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The American Zika virus (ZIKV) epidemic has highlighted the need to gain a better understanding of this emerging virus. The goal of this study was to describe the clinical symptoms, laboratory findings, and risk factors for symptomatic ZIKV infection in an area with ongoing transmission of other arboviral infections. We recruited patients at least 2 years of age seeking care at public health centers in León, Nicaragua, between January 2016 and August 2017, for fever, maculopapular rash, and/or nonsuppurative conjunctivitis with a duration of less than 1 week. A laboratory diagnosis of ZIKV was established using a combination of molecular and serological tests. Clinical and laboratory findings and potential risk factors were compared between participants with and without acute ZIKV infection. Fifty-eight (26%) of the 225 participants included in the analysis were found to have acute ZIKV infection. Pregnancy and reports of previous arboviral infection were associated with a higher risk of ZIKV infection. Rash, conjunctivitis, sore throat, and lower absolute neutrophil counts were associated with acute ZIKV infection. The clinical characteristics and risk factors identified were consistent with those identified by previous studies; however, we found sore throat to be a feature of ZIKV infection. We also found that neutrophil counts were lower in ZIKV-infected subjects. These clinical symptoms and laboratory data may help clinicians suspect ZIKV infection during future outbreaks.

COVID-19 convalescent plasma (CCP) was an early and widely adopted putative therapy for severe COVID-19. Results from randomized control trials and observational studies have failed to demonstrate a clear therapeutic role for CCP for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Underlying these inconclusive findings is a broad heterogeneity in the concentrations of neutralizing antibodies (nAbs) between different CCP donors. We conducted this study to evaluate the effectiveness and safety of nAb titer-defined CCP in adults admitted to an academic referral hospital. Patients positive by a SARS-CoV-2 nucleic acid amplification test and with symptoms for 1:640 (high-titer group) or ≥1:160 to 1:640 (standard-titer group) in addition to standard of care treatments. The primary clinical outcome was time to hospital discharge, with mortality and respiratory support evaluated as secondary outcomes. Adverse events were contrasted by CCP titer. Between 28 August and 4 December 2020, 316 participants were screened, and 55 received CCP, with 14 and 41 receiving high- versus standard-titer CCP, respectively. Time to hospital discharge was shorter among participants receiving high- versus standard-titer CCP, accounting for death as a competing event (hazard ratio, 1.94; 95% confidence interval [CI], 1.05 to 3.58; Gray’s P = 0.02). Severe adverse events (SAEs) (≥grade 3) occurred in 4 (29%) and 23 (56%) of participants receiving the high versus standard titer, respectively, by day 28 (risk ratio, 0.51; 95% CI, 0.21 to 1.22; Fisher’s P = 0.12). There were no observed treatment-related AEs. (This study has been registered at ClinicalTrials.gov under registration no. NCT04524507).

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused millions of deaths around the world within the past 2 years. Transmission within the United States has been heterogeneously distributed by geography and social factors with little data from North Carolina. Here, we describe results from a weekly cross-sectional study of 12,471 unique hospital remnant samples from 19 April to 26 December 2020 collected by four clinical sites within the University of North Carolina Health system, with a majority of samples from urban, outpatient populations in central North Carolina. We employed a Bayesian inference model to calculate SARS-CoV-2 spike protein immunoglobulin prevalence estimates and conditional odds ratios for seropositivity. Furthermore, we analyzed a subset of these seropositive samples for neutralizing antibodies. We observed an increase in seroprevalence from 2.9 (95% confidence interval [CI], 1.8 to 4.5) to 12.8 (95% CI, 10.6 to 15.2) over the course of the study. Latinx individuals had the highest odds ratio of SARS-CoV-2 exposure at 6.56 (95% CI, 4.66 to 9.44). Our findings aid in quantifying the degree of asymmetric SARS-CoV-2 exposure by ethnoracial grouping. We also find that 49% of a subset of seropositive individuals had detectable neutralizing antibodies, which was skewed toward those with recent respiratory infection symptoms.

Mature DENVs represent the dominant form in vivo and are the target for vaccine development. Here, we used multiple strategies, including protein engineering and natural and directed evolution to generate DENV1, -2, -3, and -4 variants that are highly mature without compromising replication efficiency compared to the parental strains.

The four dengue virus serotypes (DENV1-4) are mosquito-borne flaviviruses of humans. Several live attenuated tetravalent DENV vaccines are at different stages of clinical development and approval. In children with no baseline immunity to DENVs, a leading vaccine (Dengvaxia™) was efficacious against vaccine-matched DENV4 genotype II (GII) strains but not vaccine-mismatched DENV4 genotype I (GI) viruses. We used a panel of recombinant DENV4 viruses displaying GI or GII envelope (E) proteins to map Dengvaxia™ induced neutralizing antibodies (NAb) linked to protection. The vaccine stimulated antibodies that neutralized the DENV4 GII virus better than the GI virus. The neutralization difference mapped to 5 variable amino acids on E protein located within a region targeted by DENV4 NAbs, supporting a mechanistic role for these epitope-specific NAbs in protection. In children with no baseline immunity to DENVs, levels of DENV4 serotype- and genotype-specific NAbs induced by vaccination are predictive of vaccine efficacy.

