Asymptomatic bacteriuria in sickle cell disease: a cross-sectional study

BACKGROUND: It is known that there is significant morbidity associated with urinary tract infection and with renal dysfunction in sickle cell disease (SCD). However, it is not known if there are potential adverse outcomes associated with asymptomatic bacteriuria (ASB) infections in sickle cell disease if left untreated. This study was undertaken to determine the prevalence of ASB, in a cohort of patients with SCD. METHODS: This is a cross-sectional study of patients in the Jamaican Sickle Cell Cohort. Aseptically collected mid-stream urine (MSU) samples were obtained from 266 patients for urinalysis, culture and sensitivity analysis. Proteinuria was measured by urine dipsticks. Individuals with abnormal urine culture results had repeat urine culture. Serum creatinine was measured and steady state haematology and uric acid concentrations were obtained from clinical records. This was completed at a primary care health clinic dedicated to sickle cell diseases in Kingston, Jamaica. There were 133 males and 133 females in the sample studied. The mean age (mean ± sd) of participants was 26.6 ± 2.5 years. The main outcome measures were the culture of ≥ 10(5 )colony forming units of a urinary tract pathogen per milliliter of urine from a MSU specimen on a single occasion (probable ASB) or on consecutive occasions (confirmed ASB). RESULTS: Of the 266 urines collected, 234 were sterile and 29 had significant bacteriuria yielding a prevalence of probable ASB of 10.9% (29/266). Fourteen patients had confirmed ASB (prevalence 5.3%) of which 13 had pyuria. Controlling for genotype, females were 14.7 times more likely to have confirmed ASB compared to males (95%CI 1.8 to 121.0). The number of recorded visits for symptomatic UTI was increased by a factor of 2.5 (95% CI 1.4 to 4.5, p < 0.005) but serum creatinine, uric acid and haematology values were not different in patients with confirmed ASB compared with those with sterile urine. There was no association with history of gram negative sepsis. CONCLUSION: ASB is a significant problem in individuals with SCD and may be the source of pathogens in UTI. However, further research is needed to determine the clinical significance of ASB in SCD

De Novo Generation of Infectious Prions In Vitro Produces a New Disease Phenotype

Prions are the proteinaceous infectious agents responsible for Transmissible Spongiform Encephalopathies. Compelling evidence supports the hypothesis that prions are composed exclusively of a misfolded version of the prion protein (PrPSc) that replicates in the body in the absence of nucleic acids by inducing the misfolding of the cellular prion protein (PrPC). The most common form of human prion disease is sporadic, which appears to have its origin in a low frequency event of spontaneous misfolding to generate the first PrPSc particle that then propagates as in the infectious form of the disease. The main goal of this study was to mimic an early event in the etiology of sporadic disease by attempting de novo generation of infectious PrPSc in vitro. For this purpose we analyzed in detail the possibility of spontaneous generation of PrPSc by the protein misfolding cyclic amplification (PMCA) procedure. Under standard PMCA conditions, and taking precautions to avoid cross-contamination, de novo generation of PrPSc was never observed, supporting the use of the technology for diagnostic applications. However, we report that PMCA can be modified to generate PrPSc in the absence of pre-existing PrPSc in different animal species at a low and variable rate. De novo generated PrPSc was infectious when inoculated into wild type hamsters, producing a new disease phenotype with unique clinical, neuropathological and biochemical features. Our results represent additional evidence in support of the prion hypothesis and provide a simple model to study the mechanism of sporadic prion disease. The findings also suggest that prion diversity is not restricted to those currently known, and that likely new forms of infectious protein foldings may be produced, resulting in novel disease phenotypes

