Irene Leijonhufvud

A genetic basis of susceptibility to acute pyelonephritis.

Background For unknown reasons, urinary tract infections (UTIs) are clustered in certain individuals. Here we propose a novel, genetically determined cause of susceptibility to acute pyelonephritis, which is the most severe form of UTI. The IL-8 receptor, CXCR1, was identified as a candidate gene when mIL-8Rh mutant mice developed acute pyelonephritis (APN) with severe tissue damage. Methods and Findings We have obtained CXCR1 sequences from two, highly selected APN prone patient groups, and detected three unique mutations and two known polymorphisms with a genotype frequency of 23% and 25% compared to 7% in controls (p<0.001 and p<0.0001, respectively). When reflux was excluded, 54% of the patients had CXCR1 sequence variants. The UTI prone children expressed less CXCR1 protein than the pediatric controls (p<0.0001) and two sequence variants were shown to impair transcription. Conclusions The results identify a genetic innate immune deficiency, with a strong link to APN and renal scarring.

Reduced Toll-Like Receptor 4 Expression in Children with Asymptomatic Bacteriuria

Toll-like receptor (TLR) 4 is essential for the defense against infection with gram-negative pathogens, but reduced TLR4 expression has not been linked to altered disease susceptibility in humans. In mice, Tlr4 controls the mucosal response to Escherichia coli urinary tract infections. Inactivation of mouse Tlr4 causes an asymptomatic carrier state resembling asymptomatic bacteriuria (ABU). The present study compared neutrophil TLR4 expression levels between children with ABU (n=17) and age-matched control subjects (n=24), and significantly lower levels were detected in the patients with ABU. We also found elevated levels of the TLR4 adaptor protein TRIF and reduced levels of the TLR4-inhibitor SIGIRR in the patients with ABU, but MyD88 and TRAM levels were not significantly altered. Altered TLR4 and adaptor protein expression might impair TLR4 signaling and explain the weak mucosal response to urinary tract infection in patients who develop ABU rather than symptomatic disease.

PapG-Dependent Adherence Breaks Mucosal Inertia and Triggers the Innate Host Response

Mucosal pathogens differ from normal flora constituents in that they provoke a host response that upsets mucosal integrity. We investigated whether the elaboration of discrete adherence factors is sufficient to break the inertia of the mucosal barrier. PapG-mediated adherence was selected as an example, because P fimbrial expression characterizes uropathogenic Escherichia coli and because adherence starts the attack on the mucosal barrier. Patients were inoculated intravesically with transformed nonvirulent E. coli strains expressing functional P fimbriae (E. coli pap(+)) or mutant fimbriae lacking the adhesin (E. coli Delta papG). E. coli pap(+) was shown to activate the innate host response, and adherent gfp(+) bacteria were observed on excreted uroepithelial cells. E. coli Delta papG failed to trigger a response and was nonadhesive. We conclude that PapG-mediated adherence breaks mucosal inertia in the human urinary tract by triggering innate immunity and propose that this activation step differentiates asymptomatic carriage from infection.

Toll-like receptor 4 promoter polymorphisms: common TLR4 variants may protect against severe urinary tract infection.

Background Polymorphisms affecting Toll-like receptor (TLR) structure appear to be rare, as would be expected due to their essential coordinator role in innate immunity. Here, we assess variation in TLR4 expression, rather than structure, as a mechanism to diversify innate immune responses. Methodology/Principal Findings We sequenced the TLR4 promoter (4,3 kb) in Swedish blood donors. Since TLR4 plays a vital role in susceptibility to urinary tract infection (UTI), promoter sequences were obtained from children with mild or severe disease. We performed a case-control study of pediatric patients with asymptomatic bacteriuria (ABU) or those prone to recurrent acute pyelonephritis (APN). Promoter activity of the single SNPs or multiple allelic changes corresponding to the genotype patterns (GPs) was tested. We then conducted a replication study in an independent cohort of adult patients with a history of childhood APN. Last, in vivo effects of the different GPs were examined after therapeutic intravesical inoculation of 19 patients with Escherichia coli 83972. We identified in total eight TLR4 promoter sequence variants in the Swedish control population, forming 19 haplotypes and 29 genotype patterns, some with effects on promoter activity. Compared to symptomatic patients and healthy controls, ABU patients had fewer genotype patterns, and their promoter sequence variants reduced TLR4 expression in response to infection. The ABU associated GPs also reduced innate immune responses in patients who were subjected to therapeutic urinary E. coli tract inoculation. Conclusions The results suggest that genetic variation in the TLR4 promoter may be an essential, largely overlooked mechanism to influence TLR4 expression and UTI susceptibility.

