Primary exposure to Zika virus is linked with increased risk of symptomatic dengue virus infection with serotypes 2, 3, and 4, but not 1

Preexisting Yellow Fever Virus and West Nile Virus Immunity and Pregnancy Outcomes in a Nigerian Cohort with Endemic Flavivirus Exposure

Background

Yellow fever virus (YFV) and West Nile virus (WNV) co-circulate with other arboviruses, including Zika (ZIKV), dengue (DENV), and chikungunya virus (CHIKV), in sub-Saharan Africa. Associations between preexisting YFV and WNV immunity with symptoms and adverse infant outcomes among pregnant women exposed to flaviviruses are unknown.

Methods

We retrospectively studied a prospective cohort of pregnant women enrolled between 2019 and 2022 in Jos, Nigeria. Rapid tests identified ZIKV, DENV, and CHIKV IgM/IgG reactivity for enrollment; 216 women underwent Western blot for YFV and WNV IgG. Logistic regression evaluated associations between arboviral seropositivity and maternal symptoms or adverse infant outcomes. Sequential serology of mother-infant pairs estimated the persistence of passively transferred maternal YFV antibodies.

Findings

YFV IgG was detected in 50.5% (109/216) and WNV IgG in 5.1% (11/216) of maternal samples. YFV and WNV seropositivity was significantly associated with maternal symptoms (OR = 2.02, 95% CI: 1.35-3.02, P = 0.001), as was YFV seropositivity alone (OR = 1.77, 95% CI: 1.21-2.61, P < 0.004). CHIKV IgM reactivity was significantly associated with abnormal infant outcomes (OR = 2.38, 95% CI: 1.43-4.02, p = 0.001), but not ZIKV and DENV IgM reactivity. Passive maternal YFV IgG waned in infants at a median of 3.1 months (IQR: 1.65-5.35 months) after birth.

Interpretation

YFV and WNV seropositivity was associated with maternal symptoms but not with adverse infant outcomes. Rapid waning of maternal YFV IgG highlights infant vulnerability and supports enhanced surveillance and maternal immunization strategies.

Enhanced durability of a Zika virus self-amplifying RNA vaccine through combinatorial OX40 and 4-1BB agonism

The SARS-CoV-2 pandemic highlighted the potential of mRNA vaccines in rapidly responding to emerging pathogens. However, immunity induced by conventional mRNA vaccines wanes quickly, requiring frequent boosters. Self-amplifying RNA (saRNA) vaccines, which extend antigen expression via self-replication, offer a promising strategy to induce more durable immune responses. In this study, we developed an saRNA vaccine encoding Zika virus (ZIKV) membrane and envelope proteins and evaluated its efficacy in mice. A single vaccination elicited strong humoral and cellular immune responses and reduced viral loads but only for 28 days. By day 84, antibody titers and T cell responses had significantly declined, resulting in reduced efficacy. To address this, we evaluated agonist antibodies targeting the T cell costimulatory molecules OX40 and 4-1BB. Coadministration of agonist antibodies enhanced CD8+ T cell responses to vaccination, resulting in sustained immunity and reduced viral loads at day 84. Depletion and passive transfer studies verified that long-term antiviral immunity was primarily CD8+ T cell dependent, with minimal contributions from antibody responses. These findings suggest that agonists targeting members of the tumor necrosis receptor superfamily, such as OX40 and 4-1BB, might enhance the durability of saRNA vaccine-induced protection, addressing a key limitation of current mRNA vaccine platforms.

Dengue Dilemma: Navigating Cross-Reactivity and Immune Challenges

This chapter examines the immunological mechanisms underlying the cross-reactivity and immune enhancement in dengue and how they influence the clinical outcomes. The four DENV serotypes (DENV-1 to DENV-4) share high genetic and antigenic similarity, leading to antibodies and T cells that can recognize multiple serotypes. While this cross-reactive immunity can confer partial or transient protection, it can also result in antibody-dependent enhancement (ADE), wherein non-neutralizing antibodies facilitate viral entry into immune cells, increasing the likelihood of severe disease in secondary infections and in infants carrying maternal anti-DENV antibodies. Furthermore, cross-reactivity with other flaviviruses, such as ZIKV, complicates serological diagnosis by producing false-positive results and uncertain prior exposure histories. These complexities extend to vaccine design, which must induce effective immunity against all four DENV serotypes while minimizing ADE risk. Epidemiological studies confirm that secondary infections, especially when antibody levels have waned, carry an elevated risk of severe clinical manifestations. However, the timing between infections and the specific serotype involved can modulate these outcomes. A thorough understanding of cross-reactivity and immune enhancement is therefore pivotal for advancing diagnostic accuracy, guiding patient care, and informing vaccine strategies and public health policies to better control dengue globally.

