Frequency and characteristics of refractory dyspnea in idiopathic fibrosing interstitial pneumonia.

Patients with idiopathic fibrosing interstitial pneumonias (f-IIPs) mainly suffer from dyspnea. Refractory dyspnea, defined as persistent dyspnea despite optimal treatment, could be the signal to prescribe dyspnea relievers. We aimed to examine the prevalence and characteristics of refractory dyspnea in consecutive patients with f-IIPs. Refractory dyspnea was defined by an mMRC≥3 and also by a VAS dyspnea score≥2 at rest. The sensory and affective characteristics of refractory dyspnea (mMRC≥3) and associated quality of life (QoL) anxiety and depression were compared with non-refractory dyspnea (mMRC1-2) using the Multidimensional Dyspnea Profile (MDP), King's Brief Interstitial Lung Disease (KBILD) and Hospital Anxiety and Depression scale (HADs). We included 40 patients (24 men), aged 72 [68-79], FVC of 71 % [59-86] and DLCO 47 % [40-49]. Refractory dyspnea, was found in 38 % (95%CI:23-54) when defined by mMRC≥3 and in 67 % (95%CI:50-81) using a resting VAS dyspnea score ≥2. The agreement between the two definitions was low. Patients with refractory dyspnea (mMRC≥3) were more often women (60 % vs.28 %, p = 0.046), had a lower DLCO (24 % [22-43] vs.47 % [43-51], p = 0.014) and more frequently used oxygen (60 % vs.12 %, p = 0.003); they experience more intense air hunger (5/10 [3-6] vs.2/10 [0-5], p = 0.018)). No significant differences were observed in VAS, MDP, KBILD, or HADs scores between refractory and non-refractory dyspnea patients. Our results indicate a significant frequency of refractory dyspnea in patients with f-IIPs and an association with air hunger but no impact on the affective dimension of dyspnea, anxiety, depression and QoL, suggesting that the mMRC score might not accurately identify patients distressed by their breathlessness.

Investigation of the role of GBF1 in the replication of positive-sense single-stranded RNA viruses.

GBF1 has emerged as a host factor required for the replication of positive-sense single-stranded RNA viruses of different families, but its mechanism of action is still unknown. GBF1 is a guanine nucleotide exchange factor for Arf family members. Recently, we identified Arf4 and Arf5 (class II Arfs) as host factors required for the replication of hepatitis C virus (HCV), a GBF1-dependent virus. To assess whether a GBF1/class II Arf pathway is conserved among positive-sense single-stranded RNA viruses, we investigated yellow fever virus (YFV), Sindbis virus (SINV), coxsackievirus B4 (CVB4) and human coronavirus 229E (HCoV-229E). We found that GBF1 is involved in the replication of these viruses. However, using siRNA or CRISPR-Cas9 technologies, it was seen that the depletion of Arf1, Arf3, Arf4 or Arf5 had no impact on viral replication. In contrast, the depletion of Arf pairs suggested that class II Arfs could be involved in HCoV-229E, YFV and SINV infection, as for HCV, but not in CVB4 infection. In addition, another Arf pair, Arf1 and Arf4, appears to be essential for YFV and SINV infection, but not for infection by other viruses. Finally, CVB4 infection was not inhibited by any combination of Arf depletion. We conclude that the mechanism of action of GBF1 in viral replication appears not to be conserved, and that a subset of positive-sense single-stranded RNA viruses from different families might require class II Arfs for their replication.

Identification of class II ADP-ribosylation factors as cellular factors required for hepatitis C virus replication.

GBF1 is a host factor required for hepatitis C virus (HCV) replication. GBF1 functions as a guanine nucleotide exchange factor for G-proteins of the Arf family, which regulate membrane dynamics in the early secretory pathway and the metabolism of cytoplasmic lipid droplets. Here we established that the Arf-guanine nucleotide exchange factor activity of GBF1 is critical for its function in HCV replication, indicating that it promotes viral replication by activating one or more Arf family members. Arf involvement was confirmed with the use of two dominant negative Arf1 mutants. However, siRNA-mediated depletion of Arf1, Arf3 (class I Arfs), Arf4 or Arf5 (class II Arfs), which potentially interact with GBF1, did not significantly inhibit HCV infection. In contrast, the simultaneous depletion of both Arf4 and Arf5, but not of any other Arf pair, imposed a significant inhibition of HCV infection. Interestingly, the simultaneous depletion of both Arf4 and Arf5 had no impact on the activity of the secretory pathway and induced a compaction of the Golgi and an accumulation of lipid droplets. A similar phenotype of lipid droplet accumulation was also observed when GBF1 was inhibited by brefeldin A. In contrast, the simultaneous depletion of both Arf1 and Arf4 resulted in secretion inhibition and Golgi scattering, two actions reminiscent of GBF1 inhibition. We conclude that GBF1 could regulate different metabolic pathways through the activation of different pairs of Arf proteins.