BackgroundCOVID-19 Convalescent Plasma (CCP) was an early and widely adopted putative therapy for severe COVID-19. Results from randomized control trials and observational studies have failed to demonstrate a clear therapeutic role for CCP for severe SARS-CoV-2 infection. Underlying these inconclusive findings is a broad heterogeneity in the concentrations of neutralizing antibodies (nAb) between different CCP donors. The present study was designed to evaluate nAb titer threshold for clinically effective CCP.MethodsWe conducted a double-blind, phase 2 study to evaluate the safety and effectiveness of nAb titer-defined CCP in adults admitted to an academic referral hospital. Patients positive on a SARS-CoV-2 nucleic acid amplification test and with symptoms for < 10 days were eligible. Participants received either CCP with nAb titers ≥1:160-1:640 (standard titer group) or >1:640 (high titer group) in addition to standard of care treatments. Adverse events were contrasted by CCP titer. The primary clinical outcome was time to hospital discharge, with mortality and respiratory support evaluated as secondary outcomes.FindingsBetween August 28 and December 4, 2020, 316 participants were screened, 55 received CCP, with 41 and 14 receiving standard versus high titer CCP, respectively. Participants were a median of 61 years of age (IQR 52-67), 36% women, 25% Black and 33% Hispanic. Severe adverse events (SAE) (≥ grade 3) occurred in 4 (29%) and 23 (56%) of participants in the high versus standard titer groups, respectively by day 28 (Risk Difference -0.28 [95% CI -0.56, 0.01]). There were no observed treatment-related AEs. By day 55, time to hospital discharge was shorter among participants receiving high versus standard titer, accounting for death as a competing event (hazard ratio 1.94 [95% CI 1.05, 3.58], Gray’s p=0.02).InterpretationIn this phase 2 trial in a high-risk population of patients admitted for Covid-19, we found earlier time to hospital discharge and lower occurrences of life-threatening SAEs among participants receiving CCP with nAb titers >1:640 compared with participants receiving CCP with lower nAb titer CCP. Though limited by a small study size these findings support further study of high-nAb titer CCP defined as >1:640 in the treatment of COVID-19.FundingThis clinical study was supported by the UNC Health Foundation and the North Carolina Policy Collaboratory at the University of North Carolina at Chapel Hill with funding from the North Carolina Coronavirus Relief Fund established and appropriated by the North Carolina General Assembly. The laboratory assays for neutralizing antibody titers and SARS-CoV-2 specific antibody-binding assays were partially supported by The NIH NCI/NIAID SeroNet Serocenter of Excellence Award U54 CA260543.Research in ContextEvidence before this studyCOVID-19 Convalescent Plasma (CCP) has emergency use authorization from the FDA for early treatment of COVID-19 in either outpatient or inpatient settings. Evidence supporting the use of CCP for severe COVID-19 is mixed and still emerging. One major limitation in interpreting published clinical trials and the clinical role of CCP is incomplete understanding of necessary neutralizing antibody (nAb) titer for clinically effective CCP. Observational studies suggest that higher antibody-content CCP is more effective than lower antibody-content CCP, or that very low antibody-content CCP is harmful. We searched PubMed articles published between February 1, 2020, and April 15, 2022, using the terms “COVID-19”, “convalescent plasma”, “SARS-CoV-2”, and “CCP” alone and in combination. Our search yielded 6,468 results which we filtered to 280 and 162 by selecting ‘Clinical Trial’ and ‘Randomized Controlled Trial’ article types, respectively. Among these, we identified 25 open-label or blinded efficacy or effectiveness studies in hospitalized patients that were relevant to our study. Preliminary reports show wide variability in the antibody content of CCP used in clinical trials, the assays used to define CCP antibody content, and the estimates of clinical outcomes following CCP therapy for hospitalized patients. Only one study deliberately infused CCP with nAb > 1:640. Post-hoc analyses of potent monoclonal antibody therapy in hospitalized patients in the UK showed survival benefit when monoclonal antibody was infused to patients who had not yet seroconverted by spike antibody ELISA, suggesting that if dosed appropriately, antibody-based therapies may have a role in improving outcomes of severe COVID-19.Added value of this studyThis phase 2 study showed that CCP with high nAb titer (>1:640) provided more rapid recovery to hospital discharge and fewer COVID-19 attributable AEs than CCP with nAb titer between the FDA-recommended minimum standard and 4-fold higher (≥1:160-1:640). The hazard ratio of time to hospital discharge from baseline through day 55, accounting for death as a competing event, contrasting patients receiving high versus standard CCP titer was 1.94 (95% CI 1.05-3.58). Adjusted hazard ratios of high versus standard titer CCP receipt for time to hospital discharge were consistent with the primary unadjusted findings. Mortality through 55 days was lower in the high titer group, but with a wide confidence interval that did not reach statistical significance.Implications of all available evidenceOur data that CCP with nAb >1:640 expedites recovery of patients admitted with COVID-19 compared with CCP with nAb ≥1:160-1:640 suggests that a threshhold of nAb ≥1:160 may be too low to define CCP as ‘high titer’. Analyses in larger CCP trials should consider full reporting of nAb in CCP units administered at individual study participant level, and specifically whether CCP contained nAb >1:640. Further investigation of CCP with nAb >1:640 is warranted given that raising the threshhold of nAb, or a correlative specific anti-spike antibody assay, used to qualify ‘high titer’ CCP in clinical trials could inform policy guidance and clinical use of CCP.

