Centromeric AA motif in KIR as an optimal surrogate marker for precision definition of alloimmune reproductive failure

Throughout pregnancy, the decidua is predominantly populated by NK lymphocytes expressing Killer immunoglobulin-like receptors (KIR) that recognize human leukocyte antigen-C (HLA-C) ligands from trophoblast cells. This study aims to investigate the association of KIR-HLA-C phenotypes in couples facing infertility, particularly recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF), in comparison to a reference population and fertile controls. This observational, non-interventional retrospective case-control study included patients consecutively referred to our Reproductive Immunology Unit from 2015 to 2019. We analyzed the frequencies of KIR and HLA-C genes. As control groups, we analyzed a reference Spanish population for KIR analysis and 29 fertile controls and their male partners for KIR and HLA-C combinations. We studied 397 consecutively referred women with infertility and their male partners. Among women with unexplained RPL (133 women) and RIF (176 women), the centromeric (cen)AA KIR genotype was significantly more prevalent compared to the reference Spanish population (p = 0.001 and 0.02, respectively). Furthermore, cenAA was associated with a 1.51-fold risk of RPL and a 1.2-fold risk of RIF. Conversely, the presence of BB KIR showed a lower risk of reproductive failure compared to non-BB KIR (OR: 0.12, p < 0.001). Women and their partners with HLA-C1C1/C1C1 were significantly less common in the RPL-Group (p < 0.001) and RIF-Group (p = 0.002) compared to the control group. Moreover, the combination of cenAA/C1C1 in women with C1C1 partners was significantly higher in the control group than in the RPL (p = 0.009) and RIF (p = 0.04) groups, associated with a 5-fold increase in successful pregnancy outcomes. In our cohort, the cenAA KIR haplotype proved to be a more accurate biomarker than the classic AA KIR haplotype for assessing the risk of RPL and RIF, and might be particularly useful to identify women at increased risk among the heterogeneous KIR AB or Bx population. The classification of centromeric KIR haplotypes outperforms classical KIR haplotypes, making it a better indicator of potential maternal-fetal KIR-HLA-C mismatch in patients.

Dysimmunity in common variable immunodeficiency is associated with alterations in oral, respiratory, and intestinal microbiota

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency characterized by decreased immunoglobulins and recurrent infections. Its aetiology remains unknown, and some patients present with severe non-infectious autoimmune or inflammatory complications with elevated associated morbimortality. Recently, intestinal dysbiosis has been proposed as a driver of immune dysregulation. In this study, we assessed the oral, respiratory, and gastrointestinal microbiota of 41 CVID patients (24 with dysimmune and 17 with infection complications) and 15 healthy volunteers using 16S rRNA gene sequencing to explore associations between microbiome profiles and CVID phenotypes. Profound differences in the composition of the microbiota in saliva, sputum, and stool were detected between dysimmune CVID patients and healthy individuals. Globally, respiratory species diversity and faecal bacterial richness were lower in CVID individuals with immune complications. Although a single species could not be identified as a robust predictor of dysimmunity, a combination of around 5-7 bacterial species in each type of sample could predict this severe phenotype with an accuracy of around 90% in the study population. Our study provides new insights into these previously unexplored but highly interrelated ecological niches among themselves and with patient profiles. Our data suggest that this disease-related systemic dysbiosis could be implicated in the immune dysregulation associated with severe cases of CVID.

Norovirus infection as a model of chronic or recurrent infection in common variable immunodeficiency

Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immunodeficiency (PID) in general population. PID are genetic diseases that share a dysfunction in the immune system entailing a greater risk of both chronic and recurrent infections. These patients can also develop chronic gastrointestinal infections caused by norovirus with persistent viral dissemination, which can be detected months after primoinfection. Additionally, a proportion of CVID patients show a typical severe enteropathy presenting with recurrent diarrhoea, intestinal malabsorption, inflammatory lesions, and villous atrophy. Some studies have related this enteropathy with chronic intestinal infection caused by norovirus.