20Recent outbreaks of Zika virus (ZIKV) have been associated with birth defects, 21 including microcephaly and neurological impairment. However, the mechanisms which 22 confer increased susceptibility to ZIKV during pregnancy remain unclear. We 23 hypothesized that poor outcomes from ZIKV infection during pregnancy are due in part 24 to pregnancy-induced alteration of innate immune cell frequencies and cytokine 25 expression. To examine the impact of pregnancy on innate immune responses, we 26 inoculated pregnant and non-pregnant female C57BL/6 mice with 5x105 FFU of ZIKV 27 intravaginally. Innate immune cell frequencies and cytokine expression were measured 28 by flow cytometry at day 3 post infection. Compared to non-pregnant mice, pregnant 29 mice exhibited higher frequencies of uterine macrophages (CD68+) and tolerogenic 30 dendritic cells (CD11c+ CD103+ and CD11c+ CD11b+). Additionally, ZIKV-infected 31 pregnant mice had lower frequencies of CD45+ IL-12+ and CD11b+ IL-12+ cells in the 32 uterus and spleen. These data show that pregnancy results in an altered innate immune 33 response to ZIKV infection in the genital tract of mice and that pregnancy-associated 34 immune modulation may play an important role in the severity of acute ZIKV infection.
35
Importance
36Pregnant females longer duration that viremia following infection with Zika virus 37 but the mechanism of this is not established. Innate immune cellular responses are 38 important for controlling virus infection and are important for development and 39 maintenance of pregnancy. Thus, the acute immune response to Zika virus during 40 pregnancy may be altered so that the pregnancy can be maintained. To examine this 41 interaction, we utilized a mouse model of Zika virus infection during pregnancy using 42 3 intravaginal inoculation. We found that following Zika virus infection, pregnant mice 43 exhibited increased expression of tolerant or non-inflammatory dendritic cells. 44 Additionally, we found that pregnant mice have significantly depressed ability to secrete 45 the cytokine IL-12 from innate immune cells in the uterus and the spleen while 46 maintaining MHCII expression. These findings show that pregnancy-induced changes in 47 the innate immune cells are biased towards tolerance and can result in decreased 48 antigen-dependent stimulation of immune responses.49 50 Zika virus (ZIKV) is a neurotropic flavivirus originally isolated from a febrile 51 rhesus macaque in the Zika Forest of Uganda (1). Although ZIKV was first identified in 52 humans in 1952, only sporadic infections occurred in humans until 2007, when the first 53major outbreak was reported on Yap Island (2). Since its emergence, infections have 54 been reported in Africa, Asia, the Pacific Islands, and the Americas. ZIKV is transmitted 55 to humans predominantly through bites from Aedes mosquitos, but infections after 56 sexual contact and blood transfusions have also been reported (3, 4). The majority of 57 infected individuals are asymptomatic, with some infections causing mild...