Preclinical immunogenicity study of trivalent meningococcal AWX-OMV vaccines for the African meningitis belt.

In the recent decade, epidemic meningitis in the African meningitis belt has mostly been caused by Neisseria meningitidis of serogroups A, W and X (MenA, MenW and MenX, respectively). There is at present no licensed vaccine available to prevent MenX meningococcal disease. To explore a trivalent MenAWX vaccine concept, we have studied the immunogenicity in mice of MenX outer membrane vesicles (X-OMV) or MenX polysaccharide (X-PS) when combined with a bivalent A-OMV and W-OMV (AW-OMV) vaccine previously shown to be highly immunogenic in mice. The vaccine antigens were produced from three representative wild type strains of MenA (ST-7), MenW (ST-11) and MenX (ST-751) isolated from patients in the African meningitis belt. Groups of mice were immunized with two doses of X-OMV or X-PS combined with the AW-OMV vaccine or as individual components. All vaccine preparations were adsorbed to Al(OH)3. Sera from immunized mice were tested by ELISA and immunoblotting. Functional antibody responses were measured as serum bactericidal activity (SBA) and opsonophagocytic activity (OPA). Immunization of mice with X-OMV, alone or in combination with AW-OMV induced high levels of anti-X OMV IgG. Moreover, X-OMV alone or in combination with the AW-OMV vaccine induced high SBA and OPA titers against the MenX target strain. X-PS alone was not immunogenic in mice; however, addition of the AW-OMV vaccine to X-PS increased the immunogenicity of X-PS. Both AWX vaccine formulations induced high levels of IgG against A- and W-OMV and high SBA titers against the MenA and MenW vaccine strains. These results suggest that a trivalent AWX vaccine, either as a combination of OMV or OMV with X-PS, could potentially prevent the majority of meningococcal disease in the meningitis belt.

Preclinical immunogenicity and functional activity studies of an A+W meningococcal outer membrane vesicle (OMV) vaccine and comparisons with existing meningococcal conjugate- and polysaccharide vaccines.

Meningococci of serogroups A and W (MenA and MenW) are the main causes of epidemic bacterial meningitis outbreaks in sub-Saharan Africa. In this study we prepared a detergent extracted outer membrane vesicle (dOMV) vaccine from representative African MenA and MenW strains, and compared the immunogenicity of this vaccine with existing meningococcal conjugate and polysaccharide (PS) vaccines in mice. NMRI mice were immunized with preclinical batches of the A+W dOMV vaccine, or with commercially available vaccines; a MenA conjugate vaccine (MenAfriVac(®), Serum Institute of India), ACYW conjugate vaccine (Menveo(®), Novartis) or ACYW PS vaccine (Mencevax(®), GlaxoSmithKline). The mice received 2 doses of 1/10 or 1/50 of a human dose with a three week interval. Immune responses were tested in ELISA, serum bactericidal activity (SBA) and opsonophagocytic activity (OPA) assays. High levels of IgG antibodies against both A and W dOMV were detected in mice receiving the A+W dOMV vaccine. High SBA titers against both MenA and MenW vaccine strains were detected after only one dose of the A+W dOMV vaccine, and the titers were further increased after the second dose. The SBA and OPA titers in mice immunized with dOMV vaccine were significantly higher than in mice immunized with the ACYW-conjugate vaccine or the PS vaccine. Furthermore, the A+W dOMV vaccine was shown to induce SBA and OPA titers against MenA of the same magnitude as the titers induced by the A-conjugate vaccine. In conclusion, the A+W dOMV vaccine induced high levels of functional antibodies to both MenA and MenW strains, levels that were shown to be higher or equal to the levels induced by licensed meningococcal vaccines. Thus, an A+W dOMV vaccine could potentially serve as an alternative or a supplement to existing conjugate and PS vaccines in the African meningitis belt.

Influence of season and diet on liver and kidney content of essential elements and heavy metals in Svalbard reindeer.

Samples of liver (n = 78) and kidney (n = 60) from Svalbard reindeer (Rangifer tarandus platyrhynchus Vrolik) collected at four different seasons in Svalbard were analysed for their content of Cd, Pb, Cu, Zn, Mn, and Se. The study shows that when animals are exposed to large seasonal variations in both the quality and quantity of food, it is crucial to relate element concentrations to the physiological condition of the animal, e.g., to look at seasonal fluctuations in the total element content of the different organs.

Supplementation with wheat selenium induces a dose-dependent response in serum and urine of a Se-replete population.

