Restricted polymorphisms of the mannose-binding lectin gene in a population of Papua New Guinea

MBL-2 polymorphisms (codon 54 and Y-221X) and low MBL levels are associated with susceptibility to multi organ dysfunction in P. falciparum malaria in Odisha, India

Background: Mannose binding lectin, a plasma protein protects host from virus, bacteria, and parasites. Deficiency in MBL levels has been associated with susceptibility to various infectious diseases including P. falciparum malaria. Common MBL polymorphisms in promoter and coding regions are associated with decrease in plasma MBL levels or production of deformed MBL, respectively. In the present study, we hypothesized that MBL2 variants and plasma MBL levels could be associated with different clinical phenotypes of severe P. falciparum malaria.

Methods: A hospital based study was conducted in eastern Odisha, India which is endemic to P. falciparum malaria. Common MBL-2 polymorphisms (codon 54, H-550L, and Y-221X) were typed in 336 cases of severe malaria (SM) [94 cerebral malaria (CM), 120 multi-organ dysfunction (MOD), 122 non-cerebral severe malaria (NCSM)] and 131 un-complicated malaria patients (UM). Plasma MBL levels were quantified by ELISA.

Results: Severe malaria patients displayed lower plasma levels of MBL compared to uncomplicated falciparum malaria. Furthermore, on categorization of severe malaria patients into various subtypes, plasma MBL levels were very low in MOD patients compared to other categories. Higher frequency of AB genotype and allele B was observed in MOD compared to UM (AB genotype: P = 0.006; B allele: P = 0.008). In addition, prevalence of YX genotype of MBL Y-221X polymorphism was also statistically more frequent in MOD case than UM (P = 0.009).

Conclusions: The observations of the present study reveal that MBL-2 polymorphisms (codon 54 and Y-221X) and lower plasma MBL levels are associated with increased susceptibility to multi organ dysfunctions in P. falciparum malaria.

Mannose-binding lectin (+54) exon-1 gene polymorphism influence human immunodeficiency virus-1 susceptibility in North Indians

Mannose-binding lectin (MBL) is a circulating pattern-recognition molecule involved in the innate immune system that mediates phagocytosis and activates complement by binding to carbohydrate motifs. MBL-2 allelic variants are associated with deficiencies in innate immunity and have been found to be correlated with human immunodeficiency virus (HIV) infection. The present study investigated the role of MBL-2 exon-1 gene polymorphism (A, B, C and D) in 180 HIV-1 seropositive (HSP) stratified on the basis of disease severity (stage I, II, III), 50 HIV-1 exposed seronegative (HES) and 305 HIV-1 seronegative (HSN) individuals as a possible factor in the susceptibility to HIV-1 infection and the influence on disease progression among North Indian individuals. In our population, gene frequencies of MBL-2 variants were 15%, 5% and 2% for B, C and D alleles, respectively. The frequency of A/O heterozygous genotype was higher (42.00%), mainly because of A/D in HES group compared with HSP (35.00%) and HSN (36.72%) group. Homozygous B/B genotype was more frequent in HSP (6.11%) group than in HSN (1.31%; P = 0.005; odds ratio (OR) = 4.898) and was significantly associated with fourfold risk of acquiring HIV-1 infection. Our findings indicate that homozygosity for the codon 54-allele associated with low MBL production in the exon-1 of the MBL-2 gene is associated with increased susceptibility to HIV-1 infection in the studied population.

Phylogenetic nomenclature and evolution of mannose-binding lectin (MBL2) haplotypes

Background

Polymorphisms of the mannose-binding lectin gene (MBL2) affect the concentration and functional efficiency of the protein. We recently used haplotype-specific sequencing to identify 23 MBL2 haplotypes, associated with enhanced susceptibility to several diseases.

Results

In this work, we applied the same method in 288 and 470 chromosomes from Gabonese and European adults, respectively, and found three new haplotypes in the last group. We propose a phylogenetic nomenclature to standardize MBL2 studies and found two major phylogenetic branches due to six strongly linked polymorphisms associated with high MBL production. They presented high Fst values and were imbedded in regions with high nucleotide diversity and significant Tajima's D values. Compared to others using small sample sizes and unphased genotypic data, we found differences in haplotyping, frequency estimation, Fu and Li's D* and Fst results.

