Anti-Flavivirus antibodies are highly cross-reactive and may facilitate Zika virus (ZIKV) infection through the antibody-dependent enhancement (ADE) mechanism. We demonstrate that dengue-specific antibodies enhance the infection of a primary Brazilian ZIKV isolate in a FcγRII-expressing K562 cell line. In addition, we demonstrate that serum samples from dengue-immune pregnant women enhanced ZIKV infection. These findings highlight the need for epidemiological studies and animal models to further confirm the role of ADE in the development of congenital and neurological complications associated with ZIKV infections.

Zika virus (ZIKV) infection during pregnancy is associated with microcephaly, a congenital malformation resulting from neuroinflammation and direct effects of virus replication on the developing central nervous system (CNS). However, the exact changes in the affected CNS remain unknown. Here, we show by transcriptome analysis (at 48 h post-infection) and multiplex immune profiling that human induced-neuroprogenitor stem cells (hiNPCs) respond to ZIKV infection with a strong induction of type-I interferons (IFNs) and several type-I IFNs stimulated genes (ISGs), notably cytokines and the pro-apoptotic chemokines CXCL9 and CXCL10. By comparing the inflammatory profile induced by a ZIKV Brazilian strain with an ancestral strain isolated from Cambodia in 2010, we observed that the response magnitude differs among them. Compared to ZIKV/Cambodia, the experimental infection of hiNPCs with ZIKV/Brazil resulted in a diminished induction of ISGs and lower induction of several cytokines (IFN-α, IL-1α/β, IL-6, IL-8, and IL-15), consequently favoring virus replication. From ZIKV-confirmed infant microcephaly cases, we detected a similar profile characterized by the presence of IFN-α, CXCL10, and CXCL9 in cerebrospinal fluid (CSF) samples collected after birth, evidencing a sustained CNS inflammation. Altogether, our data suggest that the CNS may be directly affected due to an unbalanced and chronic local inflammatory response, elicited by ZIKV infection, which contributes to damage to the fetal brain.

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In Chagas disease, chronically infected individuals may be asymptomatic or may present cardiac or digestive complications, and it is well known that the human immune response is related to different clinical manifestations. Different patterns of cytokine levels have been previously described in different clinical forms of this disease, but contradictory results are reported. Our aim was to evaluate the serum levels of interleukin-10 and tumour necrosis factor-alpha in patients with asymptomatic and cardiac Chagas disease. The serum interleukin-10 levels in patients with cardiomyopathy were higher than those in asymptomatic patients, mainly in those without heart enlargement. Although no significant difference was observed in serum tumour necrosis factor-alpha levels among the patients, we found that cardiac patients also present high levels of this cytokine, largely those with heart dilatation. Therefore, these cytokines play an important role in chronic Chagas disease cardiomyopathy. Follow-up investigations of these and other cytokines in patients with chronic Chagas disease need to be conducted to improve the understanding of the immunopathology of this disease.

Background Zika virus (ZIKV) is a mosquito-borne virus that is also transmitted sexually, however, the epidemiological relevance of ZIKV sexual transmission in endemic regions is unclear. Methods We performed a household-based serosurvey in Northeast Brazil to evaluate the differential exposure to ZIKV and chikungunya virus (CHIKV) among households. Individuals who participated in our previous arboviral disease cohort (indexes) were re-contacted and enrolled, and their household members were newly enrolled. Results The Relative Risk (RR) of sexual partners being ZIKV seropositive when living with a ZIKV-seropositive index participant was significantly higher, while this was not observed among non-sexual partners of the index. For CHIKV, both sexual and non-sexual partner household members living with a CHIKV-seropositive index had a significantly higher risk of being seropositive. In the non-index based dyadic and generalized linear mixed model analyses, the odds of sexual dyads having a concordant ZIKV PRNT result was significantly higher. We have also analyzed retrospective clinical data according to the participants’ exposure to ZIKV and CHIKV. Conclusion Our data suggest that ZIKV sexual transmission may be a key factor for the high ZIKV seroprevalence among households in endemic areas and raises important questions about differential disease from the two modes of transmission.