Members of the Family Bufonidae, true toads, are famous for their endogenously synthesized cardioactive steroids that serve as defensive toxins. Evolution of resistance to these toxins is not understood. We sequenced a key region of the toxin's binding site in the Na + /K + ATPase for relevant taxa representing Hyloidea (including bufonids), Ranoidea and Archaeobatrachia and tested for positive selection in a phylogenetic context. Bufonidae were distinct from other Hyloidea at 4–6 of 12 sites and, with one exception, had a homologous amino acid sequence. Melanophryniscus stelzneri had a distinct sequence, consistent with other independent evidence for a differentiated toxin. Tests within Bufonidae detected positive selection within the binding region, providing, to our knowledge, the first evidence of this type for positive selection within Amphibia. There was no evidence for positive selection on Bufonidae or M. stelzneri lineages. Sequence change in Leptodactylus ocellatus , a leptodactylid predator of Bufonidae, provides a molecular basis for predator resistance possibly associated with gene duplication.

The marine toad Bufo marinus is native to northern South America, parts of Central America and Southern Texas. It was deliberately introduced into Australia's tropical north-east in 1935 in an unsuccessful attempt to control the cane beetle, a damaging insect pest of sugarcane crops. The toads quickly established in the new environment and began to spread. Today, they inhabit most of the Australian tropics and sub-tropics and have reached Western Australia. Models predict that global warming will enable the toads to extend their range further south. They cause severe environmental impacts, as all life stages of B. marinus contain bufadienolides, alkaloid substances toxic to vertebrates, resulting in death of the predators ingesting it. The continental scale of this biological invasion in combination with the remoteness of the areas affected, poses a specific set of challenges to potential control approaches for cane toads. This review covers different biocontrol strategies pursued over the past 8 years, with particular focus on an immunological approach aiming at the disruption of toad metamorphosis. So far, research efforts have failed to produce a tool for large-scale reduction of toad populations. Considerations of future research priorities and efforts are also discussed.

Interferon gamma (IFN-g) and interleukin-4 (IL-4) are not only generated during cell-mediated immunity (CMI) and humoral immunity (HI), but are also generated by innate immune cells in response to pathogenic factors. How these cytokines differentially effect the development of dendritic cell (DC)-associated immunoregulatory properties from progenitor cells during innate immunity is unresolved. To address this we have utilized a homogeneous DC progenitor-like cell line, MTHC-D2, as a model to examine cytokine-induced maturation of DCs. By 6 h IFN-g induced genes that are important for antiviral activity and development of CMI, whereas IL-4 induced genes involved in cellular adhesion, uptake of extracellular antigen, suppression of cytotoxic T-cell responses, and that repair the extracellular matrix. By 48 h the cytokine stimulus had induced many properties characteristic of immature DCs; however, these were differentially effected by IFN-g and IL-4. IFN-g induced the greatest levels of costimulatory/ activation marker expression, and the highest levels of T-cell proliferation, whereas IL-4 induced the greatest levels of phagocytic activity. Stimulation of the cells with CD40 Ab enhanced the levels of costimulatory marker expression and T-cell stimulatory capacity of cells exposed to IFN-g, but had little effect on cells exposed to IL-4 in the absence of IFN-g.

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A bstract: Marine toads, Bufo marinus, also known as cane toads, were introduced into Australia in 1935 as a biological control agent for native beetles in sugarcane plantations. They were unsuccessful in controlling the beetles and have since become a pest in their own right. They now rank as one of Australia's most serious invasive vertebrate species. We are seeking a means to control the marine toad population and have established a marine toad colony to provide a continuous supply of various life stages to aid our research. We describe here the establishment and maintenance of a breeding colony of Bufo marinus.

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BackgroundThe cane toad, Bufo (Chaunus) marinus, is one of the most notorious vertebrate pests introduced into Australia over the last 200 years and, so far, efforts to identify a naturally occurring B. marinus-specific pathogen for use as a biological control agent have been unsuccessful. We explored an alternative approach that entailed genetically modifying a pathogen with broad host specificity so that it no longer caused disease, but carried a gene to disrupt the cane toad life cycle in a species specific manner.Methodology/Principal FindingsThe adult beta globin gene was selected as the model gene for proof of concept of autoimmunity as a biocontrol method for cane toads. A previous report showed injection of bullfrog tadpoles with adult beta globin resulted in an alteration in the form of beta globin expressed in metamorphs as well as reduced survival. In B. marinus we established for the first time that the switch from tadpole to adult globin exists. The effect of injecting B. marinus tadpoles with purified recombinant adult globin protein was then assessed using behavioural (swim speed in tadpoles and jump length in metamorphs), developmental (time to metamorphosis, weight and length at various developmental stages, protein profile of adult globin) and genetic (adult globin mRNA levels) measures. However, we were unable to detect any differences between treated and control animals. Further, globin delivery using Bohle iridovirus, an Australian ranavirus isolate belonging to the Iridovirus family, did not reduce the survival of metamorphs or alter the form of beta globin expressed in metamorphs.Conclusions/SignificanceWhile we were able to show for the first time that the switch from tadpole to adult globin does occur in B. marinus, we were not able to induce autoimmunity and disrupt metamorphosis. The short development time of B. marinus tadpoles may preclude this approach.

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