Severe hypertension in the Spanish population. Association with specific HLA antigens

Bioinformatic HLA Studies in the Context of SARS-CoV-2 Pandemic and Review on Association of HLA Alleles with Preexisting Medical Conditions

After the announcement of a new coronavirus in China in December 2019, which was then called SARS-CoV-2, this virus changed to a global concern and it was then declared as a pandemic by WHO. Human leukocyte antigen (HLA) alleles, which are one of the most polymorphic genes, play a pivotal role in both resistance and vulnerability of the body against viruses and other infections as well as chronic diseases. The association between HLA alleles and preexisting medical conditions such as cardiovascular diseases and diabetes mellitus is reported in various studies. In this review, we focused on the bioinformatic HLA studies to summarize the HLA alleles which responded to SARS-CoV-2 peptides and have been used to design vaccines. We also reviewed HLA alleles that are associated with comorbidities and might be related to the high mortality rate among COVID-19 patients. Since both genes and patients' medical conditions play a key role in both severity of the disease and the mortality rate in COVID-19 patients, a better understanding of the connection between HLA alleles and SARS-CoV-2 can provide a wider perspective on the behavior of the virus. Such understanding can help scientists, especially in terms of protecting healthcare workers and designing effective vaccines.

Association of HLA-DRB3*0202 and serum IgG antibodies to Chlamydia pneumoniae with essential hypertension in a highly homogeneous population from Majorca (Balearic Islands, Spain)

Separate studies investigating the relationship of essential hypertension (EH) with the HLA system and with Chlamydia pneumoniae (C. pneumoniae) infection have given conflicting results. Our aim was to clarify these relationships and determine whether the HLA system and C. pneumoniae infection interact with respect to the risk for EH. An association study (110 essential hypertensives and 107 controls) was conducted in a highly homogeneous population in the Balearic Island of Majorca (Spain). Molecular typing of HLA-B and HLA-DRB and quantification of serum levels of IgG antibodies to C. pneumoniae (sIgGa-Cp) were determined. Student's t-test, chi(2)-statistics, logistic regression analysis, and general linear model ANOVA were used for statistical analysis. The results showed that EH was related with HLA-DRB3*0202 in the whole study population, and with levels of sIgGa-Cp>63.5 BU/ml in the group of individuals with sIgGa-Cp>30 BU/ml (OR (95% CI) adjusted for obesity, familial history of EH and diabetes=2.06 (1.07-3.97), P=0.03, and =4.60 (1.06-19.90), P=0.04, respectively). The association between EH and sIgGa-Cp was observed in the DRB3*0202(+) individuals, but not in the DRB3*0202(-) subgroup (OR (95% CI)=11.14 (1.92-64.54), P=0.004, and =0.98 (0.22-4.43), P=0.64, respectively (P of the Mantel-Haenszel test for homogeneity of OR=0.06)). In our population, EH was positively associated with HLA-DRB3*0202 and with high levels of sIgGa-Cp. Moreover, a significant interaction of DRB3*0202 on the effect of sIgGa-Cp was observed, as the association of EH with these antibodies depended on the presence of DRB*0202.

HLA phenotypes as promoters of cardiovascular remodelling in subjects with arterial hypertension

The objective of this study was to investigate the association between human leukocyte antigens (HLA) phenotypes and cardiovascular remodelling, as expressed by left ventricular mass (LVM) and carotid intima-media thickness (IMT), in hypertensives. We examined 153 subjects with arterial hypertension and 61 normotensive controls living in the greater Athens area. The population was classified into three groups and specifically group I (normotensives), group II with Grade 1 hypertension and group III with Grade 2 or 3 hypertension. HLA class I and class II antigens were studied by microlymphocytotoxic technique. Carotid IMT and LVM were determined by ultrasonography. The prevalence of HLA DQ7 in the hypertensive cohort was 27.4% that was significantly smaller than the 52.5% among the controls (P = 0.002). The HLA DR11 was found in 24.0% of the hypertensives and in 52.5% of the controls (P < 0.001). Group III hypertensives with HLA DR11 exhibited significantly higher LVM/h in comparison to the hypertensives without this HLA (199.0 +/- 28.8 vs 171.2+44.1g/m, P = 0.009). This association was not present in groups I and II. Similarly, group III hypertensives with HLA DQ7 were characterized by higher IMT in comparison to those without this HLA (0.94 +/- 0.19 vs 0.83 +/- 0.23 mm, P = 0.048). HLA DR17 was associated with higher IMT in both groups II and III (1.00 +/- 0.19 vs 0.82 +/- 0.19 mm, P = 0.046 and 1.01 +/- 0.23 vs 0.84 +/- 0.22 mm, P = 0.049, respectively) but not in group I. In conclusion, certain HLA phenotypes may be related to the levels of arterial blood pressure. Moreover, it seems that these HLA phenotypes may identify subjects with arterial hypertension that are more prone to develop cardiovascular hypertrophy.

Essential hypertension and histocompatibility antigens. An association study

Data from a previous study concerning the distribution of human leukocyte antigen (HLA) haplotypes in siblings with essential hypertension suggested that at least one of the genes responsible for the genetic susceptibility to this disease is located in or near the HLA complex. The objective of the present study was to investigate if a given HLA-A, B, or DR gene could represent a marker for susceptibility to essential hypertension at the population level. Thus, the frequencies of HLA antigens were determined in Caucasian patients with essential hypertension (HLA-A and B antigens were determined in 89 cases, 85 of which were also typed for HLA-DR antigens). The results showed an increased frequency (p = 0.00064) of HLA-DR4, which was present in 34% of the patients and in 16% of local ethnically matched control subjects. We conclude that HLA-DR4 may represent a marker for susceptibility to essential hypertension in the Brazilian Caucasian population.

Essential hypertension and histocompatibility antigens. A linkage study

It is well established that genetic and environmental factors are involved in the etiology of essential hypertension. The presence of genes predisposing to essential hypertension in the human leukocyte antigen (HLA) complex is controversial because studies of an association between HLA antigens and essential hypertension have failed to yield consistent results. Our aim in the present study was to further investigate this issue through the method of linkage analysis. Analysis of 96 hypertensive siblings distributed in 31 families indicated a significant distortion (p = 0.0009) of the normal segregation pattern of inheritance of HLA haplotypes. Thus, our data indicate that at least one of the genes responsible for genetic predisposition to essential hypertension is located very near or within the HLA complex.

Possible association of MN locus haplotypes with essential hypertension

Five multigenerational kindreds with familial hypertension were typed for human leukocyte antigen (HLA) and blood group antigens to investigate genetic factors that influence variability in blood pressure. Pedigree analysis revealed that children of matings in which both parents were hypertensive had a significantly greater risk of hypertension than children of matings in which one parent or neither parent was hypertensive. Blood types N and MN were abnormally distributed among hypertensive as compared with normotensive members of white but not black families. The distribution of ABO and Rh types was not significantly different between hypertensive and normotensive siblings. When all possible pairings of siblings were examined for HLA haplotype sharing, abnormal distributions were observed among hypertensive sib pairs whereas the expected mendelian segregation was observed among hypertensive-normotensive sib pairs and normotensive-normotensive sib pairs. These results suggest the genetic factors controlling variation in blood pressure may include loci in the region of the MN locus on chromosome 4 and, possibly, the major histocompatibility complex on chromosome 6.