Seroprevalence of antibodies against SARS-CoV-2 in the school community in Campo Grande, state of Mato Grosso do Sul, Brazil, October 2021-November 2022.

Introduction: With the reopening of schools during the coronavirus disease 2019 (COVID-19) pandemic, it was imperative to understand the role of students and education professionals in the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this paper, we determined the seroprevalence of the SARS-CoV-2 anti-nucleocapsid antibodies in the school community in Campo Grande, the capital and most populous city of the state of Mato Grosso do Sul (Brazil) and evaluated its association with sex, school level, and school type. Materials and methods: The survey was carried out in 20 public and private schools in the urban region of Campo Grande using the TR DPP® COVID-19 immunoglobulin M/immunoglobulin G (IgM/IgG) kit from the Immunobiological Technology Institute (Bio-Manguinhos, Rio de Janeiro, Brazil). Testing was carried out in three periods: from October to December 2021; from March to July 2022; and from August to November 2022. The participants were students aged 6-17 years enrolled in primary or secondary schools and professionals of different ages and roles. Results: During the first testing period, 162 participants were seropositive for the IgM and/or IgG anti-nucleocapsid SARS-CoV-2 antibodies, with an estimated seroprevalence of 19.6% using Bayesian multilevel regression. In the second period, 251 participants were seropositive (estimated seroprevalence, 34.6%), while in the third period, 393 participants were seroconverted (estimated seroprevalence, 56.7%). In 2022, there was an increase in the seroconversion rate compared to that in 2021. The most frequently described acute manifestations in the three periods were fever, headache, sore throat, and runny nose. In terms of the demographic profile, there was no predominance of seropositivity between the sexes, although women represented approximately 70% of the study population. There were also no differences between students and school staff. Discussion: The results made it possible to evaluate the extent of SARS-CoV-2 transmission in the school community through immunity developed against the virus, in addition to providing information about COVID-19 symptoms in children, adolescents, and adults.

Development and validity assessment of ELISA test with recombinant chimeric protein of SARS-CoV-2.

Serological tests developed for COVID-19 diagnostic are based on antibodies specific for SARS-CoV-2 antigens. Most of the antigens consist of a fragment or a whole amino acid sequence of the nucleocapsid or spike proteins. We evaluated a chimeric recombinant protein as an antigen in an ELISA test, using the most conserved and hydrophilic portions of the S1-subunit of the S and Nucleocapsid (N) proteins. These proteins, individually, indicated a suitable sensitivity of 93.6 and 100% and a specificity of 94.5 and 91.3%, respectively. However, our study with the chimera containing S1 and N proteins of SARS-CoV-2 suggested that the recombinant protein could better balance both the sensitivity (95.7%) and the specificity (95.5%) of the serological assay when comparing with the ELISA test using the antigens N and S1, individually. Accordingly, the chimera showed a high area under the ROC curve of 0.98 (CI 95% 0.958-1). Thus, our chimeric approach could be used to assess the natural exposure against SARS-CoV-2 virus over time, however, other tests will be necessary to better understand the behaviour of the chimera in samples from people with different vaccination doses and/or infected with different variants of the virus.

Case Report: SARS-CoV-2 Gamma Isolation From Placenta of a Miscarriage in Midwest, Brazil.

The present study investigated a SARS-CoV-2 infection in placenta and fetal samples from an early pregnancy miscarriage in Midwest Brazil. The Gamma variant was isolated and fully sequenced from the placenta sample, but not from fetal samples. Our findings highlight potential adverse perinatal outcomes caused by SARS-CoV-2 Gamma infection during pregnancy.

Cuantificación relativa de genes relacionados con la respuesta inmune antiviral en una población venezolana de Aedes (stegomyia) aegypti / Relative quantification of Antiviral immune response related genes in an Aedes (stemgoyia) aegypti Venezuelan population