Anti-dengue virus antibodies that elicit complement-mediated lysis of Zika virion correlate with protection from severe dengue disease

Antibodies from primary dengue (DENV1-4) or Zika (ZIKV) virus infections can influence subsequent heterotypic infections, but their protective characteristics are not well defined. We analyzed pre-infection plasma samples from children in our Nicaraguan cohort study who later developed either dengue fever (DF; n = 31) or dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS; n = 33) upon secondary heterotypic DENV infection. Various antibody properties, notably antibody-dependent complement deposition, correlated with protection against DHF/DSS. Interestingly, this association was strongest when using recombinant ZIKV antigens despite participants being ZIKV naive. Additionally, complement-mediated virion lysis (virolysis) with ZIKV virions was strongly associated with protection, a finding replicated in an independent sample set. ZIKV virolysis emerged as the only antibody property linked to reduced risk of DHF/DSS and severe symptoms such as thrombocytopenia and plasma leakage. These results suggest that ZIKV-cross-reactive anti-DENV antibodies that mediate complement-dependent virolysis may lower the risk of severe disease, informing the development of effective dengue vaccines and therapeutics.

Quantifying temporal differences in the induction of interferon-mediated signalling observed in a dengue virus 1 human infection model: insights from longitudinal proteome analysis

BACKGROUND

According to WHO, dengue is one of the top ten global health threats, with almost half of the world's population at risk of being infected. Most of the annual 400 million dengue virus (DENV) infections manifest asymptomatically or in a mild form, causing symptoms such as fever and headache. Nevertheless, every year 500,000 dengue cases require hospitalization and up to 25,000 patients die. Despite the high incidence, the DENV-elicited proteome response remains insufficiently understood.

METHODS

Therefore, we evaluated the proteome dynamics of nine dengue-naïve individuals experimentally infected with the underattenuated DENV-1 strain 45AZ5 via the Proximity Extension Assay technology of Olink®.

FINDINGS

Using Olink Explore, a total of ∼3000 proteins were quantified simultaneously in serum samples at 8, 10, 14, and 28 days after the viral inoculation. We identified the top ten significant proteins via linear mixed effects models, i.e., interferons (IFNs), IFN-related proteins, and members of the CCL and CXCL chemokine family. In all participants, an increase in IFN-λ1 levels was observed after peak viral load, whereas in one participant an IFN-γ response was not detected. Interestingly, both the onset and peak viral load of this participant were, on average, delayed 4 days compared to other participants. To gain a detailed kinetic overview of the DENV-elicited proteome response, we designed a smaller, targeted Olink® panel to evaluate serum protein levels at multiple time points throughout the infection. Here, we revealed that type I/III IFN response precedes the type II IFN response.

INTERPRETATION

In conclusion, our analyses provided detailed insights into the temporal dynamics of the different IFN responses upon a primary DENV-1 infection. These insights might aid in better understanding dengue pathogenesis.

FUNDING

Funding for this research was provided by Johnson and Johnson, the State of New York, and the Congressionally Directed Medical Research Programs.

Zika virus: an overview update

PURPOSE OF REVIEW

Although cases of Zika virus disease (ZVD) have declined globally since 2017, new outbreaks have been reported, such as in Asia in 2024. As there is no vaccine or treatment available to date, both vaccines and mAbs neutralizing Zika virus would be of great interest, especially for pregnant women and immunocompromised patients such as those living with HIV. This review focuses on new insights regarding ZVD in the last two years and summarizes the key literature on global epidemiology, transmission, diagnostics, clinical features, preventive measures, and treatment options.

RECENT FINDINGS

At the time of writing, ZVD is endemic across tropical and subtropical regions of the world, with the highest risk of infection in Latin America and the Caribbean, but no significant peaks in outbreak activity across endemic regions. There are ongoing efforts to further investigate the clinical and epidemiological long-term sequelae of the large outbreak in the Americas 2015-2018; further refinement of diagnostic tools to improve specificity in view of significant cross-reactivity potential, particularly with dengue virus. Multiple vaccines are in different clinical development stages; however, phase 3 trials are awaiting the next epidemic.

