Pregnant women are at increased risk of adverse outcomes, including preeclampsia and preterm birth, that may result from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Pregnancy imprints specific maternal immune responses that can modulate host susceptibility to microbial infection; therefore, recent studies have focused on the humoral response against SARS-CoV-2 in pregnant women. However, the pregnancy-specific cellular immune responses triggered by SARS-CoV-2 infection are poorly understood. In this study, we undertook an extensive in vitro investigation to determine the cellular immune responses to SARS-CoV-2 particles and proteins/peptides in pregnant women. First, we show that SARS-CoV-2 particles do not alter the pregnancy-specific oxidative burst of neutrophils and monocytes. Yet, SARS-CoV-2 particles/proteins shift monocyte activation from the classical to intermediate states in pregnant, but not in nonpregnant, women. Furthermore, SARS-CoV-2 proteins, but not particles or peptide pools, mildly enhance T cell activation during pregnancy. As expected, B cell phenotypes are heavily modulated by SARS-CoV-2 particles in all women; yet, pregnancy itself further modified such responses in these adaptive immune cells. Lastly, we report that pregnancy itself governs cytokine responses in the maternal circulation, of which IFN-β and IL-8 were diminished upon SARS-CoV-2 challenge. Collectively, these findings highlight the differential in vitro responses to SARS-CoV-2 in pregnant and nonpregnant women and shed light on the immune mechanisms implicated in coronavirus disease 2019 during pregnancy.
Copyright © 2022 by The American Association of Immunologists, Inc.

Postmitotic differentiated neurons are among the most difficult cells to reprogram into induced pluripotent stem cells (iPSCs) because they have poor viability when cultured as dissociated cells. To overcome this, other protocols have required the inactivation of the p53 tumor suppressor to reprogram postmitotic neurons, which can result in tumorigenesis of the cells. We describe a method that does not require p53 inactivation but induces reprogramming in retinal cells from reprogrammable mice grown in aggregates with wild-type mouse retinal cells. After the first 10 d of reprogramming, the aggregates are then dispersed and plated on irradiated feeder cells to propagate and isolate individual iPSC clones. The reprogramming efficiency of different neuronal populations at any stage of development can be quantified using this protocol. Reprogramming retinal neurons using this protocol will take 56 d, and these retina-derived iPSCs can undergo retinal differentiation to produce retinae in 34 d. In addition, we describe a quantitative assessment of retinal differentiation from these neuron-derived iPSCs called STEM-RET. The procedure quantifies eye field specification, optic cup formation and retinal differentiation in 3D cultures using molecular, cellular and morphological criteria. An advanced level of cell culture experience is required to carry out this protocol.