M.T. Arias

High prevalence of genetically-determined mannose binding lectin deficiency in young children with invasive pneumococcal disease

Susceptibility to invasive pneumococcal disease (IPD) correlates with age, younger children being the group with the highest burden of disease. The relevance of the innate immune response and particularly the role of mannose-binding lectin (MBL) in combating IPD is not well known. This is a 2-year prospective study (February 2011 to March 2013) including patients with IPD who attended two hospitals from Catalonia, Spain. Variables including attack rate of pneumococcal serotype (high or low invasive potential serotypes) and genotypes associated with low serum MBL levels were recorded. One hundred and forty-seven patients were included in the study. One hundred and two (69.4%) patients were children or adolescents <18 years and 45 (30.6%) were adults. Overall, low-MBL genotypes (O/O; XA/O) were detected in 23 (15.6%) patients. Children <2 years showed a higher frequency of low-MBL genotypes compared with other patients (31.0% vs. 11.9%; p = 0.031). Further sub-analysis revealed a higher proportion of low-MBL genotypes in children <2 years with IPD caused by opportunistic or low-attack-rate serotypes when compared with older patients (46.2% vs. 13.2%; p = 0.02). However, no statistically significant differences between the two groups were observed when including patients infected with invasive or high-attack-rate serotypes (18.8% vs. 10.0%; p = 0.59). Our data suggest that young children with a genetically determined low-MBL production are at a higher risk of developing IPD, particularly that caused by opportunistic or low-attack-rate pneumococcal serotypes.

Analysis of ancestral and functionally relevant CD5 variants in systemic lupus erythematosus patients.

Objective CD5 plays a crucial role in autoimmunity and is a well-established genetic risk factor of developing RA. Recently, evidence of positive selection has been provided for the CD5 Pro224-Val471 haplotype in East Asian populations. The aim of the present work was to further analyze the functional relevance of non-synonymous CD5 polymorphisms conforming the ancestral and the newly derived haplotypes (Pro224-Ala471 and Pro224-Val471, respectively) as well as to investigate the potential role of CD5 on the development of SLE and/or SLE nephritis. Methods The CD5 SNPs rs2241002 (C/T; Pro224Leu) and rs2229177 (C/T; Ala471Val) were genotyped using TaqMan allelic discrimination assays in a total of 1,324 controls and 681 SLE patients of Spanish origin. In vitro analysis of CD3-mediated T cell proliferative and cytokine response profiles of healthy volunteers homozygous for the above mentioned CD5 haplotypes were also analyzed. Results T-cell proliferation and cytokine release were significantly increased showing a bias towards to a Th2 profile after CD3 cross-linking of peripheral mononuclear cells from healthy individuals homozygous for the ancestral Pro224-Ala471 (CC) haplotype, compared to the more recently derived Pro224-Val471 (CT). The same allelic combination was statistically associated with Lupus nephritis. Conclusion The ancestral Ala471 CD5 allele confers lymphocyte hyper-responsiveness to TCR/CD3 cross-linking and is associated with nephritis in SLE patients.

Etiopathogenic Role of Surfactant Protein D in the Clinical and Immunological Expression of Primary Sjögren Syndrome

Objective. To analyze the etiopathogenic role of genetic polymorphisms and serum levels of surfactant protein-D (SP-D) in primary Sjögren syndrome (pSS). Methods. We analyzed 210 consecutive patients with pSS. SFTPD genotyping (M11T polymorphism rs721917) was analyzed by sequence-based typing and serum SP-D by ELISA. Results. Thirty-two patients (15%) had the Thr11/Thr11 genotype, 80 (38%) the Met11/Met11 genotype, and 96 (46%) the Met11/Thr11 genotype; 2 patients could not be genotyped. Patients carrying the Thr11/Thr11 genotype had a higher prevalence of renal involvement (13% vs 1% and 4% in comparison with patients carrying the other genotypes, p = 0.014). Serum SP-D levels were analyzed in 119 patients (mean 733.94 ± 49.88 ng/ml). No significant association was found between serum SP-D levels and the SP-D genotypes. Higher mean values of serum SP-D were observed in patients with severe scintigraphic involvement (851.10 ± 685.69 vs 636.07 ± 315.93 ng/ml, p = 0.038), interstitial pulmonary disease (1053.60 ± 852.03 vs 700.36 ± 479.33 ng/ml, p = 0.029), renal involvement (1880.64 ± 1842.79 vs 716.42 ± 488.01 ng/ml, p = 0.002), leukopenia (899.83 ± 661.71 vs 673.13 ± 465.88 ng/ml, p = 0.038), positive anti-Ro/SS-A (927.26 ± 731.29 vs 642.75 ± 377.23 ng/ml, p = 0.006), and positive anti-La/SS-B (933.28 ± 689.63 vs 650.41 ± 428.14 ng/ml, p = 0.007), while lower mean values of serum SP-D were observed in patients with bronchiectasis (489.49 vs 788.81 ng/ml, p = 0.019). Conclusion. In pSS, high SP-D levels were found in patients with severe glandular involvement, hypergammaglobulinemia, leukopenia, extraglandular manifestations, and positive anti-Ro/La antibodies. The specific association between SP-D levels and pulmonary and renal involvements may have pathophysiological implications.