Objective: To understand the dynamics of Zika virus (ZIKV)-specific antibody immunity in children born to mothers in a flavivirus-endemic region during and after the emergence of ZIKV in the Americas. Methods: We performed serologic testing for ZIKV cross-reactive and type-specific IgG in two longitudinal cohorts, which enrolled pregnant women and their children (PW1 and PW2) after the beginning of the ZIKV epidemic in Nicaragua. Quarterly samples from children over their first two years of life and maternal blood samples at birth and at the end of the two-year follow-up period were studied. Results: Most mothers in this dengue-endemic area were flavivirus-immune at enrollment. ZIKV-specific IgG (anti-ZIKV EDIII IgG) was detected in 82 of 102 (80.4%) mothers in cohort PW1 and 89 of 134 (66.4%) mothers in cohort PW2, consistent with extensive transmission observed in Nicaragua during 2016. ZIKV-reactive IgG decayed to undetectable levels by 6–9 months in infants, whereas these antibodies were maintained in mothers at the year two time point. Interestingly, a greater contribution to ZIKV immunity by IgG3 was observed in babies born soon after ZIKV transmission. Finally, 43 of 343 (13%) children exhibited persistent or increasing ZIKV-reactive IgG at ≥9 months, with 10 of 30 (33%) tested demonstrating serologic evidence of incident dengue infection. Conclusions: These data inform our understanding of protective and pathogenic immunity to potential flavivirus infections in early life in areas where multiple flaviviruses co-circulate, particularly considering the immune interactions between ZIKV and dengue and the future possibility of ZIKV vaccination in women of childbearing potential. This study also shows the benefits of cord blood sampling for serologic surveillance of infectious diseases in resource-limited settings.

Dengue seroprevalence data are useful for understanding epidemiologic trends and transmission dynamics, and for making decisions about implementation of dengue control programs. A logistical challenge to seroprevalence surveys is the collection and transport of serum samples. For conducting large and repeated dengue serosurveys, dried blood spots (DBS) would allow easier sample collection, shipment, transport, and storage than standard serum collection methods. Further evidence is needed to understand how well DBS performs compared with standard serum collection methods in laboratory assays. We evaluated the detection of anti-dengue antibodies by IgG indirect ELISA when using DBS compared with sera. Specimens were collected from healthy children in Cebu, Philippines, who would be 9–14 years of age at the time of a mass dengue vaccination program. Using an ELISA index value cutoff of 0.9, 1,285/1,488 (86.4%) of the DBS were seropositive and 203 (13.6%) were seronegative, compared with 1,292/1,488 (86.8%) seropositive and 196 (13.2%) seronegative serum samples. Compared with sera, the DBS method had a 98.3% sensitivity, 92.4% specificity, 98.9% positive predictive value, and 89.2% negative predictive value. Considering the advantages in terms of sample collection, shipment, and storage, DBS sampling may be appropriate for dengue population serosurveys.

Background Neurodevelopmental outcomes of asymptomatic children exposed to Zika virus (ZIKV) in utero are not well characterized. Methods We prospectively followed 129 newborns without evidence of congenital Zika syndrome (CZS) up to 24 months of age. Participants were classified as ZIKV exposed or ZIKV unexposed. The Mullen Scales of Early Learning (MSEL) was administered in the participants’ homes at 6, 12, 15, 18, 21, and 24 months of age by trained psychologists. Sociodemographic data, medical history, and infant anthropometry at birth were collected at each home visit. Our primary outcome was the Mullen Early Learning Composite Score (ECL) at 24 months of age between our 2 exposure groups. Secondary outcomes were differences in MSEL subscales over time and at 24 months. Results Of 129 infants in whom exposure status could be ascertained, 32 (24.8%) met criteria for in utero ZIKV exposure and 97 (75.2%) did not. There were no differences in maternal age, maternal educational attainment, birthweight, or gestational age at birth between the 2 exposure groups. The adjusted means and standard errors (SEs) for the ELC score between the ZIKV-exposed children compared to ZIKV-unexposed children were 91.4 (SE, 3.1) vs 96.8 (SE, 2.4) at 12 months and 93.3 (SE, 2.9) vs 95.9 (SE, 2.3) at 24 months. In a longitudinal mixed model, infants born to mothers with an incident ZIKV infection (P = .01) and low-birthweight infants (, Children with in utero Zika virus exposure and without congenital Zika syndrome in Nicaragua had lower neurocognitive scores at 24 months. Our study includes multiple evaluations over time and a contemporary nonexposed comparator group of children, which is currently lacking in the literature.

Preexisting immune response to SARS-CoV-2 Robust T cell responses to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus occur in most individuals with coronavirus disease 2019 (COVID-19). Several studies have reported that some people who have not been exposed to SARS-CoV-2 have preexisting reactivity to SARS-CoV-2 sequences. The immunological mechanisms underlying this preexisting reactivity are not clear, but previous exposure to widely circulating common cold coronaviruses might be involved. Mateus et al. found that the preexisting reactivity against SARS-CoV-2 comes from memory T cells and that cross-reactive T cells can specifically recognize a SARS-CoV-2 epitope as well as the homologous epitope from a common cold coronavirus. These findings underline the importance of determining the impacts of preexisting immune memory in COVID-19 disease severity. Science , this issue p. 89

In 2017, a dengue epidemic of unexpected magnitude occurred in Sri Lanka. A total of 186,101 suspected cases and 440 dengue-related deaths occurred. We conducted a comprehensive analysis of this epidemic by comparing national surveillance data for 2017 with data from the preceding 5 years. In all Sri Lanka districts, dengue incidence in 2017 increased significantly over incidence during the previous 5 years. Older schoolchildren and young adults were more clinically symptomatic than those at extremes of age. Limited virologic surveillance showed the dominant circulating variant was dengue virus type 2 cosmopolitan genotype in the most affected district. One quarter of total annual cases were reported 5 weeks after the southwest monsoon started. Changes in vector abundance were not predictive of the increased incidence. Direct government expenditures on dengue control activities in 2017 were US $12.7 million. The lessons learned from this outbreak are useful for other tropical nations facing increasing dengue incidence.

