Influenza A virus interactions with macrophages: Lessons from epithelial cells
CELLULAR MICROBIOLOGY
Authors: Meischel, Tina; Villalon-Letelier, Fernando; Saunders, Philippa M.; Reading, Patrick C.; Londrigan, Sarah L.
Abstract
Influenza viruses are an important cause of respiratory infection worldwide. In humans, infection with seasonal influenza A virus (IAV) is generally restricted to the respiratory tract where productive infection of airway epithelial cells promotes viral amplification, dissemination, and disease. Alveolar macrophages (M phi) are also among the first cells to detect and respond to IAV, where they play a pivotal role in mounting effective innate immune responses. In contrast to epithelial cells, IAV infection of M phi is a "dead end" for most seasonal strains, where replication is abortive and newly synthesised virions are not released. Although the key replicative stages leading to productive IAV infection in epithelial cells are defined, there is limited knowledge about the abortive IAV life cycle in M phi. In this review, we will explore host factors and viral elements that support the early stages (entry) through to the late stages (viral egress) of IAV replication in epithelial cells. Similarities, differences, and unknowns for each key stage of the IAV replicative cycle in M phi will then be highlighted. Herein, we provide mechanistic insights into M phi-specific control of seasonal IAV replication through abortive infection, which may in turn, contribute to effective host defence.
Mycobacterial immunomodulation and viral manipulation of neuronal copper efflux in the setting of sporadic Parkinson's disease: A multi- hit, outside - in hypothesis of its pathogenesis
MEDICAL HYPOTHESES
Authors: Vavougios, George D.
Abstract
Following Braak's hypothesis on the infectious pathogenesis of sporadic Parkinson's disease (sPD), several bacteria and viruses have been investigated as likely culprits. Recent research has focused on neuroinvasive influenza A viruses (IAV), whereas a genetic link between sPD and tuberculosis has arisen in LRRK2 - dependent maturation of the phagosome. An integrative, outside - in, multi - hit hypothesis is presented here, where (a) mycobacterial immunomodulation creates a phagocyte niche along with cytokine mediated, site specific (i.e. the gut) alterations of both immunity and the microbiome, (b) copper modulating IAVs gain latency in and control over phagocytes and their phenotypes, (c) gain access to the central nervous system (CNS) via the olfactory and vagus nerves in subsequent infection cycles, (d) induce indolent neuroinflammation characterized by perturbed intraneuronal copper compartmentalization and (e) produce alpha - synuclein (alpha Syn) pathology at least in part via copper - induced aggregation and misfolding as well as potential synergy with other underlying, corroborating factors (either genetic or acquired) contributing to dopaminergic neurodegeneration. This hypothesis explores recently arisen evidence for each step of this process, as well as pre-existing, yet unexplored overlapping pathophysiological characteristics of sPD with mycobacterial and IAV infections. The implications of this proposed pathogenic model extend both in sPD research (i.e. determining non - tuberculous mycobacteria as the first hit organism, inactivating IAV - induced copper hijacking), as well as therapeutics.