Mannose-Binding Lectin–Deficient Donors Increase the Risk of Bacterial Infection and Bacterial Infection–Related Mortality After Liver Transplantation

Mannose‐binding lectin (MBL) is synthesized by the liver and binds to microbes. MBL2 gene polymorphisms produce intermediate/low/null or normal MBL serum levels (MBL‐deficient or MBL‐sufficient phenotypes, respectively). We aimed to evaluate the incidence and severity of infection, rejection, and survival within 1 year after liver transplantation (LT) according to donor and recipient MBL2 gene polymorphisms. A repeated‐event analysis for infection episodes (negative binomial regression, Andersen–Gill model) was performed in 240 LTs. Four hundred twenty‐eight infectious episodes (310 bacterial, 15 fungal, 65 cytomegalovirus [CMV]‐related, and 38 viral non–CMV‐related episodes) and 48 rejection episodes were recorded. The main bacterial infections were urinary (n = 82, 26%) and pneumonia (n = 69, 22%). LT recipients of MBL‐deficient livers had a higher risk of bacterial infection (incidence rate ratio [IRR] 1.48 [95% confidence interval 1.04–2.09], p = 0.028), pneumonia (IRR 2.4 [95% confidence interval 1.33–4.33], p = 0.013), and septic shock (IRR 5.62 [95% confidence interval 1.92–16.4], p = 0.002) compared with recipients of MBL‐deficient livers. The 1‐year bacterial infection–related mortality was higher in recipients of MBL‐deficient versus MBL‐sufficient livers (65.8% vs. 56.1%, respectively; p = 0.0097). The incidence of rejection, viral, or fungal infection was similar in both groups. Recipient MBL2 genotype did not significantly increase the risk of bacterial infection. LT recipients of MBL‐deficient livers have a higher risk of bacterial infection, pneumonia, septic shock, and 1‐year bacterial infection–related mortality after LT.

Mannose Binding Lectin (mbl2) Genotype Frequencies in Solid Organ Transplant Patients

Background Mannose-binding lectin (MBL) is a protein critical in the activation of the lectin complement pathway. Patients with wild-type and variant mbl2 genotypes have high or low concentrations of MBL protein, which have been associated to increase susceptibility to transplant rejection or infection, respectively. Objective Our objective was to determine mbl2 genotype frequencies in a cohort of solid organ transplant recipients and its relationship with clinical outcomes. Materials and Methods A retrospective observational study in a single center. DNA samples were obtained at the time of inclusion in the waiting list for solid organ trasplantation as part of an extended immunological analysis to assess the pre-transplant immunocompetence status of the patients (109 heart transplantation, 3 liver transplantation). DNA was extracted from 1.5-mL ethylene diamine tetraacetic acid–treated whole blood samples. Genotyping of MBL2 was done by a polymerase chain reaction (PCR)/sequence-based typing technique. MBL2 encompassing a region from the promoter to the end of exon 1 was obtained by PCR amplification. Results Frequencies of the MBL genotype in our patients were similar to those of other Spanish populations used as a reference: Low-expressing genotype 16 (14%), intermediate 30 (27%), high 66 (59%). We have confirmed a correlation of genotype and phenotype as patients with the intermediate and deficient mbl2 genotypes disclosed significantly lower concentrations of MBL protein. Patients with low-intermediate expressing genotypes had a higher prevalence of viral infections (p=0.004). Results Conclusion: Low-intermediate expressing genotype is a frequently expressed profile in the population that may predispose solid organ recipients to a greater susceptibility of viral infections. Under immunosuppressive clinical settings these genetic host factors might be associated with distinct clinical outcomes. The potential role of this genetic biomarker warrants further evaluation in prospective multicenter studies. Fondo de Investigación Sanitaria. Project FIS 1501472. With participation of FEDER funds. A way of making Europe.