SUMMARY

While there is no current major zika virus outbreak, progress has been made in the epidemiological work-up of clinical-epidemiological data, refinement of diagnostic tools, and mainly preventive (vaccines) rather than curative (drugs) tools.

Zika Virus: A Review of Biology, Clinical Impacts, and Coinfections

The Zika virus (ZIKV) gained prominence as a significant global pathogen after the 2015-2016 outbreaks associated it with an increase in neurological complications in adults and congenital malformations. Different mechanisms have been proposed by which ZIKV may cross the blood-brain barrier and reach the central nervous system to cause neuroinflammation. Although ZIKV infection triggers a robust immune response, the virus has developed different strategies to escape it. Furthermore, although the virus is present in areas with cocirculation of other pathogenic agents, few studies have evaluated the cross-immune reactions and coinfection of ZIKV. Coinfections of ZIKV with other viruses, parasites, and bacteria are described. Such interactions can worsen infections and alter the immune response, imposing new therapeutic challenges and highlighting the need for more studies in the field. In this review, we discuss various aspects of ZIKV biology, focusing on the impacts of coinfections.

Enhancing capacities in genomic surveillance capabilities for SARS-CoV-2 and dengue virus: A South-South collaborative partnership

Latin American countries have faced limited access to new scientific technologies for many years due to restricted budgets for research programs, which has hindered local scientific development. These research disparities became especially evident during the COVID-19 pandemic, as lower-middle-income countries (LMICs) like Ecuador and Nicaragua had restricted access to genomic surveillance protocols, sequencing technologies, and adequate infrastructure, compromising global pandemic preparedness and response. In response to the urgent need for SARS-CoV-2 research capabilities in these countries, the Asian-American Center for Arbovirus Research and Enhanced Surveillance led the initiative, collaborating with the NGO Sustainable Sciences Institute and LMIC stakeholders, including universities and Ministries of Health, to develop pandemic-related research programs, provide resources, and conduct peer training workshops for local health scientists. Over the past five years, collaborative efforts have enabled teams in Ecuador and Nicaragua to establish sustainable research capacity and technology-sharing initiatives, as showcased by the institutionalization of government-led genomic surveillance efforts. This has opened new research opportunities in genomic surveillance for other emerging and reemerging pathogens and strengthening South-South collaboration.

Proceedings of the second annual dengue endgame summit: A call to action

On August 7-9, 2024, the second annual dengue "endgame" summit was held in Syracuse, NY, hosted by the Global Health Institute at SUNY Upstate Medical University. The meeting brought together attendees from around the world, with talks spanning healthcare, government control programs, basic research, and medical countermeasure development efforts. The summit goal was to work toward a better understanding of what dengue control could look like and the steps required to reach such a goal. The objectives of the meeting were to discuss the current global state of dengue, what dengue "control" might look like, and to discuss actionable pathways for achieving dengue control. Topics covered throughout the meeting included DENV immunity and pathogenesis, challenges in countermeasure development, innovative vector control strategies, dengue diagnostics, addressing challenges in science communication, and vaccine hesitancy. Several fundamental knowledge gaps were repeatedly highlighted by the summit attendees and were cited as critical barriers to the development, deployment, and evaluation of effective dengue countermeasures. These gaps include (1) the lack of a broadly applicable immunologic biomarker/correlate of DENV immunity and (2) the lack of universally accepted/applicable metrics for quantifying dengue severity in the setting of countermeasure evaluations. In addition, the lack of clear and consistent international leadership in the global dengue control effort was cited as a barrier to widespread and synergistic research and countermeasure development/deployment activities. Despite these persistent roadblocks, summit attendees expressed optimism that holistic and multi-tiered approaches-incorporating optimal use of existing and nascent countermeasure technologies deployed in collaboration with local communities-could be effective in progressing toward dengue control.

