Perception de l'environnement et réponse adaptative chez la pneumocoque (caractérisation fonctionnelle de gènes impliqués dans la régulation de la compétence et de la virulence)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Validation de l’outil aequorine pour le dosage du calcium libre cytoplasmique par chimioluminescence chez Streptococcus pneumoniae

Streptococcus pneumoniae est une bactérie pathogène extracellulaire, transformable par l’ADN en solution. Il a été montré que le transport du calcium joue un rôle clé dans sa croissance végétative, la compétence pour la transformabilité génétique et la virulence expérimentale. Afin de préciser la localisation du calcium dans la bactérie, nous avons cloné l’ADN complémentaire de l’apoaequorine dans le chromosome de Streptococcus pneumoniae. Ceci a permis la reconstitution du système aequorine in vivo et les mesures par chimioluminescence de la concentration cytoplasmique en calcium libre. La concentration cytoplasmique en calcium est de 2 µM à l’équilibre et peut atteindre 14 µM après addition de calcium dans la suspension bactérienne. Cette augmentation de la concentration intracytoplasmique en calcium libre en réponse à un gradient extérieur de calcium implique un transport actif sensible au DMB et dépend de la vitesse initiale du transport de calcium

Clinical performance of a rapid test compared to a microplate test to detect total anti SARS-CoV-2 antibodies directed to the spike protein

International audienceContents lists available at ScienceDirect Journal of Clinical Virology journal homepage: www.elsevier.com/locate/jcv Clinical performance of a rapid test compared to a microplate test to detect total anti SARS-CoV-2 antibodies directed to the spike protein The recent emergence of the SARS-CoV-2 pandemic has posed for-midable challenges for clinical laboratories. While immunoassays are already available, their diagnostic accuracy and optimal use remain undefined. Serologic tests could be used as complements to assays for virus nucleic acid in the diagnosis of COVID-19 [1–3]. Serologic assays that accurately assess prior infection and immunity to SARS–CoV-2 are essential for retrospective diagnosis, epidemiologic studies, ongoing surveillance and vaccine studie

Vectorial Release of Human RNA Viruses from Epithelial Cells

International audienceEpithelial cells are apico-basolateral polarized cells that line all tubular organs and are often targets for infectious agents. This review focuses on the release of human RNA virus particles from both sides of polarized human cells grown on transwells. Most viruses that infect the mucosa leave their host cells mainly via the apical side while basolateral release is linked to virus propagation within the host. Viruses do this by hijacking the cellular factors involved in polarization and trafficking. Thus, understanding epithelial polarization is essential for a clear understanding of virus pathophysiology

Hepatitis E Pathogenesis

Although most hepatitis E virus (HEV) infections are asymptomatic, some can be severe, causing fulminant hepatitis and extra-hepatic manifestations, including neurological and kidney injuries. Chronic HEV infections may also occur in immunocompromised patients. This review describes how our understanding of the pathogenesis of HEV infection has progressed in recent years

Zika Virus Infection and Prolonged Viremia in Whole-Blood Specimens

We tested whole-blood and plasma samples from immunocompetent patients who had had benign Zika virus infections and found that Zika virus RNA persisted in whole blood substantially longer than in plasma. This finding may have implications for diagnosis of acute symptomatic and asymptomatic infections and for testing of blood donations

Post-Vaccination Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibody Kinetics and Protection Duration

International audienceDear Editor,It will be difficult to mount an effective response to the SARS-CoV-2 pandemic without a clear understanding of the kinetics of the immune response to the virus. A recent study looked at the kinetics of antibody avidity maturation in COVID-19 patients and showed that IgG avidity increased form 1-90 days associated with disease severity. In a complementary way, another study in healthcare workers (HCWs) showed that a total antibody concentration greater than 141 BAU/ml provides 89.3% protection against SARS-CoV-2 infection. In this study we determined the duration of protection conferred by the total antibodies taking into account the pre-vaccination infectious status and the waninghumoral immunity

Performance of an antigen assay for diagnosing acute hepatitis E virus genotype 3 infection

International audienceBackground: Hepatitis E virus (HEV) is a major cause of hepatitis worldwide. Its diagnosis is based on the detection of anti-HEV IgM and/or HEV-RNA.Objective: To evaluate the performance of the Wantaï HEV-antigen (Ag) ELISA(Plus) assay for diagnosing acute HEV infections.Study design: Specificity was assessed using 100 blood samples containing no anti-HEV IgM, anti-HEV IgG, or HEV-RNA. Cross reactivity was assessed using samples positive for hepatitis C virus RNA (n=10), Epstein-Barr virus DNA (n=10) and cytomegalovirus DNA (n=10). Serial dilutions of 4 HEV RNA positive samples were used to estimate the corresponding viremia detected with the Ag assay. Blood samples from 33 immunocompetent and 31 immunocompromised patients with an acute HEV genotype 3 infection, HEV-RNA positive, were tested to assess diagnostic sensitivity.Results: The HEV-Ag assay was 100% specific, with no cross-reactivity. The lower viremias detected ranged from 10(3)copies/ml to 10(5)copies/ml (800-80,000UI/ml). Diagnostic sensitivity for an acute HEV infection was 91%, with no significant difference between immunocompetent (88%) and immunocompromised (94%) patients. The HEV-Ag assay was more frequently positive in immunocompromised patients at the acute phase (94%) than was the anti-HEV IgM test (71%; p=0.04). The HEV-Ag assay ratio was correlated with HEV-RNA viral load (ρ=0.54; p<0.0001).Conclusion: The HEV-Ag assay performed well and could be suitable for laboratories with no molecular diagnosic facilities

Evaluation of Three Quantitative Anti-SARS-CoV-2 Antibody Immunoassays

International audienceThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 and caused a dramatic pandemic. Serological assays are used to check for immunization and assess herd immunity. We evaluated commercially available assays designed to quantify antibodies directed to the SARS-CoV-2 Spike (S) antigen, either total (Wantaï SARS-CoV-2 Ab ELISA) or IgG (SARS-CoV-2 IgG II Quant on Alinity, Abbott, and Liaison SARS-CoV-2 TrimericS IgG, Diasorin). The specificities of the Wantaï, Alinity, and Liaison assays were evaluated using 100 prepandemic sera and were 98, 99, and 97%, respectively. The sensitivities of all three were around 100% when tested on 35 samples taken 15 to 35 days postinfection. They were less sensitive for 150 sera from late infections (>180 days). Using the first WHO international standard (NIBSC), we showed that the Wantai results were concordant with the NIBSC values, while Liaison and Alinity showed a proportional bias of 1.3 and 7, respectively. The results of the 3 immunoassays were significantly globally pairwise correlated and for late infection sera (P < 0.001). They were correlated for recent infection sera measured with Alinity and Liaison (P < 0.001). However, the Wantai results of recent infections were not correlated with those from Alinity or Liaison. All the immunoassay results were significantly correlated with the neutralizing antibody titers obtained using a live virus neutralization assay with the B1.160 SARS-CoV-2 strain. These assays will be useful once the protective anti-SARS-CoV-2 antibody titer has been determined