Mechanisms Relating to the Distinct in Vitro Susceptibility of Human Macrophages to L. Viannia Infection
Condition: Leishmaniasis
MeSH terms: Leishmaniasis
Study type: Observational

Summary: 
      The purpose of this study is to determine how the body defends itself against Leishmania
      (Viannia), a parasite that can cause a skin infection and skin sores. Certain cells in the
      immune system act more aggressively against Leishmania in people with mild Leishmania
      symptoms than in those who have long-term or recurring symptoms of the disease. Participants
      in the study will include people who currently have Leishmania infection, people who have had
      the infection in the past, and people who have never been exposed to the parasite. This study
      will enroll 220 adults, ages 18 to 70 years, at 3 sites in Colombia. Blood samples will be
      collected from volunteers at least once during the study. Participants will also undergo HIV
      testing. Volunteers will participate in up to 2 study visits, scheduled 2-3 weeks apart.
    

Detailed description: 
      This is a cross-sectional study that aims to determine the mechanisms that lead to the
      distinct in vitro susceptibility of human macrophages to L. Viannia infection, and their
      relationship to clinical phenotype. It is the third part of a study which includes DMID
      protocols 06-0009 and 06-0010. The general objective of the study is to determine the
      mechanisms that lead to the distinct in vitro susceptibility of human macrophages to L.
      Viannia infection, and their relationship to clinical phenotype. (Understanding the immune
      mechanisms underlying disease should provide insight for the development of new methods for
      treatment and intervention.) The specific objectives of the study are: to determine the
      association of the Toll response profile of monocytes and macrophages with the in vitro
      susceptibility phenotype, and analyze Toll receptor response in relation with both in vitro
      and clinical phenotype in participants presenting asymptomatic, chronic and recurrent disease
      and in healthy donors (controls)(Toll receptors); to determine gene expression response of
      susceptible and resistant macrophages to exposure and infection by L. panamensis, in order to
      identify genes and gene products that determine the course of infection in the host cell and
      that are linked to clinical response; to define the interaction of cytokines and Leishmania
      infection in promoting the latent persistence of infection or activation of growth, and to
      explore the role of apoptosis in elimination or propagation of infection (Apoptosis); and to
      determine the functional phenotypic characteristics of susceptible and resistant macrophages
      from healthy donors and clinically disparate individuals by flow cytometric analyses
      (Functional Phenotype of mononuclear phagocytes). Participants of the four specific
      objectives will be asked to provide relevant demographic, clinical and epidemiologic
      information and blood samples. Monocytes and macrophages differentiated from peripheral blood
      samples will be analyzed by different methodologies (flow cytometry, Real time PCR, ELISA and
      microarray analysis), and the results compared across the groups in order to determine if the
      macrophage response to infection is a determinant of recurrent and/or chronic disease
      development. Participants will be enrolled at three sites in Colombia: CIDEIM, Cali; CIDEIM,
      San Andrés Hospital, Tumaco; and San Juan Bautista Hospital, Chaparral. Patients (males and
      females) aged between 18-70 years with historic chronic or recurrent cutaneous leishmaniasis
      diagnosed at any of these three study sites will be invited to participate in the study.
      Asymptomatic and healthy donors (controls) will also be enrolled. A maximum of 220
      participants will be enrolled. For historic (chronic and recurrent) and asymptomatic
      participants, a single study visit is planned. For healthy donors, 2 study visits are
      planned. The second visit will be programmed 2-3 weeks after the first visit. Study outcome
      measures will be levels of transcription of cytokines (e.g. TNF-alpha, IL-10, IL-12) and
      nuclear transcription factors normalized to the number of macrophages; percentage of
      non-infected and infected macrophages/monocytes expressing specific cytokine receptors and
      Toll like receptors; density of receptor expression; percentage of apoptotic cells; number
      and change in number of parasites in apoptotic and non-apoptotic cells; nitric oxide level;
      cytokine production as concentration of supernatants of macrophage cultures (e.g. TNF-alpha,
      IL-10, and IL-12); intracellular cytokine production, intracellular nitric oxide level;
      percentage of infected macrophages/monocytes and number of intracellular parasites over time
      to assess survival and replication; and percentage of non-infected and infected
      macrophages/monocytes expressing specific activation and differentiation markers and the
      intensity of marker expression.
    

Observational model: Other
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Historical cases of chronic disease:

          -  Age between 18-70 years

          -  Historic parasitologically confirmed, skin test positive cutaneous leishmaniasis (CL)
             patients who presented chronic CL lesions of > 6 months duration at the time of
             diagnosis

          -  No active lesions

        Historical cases of recurrent disease:

          -  Age between 18-70 years

          -  Historic CL patients who have developed new parasitologically confirmed lesions after
             resolution of prior disease

          -  No active lesions

        Asymptomatic infection:

          -  Age between 18-70 years

          -  Resident of endemic area

          -  No history or evidence of active or prior dermal leishmaniasis

        Healthy donors:

          -  Age between 18-70 years

          -  No history or evidence of exposure to transmission of leishmaniasis
      
Keywords: Leishmaniasis, Leishmania (Viannia), Colombia