Gammaherpesvirus infection modulates the temporal and spatial expression of SCGB1A1 (CCSP) and BPIFA1 (SPLUNC1) in the respiratory tract

BPIFA1 is a secreted biomarker of differentiating human airway epithelium

In vitro culture and differentiation of human-derived airway basal cells under air-liquid interface (ALI) into a pseudostratified mucociliated mucosal barrier has proven to be a powerful preclinical tool to study pathophysiology of respiratory epithelium. As such, identifying differentiation stage-specific biomarkers can help investigators better characterize, standardize, and validate populations of regenerating epithelial cells prior to experimentation. Here, we applied longitudinal transcriptomic analysis and observed that the pattern and the magnitude of OMG, KRT14, STC1, BPIFA1, PLA2G7, TXNIP, S100A7 expression create a unique biosignature that robustly indicates the stage of epithelial cell differentiation. We then validated our findings by quantitative hemi-nested real-time PCR from in vitro cultures sourced from multiple donors. In addition, we demonstrated that at protein-level secretion of BPIFA1 accurately reflects the gene expression profile, with very low quantities present at the time of ALI induction but escalating levels were detectable as the epithelial cells terminally differentiated. Moreover, we observed that increase in BPIFA1 secretion closely correlates with emergence of secretory cells and an anti-inflammatory phenotype as airway epithelial cells undergo mucociliary differentiation under air-liquid interface in vitro.

The potential applications of microparticles in the diagnosis, treatment, and prognosis of lung cancer

Microparticles (MPs) are 100–1000 nm heterogeneous submicron membranous vesicles derived from various cell types that express surface proteins and antigenic profiles suggestive of their cellular origin. MPs contain a diverse array of bioactive chemicals and surface receptors, including lipids, nucleic acids, and proteins, which are essential for cell-to-cell communication. The tumour microenvironment (TME) is enriched with MPs that can directly affect tumour progression through their interactions with receptors. Liquid biopsy, a minimally invasive test, is a promising alternative to tissue biopsy for the early screening of lung cancer (LC). The diverse biomolecular information from MPs provides a number of potential biomarkers for LC risk assessment, early detection, diagnosis, prognosis, and surveillance. Remodelling the TME, which profoundly influences immunotherapy and clinical outcomes, is an emerging strategy to improve immunotherapy. Tumour-derived MPs can reverse drug resistance and are ideal candidates for the creation of innovative and effective cancer vaccines. This review described the biogenesis and components of MPs and further summarised their main isolation and quantification methods. More importantly, the review presented the clinical application of MPs as predictive biomarkers in cancer diagnosis and prognosis, their role as therapeutic drug carriers, particularly in anti-tumour drug resistance, and their utility as cancer vaccines. Finally, we discussed current challenges that could impede the clinical use of MPs and determined that further studies on the functional roles of MPs in LC are required.

Constitutive TRIM22 Expression in the Respiratory Tract Confers a Pre-Existing Defence Against Influenza A Virus Infection

The induction of antiviral effector proteins as part of a homeostatically controlled innate immune response to infection plays a critical role in limiting the propagation and transmission of respiratory pathogens. However, the prolonged induction of this immune response can lead to lung hyperinflammation, tissue damage, and respiratory failure. We hypothesized that tissues exposed to the constant threat of infection may constitutively express higher levels of antiviral effector proteins to reduce the need to activate potentially harmful innate immune defences. By analysing transcriptomic data derived from a range of human tissues, we identify lung tissue to express constitutively higher levels of antiviral effector genes relative to that of other mucosal and non-mucosal tissues. By using primary cell lines and the airways of rhesus macaques, we show the interferon-stimulated antiviral effector protein TRIM22 (TRIpartite Motif 22) to be constitutively expressed in the lung independently of viral infection or innate immune stimulation. These findings contrast with previous reports that have shown TRIM22 expression in laboratory-adapted cell lines to require interferon stimulation. We demonstrate that constitutive levels of TRIM22 are sufficient to inhibit the onset of human and avian influenza A virus (IAV) infection by restricting the onset of viral transcription independently of interferon-mediated innate immune defences. Thus, we identify TRIM22 to confer a pre-existing (intrinsic) intracellular defence against IAV infection in cells derived from the respiratory tract. Our data highlight the importance of tissue-specific and cell-type dependent patterns of pre-existing immune gene expression in the intracellular restriction of IAV from the outset of infection.

