Low MBL-associated serine protease 2 (MASP-2) levels correlate with urogenital schistosomiasis in Nigerian children

OBJECTIVES

The human mannose-binding lectin (MBL) and ficolins (FCN) are involved in pathogen recognition in the first line of defence. They support activation of the complement lectin cascade in the presence of MBL-associated serine protease 2 (MASP-2), a protein that cleaves the C4 and C2 complement components. Recent studies found that distinct MBL2 and FCN2 promoter variants and their corresponding serum levels are associated with relative protection from urogenital schistosomiasis.

METHODS

We investigated the contribution of MASP-2 levels and MASP2 polymorphisms in a Nigerian study group, of 163 individuals infected with Schistosoma haematobium and 183 healthy subjects.

RESULTS

MASP-2 serum levels varied between younger children (≤12 years) and older children (>12 years) and adults (P = 0.0001). Younger children with a patent infection had significantly lower MASP-2 serum levels than uninfected children (P = 0.0074). Older children and adults (>12 years) with a current infection had higher serum MASP-2 levels than controls (P = 0.032). MBL serum levels correlated positively with MASP-2 serum levels (P = 0.01). MASP2 secretor haplotypes were associated with MASP-2 serum levels in healthy subjects. The heterozygous MASP2 p.P126L variant was associated with reduced serum MASP-2 levels (P = 0.01).

CONCLUSIONS

The findings indicate that higher MASP-2 serum levels are associated with relative protection from urogenital schistosomiasis in Nigerian children.

Mannose-binding lectin and susceptibility to schistosomiasis

BACKGROUND

Human ficolin 2 (encoded by FCN2) and mannose-binding lectin (encoded by MBL2) bind to specific pathogen-associated molecular patterns, activate the complement lectin cascade in a similar manner, and are associated with several infectious diseases. Our recently published study established certain FCN2 promoter variants and ficolin-2 serum levels as protective factors against schistosomiasis.

METHODS

We used the Nigerian cohort from our recently published study, which included 163 Schistosoma haematobium-infected individuals and 183 matched healthy subjects, and investigated whether MBL deficiency and MBL2 polymorphisms are associated with schistosomiasis.

RESULTS

MBL serum levels were significantly higher in controls and were associated with protection (P < .0001). The -550H minor allele was significantly associated with protection (P = .03), and the heterozygous genotypes -550HL were observed to confer protection (P = .03). The MBL2*HYPA haplotype was significantly associated with protection (P = .03), with significantly higher serum MBL levels in controls (P = .00073). The heterozygous 6-bp deletion in the promoter was observed to be a susceptibility factor in schistosomiasis (P = .03).

CONCLUSIONS

In agreement with findings from our recently published study, the findings reported here support the observation that MBL is also associated with protection in schistosomiasis.

Ficolin-2 levels and FCN2 genetic polymorphisms as a susceptibility factor in schistosomiasis

BACKGROUND

Human ficolin-2 (L-ficolins) encoded by the FCN2 gene are pattern-recognition proteins involved in innate immunity and are associated with several infectious diseases.

METHODS

A Nigerian cohort of 168 Schistosoma haematobium-infected individuals and 192 healthy controls were examined for functional single-nucleotide polymorphisms in the promoter region (-986G>A, -602G>A, -4A>G) and in exon 8 (+6424G>T) using real-time polymerase chain reaction.

RESULTS

The FCN2 -986A and -4G alleles were significantly associated with the occurrence of schistosomiasis (P = .0004 for -986G>A; P = .0001 for -4A>G). The heterozygous genotypes (P = .0006 for -986G>A; P = .0002 for -4A>G) were observed to be a risk factor for susceptibility to schistosomiasis, whereas the homozygous genotypes of major alleles (P = .0002 for -986G>A; P = .0001 for -4A>G) were observed to shield against schistosomiasis. The haplotype AGGG (P = .0002) was observed to be a risk factor for susceptibility to schistosomiasis compared with controls, and the haplotype GGAG (P = .04) was observed to confer protection compared with patients. Ficolin-2 serum level was significantly higher in controls (P < .005) and in controls with GGAG haplotypes (P < .0001).

CONCLUSIONS

Our findings demonstrate that FCN2 promoter variants (-986G>A and -4A>G) influence ficolin-2 serum levels and susceptibility to schistosomiasis.