SARS-CoV-2 N-Antigen Quantification in Respiratory Tract, Plasma and Urine: Kinetics and Association with RT-qPCR Results.

Qualitative SARS-CoV-2 antigen assays based on immunochromatography are useful for mass diagnosis of COVID-19, even though their sensitivity is poor in comparison with RT-PCR assays. In addition, quantitative assays could improve antigenic test performance and allow testing with different specimens. Using quantitative assays, we tested 26 patients for viral RNA and N-antigen in respiratory samples, plasma and urine. This allowed us to compare the kinetics between the three compartments and to compare RNA and antigen concentrations in each. Our results showed the presence of N-antigen in respiratory (15/15, 100%), plasma (26/59, 44%) and urine (14/54, 28.9%) samples, whereas RNA was only detected in respiratory (15/15, 100%) and plasma (12/60, 20%) samples. We detected N-antigen in urine and plasma samples until the day 9 and day 13 post-inclusion, respectively. The antigen concentration was found to correlate with RNA levels in respiratory (p < 0.001) and plasma samples (p < 0.001). Finally, urinary antigen levels correlated with plasma levels (p < 0.001). Urine N-antigen detection could be part of the strategy for the late diagnosis and prognostic evaluation of COVID-19, given the ease and painlessness of sampling and the duration of antigen excretion in this biological compartment.

Diagnostic Performance of an Automated System for Assaying Anti-Hepatitis E Virus Immunoglobulins M and G Compared with a Conventional Microplate Assay.

To evaluate the diagnostic performance of the Liaison® Murex anti-HEV IgM and IgG assays running on the Liaison® instrument and compare the results with those obtained with Wantai HEV assays. We tested samples collected in immunocompetent and immunocompromised patients during the acute (HEV RNA positive, anti-HEV IgM positive) and the post-viremic phase (HEV RNA negative, anti-HEV IgM positive) of infections. The specificity was assessed by testing HEV RNA negative/anti-HEV IgG-IgM negative samples. The clinical sensitivity of the Liaison® IgM assay was 100% for acute-phase samples (56/56) and 57.4% (27/47) for post-viremic samples from immunocompetent patients. It was 93.8% (30/32) for acute-phase (viremic) samples and 71%% (22/31) for post-viremic samples from immunocompromised patients. The clinical sensitivity of the Liaison® IgG assay was 100% for viremic samples (56/56) and 94.6% (43/47) for post-viremic samples from immunocompetent patients. It was 84.3% (27/32) for viremic samples and 93.5% (29/31) for post-viremic samples from immunocompromised patients. Specificity was very high (>99%) in both populations. We checked the limit of detection stated for the Liaison® IgG assay (0.3 U/mL). The clinical performance of the Liaison® ANTI-HEV assays was good. These rapid, automated assays for detecting anti-HEV antibodies will greatly enhance the arsenal for diagnosing HEV infections.

Rat Hepatitis E Virus: Presence in Humans in South-Western France?

Background: Hepatitis E Virus (HEV) is one of the most common causes of hepatitis worldwide, and South-Western France is a high HEV seroprevalence area. While most cases of HEV infection are associated with the species Orthohepevirus-A, several studies have reported a few cases of HEV infections due to Orthohepevirus-C (HEV-C) that usually infects rats. Most of these human cases have occurred in immunocompromised patients. We have screened for the presence of HEV-C in our region. Methods and Results: We tested 224 sera, mostly from immunocompromised patients, for HEV-C RNA using an in-house real time RT-PCR. Liver function tests gave elevated results in 63% of patients: mean ALT was 159 IU/L (normal < 40 IU/L). Anti-HEV IgG (49%) and anti-HEV IgM (9.4%) were frequently present but none of the samples tested positive for HEV-C RNA. Conclusion: HEV-C does not circulate in the human population of South-Western France, despite the high seroprevalence of anti-HEV IgG.