Conclusion

Using extensive testing for selective neutrality, we confirmed that stochastic evolutionary factors have had a major role in shaping this polymorphic gene worldwide.

Genetic and other factors determining mannose-binding lectin levels in American Indians: the Strong Heart Study

Background

Mannose-binding lectin (MBL) forms an integral part of the innate immune system. Persistent, subclinical infections and chronic inflammatory states are hypothesized to contribute to the pathogenesis of atherosclerosis. MBL gene (MBL2) variants with between 12 to 25% allele frequency in Caucasian and other populations, result in markedly reduced expression of functional protein. Prospective epidemiologic studies, including a nested, case-control study from the present population, have demonstrated the ability of MBL2 genotypes to predict complications of atherosclerosis,. The genetic control of MBL2 expression is complex and genetic background effects in specific populations are largely unknown.

Methods

The Strong Heart Study is a longitudinal, cohort study of cardiovascular disease among American Indians. A subset of individuals genotyped for the above mentioned case-control study were selected for analysis of circulating MBL levels by double sandwich ELISA method. Mean MBL levels were compared between genotypic groups and multivariate regression was used to determine other independent factors influencing MBL2 expression.

Results

Our results confirm the effects of variant structural (B, C, and D) and promoter (H and Y) alleles that have been seen in other populations. In addition, MBL levels were found to be positively associated with male gender and hemoglobin A1c levels, but inversely related to triglyceride levels. Correlation was not found between MBL and other markers of inflammation.

Conclusion

New data is presented concerning the effects of known genetic variants on MBL levels in an American Indian population, as well as the relationship of MBL2 expression to clinical and environmental factors, including inflammatory markers.

Mannose-binding lectin gene polymorphism and its impact on human immunodeficiency virus 1 infection

Mannose-binding lectin (MBL) is a serum protein whose low concentration is associated with the occurrence of allele variants named MBL*B, MBL*C and MBL*D. The present study investigated the association between MBL gene polymorphism and the susceptibility to HIV-1 infection. The study of 145 HIV-1-infected subjects and 99 healthy controls showed the presence of alleles MBL*A, MBL*B and MBL*D, whose frequencies were 69%, 22% and 09% among patients and 71%, 13% and 16% among healthy controls, respectively. The presence of the variant MBL*B was associated with higher plasma viral load levels, suggesting the importance of the MBL gene polymorphism in the clinical evolution of HIV-1-infected patients.

Mannose-binding lectin and its genetic variants

Mannose-binding lectin (MBL) is a collagen-like serum protein that mediates activation of the complement system and is of importance for host defence. Common variant alleles situated both in the promoter and structural region of the human MBL gene (MBL2) influence the stability and the serum concentration of the protein. Epidemiological studies have suggested that genetically determined variation in MBL serum concentration influences the susceptibility to and the course of different types of infections, autoimmune, metabolic and cardiovascular diseases, but this is still a subject of debate. The fact that these genetic variations are very frequent indicates a dual role for MBL in host defence. In this survey, we summarize the current molecular understanding of human MBL genetics.

Mannose-binding lectin gene polymorphisms and hepatitis B virus infection in Vietnamese patients

Mannose-binding lectin (MBL) is a constituent of the human innate immune system which may play an important role in combating a variety of infectious diseases. We investigated the distribution of MBL gene mutations in a Vietnamese population, using polymerase chain reaction and DNA sequence analysis, and sought associations with the outcome of hepatitis B virus (HBV) infection. For this purpose we used samples from a total of 123 patients with confirmed, well-defined HBV infections, representing a full spectrum of clinical presentation from acute to chronic to malignant states, as well as from 112 healthy controls. The only MBL gene mutation found in this population, that at codon 54 of exon 1, was present at an overall frequency of 0.12, with a trend towards a higher frequency in the HBV-infected group compared with controls (0.15 versus 0.08, P = 0.079). Within the HBV-infected group there was a non-significant trend towards higher viral loads in those with this mutation, accompanied by significantly higher serum transaminase levels in the same individuals. Segregation according to clinical presentation showed that the mutation was present at a significantly higher frequency in the group with acute hepatitis B (AHB) compared with the healthy control group (0.25 versus 0.08, P = 0.01), and was associated with higher serum transaminase levels. Our results indicate that a mutation of the MBL gene might influence the clinical outcome of HBV infection in Vietnamese patients.