Delivery of lethal dsRNAs in insect diets by branched amphiphilic peptide capsules.

Development of new and specific insect pest management methods is critical for overcoming pesticide resistance and collateral off-target killings. Gene silencing by feeding dsRNA to insects shows promise in this area. Here we described the use of a peptide nano-material, branched amphiphilic peptide capsules (BAPCs), that facilitates cellular uptake of dsRNA by insects through feeding. The insect diets included dsRNA with and without complexation with BAPCs. The selected insect species come from two different orders with different feeding mechanisms: Tribolium castaneum and Acyrthosiphon pisum. The gene transcripts tested (BiP and Armet) are part of the unfolded protein response (UPR) and suppressing their translation resulted in lethality. For Acyrthosiphon pisum, ingestion of BiP-dsRNA associated with BAPCs led to the premature death of the aphids (t1/2=4-5days) compared to ingestion of the same amounts of free BiP-dsRNA (t1/2=11-12days). Tribolium castaneum was effectively killed using a combination of BiP-dsRNA and Armet-dsRNA complexed with BAPCs; most dying as larvae or during eclosion (~75%). Feeding dsRNA alone resulted in fewer deaths (~30%). The results show that complexation of dsRNA with BAPCs enhanced the oral delivery of dsRNA over dsRNA alone.

Effects of probiotics and maternal vaccination on Salmonella enteritidis infection in broiler chicks.

The effects of probiotics and maternal vaccination with an inactivated Salmonella Enteritidis (SE) vaccine on day-old chicks challenged with SE were evaluated. A 2 X 3 factorial arrangement was used (with or without probiotics; breeders nonvaccinated, vaccinated intramuscularly, or vaccinated intraperitoneally). Three trials were conducted in isolation cabinets and SE challenge was different between trials. The number of SE organisms per chick and the time interval between housing and introduction of seeder birds (hereafter called challenge) were 1.6 X 10(8) and 1 hr (Trial I), 1.8 X 10(6) and 12 hr (Trial II), and 1.2 X 10(4) and 24 hr (Trial III). SE recovery was assessed in ceca and liver at 3, 5, and 7 days postchallenge, and the number of colony-forming units (CFU) in ceca was evaluated at 5 and 7 days postchallenge. The number of SE (log CFU) in the ceca reduced 0.56 log (from 7.59 to 7.03) and 1.45 log (7.62 to 6.17) because of the treatment with probiotics in Trials II and III, respectively. The greater reduction in Trial III indicates the importance of the early use of probiotics on the prevention of SE infection. Treatment with probiotics resulted in a smaller number of SE-positive livers after 5 days postchallenge on Trial III. Although there was no significant effect of maternal vaccination on the number of SE CFU in the ceca, a significant effect of maternal vaccination on the SE CFU was observed in the liver, but not in the ceca at 5 days after challenge.

Gene delivery and immunomodulatory effects of plasmid DNA associated with Branched Amphiphilic Peptide Capsules.

We recently reported on a new class of branched amphiphilic peptides that associate with double stranded DNA and promote in vitro transfection of eukaryotic cells. In the present study, we tested a different formulation in which plasmid DNA associates with the surface of preformed 20-30nm cationic capsules formed through the self-assembly of the two branched amphiphilic peptides. Under these conditions, the negatively charged DNA interacts with the cationic surface of the Branched Amphiphilic Peptide Capsules (BAPCs) through numerous electrostatic interactions generating peptide-DNA complexes with sizes ranging from 50 to 250nm. The BAPCs-DNA nanoparticles are capable of delivering plasmid DNA of different size into cells in culture, yielding high transfection rates and minimal cytotoxicity. Furthermore, BAPCs were tested for in vivo delivery of a DNA vaccine previously designed to activate immune responses and capable of controlling tumors induced by type 16 human papilloma virus (HPV-16). The BAPCs-DNA nanoparticles enhanced the vaccine-induced antitumor protection and promoted activation of murine dendritic cells without significant toxic effects. These results indicate that branched amphiphilic oligo-peptides nanoparticles represent a new and promising nonviral DNA/gene delivery approach endowing immunomodulatory properties for DNA vaccines.

In vitro synergism of 4-hydroperoxycyclophosphamide and cisplatin: relevance for bone marrow purging.