Understanding vaccine-mediated protection against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is critical to overcoming the global coronavirus disease 2019 (COVID-19) pandemic. We investigate mRNA-vaccine-induced antibody responses against the reference strain, seven variants, and seasonal coronaviruses in 168 healthy individuals at three time points: before vaccination, after the first dose, and after the second dose. Following complete vaccination, both naive and previously infected individuals developed comparably robust SARS-CoV-2 spike antibodies and variable levels of cross-reactive antibodies to seasonal coronaviruses. However, the strength and frequency of SARS-CoV-2 neutralizing antibodies in naive individuals were lower than in previously infected individuals. After the first vaccine dose, one-third of previously infected individuals lacked neutralizing antibodies; this was improved to one-fifth after the second dose. In all individuals, neutralizing antibody responses against the Alpha and Delta variants were weaker than against the reference strain. Our findings support future tailored vaccination strategies against emerging SARS-CoV-2 variants as mRNA-vaccine-induced neutralizing antibodies are highly variable among individuals., Graphical abstract, Narowski et al. investigate mRNA-vaccine-induced antibody responses in 168 healthy individuals with longitudinal specimens. After complete vaccination, both previously infected and naive individuals develop comparably robust SARS-CoV-2 spike antibodies. However, neutralizing antibody response to vaccination is variable among these individuals, supporting future tailored vaccination strategies against emerging SARS-CoV-2 variants.

Zika virus (ZIKV) is a member of the Flaviviridae family, which includes other clinically notable viruses such as the 4 dengue virus serotypes (DENV-1–4). Distinguishing DENVs from ZIKV using the established serologic assays widely used for monitoring DENV transmission is difficult because of antibody cross-reactivity between these closely related flaviviruses. We describe a modified and improved recombinant envelope domain III–based serologic assay for detecting ZIKV type-specific antibodies in regions with endemic DENV transmission. When the assay was used to measure ZIKV seroprevalence in 2017 among children 9–14 years of age living in a region of the Philippines with endemic DENV transmission, we observed a ZIKV seroprevalence of 18%. Investigators should consider using the ZIKV envelope domain III–based assay, which is simple and readily adaptable for use in standard clinical and public health laboratories, to assess ZIKV seroprevalence in areas with endemic DENV transmission.

Background Early in the pandemic, transmission risk from asymptomatic infection was unclear, making it imperative to monitor infection in workplace settings. Further, data on SARS-CoV-2 seroprevalence within university populations has been limited. Methods We performed a longitudinal study of University research employees on campus July-December 2020. We conducted questionnaires on COVID-19 risk factors, RT-PCR testing, and SARS-CoV-2 serology using an in-house spike RBD assay, laboratory-based Spike NTD assay, and standard nucleocapsid platform assay. We estimated prevalence and cumulative incidence of seroconversion with 95% confidence intervals using the inverse of the Kaplan-Meier estimator. Results 910 individuals were included in this analysis. At baseline, 6.2% (95% CI 4.29–8.19) were seropositive using the spike RBD assay; four (0.4%) were seropositive using the nucleocapsid assay, and 44 (4.8%) using the Spike NTD assay. Cumulative incidence was 3.61% (95% CI: 2.04–5.16). Six asymptomatic individuals had positive RT-PCR results. Conclusions Prevalence and incidence of SARS-CoV-2 infections were low; however, differences in target antigens of serological tests provided different estimates. Future research on appropriate methods of serological testing in unvaccinated and vaccinated populations is needed. Frequent RT-PCR testing of asymptomatic individuals is required to detect acute infections, and repeated serosurveys are beneficial for monitoring subclinical infection.

Amidst the therapeutic void at the onset of the COVID-19 pandemic, a critical mass of scientific and clinical interest coalesced around COVID-19 convalescent plasma (CCP). To date, the CCP literature has focused largely on safety and efficacy outcomes, but little on implementation outcomes or experience. Expert opinion suggests that if CCP has a role in COVID-19 treatment, it is early in the disease course, and it must deliver a sufficiently high titer of neutralizing antibodies (nAb). Missing in the literature are comprehensive evaluations of how local CCP programs were implemented as part of pandemic preparedness and response, including considerations of the core components and personnel required to meet demand with adequately qualified CCP in a timely and sustained manner. To address this gap, we conducted an evaluation of a local CCP program at a large U.S. academic medical center, the University of North Carolina Medical Center (UNCMC), and patterned our evaluation around the dimensions of the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework to systematically describe key implementation-relevant metrics. We aligned our evaluation with program goals of reaching the target population with severe or critical COVID-19, integrating into the structure of the hospital-wide pandemic response, adapting to shifting landscapes, and sustaining the program over time during a compassionate use expanded access program (EAP) era and a randomized controlled trial (RCT) era. During the EAP era, the UNCMC CCP program was associated with faster CCP infusion after admission compared with contemporaneous affiliate hospitals without a local program: median 29.6 hours (interquartile range, IQR: 21.2–48.1) for the UNCMC CCP program versus 47.6 hours (IQR 32.6–71.6) for affiliate hospitals; (P

