Impact of caspase-1/11, -3, -7, or IL-1\u03b2/IL-18 deficiency on rabies virus-induced macrophage cell death and onset of disease

E Kip,S Lamoral,M Kalai,A Francart,T Vanden Berghe,P Vandenabeele,V Suin,F Nazé,R Beyaert,S Van Gucht

doi:10.1038/cddiscovery.2017.12

Abstract

Rabies virus is a highly neurovirulent RNA virus, which causes about 59000 deaths in humans each year. Previously, we described macrophage cytotoxicity upon infection with rabies virus. Here we examined the type of cell death and the role of specific caspases in cell death and disease development upon infection with two laboratory strains of rabies virus: Challenge Virus Standard strain-11 (CVS-11) is highly neurotropic and lethal for mice, while the attenuated Evelyn–Rotnycki–Abelseth (ERA) strain has a broader cell tropism, is non-lethal and has been used as an oral vaccine for animals. Infection of Mf4/4 macrophages with both strains led to caspase-1 activation and IL-1β and IL-18 production, as well as activation of caspases-3, -7, -8, and -9. Moreover, absence of caspase-3, but not of caspase-1 and -11 or -7, partially inhibited virus-induced cell death of bone marrow-derived macrophages. Intranasal inoculation with CVS-11 of mice deficient for either caspase-1 and -11 or -7 or both IL-1β and IL-18 led to general brain infection and lethal disease similar to wild-type mice. Deficiency of caspase-3, on the other hand, significantly delayed the onset of disease, but did not prevent final lethal outcome. Interestingly, deficiency of caspase-1/11, the key executioner of pyroptosis, aggravated disease severity caused by ERA virus, whereas wild-type mice or mice deficient for either caspase-3, -7, or both IL-1β and IL-18 presented the typical mild symptoms associated with ERA virus. In conclusion, rabies virus infection of macrophages induces caspase-1- and caspase-3-dependent cell death. In vivo caspase-1/11 and caspase-3 differently affect disease development in response to infection with the attenuated ERA strain or the virulent CVS-11 strain, respectively. Inflammatory caspases seem to control attenuated rabies virus infection, while caspase-3 aggravates virulent rabies virus infection.

Highlights

Rabies virus is a negative single-stranded RNA virus belonging to the Genus Lyssavirus, Familia Rhabdoviridae
We found that intranasal inoculation of Evelyn–Rotnycki–Abelseth virus (ERA) virus in WT, caspase-3, -7, or IL1β/IL-18− / − mice led to the development of minor symptoms such as weight loss or motoric incoordination from 11–18 days post inoculation (DPI)
Apoptosis and pyroptosis can be induced by a wide variety of stimuli, including viral infection

Summary

INTRODUCTION

Rabies virus is a negative single-stranded RNA virus belonging to the Genus Lyssavirus, Familia Rhabdoviridae. The extrinsic pathway is based on activation of cell death receptors, whereas the intrinsic pathway occurs through the mitochondria. Apoptotic neurons were detected in the brain of mice upon intracranial inoculation of virulent rabies virus.[14,15,16] Jackson et al.[17] suggest that there is an inverse relationship between pathogenicity and neuronal apoptosis and that neuronal apoptosis does not contribute to pathogenicity in human rabies encephalitis,[18] even if apoptosis is detected in brains of human patients.[19] Others reported that rabies virus can infect mouse and human lymphocytes and induce their apoptosis[20,21] or suggested study the activation of apoptotic and pyroptotic pathways in Mf4/4 macrophages. The impact of caspase-1/11, -3, or -7 deficiency on virus-induced cell death was further studied in bone marrow-derived macrophages (BMDM). We examined the impact of a deficiency in caspase-1/11, -3, -7, or IL-1β/IL-18 on the virological and clinical outcome of rabies virus infection in mice

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS