The CDI toxin of Yersinia kristensenii is a novel bacterial member of the RNase A superfamily

Contact-dependent growth inhibition (CDI) is an important mechanism of inter-bacterial competition found in many Gram-negative pathogens. CDI⁺ cells express cell-surface CdiA proteins that bind neighboring bacteria and deliver C-terminal toxin domains (CdiA-CT) to inhibit target-cell growth. CDI⁺ bacteria also produce CdiI immunity proteins, which specifically neutralize cognate CdiA-CT toxins to prevent self-inhibition. Here, we present the crystal structure of the CdiA-CT/CdiI^Ykris complex from Yersinia kristensenii ATCC 33638. CdiA-CT^Ykris adopts the same fold as angiogenin and other RNase A paralogs, but the toxin does not share sequence similarity with these nucleases and lacks the characteristic disulfide bonds of the superfamily. Consistent with the structural homology, CdiA-CT^Ykris has potent RNase activity in vitro and in vivo. Structure-guided mutagenesis reveals that His175, Arg186, Thr276 and Tyr278 contribute to CdiA-CT^Ykris activity, suggesting that these residues participate in substrate binding and/or catalysis. CdiI^Ykris binds directly over the putative active site and likely neutralizes toxicity by blocking access to RNA substrates. Significantly, CdiA-CT^Ykris is the first non-vertebrate protein found to possess the RNase A superfamily fold, and homologs of this toxin are associated with secretion systems in many Gram-negative and Gram-positive bacteria. These observations suggest that RNase A-like toxins are commonly deployed in inter-bacterial competition.

Profiling the Targets of Protective CD8+ T Cell Responses to Infection

T cells are critical effectors of host immunity that target intracellular pathogens, such as the causative agents of HIV, tuberculosis, and malaria. The development of vaccines that induce effective cell-mediated immunity against such pathogens has proved challenging; for tuberculosis and malaria, many of the antigens targeted by protective T cells are not known. Here, we report a novel approach for screening large numbers of antigens as potential targets of T cells. Malaria provides an excellent model to test this antigen discovery platform because T cells are critical mediators of protection following immunization with live sporozoite vaccines and the specific antigen targets are unknown. We generated an adenovirus array by cloning 312 highly expressed pre-erythrocytic Plasmodium yoelii antigens into adenovirus vectors using high-throughput methodologies. The array was screened to identify antigen-specific CD8⁺ T cells induced by a live sporozoite vaccine regimen known to provide high levels of sterile protection mediated by CD8⁺ T cells. We identified 69 antigens that were targeted by CD8⁺ T cells induced by this vaccine regimen. The antigen that recalled the highest frequency of CD8⁺ T cells, PY02605, induced protective responses in mice, demonstrating proof of principle for this approach in identifying antigens for vaccine development.

New gorilla adenovirus vaccine vectors induce potent immune responses and protection in a mouse malaria model

Background

A DNA-human Ad5 (HuAd5) prime-boost malaria vaccine has been shown to protect volunteers against a controlled human malaria infection. The potency of this vaccine, however, appeared to be affected by the presence of pre-existing immunity against the HuAd5 vector. Since HuAd5 seroprevalence is very high in malaria-endemic areas of the world, HuAd5 may not be the most appropriate malaria vaccine vector. This report describes the evaluation of the seroprevalence, immunogenicity and efficacy of three newly identified gorilla adenoviruses, GC44, GC45 and GC46, as potential malaria vaccine vectors.

Results

The seroprevalence of GC44, GC45 and GC46 is very low, and the three vectors are not efficiently neutralized by human sera from Kenya and Ghana, two countries where malaria is endemic. In mice, a single administration of GC44, GC45 and GC46 vectors expressing a murine malaria gene, Plasmodium yoelii circumsporozoite protein (PyCSP), induced robust PyCSP-specific T cell and antibody responses that were at least as high as a comparable HuAd5-PyCSP vector. Efficacy studies in a murine malaria model indicated that a prime-boost regimen with DNA-PyCSP and GC-PyCSP vectors can protect mice against a malaria challenge. Moreover, these studies indicated that a DNA-GC46-PyCSP vaccine regimen was significantly more efficacious than a DNA-HuAd5-PyCSP regimen.