Autologous bone marrow transplantation with 4-hydroperoxycyclophosphamide (4-HC)-purged bone marrow gives long-term remission in almost half of relapsed acute nonlymphocytic leukemia and non-Hodgkin's lymphoma patients, but relapse of disease is the main cause of failure, suggesting ineffective purging in some cases. Cisplatin (CP) has activity against a variety of human tumors and is not commonly used for initial therapy of leukemia and lymphoma. Using established human leukemia cell lines, combinations of 4-HC and CP were investigated as a potential regimen for improving the ex vivo removal of leukemia cells from bone marrow. The cell lines (K-562 and Raji) were incubated for 1 (4-HC) or 4 h (CP), washed, and assayed for inhibition of colony formation in semisolid media. In both cell lines, CP (4h) was more potent than 4-HC (1 h). Combinations of the drugs in various molar ratios were studied after the cells were sequentially incubated with 4-HC and CP. The effects of the drugs were analyzed using the multiple drug-effect analysis of Chou and Talalay. Analysis of data on in vitro inhibition of colony formation suggested that all combinations studied were synergistic in both cell lines, with the greatest synergism being found in the Raji cell line. In addition, for K-562 cells we could detect at least a 4.6 log reduction in cloning with the CP:4-HC combination (1:10 molar ratio). We conclude that CP is a potential candidate in drug combinations for ex vivo bone marrow purging because of its high potency against human leukemia cell lines, its synergistic activity in combination with 4-HC, and its ability to reduce a high tumor burden when combined with 4-HC.

Analysis of pure and mixed murine mast cell colonies.

Mast cells have been proposed to originate from diverse sources, including connective tissues, macrophages, T lymphocytes, and hemopoietic cells. Evidence for a hemopoietic origin of mast cells includes the presence of mast cell precursors in spleen colonies and the presence of mast cells in hemopoietic colonies in culture. Here we report a detailed analysis of mouse spleen mixed hemopoietic colonies containing mast cells. All of the colonies in cultures plated at low cell densities were individually removed for analysis by May-Grunwald-Giemsa staining on day 15 of culture. Examination of five dishes which contained a total of 82 colonies showed 16 pure mast cell colonies and 36 mixed mast cell colonies. Sixteen different combinations of cell types were seen and were not distinguishable from each other in situ. The most diverse type of mixed colony contained macrophages (m), neutrophils (n), eosinophils (e), mast cells (Mast), megakaryocytes (M), erythroid cells (E), and blast cells. The clonal origin of mixed mast cell colonies was established by the replating of single cells obtained from blast cell colonies. Individual cells were removed with a micromanipulator, replated, and allowed to grow for 15 days. Cytospin preparations of 10 such colonies showed diverse combinations of cell lineages which were seen in the different types of mixed mast cell colonies described above. Replating studies of mixed mast cell colonies were carried out and a high incidence of replating was seen. Approximately one half of these colonies formed only mast cell colonies upon replating. Further studies showed that pure mast cell colonies could be serially replated four to five times. The replating efficiency of cells in the primary mast cell colonies varied over a wide range (2.5-44%) with an average replating efficiency of 13%. The data also revealed that cells containing metachromatic granules possess significant proliferative capacity. From these studies of pure and mixed mast cell colonies, we concluded that mast cells are in wide variety of types of mixed colonies and that the in situ identification of mixed colonies is unreliable, that mast cells are derived from pluripotent hemopoietic stem cells, and that mast cells with metachromatic granules can have a high proliferating ability.

Combinations of 4-hydroperoxycyclophosphamide (4-HC) and cisplatin for bone marrow purging in autologous marrow transplantation: an update.

We are studying the usefulness of combinations of 4-HC and cisplatin as a potential purging regimen for autologous bone marrow transplantation. In all of our studies, in vitro cytotoxicity was determined by clonogenic assay, and drug interaction was quantitated using the multiple drug-effect analysis method. The cells were incubated for one hour (4-HC) and/or 4 hours (cisplatin). We found that the drugs in combination had cytotoxic synergism against human leukemia cell lines (K-562 and Raji). The synergism was sequence-dependent (cells must be exposed to 4-HC first), was present at various molar ratios of the drugs, and most pronounced at high levels of cell kill. We also found that the drugs had cytotoxic synergism against normal human marrow progenitors (CFU-GM). However, the leukemic cells were approximately 55 times more sensitive to the combination than CFU-GM. In a murine system, the drugs were synergistic against L1210 leukemia cells and normal murine CFU-GM, but L1210 cells were at least 130 times more sensitive to the combination than CFU-GM. To determine the ability of L1210 cells to grow in vivo after exposure to the drugs, BDF1 mice were injected with 2 x 10(4) cells which had been incubated with 4-HC and/or cisplatin. The survival time of untreated controls was 13 +/- 2.8 days. For treated groups, the cure rates after 50 days of observation were 33% (4-HC, 40 uM), 0% (cisplatin, 8 uM), and 100% (4-HC + cisplatin). Finally, at concentrations resulting in equivalent toxicity to marrow CFU-GM, cisplatin seemed to be more toxic to murine spleen blast colony forming cells (CFC-BC) than 4-HC. The drugs in combination appeared to have at least additive toxicities against CFC-BC.