Long-term impact of congenital Zika virus infection on the rat hippocampus: Neuroinflammatory, glial alterations and sex-specific effects

Abstract

Congenital Zika Syndrome (CZS) is a condition that arises when a neonate presents with abnormalities resulting from Zika virus infection during gestation. While microcephaly is a prominent feature of the syndrome, other forms of brain damage are also observed, often accompanied by significant neurological complications. It is therefore essential to investigate the long-term effects of CZS, with special attention to sex differences, particularly concerning hippocampal function, given its vulnerability to viral infections. The aim of this study was to evaluate the long-term impacts on cognitive and memory functions, as well as neuroinflammatory and glial alterations in the hippocampus, in offspring of both sexes exposed to a model of congenital Zika virus infection. Pregnant rats were subcutaneously inoculated with ZIKV-BR at a dose of 1 × 10^7 plaque-forming units (PFU mL^-1) of ZIKV isolated in Brazil (ZIKV-BR) on gestational day 18 (G18). From postnatal day 70, the animals underwent behavioral tests. On postnatal day 80, the animals were euthanized, and hippocampal samples were collected for biochemical and histological analyses. In the open field test, females displayed more exploratory behavior and less grooming, while no significant differences in locomotion were observed between the sexes. Additionally, ZIKV-exposed females showed a reduction in grooming behavior compared to ZIKV-exposed males. In the memory test, males in the ZIKV group exhibited greater memory impairment, spending more time to locate the correct quadrant, while females showed relatively better performance. Neuroinflammatory markers, such as TNF-α, were significantly elevated in the hippocampus of ZIKV-exposed animals, regardless of sex. However, microglial and astrocytic responses, indicated by higher IBA1 and GFAP density, were only observed in male ZIKV rats. In conclusion, our findings suggest that congenital ZIKV exposure leads to sex-specific behavioral and neuroinflammatory alterations. While both males and females exhibited some behavioral changes, males were more significantly impacted in memory performance. Additionally, increased neuroinflammatory markers and glial activation were observed in the hippocampus of ZIKV-exposed animals, with a pronounced response in males. These results highlight the long-term impact of ZIKV infection on neurodevelopment, emphasizing the importance of considering sex differences in studies of congenital ZIKV syndrome.