Lina Mouna

Background: Hepatitis A virus (HAV), transmitted primarily through the faecal–oral route, remains endemic in Mayotte, particularly among children. This study aims to assess the HAV epidemiology and circulating strains from 2017 to 2019 to evaluate prevention strategies. Methods: Between November 2017 and June 2019, 2434 patients were tested for HAV immunoglobulin M (IgM). Acute HAV infection was defined by HAV-IgM levels and clinical symptoms. Genotyping was performed using reverse transcription polymerase chain reaction and phylogenetic analysis. Results: Of 125 positive cases, 50 met the acute infection criteria, with a median age of 13 y. Most cases were mild and 28% required hospitalization. Phylogenetic analysis identified genotype IIIA, with a distinct ‘Mahorese strain’ circulating in Mayotte. A few cases were linked to travel to Madagascar and Pakistan. Conclusions: Mayotte remains highly endemic for HAV, with a locally circulating strain. Improved sanitation and hygiene are crucial to control the spread of HAV, and while universal vaccination could help, hygiene measures should remain a priority.

Molecular assays from nasopharyngeal swabs are the current reference method to diagnose COVID-19. As an alternative, we evaluated the performance of the iFlash-2019-nCoV Antigen® (YHLO, Shenzhen, China), developed for SARS-CoV-2 N-antigen detection in serum samples. Specificity, determined on 50 pre-pandemic samples, was 100%. Overall sensitivity, evaluated on 40 sera from patients with RT-PCR confirmed infection, was 67.5%. However, sensitivity reached 73% in symptomatic patients, 80% in patients with high and medium nasopharyngeal (NP) viral loads (samples with Ct≤33) and, 90% in samples collected within the first week after symptoms onset. These sera were further analyzed with the COV-QUANTO® ELISA and COVID-VIRO® LFIA assays (AAZ, Boulogne-Billancourt, France). EIA Ag assays from Yhlo and AAZ had comparable performances, and both were more sensitive than the LFIA. These findings suggest that SARS-CoV-2 N-antigen detection in serum could be an alternative to PCR from NP swabs, at least early after onset of symptoms. Further studies are required to confirm these results.

Vaccination against COVID-19 is the main public health approach to fight against the pandemic. The Spike (S) glycoprotein of SARS-CoV-2 is the principal target of the neutralizing humoral response. We evaluated the analytical and clinical performances of a surrogate virus neutralization test (sVNT) compared to conventional neutralization tests (cVNTs) and anti-S eCLIA assays in recovered and/or vaccinated healthcare workers. Our results indicate that sVNTs displayed high specificity and no cross-reactivity. Both eCLIA and sVNT immunoassays were good at identifying cVNT serum dilutions ≥1:16. The optimal thresholds when identifying cVNT titers ≥1:16, were 74.5 U/mL and 49.4 IU/mL for anti-S eCLIA and sVNT, respectively. Our data show that neutralizing antibody titers (Nab) differ from one individual to another and may diminish over time. Specific assays such as sVNTs could offer a reliable complementary tool to routine anti-S serological assays.

(1) Background: What is the role of serum CMV PCR in the diagnosis of recent primary infection (PI) in pregnant women when IgG avidity is uninformative? (2) Methods: Retrospective cohort study to compare serum versus whole blood CMV PCR. (a) Qualitative assessment: CMV PCR was performed on 123 serum samples and 74 whole blood samples collected from 132 pregnant women with recent CMV PI. PCR positivity rate was used to calculate sensitivity in serum and whole blood. (b) Quantitative assessment: CMV PCR was performed on 72 paired samples of serum and whole blood collected on the same day from 57 patients. (3) Results: In pregnant women, PCR positivity rate was 89% for serum samples versus 100% in whole blood in the case of very recent PI (<15 days), but only 27% in serum versus 68% in whole blood for PI occurring from 6 weeks to 3 months before. Comparing CMV viral loads between serum and whole blood, we determined the limit of CMV DNA detection in serum as 3 log copies/mL (whole blood equivalent). (4) Conclusions: Serum CMV PCR is reliable in confirming PI in cases when only IgM is detected. It is therefore a valuable tool in introducing valaciclovir treatment as early as possible to prevent mother-to-child CMV transmission.

Vaccination against the ongoing COVID-19 is the key point in fight against the pandemic. The Spike (S) glycoprotein of SARS-CoV-2 is the major target of the neutralizing humoral response. We evaluated analytical and clinical performances of a surrogate virus neutralization test (sVNT) (iFlash-2019-nCoV Nab assay, Ylho, China) compared to the conventional neutralization tests (cVNT) and anti-S eCLIA assays (Roche Diagnostics, Switzerland) in recovered and/or vaccinated health care workers. Our results indicate that sVNT displayed high specificity and no cross reactivity. Both Roche and iFlash immunoassays were good in identifying cVNT serum dilution > 1:16. Optimal thresholds in identifying cVNT titers ≥ 1:16, were 74.5 U/ml and 49.4 IU/ml for anti-S eCLIA and sVNT, respectively. Our data show that Nab neutralizing antibodies titers depend on individuals and may abate over time. Specific assays such as sVNT may be a reliable complementary tool to routine anti-S serology assays.

Gaspard Lamy, Christelle Vauloup Fellous, Lina Mouna, Mathilde Dargelos, Eve Vilaine, Aymeric Couturier, Panha Chhom, Marie Essig, Ziad A Massy; Heterogeneous n