El virus DENV-3 es el responsable del segundo mayor porcentaje de afecciones hemorrágicas severas causadas por este virus, solo superado por el virus DENV-2. La virulencia de este serotipo, causante de brotes epidémicos a gran escala en países como Venezuela donde circula activamente durante todo el año, es la razón principal del desarrollo investigativo en el campo de las interacciones virus-vector en la búsqueda de un control epidémico efectivo. En el presente trabajo, se evaluó la expresión de dos genes, RNAi (dcr-2 y ago-2), que codifican para proteínas de respuesta antiviral en mosquitos con la finalidad de estudiar el cambio en la expresión de los mismos en el vector una vez infectado con el DENV-3. Para ello, se infectó artificialmente una población de Aedes (stegomyia) aegypti de Trujillo, elaborándose dos grupos experimentales (15dpi y 20dpi) y un control; posteriormente se aisló, cuantificó y se realizó transcripción reversa al RNA total aislado de los grupos. La infección en los grupos experimentales se evidenció por la detección de bandas de productos de PCR de 511pb para DENV y 290pb para DENV-3 mediante electroforesis en gel de agarosa al 2%, y se realizó la cuantificación relativa de la expresión genética por PCR en tiempo real. Como resultado, la expresión de los genes no presentó cambios con respecto a los mosquitos no infectados (grupo control) (p<0.05). Estos resultados indican que el virus DENV-3 pudiera estar mostrando mecanismos de evasión sobre las vías de RNAi dentro del cuerpo del vector, y esto puede estar relacionado al hecho de que la replicación de los miembros del genero Flavivirus, entre ellos el DENV, se lleva a cabo en el sistema de membranas y vesículas, lo que les permite evadir el encuentro en el citoplasma con las proteínas asociadas al complejo de RNAi.

DENV-3 is the responsible for the second major percentage of hemorrhagic severe affections caused by this virus, only overcome by DENV-2. The virulence of this serotype is the cause of broad scale fever outbreaks in different countries, especially in Venezuela where it circulates actively throughout the year. This is the main reason of investigative developments in the virus-vector interactions field to find an effective epidemic control. In this study, we evaluated the expression of dcr-2 and ago-2, two RNAi antiviral pathway genes in mosquitoes to study the fold change in the expression of these genes in the mosquito vector Aedes (stegomyia) aegypti infected with DENV-3. We artificially infected a population of mosquitoes from Trujillo state (Venezuela) and prepared three (3) experimental groups (15dpi, 20dpi and a control group). Later, we isolated, quantified and applied a reverse transcription to the total RNA obtained of mosquitoes and the infection in the experimental groups was detected performing a 2% agarose gel electrophoresis of the PCR products of the total RNA (511bp for DENV and 290bp for DENV3). In addition, the infection in the experimental groups was confirmed by the detection of PCR products. The fold change in dcr-2 and ago-2 expression genes was quantify by Real Time PCR. As results, the fold change expression in the ago-2 and dcr-2 were equal to the non-infected mosquitoes “control group” (p<0.05). These results indicate that DENV-3 could have evasion mechanisms of RNAi pathway inside vector’s body, and this can be related to the fact that dengue virus replication is accomplished in the vesicle system and membrane system as well (endoplasmic reticulum and golgi complex) avoiding cytoplasmic encounter with the RNAi pathway proteins.

Potential role of sylvatic and domestic African mosquito species in dengue emergence.

Dengue virus 2 (DENV-2) strains that circulate in sylvatic habitats of Senegal and other parts of west Africa are believed to represent ancestral forms that evolved into endemic/epidemic strains that now circulate widely in urban areas of the tropics. Previous studies suggested that the evolution of the endemic/epidemic strains was mediated by adaptation to the peridomestic mosquito vectors Aedes aegypti and Ae. albopictus. We conducted experimental infections using sylvatic and peridomestic Senegalese mosquitoes, and both sylvatic and urban DENV-2 strains to determine if endemic DENV-2 adaptation was vector species specific, and to assess ancestral vector susceptibility. Aedes furcifer and Ae. luteocephalus, probable sylvatic vectors, were highly susceptible to both sylvatic and urban DENV-2 strains. In contrast, sylvatic Ae. vittatus and both sylvatic and peridomestic populations of Ae. aegypti were relative refractory to all DENV-2 strains tested. These results indicate that adaptation of DENV-2 to urban vectors did not result in a loss of infectivity for some African sylvatic vectors. Implications for dengue emergence in west Africa are discussed.

Susceptibility of urban and rural populations of Aedes albopictus from São Paulo State, Brazil, to infection by dengue-1 and -2 viruses.

In Brazil, dengue viruses (DENV) are transmitted by Aedes aegypti (L.). However, the recent introduction of Aedes albopictus (Skuse) has caused concern, because some populations of this species also are capable of DENV transmission. Ae. albopictus from rural and urban localities of São Paulo State, Brazil, were artificially exposed to infection with DENV-1 and -2 to evaluate their susceptibility. The rates of infection (6.2 and 5.7% for DENV-1; 5.3 and 12% for DENV-2) and dissemination (22.2 and 40% for DENV-1; 0 and 20% for DENV-2) were low in both urban and rural populations, with no significant differences detected between these mosquito populations.