IgA-driven neutrophil activation underlies post-Zika severe dengue disease in humans

The four dengue virus serotypes (DENV1-4) and the related Zika flavivirus (ZIKV) are major public health concerns worldwide. Primary immunity against ZIKV increases the risk of a subsequent severe DENV2 infection, presenting a significant challenge for developing safe and effective ZIKV vaccines. However, the mechanisms driving this phenomenon remain unclear. Leveraging our long-standing Pediatric Dengue Cohort Study in Nicaragua, we show that serum anti-NS1 IgA antibodies elicited after a primary ZIKV infection drive neutrophil activation and correlate with increased risk of subsequent severe DENV2 disease. Depletion experiments combined with ex vivo functional NETosis assays confirmed that anti-NS1 IgA antibodies drive neutrophil activation in dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). Moreover, increased neutrophil degranulation in paired serum samples obtained during the acute DENV2 infection from the same individuals correlated with IgA binding to DENV2 NS1 and preceded the development of vascular leakage. This finding was corroborated in an orthogonal hospital-based study. Thus, serum anti-NS1 IgA enhances neutrophil activation in severe dengue, with implications for prognostics, therapeutics, and vaccines.

Higher abundance of the vector Aedes aegypti in rural areas than in urban areas in Managua, Nicaragua

Background

Ae. aegypti is the primary vector of dengue, chikungunya, and Zika viruses, traditionally associated with urban environments. However, its presence and abundance in rural settings remain understudied. This study compares Ae. aegyptipopulations between rural and urban communities in Managua, Nicaragua, across different seasons over multiple years.

Methods

Entomological surveys were conducted in 500 randomly selected households (250 rural, 250 urban) during the rainy and dry seasons of 2022 and 2023. Immature mosquitoes were collected from water-holding containers, and adult mosquitoes were sampled using aspirators. Entomological indices, including Stegomyia, pupal, and adult indices, were compared across seasons and localities.

Results

All entomological indices were significantly higher in rural communities than in urban areas across both years and seasons. Rural households had greater mosquito densities, with pupal productivity concentrated in large water storage containers. Adult mosquito collections confirmed a greater Ae. aegypti presence in rural areas, suggesting sustained transmission risk. We observed pupal thresholds in water-holding containers for female adult collections.

Discussion

Contrary to the conventional view of Ae. aegypti as an urban mosquito, our findings highlight its substantial presence in rural settings, likely driven by water storage practices and environmental conditions. These results align with findings from other regions reporting high mosquito abundance in rural areas, challenging assumptions about urban dominance.

Conclusion

Rural areas play a crucial role in sustaining Ae. aegypti populations. Vector control strategies should target both rural and urban communities, with seasonally tailored interventions to mitigate disease transmission risks.

Efficacy of emergency maternal MVA-ZIKV vaccination in a rapid challenge model of lethal Zika infection

Zika virus (ZIKV) outbreak of 2015 was associated with microcephaly and congenital birth defects in children born to pregnant women infected with ZIKV. Using the highly susceptible Type I Interferon Receptor-deficient mouse-model, we demonstrate that a single emergency vaccination with a non-replicating MVA-ZIKV vaccine, when administered as early as 2-days before challenge fully protected non-pregnant and pregnant mice and fetuses against lethal ZIKV-infection. Early protection was associated with the rapid emergence of ZIKV-specific CD8+ T cell responses; depletion of CD8+ T cells resulted in the loss of protection supporting a critical role for CD8+ T cells in the early protective efficacy of MVA-ZIKV. Neutralizing antibody responses were induced later than the CD8+ T cell responses, suggesting that it may play a role in later stages of infection. Our results suggest that MVA-ZIKV induces potent anamnestic cellular immunity early after infection, contributing to its protective efficacy against rapid ZIKV challenge.

Serotype-specific epidemiological patterns of inapparent versus symptomatic primary dengue virus infections: a 17-year cohort study in Nicaragua

BACKGROUND

Dengue is the most prevalent mosquito-borne viral disease and a major public health problem worldwide. Most primary infections with the four dengue virus serotypes (DENV1-4) are inapparent; nonetheless, whether the distribution of symptomatic versus inapparent infections by serotype varies remains unknown. Here, we present (1) the evaluation of a DENV1-4 envelope domain III multiplex microsphere-based assay (EDIII-MMBA) to serotype inapparent primary infections and (2) its application leveraging 17 years of prospective sample collection from the Nicaraguan Pediatric Dengue Cohort Study (PDCS).