A Three-Dimensional Human Tissue-Engineered Lung Model to Study Influenza A Infection

Influenza A virus (IAV) claims ∼250,000-500,000 lives annually worldwide. Currently, there are a few in vitro models available to study IAV immunopathology. Monolayer cultures of cell lines and primary lung cells (two-dimensional [2D] cell culture) is the most commonly used tool, however, this system does not have the in vivo-like structure of the lung and immune responses to IAV as it lacks the three-dimensional (3D) tissue structure. To recapitulate the lung physiology in vitro, a system that contains multiple cell types within a 3D environment that allows cell movement and interaction would provide a critical tool. In this study, as a first step in designing a 3D-Human Tissue-Engineered Lung Model (3D-HTLM), we describe the 3D culture of primary human small airway epithelial cells (HSAEpCs) and determined the immunophenotype of this system in response to IAV infections. We constructed a 3D chitosan-collagen scaffold and cultured HSAEpCs on these scaffolds at air-liquid interface (ALI). These 3D cultures were compared with 2D-cultured HSAEpCs for viability, morphology, marker protein expression, and cell differentiation. Results showed that the 3D-cultured HSAEpCs at ALI yielded maximum viable cells and morphologically resembled the in vivo lower airway epithelium. There were also significant increases in aquaporin-5 and cytokeratin-14 expression for HSAEpCs cultured in 3D compared to 2D. The 3D culture system was used to study the infection of HSAEpCs with two major IAV strains, H1N1 and H3N2. The HSAEpCs showed distinct changes in marker protein expression, both at mRNA and protein levels, and the release of proinflammatory cytokines. This study is the first step in the development of the 3D-HTLM, which will have wide applicability in studying pulmonary pathophysiology and therapeutics development.

Comparative Proteomic Analysis of Exosomes and Microvesicles in Human Saliva for Lung Cancer

Extracellular vesicles (EVs) are cell-derived microparticles present in most body fluids, mainly including microvesicles and exosomes. EV-harbored proteins have emerged as novel biomarkers for the diagnosis and prediction of different cancers. We successfully isolated microvesicles and exosomes from human saliva, which were further characterized comprehensively. Salivary EV protein profiling in normal subjects and lung cancer patients was systematically compared through utilizing LC-MS/MS-based label-free quantification. 785 and 910 proteins were identified from salivary exosomes and microvesicles, respectively. According to statistical analysis, 150 and 243 proteins were revealed as dysregulated candidates in exosomes and microvesicles for lung cancer. Among them, 25 and 40 proteins originally from distal organ cells were found in the salivary exosomes and microvesicles of lung cancer patients. In particular, 5 out of 25 and 9 out of 40 are lung-related proteins. Six potential candidates were selected for verification by Western blot, and four of them, namely, BPIFA1, CRNN, MUC5B, and IQGAP, were confirmed either in salivary microvesicles or in exosomes. Our data collectively demonstrate that salivary EVs harbor informative proteins that might be used for the detection of lung cancer through a noninvasive way.

An innate defense peptide BPIFA1/SPLUNC1 restricts influenza A virus infection

The airway epithelium secretes proteins that function in innate defense against infection. Bactericidal/permeability-increasing fold-containing family member A1 (BPIFA1) is secreted into airways and has a protective role during bacterial infections, but it is not known whether it also has an antiviral role. To determine a role in host defense against influenza A virus (IAV) infection and to find the underlying defense mechanism, we developed transgenic mouse models that are deficient in BPIFA1 and used these, in combination with in vitro three-dimensional mouse tracheal epithelial cell (mTEC) cultures, to investigate its antiviral properties. We show that BPIFA1 has a significant role in mucosal defense against IAV infection. BPIFA1 secretion was highly modulated after IAV infection. Mice deficient in BPIFA1 lost more weight after infection, supported a higher viral load and virus reached the peripheral lung earlier, indicative of a defect in the control of infection. Further analysis using mTEC cultures showed that BPIFA1-deficient cells bound more virus particles, displayed increased nuclear import of IAV ribonucleoprotein complexes, and supported higher levels of viral replication. Our results identify a critical role of BPIFA1 in the initial phase of infection by inhibiting the binding and entry of IAV into airway epithelial cells.

Cutting Edge: Fetal/Placental Type I IFN Can Affect Maternal Survival and Fetal Viral Load during Viral Infection

Pregnant women have greater mortality and complications associated with viral infections compared with the general population, but the reason for the increased susceptibility is not well defined. Placenta type I IFN is an important immune modulator and protects the pregnancy. We hypothesized that loss of placental IFN affects the regulation of the maternal immune system, resulting in the differential response to infections observed in pregnancy. Pregnant mice lacking the IFN-α/β receptor (IFNAR) became viremic and had higher mortality compared with nonpregnant animals. Notably, an embryo with functional IFN signaling alone was sufficient to rescue the pregnant IFNAR-/- dam from virus-associated demise. Placental IFN was also an important regulator of viral replication in placental tissue and significantly affected viral transmission to the fetus. These findings highlight the role of fetal/placental IFN in the modulation of viral infection in the mother and fetus.