COOPERATIVE RESEARCH ON A VACCINE AGAINST LEISHMANIASIS IN MANU, PERU
Coordination: Prof. François Luis Blanc, 2001-2007
partners: France: IRD, Institut de Recherches et Développement.
Peru: UNSAAC, (Prof. Rosa Pacheco, unidad leishmaniasis, Cusco).
Universidad Cayetano Heredia UPCH, (Prof. Jorge Arevalo, molecular biology dpt, Lima).
MOVIES : A preventive campaign against Leishmaniasis in a matsiguengas community of the peruvian Amazon (sept 2006)
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look at a film about prevention:
click at: http://www.youtube.com/v/i3LJ_hkN0uM&rel=1
PROJECT DESCRIPTION :
Objectives of the project : 1- To understand, through a multidisciplinary approach, why in an endemic area of Manu, Perú, different clinical outcomes (asymptomatic/paucisymptomatic versus severe mucocutaneous (MC) or visceral disease (VL) result from infection by Leishmania braziliensis : identification of factors determining resistance or susceptibility to the disease.2- To evaluate the potential efficiency of excretory/secretory antigens of Leishmania promastigotes to induce protective immunity (Th1 type response) using human cell culture assays.Specifically, the project proposal will address following objectives :
1- To characterise the study population by a two years longitudinal follow-up.
2- To characterise the humoral and cellular immune response (ex-vivo) of the host to total Leishmania antigens and to the candidate vaccine antigens (LESA) in subjects with cutaneo mucosal MC or VL (before and after treatment) and asymptomatic subjects.
3- To evaluate the impact of parasite diversity on L. braziliensis infection outcome and on the subjects immunological responses.
4- To search for host genetic factors determining susceptibility or resistance to the disease and/or polarised immune responses. Our research project, integrating on the same subjects epidemiological, parasitological, immunological and host genetic studies will for the first time provide a clear picture of the interplay between environmental, parasitic and host factors in the development of MC and VL. The study of the vaccine antigen specific antibodies and of the cellular immune responses induced ex-vivo in T-cell stimulation assays in VL patients before and after treatment and from asymptomatic subjects will determine if the project should be followed by a vaccine trial. Furthermore the immunological and host genetics studies will provide new insights on the critical biological pathways implicated in the host resistance or susceptibility to MC or VL and therefore help in orienting new therapeutic or vaccine strategies.
State of the art
Visceral leishmaniasis (VL) is the most severe form of leishmaniasis. VL is a chronic disease caused by viscero-tropic Leishmania parasites (L. donovani, L. infantum L. chagasi, L. braziliensis). Mucocutaneous (MC) “espundia” is more common in the amazonian basin although a few outbreaks of visceral forms have been reported. MC Leishmaniasis due to L. braziliensis begins with simple skin ulcers, but these can spread to hideous tissue destruction-especially of the nose and the mouth, a disease already known to the Incas as the “UTA”.
Leishmania that are inoculated to their human host by sand flies, rapidly invade macrophages. The main clinical symptoms of VL are an enlarged spleen and a prolonged irregular fever and the disease is almost always fatal if left untreated. Approximately *500,000 new cases of human VL occur annually and the disease is mainly found in Brazil, Peru, East Africa and on the Indian sub-continent. Affected populations are among the poorest in the world and are not much aware of existing preventive measures. Furthermore misuse of the first-line drug in these communities is widely spread and the lack of response to pentavalent antimonials has been increasing sharply these last years.
However, in endemic areas it is now well established that most exposed individuals are asymptomatic. These individuals are able to mount a protective cellular immune response against Leishmania and either eliminate infection or remain asymptomatic carriers. Factors determining whether an infection remains asymptomatic or progresses toward VL or invalidating MC are largely unknown and probably result from the complex interaction between environmental, parasite and host related factors. In order to develop disease control strategies, it is therefore fundamental to understand why in a given transmission focus some subjects remain asymptomatic whereas others develop VL or invalidating MC. Furthermore there is an urgent need for the development of new low cost drugs and/or new therapeutic interventions such as a vaccine. Three types of markers or factors were identified: (i) indirect genetic markers of pathogenicity, (ii) factors called invasive/evasive determinants and (iii) factors called pathoantigenic. However data are lacking on the role played by such factors in natural population of parasites and yet no genetic markers were found to correlate with the different clinical outcomes. From the host point of view, cumulative data from human epidemiological studies now indicate that host genetic factors play an important role in the determination of the VL or MC resistant/susceptible status. Several genetic studies of VL multi-case families carried out in Sudan have shown that alleles at the NRAMP1, lL4 and INFG loci are preferentially transmitted from heterozygous parents to their affected child.
