Sun, Jie

Abstract Infants born prematurely often develop chronic lung diseases including bronchopulmonary dysplasia (BPD). BPD is associated with greatly increased host susceptibility and severe disease development following respiratory viral infection. To this end, we have recently established a neonatal hyperoxia model respiratory viral infection in hosts with lung prematurity and BPD. Using this model, we observed that mice exposed with neonatal hyperoxia (80% oxygen, BPD hosts) developed enhanced diseases following influenza virus or respiratory syncytial virus (RSV) infection compared to those of influenza or RSV-infected control mice. We showed that neonatal hyperoxia leaded to modestly enhanced viral replication in the respiratory tract. Using nanostring immune gene profiling and multiplex cytokine analysis, we found that neonatal hyperoxia markedly enhanced immune-associated gene expression and the production of a number of proinflammatory cytokines and chemokines in the airway compared to those of control mice. Neonatal hyperoxia also increased the accumulation of multiple inflammatory innate cell types that were shown to be pathogenic during respiratory viral infections. Importantly, antiviral T, B cells and NK cells were similar in the lungs between infected neonatal hyperoxia-exposed and control mice, which are consistent with the similar viral clearance kinetics in those mice. Thus, we have successfully established a clinically-relevant mouse model of respiratory viral infection in BPD hosts. We expect to further uncover novel insights on the viral pathogenesis and host disease devlopment in this novel model of respiratory viral infection in hosts with chronic lung diseases.

Abstract Alveolar Macrophages (AMs) are a unique population of innate immune cells that reside in the alveolar space and contribute to accommodate the ever-changing need of the lungs against the external environmental challenges. AMs derive from the fetal origins and are capable of maintaining themselves through self-renewal without the input of hematopoiesis during the adulthood. However, little is known about how aging is influencing the molecular characteristics and heterogeneity of the AMs during homeostasis. Using single-cell RNA sequencing (scRNA-seq) and Seurat clustering, we discovered AMs can be subdivided into different “subsets” with unique molecular characteristics during homeostasis. Interestingly, when we further investigate the AM population with the combined data from the young(~8w) and old(~2y) mice, the data suggested that the proliferating cell fall in the same cluster with reduced number in the old-mice group, while the poised inflammatory cells showed distinct molecular patterns between the group with different age. We hypothesize that the inflammatory and the self-renewal AM subpopulations may be maintained by distinct extracellular signals. With the progress of aging, the self-renewal ability of AMs would reduce because of the number of proliferating cells but not the change of molecular patterns. At the same time, the inflammatory population would change its characteristics with age, and potentially lead to functional change upon activation. Further validation of the AM subset identity as well as the developmental and functional interrelationship of these subsets are required. In addition, the extrinsic and intrinsic signals responsible for the maintenance of these AM subsets are to be explored.

Abstract The role of Bcl6 expression in different immune compartments in regulating anti-tumor immunity is relatively unknown. Previous studies have linked Bcl6 expression in PBMC with poor prognosis in non-small cell lung cancer. We found that high expression of Bcl6 in tumor predicts survival in gastric and ovarian cancers. Using cell type specific conditional knockouts, we were able to investigate the contribution of Bcl6 expression in different lineages in modulating immune response to subcutaneously implanted B16-ova melanoma tumors. Myeloid deficiency of Bcl6 results in decreased tumor growth and metastasis. This is accompanied by enrichment of antigen specific T cells within the tumor. These tumor infiltrating T cells show an increased expression of exhausted markers such as PD-1, Lag-3 and Tim-3. Tumor associated innate cells also upregulate PD-L1. Furthermore, the TILs display an enhanced effector profile measured by robust production of granzyme B, interferon gamma and CCL3 on ex vivo stimulation. This is accompanied by increase in poly-functional CD8 T cells. Our result suggests that Bcl6 expression in the monocyte/macrophage lineage dampens the development of effective anti-tumor immunity and augments immunosuppressive tumor microenvironment. We will elucidate the exact underlying mechanisms and evaluate the translational potential of Bcl6 inhibitors in conjunction with immune checkpoint blockade in the future.

Abstract Background Despite extensive studies of human immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) vaccination, research examining protective correlates of vertical transmission following maternal exposure in pregnancy remain limited. Here, we characterized antibody and cytokine responses in maternal and cord blood following infection or vaccination at various timepoints during gestation. Methods Spike S1 protein-specific binding antibodies and antibodies capable of blocking the interaction between the receptor binding domain (RBD) and the angiotensin converting enzyme 2 (ACE2) were measured in maternal and cord blood by ELISA. Serum concentrations of 74 cytokines/chemokines were measured by multiplex assay. Humoral responses and cytokine levels from matched maternal and fetal cord sera were compared and examined for potential correlations. Results We observed a highly significant correlation between Spike S1-specific antibody titer and RBD-ACE2 blocking antibody activity between maternal and fetal cord serum (p < 2.2e-16, R > 0.90). Blocking antibody activity was significantly higher for mothers infected during the 3rd trimester compared to earlier trimesters; however, vaccinated mothers developed and transferred higher antibody titers with greater RBD-ACE2 blocking antibody activity to their neonates than infected mothers. Furthermore, vaccine-induced Spike S1 IgG transfer ratios (fetal cord/maternal) were significantly higher than those induced by infection (p = 0.002). Multiplex assay showed significantly elevated levels of 33 cytokines/chemokines, mainly pro-inflammatory in infected maternal serum samples, while the paired fetal cord samples exhibited an anti-inflammatory cytokine predominance. Conclusion Our data support selective vertical transmission of potentially protective humoral responses against SARS-CoV-2, especially following vaccination in the 3rd trimester. The anti-inflammatory cytokine predominance in cord blood that persists despite maternal SARS-CoV-2 infection may offset the adverse outcomes of inflammation in pregnancy for the neonate. Disclosures All Authors: No reported disclosures.