Editorial: Lessons Learned From Chikungunya in the Americas

Macrophage scavenger receptor 1 controls Chikungunya virus infection through autophagy in mice

Macrophage scavenger receptor 1 (MSR1) mediates the endocytosis of modified low-density lipoproteins and plays an important antiviral role. However, the molecular mechanism underlying MSR1 antiviral actions remains elusive. We report that MSR1 activates autophagy to restrict infection of Chikungunya virus (CHIKV), an arthritogenic alphavirus that causes acute and chronic crippling arthralgia. Msr1 expression was rapidly upregulated after CHIKV infection in mice. Msr1 knockout mice had elevated viral loads and increased susceptibility to CHIKV arthritis along with a normal type I IFN response. Induction of LC3 lipidation by CHIKV, a marker of autophagy, was reduced in Msr1^-/- cells. Mechanistically, MSR1 interacted with ATG12 through its cytoplasmic tail and this interaction was enhanced by CHIKV nsP1 protein. MSR1 repressed CHIKV replication through ATG5-ATG12-ATG16L1 and this was dependent on the FIP200-and-WIPI2-binding domain, but not the WD40 domain of ATG16L1. Our results elucidate an antiviral role for MSR1 involving the autophagic function of ATG5-ATG12-ATG16L1.

The Clinical Features, Pathogenesis and Methotrexate Therapy of Chronic Chikungunya Arthritis

Chikungunya fever (CHIKF) is an emerging viral infection that has spread widely, along with its Aedes vectors, throughout the tropics and beyond, causing explosive epidemics of acute illness and persistent disabling arthritis. The rheumatic symptoms associated with chikungunya virus (CHIKV) infection include polyarthralgia, polyarthritis, morning stiffness, joint edema, and erythema. Chronic CHIK arthritis (CCA) often causes severe pain and associated disability. The pathogenesis of CCA is not well understood. Proposed hypotheses include the persistence of a low level of replicating virus in the joints, the persistence of viral RNA in the synovium, and the induction of autoimmunity. In this review, we describe the main hypotheses of CCA pathogenesis, some of which support methotrexate (MTX) treatment which has been shown to be effective in preliminary studies in CCA.