Dinko Pavlinić

Heterozygous carriage of a dysfunctional Toll-like receptor 9 allele affects CpG oligonucleotide responses in B cells.

Background: Human B cells respond to Toll-like receptor (TLR) 9 stimulation by cytokine production. Results: A rare, novel TLR9 allele fails to activate NF-κB in HEK293 cells. Heterozygous carrier B cells show defective IL-6 and IL-10 production. Conclusion: Heterozygosity for this TLR9 allele modifies CpG oligonucleotide responsiveness. Significance: This is the first analysis of human TLR9 variants in primary cells. Toll-like receptors (TLR) are employed by the innate immune system to detect microbial pathogens based on conserved microbial pathogen molecules. For example, TLR9 is a receptor for CpG-containing microbial DNA, and its activation results in the production of cytokines and type I interferons from human B cells and plasmacytoid dendritic cells, respectively. Both are required for mounting an efficient antibacterial or antiviral immune response. These effects are mimicked by synthetic CpG oligodeoxynucleotides (ODN). Although several hyporesponsive TLR9 variants have been reported, their functional relevance in human primary cells has not been addressed. Here we report a novel TLR9 allele, R892W, which is hyporesponsive to CpG ODN and acts as a dominant-negative in a cellular model system. The R892W variant is characterized by increased MyD88 binding and defective co-localization with CpG ODN. Whereas primary plasmacytoid dendritic cells isolated from a heterozygous R892W carrier responded normally to CpG by interferon-α production, carrier B cells showed impaired IL-6 and IL-10 production. This suggests that heterozygous carriage of a hyporesponsive TLR9 allele is not associated with complete loss of TLR9 function but that TLR9 signals elicited in different cell types are regulated differently in human primary cells.

Down syndrome: parental origin, recombination, and maternal age.

The aims of the present study were to assess (1) the parental origin of trisomy 21 and the stage in which nondisjunction occurs and (2) the relationship between altered genetic recombination and maternal age as risk factors for trisomy 21. The study included 102 cases with Down syndrome from the Croatian population. Genotyping analyses were performed by polymerase chain reaction using 11 short tandem repeat markers along chromosome 21q. The vast majority of trisomy 21 was of maternal origin (93%), followed by paternal (5%) and mitotic origin (2%). The frequencies of maternal meiotic I (MI) and meiotic II errors were 86% and 14%, respectively. The highest proportion of cases with zero recombination was observed among those with maternal MI derived trisomy 21. A higher proportion of telomeric exchanges were presented in cases with maternal MI errors and cases with young mothers, although these findings were not statistically significant. The present study is the first report examining parental origin and altered genetic recombination as a risk factor for trisomy 21 in a Croatian population. The results support that trisomy 21 has a universal genetic etiology across different human populations.

The relationship between interferon-γ gene polymorphism and acute kidney allograft rejection.

Cytokine gene polymorphisms have been associated with modified gene expression and cytokine production. Gamma interferon (IFN‐γ) plays an important role in the pathogenesis of kidney transplant rejection. This study evaluated the association between IFN‐γ gene polymorphisms and the history of acute allograft rejection in 53 adult first‐transplant recipients receiving cadaveric kidney grafts. They were followed up in a single centre until 2006, for a median time of 4 years after transplantation (1–22 years). IFN‐γ gene polymorphisms +874 T/A (rs2430561) were determined by polymerase chain reaction (PCR). T/T high IFN‐γ genotype was found in 12, intermediate T/A in 29 and low A/A in 12 patients. Twenty‐six acute kidney rejection episodes were evidenced in 20 patients, of which none occurred in the 12 patients with low IFN‐γ genotype A/A. Age, gender, number of HLA (human leukocyte antigen) mismatches, ABO blood groups, HLA, time after transplantation, creatinine clearance and immunosuppressive regimens were excluded as confounding factors associated with IFN‐γ genotype distribution between rejectors and non‐rejectors. IFN‐γ gene polymorphisms could be an important risk factor for acute kidney transplant rejection, whereas the low A/A IFN‐γ genotype could be protective against rejection.

Frequency Determination of α-1,3 Glucosyltransferase p.Y131H and p.F304S Polymorphisms in the Croatian Population Revealed Five Novel Single Nucleotide Polymorphisms in the hALG6 Gene

The congenital disorder of glycosylation (CDG)-Ic (ALG6-CDG, CDG-Ic) is caused by mutations in the hALG6 gene that encodes the N-glycosylation pathway enzyme, α-1,3-glucosyltransferase (NP_037471.2). The aim of our study was to estimate the frequencies of ALG6-CDG related p.Y131H and p.F304S polymorphisms in the Croatian population. Genomic DNA was isolated from blood samples collected from 600 healthy individuals. Functional single-nucleotide polymorphisms rs35383149 and rs17856039 causing p.Y131H and p.F304S, respectively, were genotyped by the TaqMan method and direct sequencing. The frequency of p.F304S polymorphism in the studied cohort was shown to be similar to the frequencies found in other tested populations (27%), whereas the frequency of p.Y131H was found to be three times higher (6.7%). Five novel base substitutions in the hALG6 gene were also found: three in exon 5 (c.383T>C, c.390G>A, and c.429G>C) and two in a downstream intervening sequence (IVS5+17C/T and IVS5+34G/A).

Distribution of Chlamydia trachomatis Serotypes in Clinical Urogenital Samples from North-Eastern Croatia

The purpose of this study was to determine prevalence of Chlamydia trachomatis (Ct) urogenital infection and its serotype distribution from clinical samples in north-eastern Croatia. During a 3-year period, 2,379 urogenital samples were analyzed by real-time polymerase chain reaction (A group), while 4,846 genital swabs were analyzed by direct fluorescent antibody test (B group). 132 Ct positive specimens were genotyped by omp1 gene sequencing. The prevalence rate of Ct was 3.2 % in A and 1 % in B group. The most prevalent chlamydial genotype was E (44 %), followed by F (33 %), K (11.5 %), G (8 %), J/UW (5.3 %), D-IC (4.4 %), D-B120 (1.8 %), and B/IU, J/IU, Ia/IU (0.9 % each) serotypes. Single-nucleotide polymorphisms (SNPs) of omp1 gene were detected in E, K, and G serotypes. Some of these SNPs (C/T at position 272 and G/A at position 813 in E strain; C/T at position 884 in D strain) might represent novel omp1 variants.