Mom's Cytotoxic T Cells from Dengue May Protect Babies Against Zika

Sep 24, 2018 10:09:00 AM by Stacy Matthews Branch, DVM, PhD

Mother and newborn baby in white nursery_AdobeStock_94173906-571838-editedResearchers investigated the fetal effects of Zika virus exposure in dengue-immune and nonimmune mice.

Outbreaks of Zika virus (ZIKV) infection in different parts of the world have raised awareness of its health effects. ZIKV is an RNA flavivirus and is transmitted by mosquitoes and sexual contact. An important feature of ZIKV infection is its maternal to fetal passage and induction of birth defects. Congenital Zika Syndrome has been described, and includes defects such as microcephaly, brain damage, eye defects, and musculoskeletal defects.

There is no cure or vaccine for Zika, but studies have shown cytotoxic T-cell mediated protection against Zika in mice previously infected with dengue flavivirus (DENV), which is closely related to ZIKV and transmitted by the same mosquito species. The effects of ZIKV infection in pregnant women previously infected with DENV are not known. Therefore, researchers investigated the fetal effects of ZIKV exposure in DENV-immune and nonimmune mice.

Dengue-immune pregnant mice were inoculated with ZIKV and fetuses were evaluated. DENV-immune mice that were exposed to ZIKV had normal fetuses with no visible morphological defects, resembling normal unaffected fetuses. Fetal resorption and decreased fetal weight and size were observed in nonimmune mice exposed to ZIKV. There was also a reduction in ZIKV RNA in the placenta and fetuses of DENV-immune pregnant mice treated with ZIKV, and cytotoxic T cells were present in the maternal-placental interface. The only DENV-immune mice with fetal resorption were those treated with an anti-CD8 antibody. This suggests that cytotoxic T cells contribute to the protection against ZIKV in DENV-immune mice.

Mice immunized with dengue virus proteins capable of inducing T-cell response were exposed to ZIKV, mated, and evaluated for effects on fetuses. The immunization lead to lower ZIKV infection in the placental tissue when compared to mice that were not exposed to the dengue proteins. This further shows the protective role of cytotoxic T cells against ZIKV. Taken together, dengue-infected mice had immunity against ZIKV infection that is mediated by cytotoxic T-cell cross-reactivity. These results provide essential information that can be applied in efforts to develop vaccines that may protect against both ZIKV and DENV.

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Reference:

Maternal dengue immunity protects against fetal damage in mice following Zika infection: Cytotoxic T-cells mobilized by dengue infection may combat catastrophic effects of Zika infection. (2018). ScienceDaily. Retrieved 21 August 2018, from https://www.sciencedaily.com/releases/2018/08/180802102411.htm