Humoral correlates of protection against influenza A H3N2 virus infection.

BACKGROUND: Influenza virus remains a threat to human health, but gaps remain in our knowledge of the humoral correlates of protection against influenza virus A/H3N2, limiting our ability to generate effective, broadly protective vaccines. The role of antibodies against the hemagglutinin (HA) stalk, a highly conserved but immunologically sub-dominant region, has not been established for influenza virus A/H3N2. METHODS: Household transmission studies were conducted in Managua, Nicaragua across three influenza seasons. Household contacts were tested for influenza virus infection using RT-PCR. We compared pre-existing antibody levels against full-length hemagglutinin (FLHA), HA stalk, and neuraminidase (NA) measured by enzyme-linked immunosorbent assay (ELISA), along with HA inhibition assay (HAI) titers, between infected and uninfected participants. RESULTS: A total of 899 individuals participated in household activation, with 329 infections occurring. A four-fold increase in initial HA stalk titers was independently associated with an 18% decrease in the risk of infection (OR=0.82, 95%CI 0.68-0.98, p=0.04). In adults, anti-HA stalk antibodies were independently associated with protection (OR=0.72, 95%CI 0.54-0.95, p=0.02). However, in 0-14-year-olds, anti-NA antibodies (OR=0.67, 95%CI 0.53-0.85, p<0.01) were associated with protection against infection, but anti-HA stalk antibodies were not. CONCLUSIONS: The HA stalk is an independent correlate of protection against A/H3N2 infection, though this association is age dependent. Our results support the continued exploration of the HA stalk as a target for broadly protective influenza vaccines but suggest that the relative benefits may depend on age and influenza virus exposure history.

Obesity is associated with increased pediatric dengue virus infection and disease: A 9-year cohort study in Managua, Nicaragua.

BACKGROUND: Obesity is on the rise globally in adults and children, including in tropical areas where diseases such as dengue have a substantial burden, particularly in children. Obesity impacts the risk of severe dengue disease; however, the impact on dengue virus (DENV) infection and dengue cases remains an open question. METHODS: We used 9 years of data from 5,940 children in the Pediatric Dengue Cohort Study in Nicaragua to examine whether pediatric obesity is associated with increased susceptibility to DENV infection and symptomatic presentation. Analysis was performed using Generalized Estimating Equations adjusted for age, sex, and pre-infection DENV antibody titers. RESULTS: From 2011 to 2019, children contributed 26,273 person-years of observation, and we observed an increase in the prevalence of overweight (from 12% to 17%) and obesity (from 7% to 13%). There were 1,682 DENV infections and 476 dengue cases in the study population. Compared to participants with normal weight, participants with obesity had higher odds of DENV infection (Adjusted Odds Ratio [aOR] 1.21, 95% confidence interval [CI] 1.03-1.42) and higher odds of dengue disease given infection (aOR 1.59, 95% CI 1.15-2.19). Children with obesity infected with DENV showed increased odds of presenting fever (aOR 1.46, 95% CI 1.05-2.02), headache (aOR 1.51, 95% CI 1.07-2.14), and rash (aOR 2.26, 95% CI 1.49-3.44) when compared with children with normal weight. CONCLUSIONS: Our results indicate that obesity is associated with increased susceptibility to DENV infection and dengue cases in children, independently of age, sex, and pre-infection DENV antibody titers.

Correction: SARS-CoV-2 and endemic coronaviruses: Comparing symptom presentation and severity of symptomatic illness among Nicaraguan children.

[This corrects the article DOI: 10.1371/journal.pgph.0000414.].

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.

Obesity is associated with increased pediatric dengue virus infection and disease: A 9-year cohort study in Managua, Nicaragua.

