Acute Toxicity Assays with the Artemia salina Model: Assessment of Variables.

The use of the brine shrimp Artemia salina (Leach) in acute toxicity assays has great potential due to its simplicity, low cost and reproducibility. In the current study, some of the variables that can influence the reliability of the assay in terms of test organism survival, were evaluated as part of its implementation in our laboratory. The quality and type of water used, the buffer components and other parameters (salinity, pH and dissolved oxygen level), were all evaluated for optimisation purposes. DMSO (dimethyl sulphoxide) was used as the test substance in the toxicity assay, to evaluate the concentration limits as a solvent in sample preparation. Regarding the buffer salinity, pH and dissolved oxygen level, we found that a 25% to 30% deviation from the standard values did not affect the survival of the nauplii (the first-instar larval stage) under assay conditions. In summary, we corroborate the potential use of this model for the prediction of the toxic potential of substances, to inform future testing strategies.

A role for CD103 in the retention of CD4+CD25+ Treg and control of Leishmania major infection.

Endogenous regulatory T cells (T(reg)) play a central role in the control of excessive or misdirected immune responses against self or foreign Ags. To date, virtually no data are available on the nature of the molecules and signals involved in the trafficking and retention of T(reg) in tissues where regulation is required. Here, we show that expression of alpha(E)beta(7) integrin is necessary for the homing of T(reg) at site of Leishmania major infection. The vast majority of T(reg) present in the dermis at steady-state conditions or during L. major infection express the alpha(E) chain (CD103) of alpha(E)beta(7). Genetically susceptible BALB/c mice that lack CD103 become resistant to infection, a phenotype that is associated with a poor capacity of T(reg) to be retained in the infected site. Such susceptible phenotype can be restored when T(reg) from wild-type mice were transferred in CD103(-/-) mice. The central role of CD103 in T(reg) retention was further demonstrated by usage of blocking Abs against CD103 and the transfer of T(reg) purified from CD103(-/-) mice. Our results strongly suggest that this molecule is induced and maintained on T(reg) following or just prior to their arrival in tissues. Furthermore, the expression of CD103 and the subsequent retention of T(reg) in tissues is highly regulated by their exposure to Leishmania Ag and the level of activation of the APCs they encounter. Thus, CD103, by controlling T(reg) retention, can contribute to the outcome of chronic infection by Leishmania.

Importance of CD8 T cell-mediated immune response during intracellular parasitic infections and its implications for the development of effective vaccines

Obligatory intracellular parasites such as Plasmodium sp, Trypanosoma cruzi, Toxoplasma gondii and Leishmania sp are responsible for the infection of hundreds of millions of individuals every year. These parasites can deliver antigens to the host cell cytoplasm that are presented through MHC class I molecules to protective CD8 T cells. The in vivo priming conditions of specific CD8 T cells during natural infection are largely unknown and remain as an area that has been poorly explored. The antiparasitic mechanisms mediated by CD8 T cells include both interferon-g-dependent and -independent pathways. The fact that CD8 T cells are potent inhibitors of parasitic development prompted many investigators to explore whether induction of these T cells can be a feasible strategy for the development of effective subunit vaccines against these parasitic diseases. Studies performed on experimental models supported the hypothesis that CD8 T cells induced by recombinant viral vectors or DNA vaccines could serve as the basis for human vaccination. Regimens of immunization consisting of two different vectors (heterologous prime-boost) are much more efficient in terms of expansion of protective CD8 T lymphocytes than immunization with a single vector. The results obtained using experimental models have led to clinical vaccination trials that are currently underway

Importance of CD8 T cell-mediated immune response during intracellular parasitic infections and its implications for the development of effective vaccines.

Obligatory intracellular parasites such as Plasmodium sp, Trypanosoma cruzi, Toxoplasma gondii and Leishmania sp are responsible for the infection of hundreds of millions of individuals every year. These parasites can deliver antigens to the host cell cytoplasm that are presented through MHC class I molecules to protective CD8 T cells. The in vivo priming conditions of specific CD8 T cells during natural infection are largely unknown and remain as an area that has been poorly explored. The antiparasitic mechanisms mediated by CD8 T cells include both interferon-gamma-dependent and -independent pathways. The fact that CD8 T cells are potent inhibitors of parasitic development prompted many investigators to explore whether induction of these T cells can be a feasible strategy for the development of effective subunit vaccines against these parasitic diseases. Studies performed on experimental models supported the hypothesis that CD8 T cells induced by recombinant viral vectors or DNA vaccines could serve as the basis for human vaccination. Regimens of immunization consisting of two different vectors (heterologous prime-boost) are much more efficient in terms of expansion of protective CD8 T lymphocytes than immunization with a single vector. The results obtained using experimental models have led to clinical vaccination trials that are currently underway.