Potential role of killer immunoglobulin receptor genes among individuals vaccinated against hepatitis B virus in Lebanon.

AIM: To explore the role of killer immunoglobulin receptor (KIR) genes in responsiveness or non-responsiveness to vaccination against hepatitis B virus. METHODS: We recruited 101 voluntary participants between March 2010 and December 2011. Sera samples from vaccinated and non-vaccinated participants were tested for the presence of anti-HBs antibodies as a measure of protection against hepatitis B, hepatitis B surface antigen and hepatitis B core antibody as indicators of infection by enzyme-linked immunosorbent assay. KIR gene frequencies were determined by polymerase chain reaction. RESULTS: Sera samples from 99 participants were tested for the levels of anti-HBs as an indicator of protection (≥ 10 mIU/mL) following vaccination as defined by the World Health Organization international reference standard. Among the vaccinated participants, 47% (35/74) had anti-HBs titers above 100 mIU/mL, 22% (16/74) had anti-HBs ranging between 10-100 mIU/mL, and 20% (15/74) had values of less than 10 mIU/mL. We report the lack of significant association between the number of vaccine dosages and the titer of antibodies among our vaccinated participants. The inhibitory KIR2DL1, KIR2DL4, KIR3DL1, KIR3DL2, and KIR3DL were detected in more than 95%, whereas KIR2DL2, KIR2DL3, KIR2DL5 (KR2DL5A and KIR2DL5B) were expressed in 56%, 84% and 42% (25% and 29%) of participants, respectively. The observed frequency of the activating KIR genes ranged between 35% and 55% except for KIR2DS4, detected in 95% of the study participants (40.6% 2DS4*001/002; 82.2% 2DS4*003/007). KIR2DP1 pseudogene was detected in 99% of our participants, whereas KIR3DP*001/02/04 and KIR3DP1*003 had frequencies of 17% and 100%, respectively. No association between the frequency of KIR genes and anti-HBs antibodies was detected. When we compared the frequency of KIR genes between vaccinated individuals with protective antibodies titers and those who lost their protective antibody levels, we did not detect a significant difference. KIR2DL5B was significantly different among different groups of vaccinated participants (group I > 100 mIU/mL, group II 10-100 mIU/mL, group III < 10 mIU/mL and group IV with undetectable levels of protective antibodies). CONCLUSION: To our knowledge, this is the first study screening for the possible role of KIR genes among individuals vaccinated against hepatitis B virus (HBV). Our results can be used to design larger studies to better understand the role of KIR genes in protection against or susceptibility to HBV post vaccination.

Apolipoprotein E gene polymorphisms in Lebanese with hypercholesterolemia.

Apolipoprotein E (ApoE) has an important role in the metabolism of lipids through its major isoforms (ε2, ε3, ε4). In particular, ApoE ε4, has been considered as a major genetic risk factor for cardiovascular diseases (CVD). The aim of our study is to investigate the frequency of ApoE gene polymorphisms (rs 429358C>T, rs 7412C>T) and their relationship to lipid parameters in a group of Lebanese hypercholesterolemic subjects (22 males and 24 females, aged 25-80 years). Lipid profile, apolipoproteins A-I and B were determined using fasting serum samples; and molecular analysis of ApoE polymorphisms using blood in EDTA tubes. The distribution of the four ApoE genotypes detected in this study was: ε3/ε3 (73.9%), ε3/ε4 (17.4%), ε2/ε3 (6.5%), and ε2/ε4 (2.2%) resulting in allelic frequencies for ε2, ε3 and ε4 of 4.3%, 85.9% and 9.8%, respectively. No association was determined among any of the lipid parameters, gender and ApoE genotypes. Lipid parameters were not statistically different among various ApoE genotypes (p>0.05). ApoE ε2 frequency was found to be lower than that previously reported for healthy Lebanese (7.2%). CVD is one of the major leading causes of mortality in Lebanon with a reported prevalence of 12.2% in males and 7.7% in females, which incidentally agrees with our finding regarding ε4 allelic frequency of 13.6% in males and 6.3% in females. Consequently, larger prospective studies are recommended to highlight the correlation of ApoE polymorphisms to other biochemical and environmental factors involved in CVD.

Correlation of methylenetetrahydrofolate reductase polymorphisms with homocysteine metabolism in healthy Lebanese adults.

Hyperhomocysteinemia is associated with several vascular and teratogenic conditions. Determinants of total homocysteine concentrations include genetic and nutritional factors. This study assesses the relation between homocysteine concentrations and MTHFR gene polymorphisms at two common alleles (C677T (rs1801133) and A1298C (rs1801131)) as well as other predictors of homocysteine (folate, vitamin B(12), body mass index (BMI), age, and gender) in a group of healthy Lebanese: 109 males and 124 females aged 17-55years. We used serum for the determination of homocysteine, folate and vitamin B(12) levels and blood drawn in EDTA tubes for molecular analysis of MTHFR polymorphisms. Hyperhomocysteinemia was present in 59/233 (25.3%) of the subjects, with male/female ratio of 1.95. Multivariable regression analysis showed that homocysteine levels were negatively related to folate and vitamin B(12) and positively related to male gender and C677T homozygosity; but not A1298C polymorphism, BMI or age. The prevalence of wild, heterozygous, and homozygous C677T genotypes was 45.0%, 43.3% and 11.6%, respectively; with a carrier frequency of 54.9% and allelic frequency of 33.3%. The A1298C genotypic prevalence was 39.5%, 30.9%, and 29.6% respectively; with a carrier frequency of 60.5% and allelic frequency of 45.1%. C677T/A1289C compound heterozygosity was present in 47/233 (20.2%) of volunteers. In this first pilot study, gender, folate, vitamin B(12) and C677T mutational status could explain around 32% of homocysteine variations. Future larger studies are recommended to investigate other predictors of homocysteine variation and combine them with markers explored in this and other studies, in order to evaluate their impact on vascular and/or congenital diseases.

Should we screen for hereditary hemochromatosis in healthy Lebanese: a pilot study.

Hereditary hemochromatosis (HHC) is a genetic disorder of iron metabolism characterized by abnormal accumulation of iron that may lead to organ damage and death. Diagnosis is usually based on various genetic and phenotypic criteria. The study goals were to perform mutation analysis for 18 different mutations associated with HHC in healthy Lebanese, determine their allele frequency, and compare iron-overload status in identified carriers versus those found to be wild-type for mutations analyzed. 116 healthy adults (59 males and 57 females) underwent DNA testing for 18 different HHC mutations, and biochemical testing for percent transferrin saturation (%TS) and ferritin. C282Y mutation was not detected. Only H63D mutation (rs1799945) was found with an overall carrier frequency of 25.8% (24.1% heterozygous and 1.7% homozygous). %TS and ferritin differed significantly between genders. %TS and ferritin were significantly higher in males with H63D mutation when compared to males with wild-type (P=0.001, 0.019; respectively); but not in females. The proportion of subjects with increased %TS and serum ferritin was not statistically different between those with H63D mutation and the wild-type in either gender. In addition, none of the subjects had concurrent increase in %TS and ferritin. In conclusion, the H63D carrier frequency in healthy Lebanese is comparable to other populations in the region, and it does not result in significant biochemical iron overload. Moreover, in the absence of the C282Y mutation, genetic screening for HHC is not recommended according to this preliminary study in healthy Lebanese.