Mannose-binding lectin-deficient genotypes as a risk factor of pneumococcal meningitis in infants

Objectives The objective of this study was to evaluate to evaluate the role of mannose-binding-lectin deficient genotypes in pneumococcal meningitis (PM) in children. Methods We performed a 16-year retrospective study (January 2001 to March 2016) including patients ≤ 18 years with PM. Variables including attack rate of pneumococcal serotype (high or low invasive capacity) and MBL2 genotypes associated with low serum MBL levels were recorded. Results Forty-eight patients were included in the study. Median age was 18.5 months and 17/48 episodes (35.4%) occurred in children ≤ 12 months old. Serotypes with high-invasive disease potential were identified in 15/48 episodes (31.2%). MBL2 deficient genotypes accounted for 18.8% (9/48). Children ≤ 12 months old had a 7-fold risk (95% CI: 1.6–29.9; p < 0.01) of having a MBL2 deficient genotype in comparison to those > 12 months old. A sub-analysis of patients by age group revealed significant proportions of carriers of MBL2 deficient genotypes among those ≤ 12 months old with PM caused by opportunistic serotypes (54.5%), admitted to the PICU (Pediatric Intensive Care Unit) (46.7%) and of White ethnicity (35.7%). These proportions were significantly higher than in older children (all p<0.05). Conclusions Our results suggest that differences in MBL2 genotype in children ≤12 months old affects susceptibility to PM, and it may have an important role in the episodes caused by non-high invasive disease potential serotypes.

Functional relevance of a non-synonymous substitution in the CD5 gene (V471A) targeted for positive selection in East Asian populations

CD5 is a transmembrane receptor expressed on T and B1a lymphocytes where it is known to modulate lymphocyte activation and/or differentiation processes. Recent evidence show that CD5 also works as pathogen recognition receptor for conserved fungal cell wall components (β-glucans). When analyzing SNP data in a worldwide sample of 39 human populations (HGDP diversity panel) different signatures of positive selection were detected in a 150 kb genomic region where the CD5 gene maps. The Val471 to Ala substitution (rs2229177) in the cytoplasmatic region of CD5 was suggested to be the most plausible target of selection as it was the only known nonsynonymous variant linked to the putatively selected haplotype. In silico analyses predict a possible deleterious function of Val to Ala replacement and one recent study reported better clinical prognosis for Valine in patients with chronic lymphocytic leukaemia (CLL). Resequencing analysis of the CD5 gene in 60 individuals representing three main populations (20 Africans, 20 Europeans and 20 Asians) has been performed in this study with the specific aims of fully describing its genetic variability and of confirming previous evidences of selection. The results obtained show a clear signal of positive selection at the CD5 locus in East Asians when applying classical tests of neutrality such as Tajima´s D, Fu and Li’s F and D, or Fu and Wu’s H and suggest that no other coding variations in this locus could be the actual target of selection. Interestingly, MAPK kinase assays performed on COS-7 cell transfectants and human peripheral blood lymphocytes subjected to different stimuli (anti-CD5 mAb crosslinking, Zymosan) demonstrated quantitative and qualitative functional differences between the two allelic CD5 variants. Taken together, the results strongly favor the hypothesis of a possible adaptive role of the V471A substitution in East Asian populations.

Using a Computer to Identify Nematodes

In the study of virus vector nematodes of the family Longidoridae in Spain during the last six years, we have used the polytomous key by Romanenko modified by Hooper for the identification of Longidorus spp. It was proposed to use a computer program to conveniently manage the great quantity of data involved. Such a program was recently published for Longidorus (Rey et al., 1988), and for Tylenchorhynchus and Merlinius (Rey & Mahajan, in press).