High frequency of pre-existing neutralizing antibody responses in patients with dengue during an outbreak in Central Brazil.

BACKGROUND: This study aims to identify dengue neutralizing antibody response in patients with dengue from a well-characterized cohort during an outbreak in central Brazil, 2012-2013. METHODS: We analyzed paired samples from 40 patients with severe dengue and 20 patients with dengue. Eligibility criteria were: IgM, NS1Ag and/or RT-PCR positivity and positive IgG result. Plaque reduction neutralization test (PRNT50) from DENV-1 to DENV-4 was performed to identify serotype-specific NAbs response. An infecting serotype was defined as ≥4-fold increase in DENV NAbs in paired samples. Monotypic response was classified as PRNT50 ≥ 1/20 to only one DENV serotype, and multitypic response was considered to be PRNT50 ≥ 1/20 to two or more serotypes simultaneously. RESULTS: Patients were mainly adults. Virological dengue infection was confirmed by RT-PCR: DENV-4(n = 14) and DENV-1(n = 10). Forty-four out of 60(73.3 %) patients had NAbs to DENV-4, DENV-1(68.3 %), DENV-2(68.3 %) and DENV-3(61.6 %) respectively. Fifteen percent of the cases presented monotypic response, whereas 85 % had multitypic response. DENV-4 infected-patients presented the greatest difference in PRNT50 titers compared with other serotypes. Pre-existing DENV NAbs was not correlated with disease severity. This was the first time that DENV-4 was implicated in an epidemic in the region. CONCLUSION: Our data indicates high exposure of multiple DENV serotypes in all age groups in the pre-dengue vaccine era and also previous to Zika virus introduction in Brazil.

Guillain-Barré Syndrome, Acute Disseminated Encephalomyelitis and Encephalitis Associated with Zika Virus Infection in Brazil: Detection of Viral RNA and Isolation of Virus during Late Infection.

Zika virus (ZIKV) emerged in Brazil in 2015, which was followed by an increase of Guillain-Barre Syndrome (GBS) cases. We report the epidemiological, clinical, and laboratory findings of the first six neurological cases associated with ZIKV in Brazil seen in a reference neurology hospital in Pernambuco, Brazil. In all cases, ZIKV was detected in serum and/or cerebrospinal fluid (CSF) samples. In this case series, four cases were defined as GBS, one as acute disseminated encephalomyelitis (ADEM) and the other as encephalitis. ZIKV was detected in all cases by RT-PCR and virus isolation was successful in two patients. The time between ZIKV acute symptoms and the development of neurological manifestations varied from 3 to 13 days and ZIKV was detected between 15 and 34 days after the initial symptoms. Our results highlight the need to include ZIKV as a differential diagnosis for neurological syndromes in countries with circulation of this arbovirus. Because the viremia in these patients appears to persist longer, direct diagnostic techniques such as RT-PCR and viral isolation should be considered even if it is after the acute phase of viral infection.