Cellular and humoral responses to Leishmania major virulence factors in healed cutaneous leishmaniasis and Mediterranean visceral leishmaniasis patients

Mastomys natalensis Has a Cellular Immune Response Profile Distinct from Laboratory Mice

The multimammate mouse (Mastomys natalensis; M. natalensis) has been identified as a major reservoir for multiple human pathogens including Lassa virus (LASV), Leishmania spp., Yersinia spp., and Borrelia spp. Although M. natalensis are related to well-characterized mouse and rat species commonly used in laboratory models, there is an absence of established assays and reagents to study the host immune responses of M. natalensis. As a result, there are major limitations to our understanding of immunopathology and mechanisms of immunological pathogen control in this increasingly important rodent species. In the current study, a large panel of commercially available rodent reagents were screened to identify their cross-reactivity with M. natalensis. Using these reagents, ex vivo assays were established and optimized to evaluate lymphocyte proliferation and cytokine production by M. natalensis lymphocytes. In contrast to C57BL/6J mice, lymphocytes from M. natalensis were relatively non-responsive to common stimuli such as phytohaemagglutinin P and lipopolysaccharide. However, they readily responded to concanavalin A stimulation as indicated by proliferation and cytokine production. In summary, we describe lymphoproliferative and cytokine assays demonstrating that the cellular immune responses in M. natalensis to commonly used mitogens differ from a laboratory-bred mouse strain.

Leishmania major large RAB GTPase is highly immunogenic in individuals immune to cutaneous and visceral leishmaniasis

Background

We previously identified a Leishmania (L.) major large RAB GTPase (LmlRAB), a new atypical RAB GTPase protein. It is highly conserved in Leishmania species while displaying low level of homology with mammalian homologues. Leishmania small RAB GTPases proteins have been involved in regulation of exocytic and endocytic pathways whereas the role of large RAB GTPases proteins has not been characterized yet. We report here the immunogenicity of both recombinant rLmlRAB and rLmlRABC, in individuals with immunity against L. major or L. infantum.

Methods

PBMC were isolated from individuals cured of L. major (CCLm) or from healthy individuals. The latter were subdivided into high or low IFN-γ responders. Healthy high IFN-γ responders, considered as asymptomatics, were living in an endemic area for L. major (HHRLm) or L. infantum (HHRLi). Healthy low IFN-γ responders (HLR) were considered as naïve controls. Cells from all volunteers were stimulated with rLmlRAB or rLmlRABC. Cytokines were analysed by CBA and ELISA and phenotypes of IFN-γ-producing cells were analysed by flow cytometry.

Results

Both rLmlRAB and rLmlRABC induced high significant levels of IFN-γ in CCLm, HHRLm and HHRLi groups. Phenotype analysis of rLmlRAB and rLmlRABC-stimulated T cells in CCLm individuals showed a significant increase in the percentage of specific IFN-γ-producing CD4+ and CD8+ T cells. rLmlRAB induced significant granzyme B levels in CCLm and HHRLm. Low but significant granzyme B levels were detected in naïve group. IL-10 was detected in immune and naïve individuals.

Conclusion

We showed that rLmlRAB protein and its divergent carboxy-terminal part induced a predominant Th1 response in individuals immune to L. major or L. infantum. Our results suggest that rLmlRAB and rLmlRABC proteins are potential cross-species vaccine candidates against cutaneous and visceral leishmaniasis.

Elevated TGF-beta levels in drug-resistant visceral leishmaniasis

BACKGROUND

Poor and neglected populations in Africa are particularly affected with visceral leishmaniasis. The widespread emergence of resistance to pentavalent antimonials occurs globally and the unavailability of a vaccine in clinical use constitutes a major obstacle in disease control.

OBJECTIVE

To investigate the cytokine profile in human visceral leishmaniasis.

DESIGN

A cross-sectional laboratory-based study.

SETTING

Single center study carried out at the Institute of Endemic Diseases, University of Khartoum, Sudan.

