An Overview of Peripheral Blood Mononuclear Cells as a Model for Immunological Research of Toxoplasma gondii and Other Apicomplexan Parasites.

In biology, models are experimental systems meant to recreate aspects of diseases or human tissue with the goal of generating inferences and approximations that can contribute to the resolution of specific biological problems. Although there are many models for studying intracellular parasites, their data have produced critical contradictions, especially in immunological assays. Peripheral blood mononuclear cells (PBMCs) represent an attractive tissue source in pharmacogenomics and in molecular and immunologic studies, as these cells are easily collected from patients and can serve as sentinel tissue for monitoring physiological perturbations due to disease. However, these cells are a very sensitive model due to variables such as temperature, type of stimulus and time of collection as part of posterior processes. PBMCs have been used to study Toxoplasma gondii and other apicomplexan parasites. For instance, this model is frequently used in new therapies or vaccines that use peptides or recombinant proteins derived from the parasite. The immune response to T. gondii is highly variable, so it may be necessary to refine this cellular model. This mini review highlights the major approaches in which PBMCs are used as a model of study for T. gondii and other apicomplexan parasites. The variables related to this model have significant implications for data interpretation and conclusions related to host-parasite interaction.

Antibodies against Apicomplexa protozoa and absence sarcocysts in heart tissues from horses in southern Brazil / Anticorpos contra protozoários do filo Apicomplexa e ausência de sarcocistos no miocárdio de equinos no sul do Brasil

Sarcocystis spp., Neospora spp., and Toxoplasma gondii are Apicomplexa protozoa that can infect horses. This study aimed to investigate the occurrence of antibodies against Sarcocystis spp., Neospora spp., and T. gondii in horses slaughtered in southern Brazil. The presence of histological lesions, tissue cysts, and Sarcocystis spp. DNA in the hearts of these horses was also investigated. A total of 197 paired serum and heart samples were evaluated by serology and direct microscopic examination; 50 of these samples were subjected to histopathological and PCR analyses. Antibodies against at least one of the protozoa were detected in 146 (74.1%) of the serum samples. The frequencies of positive serology were: 36% (71/197) against Sarcocystis spp., 39.1% (77/197) against Neospora spp., and 47.2% (93/197) against T. gondii. No cysts, Sarcocystis spp. DNA, or histopathological lesions were observed in myocardial tissue samples. The frequencies of antibody seropositivity against Sarcocystis spp., Neospora spp., and T. gondii showed that horses are frequently infected by these parasites in southern Brazil. The absence of sarcocysts in horse tissues is compatible with their role as aberrant/accidental hosts in the life cycle of Sarcocystis spp..(AU)

Sarcocystis spp., Neospora spp. e Toxoplasma gondii são protozoários que pertencem ao filo Apicomplexa e que podem afetar equinos. O objetivo deste estudo foi investigar a ocorrência de anticorpos contra Sarcocystis spp., Neospora spp. e T. gondii. A presença de lesões histológicas, cistos teciduais e DNA de Sarcocystis spp. no miocárdio de equinos abatidos no sul do Brasil também foi investigado. Um total de 197 amostras de soro juntamente com as respectivas amostras de coração, foram avaliadas por sorologia e exame microscópico direto. Destas amostras, 50 foram selecionadas e submetidas a análise histopatológica e PCR. Anticorpos contra pelo menos um dos protozoários foi detectado em 146 (74,1%) das amostras de soro. As frequências de sorologia positiva foram: 36% (71/197) para Sarcocystis spp., 39,1% (77/197) para Neospora spp. e 47,2% (93/197) para T. gondii. Não foram encontradas lesões histopatológicas, cistos e DNA de Sarcocystis spp. nas amostras de miocárdio dos equinos. As frequências de soropositividade para Sarcocystis spp., Neospora spp. e T. gondii mostra que os equinos podem ser frequentemente infectados por estes parasitas no sul do Brasil. A ausência de sarcocistose no coração dos equinos é compatível com seu papel como hospedeiro errático/acidental no ciclo de vida deste protozoário.(AU)

Characterisation of a Babesia orientalis apical membrane antigen, and comparison of its orthologues among selected apicomplexans.

