Porcine reproductive and respiratory virus 2 infection of the fetus results in multi-organ cell cycle suppression

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) infection during late gestation negatively affects fetal development. The objective of this study was to identify the fetal organs most severely impacted following infection, and evaluate the relationship between this response and fetal phenotypes. RNA was extracted from fetal heart, liver, lung, thymus, kidney, spleen, and loin muscle, collected following late gestation viral challenge of pregnant gilts. Initially, gene expression for three cell cycle promoters (CDK1, CDK2, CDK4) and one inhibitor (CDKN1A) were evaluated in biologically extreme phenotypic subsets including gestational age-matched controls (CON), uninfected (UNIF), high-viral load viable (HV-VIA), and high-viral load meconium-stained (HV-MEC) fetuses. There were no differences between CON and UNIF groups for any gene, indicating no impact of maternal infection alone. Relative to CON, high-viral load (HV-VIA, HV-MEC) fetuses showed significant downregulation of at least one CDK gene in all tissues except liver, while CDKN1A was upregulated in all tissues except muscle, with the heart and kidney most severely impacted. Subsequent evaluation of additional genes known to be upregulated following activation of P53 or TGFb/SMAD signaling cascades indicated neither pathway was responsible for the observed increase in CDKN1A. Finally, analysis of heart and kidney from a larger unselected population of infected fetuses from the same animal study showed that serum thyroxin and viral load were highly correlated with the expression of CDKN1A in both tissues. Collectively these results demonstrate the widespread suppression in cell division across all tissues in PRRSV infected fetuses and indicate a non-canonical regulatory mechanism.

Compensatory mechanisms in response to induced hypothyroidism in the late gestation pig fetus

“…Thyroidectomy of late gestation fetal sheep showed a decrease in the proportion of fetal heart weight relative to body weight, which is associated with decreased cardiomyocyte maturation [ 56 ]. Similarly, in fetal pigs experiencing a decrease in circulating thyroid hormone associated with PRRSV infection, the heart is severely impacted by altered gene expression associated with the regulation of cell cycle progression [ 25 , 62 ]. These reports are consistent with current study findings that fetuses rendered hypothyroid from MMI exposure have decreased heart weights relative to body weight.…”

Genome wide association study of thyroid hormone levels following challenge with porcine reproductive and respiratory syndrome virus

“…In humans HSDL2 modulates cervical cancer cell proliferation and metastasis ( Yang et al, 2021 ). Recent work has shown PRRSV infection in fetus to result in multi-organ cell cycle suppression ( Mulligan et al, 2022 ). In addition, the CREG1 and POU2F1 proteins function in cell proliferation and differentiation pathways and were identified near QTL for fetal_T3 levels in the current study.…”

Impact of methimazole‐induced hypothyroidism on postnatal swine

“…Frozen LVR tissue samples were ground under liquid nitrogen into a fine powder using frozen mortar and pestles. RNA was extracted with TRIzol (Thermofisher Scientific, Waltham, USA) (Cat# 15596026) followed a double‐precipitation method as previously described (Mulligan et al., 2022 ). Contaminating DNA was removed with the TURBO DNase kit (Thermofisher Scientific, Cat# AM2238) following manufacturers instructions but with the addition of recombinant RNAse inhibitor (Thermofisher Scientific, Cat# N8080119).…”