[Neonatal screening of severe combined immunodeficiencies]. / Projet de mise en place du dépistage néonatal systématique des déficits immunitaires combinés sévères : présentation de l'étude DEPISTREC.

Severe combined immunodeficiencies (SCID) are a group of inherited diseases of the immune system characterized by profound abnormalities of T-cell development. Infants with SCID require prompt clinical intervention to prevent life-threatening infection and studies show significantly improved survival in babies diagnosed at birth based on previous family history. SCID follows the criteria for population-based newborn screening because it is asymptomatic at birth and fatal within the 1st year of life if there is no intervention, the confirmation of the disease is easy, there is a curative treatment, and it is known that early hematopoietic stem cell transplantation significantly improves survival, the quality of immune reconstitution, and quality of life. Quantification of T-cell receptor excision circles (TRECs) in DNA extracted from Guthrie samples is a sensitive and specific screening test for SCID. We conducted a nationwide prospective study of neonatal screening of SCID in a population of 200,000 French newborns over a period of 2 years. The objective was to study the clinical utility and the cost-effectiveness ratio, and to demonstrate that universal SCID screening could result in a substantial benefit to detect individuals, making screening relatively cost-effective in spite of the low incidence of the disease.

Targeting of a CD8 T cell env epitope presented by HLA-B*5802 is associated with markers of HIV disease progression and lack of selection pressure.

In HIV-infected persons, certain HLA class I alleles are associated with effective control of viremia, while others are associated with rapid disease progression. Among the most divergent clinical outcomes are the relatively good prognosis in HLA-B*5801 expressing persons and poor prognosis with HLA-B*5802. These two alleles differ by only three amino acids in regions involved in HLA-peptide recognition. This study evaluated a cohort of over 1000 persons with chronic HIV clade C virus infection to determine whether clinical outcome differences associated with B*5801 (n = 93) and B*5802 ( n = 259) expression are associated with differences in HIV-1-specific CD8 (+) T cell responses. The overall breadth and magnitude of HIV-1-specific CD8(+) T cell responses were lower in persons expressing B*5802, and epitope presentation by B*5802 contributed significantly less to the overall response as compared to B*5801-restricted CD8 (+) T cells. Moreover, viral load in B*5802-positive persons was higher and CD4 cell counts lower when this allele contributed to the overall CD8 (+) T cell response, which was detected exclusively through a single epitope in Env. In addition, persons heterozygous for B*5802 compared to persons homozygous for other HLA-B alleles had significantly higher viral loads. Viral sequencing revealed strong selection pressure mediated through B*5801-restricted responses but not through B*5802. These data indicate that minor differences in HLA sequence can have a major impact on epitope recognition, and that selective targeting of Env through HLA-B*5802 is at least ineffectual if not actively adverse in the containment of viremia. These results provide experimental evidence that not all epitope-specific responses contribute to immune containment, a better understanding of which is essential to shed light on mechanisms involved in HIV disease progression.