Hypomorphic pathogenic variant in SFTPB leads to adult pulmonary fibrosis.

Biallelic pathogenic variants in the surfactant protein (SP)-B gene (SFTPB) have been associated with fatal forms of interstitial lung diseases (ILD) in newborns and exceptional survival in young children. We herein report the cases of two related adults with pulmonary fibrosis due to a new homozygous SFTPB pathogenic variant, c.582G>A p.(Gln194=). In vitro transcript studies showed that this SFTPB synonymous pathogenic variant induces aberrant splicing leading to three abnormal transcripts with the preservation of the expression of a small proportion of normal SFTPB transcripts. Immunostainings on lung biopsies of the proband showed an almost complete loss of SP-B expression. This hypomorphic splice variant has thus probably allowed the patients' survival to adulthood while inducing an epithelial cell dysfunction leading to ILD. Altogether, this report shows that SFTPB pathogenic variants should be considered in atypical presentations and/or early-onset forms of ILD particularly when a family history is identified.

Tracking receptor motions at the plasma membrane reveals distinct effects of ligands on CCR5 dynamics depending on its dimerization status.

G-protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammation and the principal entry co-receptor for Human Immunodeficiency Viruses type 1 (HIV-1). We used TIRF microscopy and a statistical method to track and classify the motion of different receptor subpopulations. We showed a diversity of ligand-free forms of CCR5 at the cell surface constituted of various oligomeric states and exhibiting transient Brownian and restricted motions. These forms were stabilized differently by distinct ligands. In particular, agonist stimulation restricted the mobility of CCR5 and led to its clustering, a feature depending on ß-arrestin, while inverse agonist stimulation exhibited the opposite effect. These results suggest a link between receptor activation and immobilization. Applied to HIV-1 envelope glycoproteins gp120, our quantitative analysis revealed agonist-like properties of gp120s. Distinct gp120s influenced CCR5 dynamics differently, suggesting that they stabilize different CCR5 conformations. Then, using a dimerization-compromized mutant, we showed that dimerization (i) impacts CCR5 precoupling to G proteins, (ii) is a pre-requisite for the immobilization and clustering of receptors upon activation, and (iii) regulates receptor endocytosis, thereby impacting the fate of activated receptors. This study demonstrates that tracking the dynamic behavior of a GPCR is an efficient way to link GPCR conformations to their functions, therefore improving the development of drugs targeting specific receptor conformations.

Specificities and Commonalities of Carbapenemase-Producing Escherichia coli Isolated in France from 2012 to 2015.

Carbapenemase-producing Escherichia coli (CP-Ec) represents a major public health threat with a risk of dissemination in the community as has occurred for lineages producing extended-spectrum ß-lactamases. To characterize the extent of CP-Ec spread in France, isolates from screening and infection samples received at the French National Reference Center (F-NRC) laboratory for carbapenemase-producing Enterobacterales were investigated. A total of 691 CP-Ec isolates collected between 2012 and 2015 and 22 isolates collected before 2012 were fully sequenced. Analysis of their genome sequences revealed some disseminating multidrug-resistant (MDR) lineages frequently acquiring diverse carbapenemase genes mainly belonging to clonal complex 23 (CC23) (sequence type 410 [ST410]) and CC10 (ST10 and ST167) and sporadic isolates, including rare ST131 isolates (n = 17). However, the most represented sequence type (ST) was ST38 (n = 92) with four disseminated lineages carrying blaOXA-48-like genes inserted in the chromosome. Globally, the most frequent carbapenemase gene (n = 457) was blaOXA-48. It was also less frequently associated with MDR isolates being the only resistance gene in 119 isolates. Thus, outside the ST38 clades, its acquisition was frequently sporadic with no sign of dissemination, reflecting the circulation of the IncL plasmid pOXA-48 in France and its high frequency of conjugation. In contrast, blaOXA-181 and blaNDM genes were often associated with the evolution of MDR E. coli lineages characterized by mutations in ftsI and ompC. IMPORTANCE Carbapenemase-producing Escherichia coli (CP-Ec) might be difficult to detect, as MICs can be very low. However, their absolute number and their proportion among carbapenem-resistant Enterobacterales have been increasing, as reported by WHO and national surveillance programs. This suggests a still largely uncharacterized community spread of these isolates. Here, we have characterized the diversity and evolution of CP-Ec isolated in France before 2016. We show that carbapenemase genes are associated with a wide variety of E. coli genomic backgrounds and a small number of dominant phylogenetic lineages. In a significant proportion of CP-Ec, the most frequent carbapenemase gene blaOXA-48, was detected in isolates lacking any other resistance gene, reflecting the dissemination of pOXA-48 plasmids, likely in the absence of any antibiotic pressure. In contrast, carbapenemase gene transfer may also occur in multidrug-resistant E. coli, ultimately giving rise to at-risk lineages encoding carbapenemases with a high potential of dissemination.

Low CCR5 expression protects HIV-specific CD4+ T cells of elite controllers from viral entry.

HIV elite controllers maintain a population of CD4 + T cells endowed with high avidity for Gag antigens and potent effector functions. How these HIV-specific cells avoid infection and depletion upon encounter with the virus remains incompletely understood. Ex vivo characterization of single Gag-specific CD4 + T cells reveals an advanced Th1 differentiation pattern in controllers, except for the CCR5 marker, which is downregulated compared to specific cells of treated patients. Accordingly, controller specific CD4 + T cells show decreased susceptibility to CCR5-dependent HIV entry. Two controllers carried biallelic mutations impairing CCR5 surface expression, indicating that in rare cases CCR5 downregulation can have a direct genetic cause. Increased expression of ß-chemokine ligands upon high-avidity antigen/TCR interactions contributes to autocrine CCR5 downregulation in controllers without CCR5 mutations. These findings suggest that genetic and functional regulation of the primary HIV coreceptor CCR5 play a key role in promoting natural HIV control.

Functional assessment and phenotypic heterogeneity of SFTPA1 and SFTPA2 mutations in interstitial lung diseases and lung cancer.

INTRODUCTION: Interstitial lung diseases (ILDs) can be caused by mutations in the SFTPA1 and SFTPA2 genes, which encode the surfactant protein (SP) complex SP-A. Only 11 SFTPA1 or SFTPA2 mutations have so far been reported worldwide, of which five have been functionally assessed. In the framework of ILD molecular diagnosis, we identified 14 independent patients with pathogenic SFTPA1 or SFTPA2 mutations. The present study aimed to functionally assess the 11 different mutations identified and to accurately describe the disease phenotype of the patients and their affected relatives. METHODS: The consequences of the 11 SFTPA1 or SFTPA2 mutations were analysed both in vitro, by studying the production and secretion of the corresponding mutated proteins and ex vivo, by analysing SP-A expression in lung tissue samples. The associated disease phenotypes were documented. RESULTS: For the 11 identified mutations, protein production was preserved but secretion was abolished. The expression pattern of lung SP-A available in six patients was altered and the family history reported ILD and/or lung adenocarcinoma in 13 out of 14 families (93%). Among the 28 SFTPA1 or SFTPA2 mutation carriers, the mean age at ILD onset was 45 years (range 0.6-65 years) and 48% underwent lung transplantation (mean age 51 years). Seven carriers were asymptomatic. DISCUSSION: This study, which expands the molecular and clinical spectrum of SP-A disorders, shows that pathogenic SFTPA1 or SFTPA2 mutations share similar consequences for SP-A secretion in cell models and in lung tissue immunostaining, whereas they are associated with a highly variable phenotypic expression of disease, ranging from severe forms requiring lung transplantation to incomplete penetrance.