Biology subjects

Bouin, A.

Publications and source records attributed to Bouin, A..

3 recordsLinked to original sources

bioRxiv2025

Differences between human and rodent nitric oxide production dictate susceptibility to tick-borne Rickettsia.

Arthropod-borne pathogens cause serious human infections, yet they only cause limited disease in rodent reservoirs. Wild type mice resist infection by tick-borne Rickettsia parkeri, which causes spotted fever in humans, and it remains unclear why humans are vulnerable. Here, we report that whereas mouse type I interferon (IFN-I) or interferon-{gamma} (IFN-{gamma}) dramatically restrict R. parkeri in macrophages, human interferons do not. Differential RNA-seq revealed a significant induction of nitric oxide synthase 2 (Nos2, encoding inducible nitric oxide synthase, iNOS) in infected mouse but not human macrophages upon interferon treatment. Chemical iNOS inhibition or Nos2 deletion restored IFN-{gamma}-mediated restriction in mouse cells. Human cells treated with cytokine cocktails or with iNOS cofactors and substrates were still unable to restrict R. parkeri. In vivo, whereas wild type mice restricted R. parkeri, infected Nos2-/-mice developed mild skin eschars, recapitulating a key human disease manifestation. Together, our findings suggest that there is a threshold of NO production required to restrict R. parkeri, which mouse cells reach but human cells do not, and this is a key explanation for why humans develop tick-borne rickettsial diseases while rodents can be tolerant, asymptomatic reservoirs. Differences in NO abundance may provide an evolutionary explanation for human susceptibility to pathogens that propagate themselves in rodent reservoirs.

microbiology↗

bioRxiv2024

Cooperative Role of PACT and ADAR1 in Preventing Aberrant PKR Activation by Self-Derived Double-Stranded RNA

Double-stranded RNAs (dsRNAs) produced during viral infections are recognized by the innate immune sensor protein kinase R (PKR), triggering a host translation shutoff that inhibits viral replication and propagation. Given the harmful effects of uncontrolled PKR activation, cells must tightly regulate PKR to ensure that its activation occurs only in response to viral infections, not endogenous dsRNAs. Here, we use CRISPR-Translate, a FACS-based genome-wide CRISPR-Cas9 knockout screening method that exploits translation levels as a readout and identifies PACT as a key inhibitor of PKR during viral infection. We find that cells deficient for PACT hyperactivate PKR in response to several different RNA viruses, raising the question of why cells need to limit PKR activity. Our results demonstrate that PACT cooperates with ADAR1 to suppress PKR activation from self-dsRNAs in uninfected cells. The simultaneous deletion of PACT and ADAR1 results in synthetic lethality, which can be fully rescued in PKR-deficient cells. We propose that both PACT and ADAR1 act as essential barriers against PKR, creating a threshold of tolerable levels to endogenous dsRNA in cells without activating PKR-mediated translation shutdown and cell death.

microbiology↗

bioRxiv2022

Enterovirus-cardiomyocyte interactions: impact of terminally deleted genomic RNAs on viral and host functions

Group B enteroviruses, including coxsackievirus B3 (CVB3), can persistently infect cardiac tissue and cause dilated cardiomyopathy. Persistence is linked to 5 terminal deletions of viral genomic RNAs that have been detected together with minor populations of full-length genomes in human infections. In this study, we explored the functions and interactions of the different viral RNA forms found in persistently-infected patients and their putative role(s) in pathogenesis. Since enterovirus cardiac pathogenesis is linked to the viral proteinase 2A, we investigated the effect of different terminal genomic RNA deletions on 2A activity. We discovered that 5 terminal deletions in CVB3 genomic RNAs decreased the proteinase activity of 2A but could not abrogate it. Using newly-generated viral reporters encoding nano-luciferase, we found that 5 terminal deletions resulted in decreased levels of viral protein and RNA synthesis in singly-transfected cardiomyocyte cultures. Unexpectedly, when full-length and terminally deleted forms were co-transfected into cardiomyocytes, a cooperative interaction was observed, leading to increased viral RNA and protein production. However, when viral infections were carried out in cells harboring 5 terminally deleted CVB3 RNAs, a decrease in infectious particle production was observed. Our results provide a possible explanation for the necessity of full-length viral genomes during persistent infection, as they would stimulate efficient viral replication compared to that of the deleted genomes alone. To avoid high levels of viral particle production that would trigger cellular immune activation and host cell death, the terminally deleted RNA forms act to limit the production of viral particles, possibly as trans-dominant inhibitors. ImportanceEnteroviruses like coxsackievirus B3 are able to initiate acute infections of cardiac tissue and, in some cases, to establish a long-term persistent infection that can lead to serious disease sequelae, including dilated cardiomyopathy. Previous studies have demonstrated the presence of 5 terminally-deleted forms of enterovirus RNAs in heart tissues derived from patients with dilated cardiomyopathy. These deleted RNAs are found in association with very low levels of full-length enterovirus genomic RNAs, an interaction that may facilitate continued persistence while limiting virus particle production. Even in the absence of detectable infectious virus particle production, these deleted viral RNA forms express viral proteinases at levels capable of causing viral pathology. Our studies provide mechanistic insights into how full length and deleted forms of enterovirus RNA cooperate to stimulate viral protein and RNA synthesis without stimulating infectious viral particle production. They also highlight the importance of targeting enteroviral proteinases to inhibit viral replication while at the same time limiting the long-term pathologies they trigger.

microbiology↗