Polymorphisms of CX3CL1- receptor (CX3CR1) gene in patients with Shigatoxin-producing E. coli infections with or without progression to Hemolytic Uremic Syndrome (HUS)

CECILIA A. PANEK; MARIA V. RAMOS; MARÍA P. MEJIAS; ROMINA J. FERNÁNDEZ-BRANDO; LETICIA V. BENTANCOR; C. EXENI; A. EXENI; M.C. LAZO; RAMÓN A. EXENI; CHRISTOPHE COMBADIERE; MARINA S. PALERMO

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Conferencia; Gordon Research Conferences – Chemotactic cytokines; 2010

Abstract Hemolytic Uremic Syndrome (HUS), a vascular disease characterized by nephropathy, thrombocytopenia, and hemolytic anemia, is a life-threatening systemic complication that occurs in 10% of children infected with enterohemorraghic Shiga-toxins (Stx) producing-bacteria (STEC). We have found that HUS patients present a significant decrease in circulating leukocytes expressing the CX3CR1 (monocytes and Natural killer cells), which correlated with poor prognosis. In addition, CX3CR1+ leukocytes were detected in renal biopsies of HUS patients. Two single-nucleotide polymorphisms of the CX3CR1 gene (T280M and V249I) affect fractalkine receptor expression and function.We aimed to assess the prevalence of CX3CR1 polymorphisms and the association with evolution to HUS in a case-control cohort, in which we included STEC-infected children with (HUS) or without HUS-evolution (STEC-I) and age-matched healthy controls (HC). METHODS: DNA extraction from urine samples and PCR-RFLP technique was used to analyze allelotypes for T280M and V249I in 39 HUS patients, 6 STEC-I and 37 HC. Results: we observed the following frequencies (%) of genotypes in HUS patients(n=39): VV-TT (56); VI-TT (15); VI-TM (23); II-MM (3); II-TM (3). STEC-I patients (n=6): VV-TT (66), VI-TT (17) and VI-TM (17); and HC: VV-TT (56); VI-TT (19); VI-TM (11); II-MM (3); II-TM (11). The frequency of I249 carriers was 42 and 44 for HC and HUS, respectively. The frequency of the M280 carriers was 25 and 29 for HC and HUS, respectively. When we analyze the frequency of haplotypes we found: HUS: VT= 76%, IT=9% and IM= 15%; HC: VT=70%, IT= 16% and IM= 14%, ratio IT/IM: HUS =0.6 and HC= 1.2. Conclusions:We conclude that: 1) it is possible to determine CX3CR1 genetic polymorphisms from urine samples in pediatric patients; and 2) although a major number of patients is necessary to reach a definitive conclusion, the data found suggest that: The homozygosity of CX3CR1-I249 was less frequent in the HUS group, suggesting that this allele may act as a protective genetic factor; B) The relative frequency of VI-TT/VI-TM combined genotypes are reversed in HUS patients compared to controls: 0.66 vs 1.73 respectively, suggesting that any hazardous effect of CX3CR1-M280 is reversed by possession of homozygosity for CX3CR1-I249. Finally, since defective receptor CX3CR1-M280 actually has two aa changes, the functional defect could be caused by M280 or I249 acting alone or by both together.