Hybrid Immunity Results in Enhanced and More Sustained Antibody Responses after the Second Sinovac-CoronaVac Dose in a Brazilian Cohort: DETECTCoV-19 Cohort.

We measured anti-SARS-CoV-2 antibody responses before and after CoronaVac (inactivated) vaccination in a case-control study performed in CoronaVac-immunized individuals participating in a longitudinal prospective study of adults in Manaus (DETECTCoV-19). Antibody responses were measured by standard serological immunoassays. Peak anti-S-RBD and neutralizing RBD-ACE2 blocking antibody responses after two doses of CoronaVac vaccine were similar in vaccine breakthrough cases (n = 9) and matched controls (n = 45). Individuals with hybrid immunity resulting from prior SARS-CoV-2 infection followed by vaccination (n = 22) had elevated levels of anti-N, anti-S-RBD and RBD-ACE2 blocking antibodies after the second vaccine dose compared to infection-naïve individuals (n = 48). Post-vaccination SARS-CoV-2-specific antibody responses rapidly waned in infection-naïve individuals. Antibody responses wane after vaccination, making individuals susceptible to infection by SARS-CoV-2 variants. These findings support the need for booster doses after primary vaccination. Population antibody serosurveys provide critical information toward implementing optimal timing of booster doses.

Antibody cross-reactivity and evidence of susceptibility to emerging Flaviviruses in the dengue-endemic Brazilian Amazon.

OBJECTIVES: Several Flaviviruses can co-circulate. Pre-existing immunity to one virus can modulate the response to a heterologous virus; however, the serological cross-reaction between these emerging viruses in dengue virus (DENV)-endemic regions are poorly understood. METHODS: A cross-sectional study was performed among the residents of Manaus city in the state of Amazonas, Brazil. The serological response was assessed by hemagglutination inhibition assay (HIA), enzyme-linked immunosorbent assay, and neutralization assay. RESULTS: A total of 74.52% of the participants were immunoglobulin G-positive (310/416), as estimated by lateral flow tests. Overall, 93.7% of the participants were seropositive (419/447) for at least one DENV serotype, and the DENV seropositivity ranged between 84.8% and 91.0%, as determined by HIA. About 93% had antiyellow fever virus 17D-reactive antibodies, whereas 80.5% reacted to wild-type yellow fever virus. Zika virus (ZIKV) had the lowest seropositivity percentage (52.6%) compared with other Flaviviruses. Individuals who were DENV-positive with high antibody titers by HIA or envelope protein domain III enzyme-linked immunosorbent assay reacted strongly with ZIKV, whereas individuals with low anti-DENV antibody titers reacted poorly toward ZIKV. Live virus neutralization assay with ZIKV confirmed that dengue serogroup and ZIKV-spondweni serogroup are far apart; hence, individuals who are DENV-positive do not cross-neutralize ZIKV efficiently. CONCLUSION: Taken together, we observed a high prevalence of DENV in the Manaus-Amazon region and a varying degree of cross-reactivity against emerging and endemic Flaviviruses. Epidemiological and exposure conditions in Manaus make its population susceptible to emerging and endemic arboviruses.

Antigen-Specific Antibody Signature Is Associated with COVID-19 Outcome.

Numerous studies have focused on inflammation-related markers to understand COVID-19. In this study, we performed a comparative analysis of spike (S) and nucleocapsid (N) protein-specific IgA, total IgG and IgG subclass response in COVID-19 patients and compared this to their disease outcome. We observed that the SARS-CoV-2 infection elicits a robust IgA and IgG response against the N-terminal (N1) and C-terminal (N3) region of the N protein, whereas we failed to detect IgA antibodies and observed a weak IgG response against the disordered linker region (N2) in COVID-19 patients. N and S protein-specific IgG1, IgG2 and IgG3 response was significantly elevated in hospitalized patients with severe disease compared to outpatients with non-severe disease. IgA and total IgG antibody reactivity gradually increased after the first week of symptoms. Magnitude of RBD-ACE2 blocking antibodies identified in a competitive assay and neutralizing antibodies detected by PRNT assay correlated with disease severity. Generally, the IgA and total IgG response between the discharged and deceased COVID-19 patients was similar. However, significant differences in the ratio of IgG subclass antibodies were observed between discharged and deceased patients, especially towards the disordered linker region of the N protein. Overall, SARS-CoV-2 infection is linked to an elevated blood antibody response in severe patients compared to non-severe patients. Monitoring of antigen-specific serological response could be an important tool to accompany disease progression and improve outcomes.

An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination.

The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3',5,5'-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000-1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction.