Highly Efficient Protein Misfolding Cyclic Amplification

Protein misfolding cyclic amplification (PMCA) provides faithful replication of mammalian prions in vitro and has numerous applications in prion research. However, the low efficiency of conversion of PrPC into PrPSc in PMCA limits the applicability of PMCA for many uses including structural studies of infectious prions. It also implies that only a small sub-fraction of PrPC may be available for conversion. Here we show that the yield, rate, and robustness of prion conversion and the sensitivity of prion detection are significantly improved by a simple modification of the PMCA format. Conducting PMCA reactions in the presence of Teflon beads (PMCAb) increased the conversion of PrPC into PrPSc from ∼10% to up to 100%. In PMCAb, a single 24-hour round consistently amplified PrPSc by 600-700-fold. Furthermore, the sensitivity of prion detection in one round (24 hours) increased by 2-3 orders of magnitude. Using serial PMCAb, a 1012-fold dilution of scrapie brain material could be amplified to the level detectible by Western blotting in 3 rounds (72 hours). The improvements in amplification efficiency were observed for the commonly used hamster 263K strain and for the synthetic strain SSLOW that otherwise amplifies poorly in PMCA. The increase in the amplification efficiency did not come at the expense of prion replication specificity. The current study demonstrates that poor conversion efficiencies observed previously have not been due to the scarcity of a sub-fraction of PrPC susceptible to conversion nor due to limited concentrations of essential cellular cofactors required for conversion. The new PMCAb format offers immediate practical benefits and opens new avenues for developing fast ultrasensitive assays and for producing abundant quantities of PrPSc in vitro

Quantitative Detection and Biological Propagation of Scrapie Seeding Activity In Vitro Facilitate Use of Prions as Model Pathogens for Disinfection

Prions are pathogens with an unusually high tolerance to inactivation and constitute a complex challenge to the re-processing of surgical instruments. On the other hand, however, they provide an informative paradigm which has been exploited successfully for the development of novel broad-range disinfectants simultaneously active also against bacteria, viruses and fungi. Here we report on the development of a methodological platform that further facilitates the use of scrapie prions as model pathogens for disinfection. We used specifically adapted serial protein misfolding cyclic amplification (PMCA) for the quantitative detection, on steel wires providing model carriers for decontamination, of 263K scrapie seeding activity converting normal protease-sensitive into abnormal protease-resistant prion protein. Reference steel wires carrying defined amounts of scrapie infectivity were used for assay calibration, while scrapie-contaminated test steel wires were subjected to fifteen different procedures for disinfection that yielded scrapie titre reductions of ≤101- to ≥105.5-fold. As confirmed by titration in hamsters the residual scrapie infectivity on test wires could be reliably deduced for all examined disinfection procedures, from our quantitative seeding activity assay. Furthermore, we found that scrapie seeding activity present in 263K hamster brain homogenate or multiplied by PMCA of scrapie-contaminated steel wires both triggered accumulation of protease-resistant prion protein and was further propagated in a novel cell assay for 263K scrapie prions, i.e., cerebral glial cell cultures from hamsters. The findings from our PMCA- and glial cell culture assays revealed scrapie seeding activity as a biochemically and biologically replicative principle in vitro, with the former being quantitatively linked to prion infectivity detected on steel wires in vivo. When combined, our in vitro assays provide an alternative to titrations of biological scrapie infectivity in animals that substantially facilitates the use of prions as potentially highly indicative test agents in the search for novel broad-range disinfectants

Highly Efficient Amplification of Chronic Wasting Disease Agent by Protein Misfolding Cyclic Amplification with Beads (PMCAb)

Protein misfolding cyclic amplification (PMCA) has emerged as an important technique for detecting low levels of pathogenic prion protein in biological samples. The method exploits the ability of the pathogenic prion protein to convert the normal prion protein to a proteinase K-resistant conformation. Inclusion of Teflon® beads in the PMCA reaction (PMCAb) has been previously shown to increase the sensitivity and robustness of detection for the 263 K and SSLOW strains of hamster-adapted prions. Here, we demonstrate that PMCAb with saponin dramatically increases the sensitivity of detection for chronic wasting disease (CWD) agent without compromising the specificity of the assay (i.e., no false positive results). Addition of Teflon® beads increased the robustness of the PMCA reaction, resulting in a decrease in the variability of PMCA results. Three rounds of serial PMCAb allowed detection of CWD agent from a 6.7×10−13 dilution of 10% brain homogenate (1.3 fg of source brain). Titration of the same brain homogenate in transgenic mice expressing cervid prion protein (Tg(CerPrP)1536+/− mice) allowed detection of CWD agent from the 10−6 dilution of 10% brain homogenate. PMCAb is, thus, more sensitive than bioassay in transgenic mice by a factor exceeding 105. Additionally, we are able to amplify CWD agent from brain tissue and lymph nodes of CWD-positive white-tailed deer having Prnp alleles associated with reduced disease susceptibility

