CD43 sialoglycoprotein modulates cardiac inflammation and murine susceptibility to Trypanosoma cruzi infection.

CD43 (leukosialin) is a large sialoglycoprotein abundantly expressed on the surface of most cells from the hematopoietic lineage. CD43 is directly involved in the contact between cells participating in a series of events such as signaling, adherence and host parasite interactions. In this study we examined the role of CD43 in the immune response against Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, a potential life-threatening illness endemic in 21 Latin American countries according to the WHO. The acute stage of infection is marked by intense parasitemia and cardiac tissue parasitism, resulting in the recruitment of inflammatory cells and acute damage to the heart tissue. We show here that CD43-/- mice were more resistant to infection due to increased cytotoxicity of antigen specific CD8+ T cells and reduced inflammatory infiltration in the cardiac tissue, both contributing to lower cardiomyocyte damage. In addition, we demonstrate that the induction of acute myocarditis involves the engagement of CD43 cytoplasmic tripeptide sequence KRR to ezrin-radixin-moiesin cytoskeletal proteins. Together, our results show the participation of CD43 in different events involved in the pathogenesis of T. cruzi infection, contributing to a better overall understanding of the mechanisms underlying the pathogenesis of acute chagasic cardiomyopathy.

The role of innate immune signals in immunity to Brucella abortus.

Innate immunity serves as the first line of defense against infectious agents such as intracellular bacteria. The innate immune platform includes Toll-like receptors (TLRs), retinoid acid-inducible gene-I-like receptors and other cytosolic nucleic acid sensors, nucleotide-binding and oligomerization domain-like receptors, adaptors, kinases and other signaling molecules that are required to elicit effective responses against different pathogens. Our research group has been using the Gram-negative bacteria Brucella abortus as a model of pathogen. We have demonstrated that B. abortus triggers MAPK and NF-κB signaling pathways in macrophages in a MyD88 and IRAK-4-dependent manner. Furthermore, we claimed that so far TLR9 is the most important single TLR during Brucella infection. The identification of host receptors that recognize pathogen-derived nucleic acids has revealed an essential role for nucleic acid sensing in the triggering of immunity to intracellular pathogens. Besides TLRs, herein we describe recent advances in NOD1, NOD2, and type I IFN receptors in innate immune pathways during B. abortus infection.

Improved canine and human visceral leishmaniasis immunodiagnosis using combinations of synthetic peptides in enzyme-linked immunosorbent assay.

BACKGROUND: Zoonotic visceral leishmaniasis (VL) is a severe infectious disease caused by protozoan parasites of the genus Leishmania and the domestic dogs are the main urban parasite reservoir hosts. In Brazil, indirect fluorescence antibody tests (IFAT) and indirect enzyme linked immunosorbent assay (ELISA) using promastigote extracts are widely used in epidemiological surveys. However, their sensitivity and specificity have often been compromised by the use of complex mixtures of antigens, which reduces their accuracy allowing the maintenance of infected animals that favors transmission to humans. In this context, the use of combinations of defined peptides appears favorable. Therefore, they were tested by combinations of five peptides derived from the previously described Leishmania diagnostic antigens A2, NH, LACK and K39. METHODOLOGY/PRINCIPAL FINDINGS: Combinations of peptides derived A2, NH, LACK and K39 antigens were used in ELISA with sera from 44 human patients and 106 dogs. Improved sensitivities and specificities, close to 100%, were obtained for both sera of patients and dogs. Moreover, high sensitivity and specificity were observed even for canine sera presenting low IFAT anti-Leishmania antibody titers or from asymptomatic animals. CONCLUSIONS/SIGNIFICANCE: The use of combinations of B cell predicted synthetic peptides derived from antigens A2, NH, LACK and K39 may provide an alternative for improved sensitivities and specificities for immunodiagnostic assays of VL.

Local injection of BDNF producing mesenchymal stem cells increases neuronal survival and synaptic stability following ventral root avulsion.

The present study proposed to graft mesenchymal stem cells (MSCs), which continuously produce BDNF, into the spinal cord ventral horn, after ventral root avulsion. Neurotrophin expression was naturally achieved by culturing MSCs in an undifferentiated state for at least 10 weeks. Lewis rats were subjected to unilateral avulsion of lumbar ventral roots, receiving 3 x 10(5) cells injected through the lateral funiculus. Two weeks after surgery, the animals were sacrificed and neuronal survival, astroglial reaction and synaptic inputs within the motor nucleus analyzed. The results indicated that the MSCs treatment significantly rescued avulsed motoneurons. Such neuronal survival was related to in vivo mRNA up regulation as well as expression of BDNF and GDNF. Such increase was correlated to the preservation of synaptophysin- positive nerve terminals. Thus it was proposed that when maintained undifferentiated for a period of 10 weeks, MSCs may be used as a continuous source of BDNF, positively influencing neuronal survival and synaptic plasticity.

Protective immunity against challenge with Leishmania (Leishmania) chagasi in beagle dogs vaccinated with recombinant A2 protein.

In this study, we investigated in dogs the immunogenicity and protective immunity against Leishmania (Leishmania) chagasi infection induced by vaccination with a formulation containing the recombinant A2 protein, an amastigote specific antigen, and saponin. Vaccinated animals produced significantly increased levels of total IgG and IgG2, but not IgG1 anti-A2 antibodies, and remained negative in conventional leishmaniasis serodiagnostic methods. Significantly increased IFN-gamma and low IL-10 levels were detected in vaccinated animals before and after challenge, as compared to control animals. Importantly, while the symptoms onset appeared as early as three months after infection in most control dogs, 14 months after challenge, 5 out of 7 vaccinated dogs remained asymptomatic. Therefore, immunization with rA2 antigen was immunogenic and induced partial protection in dogs, and allowed the serological differentiation between vaccinated and infected animals, an important requirement for a canine visceral leishmaniasis (CVL) vaccine.

Immunization with radioattenuated yeast cells of Paracoccidioides brasiliensis induces a long lasting protection in BALB/c mice.

Paracoccidioides brasiliensis is the fungus agent of paracoccidioidomycosis, a chronic systemic disease prevalent in Latin America. The aim of the present work was to evaluate the protection elicited by the immunization of BALB/c mice with radioattenuated yeast cells of P. brasiliensis. The immunization promoted a long lasting protection against highly infective yeast forms of P. brasiliensis. A 99.5% decrease in CFUs recovery was verified 90 days post challenge. At the same time the levels of IgG2a and IFN-gamma were high while a very low production of IL-10 and IL-5 was verified, suggesting that a Th1 pattern was dominant. This work shows the potential of radioattenuated yeast cells for the development of vaccines against fungi infections.