Background: Obesity is on the rise globally in adults and children, including in tropical areas where diseases such as dengue have a substantial burden, particularly in children. Obesity impacts the risk of severe dengue disease; however, the impact on dengue virus (DENV) infection and dengue cases remains an open question. Methods: We used 9 years of data from 5,940 children in the Pediatric Dengue Cohort Study in Nicaragua to examine whether pediatric obesity is associated with increased susceptibility to DENV infection and symptomatic presentation. Analysis was performed using Generalized Estimating Equations adjusted for age, sex, and pre-infection DENV antibody titers. Results: From 2011 to 2019, children contributed 26,273 person-years of observation, and we observed an increase in the prevalence of overweight (from 12% to 17%) and obesity (from 7% to 13%). There were 1,682 DENV infections and 476 dengue cases in the study population. Compared to participants with normal weight, participants with obesity had higher odds of DENV infection (Adjusted Odds Ratio [aOR] 1.21, 95% confidence interval [CI] 1.03-1.42) and higher odds of dengue disease given infection (aOR 1.59, 95% CI 1.15-2.19). Children with obesity infected with DENV showed increased odds of presenting fever (aOR 1.46, 95% CI 1.05-2.02), headache (aOR 1.51, 95% CI 1.07-2.14), and rash (aOR 2.26, 95% CI 1.49-3.44) when compared with children with normal weight. Conclusions: Our results indicate that obesity is associated with increased susceptibility to DENV infection and dengue cases in children, independently of age, sex, and pre-infection DENV antibody titers.

Longitudinal analysis of post-acute chikungunya-associated arthralgia in children and adults: A prospective cohort study in Managua, Nicaragua (2014-2018).

Chikungunya can result in debilitating arthralgia, often presenting as acute, self-limited pain, but occasionally manifesting chronically. Little is known about differences in chikungunya-associated arthralgia comparing children to adults over time. To characterize long-term chikungunya-associated arthralgia, we recruited 770 patients (105 0-4 years old [y/o], 200 5-9 y/o, 307 10-15 y/o, and 158 16+ y/o) with symptomatic chikungunya virus infections in Managua, Nicaragua, during two consecutive chikungunya epidemics (2014-2015). Participants were assessed at ~15 days and 1, 3, 6, 12, and 18 months post-fever onset. Following clinical guidelines, we defined participants by their last reported instance of arthralgia as acute (≤10 days post-fever onset), interim (>10 and <90 days), or chronic (≥90 days) cases. We observed a high prevalence of arthralgia (80-95%) across all ages over the study period. Overall, the odds of acute arthralgia increased in an age-dependent manner, with the lowest odds of arthralgia in the 0-4 y/o group (odds ratio [OR]: 0.27, 95% confidence interval [CI]: 0.14-0.51) and the highest odds of arthralgia in the 16+ y/o participants (OR: 4.91, 95% CI: 1.42-30.95) relative to 10-15 y/o participants. Females had higher odds of acute arthralgia than males (OR: 1.63, 95% CI: 1.01-2.65) across all ages. We found that 23-36% of pediatric and 53% of adult participants reported an instance of post-acute arthralgia. Children exhibited the highest prevalence of post-acute polyarthralgia in their legs, followed by the hands and torso - a pattern not seen among adult participants. Further, we observed pediatric chikungunya presenting in two distinct phases: the acute phase and the subsequent interim/chronic phases. Thus, differences in the presentation of arthralgia were observed across age, sex, and disease phase in this longitudinal chikungunya cohort. Our results elucidate the long-term burden of chikungunya-associated arthralgia among pediatric and adult populations.

Protection against symptomatic dengue infection by neutralizing antibodies varies by infection history and infecting serotype.