Dengue emergence and adaptation to peridomestic mosquitoes.

Phylogenetic evidence suggests that endemic and epidemic dengue viruses (DENV), transmitted among humans by the anthropophilic mosquitoes Aedes aegypti and Ae. albopictus, emerged when ancestral, sylvatic DENV transmitted among nonhuman primates by sylvatic Aedes mosquitoes adapted to these peridomestic vectors. We tested this hypothesis by retrospectively examining evidence for adaptation of epidemic and endemic versus sylvatic strains of DENV-2 to Ae. albopictus and Ae. aegypti. First and second-generation offspring of mosquitoes from different geographic regions in the Americas and Southeast Asia were tested for their susceptibility to epidemic/endemic and sylvatic DENV-2 isolates from West Africa, Southeast Asia, and Oceania. Both Aedes species were highly susceptible (up to 100% infected) to endemic/epidemic DENV-2 strains after ingesting artificial blood meals but significantly less susceptible (as low as 0%) to sylvatic DENV-2 strains. Our findings support the hypothesis that adaptation to peridomestic mosquito vectors mediated dengue emergence from sylvatic progenitor viruses.

[Survival of Aedes albopictus: physiological age and reproductive history]. / Sobrevivência de populações de Aedes albopictus: idade fisiológica e história reprodutiva.

OBJECTIVES: To study the longevity of Ae. albopictus populations in rural and urban areas in two different feeding conditions and to assess their physiological age and reproductive history. METHODS: Ae. albopictus larvae were collected in the Para ba Valley, (urban area) and Ribeira Valley (rural area), S o Paulo State, Brazil. In the laboratory, females were fed with sugar or blood and monitored daily. The day of death of each mosquito and other reproduction related characteristics were registered. Ovaries were dissected using Polovodova techniques and follicular development was examined according Christophers and Mer. Life tables were created and statistics analysis was performed for survival rates. Data analysis was carried out using Stata 7.0. RESULTS: Gonotrophic discordance was seen in both populations. Parous females developed terminal sacs. Nulliparous females had normal ovaries and in some cases dilatations were seen. Females fed with sugar showed higher survival rates. Statistical difference in survival rates was not observed in the populations of both areas. CONCLUSIONS: Parity status and physiological age of Ae. albopictus were not described using ovarioles analysis because they formed terminal sacs instead of dilations. Longevity of Ae. albopictus females was influenced by the food provided.

Potencial sinantrópico de mosquitos Kerteszia e Culex (Diptera: Culicidae) no Sudeste do Brasil / The synanthropic potential of Kerteszia and Culex mosquitoes (Diptera: Culicidae) in Southeastern Brazil

Objetivo: Observar a potencialidade sinantrópica de Anopheles bellator e de An. cruzii em vilarejo rodeado por ambiente natural. Métodos: As observaçöes foram levadas a efeito na localidade de Pedrinhas, no Sudeste do Estado de Säo Paulo, Brasil, de outubro de 1996 a janeiro de 2000. A sinantropia, ou domiciliaçäo, foi estimada pelo índice de Nuorteva (s) acrescido do fator intradomiciliar de Mihályi (d) e adaptado para culicídeos hematófagos. Resultados: Utilizando procedimento baseado na atraçäo pela isca humana, as duas espécies de Kerteszia mostraram freqüência conjunta positiva correspondente a s=35,7. Isso parece indicar a existência de certo grau de sinantropia por parte desses mosquitos. Assim também, a populaçäo de Cx. sacchettae, correspondente à razäo de sinantropia sr=12,8, obtida pelo cálculo da relaçäo entre os dados conseguidos na armadilha de Shannon. Quanto ao método de procura ativa pela aspiraçäo ambiental, os resultados obtidos consistiram em valores negativos de s. Assim, corresponderam a -43,1 para An. bellator, -48,2 para An. cruzii e -3,0 para Cx. sacchettae. Tais cifras foram relacionadas ao valor positivo de s=+93,8 apresentado por Cx. quinquefasciatus e considerado como equivalente a +100,00. Conclusöes: O observado em relaçäo a domicílios isolados rurais repetiu-se em conjunto de casas formando vila, também de caráter rural, e circundada por ambiente primitivo, ou seja, esses mosquitos adultos tendem a procurar o ambiente antrópico na busca de repasto sangüíneo. Uma vez tendo-o conseguido, voltam para o ambiente de onde saíram. Todavia, revelou-se alguma tendência adaptativa revelada pelo encontro de formas imaturas de An. bellator em recipientes artificiais. Quanto a Cx. sacchettae, a populaçäo local parece mostrar tendência para adaptaçäo ao meio antrópico

