Single-cell RNA sequencing highlights a reduced function of natural killer and cytotoxic T cell in recovered COVID-19 pregnant women

Pregnancy is a complex phenomenon during which women undergo immense immunological change throughout this period. Having an infection with the SARS-CoV-2 virus leads to an additional burden on the highly stretched immune response. Some studies suggest that age-matched pregnant women are more prone to SARS-CoV-2 infection compared with normal healthy (non-pregnant) women, while alternative evidence proposed that pregnant women are neither susceptible nor develop severe symptoms. This discrepancy in different findings regarding the immune responses of pregnant women infected with SARS-CoV-2 virus is not well understood. In this study, we investigated how SARS-CoV-2 viral infection could modulate the immune landscape during the active infection phase and recovery in pregnant females. Using flow cytometry, we identified that intermediate effector CD8 ⁺ T cells were increased in pregnant women who had recovered from COVID-19 as opposed to those currently infected. Similarly, an increase in CD4 ⁺ T helper cells (early or late) during the recovered phase was observed during the recovery phase compared with infected pregnant women or healthy pregnant women, whilst infected pregnant women had a reduced number of late effector CD4 ⁺ T cells. CD3 ⁺ CD4 ^- CD8 ^- NKT cells that diminished during active infection in contrast to healthy pregnant women were significant increase in recovered COVID-19 recovered pregnant women. Further, our single-cell RNA sequencing data revealed that infection of SARS-CoV-2 had changed the gene expression profile of monocytes, CD4 ⁺ effector cells and antibody producing B cells in convalescent as opposed to healthy pregnant women. Additionally, several genes with cytotoxic function, interferon signalling type I & II, and pro- and anti-inflammatory functions in natural killer cells and CD8 ⁺ cytotoxic T cells were compromised in recovered patients compared with healthy pregnant women. Overall, our study highlights that SARS-CoV-2 infection deranged the adaptive immune response in pregnant women and could be implicated in pregnancy complications in ongoing pregnancies.