Cell mediated immunity and specific IgG1 and IgG2 antibody response in natural and experimental canine leishmaniosis.

In the present study, we have followed up Leishmania infantum infection in dogs: (1) naturally infected; (2) experimentally infected with amastigotes; and (3) experimentally infected with culture promastigotes. The main objective was to evaluate the differences of the humoral and cellular immune responses of each group. Sera from 12 beagle dogs were analysed for total anti-leishmanial antibodies and IgG1 and IgG2 subclasses by enzyme-linked immunosorbent assay (ELISA). Lymphoproliferation to L. infantum antigen was also performed. All naturally infected animals were symptomatic with a marked humoral response. Dogs inoculated with amastigotes were asymptomotic and presented lower antibody titres than naturally infected. Dogs inoculated with culture promastigotes were asymptomotic with no significant humoral response. Strong proliferative responses to Leishmania antigen was observed in dogs inoculated with promastigotes. In our experimental model, IgG1 antibody levels presented a similar pattern in all infected animals, and IgG2 reactivity was high in naturally infected dogs.

Performance of immunoblotting in diagnosis of visceral Leishmaniasis in human immunodeficiency virus-Leishmania sp.-coinfected patients.

This study evaluated the performance of immunoblotting with Leishmania infantum soluble antigens for the diagnosis of visceral leishmaniasis in human immunodeficiency virus (HIV)-infected and immunocompetent patients and assessed the humoral responses of patients coinfected with HIV and Leishmania. In this work, the results of the immunoblot analysis were compared to those of parasitological examination (Giemsa-stained smears and/or parasite isolation in Novy, Nicolle, and MacNeal medium from bone marrow) and indirect immunofluorescence and counterimmunoelectrophoresis techniques. Patients were considered to be infected if one or more of the comparison techniques gave a positive result. Immunoblotting was considered to be positive if at least one band was present. For 198 HIV-positive patients with a clinical suspicion of visceral leishmaniasis, immunoblot analysis had a sensitivity of 70.6%, a specificity of 73.2%, and an accuracy of 72.7%. For a separate group of 40 immunocompetent patients not infected with Leishmania, the immunoblot analysis was negative for all patients (100% specificity), and for a third group of 32 immunocompetent patients with confirmed visceral leishmaniasis, the immunoblot analysis was positive for all patients (100% sensitivity). Sera of coinfected patients recognized few bands and recognized bands at lower intensities compared with sera from immunocompetent patients. The most frequently detected band was 63 to 66 kDa (55.9%), with the difference being statistically significant compared to frequency of detection of the other bands. This study confirms that the humoral response in patients coinfected with HIV and Leishmania is much lower than that in immunocompetent patients and that the immunoblot method is a sensitive, noninvasive, and specific serological technique for the diagnosis of visceral leishmaniasis in immunocompromised patients.

Latent class analysis permits unbiased estimates of the validity of DAT for the diagnosis of visceral leishmaniasis.

BACKGROUND: Substantial uncertainty surrounds the specificity of the Direct Agglutination Test (DAT) for visceral leishmaniasis (VL) in clinical suspects, since no good gold standard exists for unequivocally identifying diseased subjects. We explored the Latent Class Analysis (LCA) modelling technique to circumvent this problem. PATIENTS AND METHODS: Data on 149 clinical suspects recruited in 1993-96 during a multicentre study in Sudan were re-examined. Clinical data, lymph node and bone marrow aspirate and DAT results were available. IFAT was performed in 1997 on stored filter paper blood of 80 individuals. Classical Validity Analysis (CVA) in a 2 x 2 contingency table with parasitology as a gold standard was compared with the parameter estimates produced by the best fitting LCA model. RESULTS: The sensitivity estimates of DAT produced by CVA (98% (89%-100%)) were almost exactly reproduced by LCA. The specificity estimates by LCA were substantially higher than those obtained in CVA. Specificity of DAT depended, however, on whether the subject was treated for VL before. In subjects without prior treatment, CVA estimated DAT specificity at 68% (56%-79%), whereas LCA estimated it at 85% (63%-100%). CONCLUSION: LCA modelling proved a useful tool, as it gave consistent estimates of test characteristics and allowed for control of confounding factors and interaction effects. Since VL is a life-threatening disease for which expensive but effective and safe treatment exists, a clinical suspect in an endemic area should be treated on the basis of a positive DAT result.