Conclusion

These data suggest that these gorilla-based adenovectors have key performance characteristics for an effective malaria vaccine. The superior performance of GC46 over HuAd5 highlights its potential for clinical development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1911-z) contains supplementary material, which is available to authorized users.

Glucose tolerance and insulin release in hypertensive patients treated with the cardioselective beta-receptor blocking agent metoprolol

Blood glucose and plasma insulin levels were studied under fasting conditions and following an i.v. and an oral glucose load, respectively, in nine males with moderate hypertension before treatment, after one month on placebo and after three months on the cardioselective beta-receptor blocking agent metoprolol. The studies were performed under metabolic ward conditions. The reproducibility of blood glucose and plasma insulin values following an i.v. glucose load was very good. Medication with metoprolol caused no changes in the fasting levels of blood glucose or plasma insulin, nor in the blood glucose response following a glucose load given i.v. or orally. The initial and total integrated insulin response to the i.v. administration of glucose was similar before and during metroprolol. Following oral glucose both the total integrated blood glucose response and the insulin response were unaffected by treatment with metoprolol.

Early community outreach intervention in children with acquired brain injury

Ten patients with acquired brain injury were recruited over an 18 month period in the south-western health care region of Sweden in order to evaluate the costs and effectiveness of a multidisciplinary community outreach intervention programme. An experienced multidisciplinary project team was involved and patients underwent detailed functional, cognitive and motor assessments following initial contact within two weeks of injury, within six weeks of injury and at a 12-month follow-up. An individualized counselling programme was also offered. Of an expected recruitment number of 50 patients (based on epidemiological and population based figures) 10 children were reached, evaluated and followed; eight patients with traumatic brain injury (five severe, two moderate and one mild), and two patients with non-traumatic brain injury (both severe). At follow-up there was a significant improvement in motor function. No significant changes were seen in other areas of functional assessment or on neuropsychological measures although there were mild improvements in communication and behaviour functions. The financial costs per patient in the programme were deemed relatively modest compared with cost estimates of shorter-term in-patient rehabilitation. Time intensive interventions included supporting caregivers and school staff and the direct and indirect patient interventions were shown to enhance support and promote active involvement of local services.

Raised platelet levels in diabetes mellitus complicated with nephropathy

OBJECTIVES

To study if elevated platelet levels are found in early and late diabetic nephropathy.

DESIGN

A retrospective study was performed of platelet count in different subgroups of patients with insulin-dependent diabetes mellitus, including patients with long and short duration of diabetes and with early signs of nephropathy. Patients with severe renal failure subjected to renal transplantation were also included.

RESULTS

The results suggest that raised platelet levels were associated with early signs of diabetic nephropathy and with female gender. Amongst diabetics progressing to uraemia leading to renal transplant, the platelet level was 50% higher than in non-diabetic uraemic patients.

CONCLUSION

It is concluded that raised platelet levels are a common finding in patients with diabetes mellitus complicated by nephropathy.

Glutamate decarboxylase antibodies in non-diabetic pregnancy precedes insulin-dependent diabetes in the mother but not necessarily in the offspring

We studied the risk for diabetes of glutamate decarboxylase (GAD65Ab) and islet cell (ICA) autoantibodies in non-diabetic pregnant mothers and their children. Pregnancy and cord blood sera were collected in 1970-87 from about 35,000 mothers who delivered a child in the city of Malmö, Sweden. A total of 42 mothers were identified in 1988 who, 1-18 years after their pregnancies, had developed either insulin-dependent (n = 22) or non-insulin dependent (n = 20) diabetes mellitus. First, in 123 pregnant mothers selected as controls, 0.8% had GAD65Ab and 0.8% ICA. Second, among the mothers with non-insulin dependent diabetes, 7/20 (35%) had GAD65Ab eight months to 13 years, 10 months before clinical diagnosis. Third, in mothers who later developed insulin-dependent diabetes, 12/22 (55%) had GAD65Ab and 10/22 (45%) had ICA in pregnancies preceding the clinical diagnosis by 13 months to 9 years, 4 months. In 1996, none of the children born to the 42 mothers have developed diabetes. GAD65Ab and ICA in non-diabetic pregnancies may predict insulin-dependent diabetes in the mother but not necessarily in the offspring.