Prevalence of arbovirus antibodies in young healthy adult population in Brazil.

BACKGROUND: The emergence and re-emergence of infectious diseases are a cause for worldwide concern. The introduction of Zika and Chikungunya diseases in the Americas has exposed unforeseen medical and logistical challenges for public health systems. Moreover, the lack of preventive measures and vaccination against known and emerging mosquito-transmitted pathogens, and the occurrence of unanticipated clinical complications, has had an enormous social and economic impact on the affected populations. In this study, we aimed to measure the seroprevalence of endemic and emerging viral pathogens in military personnel stationed in Manaus, Amazonas state. METHODS: We measured the seropositivity of antibodies against 19 endemic and emerging viruses in a healthy military personnel group using a hemagglutination inhibition assay (HIA). RESULTS: Overall, DENV positivity was 60.4%, and 30.9% of the individuals reacted against ZIKV. Also, 46.6%, 54.7%, 51.3% and 48.7% individuals reacted against West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), Ilheus virus (ILHV) and Rocio virus (ROCV), respectively. Individuals with high DENV HIA titer reacted more frequently with ZIKV or WNV compared to those with low HIA titers. Observed cross-reactivity between Flaviviruses varied depending on the virus serogroup. Additionally, 0.6% and 0.3% individuals were seropositive for Oropouche virus (OROV) and Catu virus (CATUV) from the family Peribunyaviridae, respectively. All samples were negative for Eastern Equine Encephalitis virus (EEEV), Western Equine Encephalomyelitis virus (WEEV), Mayaro virus (MAYV), Mucambo virus (MUCV) and CHIKV from the family Togaviridae. CONCLUSIONS: A high proportion of individuals in our high-risk population (~ 60%) lacked antibodies against major endemic and emerging viruses, which makes them susceptible for further infections. Military personnel serving in the Amazon region could serve as sentinels to strengthen global infectious disease surveillance, particularly in remote areas.

SARS-CoV-2 seroprevalence and associated factors in Manaus, Brazil: baseline results from the DETECTCoV-19 cohort study.

BACKGROUND: Manaus, located in the Brazilian rainforest, has experienced two health system collapses due to the coronavirus disease 2019 (COVID-19) pandemic. However, little is known about which groups among the general population have been most affected. METHODS: A convenience sampling strategy via online advertising recruited 3046 adults between 19 August 2020 and 2 October 2020. Sociodemographic characteristics, COVID-19-related symptoms, COVID-19 testing, self-medication and prescribed medications were recorded. Serum anti-severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) nucleocapsid immunoglobulin G antibodies were measured with an enzyme-linked immunosorbent assay. Prevalence ratios (PR) were obtained using cluster-corrected and adjusted Poisson's regression models. RESULTS: A crude positivity rate among asymptomatic and symptomatic individuals was estimated at 29.10%, with maximum possible seroprevalence of 44.82% corrected by test characteristics and an antibody decay rate of 32.31%. Regression models demonstrated a strong association towards marginalized low-income and vulnerable residents with limited access to health care. The presence of a COVID-19 case [PR 1.39, 95% confidence interval (CI) 1.24-1.57] or death (PR 2.14, 95% CI 1.74-2.62) in a household greatly increased the risk of other household members acquiring infection. The seroprevalence of SARS-CoV-2 was higher among those who self-medicated to prevent infection (PR 1.36, 95% CI 1.27-1.46). CONCLUSIONS: Disproportionate socio-economic disparity was observed among the study participants. The syndemic nature of COVID-19 in the Amazon region needs differential policies and urgent solutions to control the ongoing pandemic.

High anti-SARS-CoV-2 antibody seroconversion rates before the second wave in Manaus, Brazil, and the protective effect of social behaviour measures: results from the prospective DETECTCoV-19 cohort.

