Alternative leech vectors for frog and turtle trypanosomes.

Trypanosoma pipientis infections were achieved by exposing laboratory-raised bullfrog tadpoles (Rana catesbeiana) to the leech Desserobdella picta that had fed on infected frogs. Likewise, a laboratory-raised snapping turtle (Chelydra serpentina) was infected with Trypanosoma chrysemydis following exposure to infected Placobdella ornata. Transmission of the trypanosomes by these leeches constitutes new vector records for the parasites. The biology of D. picta and P. ornata suggests that they are more important in transmitting these flagellates than the species of leech previously reported as vectors.     

DNA breaks as triggers for antigenic variation in African trypanosomes

The DNA repair machinery has been co-opted for antigenic variation in African trypanosomes. New work directly demonstrates that a double-strand break initiates a switch in the expressed variant surface coat.     

Gene conversion as a mechanism for antigenic variation in trypanosomes

Expression of the gene coding for the trypanosome AnTat 1.1 surface antigen is linked to the duplicative transposition of a basic copy (BC) of this gene to an expression site. In two trypanosome clones successively derived from AnTat 1.1 (AnTat 1.10 and AnTat 1.1B) we found evidence that gene conversions are involved in the transformation of the AnTat 1.1 transposed element into the two new surface antigen coding sequences. Although the three resultant mRNAs--AnTat 1.1, 1.10, and 1.1B--are different, they still share large homologies. Two of them, AnTat 1.1 and 1.1B, code for surface coats that are indistinguishable by conventional serological techniques, whereas AnTat 1.10 has been found different by the same methods. The three genomic rearrangements involve two of the five members of the AnTat 1.1 gene family. These two members are both located in unstable telomeric regions similar to the expression site, each in a different orientation with respect to the DNA terminus. We have concluded that the duplicative transposition is achieved by a gene conversion that may affect variable lengths of the same silent genes, and that different members of the same surface antigen gene family can contribute to the diversification of the antigen repertoire.     

Edible insects as minilivestock

Many species of insects (probably 1000 or more) have served as traditional foods among indigenous peoples, especially in warmer climes, and the insects have played an important role in the history of human nutrition. As part of the hunter-gatherer style of life, the main criteria for selection of these traditional species appears to be medium-to-large size and easy availability, i.e., abundance, as noted by Dufour and others. Thus it is not surprising that many insects considered as crop pests in modern agriculture have served as important food sources. Locusts and grasshoppers, which often occur in swarms, are good examples, and these insects have been included in the diets of almost every culture with any history of food-insect use.     

Animals as reservoir hosts of human trypanosomes

Present knowledge on reservoir hosts of Trypanosoma rhodesiense, T. gambiense and T. brucei in Africa and T. cruzi and T. rangeli in America and experimental transmission studies of T. cruzi in mammalian hosts and in lizards is discussed. The difficulty in differentiating the African species of human trypanosomes, which appear not to be host specific, is a major obstacle to epizootiological studies.     

Aquatic insects as a vector for Mycobacterium ulcerans

Mycobacterium ulcerans is an emerging environmental pathogen which causes chronic skin ulcers (i.e., Buruli ulcer) in otherwise healthy humans living in tropical countries, particularly those in Africa. In spite of epidemiological and PCR data linking M. ulcerans to water, the mode of transmission of this organism remains elusive. To determine the role of aquatic insects in the transmission of M. ulcerans, we have set up an experimental model with aquariums that mimic aquatic microenvironments. We report that M. ulcerans may be transmitted to laboratory mice by the bite of aquatic bugs (Naucoridae) that are infected with this organism. In addition, M. ulcerans appears to be localized exclusively within salivary glands of these insects, where it can both survive and multiply without causing any observable damage in the insect tissues. Subsequently, we isolated M. ulcerans from wild aquatic insects collected from a zone in the Daloa region of Ivory Coast where Buruli ulcer is endemic. Taken together, these results point to aquatic insects as a possible vector of M. ulcerans.     

Bacteria as vectors for gene therapy of cancer

Anti-cancer therapy faces major challenges, particularly in terms of specificity of treatment. The ideal therapy would eradicate tumor cells selectively with minimum side effects on normal tissue. Gene or cell therapies have emerged as realistic prospects for the treatment of cancer, and involve the delivery of genetic information to a tumor to facilitate the production of therapeutic proteins. However, there is still much to be done before an efficient and safe gene medicine is achieved, primarily developing the means of targeting genes to tumors safely and efficiently. An emerging family of vectors involves bacteria of various genera. It has been shown that bacteria are naturally capable of homing to tumors when systemically administered resulting in high levels of replication locally. Furthermore, invasive species can deliver heterologous genes intra-cellularly for tumor cell expression. Here, we review the use of bacteria as vehicles for gene therapy of cancer, detailing the mechanisms of action and successes at preclinical and clinical levels.     

Novel self-assembling conjugates as vectors for agrochemical delivery

Background

Modern agricultural practises rely on surfactant-based spray applications to eliminate weeds in crops. The wide spread and indiscriminate use of surfactants may result in a number of deleterious effects that are not limited to impacts on the crop and surrounding farm eco-system but include effects on human health. To provide a safer alternative to the use of surfactant-based formulations, we have synthesised a novel, self-assembling herbicide conjugate for the delivery of a broad leaf herbicide, picloram.

