Coxsackievirus Infection Induces Autophagy-Like Vesicles and Megaphagosomes in Pancreatic Acinar Cells In Vivo

Abstract

Autophagy can play an important part in protecting host cells during virus infection, and several viruses have developed strategies by which to evade or even exploit this homeostatic pathway. Tissue culture studies have shown that poliovirus, an enterovirus, modulates autophagy. Herein, we report on in vivo studies that evaluate the effects on autophagy of coxsackievirus B3 (CVB3). We show that in pancreatic acinar cells, CVB3 induces the formation of abundant small autophagy-like vesicles and permits amphisome formation. However, the virus markedly, albeit incompletely, limits the fusion of autophagosomes (and/or amphisomes) with lysosomes, and, perhaps as a result, very large autophagy-related structures are formed within infected cells; we term these structures megaphagosomes. Ultrastructural analyses confirmed that double-membraned autophagy-like vesicles were present in infected pancreatic tissue and that the megaphagosomes were related to the autophagy pathway; they also revealed a highly organized lattice, the individual components of which are of a size consistent with CVB RNA polymerase; we suggest that this may represent a coxsackievirus replication complex. Thus, these in vivo studies demonstrate that CVB3 infection dramatically modifies autophagy in infected pancreatic acinar cells.Macroautophagy-henceforth referred to as autophagy-is an intracellular process that is important for cellular differentiation, homeostasis, and survival. Through autophagy, longlived cytosolic proteins and organelles become encapsulated within double-membraned vesicles, called autophagosomes, which fuse with lysosomes to facilitate degradation of protein and cellular organelles and to promote nutrient recycling/regeneration. Autophagy plays a key role in the host immune response to infection by viruses, bacteria, fungi, and parasites (reviewed in references 10 and 62). Within virus-infected cells, whole virions and/or viral proteins and nucleic acids are captured inside autophagosomes and degraded (following lysosomal fusion) through the process of xenophagy. Moreover, autophagosome fusion with the endosomal/lysosomal pathway facilitates Toll-like receptor recognition of viral materials and delivers endogenous cytosolic viral proteins to the major histocompatibility complex (MHC) class II antigen presentation pathway, which in turn may help to trigger activation of innate immunity (and type I interferon production) and promote antigen presentation to virus-specific CD4 ϩ T cells (reviewed in references 9, 41, 44, 47, 72, and 90). A recent study has shown that autophagy is also involved in the processing and presentation of MHC class I-restricted viral epitopes (13).Given the importance of autophagy in antiviral immunity, it is perhaps not surprising that viruses have evolved mechanisms to evade and/or subvert this pathway (reviewed in references 9, 11, 14, 35, 37, 60, 61, and 77). Several members of the herpesvirus family, most notably herpes simplex virus type 1, inhibit autophagy within an infected cell and encode prote...

Lipid Raft- and Src Family Kinase-Dependent Entry of Coxsackievirus B into Human Placental Trophoblasts

“…Additionally, we found that CVB readily infects BeWo cells and forms characteristic double-membrane replica-tion complexes in BeWo trophoblasts (Fig. 1D), similar to those detected in other cell types following picornavirus infection (46)(47)(48). These data reveal that BeWo trophoblasts are an appropriate polarized cell model for studying CVB interactions at the maternal-fetal interface.…”

Autophagy and pancreatitis

“…6). Indeed, features of impaired autophagy are evident in human disease (3,43,111) and in all experimental models of pancreatitis (1,7,55,65,77,108), including those induced by ethanol ϩ LPS (24) or coxsackievirus infection (51). The lysosomal/autophagic disordering is an early event in development of the disease.…”

Human Rhinovirus 2 Induces the Autophagic Pathway and Replicates More Efficiently in Autophagic Cells

“…Certain picornaviruses, including poliovirus (PV), coxsackievirus, and enterovirus 71 subvert the autophagic pathway to generate double-membraned vesicles, which are thought to serve as substrates for viral genome replication (9,10,12,28). Increased autophagy has a positive effect on PV replication, and PV, human rhinovirus 2 (HRV-2), and HRV-14 induce autophagosome formation, based on a single assay analyzing colocalization of LC3 and the lysosome/endosome marker LAMP1 (10).…”