Depletion of TAX1BP1 Amplifies Innate Immune Responses during Respiratory Syncytial Virus Infection

Abstract

Respiratory syncytial virus (RSV) is the main cause of acute respiratory infections in young children, and also has a major impact on the elderly and immunocompromised people. In the absence of a vaccine or efficient treatment, a better understanding of RSV interactions with the host antiviral response during infection is needed. Previous studies revealed that cytoplasmic inclusion bodies (IBs) where viral replication and transcription occur could play a major role in the control of innate immunity during infection by recruiting cellular proteins involved in the host antiviral response. We recently showed that the morphogenesis of IBs relies on a liquid-liquid phase separation mechanism depending on the interaction between viral nucleoprotein (N) and phosphoprotein (P). These scaffold proteins are expected to play a central role in the recruitment of cellular proteins to IBs. Here, we performed a yeast two-hybrid screen using RSV N protein as a bait, and identified the cellular protein TAX1BP1 as a potential partner of this viral protein. This interaction was validated by pulldown and immunoprecipitation assays. We showed that TAX1BP1 suppression has only a limited impact on RSV infection in cell cultures. However, RSV replication is decreased in TAX1BP1-deficient mice (TAX1BP1 KO ), whereas the production of inflammatory and antiviral cytokines is enhanced. In vitro infection of wild-type or TAX1BP1 KO alveolar macrophages confirmed that the innate immune response to RSV infection is enhanced in the absence of TAX1BP1. Altogether, our results suggest that RSV could hijack TAX1BP1 to restrain the host immune response during infection. Importance Respiratory syncytial virus (RSV), which is the leading cause of lower respiratory tract illness in infants, still remains a medical problem in the absence of vaccine or efficient treatment. This virus is also recognized as a main pathogen in the elderly and immunocompromised people, and the occurrence of co-infections (with other respiratory viruses and bacteria) amplifies the risks of developing respiratory distress. In this context, a better understanding of the pathogenesis associated to viral respiratory infections, which depends on both viral replication and the host immune response, is needed. The present study reveals that the cellular protein TAX1BP1, which interacts with the RSV nucleoprotein N, participates in the control of the innate immune response during RSV infection, suggesting that N-TAX1BP1 interaction represents a new target for the development of antivirals.

How RSV Proteins Join Forces to Overcome the Host Innate Immune Response

“…Based on this clarified mechanism of the A20 protein complex [111] and the recent findings that RSV N interacts with TAX1BP1 [106], we could hypothesize that RSV N facilitates the assembly of this multiprotein complex (Figure 5). In this way, RSV N would be able to restrain the innate immune response during infection.…”

“…In parallel, higher levels of IFN-α and TNF-α were detected in the lungs of TAX1BP1 knockout mice compared to wildtype mice. Infection of alveolar macrophages isolated from TAX1BP1 knockout mice resulted in enhanced secretion of antiviral and inflammatory cytokines compared to RSVinfected macrophages isolated from wild-type mice [106]. These findings suggest a proviral role of TAX1BP1 during RSV replication by participating in the attenuation of the host antiviral and inflammatory response.…”

“…Another immunomodulatory mechanism is related to the interaction of N with host Tax1-binding protein 1 (TAX1BP1). This interaction was recently identified in a yeast two-hybrid screen using RSV N as a bait [106]. The interaction was further validated by GST-pulldown and by co-IP in BSRT7 cells.…”

Molecular mechanisms and cellular functions of liquid-liquid phase separation during antiviral immune responses

“…Depletion of WDR5 has been shown to enhance the induction of IFN-β during MeV infection ( 67 ). Additionally, the Tax1-binding protein 1 (TAX1BP1), which is directly involved in the negative regulation of NF-κB and IRF3 signaling pathways, has been identified as a cellular partner of RSV N protein ( 174 ). The depletion of TAX1BP1 resulted in enhanced antiviral and inflammatory responses and restricted RSV replication.…”

Early innate immune response triggered by the human respiratory syncytial virus and its regulation by ubiquitination/deubiquitination processes

“…In line with this, our group found that downregulation of A20, TAX1BP1, or ABIN1 in HRSV infection increased the early innate immune response and reduced virus production in epithelial cells [ 108 ]. Accordingly, enhanced expression of inflammatory and anti-viral cytokines has been observed in TAX1BP1 knockout mice infected with HRSV [ 32 ].…”