In the present study, we identified and characterised the complete coding sequence of Babesia orientalis apical membrane antigen 1 (designated Bo-ama1); it is 1803bp in length and encodes a polypeptide of 601 amino acids (aa). The Bo-ama-1 gene product (Bo-AMA1) is predicted to be 67kDa in size and contains a signal peptide. Mature Bo-AMA1 is predicted to have one transmembrane region and a short cytoplasmic tail (C-terminal domain). The extracellular part of Bo-AMA1 has three functional domains (DI, DII and DIII) with 14 conserved cysteine residues. A Bo-AMA1 fragment containing all three of these domains (designated Bo-AMA1-DI/II/III) was cloned into the plasmid vector pET-28a and expressed as a recombinant (His-fusion) protein of 53kDa. Antibodies in the serum from a B. orientalis-infected water buffalo specifically recognised this protein in immunoblotting analysis. Rabbit antibodies raised against the recombinant protein were able to detect native Bo-AMA1 (67kDa) from erythrocytes of B. orientalis-infected water buffalo. Bo-AMA1 is a new member of the AMA1 family and might be a good antigen for the specific detection of antibodies produced in B. orientalis infected cattle. This protein is likely to play critical roles during host cell adherence and invasion by B. orientalis, as the AMA1s reported in other organisms such as Plasmodium falciparum and Toxoplasma gondii. Further research is required to explore the biological functions of this protein and to determine whether its immunisation can induce protective effects in water buffalo against B. orientalis infection.

The sicker sex: understanding male biases in parasitic infection, resource allocation and fitness.

The "sicker sex" idea summarizes our knowledge of sex biases in parasite burden and immune ability whereby males fare worse than females. The theoretical basis of this is that because males invest more on mating effort than females, the former pay the costs by having a weaker immune system and thus being more susceptible to parasites. Females, conversely, have a greater parental investment. Here we tested the following: a) whether both sexes differ in their ability to defend against parasites using a natural host-parasite system; b) the differences in resource allocation conflict between mating effort and parental investment traits between sexes; and, c) effect of parasitism on survival for both sexes. We used a number of insect damselfly species as study subjects. For (a), we quantified gregarine and mite parasites, and experimentally manipulated gregarine levels in both sexes during adult ontogeny. For (b), first, we manipulated food during adult ontogeny and recorded thoracic fat gain (a proxy of mating effort) and abdominal weight (a proxy of parental investment) in both sexes. Secondly for (b), we manipulated food and gregarine levels in both sexes when adults were about to become sexually mature, and recorded gregarine number. For (c), we infected male and female adults of different ages and measured their survival. Males consistently showed more parasites than females apparently due to an increased resource allocation to fat production in males. Conversely, females invested more on abdominal weight. These differences were independent of how much food/infecting parasites were provided. The cost of this was that males had more parasites and reduced survival than females. Our results provide a resource allocation mechanism for understanding sexual differences in parasite defense as well as survival consequences for each sex.

[Advances in the development of vaccines for bovine neosporosis]. / Avances en el desarrollo de vacunas contra la neosporosis bovina.

Neosporosis, a disease caused by the obligate intracellular protozoan Neospora caninum, produces abortions in cattle. The severe economic losses in cattle industry justify the need to develop control measures for preventing bovine abortion. Apicomplexan parasitic resistance is associated with T helper 1 immune response mediated by CD4 cytotoxic T lymphocytes, the production of interferon-gamma, interleukin-12, tumor necrosis factor and immunoglobulin G2. The reduction of vertical transmission in subsequent pregnancies and the low levels of abortion repetition suggests the existence of protective immune mechanisms. Inoculation with live tachyzoites before mating protects against infection and abortion. Antecedents of the development of live vaccines against other protozoa stimulate research to develop a live vaccine against N. caninum. On the other hand, an inactivated vaccine with low efficacy against neosporosis is useful in the prevention of abortion in farms with epizootic disease. A neosporosis vaccine should avoid abortion, transplacental transmission and infection persistence. In the present work, advances in vaccine development including lysate of tachyzoites, live parasites, recombinant antigens and vaccine vectors are reviewed.