Influenza pathogenesis in pregnancy

Project Summary
Pregnant women are highly vulnerable to influenza A virus (IAV) and are at increased risk for maternal death,
preterm birth and stillbirth. Universal influenza vaccines (UFV) are thought to be possible if conserved regions of
influenza virus are targeted and appropriate immune responses generated. However, relevant animal models are
lacking in which to test such a vaccine, particularly for pregnant women. This proposal is focused on investigating
maternal and placental immune responses to IAV in a pregnant nonhuman primate (NHP) model to understand the
viral-host factors driving enhanced maternal disease. Our central hypothesis is that an aberrant Th17 response
during an acute IAV infection leads to a broadly dysfunctional innate and adaptive immune response that
prevents viral clearance and enhances risk for maternal death and stillbirth. Th17 cells produce high levels of
the inflammatory cytokines IL-17 and IL-2218,19 with early Th17 polarization considered to be critical for IAV
resolution; aberrant and/or late activation of the Th17 pathway by IL-23 in murine models is thought to impair viral
clearance and promote lung injury.20,21 Our preliminary data in a pregnant NHP model of an acute IAV H1N1 infection
demonstrates pneumonia in all animals by Day 5 post-IAV inoculation. In pregnant NHP, influenza disease scores
were higher than non-pregnant animals with notable extra-pulmonary organ injury (myocarditis, white matter injury).
Pregnant NHP demonstrated a nearly absent early Th17 CD4+ T cell response in whole blood and PBMC coupled
with a marked increase in Th17 cells in the lung at peak immunopathology compared to non-pregnant animals.
Inflammatory cytokines and chemokines in the lungs and bronchoalveolar lavage fluid (BAL) were also greater in
pregnant versus non-pregnant animals. In Aim 1, non-pregnant and pregnant pigtail macaques will be challenged
with either IAV H1N1 A/CA/04/09 or H3N2 A/Texas/71/2017 (N=8, each group) and undergo blood and BAL
sampling until necropsy at Day 5 (peak immunopathology). In Aims 1A and 1B, we will determine pregnancy-
specific immune correlates of IAV disease by evaluating the frequency of Th17 CD4+ T cells and a broad spectrum
of innate/adaptive immune responses (i.e. immune cell subsets, cytokines/chemokines, Type I/III interferons) in the
blood, BAL and lung. In Aim 1C, we will evaluate antiviral responses in the placenta linked to adverse pregnancy
outcomes (e.g. cytokines/chemokines, NLRP3 inflammasome activation, CD8+ T cells). In Aim 2, we will use bulk
and single cell RNA-sequencing to define changes in the transcriptome within PBMC, BAL, lung and placenta with
a focus on Th17 transcriptional networks and antiviral innate immune pathways. In summary, the preliminary data
indicates an aberrant Th17 response in pregnant animals, which is critical to promoting viral clearance and
preventing lung injury. These studies will be the first to comprehensively analyze innate/adaptive immune responses
during an acute IAV infection to elucidate the pathogenesis of severe lung disease in pregnant women. Results from
these studies are critical for IAV pandemic preparedness to enable testing of efficacy and safety of new UFV.

Grant Number: 5R01AI164588-05
NIH Institute/Center: NIH
Principal Investigator: Kristina Adams Waldorf