoVs and SARS-CoV-2 Antibody Responses among Cancer and Non-Cancer Patients

Seasonal coronaviruses (HCoVs) are known to contribute to cross-reactive antibody (Ab) responses against SARS-CoV-2. While these responses are predictable due to the high homology between SARS-CoV-2 and other CoVs, the impact of these responses on susceptibility to SARS-CoV-2 infection in cancer patients is unclear. To investigate the influence of prior HCoV infection on anti-SARS-CoV-2 Ab responses among COVID-19 asymptomatic individuals with cancer and controls without cancers, we utilized the VirScan technology in which phage immunoprecipitation and sequencing (PhIP-seq) of longitudinal plasma samples was performed to investigate high-resolution (i.e., epitope level) humoral CoV responses. Despite testing positive for anti-SARS-CoV-2 Ab in the plasma, a majority of the participants were asymptomatic for COVID-19 with no prior history of COVID-19 diagnosis. Although the magnitudes of the anti-SARS-CoV-2 Ab responses were lower in individuals with Kaposi sarcoma (KS) compared to non-KS cancer individuals and those without cancer, the HCoV Ab repertoire was similar between individuals with and without cancer independent of age, sex, HIV status, and chemotherapy. The magnitudes of the anti-spike HCoV responses showed a strong positive association with those of the anti-SARS-CoV-2 spike in cancer patients, and only a weak association in non-cancer patients, suggesting that prior infection with HCoVs might play a role in limiting SARS-CoV-2 infection and COVID-19 disease severity.

Prior dengue virus serotype 3 infection modulates subsequent plasmablast responses to Zika virus infection in rhesus macaques

Immunodominant and highly conserved flavivirus envelope proteins can trigger cross-reactive IgG antibodies against related flaviviruses, which shapes subsequent protection or disease severity. This study examined how prior dengue serotype 3 (DENV-3) infection affects subsequent Zika virus (ZIKV) plasmablast responses in rhesus macaques (n = 4). We found that prior DENV-3 infection was not associated with diminished ZIKV-neutralizing antibodies or magnitude of plasmablast activation. Rather, characterization of 363 plasmablasts and their derivative 177 monoclonal antibody supernatants from acute ZIKV infection revealed that prior DENV-3 infection was associated with a differential isotype distribution toward IgG, lower somatic hypermutation, and lesser B cell receptor variable gene diversity as compared with repeat ZIKV challenge. We did not find long-lasting DENV-3 cross-reactive IgG after a ZIKV infection but did find persistent ZIKV-binding cross-reactive IgG after a DENV-3 infection, suggesting non-reciprocal cross-reactive immunity. Infection with ZIKV after DENV-3 boosted pre-existing DENV-3-neutralizing antibodies by two- to threefold, demonstrating immune imprinting. These findings suggest that the order of DENV and ZIKV infections has impact on the quality of early B cell immunity which has implications for optimal immunization strategies.

IMPORTANCE

The Zika virus epidemic of 2015-2016 in the Americas revealed that this mosquito-transmitted virus could be congenitally transmitted during pregnancy and cause birth defects in newborns. Currently, there are no interventions to mitigate this disease and Zika virus is likely to re-emerge. Understanding how protective antibody responses are generated against Zika virus can help in the development of a safe and effective vaccine. One main challenge is that Zika virus co-circulates with related viruses like dengue, such that prior exposure to one can generate cross-reactive antibodies against the other which may enhance infection and disease from the second virus. In this study, we sought to understand how prior dengue virus infection impacts subsequent immunity to Zika virus by single-cell sequencing of antibody producing cells in a second Zika virus infection. Identifying specific qualities of Zika virus immunity that are modulated by prior dengue virus immunity will enable optimal immunization strategies.

Prior flavivirus immunity skews the yellow fever vaccine response to cross-reactive antibodies with potential to enhance dengue virus infection

The yellow fever 17D vaccine (YF17D) is highly effective but is frequently administered to individuals with pre-existing cross-reactive immunity, potentially impacting their immune responses. Here, we investigate the impact of pre-existing flavivirus immunity induced by the tick-borne encephalitis virus (TBEV) vaccine on the response to YF17D vaccination in 250 individuals up to 28 days post-vaccination (pv) and 22 individuals sampled one-year pv. Our findings indicate that previous TBEV vaccination does not affect the early IgM-driven neutralizing response to YF17D. However, pre-vaccination sera enhance YF17D virus infection in vitro via antibody-dependent enhancement (ADE). Following YF17D vaccination, TBEV-pre-vaccinated individuals develop high amounts of cross-reactive IgG antibodies with poor neutralizing capacity. In contrast, TBEV-unvaccinated individuals elicit a non-cross-reacting neutralizing response. Using YF17D envelope protein mutants displaying different epitopes, we identify quaternary dimeric epitopes as the primary target of neutralizing antibodies. Additionally, TBEV-pre-vaccination skews the IgG response towards the pan-flavivirus fusion loop epitope (FLE), capable of mediating ADE of dengue and Zika virus infections in vitro. Together, we propose that YF17D vaccination conceals the FLE in individuals without prior flavivirus exposure but favors a cross-reactive IgG response in TBEV-pre-vaccinated recipients directed to the FLE with potential to enhance dengue virus infection.

