Effect of PRRSV2 on tight junctions in the porcine maternal-fetal interface
Date
2022-02-09
Authors
Journal Title
Journal ISSN
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Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Existing strategies to control porcine reproductive and respiratory syndrome (PRRS) are
not completely effective and require alternative approaches. Although intrauterine growth
restricted (IUGR) fetuses are more resilient to transplacental PRRS virus-2 (PRRSV2) infection
compared to normal fetuses, the underlying mechanisms are unknown. The overall aim of this
research was to assess a subset of tight junction (TJ) proteins in the maternal-fetal interface (MFI)
of PRRSV-infected versus control fetuses, across various fetal preservation statuses including
uninfected (UNIF) and viable (VIA) and meconium stained (MEC), and in IUGR and non (N)-
IUGR fetuses. The specific objectives of chapter 2 were to evaluate the abundance and localization
of a small subset of TJ proteins in the MFI of non-infected control (CTRL), and in PRRSV2
infected IUGR, N-IUGR and MEC fetuses and identify any alterations that may affect the
movement of nutrients or PRRSV2 across the epitheliochorial placenta. Expanding on these
results, the objective of chapter 3 was to evaluate the expression of a larger number of TJ genes in
the placenta and endometrium of PRRSV2-infected fetuses, firstly across IUGR/N-IUGR and
CTRL/PRRSV2-infected high viral load (HVL) groups using a 2 x 2 factorial approach, and
secondly across disease progression groups by comparing CTRL, UNIF, HVL-VIA fetuses, and
HVL MEC in the body (HVL-MEC-B) fetuses.
In non-infected CTRL, immunostaining for TJP1 was consistent and abundant across all
MFI regions, except for maternal and fetal endothelial cells. Immunostaining for claudins (CLDN)
1, 4, and 7 was more variable across the MFI regions. Cellular localization of TJP1 was apical in
every region assessed, whereas the claudins were more variable. Immunostaining in the maternal
villus base/tip epithelium and areolae had mostly basolateral cellular localization. Fetal villus
tip/base, amnion and areolae had mostly paracellular cellular localization, while glandular
epithelium and endothelial cells had primarily intracellular cellular localization. In PRRSVinfected
fetal groups, the intensity of CLDN1 was lower in placenta of IUGR, MEC, and N-IUGR
fetuses compared to CTRL, mainly in fetal epithelium and maternal endothelial cells. CLDN4
intensity was lower in maternal endothelial cells of IUGR compared to CTRL and MEC fetuses.
Finally, TJP1 intensity was lower in maternal and fetal epithelia of placenta in IUGR, MEC, and
N-IUGR fetuses versus CTRL. In conclusion, these results provided a baseline of cellular
localization and intensity of a subset of TJ proteins in the porcine MFI and confirmed changes in
the course of infection. Interestingly, only CLDN4 abundance in maternal endothelial cells was
significantly different in PRRSV2 infected IUGR fetuses compared to CTRL and MEC fetuses,
but it did not differ from N-IUGR fetuses.
In chapter three, the expression of CLDN 1, 3, 4, 5, 6, 7, 10, TJP1 and occludin (OCLN)
genes were evaluated by PCR. There were no significant group differences among IUGR and NIUGR
groups, regardless of infection status, that explained the resilience of IUGR fetuses. Across
disease progression groups, elevated CLDN3 and suppressed TJP1 were observed in UNIF fetuses,
CLDN6 expression was lower in PLC when the fetus became infected (HVL-VIA), and CLDN10
expression was upregulated in PLC in fetuses showing evidence of compromise (HVL-MEC-B).
Lastly, OCLN gene expression was higher in the END and PLC following maternal infection. In
conclusion, no relationship between TJ abundance or expression and IUGR resilience were found
following PRRSV infection. However, differences in TJ integrity were observed following
PRRSV2 infection with stepwise changes corresponding with disease progression. These results
provide insights into the potential mechanisms of transplacental PRRSV2 pathogenesis.
Description
Keywords
Porcine reproductive and respiratory syndrome virus, Tight junction protein, Intrauterine growth restriction, Maternal-fetal interface
Citation
Degree
Master of Science (M.Sc.)
Department
Large Animal Clinical Sciences
Program
Large Animal Clinical Sciences