Inhibition of in vitro replication of the oyster parasite Perkinsus marinus by the natural iron chelators transferrin, lactoferrin, and desferrioxamine

The mammalian iron-binding proteins transferrin and lactoferrin, the bactericidal peptide lactoferricin B, and the bacterial siderophore desferrioxamine were tested for their ability to inhibit the in vitro replication of the oyster parasite Perkinsus marinus. All three chelators were effective in reducing the parasite proliferation in a dose-dependent manner. Lactoferricin B, a peptide of lactoferrin that exhibits bactericidal properties unrelated to iron chelation, had no inhibitory activity on the parasite. When the chelators were partially or completely saturated with the appropriate iron equivalents, their inhibitory effects on the parasite proliferation were diminished or abolished accordingly, confirming that this activity was related to the chelator's capacity for iron sequestration. Our results indicate that the parasite has a strong requirement for soluble iron and its growth rates are correlated with iron availability. We propose that excess iron accumulation in the host Crassostrea virginica promotes parasite proliferation. P. marinus may avoid oxidative damage that would compromise its intracellular survival by exhaustion the host's intracellular selected iron pools required for superoxide and hydroxyl radical production.     

Enhanced T-cell immunogenicity and protective efficacy of a human immunodeficiency virus type 1 vaccine regimen consisting of consecutive priming with DNA and boosting with recombinant fowlpox virus

The induction of human immunodeficiency virus (HIV)-specific T-cell responses is widely seen as critical to the development of effective immunity to HIV type 1 (HIV-1). Plasmid DNA and recombinant fowlpox virus (rFPV) vaccines are among the most promising safe HIV-1 vaccine candidates. However, the immunity induced by either vaccine alone may be insufficient to provide durable protection against HIV-1 infection. We evaluated a consecutive immunization strategy involving priming with DNA and boosting with rFPV vaccines encoding common HIV-1 antigens. In mice, this approach induced greater HIV-1-specific immunity than either vector alone and protected mice from challenge with a recombinant vaccinia virus expressing HIV-1 antigens. In macaques, a dramatic boosting effect on DNA vaccine-primed HIV-1-specific helper and cytotoxic T-lymphocyte responses, but a decline in HIV-1 antibody titers, was observed following rFPV immunization. The vaccine regimen protected macaques from an intravenous HIV-1 challenge, with the resistance most likely mediated by T-cell responses. These studies suggest a safe strategy for the enhanced generation of T-cell-mediated protective immunity to HIV-1.     

Cytotoxicity of bile in human Hep G2 cells and in primary cultures of rat hepatocytes

There has been increasing interest in the development of a hepatocyte bioreactor for the treatment of acute hepatic failure; however, little is known about the effect of hepatocyte byproducts on the viability of the cells in the bioreactor environment. We investigated the effects of increasing concentrations of bile on the growth and viability of the human hepatoma cell line Hep G2 and on the cytochrome P-450 content and dependent mixed function oxidase (MFO) activities, reduced glutathione (GSH) content, and glutathione S-transferase (GST) activity of primary cultures of rat hepatocytes. Our purpose was to determine whether or not it would be necessary to pretreat the plasma from patients with acute liver failure to remove elevated bile concentrations which might be toxic to the hepatocytes in an artificial liver device. Bile was found to inhibit Hep G2 cell growth at concentrations as low as 0.1% and to decrease viability at concentrations above 0.5%. The cytochrome P-450 and GSH contents and the activities of the MFO system and of GST were decreased in the primary cultures of hepatocytes following 24 h treatment with concentrations of bile at and above 0.5%. The MFO activities associated with different cytochrome P-450 isoenzymes decreased to different extents in the presence of bile with the O-dealkylation of pentoxyresorufin being more labile than that of ethoxyresorufin. Our data indicate that elevated bile concentrations are cytotoxic to liver cells, and it may be necessary to pretreat patient plasma to decrease its bile content to protect the cells during the clinical operation of a hepatocyte bioreactor device.     

Brief assessments of dietary behavior in field settings

Our research team is involved in ongoing research in both worksites and medical office settings. These settings offer great potential for reaching individuals who would not otherwise participate in health promotion, but they also place considerable constraints on assessment time and efforts, especially if one's goal is to attract a high and representative proportion of employees or patients. This paper reports on our experience with measures of dietary behavior in these two settings. We found it problematic to collect detailed assessments such as 4-day food records or comprehensive food frequency/history checklists in worksites or medical office settings using population-based samples. Instead, we recommend and provide data on the utility of a dietary-fat screening instrument, and on the Food Habits Questionnaire (FHQ-Kristal, Shattuck, & Henry, 1990), a brief measure of dietary behaviors associated with high-fat eating patterns. The FHQ, in particular, was found to correlate well with other more costly and time-consuming methods of assessment, to be reliable and responsive to intervention effects, and to provide behavioral targets for intervention. The strengths and limitations of these measures for tailoring intervention and assessing outcomes are discussed.