Anti-Acinetobacter Baumannii single-chain variable fragments provide therapeutic efficacy in an immunocompromised mouse pneumonia model

BACKGROUND

The emergence of carbapenem-resistant and extensively drug-resistant (XDR) Acinetobacter baumannii as well as inadequate effective antibiotics calls for an urgent effort to find new antibacterial agents. The therapeutic efficacy of two human scFvs, EB211 and EB279, showing growth inhibitory activity against A. baumannii in vitro, was investigated in immunocompromised mice with A. baumannii pneumonia.

RESULTS

The data revealed that infected mice treated with EB211, EB279, and a combination of the two scFvs showed better survival, reduced bacterial load in the lungs, and no marked pathological abnormalities in the kidneys, liver, and lungs when compared to the control groups receiving normal saline or an irrelevant scFv.

CONCLUSIONS

The results from this study suggest that the scFvs with direct growth inhibitory activity could offer promising results in the treatment of pneumonia caused by XDR A. baumannii.

Lateral flow immunoassay (LFIA) for dengue diagnosis: Recent progress and prospect

Dengue is one of the most widespread and fatal arboviral infections in the world. Early detection of dengue virus (DENV) is essential to prevent the spread of the disease and provide an immediate response. The lateral flow immunoassay (LFIA) systems are low-cost, rapid, sensitive, targeted, and straightforward detection, which is an ideal early detection candidate for point-of-care testing (POCT) in dengue-affected areas. However, current commercial LFIA kits cannot fully satisfy the sensitivity, specificity, serotype differentiation, and multiplex detection requirements. Therefore, various strategies have been applied to optimize the LFIA for DENV detection, including label material improvement, optical enhancement and novel structure design. In this review, we comprehensively presented the snapshot of dengue, the principle of LFIA, and recent progress in the LFIA optimization for dengue diagnoses. Furthermore, this review also discusses insights into the prospect of LFIA dengue diagnostic methods, such as microfluidics, multiplex design, nucleic acid-typed probes and smartphone-assisted result analysis.

Suppression of dengue virus replication by the French maritime pine extract Pycnogenol®

Dengue virus (DENV) is mainly found in the tropics and infects approximately 400 million people annually. However, no clinically available therapeutic agents specific to dengue have been developed. Here, we examined the potential antiviral effects of the French maritime pine extract Pycnogenol® (PYC) against DENV because we previously found that the extract exerts antiviral effects on hepatitis C virus, which belongs to the Flavivirus family. First, we examined the efficacy of PYC against DENV1, 2, 3, and 4 serotypes and determined that it had a dose-dependent suppressive effect on the viral load, especially in the supernatant. This inhibitory effect of PYC may target the late stages of infection such as maturation and secretion, but not replication. Next, we examined the efficacy of PYC against DENV infection in type I interferon (IFN) receptor knockout mice (A129). As the propagation of DENV2 was the highest among the four serotypes, we used this serotype in our murine model experiments. We found that PYC significantly inhibited DENV2 replication in mice on day 4 without significantly decreasing body weight or survival ratio. We further examined the mechanism of action of PYC in DENV2 infection by characterizing the main PYC targets among the host (viral) factors and silencing them using siRNA. Silencing long noncoding-interferon-induced protein (lnc-IFI)-44, polycystic kidney disease 1-like 3 (Pkd1l3), and ubiquitin-specific peptidase 31 (Usp31) inhibited the replication of DENV2. Thus, the results of this study shed light on the inhibitory effects of PYC on DENV replication and its underlying mechanisms.

Viral infections and pathogenesis of glaucoma: a comprehensive review

Glaucoma is a leading cause of irreversible blindness worldwide, caused by the gradual degeneration of retinal ganglion cells and their axons. While glaucoma is primarily considered a genetic and age-related disease, some inflammatory conditions, such as uveitis and viral-induced anterior segment inflammation, cause secondary or uveitic glaucoma. Viruses are predominant ocular pathogens and can impose both acute and chronic pathological insults to the human eye. Many viruses, including herpes simplex virus, varicella-zoster virus, cytomegalovirus, rubella virus, dengue virus, chikungunya virus, Ebola virus, and, more recently, Zika virus (ZIKV) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), have been associated with sequela of either primary or secondary glaucoma. Epidemiological and clinical studies suggest the association between these viruses and subsequent glaucoma development. Despite this, the ocular manifestation and sequela of viral infections are not well understood. In fact, the association of viruses with glaucoma is considered relatively uncommon in part due to underreporting and/or lack of long-term follow-up studies. In recent years, literature on the pathological spectrum of emerging viral infections, such as ZIKV and SARS-CoV-2, has strengthened this proposition and renewed research activity in this area. Clinical studies from endemic regions as well as laboratory and preclinical investigations demonstrate a strong link between an infectious trigger and development of glaucomatous pathology. In this article, we review the current understanding of the field with a particular focus on viruses and their association with the pathogenesis of glaucoma.