Capillary blood on filter paper for determination of HbA1c by ion exchange chromatography

OBJECTIVE

To facilitate HbA1c determination, we evaluated an HbA1c filter paper system enabling capillary blood sampling at home by the patients.

RESEARCH DESIGN AND METHODS

Capillary blood (two drops) was applied to a filter paper (HbA1c Via Post) and sent to the laboratory where a small disc was punched out on the filter paper. Hemoglobin was eluted from the disc in a buffer containing cysteine to eliminate the interfering glutathione adduct (HbA3) formed during storage. Analysis was performed by ion-exchange chromatography (Mono S, high-performance liquid chromatography), and the eluate was compared with hemolysate of venous blood from 41 patients. The stability of blood impregnated on filter paper was checked at different temperatures over different periods of time.

RESULTS

There was an excellent agreement (r = 0.99) between HbA1c values from capillary blood on filter paper and HbA1c values from venous blood. HbA1c values were constant when stored on filter paper for 5-7 days at 20-21 degrees C (room temperature) or at 4-6 degrees C (refrigerator) for 10 days as well as at -70 degrees C for several months after blood sampling. A new chromatographic-interfering hemoglobin fraction both from venous and capillary samples was identified as free alpha-chain of hemoglobin.

CONCLUSIONS

The HbA1c filter paper system enables capillary blood sampling at home, eliminates the need of vein puncture in children and adults, and provides the diabetologist with an HbA1c value when the patient visits the clinic without a need for a previsit phlebotomy.

Slow elimination of glyburide in NIDDM subjects

OBJECTIVE

To determine the terminal elimination half-life of glyburide in non-insulin-dependent diabetes mellitus (NIDDM) subjects after cessation of long-term treatment.

RESEARCH DESIGN AND METHODS

Ten NIDDM patients (5 of each sex, 36-72 years old, without hepatic or renal disease) taking a median glyburide dose of 14 mg/day, who were to start insulin therapy because of sulfonylurea failure, were studied. Serum glyburide concentrations, measured by a newly developed selective and sensitive liquid chromatographic method, were followed from 10 to 48 h after the last glyburide dose.

RESULTS

Serum glyburide levels declined in three different phases, with a terminal gamma-phase between 18 and 48 h having a mean +/- SD half-life of 15.0 +/- 6.7 h. Two patients had half-lives over 20 h. The half-life values did not correlate with fasting blood glucose, age, body weight, body mass index, or creatinine levels. The latter agrees with the assumption that glyburide is completely eliminated by metabolic transformation. Although longer than previously observed, the current half-life values are in accordance with clinical experience that glyburide is a long-acting sulfonylurea.

CONCLUSIONS

The elimination of glyburide in NIDDM subjects is slower than previously reported. The long half-life adds support to the use of a once-daily dosage of glyburide. It also justifies increased caution when using this sulfonylurea.

Protein intake and glomerular hyperfiltration in insulin--treated diabetics without manifest nephropathy

Protein intake in relation to glomerular filtration rate (GFR) and urinary albumin excretion (UAE) has been studied in 96 insulin-treated diabetic patients, 20-40 years of age and without nephropathy. They had diastolic blood pressure (DBP) not exceeding 90 mmHg and a GFR exceeding -2 SD of the age-related value. They were without medications except for insulin. There were no significant differences in protein intake between diabetic patients with and without hyperfiltration (1.18 +/- 0.26 g/kg/d vs 1.21 +/- 0.42 g/kg/d, p = 0.75) or between diabetic patients with or without increased UAE (1.16 +/- 0.41 g/kg/d vs 1.24 +/- 0.37 g/kg/d, p = 0.37). No relations were found between protein intake and GFR or UAE in the whole sample, but a positive relation was found between UAE and protein intake in patients with increased UAE. Protein intake correlated with UAE in hyperfiltrators who use tobacco (n = 8, r = 0.85, p = 0.01), but not in non-users (n = 11, r = 0.24, p = 0.48). In conclusion our findings give no support for a relation between high protein intake and glomerular hyperfiltration in insulin-treated-diabetic patients. However, in contrast to non-users of tobacco, a positive relation was found between UAE and protein intake in tobacco users with hyperfiltration.