In spite of a rather modest dietary intake of selenium (80 micrograms/10 MJ), Norwegian serum Se levels are among the highest in Europe. As part of an ongoing study of Se bioavailability, effects of different doses of wheat Se were investigated in eighteen healthy, Norwegian women. The participants were given Se-rich bread providing 100, 200 and 300 micrograms Se daily for 6 weeks. About 50% of the Se intake was excreted in the urine by week 6, compared with 67% before the intervention started. Serum Se increased by 20, 37 and 53 micrograms/l respectively, in the three group (P less than 0.001). The blood response and renal clearance results compare well with data obtained from less Se-replete populations, and support the hypothesis that selenomethionine from the diet is incorporated into a non-specific amino acid pool. Our study indicates that the intake of wheat Se is the main determinant of blood Se levels in Norway.

The form of selenium determines the response to supplementation in a selenium replete population.

In an ongoing study of selenium bioavailability, effects of supplementation with organic and inorganic forms of selenium were investigated in healthy, Norwegian women, aged 23-50 years. In phase I of the study, 58 women received 200 micrograms selenium per day either as selenite or selenium-rich pea flour for 3 months. The selenium tablets were taken together with placebo or ascorbic acid in a double blind design. Initial blood and serum selenium concentrations were 153 +/- 15 micrograms/l and 117 +/- 12 micrograms/l, respectively. These are average values for Norwegians. Indications of increased blood levels were seen in all groups, but the rise reached significance only for the subgroup receiving selenite and ascorbic acid, 14 micrograms/l, P less than 0.05. On the other hand, selenium analysis of 72-h urine samples confirmed that at an average 50 per cent of the selenium supplements had been absorbed. In phase II of the study, 28 of the participants continued for another 5 weeks, still on 200 micrograms Se per day, but this time consuming commercially available preparations. Of four preparations that were tested, two consisted of yeast Se. Only one of these produced a significant rise in blood and serum selenium levels, 60 and 55 micrograms/l respectively. Blood glutathione peroxidase values were not affected by any supplementation. The study demonstrates that different forms of organic selenium elicit widely different responses when administered to a relatively selenium-replete population, and that the explanation for this must be sought at the metabolic level.

Chemical and morphological studies of liver from eider (Somateria mollissima) in Svalbard with special reference to the distribution of copper.

Specimens of male and brooding female eider (Somateria mollissima) were collected in Svalbard. Chemical analyses revealed hepatic copper concentrations ranging from 20 to 1050 micrograms per g wet weight. This is in agreement with previous results. The selenium, zinc and cadmium values were equal to or slightly higher than previously recorded. It is suggested that the wide variation in copper concentration is a result of differences in intake of copper-containing food among the birds. High selenium intake may enhance copper accumulation. Starvation influences the concentration of zinc and also copper. Zinc concentrations were significantly higher in females. This may be secondary to starvation. The percentage of copper recovered among the soluble proteins was inversely related to the copper content. The distribution of the soluble proteins reflects a normal copper metabolism. Microscopic studies showed prominent dark granules, positive with the rubeanic acid test for copper, confined to hepatocytes. By electron microscopy, the granules appeared as large irregular, electron-dense bodies that, by X-ray microanalysis, were found to contain copper. There were no signs of liver injuries such as necrosis and fibrosis. Apparently, the eider has evolved a high capacity for copper storage.

Selenium concentrations in the human thyroid gland.

Recently, we found that prediagnostic serum selenium concentration was significantly lower for cases developing thyroid cancer (n = 43) than for controls. We assumed that redistribution of serum selenium into the affected tissue took place in the prediagnostic period. The present study was carried out to determine the physiological concentration of selenium in the thyroid, since very few data are available in the literature. The concentrations of selenium in the thyroid (n = 45) and liver samples from Norwegians who had died because of acute illness or accidents were determined by hydride generation atomic absorption spectrometry. The mean selenium concentration was found to be 0.72 +/- 0.44 microgram/g in the thyroid and 0.45 +/- 0.11 microgram/g in the liver tissue. The surprisingly high concentration of selenium in apparently normal thyroids indicates that selenium has important functions in this organ. The remarkably broad range, together with the observation that no significant correlation exists between thyroid and liver concentrations, suggest that factors other than the selenium status are important determinants for the selenium concentration in the thyroid gland. This observation is consistent with our hypothesis that in carcinogenesis, prediagnostic processes influence the serum-/thyroid-ratio of selenium.

Hypoxia and deposition of iron in liver and spleen of mice given iron supplement.