METHODS

We analysed primary DENV infections in the PDCS from 2004 to 2022 detected by inhibition ELISA (iELISA) or RT-PCR. First, we evaluated the performance of the EDIII-MMBA for serotyping with samples characterised by RT-PCR or focus reduction neutralisation test. Next, we analysed a subset of inapparent primary DENV infections in the PDCS with the EDIII-MMBA to evaluate the epidemiology of inapparent infections. Remaining infections were inferred using stochastic imputation, taking year and neighbourhood into account. Infection incidence and percentage of inapparent, symptomatic, and severe infections were analysed by serotype.

FINDINGS

Between Aug 30, 2004, and March 10, 2022, a total of 5931 DENV-naive participants were followed in the PDCS. There were 1626 primary infections (382 symptomatic, 1244 inapparent) detected by iELISA or RT-PCR over the study period. The EDIII-MMBA demonstrated excellent overall accuracy (100%, 95% CI 95·8-100) for serotyping inapparent primary DENV infections when evaluated against gold-standard serotyping methods. Of the 1244 inapparent infections, we analysed 574 (46%) using the EDIII-MMBA. We found that the majority of primary infections were inapparent, with DENV3 exhibiting the highest likelihood of symptomatic (pooled odds ratio compared with DENV1: 2·13, 95% CI 1·28-3·56) and severe (6·75, 2·01-22·62) primary infections, whereas DENV2 was similar to DENV1 in both analyses. Considerable within-year and between-year variation in serotype distribution between symptomatic and inapparent infections and circulation of serotypes undetected in symptomatic cases were observed in multiple years.

INTERPRETATION

Our study indicates that case surveillance skews the perceived epidemiological footprint of DENV. We reveal a more complex and intricate pattern of serotype distribution in inapparent infections. The substantial differences in infection outcomes by serotype emphasises the need for vaccines with balanced immunogenicity and efficacy across serotypes.

FUNDING

National Institute of Allergy and Infectious Diseases (National Institutes of Health) and Bill & Melinda Gates Foundation.

TRANSLATION

For the Spanish translation of the abstract see Supplementary Materials section.

Zika virus vaccines and monoclonal antibodies: a priority agenda for research and development

The 2015-16 Zika virus epidemic in the Americas drew global attention to Zika virus infection as a cause of microcephaly and Guillain-Barré syndrome. The epidemic highlighted the urgent need for preventive measures, including vaccines and monoclonal antibodies (mAbs). However, nearly 9 years later, no licensed Zika virus vaccines or mAbs are available, leaving the world's populations unprotected from ongoing disease transmission and future epidemics. The current low Zika virus incidence and unpredictability of future outbreaks complicates prospects for evaluation, licensure, and commercial viability of Zika virus vaccines and mAbs. We conducted an extensive review of Zika virus vaccines and mAbs in development, identifying 16 vaccines in phase 1 or phase 2 trials and three mAbs in phase 1 trials, and convened a 2-day meeting of 130 global Zika virus experts to discuss research priorities to advance their development. This Series paper summarises a priority research agenda to address key knowledge gaps and accelerate the licensure of Zika virus vaccines and mAbs for global use.

Dengue severity by serotype and immune status in 19 years of pediatric clinical studies in Nicaragua

BACKGROUND

Dengue virus, a major global health threat, consists of four serotypes (DENV1-4) that cause a range of clinical manifestations from mild to severe and potentially fatal disease.

METHODS

This study, based on 19 years of data from the Pediatric Dengue Cohort Study and Pediatric Dengue Hospital-based Study in Managua, Nicaragua, investigates the relationship of serotype and immune status with dengue severity. Dengue cases were confirmed by molecular, serological, and/or virological methods, and study participants 6 months to 17 years old were followed during their hospital stay or as ambulatory patients.

RESULTS

We enrolled a total of 15,833 participants, of whom 3,308 (21%) were positive for DENV infection. Of 2,644 cases with serotype result by RT-PCR, 559 corresponded to DENV1, 1,002 to DENV2, 760 to DENV3 and 323 to DENV4. Severe disease was more prevalent among secondary DENV2 and DENV4 cases, while similar disease severity was observed in both primary and secondary DENV1 and DENV3 cases. According to the 1997 World Health Organization (WHO) severity classification, both DENV2 and DENV3 caused a higher proportion of severe disease compared to other serotypes, whereas DENV3 caused the greatest percentage of severity according to the WHO-2009 classification. DENV2 was associated with increased odds of pleural effusion and low platelet count, while DENV3 was associated with both hypotensive and compensated shock.

