Adverse outcomes in SARS-CoV-2–infected pregnant mice are gestational age–dependent and resolve with antiviral treatment

Abstract

SARS-CoV-2 infection during pregnancy is associated with severe COVID-19 and adverse fetal outcomes, but the underlying mechanisms remain poorly understood. Moreover, clinical studies assessing therapeutics against SARS-CoV-2 in pregnancy are limited. To address these gaps, we developed a mouse model of SARS-CoV-2 infection during pregnancy. Outbred CD1 mice were infected at E6, E10, or E16 with a mouse-adapted SARS-CoV-2 (maSCV2) virus. Outcomes were gestational age–dependent, with greater morbidity, reduced antiviral immunity, greater viral titers, and impaired fetal growth and neurodevelopment occurring with infection at E16 (third trimester equivalent) than with infection at either E6 (first trimester equivalent) or E10 (second trimester equivalent). To assess the efficacy of ritonavir-boosted nirmatrelvir, which is recommended for individuals who are pregnant with COVID-19, we treated E16-infected dams with mouse-equivalent doses of nirmatrelvir and ritonavir. Treatment reduced pulmonary viral titers, decreased maternal morbidity, and prevented offspring growth restriction and neurodevelopmental impairments. Our results highlight that severe COVID-19 during pregnancy and fetal growth restriction is associated with heightened virus replication in maternal lungs. Ritonavir-boosted nirmatrelvir mitigated maternal morbidity along with fetal growth and neurodevelopment restriction after SARS-CoV-2 infection. These findings prompt the need for further consideration of pregnancy in preclinical and clinical studies of therapeutics against viral infections.

Suppression of progesterone by influenza A virus mediates adverse maternal and fetal outcomes in mice

“…After birth and until weaning, pups were monitored daily for body mass (g) and the appearance of key developmental milestones including fur development, the opening of the ear canals and eyes, and teeth eruption (43, 44). At PND5, pups were subjected to the developmental neurobehavioral assay of surface righting, as described (45, 46). For each test, 1–2 male and 1–2 female offspring from at least 5 independent litters were used per condition to avoid confounding litter effects.…”

“…Routine H&E staining was performed to evaluate the morphological change of the placentas. Immunohistochemical staining ( Table S1 ) was performed as described (46, 49). Images were taken using a Zeiss Axioplan 2 microscope (Jena) under 5x or 20x magnification.…”

“…Images were taken using a Zeiss Axioplan 2 microscope (Jena) under 5x or 20x magnification. Cell density of vimentin and cytokeratin positive cell quantification was performed using Image J (1.47v) as described (46, 49). Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed with Click-iT™ Plus TUNEL Assay (ThermoFisher C10617) per the manufacturer protocol as described (46, 49).…”

“…Cell density of vimentin and cytokeratin positive cell quantification was performed using Image J (1.47v) as described (46, 49). Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed with Click-iT™ Plus TUNEL Assay (ThermoFisher C10617) per the manufacturer protocol as described (46, 49). For each placenta, 10 random images in labyrinth at the middle level (thickest) of placenta were taken, and the average percentage of TUNEL + nuclei (TUNEL + nuclei divided by the total number of DAPI + nuclei) given for that placenta.…”

“…Protein lysates from flash frozen right caudal lung lobes and right ovaries were prepared for as described (46, 49). For each sample, 20 µg of protein was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) on NuPAGE 4-12% Bis-Tris gels, blotted onto Immobilon-FL PVDF Membrane (Millipore #IPFL00010), and the membranes blocked, washed, and stained with primary and secondary antibodies ( Table S1 ) as described (46, 49). Blots were imaged on an Azure 600 imager (Azure Biosystems).…”