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.

Estudo comparativo dos resultados obtidos pelos métodos de imunocromatografia e o ELISA para detecção de anticorpos IgM e IgG anti-vírus dengue / Comparative study of the results obtained by immunocromatography methods and ELISA IgM and IgG antibodies detection antidengue virus

O dengue constitui sério problema de saúde pública no mundo, especialmente na maioria dos países tropicais. No Brasil, o diagnóstico sorológico é realizado pelo ensaio imunoenzimático para captura de IgM (MAC-ELISA) e IgG (ELISA IgG) anti-dengue, entretanto, inúmeros kits estão disponíveis no mercado. Nesse estudo, o Kit Dengue - Teste Rápido em Tira (KD-TRT) é comparado com as técnicas padrões. Foram utilizadas 72 soros, incluindo soros de pacientes com infecção confirmada ou presuntiva por dengue, com infecção por febre amarela e rubéola, bem como, de pacientes com sorologia dengue negativa. O KD-TRT apresentou sensibilidade de 54,2 porcento e especificidade de 100 porcento mediante análise dos soros de pacientes com ou sem dengue. Quando incluídas as amostras de febre amarela e rubéola, o KD-TRT apresentou os índices de 54,2 porcento e 91,2 porcento de sensibilidade e especificidade, respectivamente. Os resultados da detecção de anticorpos IgG do KD-TRT foram correlacionados com os resultados do ELISA IgG. O ELISA IgG detectou 20 (38,5 porcento) reações primárias, 17 (32,7 porcento) reações secundárias e 15 (28,8 porcento) reações negativas, enquanto que o KD-TRT detectou 11 (21,2 porcento), 7 (13,5 porcento) e 34 (65,3 porcento), respectivamente. O KD-TRT apresentou menor sensibilidade e especificidade em relação ao MAC-ELISA e baixa correlação de resultados com ELISA IgG.