Background The natural antibody responses to B-cell epitopes from dengue structural proteins were assessed using immune sera from people having well-defined past dengue infections with one of the four serotypes. Method Based on an immune-computational analysis previously conducted, nineteen epitopes from the envelope (E) and eight epitopes from pre-membrane (prM), which were more than 50% conserved across all the four DENV serotypes, were selected. Peptides to represent these B-cell epitopes were obtained from commercially available arrays, and were subjected to enzyme linked immunosorbent assay with sera obtained from dengue seropositive healthy volunteers (DENV1 n = 12: DENV2 n = 12: DENV3 n = 12 and DENV4 n = 12), and 10 dengue seronegative healthy volunteers from Sri Lanka. The cut-off value for the positive antibody response was set by taking the mean response of a peptide to the negative sera plus three standard deviations. The peptides (N = 7) showing the broad immune responses were used to generate antibodies in three mice (Balb/c) batches. The mice antisera were then subjected to microneutralization assays against all the four DENV serotypes. An EC50 viral neutralization ≥ 40 times the serum dilution was considered as neutralizing. Results Five of the E-peptide and two prM peptides were recognised by most individuls exposed to infections with each of the four serotypes, showing a serotype cross-reactive broad antibody response. The mice immune sera against the peptides representing the five E protein epitopes neutralized all the four DENV serotypes. Two of these five epitopes are from the Domain II, whereas one of them includes the whole bc-loop region. Conclusion The antibody responses of highly conserved epitopes across the serotypes, were broadly responsive with sera of all four DENV serotypes collected from individuals infected with only one DENV serotype. Weakly conserved epitopes showed rather specific antibody responses dominated by one or few serotypes.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has now caused over 2 million deaths worldwide and continues to expand. Currently, much is unknown about functionally neutralizing human antibody responses and durability to SARS-CoV-2 months after infection or the reason for the discrepancy in COVID-19 disease and sex. Using convalescent-phase sera collected from 101 COVID-19-recovered individuals 21 to 212 days after symptom onset with 48 additional longitudinal samples, we measured functionality and durability of serum antibodies. We also evaluated associations of individual demographic and clinical parameters with functional neutralizing antibody responses to COVID-19. We found robust antibody durability out to 6 months, as well as significant positive associations with the magnitude of the neutralizing antibody response and male sex and in individuals with cardiometabolic comorbidities. IMPORTANCE In this study, we found that neutralizing antibody responses in COVID-19-convalescent individuals vary in magnitude but are durable and correlate well with receptor binding domain (RBD) Ig binding antibody levels compared to other SARS-CoV-2 antigen responses. In our cohort, higher neutralizing antibody titers are independently and significantly associated with male sex compared to female sex. We also show for the first time that higher convalescent antibody titers in male donors are associated with increased age and symptom grade. Furthermore, cardiometabolic comorbidities are associated with higher antibody titers independently of sex. Here, we present an in-depth evaluation of serologic, demographic, and clinical correlates of functional antibody responses and durability to SARS-CoV-2 which supports the growing literature on sex discrepancies regarding COVID-19 disease morbidity and mortality, as well as functional neutralizing antibody responses to SARS-CoV-2.

Description, A stabilized dimer of the surface protein from dengue virus has been engineered to elicit antibodies that neutralize the virus., Dengue virus (DENV) is a worldwide health burden, and a safe vaccine is needed. Neutralizing antibodies bind to quaternary epitopes on DENV envelope (E) protein homodimers. However, recombinantly expressed soluble E proteins are monomers under vaccination conditions and do not present these quaternary epitopes, partly explaining their limited success as vaccine antigens. Using molecular modeling, we found DENV2 E protein mutations that induce dimerization at low concentrations (

In a Nicaraguan population-based cohort, SARS-CoV-2 seroprevalence reached 28% in the first 6 months of the country's epidemic and reached 35% 6 months later. Immune waning was uncommon. Individuals with a seropositive household member were over three times as likely to be seropositive themselves, suggesting the importance of household transmission.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has now caused over 2 million deaths worldwide and continues to expand. Currently, much is unknown about functionally neutralizing human antibody responses and durability to SARS-CoV-2 months after infection or the reason for the discrepancy in COVID-19 disease and sex. Using convalescent-phase sera collected from 101 COVID-19-recovered individuals 21 to 212 days after symptom onset with 48 additional longitudinal samples, we measured functionality and durability of serum antibodies. We also evaluated associations of individual demographic and clinical parameters with functional neutralizing antibody responses to COVID-19. We found robust antibody durability out to 6 months, as well as significant positive associations with the magnitude of the neutralizing antibody response and male sex and in individuals with cardiometabolic comorbidities. IMPORTANCE In this study, we found that neutralizing antibody responses in COVID-19-convalescent individuals vary in magnitude but are durable and correlate well with receptor binding domain (RBD) Ig binding antibody levels compared to other SARS-CoV-2 antigen responses. In our cohort, higher neutralizing antibody titers are independently and significantly associated with male sex compared to female sex. We also show for the first time that higher convalescent antibody titers in male donors are associated with increased age and symptom grade. Furthermore, cardiometabolic comorbidities are associated with higher antibody titers independently of sex. Here, we present an in-depth evaluation of serologic, demographic, and clinical correlates of functional antibody responses and durability to SARS-CoV-2 which supports the growing literature on sex discrepancies regarding COVID-19 disease morbidity and mortality, as well as functional neutralizing antibody responses to SARS-CoV-2.