Cigarette smoking and urinary albumin excretion in insulin-treated diabetics without manifest nephropathy

The frequency of microalbuminuria and glomerular hyperfiltration in insulin-treated diabetics without manifest nephropathy was studied in 76 patients, 20-40 years of age and with a diabetes duration not exceeding 20 years. Clinical determinants of urinary albumin excretion (UAE) with regard to smoking were studied further in a sample of male diabetics (n = 49) without manifest nephropathy. All patients had an age-related glomerular filtration rate (GFR) exceeding -2 SD, and their diastolic blood pressure (DBP) did not exceed 90 mmHg. GFR was assessed by 51Cr-EDTA-clearance, and UAE was analysed using an immunochemical method. Diabetic smokers with a long diabetes duration (10-20 years) had a significantly higher UAE (39.5 +/- 2.4 mg 24 h-1 vs. 17.1 +/- 2.4 mg 24 h-1; P = 0.03), a higher mean arterial blood pressure (MAP) (97.9 +/- 7.5 mmHg vs. 91.5 +/- 6.3 mmHg; P = 0.02) and a higher frequency of micro-albuminuria (85.7% vs. 37%; P = 0.028) than non-smoking diabetics. Smokers with a short diabetes duration (0-10 years) had a significantly higher frequency of glomerular hyperfiltration (64% vs. 15%; P = 0.005) than non-smokers. The frequency of microalbuminuria or blood pressure did not differ significantly. In male non-smokers (n = 35) UAE was positively correlated with HbAlc and negatively correlated with age of onset. In male smokers (n = 14) regression analysis showed that UAE was positively correlated only with duration of smoking. We conclude that smoking is associated with two accepted risk factors for nephropathy in insulin-treated diabetics, namely hyperfiltration and microalbuminuria. A positive linear relationship between smoking parameters and UAE in male diabetics also supports the view that smoking may increase the risk of nephropathy development in insulin-treated diabetics.

Cigarette smoking and glomerular filtration rate in insulin-treated diabetics without manifest nephropathy

A sample of 120 insulin-treated diabetics, 20-40 years of age, with a glomerular filtration rate (GFR) exceeding -2 SD of the age-adjusted value and without albuminuria greater than 300 mg 24 h-1, and with a diastolic blood pressure not greater than 90 mmHg, were studied in order to evaluate the possible effect of smoking on glomerular filtration rate. The patients reported their smoking habits, use of oral snuff, use of alcohol, physical exercise and heredity for hypertension in a simple questionnaire. GFR was assessed with 51Cr-EDTA-clearance and glomerular hyperfiltration was defined as a value exceeding +2 SD of the age-adjusted normal value. We found a significantly higher prevalence of glomerular hyperfiltration in smokers than in non-smokers (41% vs. 18%), but no increased prevalence in users of oral snuff. In cigarette smokers a multivariate analysis revealed that GFR was positively related to body mass index (BMI), and negatively related to the number of cigarettes smoked per week and the mean blood pressure. In non-smokers GFR was dependent only on age. We conclude that in insulin-treated diabetics glomerular hyperfiltration is related to smoking, and that the GFR in smoking diabetics is directly dependent on the smoke doses. As glomerular hyperfiltration is regarded as a risk factor for diabetic nephropathy, our findings should be relevant to preventive measures in clinical work.

A prospective study of the immunogenicity of porcine insulin in HLA-typed new insulin-treated diabetics

Fifty-four diabetics were started on insulin therapy with highly purified porcine insulin (Velosulin, Insulatard, Mixtard) and treated for at least 1 yr with blood samples drawn at regular intervals for insulin antibody determinations. In 43 patients the insulin antibody response was correlated with HLA A, B, and DR antigens. Approximately half of the patients formed insulin antibodies within 6 months of treatment, and this incidence remained constant for up till 2 yr. In those patients who developed insulin antibodies a plateau of 12% insulin binding capacity was reached after 9-12 months which remained constant for up till 2 yr. Formation of antibodies to proinsulin and pancreatic polypeptide proved completely avoidable, and no local reactions at the injection sites were observed. There was indication of a positive association between HLA DR4 tissue types and the tendency to immune response to injected insulin (p = 0.07).