Comportamento de Aedes albopictus e de Ae. scapularis adultos (Diptera: Culicidae) no Sudeste do Brasil / Adults Aedes albopictus and Ae. scapularis behavior (Diptera: Culicidae) in Southeastern Brazil

Objetivo: Observar e comparar o comportamento das espécies de Aedes albopictus e de Ae. scapularis, na localidade de Pedrinhas, litoral sul do Estado de Säo Paulo, Brasil. Métodos: As observaçöes foram feitas de outubro de 1996 a janeiro de 2000. Foram realizadas coletas sistemáticas de formas adultas mediante a utilizaçäo de isca humana, aspiraçöes ambientais e armadilha tipo Shannon. A domiciliaçäo foi estimada pelo índice de Nuorteva e pela razäo de sinantropia. Resultados: Foram feitas 87 coletas diurnas, com a obtençäo de 872 adultos fêmeas. As médias de Williams, multiplicadas por 100, foram de 118 e 21 para Ae. albopictus nos horários de 7h às 18h e de 18h às 20h, respectivamente. Quanto a Ae. scapularis, foram de 100 e 106 nos mesmos períodos. Esse último revelou pico de atividade crepuscular vespertina. Na aspiraçäo de abrigos, obteve-se o total de por 1.124 espécimens, dos quais 226 Ae. albopictus e 898 Ae. scapularis. O período janeiro-maio correspondeu ao de maior rendimento para ambos os mosquitos. Quanto à armadilha de Shannon, as coletas realizadas na mata revelaram a ausência de Ae. albopictus. No que concerne à domiciliaçäo, esse último mostrou os maiores valores de índices, enquanto Ae. scapularis revelou comportamento de tipo ubiquista. Conclusöes: Os resultados confirmam outras observaçöes, permitindo levantar hipóteses. Em relaçäo a Ae. scapularis, sugere-se que possa existir fenômeno de diapausa das fêmeas no período veräo-outono, a qual cessaria no inverno-primavera quando entäo a atividade seria retomada. Quanto a Ae. albopictus, os dados sugerem que se trata de populaçäo em processo adaptativo ao novo ambiente

Identificaçäo do vírus causador da encefalomielite eqüina, Paraná, Brasil / Identification of the encephalitis equine virus, Brazil

Objetivo: No período de 1996 a 1999, um agente viral causador de encefalomielite afetou as populaçöes de eqüinos em diferentes regiöes do Estado do Paraná, Brasil. Objetivou-se realizar pesquisa sorológica na tentativa de isolar o vírus causador da doença. Métodos: Em quatro municípios do Estado do Paraná, Brasil, foram coletados culicídeos com armadilha Shannon e isca humana, identificados e processados para isolamento de vírus. Em dois municípios estudados foram colhidas amostras de sangue de eqüinos para isolamento de vírus e para pesquisa sorológica. Os soros foram analisados pelo teste de inibiçäo da hemaglutinaçäo frente a diferentes antígenos de Alphavirus e Flavivirus. Aqueles que revelaram reaçöes positivas-cruzadas foram analisados pelo teste de neutralizaçäo. Resultados: Foram coletados culicídeos dos gêneros: Culex, Aedes, Mansonia, Coquillettidia, Psorophora, Sabethes, Wyeomyia e Limatus. Embora näo sendo isolado o agente viral, foram detectados anticorpos hemaglutinantes para o vírus Encefalomielite eqüina do Leste, Mucambo, Pixuna, Maguari e St. Luis. Em doze amostras de soros foram detectados anticorpos neutralizantes para o vírus Encefalomielite eqüina do Leste. Conclusöes: Foram coletadas espécies de culicídeos, considerados na bibliografia como vetores de vírus causadores de encefalomielite buniavírus e outras arboviroses de importância epidemiológica. Pela presença de sintomas de encefalomielite e de anticorpos para o vírus Encefalomielite eqüina do Leste nos soros de cavalos, supöe-se ser esse o vírus causador da doença nos eqüinos das regiöes estudadas