With the advance of SARS-CoV-2 vaccines, the outlook for overcoming the global COVID-19 pandemic has improved. However, understanding of immunity and protection offered by the SARS-CoV-2 vaccines against circulating variants of concern (VOC) is rapidly evolving. We investigated the mRNA vaccine-induced antibody responses against the referent WIV04 (Wuhan) strain, circulating variants, and human endemic coronaviruses in 168 naïve and previously infected people at three-time points. Samples were collected prior to vaccination, after the first and after the second doses of one of the two available mRNA-based vaccines. After full vaccination, both naïve and previously infected participants developed comparable robust SARS-CoV-2 specific spike IgG levels, modest IgM and IgA binding antibodies, and varying degrees of HCoV cross-reactive antibodies. However, the strength and frequency of neutralizing antibodies produced in naïve people were significantly lower than in the previously infected group. We also found that 1/3rdof previously infected people had undetectable neutralizing antibodies after the first vaccine dose; 40% of this group developed neutralizing antibodies after the second dose. In all subjects neutralizing antibodies produced against the B.1.351 and P.1 variants were weaker than those produced against the reference and B.1.1.7 strains. Our findings provide support for future booster vaccinations modified to be active against the circulating variants.

Zika virus (ZIKV) and dengue virus (DENV) are co-endemic in many parts of the world, but the impact of ZIKV infection on subsequent DENV infection is not well understood. Here we show in rhesus macaques that the time elapsed after ZIKV infection affects the immune response to DENV infection. We show that previous ZIKV exposure increases the magnitude of the antibody and T cell responses against DENV. The time interval between ZIKV and subsequent DENV infection further affects the immune response. A mid-convalescent period of 10 months after ZIKV infection results in higher and more durable antibody and T cell responses to DENV infection than a short period of 2 months. In contrast, previous ZIKV infection does not affect DENV viremia or pro-inflammatory status. Collectively, we find no evidence of a detrimental effect of ZIKV immunity in a subsequent DENV infection. This supports the implementation of ZIKV vaccines that could also boost immunity against future DENV epidemics., Here, the authors show that the time elapsed between Zika infection and subsequent dengue virus infection affects the magnitude and durability of the antibody and cell-mediated immune responses against dengue virus, but not viremia. This research in non-human primates has implications for co-endemic regions and vaccination.

Background Acute viral infections induce a rapid and transient increase in antibody-secreting plasmablasts. At convalescence, memory B cells (MBC) and long-lived plasma cells (LLPC) are responsible for long-term humoral immunity. Following an acute viral infection, the specific properties and relationships between antibodies produced by these B cell compartments are poorly understood. Methods We utilized a controlled human challenge model of primary dengue virus serotype 2 (DENV2) infection to study acute and convalescent B-cell responses. Findings The level of DENV2 replication was correlated with the magnitude of the plasmablast response. Functional analysis of plasmablast-derived monoclonal antibodies showed that the DENV2-specific response was dominated by cells producing DENV2 serotype-specific antibodies. DENV2-neutralizing antibodies targeted quaternary structure epitopes centered on domain III of the viral envelope protein (EDIII). Functional analysis of MBC and serum antibodies from the same subjects six months post-challenge revealed maintenance of the serotype-specific response in both compartments. The serum response mainly targeted DENV2 serotype-specific epitopes on EDIII. Interpretation Our data suggest overall functional alignment of DENV2-specific responses from the plasmablast, through the MBC and LLPC compartments following primary DENV2 inflection. These results provide enhanced resolution of the temporal and specificity of the B cell compartment in viral infection and serve as framework for evaluation of B cell responses in challenge models. Funding This study was supported by the Bill and Melinda Gates Foundation and the National Institutes of Health.

Background: Acute viral infections induce a rapid and transient increase in antibody-secreting plasmablasts. At convalescence, memory B cells (MBC) and long-lived plasma cells (LLPC) are responsible for long-term humoral immunity. Following an acute viral infection, the specific properties and relationships between antibodies produced by these B cell compartments are poorly understood. Methods: We utilized a controlled human challenge model of primary dengue virus serotype 2 (DENV2) infection to study acute and convalescent B-cell responses. Findings: The level of DENV2 replication was correlated with the magnitude of the plasmablast response. Functional analysis of plasmablast-derived monoclonal antibodies showed that the DENV2-specific response was dominated by cells producing DENV2 serotype-specific antibodies. DENV2-neutralizing antibodies targeted quaternary structure epitopes centered on domain III of the viral envelope protein (EDIII). Functional analysis of MBC and serum antibodies from the same subjects six months post-challenge revealed maintenance of the serotype-specific response in both compartments. The serum response mainly targeted DENV2 serotype-specific epitopes on EDIII. Interpretation: Our data suggest overall functional alignment of DENV2-specific responses from the plasmablast, through the MBC and LLPC compartments following primary DENV2 inflection. These results provide enhanced resolution of the temporal and specificity of the B cell compartment in viral infection and serve as framework for evaluation of B cell responses in challenge models. Funding: This study was supported by the Bill and Melinda Gates Foundation and the National Institutes of Health. Keywords: Dengue, Viral infection, Humoral immunity, Antibody