Integrated control strategies for dengue, Zika, and Chikungunya virus infections

Arboviruses are a major threat to public health in tropical regions, encompassing over 534 distinct species, with 134 capable of causing diseases in humans. These viruses are transmitted through arthropod vectors that cause symptoms such as fever, headache, joint pains, and rash, in addition to more serious cases that can lead to death. Among the arboviruses, dengue virus stands out as the most prevalent, annually affecting approximately 16.2 million individuals solely in the Americas. Furthermore, the re-emergence of the Zika virus and the recurrent outbreaks of chikungunya in Africa, Asia, Europe, and the Americas, with one million cases reported annually, underscore the urgency of addressing this public health challenge. In this manuscript we discuss the epidemiology, viral structure, pathogenicity and integrated control strategies to combat arboviruses, and the most used tools, such as vaccines, monoclonal antibodies, treatment, etc., in addition to presenting future perspectives for the control of arboviruses. Currently, specific medications for treating arbovirus infections are lacking, and symptom management remains the primary approach. However, promising advancements have been made in certain treatments, such as Chloroquine, Niclosamide, and Isatin derivatives, which have demonstrated notable antiviral properties against these arboviruses in vitro and in vivo experiments. Additionally, various strategies within vector control approaches have shown significant promise in reducing arbovirus transmission rates. These encompass public education initiatives, targeted insecticide applications, and innovative approaches like manipulating mosquito bacterial symbionts, such as Wolbachia. In conclusion, combatting the global threat of arbovirus diseases needs a comprehensive approach integrating antiviral research, vaccination, and vector control. The continued efforts of research communities, alongside collaborative partnerships with public health authorities, are imperative to effectively address and mitigate the impact of these arboviral infections on public health worldwide.

Computer-aided Affinity Enhancement of a Cross-reactive Antibody against Dengue Virus Envelope Domain III

The dengue virus (DENV), composed of four distinct but serologically related Flaviviruses, causes the most important emerging viral disease, with nearly 400 million infections yearly. Currently, there are no approved therapies. Although DENV infection induces lifelong immunity against the same serotype, the antibodies raised contribute to severe disease in heterotypic infections. Therefore, understanding the mechanism of DENV neutralization by antibodies is crucial in the design of vaccines against all serotypes. This study reports a comparative structural and energetic analysis of the monoclonal antibody (mAb) 4E11 in complex with its target domain III of the envelope protein for all four DENV serotypes. We use extensive replica molecular dynamics simulations in conjunction with the binding free energy calculations. Further single point and double mutations were designed through computational site-directed mutagenesis and observed that the re-engineered antibody exhibits high affinity to binding and broadly neutralizing activity against serotypes. Our results showed improved binding affinity by the gain of enthalpy, which could be attributed to the stabilization of salt-bridge and hydrogen bond interactions at the antigen-antibody interface. The findings provide valuable results in understanding the structural dynamics and energetic contributions that will be helpful to the design of high-affinity antibodies against dengue infections.

Development of flavivirus subviral particles with low cross-reactivity by mutations of a distinct antigenic domain

The most conserved fusion loop (FL) domain present in the flavivirus envelope protein has been reported as a dominant epitope for cross-reactive antibodies to mosquito-borne flaviviruses (MBFVs). As a result, establishing accurate serodiagnosis for MBFV infections has been difficult as anti-FL antibodies are induced by both natural infection and following vaccination. In this study, we modified the most conserved FL domain to overcome this cross-reactivity. We showed that the FL domain of lineage I insect-specific flavivirus (ISFV) has differences in antigenicity from those of MBFVs and lineage II ISFV and determined the key amino acid residues (G106, L107, or F108), which contribute to the antigenic difference. These mutations were subsequently introduced into subviral particles (SVPs) of dengue virus type 2 (DENV2), Zika virus (ZIKV), Japanese encephalitis virus (JEV), and West Nile virus (WNV). In indirect enzyme-linked immunosorbent assays (ELISAs), these SVP mutants when used as antigens reduced the binding of cross-reactive IgG and total Ig induced by infection of ZIKV, JEV, and WNV in mice and enabled the sensitive detection of virus-specific antibodies. Furthermore, immunization of ZIKV or JEV SVP mutants provoked the production of antibodies with lower cross-reactivity to heterologous MBFV antigens compared to immunization with the wild-type SVPs in mice. This study highlights the effectiveness of introducing mutations in the FL domain in MBFV SVPs with lineage I ISFV-derived amino acids to produce SVP antigens with low cross-reactivity and demonstrates an improvement in the accuracy of indirect ELISA-based serodiagnosis for MBFV infections. KEY POINTS: • The FL domain of Lineage I ISFV has a different antigenicity from that of MBFVs. • Mutated SVPs reduce the binding of cross-reactive antibodies in indirect ELISAs. • Inoculation of mutated SVPs induces antibodies with low cross-reactivity.