Respiratory Syncytial Virus Replication Is Promoted by Autophagy-Mediated Inhibition of Apoptosis

Abstract

Respiratory syncytial virus (RSV) is the main cause of acute lower respiratory tract infection (ALRI) in children worldwide. Virus-host interactions affect the progression and prognosis of the infection. Autophagy plays important roles in virus-host interactions. Respiratory epithelial cells serve as the front line of host defense during RSV infection, However, it is still unclear how they interact with RSV. In this study, we found that RSV induced autophagy that favored RSV replication and exacerbated lung pathology Mechanistically, RSV induced complete autophagy flux through reactive oxygen species (ROS) generation and activation of the AMP-activated protein kinase/mammalian target of rapamycin (AMPK-MTOR) signaling pathway in HEp-2 cells. Furthermore, we evaluated the functions of autophagy in RSV replication and found that RSV replication was increased in HEp-2 cells treated with rapamycin but decreased remarkably in cells treated with 3-methylademine (3-MA) or wortmannin. Knockdown key molecules in the autophagy pathway with short hairpinp RNA (shRNA) against autophagy-related gene 5 (), autophagy-related gene 7 (), or or treatment with ROS scavenger N-acetyl-l-cysteine (NAC) and AMPK inhibitor (compound C) suppressed RSV replication. 3-MA or sh significantly decreased cell viability and increased cell apoptosis at 48 hours postinfection (hpi). Blocking apoptosis with Z-VAD-FMK partially restored virus replication at 48 hpi. Those results provide strong evidence that autophagy may function as a proviral mechanism in a cell-intrinsic manner during RSV infection. An understanding of the mechanisms that respiratory syncytial virus utilizes to interact with respiratory epithelial cells is critical to the development of novel antiviral strategies. In this study, we found that RSV induces autophagy through a ROS-AMPK signaling axis, which in turn promotes viral infection. Autophagy favors RSV replication through blocking cell apoptosis at 48 hpi. Mechanistically, RSV induces mitophagy, which maintains mitochondrial homeostasis and therefore decreases cytochrome release and apoptosis induction. This study provides a novel insight into this virus-host interaction, which may help to exploit new antiviral treatments targeting autophagy processes.

Zebrafish C-reactive protein isoforms inhibit SVCV replication by blocking autophagy through interactions with cell membrane cholesterol

“…The results showed a significant reduction in the antiviral effect of each of the three compounds after treatment with the oxidative stress inhibitor NAC (Fig. 6D) 66 . In parallel, it was also demonstrated a direct increase of intracellular ROS levels in CRP-overexpressing ZF4 cells (Fig.…”

“…Many viruses, including those of fish, activate/need autophagy to replicate 58,59,66,[78][79][80] . In this regard, there are some previous studies that have analysed the influence of autophagy on SVCV infection 54,57,58 ; however, the conclusions of these studies are contradictory with respect to the activation of autophagy as either a negative regulatory mechanism 54,57 or, as determined more recently, a mechanism required by the virus for replication 58 .…”

“…Similarly, treatment with N-acetyl cysteine (NAC) (Fig. 6D), a hijacker of reactive oxygen species (ROS) with the ability to block/inhibit autophagy 66 , did not affect the replication of SVCV when used alone, but it did revert the inhibitory effect induced by the CRP-mix, 25-HOC and/or MBCD by ~50% (Fig. 6C).…”

Orchestrated efforts on host network hijacking: Processes governing virus replication

“…Promoting autophagy while suppressing apoptosis during the early stage of virus infection is common for many viruses. This is because that amphisome formation, nutrient, and energy supply are necessary during virus entry, delivery, and replication, and it is important to maintain a viable host cellular environment before the maturation of viral particles [138]. Late stage suppression of autophagy and activation of apoptosis is favorable for successful infection of many viruses.…”

Operation of mitochondrial machinery in viral infection-induced immune responses

“…Subsequently, the interaction between the matrix protein, mitochondrial Tu translation elongation factor and LC3 proteins regulates the formation of the autophagosome, the induction of mitophagy and the inhibition of the type I IFN response [49]. Respiratory syncytial virus (RSV) activates the autophagocytic program and induces mitophagy through a mechanism that decreases the release of cytochrome C and blocks the apoptotic mechanism [50]. Measles virus infection activates SQSTM1/p62-mediated mitophagy and decreases mitochondrion-tethered MAVS, leading to the suppression of the innate immune response in non-small-cell lung cancer [51].…”