National Institutes of Health monovalent dengue vaccines and natural primary dengue virus infections elicit serotype-specific neutralizing antibodies that recognize similar epitopes., Background Dengue virus is an emerging mosquito-borne flavivirus responsible for considerable morbidity and mortality worldwide. The Division of Intramural Research, National Institute of Allergy and Infectious Diseases of the US National Institutes of Health (NIH) has developed live attenuated vaccines to each of the 4 serotypes of dengue virus (DENV1–4). While overall levels of DENV neutralizing antibodies (nAbs) in humans have been correlated with protection, these correlations vary depending on DENV serotype, prevaccination immunostatus, age, and study site. By combining both the level and molecular specificity of nAbs to each serotype, it may be possible to develop more robust correlates that predict long-term outcome. Methods Using depletions and recombinant chimeric epitope transplant DENVs, we evaluate the molecular specificity and mapped specific epitopes and antigenic regions targeted by vaccine-induced nAbs in volunteers who received the NIH monovalent vaccines against each DENV serotype. Results After monovalent vaccination, subjects developed high levels of nAbs that mainly targeted epitopes that are unique (type-specific) to each DENV serotype. The DENV1, 2, and 4 monovalent vaccines induced type-specific nAbs directed to quaternary structure envelope epitopes known to be targets of strongly neutralizing antibodies induced by wild-type DENV infections. Conclusions Our results reported here on the molecular specificity of NIH vaccine–induced antibodies enable new strategies, beyond the absolute levels of nAbs, for determining correlates and mechanisms of protective immunity.

Dengue viruses (DENV serotypes 1-4) and Zika virus (ZIKV) are related flaviviruses that continue to be a public health concern, infecting hundreds of millions of people annually. The traditional live-attenuated virus vaccine approach has been challenging for the four DENV serotypes because of the need to achieve balanced replication of four independent vaccine components. Subunit vaccines represent an alternative approach that may circumvent problems inherent with live-attenuated DENV vaccines. In mature virus particles, the envelope (E) protein forms a homodimer that covers the surface of the virus and is the major target of neutralizing antibodies. Many neutralizing antibodies bind to quaternary epitopes that span across both E proteins in the homodimer. For soluble E (sE) protein to be a viable subunit vaccine, the antigens should be easy to produce and retain quaternary epitopes recognized by neutralizing antibodies. However, WT sE proteins are primarily monomeric at conditions relevant for vaccination and exhibit low expression yields. Previously, we identified amino acid mutations that stabilize the sE homodimer from DENV2 and dramatically raise expression yields. Here, we tested whether these same mutations raise the stability of sE from other DENV serotypes and ZIKV. We show that the mutations raise thermostability for sE from all the viruses, increase production yields from 4-fold to 250-fold, stabilize the homodimer, and promote binding to dimer-specific neutralizing antibodies. Our findings suggest that these sE variants could be valuable resources in the efforts to develop effective subunit vaccines for DENV serotypes 1 to 4 and ZIKV.

New information is emerging about SARS-CoV-2 epidemiology and immunity, but little of this information comes from low- and middle-income countries or from patients receiving care in the outpatient setting. The current study investigated the SARS-CoV-2 infection status and antibody responses in 157 patients seeking care for a respiratory disease suggestive of COVID-19 in private healthcare clinics during the first wave (June–October 2020) of infections in Nicaragua. We examined nasal swabs for the presence of viral RNA via RT-PCR and longitudinally collected sera for the changes in SARS-CoV-2 Spike antibody levels over six months. Among patients with confirmed SARS-CoV-2 infections, we evaluated if clinical symptoms were associated with age, hematological parameters and co-morbidities. The combination of PCR and paired serology identified 60 (38%) of the 157 outpatients as acute COVID-19. While both PCR and serology identified the majority (n = 38, 64%) of the acute infections, a notable number of outpatients were identified by RT-qPCR (n = 13, 22%) or by serology (n = 9, 14%) only. During the longitudinal study, we identified 6 new infections by serology among the 97 non-COVID-19 subjects. In conclusion, this study report that more than one third of the outpatients seeking care for acute respiratory disease during the first epidemic wave of SARS-CoV-2 in Nicaragua had an acute mild COVID-19 infection that correlate with prolonged humoral response. This immune response to the RBD antigen, more likely IgG dependent, significantly increased between the acute to convalescent and decay in the late convalescent but still remained seropositive.

BackgroundRobust community-level SARS-CoV-2 prevalence estimates have been difficult to obtain in the American South and outside of major metropolitan areas. Furthermore, though some previous studies have investigated the association of demographic factors such as race with SARS-CoV-2 exposure risk, fewer have correlated exposure risk to surrogates for socioeconomic status such as health insurance coverage.MethodsWe used a highly specific serological assay utilizing the receptor binding domain of the SARS-CoV-2 spike-protein to identify SARS-CoV-2 antibodies in remnant blood samples collected by the University of North Carolina Health system. We estimated the prevalence of SARS-CoV-2 in this cohort with Bayesian regression, as well as the association of critical demographic factors with higher prevalence odds.FindingsBetween April 21st and October 3rd of 2020, a total of 9,624 unique samples were collected from clinical sites in central NC and we observed a seroprevalence increase from 2·9 (1·7, 4·3) to 9·1 (7·2, 11·1) over the study period. Individuals who identified as Latinx were associated with the highest odds ratio of SARS-CoV-2 exposure at 7·77 overall (5·20, 12·10). Increased odds were also observed among Black individuals and individuals without public or private health insurance.InterpretationOur data suggests that for this care-accessing cohort, SARS-CoV-2 seroprevalence was significantly higher than cumulative total cases reported for the study geographical area six months into the COVID-19 pandemic in North Carolina. The increased odds of seropositivity by ethnoracial grouping as well as health insurance highlights the urgent and ongoing need to address underlying health and social disparities in these populations.RESEARCH IN CONTEXTEvidence before this studyWe searched PubMed for studies published through March 21st, 2021. We used search terms that included “COVID-19”, “SARS-CoV-2”, “prevalence” and “seroprevalence”. Our search resulted in 399 papers, from which we identified 58 relevant studies describing SARS-CoV-2 seroprevalence at sites around the United States from March 1 to December 9, 2020, 12 of which utilized remnant clinical samples and three of which overlapped with our study area. Most notably, one study of 4,422 asymptomatic inpatients and outpatients in central NC from April 28-June 19, 2020 found an estimated seroprevalence of 0·7 −0·8%, and another study of 177,919 inpatients and outpatients (3,817 from NC) from July 27-September 24, 2020 found an estimated seroprevalence of 2·5 −6·8%.Added value of this studyThis is the largest SARS-CoV-2 seroprevalence cohort published to date in NC. Importantly, we used a Bayesian framework to account for uncertainty in antibody assay sensitivity and specificity and investigated seropositivity by important demographic variables that have not yet been studied in this context in NC. This study corroborates other reports that specific demographic factors including race, ethnicity and the lack of public or private insurance are associated with elevated risk of SARS-CoV-2 infection. Furthermore, in a subset of serum samples, we identify other SARS-CoV-2 antibodies elicited by these individuals, including functionally neutralizing antibodies.Implications of all the available evidenceIt is difficult to say the exact seroprevalence in the central North Carolina area, but a greater proportion of the population accessing healthcare has been infected by SARS-CoV-2 than is reflected by infection cases confirmed by molecular testing. Furthermore, local governments need to prioritize addressing the many forms of systemic racism and socioeconomic disadvantage that drive SARS-CoV-2 exposure risk, such as residential and occupational risk, and an urgent need to provide access to SARS-CoV-2 testing and vaccination to these groups.