Dengue viruses (DENV1-4) are the most prevalent arboviruses in humans and a major public health concern. Understanding immune mechanisms that modulate DENV infection outcome is critical for vaccine development. Neutralizing antibodies (nAbs) are an essential component of the protective immune response, yet their measurement often relies on a single cellular substrate and partially mature virions, which does not capture the full breadth of neutralizing activity and may lead to biased estimations of nAb potency. Here, we analyze 125 samples collected after one or more DENV infections but prior to subsequent symptomatic or inapparent DENV1, DENV2, or DENV3 infections from a long-standing pediatric cohort study in Nicaragua. By assessing nAb responses using Vero cells with or without DC-SIGN and with mature or partially mature virions, we find that nAb potency and the protective NT50 cutoff are greatly influenced by cell substrate and virion maturation state. Additionally, the correlation between nAb titer and protection from disease depends on prior infection history and infecting serotype. Finally, we uncover variations in nAb composition that contribute to protection from symptomatic infection differently after primary and secondary prior infection. These findings have important implications for identifying antibody correlates of protection for vaccines and natural infections.

Anti-Neuraminidase Antibodies Reduce the Susceptibility to and Infectivity of Influenza A/H3N2 Virus.

Immune responses against neuraminidase (NA) are of great interest for developing more robust influenza vaccines, but the role of anti-NA antibodies on influenza infectivity has not been established. We conducted household transmission studies in Managua, Nicaragua to examine the impact of anti-NA antibodies on influenza A/H3N2 susceptibility and infectivity. Analyzing these data with mathematical models capturing household transmission dynamics and their drivers, we estimated that having higher preexisting antibody levels against the hemagglutinin (HA) head, HA stalk, and NA was associated with reduced susceptibility to infection (relative susceptibility 0.67, 95% Credible Interval [CrI] 0.50-0.92 for HA head; 0.59, 95% CrI 0.42-0.82 for HA stalk; and 0.56, 95% CrI 0.40-0.77 for NA). Only anti-NA antibodies were associated with reduced infectivity (relative infectivity 0.36, 95% CrI 0.23-0.55). These benefits from anti-NA immunity were observed even among individuals with preexisting anti-HA immunity. These results suggest that influenza vaccines designed to elicit NA immunity in addition to hemagglutinin immunity may not only contribute to protection against infection but reduce infectivity of vaccinated individuals upon infection.

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 sudy participants 6 months to 17 years old were followed during their hospital stay or as ambulatory patients. RESULTS: We enrolled a total of 15,266 participants, of whom 3,227 (21%) were positive for DENV infection. Of 2,630 cases with serotype result by RT-PCR, 557 corresponded to DENV1, 992 to DENV2, 759 to DENV3 and 322 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.

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

Infection with any of the four dengue virus serotypes (DENV1-4) can protect against or enhance subsequent dengue depending on preexisting antibodies and infecting serotype. Additionally, primary infection with the related flavivirus Zika virus (ZIKV) is associated with increased risk of DENV2 disease. Here, we measured how prior DENV and ZIKV immunity influenced risk of disease caused by DENV1-4 in a pediatric Nicaraguan cohort. Of 3412 participants in 2022, 10.6% experienced dengue cases caused by DENV1 (n = 139), DENV4 (n = 133), DENV3 (n = 54), DENV2 (n = 9), or an undetermined serotype (n = 39). Longitudinal clinical and serological data were used to define infection histories, and generalized linear and additive models adjusted for age, sex, time since last infection, and year, and repeat measurements were used to predict disease risk. Compared with flavivirus-naïve participants, primary ZIKV infection was associated with increased risk of disease caused by DENV4 (relative risk = 2.62, 95% confidence interval: 1.48 to 4.63) and DENV3 (2.90, 1.34 to 6.27), but not DENV1 infection. Primary DENV infection or DENV followed by ZIKV infection was also associated with increased risk of DENV4 disease. We reanalyzed 19 years of cohort data and demonstrated that prior flavivirus immunity and antibody titer had distinct associations with disease risk depending on incoming serotype. We thus find that prior ZIKV infection, like prior DENV infection, is associated with increased risk of disease with certain DENV serotypes. Cross-reactivity among flaviviruses should be considered when assessing vaccine safety and efficacy.