Aim. Periprosthetic joint infection (PJI) is one of the most serious and frequent complications in prosthetic surgery. Despite significant improvements in the criteria for diagnosis of PJI, the diagnostic workflow remains complex and, sometimes, inconclusive. Host immune factors hold great potential as diagnostic biomarkers in bone and joint infections. We have recently reported that the synovial concentration of the humoral pattern recognition molecule long pentraxin 3 (PTX3) is a sensitive and specific marker of PJI in total hip and knee arthroplasty patients (THA and TKA) undergoing revision surgery [1]. However, the contribution to risk and diagnosis of PJI of the genetic variation in PTX3 and inflammatory genes that are known to affect its expression (IL-1b, IL-6, IL-10, and IL-17A) has not been addressed. Therefore, we assessed these relationships in a cohort of THA and TKA patients who underwent prosthesis revision by focusing on a panel of single nucleotide polymorphisms (SNPs) in the PTX3, IL-1β, IL-6, IL-10 and IL-17A genes. Method. A case-control retrospective study was conducted on an historic cohort of patients that received THA or TKA revision and were diagnosed with PJI (cases) or aseptic complications (controls) [1]. Samples of saliva were collected from 93 subjects and used for extraction of genomic DNA to perform genotyping of the PTX3, IL-1β, IL-6, IL-10 and IL-17A polymorphisms. Moreover, whenever available, samples of synovial fluid and plasma [1] were used to measure the concentration of the IL-1β, IL-10, and IL-6 proteins by immunoassay. Uni-and multivariate analyses were performed to evaluate the relationships between genetic, biochemical, and clinical variables. Results. The rs3024491 (IL-10) and rs2853550 (IL-1b) SNPs were found to be strongly associated with the risk of PJI. The synovial levels of PTX3, IL-1β, IL-10, and IL-6 were higher in cases than in controls, and a clear correlation emerged between the synovial concentration of PTX3 and IL-1b in cases only. Also, we identified a causal relationship between rs2853550, synovial concentration of IL-1b and that of PTX3 (that is induced by IL-1b). Conclusions. Our findings suggest that SNPs in the IL-10 and IL-1b genes could be used for early identification of THA and TKA patients with high risk of PJI. It is therefore conceivable that integrating genetic data into current diagnostic criteria would improve diagnosis of PJI

Toll-like receptors (TLRs) are crucial components of the immune system that recognize microbial infection and trigger anti-microbial host defense responses. Gram positive bacteria are causative factors of bone infections, as they alter the balance of coordinated activities during bone remodeling, stimulating osteoclastogenesis. The aim of the study was to investigate whether genetic variation in TLR2 and TLR4 genes predisposes to bone infections’ susceptibility. One hundred and twenty patients with bone infections (osteomyelitis) and 200 healthy controls were genotyped for two single nucleotide polymorphisms (SNPs), R753Q [A/G] in TLR2 gene and T399I [C/T] in TLR4 gene. DNA was extracted from whole blood and the above SNPs were typed with PCR-RFLP (Polymerase Chain Reaction- Restriction Fragment Length Polymorphism) method for genotype identification. All patients were infected by Gram-positive bacteria, predominantly Staphylococcus aureus. Statistical analysis was carried out using the chi-square test. We observed a significantly increased frequency in patients carrying the GA genotype of TLR2 R753Q polymorphism compared to controls (p<0.05). We also found that the A allele was more common in patients than in controls. All individuals carrying the A allele were heterozygous for this variant, while homozygous mutant individuals were not detected in the patients and the control group. In contrast, we found that the TLR4 T399I [C/T] SNP was similarly distributed among the two groups (patients and controls). The mechanism through which TLR2 mediates its effect in bone infections is under investigation. A significant difference was observed in the genotype frequency of TLR2 R753Q [A/G] polymorphism in patients, suggesting that genetic variability in TLR2 gene may be associated with susceptibility to osteomyelitis in response to bacterial invasion in the bone

The Osteoprotegerin/RANK/RANKL system has been implicated in the biological cascade of events initiated by particulate wear debris and bacterial infection resulting in periprosthetic bone loss around loosened total hip arthroplasties (THA). Individual responses to such stimuli may be dictated by genetic variation and we have studied the effect of single nucleotide polymorphisms (SNPs) within these genes. We performed a case control study of the Osteoprotegerin, RANK and RANKL genes for possible association with deep sepsis or aseptic loosening. All patients included in the study were Caucasian and had had a cemented Charnley THA and polyethylene acetabular cup. Cases consisted of 91 patients with early aseptic loosening and 71 patients with microbiological evidence at surgery of deep infection. Controls consisted of 150 THAs that were clinically asymptomatic for over 10 years and demonstrated no radiographic features of aseptic loosening. DNA samples from all individuals were genotyped using Taqman allelic discrimination. The A allele (p<0.001) and homozygous genotype A/A (p<0.001) for the OPG-163 SNP were highly associated with aseptic failure. Additionally, the RANK-575 (C/T SNP) T allele (p=0.004) and T/T genotype (p=0.008) frequencies were associated with aseptic failure. No statistically significant relationship was found between aseptic loosening and the OPG- 245 or OPG-1181 SNPs. When the septic group was compared to controls, the frequency of the A allele (p<0.001) and homozygous genotype A/A (p<0.001) for the OPG-163 SNP were statistically significant. No statistically significant relationship was found between septic failure and the OPG- 245, OPG-1181 or RANK-575 SNPs. Aseptic loosening and possibly deep infection of THA may be under genetic influence to candidate susceptibility genes. SNP markers may serve as predictors of implant survival and aid pharmacogenomic prevention of THA failure