Regulator and effector functions of T-cell subsets in human Leishmanaia infections

Enhancement of peritoneal macrophage phagocytic activity against Leishmania major by garlic (Allium sativum) treatment

It has been shown that garlic (Allium sativum) extract modulates immune responses. Macrophage activation is required to establish control of the intracellular infection and progressive disease of leishmaniasis. In this study, we consider the effect of a garlic extract and a fraction isolated from it on the engulfment and destruction of Leishmania major by resident peritoneal macrophages of Balb/c mice. In regard to this study, the infiltration of macrophages in the peritoneal cavity after garlic treatment and the rate of amastigotes per macrophage were determined. The results show that a single dose of 20 mg/kg garlic extract intraperitoneally (i.p.) alters the number of peritoneal macrophages for at least 2 weeks. Intraperitoneal injection of garlic extract (20 mg/kg) or its protein fraction (0.04 mg/kg) augments parasite engulfment and destruction of intracellular amastigotes by macrophages.

THE HUMAN CYTOKINE RESPONSE TO LEISHMANIA MAJOR EARLY AFTER EXPOSURE TO THE PARASITE IN VITRO

Leishmaniasis is caused by the protozoan parasite Leishmania spp. In murine leishmaniasis, a T helper cell type-I (Th1) response, characterized by the secretion of interferon (IFN)-gamma is necessary for clearing the infection. whereas a Th2 response, accompanied by the production of interleukin (IL)-5, can exacerbate the disease. Moreover, the early cytokine milieu is thought to play an important role in determining the outcome of infection. In human leishmaniasis little is known about this early cytokine response. Because of this, we cocultured human peripheral blood mononuclear cells (PBMC) with Leishmania major in vitro and measured the production of IFN-gamma, IL-5, and IL-10. We also treated PBMC cultures with various cytokines and neutralizing anticytokines. We found that the principal cytokine produced was IFN-gamma and that its production was regulated by IL-10 and IL-12. In contrast, only low levels of Th2 cytokines such as IL-5 were produced. Therefore, the Th1-Th2 dichotomy that exists in inbred strains of mice does not appear to apply to the response of humans to L. major. Rather, Th2 cytokines may play a role in regulating IFN-gamma production.

Characterizing cellular immune response to kinetoplastid membrane protein-11 (KMP-11) during Leishmania (Viannia) panamensis infection using dendritic cells (DCs) as antigen presenting cells (APCs)

In vitro peptide binding assays and DCs pulsed with recombinant KMP-11 (rKMP-11) plus six 20-mer overlapping peptides covering the entire protein of Leishmania (Viannia) panamensis (L(V)p) promastigotes were used to identify T-cell epitopes in this protein. Such in vitro binding assays, using HLA DRB1* 0101, -0401, -0701 and -1101 alleles, demonstrated that two peptide sequences (DEEFNKKMQEQNAKFFADKP and FKHKFAELLEQQKAAQYPSK) exhibited high HLA DRB1* 0401 allele binding capacity. rKMP-11 specific T-cell proliferation and cytokine production, derived from 13 volunteers exposed to the parasite, suggested that using autologous DCs as APCs becomes advantageous in uncovering T-cell epitopes promoting proliferation and differences in IFN-gamma and IL-4 production in T-cells from volunteers with ACTIVE and CURED undetectable disease when other APCs were used. The two peptides which bound in vitro to the HLA DRB1* 0401 allele were immunogenic in HLA DRB1* 04 volunteers, thus validating the use of in vitro binding assays for predicting epitopes in this protein. The experimental approach used here may prove useful for characterizing T-cell epitopes in a protein useful in designing peptide-based vaccine candidates for Leishmania and other intracellular pathogens.

[Visceral leishmaniasis and B fulminant hepatitis association: case report]

The case of a 20-year-old man with hepatoesplenomegaly, fever and severe hepatic insufficiency is reported. Histopathological and immunohistochemical studies of tissue specimens obtained at autopsy led to diagnosis of visceral leishmaniasis and fulminant hepatitis B. The authors pointed out a possible influence of immunological response related with visceral leishmaniasis in development of severe hepatic involvement by hepatitis B virus.

Immunochemotherapy in American cutaneous leishmaniasis: immunological aspects before and after treatment

In this study, we evaluated the immune response of patients suffering from cutaneous leishmaniasis treated with two distinct protocols. One group was treated with conventional chemotherapy using pentavalent antimonium salts and the other with immunochemotherapy where a vaccine against cutaneous leishmaniasis was combined with the antimonium salt. Our results show that, although no differences were observed in the necessary time for complete healing of the lesions between the two treatments, peripheral blood mononuclear cells from patients treated by chemotherapy showed smaller lymphoproliferative responses at the end of the treatment than those from patients in the immunochemotherapy group. Furthermore, IFN-gamma production was also different between the two groups. While cells from patients in the chemotherapy group produced more IFN-gamma at the end of treatment, a significant decrease in this cytokine production was associated with healing in the immunochemotherapy group. In addition, IL-10 production was also less intense in this latter group. Finally, an increase in CD8+ -IFN-gamma producing cells was detected in the chemotherapy group. Together these results point to an alternative treatment protocol where healing can be induced with a decreased production of a potentially toxic cytokine.