Higher Rates of Hemolysis Are Not Associated with Albuminuria in Jamaicans with Sickle Cell Disease

BACKGROUND: Albuminuria is a marker of glomerular damage in Sickle Cell Disease (SCD). In this study, we sought to determine the possible predictors of albuminuria in the two more prevalent genotypes of SCD among the Jamaica Sickle Cell Cohort Study participants. METHODS: An age-matched cohort of 122 patients with HbSS or HbSC genotypes had measurements of their morning urine albumin concentration, blood pressure, body mass index, haematology and certain biochemistry parameters done. Associations of albuminuria with possible predictors including hematological parameters, reticulocyte counts, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels were examined using multiple regression models. RESULTS: A total of 122 participants were recruited (mean age 28.6 years ±2.5 years; 85 HbSS, 37 HbSC). 25.9% with HbSS and 10.8% with HbSC disease had microalbuminuria (urine albumin/creatinine ratio  =  30-300 mg/g of creatinine) whereas 16.5% of HbSS and 2.7% of HbSC disease had macroalbuminuria (urine albumin/creatinine ratio>300 mg/g of creatinine). Mean arterial pressure, hemoglobin levels, serum creatinine, reticulocyte counts and white blood cell counts were statistically significant predictors of albuminuria in HbSS, whereas white blood cell counts and serum creatinine predicted albuminuria in HbSC disease. Both markers of chronic hemolysis, i.e. AST and LDH levels, showed no associations with albuminuria in either genotype. CONCLUSIONS: Renal disease, as evidenced by excretion of increased amounts of albumin in urine due to a glomerulopathy, is a common end-organ complication in SCD. It is shown to be more severe in those with HbSS disease than in HbSC disease. Rising blood pressure, lower hemoglobin levels and higher white blood cell counts are hints to the clinician of impending renal disease, whereas higher rates of hemolysis do not appear to play a role in this complication of SCD

Prion Seeding Activities of Mouse Scrapie Strains with Divergent PrPSc Protease Sensitivities and Amyloid Plaque Content Using RT-QuIC and eQuIC

Different transmissible spongiform encephalopathy (TSE)-associated forms of prion protein (e.g. PrPSc) can vary markedly in ultrastructure and biochemical characteristics, but each is propagated in the host. PrPSc propagation involves conversion from its normal isoform, PrPC, by a seeded or templated polymerization mechanism. Such a mechanism is also the basis of the RT-QuIC and eQuIC prion assays which use recombinant PrP (rPrPSen) as a substrate. These ultrasensitive detection assays have been developed for TSE prions of several host species and sample tissues, but not for murine models which are central to TSE pathogenesis research. Here we have adapted RT-QuIC and eQuIC to various murine prions and evaluated how seeding activity depends on glycophosphatidylinositol (GPI) anchoring and the abundance of amyloid plaques and protease-resistant PrPSc (PrPRes). Scrapie brain dilutions up to 10-8 and 10-13 were detected by RT-QuIC and eQuIC, respectively. Comparisons of scrapie-affected wild-type mice and transgenic mice expressing GPI anchorless PrP showed that, although similar concentrations of seeding activity accumulated in brain, the heavily amyloid-laden anchorless mouse tissue seeded more rapid reactions. Next we compared seeding activities in the brains of mice with similar infectivity titers, but widely divergent PrPRes levels. For this purpose we compared the 263K and 139A scrapie strains in transgenic mice expressing P101L PrPC. Although the brains of 263K-affected mice had no immunoblot-detectable PrPRes, RT-QuIC indicated that seeding activity was comparable to that associated with a high-PrPRes strain, 139A. Thus, in this comparison, RT-QuIC seeding activity correlated more closely with infectivity than with PrPRes levels. We also found that eQuIC, which incorporates a PrPSc immunoprecipitation step, detected seeding activity in plasma from wild-type and anchorless PrP transgenic mice inoculated with 22L, 79A and/or RML scrapie strains. Overall, we conclude that these new mouse-adapted prion seeding assays detect diverse types of PrPSc