PATIENTS AND METHODS

Soluble lysates of L major and L donovani were used to stimulate the lymphocytes of two groups of confirmed VL patients (group 1 [n=20] had respond to pentostam treatment and group 2 [n=5] were recorded as drug resistant after follow up) in a cellular proliferation assay and the levels of IFNg, IL-10, TNFa and TGFb were detected by cytokine ELISA.

MAIN OUTCOME MEASURES

Levels of IFNg, TNFa, IL-10 and TGFb.

RESULTS

A significant increase of IFNg and TNFa levels were reported in stimulated cells of drug susceptible and drug resistant groups, but no significant difference in IL-10 production was observed between the different antigens or between the patients groups. TGFb from stimulated lymphocytes was secreted in statistically significant amounts in patients reported as drug resistant in response to both L major and L donovani antigens (P < .001).

CONCLUSIONS

In VL patients, IFNg and TNFa are extremely produced in response to in vitro re-stimulation which means that the parasitic infection, although virulent and chronic, does not render patients as immunocompromised. However, TGFb is mostly associated with treatment failure.

LIMITATIONS

This study assessed secretory TGFb. A study with a larger sample size to assess TGFb gene expression and to follow its intracytoplasmic synthesis in drug resistant VL patients is recommended.

Linear B-cell epitope mapping of MAPK3 and MAPK4 from Leishmania braziliensis: implications for the serodiagnosis of human and canine leishmaniasis

The correct and early identification of humans and dogs infected with Leishmania are key steps in the control of leishmaniasis. Additionally, a method with high sensitivity and specificity at low cost that allows the screening of a large number of samples would be extremely valuable. In this study, we analyzed the potential of mitogen-activated protein kinase 3 (MAPK3) and mitogen-activated protein kinase 4 (MAPK4) proteins from Leishmania braziliensis to serve as antigen candidates for the serodiagnosis of human visceral and tegumentary leishmaniasis, as well as canine visceral disease. Moreover, we mapped linear B-cell epitopes in these proteins and selected those epitopes with sequences that were divergent in the corresponding orthologs in Homo sapiens, in Canis familiaris, and in Trypanosoma cruzi. We compared the performance of these peptides with the recombinant protein using ELISA. Both MAPK3 and MAPK4 recombinant proteins showed better specificity in the immunodiagnosis of human and canine leishmaniasis than soluble parasite antigens and the EIE-leishmaniose-visceral-canina-bio-manguinhos (EIE-LVC) kit. Furthermore, the performance of this serodiagnosis assay was improved using synthetic peptides corresponding to B-cell epitopes derived from both proteins.

A current perspective on leishmaniasis

There are many challenges facing the successful control and eradication of cutaneous and visceral leishmaniasis. Leishmaniasis is still endemic in many poverty stricken and war torn areas. Through the use of an extensive literature review, this article examined the global disease burden of cutaneous and visceral leishmaniasis. Surveillance and control measures for leishmaniasis being used by the World Health Organization were also discussed in this article. Finally, potential new treatments and possible vaccines for leishmaniasis were reviewed in this article.

Cellular and humoral responses induced by Leishmania histone H2B and its divergent and conserved parts in cutaneous and visceral leishmaniasis patients, respectively

Leishmania histone H2B has been reported to be a promising candidate for both vaccination and serodiagnosis. We evaluated the cellular immune responses induced by H2B and its divergent amino-terminal (H2B-N) and conserved carboxy-terminal (H2B-C) regions in individuals with a history of Localized Cutaneous Leishmaniasis (LCL) due to Leishmania (L.) major. H2B induced significantly high PBMC proliferation and IFNgamma levels in LCL individuals whereas significantly lower proliferation and IFNgamma levels were observed with the divergent part of the protein. All proteins induced IL10 in LCL and healthy individuals. We also evaluated the humoral responses induced by these proteins in patients with Mediterranean Visceral Leishmaniasis (MVL) due to L. infantum. H2B and H2B-N were highly recognized by MVL sera. Our results show that the entire H2B protein is more efficient than its amino- and carboxy-terminal regions in inducing a dominant Th1 profile in cured LCL subjects and suggest that this protein may constitute a potential vaccine against leishmaniasis. Furthermore, H2B and H2B-N are interesting antigens for serodiagnosis of MVL.