CONCLUSIONS

These findings demonstrate differences in dengue severity by serotype and immune status and emphasize the critical need for a dengue vaccine with balanced effectiveness against all four serotypes, particularly as existing vaccines show variable efficacy by serotype and serostatus.

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.

Epidemiological, virological and clinical characterization of a Dengue/Zika outbreak in the Caribbean region of Costa Rica 2017-2018

The increase in incidence and geographical expansion of viruses transmitted by the Aedes mosquitoes, such as dengue (DENV) and zika (ZIKV) in the Americas, represents a burden for healthcare systems in tropical and subtropical regions. These and other under-detected arboviruses co-circulate in Costa Rica, adding additional complexity to their management due to their shared epidemiological behavior and similarity of symptoms in early stages. Since diagnostics of febrile illness is mostly based on clinical symptoms alone, we gathered acute-phase serum and urine from 399 samples of acute dengue-like cases from two healthcare facilities of Costa Rica, during an outbreak of arboviruses from July 2017 to May 2018, and tested them using molecular and serological methods. The analyses showed that of the clinically presumptive arbovirus cases that were reported, only 39.4% (n=153) of the samples were confirmed positive by RT-PCR to be DENV (DENV (10.3%), CHIKV (0.2%), ZIKV (27.3%), or mixed infections (1.5%). RT-PCR for other alphaviruses and flaviviruses, and PCR for Leptospira sp were negative. Furthermore, to assess flavivirus positivity in post-acute patients, the negative sera were tested against Dengue-IgM. 20% of sera were found positive, confounding even more the definitive number of cases, and emphasizing the need of several distinct diagnostic tools for accurate diagnostics. Molecular characterization of the prM and E genes from isolated viruses revealed that the American/Asian genotype of DENV-2 and the Asian lineage of ZIKV were circulating during this outbreak. Two different clades of DENV-2 American/Asian genotype were identified to co-circulate in the same region and a difference in the platelet and leukocyte count was noted between people infected with each clade, suggesting a putative distinct virulence. Our study sheds light on the necessity for healthcare strategies in managing arbovirus outbreaks, emphasizing the importance of comprehensive molecular and serological diagnostic approaches, as well as molecular characterization. This approach aids in enhancing our understanding of the clinical and epidemiological aspects of arboviral diseases during outbreaks. Our research highlights the need to strengthen training programs for health professionals and the need to increase research-based on laboratory evidence for diagnostic accuracy, guidance, development and implementation of public health interventions and epidemiological surveillance.

Complement-dependent virion lysis mediated by dengue-Zika virus cross-reactive antibodies correlates with protection from severe dengue disease

Primary infection with one of four dengue virus serotypes (DENV1-4) may generate antibodies that protect or enhance subsequent secondary heterotypic infections. However, the characteristics of heterotypic cross-reactive antibodies associated with protection from symptomatic infection and severe disease are not well-defined. We selected plasma samples collected before a secondary DENV heterotypic infection that was classified either as dengue fever (DF, n = 31) or dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS, n = 33) from our longstanding pediatric cohort in Nicaragua. We screened various antibody properties to determine the features correlated with protection from DHF/DSS. Protection was associated with high levels of binding of various antibody isotypes, IgG subclasses and effector functions, including antibody-dependent complement deposition, ADCD. Although the samples were derived from DENV-exposed, Zika virus (ZIKV)-naïve individuals, the protective ADCD association was stronger when assays were conducted with recombinant ZIKV antigens. Further, we showed that a complement-mediated virion lysis (virolysis) assay conducted with ZIKV virions was strongly associated with protection, a finding reproduced in an independent sample set collected prior to secondary heterotypic inapparent versus symptomatic DENV infection. Virolysis was the main antibody feature correlated with protection from DHF/DSS and severe symptoms, such as thrombocytopenia, hemorrhagic manifestations, and plasma leakage. Hence, anti-DENV antibodies that cross-react with ZIKV, target virion-associated epitopes, and mediate complement-dependent virolysis are correlated with protection from secondary symptomatic DENV infection and DHF/DSS. These findings may support the rational design and evaluation of dengue vaccines and development of therapeutics.