Fondation Jean Dausset-CEPH

Microsatellites are short tandem repeats (STRs) of a motif of 1-6 nucleotides that are ubiquitous in almost all genomes and widely used in many biomedical applications. However, despite the development of next-generation sequencing (NGS) over the past two decades with new technologies coming to the market, accurately sequencing and genotyping STRs, particularly homopolymers, remain very challenging today due to several technical limitations. This leads in many cases to erroneous allele calls and difficulty in correctly identifying the genuine allele distribution in a sample. Here, we assessed several second and third-generation sequencing approaches in their capability to correctly determine the length of microsatellites using plasmids containing A/T homopolymers, AC/TG or AT/TA dinucleotide STRs of variable length. Standard polymerase chain reaction (PCR)-free and PCR-containing, single Unique Molecular Indentifier (UMI) and dual UMI 'duplex sequencing' protocols were evaluated using Illumina short-read sequencing, and two PCR-free protocols using PacBio and Oxford Nanopore Technologies long-read sequencing. Several bioinformatics algorithms were developed to correctly identify microsatellite alleles from sequencing data, including four and two modes for generating standard and combined consensus alleles, respectively. We provided a detailed analysis and comparison of these approaches and made several recommendations for the accurate determination of microsatellite allele length.

Plasma circulating cell-free nucleic acids (ccfNAs) provide an exceptional source of information about an individual's health, yet their biology in healthy individuals during aging remains poorly understood. Here, we present the first integrative multiparametric analysis of the major types of plasma ccfNAs, including nuclear (ccfnDNA) and mitochondrial (ccfmtDNA) DNA, as well as ribosomal (ccfrRNA), messenger (ccfmRNA) and micro-RNA (ccfmiRNA) in 139 healthy donors aged 19-66 years. We focused on quantity, integrity, and DNA methylation using an optimized experimental workflow that combines highly sensitive analytical methods with the detection of highly repetitive DNA and highly abundant RNA sequences, thereby reducing the required amount of ccfNAs per analysis. We showed a highly significant increase in ccfnDNA levels during aging (p < 0.001), associated with a decrease in its integrity (p < 0.05), while no significant changes were detected in ccfmtDNA levels and ccfDNA methylation. Moreover, a significant increase in ccfmRNA and ccfrRNA (p < 0.05), as well as miR-483-5p (p < 0.001) levels was detected during aging, but without any changes in ccfRNA integrity. Finally, we also showed that ccfDNA and ccfRNA levels were correlated (p < 0.001), and a similar pattern was observed for ccfmtDNA and ccfRNA levels, suggesting a possible common release, maintenance, and/or clearance mechanism. Therefore, our study provides an optimized workflow for the global analysis of ccfNAs, enhances the understanding of their biology during aging, and identifies several potential ccfNA-based biomarkers of aging.

In our recent research on AIDS Elite controllers, we demonstrated that the HLA-B*57:01 allele is part of an extensive MHC haplotype associated with impaired MICA/MICB function. Considering the pivotal role of natural killer (NK) cells and innate immunity in fighting cancer and infectious diseases, we investigated whether this allele could also influence human longevity. To this end, we performed a multinational European study including 2,597 centenarians and 9,973 controls. We found that HLA-B*57:01 was consistently less frequent in the European centenarian cohorts compared with the corresponding controls (OR ≈ 0.68, p &;lt 0.0005). These findings provide the first in vivo genetic evidence that innate immunity and NK cell function are key components of human longevity.

Data on the SARS-CoV-2 infection among primary health care workers (PHCWs) are scarce but essential to reflect on policy regarding prevention and control measures. We assessed the prevalence of PHCWs who have been infected by SARS-CoV-2 in comparison with modeling from the general population in metropolitan France, and associated factors. A cross-sectional study was conducted among general practitioners (GPs), pediatricians, dental and pharmacy workers in primary care between May and August 2021. Participants volunteered to provide a dried-blood spot for SARS-CoV-2 antibody assessment and completed a questionnaire. The primary outcome was defined as the detection of infection-induced antibodies (anti-nucleocapsid IgG, and for non-vaccinees: anti-Spike IgG and neutralizing antibodies) or previous self-reported infection (positive RT-qPCR or antigenic test, or positive ELISA test before vaccination). Estimates were adjusted using weights for representativeness and compared with prediction from the general population. Poisson regressions were used to quantify associated factors. The analysis included 1612 PHCWs. Weighted prevalences were: 31.7% (95% CI 27.5–36.0) for GPs, 28.7% (95% CI 24.4–33.0) for pediatricians, 25.2% (95% CI 20.6–31.0) for dentists, and 25.5% (95% CI 18.2–34.0) for pharmacists. Estimates were compatible with model predictions for the general population. PHCWs more likely to be infected were: GPs compared to pharmacist assistants (adjusted prevalence ratio [aPR] = 2.26; CI 95% 1.01–5.07), those living in Île-de-France (aPR = 1.53; CI 95% 1.14–2.05), South-East (aPR = 1.57; CI 95% 1.19–2.08), North-East (aPR = 1.81; CI 95% 1.38–2.37), and those having an unprotected contact with a COVID-19 case within the household (aPR = 1.48; CI 95% 1.22–1.80). Occupational factors were not associated with infection. In conclusion, the risk of SARS-CoV-2 exposure for PHCWs was more likely to have occurred in the community rather than at their workplace.