In a Nicaraguan population-based cohort, SARS-CoV-2 seroprevalence was 34%, with higher prevalence in children compared to adults. Having a seropositive household member was associated with a two-fold probability of individual seropositivity, suggesting a role for household transmission. Co-morbidities and preventive behaviors were not associated with SARS-CoV-2 seroprevalence.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) has now caused over 2 million deaths worldwide and continues to expand. Currently, much is unknown about functionally neutralizing human antibody responses and durability to SARS-CoV-2. Using convalescent sera collected from 101 COVID-19 recovered individuals 21-212 days after symptom onset with forty-eight additional longitudinal samples, we measured functionality and durability of serum antibodies. We also evaluated associations between individual demographic and clinical parameters with functional neutralizing antibody responses to COVID-19. We found robust antibody durability out to six months, as well as significant positive associations with the magnitude of the neutralizing antibody response and male sex. We also show that SARS-CoV-2 convalescent neutralizing antibodies are higher in individuals with cardio-metabolic comorbidities.SignificanceIn this study we found that neutralizing antibody responses in COVID-19 convalescent individuals vary in magnitude but are durable and correlate well with RBD Ig binding antibody levels compared to other SARS-CoV-2 antigen responses. In our cohort, higher neutralizing antibody titers are independently and significantly associated with male sex compared to female sex. We also show for the first time, that higher convalescent antibody titers in male donors are associated with increased age and symptom grade. Furthermore, cardio-metabolic co-morbidities are associated with higher antibody titers independently of sex. Here, we present an in-depth evaluation of serologic, demographic, and clinical correlates of functional antibody responses and durability to SARS-CoV-2.

People infected with Zika virus develop durable neutralizing antibodies that prevent repeat infections. In the current study, we characterize a ZIKV-neutralizing human monoclonal antibody isolated from a patient after recovery. Our studies establish a novel site on the viral envelope that is targeted by human neutralizing antibodies. Our results are relevant to understanding how antibodies block infection and to guiding the design and evaluation of candidate vaccines., Zika virus (ZIKV), a mosquito-transmitted flavivirus, caused a large epidemic in Latin America between 2015 and 2017. Effective ZIKV vaccines and treatments are urgently needed to prevent future epidemics and severe disease sequelae. People infected with ZIKV develop strongly neutralizing antibodies linked to viral clearance and durable protective immunity. To understand the mechanisms of protective immunity and to support the development of ZIKV vaccines, we characterize here a strongly neutralizing antibody, B11F, isolated from a patient who recovered from ZIKV. Our results indicate that B11F targets a complex epitope on the virus that spans domains I and III of the envelope glycoprotein. While previous studies point to quaternary epitopes centered on domain II of the ZIKV E glycoprotein as targets of strongly neutralizing and protective human antibodies, we uncover a new site spanning domains I and III as a target of strongly neutralizing human antibodies. IMPORTANCE People infected with Zika virus develop durable neutralizing antibodies that prevent repeat infections. In the current study, we characterize a ZIKV-neutralizing human monoclonal antibody isolated from a patient after recovery. Our studies establish a novel site on the viral envelope that is targeted by human neutralizing antibodies. Our results are relevant to understanding how antibodies block infection and to guiding the design and evaluation of candidate vaccines.

Changing with the timesPandemic spread of a virus in naïe populations can select for mutations that alter pathogenesis, virulence, and/or transmissibility. The ancestral form of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that emerged from China has now been largely replaced by strains containing the mutation D614G (Asp614-to-Gly) in the viral spike protein. Houet al.compared the characteristics of the new variant against the ancestral form in a series of experiments in human cells and animal models. The variant is better at infecting upper-airway epithelial cells and replicates in greater numbers than the ancestral virus. Evidence indicates modest, if any, significant changes to virulence in animal models. Therefore, the virus appears to have evolved for greater transmissibility in humans rather than for greater pathogenicity. The mutation renders the new virus variant more susceptible to neutralizing antisera without altering the efficacy of vaccine candidates currently under development.Science, this issue p.1464