Inherited susceptibility to acute pyelonephritis : A family study of urinary tract infection

BACKGROUND Urinary tract infections (UTIs) are important causes of morbidity and death. The present study investigated whether genetic factors influence susceptibility to acute pyelonephritis (APN). CXCR1 expression was investigated as a factor predisposing to APN, because low CXCR1 expression has been associated with disease susceptibility in mice and disease-prone children. METHODS The families of APN-prone children (n=130) and of age-matched control subjects without UTI (n=101) were studied. Three-generation pedigrees of UTI-associated morbidity were established by means of structured interviews of the families. CXCR1 expression was quantified by flow cytometric analysis of peripheral blood neutrophils obtained from family members and control subjects. RESULTS APN was significantly more common in the family members of the APN-prone children (20 [15%] of 130 family members) than in the relatives of the control subjects (3 [3%] of 101 family members) (P<.002). Acute cystitis, in contrast, occurred with equal frequency in both groups (19%; P=1.0). Some families included many affected individuals, consistent with a dominant pattern of inheritance, whereas other families showed a recessive pattern of disease susceptibility. CXCR1 expression was significantly lower in the APN-prone children and in their relatives than in pediatric and adult control subjects (P<.0001). CONCLUSIONS Our results suggest that susceptibility to APN is inherited and that low CXCR1 expression might predispose to disease.

The host response to urinary tract infection.

The authors use the UTI model to identify basic mechanisms of disease pathogenesis, host response induction, and defense. Their studies hold the promise to provide a molecular and genetic explanation for susceptibility to UTI, and to offer more precise tools for diagnosis and therapy of these infections. There are few infections where the host response is understood in such detail and where pathologic host responses can be linked to distinct disease states. The susceptibility to UTI varies greatly in the population. The studies suggest that distinct molecular defects can cause the clinical entity of acute pyelonephritis with renal scarring, and suggest that the susceptibility to UTI in certain patient groups may have a genetic basis. In addition, the distinct signal transduction pathways explain the development of symptoms, and propose that defects in those signaling mechanisms may occur in patients with ABU. In the future, it may be useful to include these host response parameters in the diagnostic arsenal, to help in early detection of patients susceptible to recurrent UTI and renal scarring. These patients may then be offered therapies that strengthen their defense, and be offered close surveillance for recurrences and other complications.

Do type 1 fimbriae promote inflammation in the human urinary tract

Type 1 fimbriae have been implicated as virulence factors in animal models of urinary tract infection (UTI), but the function in human disease remains unclear. This study used a human challenge model to examine if type 1 fimbriae trigger inflammation in the urinary tract. The asymptomatic bacteriuria strain Escherichia coli 83972, which fails to express type 1 fimbriae, due to a 4.25 kb fimB–fimD deletion, was reconstituted with a functional fim gene cluster and fimbrial expression was monitored through a gfp reporter. Each patient was inoculated with the fim+ or fim− variants on separate occasions, and the host response to type 1 fimbriae was quantified by intraindividual comparisons of the responses to the fim+ or fim− isogens, using cytokines and neutrophils as end‐points. Type 1 fimbriae did not promote inflammation and adherence was poor, as examined on exfoliated cells in urine. This was unexpected, as type 1 fimbriae enhanced the inflammatory response to the same strain in the murine urinary tract and as P fimbrial expression by E. coli 83972 enhances adherence and inflammation in challenged patients. We conclude that type 1 fimbriae do not contribute to the mucosal inflammatory response in the human urinary tract.