Immunopurification of Pathological Prion Protein Aggregates

Background: Prion diseases are fatal neurodegenerative disorders that can arise sporadically, be genetically inherited or acquired through infection. The key event in these diseases is misfolding of the cellular prion protein (PrP) into a pathogenic isoform that is rich in β-sheet structure. This conformational change may result in the formation of PrP, the prion isoform of PrP, which propagates itself by imprinting its aberrant conformation onto PrP molecules. A great deal of effort has been devoted to developing protocols for purifying PrP for structural studies, and testing its biological properties. Most procedures rely on protease digestion, allowing efficient purification of PrP27-30, the protease-resistant core of PrP. However, protease treatment cannot be used to isolate abnormal forms of PrP lacking conventional protease resistance, such as those found in several genetic and atypical sporadic cases. Principal Findings: We developed a method for purifying pathological PrP molecules based on sequential centrifugation and immunoprecipitation with a monoclonal antibody selective for aggregated PrP. With this procedure we purified full-length PrP and mutant PrP aggregates at electrophoretic homogeneity. PrP purified from prion-infected mice was able to seed misfolding of PrP in a protein misfolding cyclic amplification reaction, and mutant PrP aggregates from transgenic mice were toxic to cultured neurons. Significance: The immunopurification protocol described here isolates biologically active forms of aggregated PrP. These preparations may be useful for investigating the structural and chemico-physical properties of infectious and neurotoxic PrP aggregates

Unusual Dengue Virus 3 Epidemic in Nicaragua, 2009

The four dengue virus serotypes (DENV1–4) cause the most prevalent mosquito-borne viral disease affecting humans worldwide. In 2009, Nicaragua experienced the largest dengue epidemic in over a decade, marked by unusual clinical presentation, as observed in two prospective studies of pediatric dengue in Managua. From August 2009–January 2010, 212 dengue cases were confirmed among 396 study participants at the National Pediatric Reference Hospital. In our parallel community-based cohort study, 170 dengue cases were recorded in 2009–10, compared to 13–65 cases in 2004–9. In both studies, significantly more patients experienced “compensated shock” (poor capillary refill plus cold extremities, tachycardia, tachypnea, and/or weak pulse) in 2009–10 than in previous years (42.5% [90/212] vs. 24.7% [82/332] in the hospital study (p<0.001) and 17% [29/170] vs. 2.2% [4/181] in the cohort study (p<0.001). Signs of poor peripheral perfusion presented significantly earlier (1–2 days) in 2009–10 than in previous years according to Kaplan-Meier survival analysis. In the hospital study, 19.8% of subjects were transferred to intensive care, compared to 7.1% in previous years – similar to the cohort study. DENV-3 predominated in 2008–9, 2009–10, and 2010–11, and full-length sequencing revealed no major genetic changes from 2008–9 to 2010–11. In 2008–9 and 2010–11, typical dengue was observed; only in 2009–10 was unusual presentation noted. Multivariate analysis revealed only “2009–10” as a significant risk factor for Dengue Fever with Compensated Shock. Interestingly, circulation of pandemic influenza A-H1N1 2009 in Managua was shifted such that it overlapped with the dengue epidemic. We hypothesize that prior influenza A H1N1 2009 infection may have modulated subsequent DENV infection, and initial results of an ongoing study suggest increased risk of shock among children with anti-H1N1-2009 antibodies. This study demonstrates that parameters other than serotype, viral genomic sequence, immune status, and sequence of serotypes can play a role in modulating dengue disease outcome