BACKGROUND: The city of Manaus, Brazil, has seen two collapses of the health system due to the COVID-19 pandemic. We report anti-SARS-CoV-2 nucleocapsid IgG antibody seroconversion rates and associated risk factors in Manaus residents before the second wave of the epidemic in Brazil. METHODS: A convenience sample of adult (aged ≥18 years) residents of Manaus was recruited through online and university website advertising into the DETECTCoV-19 study cohort. The current analysis of seroconversion included a subgroup of DETECTCoV-19 participants who had at least two serum sample collections separated by at least 4 weeks between Aug 19 and Oct 2, 2020 (visit 1), and Oct 19 and Nov 27, 2020 (visit 2). Those who reported (or had no data on) having a COVID-19 diagnosis before visit 1, and who were positive for anti-SARS-CoV-2 nucleocapsid IgG antibodies at visit 1 were excluded. Using an in-house ELISA, the reactivity index (RI; calculated as the optical density ratio of the sample to the negative control) for serum anti-SARS-CoV-2 nucleocapsid IgG antibodies was measured at both visits. We calculated the incidence of seroconversion (defined as RI values ≤1·5 at visit 1 and ≥1·5 at visit 2, and a ratio >2 between the visit 2 and visit 1 RI values) during the study period, as well as incidence rate ratios (IRRs) through cluster-corrected and adjusted Poisson regression models to analyse associations between seroconversion and variables related to sociodemographic characteristics, health access, comorbidities, COVID-19 exposure, protective behaviours, and symptoms. FINDINGS: 2496 DETECTCoV-19 cohort participants returned for a follow-up visit between Oct 19 and Nov 27, 2020, of whom 204 reported having COVID-19 before the first visit and 24 had no data regarding previous disease status. 559 participants were seropositive for anti-SARS-CoV-2 nucleocapsid IgG antibodies at baseline. Of the remaining 1709 participants who were seronegative at baseline, 71 did not meet the criteria for seroconversion and were excluded from the analyses. Among the remaining 1638 participants who were seronegative at baseline, 214 showed seroconversion at visit 2. The seroconversion incidence was 13·06% (95% CI 11·52-14·79) overall and 6·78% (5·61-8·10) for symptomatic seroconversion, over a median follow-up period of 57 days (IQR 54-61). 48·1% of seroconversion events were estimated to be asymptomatic. The sample had higher proportions of affluent and higher-educated people than those reported for the Manaus city population. In the fully adjusted and corrected model, risk factors for seroconversion before visit 2 were having a COVID-19 case in the household (IRR 1·49 [95% CI 1·21-1·83]), not wearing a mask during contact with a person with COVID-19 (1·25 [1·09-1·45]), relaxation of physical distancing (1·31 [1·05-1·64]), and having flu-like symptoms (1·79 [1·23-2·59]) or a COVID-19 diagnosis (3·57 [2·27-5·63]) between the first and second visits, whereas working remotely was associated with lower incidence (0·74 [0·56-0·97]). INTERPRETATION: An intense infection transmission period preceded the second wave of COVID-19 in Manaus. Several modifiable behaviours increased the risk of seroconversion, including non-compliance with non-pharmaceutical interventions measures such as not wearing a mask during contact, relaxation of protective measures, and non-remote working. Increased testing in high-transmission areas is needed to provide timely information about ongoing transmission and aid appropriate implementation of transmission mitigation measures. FUNDING: Ministry of Education, Brazil; Fundação de Amparo à Pesquisa do Estado do Amazonas; Pan American Health Organization (PAHO)/WHO.

SARS-CoV-2 seroprevalence and associated factors in Manaus, Brazil: baseline results from the DETECTCoV-19 cohort study

Antecedentes: Manaus, localizada na floresta tropical brasileira, passou por dois colapsos do sistema de saúde devido à pandemia da doença de coronavírus 2019 (COVID-19). No entanto, pouco se sabe sobre quais grupos entre a população em geral foram os mais afetados. Métodos: Uma estratégia de amostragem de conveniência por meio de publicidade online recrutou 3.046 adultos entre 19 de agosto de 2020 e 2 de outubro de 2020. Características sociodemográficas, sintomas relacionados ao COVID-19, COVID-19 testes, automedicação e medicamentos prescritos foram registrados. Soro anti-respiratório agudo grave anticorpos da imunoglobulina G do nucleocapsídeo da síndrome coronavírus-2 (SARS-CoV-2) foram medidos com um ensaio imunossorvente ligado a enzima. As razões de prevalência (RP) foram obtidas usando correção de cluster e modelos de regressão de Poisson ajustados. Resultados: A taxa bruta de positividade entre indivíduos assintomáticos e sintomáticos foi estimada em 29,10%, com soroprevalência máxima possível de 44,82% corrigida pelas características do teste e taxa de decaimento de anticorpos de 32,31%. Os modelos de regressão demonstraram uma forte associação com os marginalizados. moradores de baixa renda e vulneráveis ​​com acesso limitado aos cuidados de saúde. A presença de um COVID-19 caso [RP 1,39, intervalo de confiança de 95% (IC) 1,24­1,57] ou morte (RP 2,14, IC 95% 1,74­2,62) em uma família aumentou muito o risco de outros membros da família adquirirem infecção. A soroprevalência de O SARS-CoV-2 foi maior entre aqueles que se automedicaram para prevenir a infecção (PR 1,36, IC 95% 1,27­1,46). Conclusões: Observou-se disparidade socioeconômica desproporcional entre os participantes do estudo. O natureza sindêmica do COVID-19 na região amazônica precisa de políticas diferenciadas e soluções urgentes para controlar a pandemia em curso.

