[Source: Journal of Virology, full page: (LINK). Abstract, edited.]
Junín Virus Promotes Autophagy to Facilitate Viral Life Cycle
Julieta S. Roldán, Nélida A. Candurra, María I. Colombo, Laura R. Delgui
Junín virus (JUNV), a member of Arenaviridae family, is the etiological agent of Argentine hemorrhagic fever (AHF), a potentially deadly, endemic-epidemic disease affecting the population of the most fertile farming land of Argentina. Autophagy is a degradative process with a crucial anti-viral role; however, several viruses subvert this pathway in their benefit. We determined the role of autophagy in JUNV-infected cells analyzing LC3, a cytoplasmic protein (LC3-I) which becomes vesicle membrane-associated (LC3-II) upon induction of autophagy. Cells overexpressing EGFP-LC3 and infected with JUNV showed an increased number of LC3 puncta structures, similar to that obtained after starvation- or Bafilomycin A1- treatment which leads to autophagosome induction or accumulation, respectively. We also monitored the conversion of LC3-I to LC3-II observing LC3-II levels in JUNV-infected cells similar to that observed in starved cells. Additionally, we kinetically studied the number of LC3 dots after JUNV infection and found that the virus activated the pathway as early as 2 h p.i. whereas the UV-inactivated virus did not induce the pathway. Cells subjected to starvation or pre-treated with rapamycin, a pharmacological autophagy inductor, enhanced virus yield. Also, we assayed the replication capacity of JUNV in Atg 5 knock-out or Beclin-1 knock-down cells [both critical components of the autophagic pathway] and found a significant decrease in JUNV replication. Taken together, our results constitute the first study indicating that JUNV infection induces an autophagic response which is functionally required by the virus for efficient propagation.
Mammalian arenaviruses are zoonotic viruses causing asymptomatic and persistent infections in their rodent hosts, but may produce severe and lethal haemorrhagic fevers in humans. Currently, there are neither effective therapeutic options nor effective vaccines, for viral haemorrhagic fevers caused by human pathogenic arenaviruses, except the vaccine Candid #1 against AHF, licensed for human use in endemic areas from Argentina. Since arenaviruses remain a severe threat to global public health, more in-depth knowledge of their replication mechanisms would improve our ability to fight against these viruses. Autophagy is a lysosomal degradative pathway involved in maintaining the cellular homeostasis, representing powerful anti-infective machinery. We showed, for the first time for a member of the Arenaviridae family, a pro-viral role of autophagy in JUNV infection, providing new knowledge in the edge of host-virus interaction. Therefore, modulation of virus-induced autophagy could be used as a strategy to block arenaviruses infections.
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Keywords: Arenavirus; Junin virus; Argentina Hemorrhagic Fever; Viral pathogenesis.