High prevalence of hypogonadism and associated impaired metabolic and bone mineral status in subfertile men.

It is yet unknown to which degree young subfertile men present with signs of hypogonadism and whether low testosterone concentration, like in older men, is associated with risk of osteoporosis and metabolic derangements in those subjects. The objective was therefore to investigate the prevalence of hypogonadism and its association with metabolic and bone parameters in young subfertile men.

Risk of low bone mineral density in testicular germ cell cancer survivors: association with hypogonadism and treatment modality

The cure rate of testicular cancer exceeds 95%, but testicular cancer survivors (TCS) are at increased risk of hypogonadism (HG). It has been suggested that TCS have reduced bone mineral density (BMD), but it is unclear whether this is related to HG or a direct effect of cancer therapy. The aim of this study was to evaluate whether TCS have decreased BMD, and if BMD is related to HG and/or the cancer treatment given. We investigated 91 TCS (mean age at diagnosis: 31 years; mean 9.3 years follow‐up) and equal number of age matched controls (mean age at inclusion 40.3 years and 41.2 years, respectively). Total testosterone and LH were measured. BMD was determined using dual‐energy X‐ray absorptiometry (DXA). Low BMD (LBD) was defined as Z‐score <−1. Compared to eugonadal TCS, both TCS with untreated HG (mean difference: −0.063 g/cm2; 95% CI: −0.122; −0.004 p = 0.037) and TCS receiving androgen replacement (mean difference −0.085 g/cm2; 95% CI: −0.168; −0.003; p = 0.043) presented with statistically significantly 6–8% lower hip BMD. At the spine, L1–L4, an 8% difference reached the level of statistical significance only for those with untreated HG (mean difference: −0.097 g/cm2; 95% CI: −0.179; −0.014; p = 0.022). TCS with untreated HG had significantly increased OR for spine L1–L4 LBD (OR = 4.1; 95% CI: 1.3; 13; p = 0.020). The associations between the treatment given and BMD were statistically non‐significant, both with and without adjustment for HG. In conclusion, TCS with HG are at increased risk of impaired bone health. Prevention of osteoporosis should be considered as an important part in future follow up of these men.

Hypogonadism in testicular cancer patients is associated with risk factors of cardiovascular disease and the metabolic syndrome

More than 95% of testicular cancer are cured but they are at increased long‐term risk of cardiovascular disease. The risk of cardiovascular disease and treatment intensity was reported, but it is unknown whether this effect of cancer therapy is direct or indirect, mediated through androgen deficiency. Our aim was, therefore, to evaluate whether testicular cancer patients have increased the prevalence of risk factors of cardiovascular disease and if these risk factors are associated with hypogonadism and/or the cancer treatment given. In 92 testicular cancer patients (mean 9.2 years follow‐up) and age‐matched controls, blood samples were analysed for lipids, total testosterone, luteinizing hormone (LH), glucose and insulin. An estimate of insulin resistance, HOMAir was calculated. Hypogonadism was defined as total testosterone < 10 nmol/L and/or LH > 10 IU/L and/or androgen replacement. In testicular cancer men with hypogonadism, compared with eugonadal patients, higher insulin (mean difference: 3.10 mIU/L; p = 0.002) and HOMAir (mean difference: 0.792; p = 0.007) were detected. Hypogonadism group presented with increased risk (OR = 4.4; p = 0.01) of metabolic syndrome. Most associations between the treatment given and the metabolic parameters became statistically non‐significant after adjustment for hypogonadism. In conclusion, testicular cancer patients with signs of hypogonadism presented with significantly increased risk of metabolic syndrome and investigation of endocrine and metabolic parameters is warranted in these patients.