Results

The synthesized self-assembling amphiphile–picloram (SAP) conjugate has three extending arms: a lipophilic lauryl chain, a hydrophilic polyethylene glycol chain and the amphiphobic agrochemical active picloram. We propose that the SAP conjugate maintains its colloidal stability by quickly transitioning between micellar and inverse micellar phases in hydrophilic and lipophilic environments respectively. The SAP conjugate provides the advantage of a phase structure that enables enhanced interaction with the hydrophobic epicuticular wax surface of the leaf. We have investigated the herbicidal efficiency of the SAP conjugate compared against that of commercial picloram formulations using the model plant Arabidopsis thaliana and found that when tested at agriculturally relevant doses between 0.58 and 11.70 mM a dose-dependent herbicidal effect with comparable kill rates was evident.

Conclusion

Though self-assembling drug carriers are not new to the pharmaceutical industry their use for the delivery of agrochemicals shows great promise but is largely unexplored. We have shown that SAP may be used as an alternative to current surfactant-based agrochemical formulations and has the potential to shift present practises towards a more sustainable approach.

     

Protein kinases as drug targets in trypanosomes and Leishmania

Protein kinases represent promising drug targets for a number of human and animal diseases. The recent completion of the sequenced genomes of three human-infective trypanosomatid protozoa, Leishmania major, Trypanosoma brucei and Trypanosoma cruzi, has allowed the kinome for each parasite to be defined as 179, 156 and 171 eukaryotic protein kinases respectively, that is about one third of the human complement. The analysis revealed that the trypanosomatids lack members of the receptor-linked or cytosolic tyrosine kinase families, but have an abundance of STE and CMGC family protein kinases likely to be involved in regulating cell cycle control, differentiation and response to stress during their complex life-cycles. In this review, we examine the prospects for exploiting differences between parasite and mammalian protein kinases to develop novel anti-parasitic chemotherapeutic agents.     

Active military training areas as refugia for disturbance-dependent endangered insects

Oedipoda caerulescens (blue-winged grasshopper) and Cicindela hybrida (northern dune tiger beetle) are protected insects in Germany and elsewhere. They are known to occur on sparsely vegetated, sandy soil. Populations of the two insects were evaluated in relation to physical soil disturbance on four military training areas in Germany to determine if the military disturbance regime occurring there is conducive to the survival of the species and to provide insight into the nature of the disturbance that may be necessary as conservationists seek ways to maintain, establish or re-establish suitable habitat. Adults of O. caerulescens exhibited statistically significant preference for areas with between 60% and 100% surface disturbance, corresponding to 50–70% plant cover, depending on the location. C. hybrida adults preferentially occupied areas with >40% disturbance resulting in an average of 61% plant cover. The results confirm suggestions that both species are disturbance-dependent. Military training areas represent some of the last, large remnants of sparse, dry, sandy grasslands in Europe. The nature of land-based military training creates suitable habitat patches as well as habitat connectivity needed for the maintenance of metapopulations. As a result, military training areas represent some of the last remaining vestiges of a habitat and disturbance regime that are highly favored by O. caerulescens and C. hybrida and other species with similar habitat requirements.     

Adenoviruses as vectors for delivering vaccines to mucosal surfaces

Immunization of mucosal surfaces has become an attractive route of vaccine delivery because of its ability to induce mucosal immunity. Although various methods of inducing mucosal immunity are being developed, our laboratory has focused on developing adenoviruses as replication-competent and replication-incompetent vectors. The present report will summarize our progress in sequencing the entire bovine adenovirus-3 genome and identifying regions which can be deleted and subsequently used as insertion sites for foreign genes in developing recombinant viral vaccines. Using these recombinant viruses, we demonstrated the 'proof-of-principle' in developing mucosal immunity and, more importantly, inducing protection against bovine herpes virus in a natural host-cattle. Finally, we demonstrated that immunity and protection occurred even in animals that had pre-existing antibodies to the vector.     

Plant and insect cuticular lipids serve as behavioral cues for insects

The roles of plant and insect cuticular lipids in insect and plant interactions are reviewed. Emphasis is given to the influence that the host plant and the surface lipids of the host plant have upon insect herbivores and the predators and parasitoids of these herbivores. Variations in cuticular lipids of herbivorous insects are dependent upon the host plant, and these variations may affect the behavior of predators and parasitoids. The cuticular lipids of species which interact on multiple trophic levels are compared. Similarities were found between the hydrocarbons of herbivorous insects, their host plants, and their predators or parasitoids.     

RNA viruses as vectors for the expression of heterologous proteins

RNA viruses comprise a wide variety of infectious agents, some of which are the cause of disease in humans, animals, and plants. Recombinant DNA technology is now making it feasible to modify these genomes and engineer them to express heterologous proteins. Several different schemes are being employed that depend on the genome organization of the virus and on the strategy of replication of the particular virus. Several different examples are illustrated and potential uses as well as possible problems are discussed. In the future reverse genetics may convert some of these viruses from agents of disease to agents of cure.