High anti-SARS-CoV-2 antibody seroconversion rates before the second wave in Manaus, Brazil, and the protective effect of social behaviour measures: results from the prospective DETECTCoV-19 cohort

Antecedentes: A cidade de Manaus, Brasil, viu dois colapsos do sistema de saúde devido à pandemia de COVID-19. Relatamos as taxas de soroconversão de anticorpos IgG do nucleocapsídeo anti-SARS-CoV-2 e fatores de risco associados em Manaus residentes antes da segunda onda da epidemia no Brasil. Métodos: Uma amostra de conveniência de adultos (idade ≥18 anos) residentes de Manaus foi publicidade do site da universidade na coorte do estudo DETECTCoV-19. A análise atual de soroconversão incluiu um subgrupo de participantes do DETECTCoV-19 que teve pelo menos duas coletas de amostras de soro separadas por pelo menos 4 semanas entre 19 de agosto e 2 de outubro de 2020 (visita 1) e 19 de outubro e 27 de novembro de 2020 (visita 2). Aqueles que relataram (ou tiveram sem dados sobre) ter um diagnóstico de COVID-19 antes da visita 1 e que foram positivos para IgG de nucleocapsídeo anti-SARS-CoV-2 anticorpos na visita 1 foram excluídos. Usando um ELISA interno, o índice de reatividade (RI; calculado como a densidade óptica proporção da amostra para o controle negativo) para anticorpos IgG anti-nucleocapsídeo anti-SARS-CoV-2 sérico foi medido em ambas as visitas. Calculamos a incidência de soroconversão (definida como valores de RI ≤1·5 na visita 1 e ≥1·5 na visita 2, e uma razão >2 entre os valores de IR da visita 2 e da visita 1) durante o período do estudo, bem como taxas de incidência (IRRs) por meio de modelos de regressão de Poisson corrigidos por cluster e ajustados para analisar associações entre soroconversão e variáveis ​​relacionadas a características sociodemográficas, acesso à saúde, comorbidades, exposição à COVID-19, comportamentos protetores e sintomas. Resultados: 2.496 participantes da coorte DETECTCoV-19 retornaram para uma visita de acompanhamento entre 19 de outubro e 27 de novembro de 2020, de dos quais 204 relataram ter COVID-19 antes da primeira visita e 24 não tinham dados sobre o status anterior da doença. 559 participantes foram soropositivos para anticorpos anti-SARS-CoV-2 nucleocapsid IgG na linha de base. Do restante 1.709 participantes que eram soronegativos no início do estudo, 71 não preencheram os critérios para soroconversão e foram excluídos a partir das análises. Entre os 1.638 participantes restantes que eram soronegativos no início do estudo, 214 mostraram soroconversão na visita 2. A incidência de soroconversão foi de 13,06% (IC 95% 11,52­14,79) em geral e 6,78% (5·61­8·10) para soroconversão sintomática, durante um período médio de acompanhamento de 57 dias (IQR 54­61). 48,1% de eventos de soroconversão foram estimados como assintomáticos. A amostra apresentou maiores proporções de pessoas abastadas e com nível superior do que aquelas relatadas para a população da cidade de Manaus. No modelo totalmente ajustado e corrigido, o risco fatores de soroconversão antes da visita 2 foram ter um caso de COVID-19 no domicílio (IRR 1·49 [IC 95% 1·21­1·83]), não usar máscara durante o contato com uma pessoa com COVID-19 (1·25 [1·09­1·45]), relaxamento do distanciamento físico (1·31 [1·05­1·64]) e com sintomas de gripe (1·79 [1·23­2·59]) ou um diagnóstico de COVID-19 (3·57 [2·27­ 5·63]) entre a primeira e a segunda visita, enquanto o trabalho remoto foi associado à menor incidência (0,74 [0,56­0,97]). Interpretação: Um intenso período de transmissão de infecção precedeu a segunda onda de COVID-19 em Manaus. Diversos comportamentos modificáveis ​ aumentaram o risco de soroconversão, incluindo o não cumprimento de medidas de intervenção como não uso de máscara durante o contato, relaxamento das medidas de proteção e trabalho não remoto. É necessário aumentar os testes em áreas de alta transmissão para fornecer informações oportunas sobre transmissão e ajudar na implementação apropriada de medidas de mitigação da transmissão.