Iron-related changes in peripheral blood and variations in liver and spleen iron concentrations during alternating periods of hypoxia and normoxia have been investigated in iron-supplemented mice by chemical and histological methods. During hypoxia, packed cell volume increased from 40 to 70%. The iron content of the liver increased during the first hypoxic and the following normoxic period, while an increase in spleen iron started after the first hypoxic period. Transferrin saturation fell from about 60 to about 20% during hypoxia and normalized during normoxia. Hypoxia together with iron supplementation led to increased erythropoiesis and parenchymal iron deposition in liver. The reduction in transferrin saturation may be attributed to the effective uptake of iron by hepatocytes simultaneously with the erythropoiesis. The spleen seemed to participate in the production of red cells during hypoxia. The increase in spleen iron during normoxia can be explained by the role of the spleen in the catabolism of excess erythrocytes.

Selenium deficiency and cardiac electrophysiological and mechanical function in the rat.

Earlier studies have shown that selenium and vitamin E are important in maintaining normal cardiac function. The present study was designed to test the effect of sole selenium deficiency on electrophysiological and mechanical characteristics of the rat heart. Male weanling rats were fed a standardized vitamin E adequate but selenium deficient diet, or a control diet. Deficiency of selenium was verified by direct (tissue selenium analyses) and indirect (glutathione-peroxidase tissue analyses) methods. In vivo electrocardiographic recordings as well as in vitro electrophysiological and mechanical recordings did not reveal abnormalities in any of the two groups. In conclusion, earlier studies have shown that the combined deficiency of selenium and vitamin E leads to abnormal cardiac function. Selenium deficiency alone, however, does not appear to significantly affect cardiac function in the rat.

The selenium-deficient rat heart with special reference to tolerance against enzymatically generated oxygen radicals.

The tolerance against two different levels of enzymatically generated oxygen radicals was studied in isolated Langendorff-perfused hearts from selenium (Se)-deficient and control rats. The glutathione peroxidase activity of the Se-deficient hearts was less than 5% of that of the controls. Examination of the ultrastructure was made after random sampling using morphometric methods. Selenium-deficient hearts demonstrated some areas with myocytes with intracellular oedema. Oxygen radicals (hydrogen peroxide and superoxide) were generated by adding xanthine oxidase for 12 min (high dose: 25 U/l; low dose: 12.5 U/l) and hypoxanthine to the buffer of isolated Langendorff-perfused rat hearts. Left ventricle-developed pressure (LVDP) and high-energy phosphates (ATP and CP) were measured. After the low dose of oxygen radicals, LVDP was reduced to 32.7 +/- 6.5% (mean +/- SEM) of initial values in the Se-deficient group, but only to 58.3 +/- 8.4% in the control group (p less than 0.05). After the high dose, LVDP decreased abruptly to zero in both groups. However, ATP content was significantly (p less than 0.05) lower in Se-deficient than in control hearts. Perfusion with oxygen radicals (low dose) resulted in the appearance of mitochondrial damage in both groups, but intracellular oedema was still present only in the Se-deficient hearts. It is concluded that protection against oxygen radicals was reduced in Se-deficient hearts. This was probably due to loss of myocardial glutathione peroxidase activity.

[Mercury and selenium in wild mink (Mustela vision) from Norway]. / Kvikksølv og selen i villmink (Mustela vision) fra Norge.

Levels of mercury, methylmercuri and selenium were determined in liver samples from wild mink (Mustela vision) caught in the Norwegian countries of Rogaland (38 samples), Sogn og Fjordane (15 samples) and Hedmark (18 samples). The average mercury levels from these counties were 2.6, 3.1 and 2.1 micrograms Hg/g wet weight, respectively. No significant differences in mercury levels were found. The methyl mercury levels (MeHg) were determined in 30 samples. A very strong positive correlation between total mercury (Hg) and methyl mercury (r = 0.91, P less than 0.001) was found. The average methyl mercury level was 35 per cent of total mercury. This indicates that wild mink has the ability to demethylate mercury. The selenium levels were determined in 35 samples. A strong positive correlation between the levels of total mercury and selenium (r = 0.87, P less than 0.001) was found. There was no correlation between age or nutritional condition and mercury level. In the present study mink was examined to see of it could be recommended as an indicator species for monitoring the local environment for mercury contamination. No definite answer to this question could be found. The study did reveal, however, that in all the counties studied there are individuals that are considerably contaminated with mercury.

Trace elements in grass, cattle liver and sheep liver from districts surrounding Karatina, Kenya. I. Selenium.

Samples of grass, cattle and sheep livers from the districts surrounding Karatina, Kenya, were analysed for their contents of selenium. The following mean values were found: Grass (n = 31): 0.19 +/- 0.17 mg Se/kg on dry matter basis, cattle liver (n = 96): 0.31 +/- 0.10 mg Se/ kg on wet weight, and sheep liver (n = 93): 0.55 +/- 0.25 mg Se/kg on wet weight. It is concluded that selenium deficiency is unlikely to occur in the districts included in this investigation.