These results suggest that polymorphisms of these genes may predispose to VL and fit well the T-cell mediated nature of the disease. However a genome wide search for susceptibility genes in Sudanese families showed that other genes than those identified in mice play a most important role. This study identified a major susceptibility locus for VL on chromosome 22q12 and possibly another one on chromosome 2q23. Whether the same genetic loci or different ones are involved in peruvian VL or MC remains to be studied.
Immunity in leishmaniasis is considered mainly T cell-mediated, but also more non-specific factors acting in the early stage of infection are now considered as important for either the progression or control of disease. In cutaneous Leishmaniasis MC, the outcome of infection is critically dependent on the activation of one of the two Th1/Th2 CD4+ T-cells subsets.
Cures for leishmaniasis are related to a Th1-type cellular immune response leading to the activation of infected macrophages and NO-mediated amastigote killing. In contrast Th2 lymphocytes expansion often results in disease progression. However in human infection by L. braziliensis such a dichotomy of the CD4+ T-cells has not yet been fully documented and we will try to identify a number of immunologic parameters in subjects exhibiting patterns of progressive disease or apparent resistance.
Recently, a vaccine against canine VL(Ref) was developed involving Leishmania excreted secreted antigen (LESA) produced in axenic conditions (IRD, France). LESA was proved efficient both experimentally and in naturally Leishmania infantum exposed dogs of southern France (90% protection). The vaccine-induced protection correlates in dogs with an early establishment of a long lasting predominantly Th1-type cellular immune response specifically directed against LESA before and after experimental and natural infection.
ASPECTOS INOVADORES (spanish)
- El estudio de los factores biológicos, ecológicos y socio-culturales que afectan la incidencia y la prevalencia, y la evolución de las enfermedades tropicales, y el indagar al mismo tiempo por los efectos y la visión de las enfermedades en la cultura y la organización social del grupo matsiguengas en estudio, contribuye a que la epidemiología ecológica y socio-cultural tengan un mayor impacto en la prevención de la enfermedad por la misma población. Se enfoca la prioridad en el control de los vectores (lutzomyia chagas y yulli) usando sprays de insecticidas en las casas y en la destrucción de los huéspedes reservorios identificados (roedores orizomis).
- El conocimiento de los focos ecopidemiologicos de la Leishmaniasis en la selva amazónica ha permitido profundizar en la ecología de la transmisión de la Leishmaniasis Tegumentaria Americana. Se pretende avanzar en el conocimiento ecológico de la selva amazónica, en la cadena ecológica de climas, suelos, y poblaciones y animales y en el conocimiento de los tratamientos tradicionales con plantas.
- implementar una prevención vacinal : una nueva generación de vacunas esta investigada por Jean-Loup Lemesre, IRD Francia. Una investigación de la eficacia en humanos podría ser aplicada a la comunidad Matsiguengas y a los visitantes ocasionales de la provincia de la Convención (Turistas a Machu Pichu, colonos y migrantes sasonales).
RESULTS (September 2010)
The humoral and cellular immune response (ex-vivo) of the host to total Leishmania antigens and to the candidate vaccine antigens (LESA) in subjects with cutaneo mucosal MC or VL was not significant enough to select a purified secreted peptide available for a vaccine.
Ref: LEMESRE J.L., HOLZMULLER P. CAVALEYRA M., HOTTIN G., PAPIEROK G. Protection against visceral leishmaniasis infection in dogs immunized with purified secreted antigens of Leishmania infantum promastigotes, Vaccine, (2005), vol 2, 2840.
AGUILAR E.D., VARGAS AYITUMA A., Pruebas parasicológicas e intradermo reacción de Montenegro (IDRM) en pacientes clínicamente diagnosticados con Leishmaniasis del distrito de Yanatile, Calca, Cusco. Situa VIII (1995), p 45-48.