Abstract
Visceral Leishmaniasis and HIV-AIDS coinfection (VL/HIV) is considered a life-threatening pathology when undiagnosed and untreated, due to the immunosuppression caused by both diseases. Serological tests largely used for the VL diagnosis include the direct agglutination test (DAT), ELISA and immunochromatographic (ICT) assays. For VL diagnosis in HIV infections, different studies have shown that the use of the DAT assay facilitates the VL diagnosis in co-infected patients, since the performance of the most widely used ELISA and ICT tests, based on the recombinant protein rK39, are much less efficient in HIV co-infections. In this scenario, alternative recombinant antigens may help the development of new serological diagnostic methods which may improve the VL diagnosis for the co-infection cases. This work aimed to evaluate the use of the recombinant Lci2 antigen, related to, but antigenically more diverse than rK39, for VL diagnosis in co-infected sera through ELISA assays. A direct comparison between recombinant Lci2 and rK39 was thus carried out. The two proteins were first tested using indirect ELISA with sera from VL afflicted individuals and healthy controls, with similar performances. They were then tested with two different sets of VL/HIV co-infected cases and a significant drop in performance, for one of these groups, was observed for rK39 (32% sensitivity), but not for Lci2 (98% sensitivity). In fact, an almost perfect agreement (Kappa: 0.93) between the Lci2 ELISA and DAT was observed for the coinfected VL/HIV patients. Lci2 then has the potential to be used as a new tool for the VL diagnosis of VL/HIV co-infections.
Highlights
Visceral Leishmaniasis (VL) is considered a critical and opportunistic infection in people with HIV-AIDS [1]
Human sera samples were divided into five groups: VL—49 sera from patients with parasitologically confirmed VL diagnosis; VL/ HIV-A—16 HIV sera with parasitologically confirmed VL diagnosis; VL/HIV-B—47 HIV sera with the VL diagnosis confirmed by direct agglutination test (DAT) assays; Control—50 sera from healthy control individuals, all negative for VL and HIV; HIV—12 HIV positive sera with a VL negative diagnosis confirmed through DAT assays
These two recombinant proteins were never directly compared, so in this study we decided first to evaluate both regarding their efficiency for VL diagnosis, using a commercially purchased rK39 and a newly prepared batch of recombinant Lci2 (Fig 1A)
Summary
Visceral Leishmaniasis (VL) is considered a critical and opportunistic infection in people with HIV-AIDS [1]. The visualization of the Leishmania parasite in bone marrow aspirates is the gold standard test for the VL diagnosis It is highly specific, despite a low sensitivity, but it is an invasive method that can pose risks to the patients, especially those infected with HIV-AIDS [6,7,8]. Serological methods are largely used as an alternative for VL diagnosis This is mainly due to the easier sample collection, as well as to the various diagnostic methods available: immunofluorescence, ELISA, direct agglutination test (DAT) and immunochromatographic tests (ICT). The serological tests do not differentiate between active infection and cured VL, they remain as viable choices for the screening of VL/HIV co-infected samples, requiring simple procedures and less specialized equipment [4,5,6]
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