Association between mannose binding lectin gene polymorphisms and clinical severity of COVID-19 in children

Impact of Exon 1 polymorphism in the MBL2 gene on MBL serum levels and infection susceptibility in acute lymphoid leukemia

Polymorphisms in the MBL2 gene exon 1 can decrease serum levels of mannose-binding lectin (MBL), increasing the risk of infection in immunocompromised individuals. This study evaluated the association between the polymorphism in exon 1 of the MBL2 gene, genotypes, serum MBL levels, and infection in 122 patients with acute lymphoid leukemia (ALL). The MBL*A allele exhibited the highest frequency (0.37) within the study population. The MBL*D (0.32) was the predominant variant. The combined frequency of O polymorphic alleles (either B or D) was 0.63. The frequencies of the A/A, A/O and O/O genotypes were 0.13, 0.49 and 0.38, respectively. All patients exhibited consistently low levels of serum MBL, irrespective of their exon 1 genotype. Parasitic infections (n = 103), bacterial (n = 69) and viral (n = 48). A/O genotype (0.49) had higher infection rates, A/A (0.13) had lower rates, and O/O showed increased viral susceptibility (OR: 0.37; 95% CI 0.13-1.06; p = 0.05). Our findings demonstrated that the study population were MBL-deficient, regardless of their MLB2 genotype. Individuals with the A/O genotype had more infections, while those with the O/O genotype appeared more susceptible to viral infections. These findings highlight the impact of MBL levels and genetic variants on infection susceptibility in ALL patients.

Genomic Landscape of Susceptibility to Severe COVID-19 in the Slovenian Population

Determining the genetic contribution of susceptibility to severe SARS-CoV-2 infection outcomes is important for public health measures and individualized treatment. Through intense research on this topic, several hundred genes have been implicated as possibly contributing to the severe infection phenotype(s); however, the findings are complex and appear to be population-dependent. We aimed to determine the contribution of human rare genetic variants associated with a severe outcome of SARS-CoV-2 infections and their burden in the Slovenian population. A panel of 517 genes associated with severe SARS-CoV-2 infection were obtained by combining an extensive review of the literature, target genes identified by the COVID-19 Host Genetic Initiative, and the curated Research COVID-19 associated genes from PanelApp, England Genomics. Whole genome sequencing was performed using PCR-free WGS on DNA from 60 patients hospitalized due to severe COVID-19 disease, and the identified rare genomic variants were analyzed and classified according to the ACMG criteria. Background prevalence in the general Slovenian population was determined by comparison with sequencing data from 8025 individuals included in the Slovenian genomic database (SGDB). Results show that several rare pathogenic/likely pathogenic genomic variants in genes CFTR, MASP2, MEFV, TNFRSF13B, and RNASEL likely contribute to the severe infection outcomes in our patient cohort. These results represent an insight into the Slovenian genomic diversity associated with a severe COVID-19 outcome.

High production MBL2 polymorphisms protect against COVID-19 complications in critically ill patients: A retrospective cohort study

Mannose-binding lectin (MBL) binds to SARS-CoV-2, inhibits infection of susceptible cells, and activates the complement system via the lectin pathway. In this study, we investigated the association of MBL2 polymorphisms with the risk of hospitalization and clinical worsening in patients with COVID-19. A total of 550 patients with COVID-19 were included (94 non-hospitalized and 456 hospitalized). Polymorphisms in MBL2 exon 1 (codons 52, 54 and 57) and promoter region (-550, -221, and +4) were determined by real-time PCR. MBL and complement proteins were measured by Luminex. A higher frequency of the H/H genotype and the HYPA haplotype was observed in non-hospitalized patients when compared to hospitalized. In addition, critically ill patients carrying haplotypes associated with high MBL levels (HYPA/HYPA + HYPA/LYPA + HYPA/LYQA + LYPA/LYQA + LYPA/LYPA + LYQA/LYQA + LXPA/HYPA + LXPA/LYQA + LXPA/LYPA) were protected against lower oxygen saturation levels (P = 0.02), use of invasive ventilation use (P = 0.02, OR 0.38), and shock (P = 0.01, OR 0.40), independent of other potential confounders adjusted by multivariate analysis. Our results suggest that variants in MBL2 associated with high MBL levels may play a protective role in the clinical course of COVID-19.

The MBL2 genotype relates to COVID-19 severity and may help to select the optimal therapy

OBJECTIVES

Sars-CoV-2 acute infection is clinically heterogeneous, ranging from asymptomatic cases to patients with a severe, systemic clinical course. Among the involved factors age and preexisting morbidities play a major role; genetic host susceptibility contributes to modulating the clinical expression and outcome of the disease. Mannose-binding lectin is an acute-phase protein that activates the lectin-complement pathway, promotes opsonophagocytosis and modulates inflammation, and is involved in several bacterial and viral infections in humans. Understanding its role in Sars-CoV-2 infection could help select a better therapy.

METHODS

We studied MBL2 haplotypes in 419 patients with acute COVID-19 in comparison to the general population and related the haplotypes to clinical and laboratory markers of severity.

RESULTS

We recorded an enhanced frequency of MBL2 null alleles in patients with severe acute COVID-19. The homozygous null genotypes were significantly more frequent in patients with advanced WHO score 4-7 (OR of about 4) and related to more severe inflammation, neutrophilia, and lymphopenia.

CONCLUSIONS

Subjects with a defective MBL2 genotype (i.e., 0/0) are predisposed to a more severe acute Sars-CoV-2 infection; they may benefit from early replacement therapy with recombinant MBL. Furthermore, a subset of subjects with the A/A MBL genotype develop a relevant increase of serum MBL during the early phases of the disease and develop a more severe pulmonary disease; in these patients, the targeting of the complement may help. Therefore, COVID-19 patients should be tested at hospitalization with serum MBL analysis and MBL2 genotype, to define the optimal therapy.