Characterization of the biology and infectivity of Leishmania infantum viscerotropic and dermotropic strains isolated from HIV+ and HIV- patients in the murine model of visceral leishmaniasis

Abstract

BackgroundLeishmaniasis is a group of diseases with a variety of clinical manifestations. The form of the disease is highly dependent on the infective Leishmania species and the immunological status of the host. The infectivity of the parasite strain also plays an important role in the progression of the infection. The aim of this work is to understand the influence of the natural infectivity of Leishmania strains in the outcome of visceral leishmaniasis.MethodsIn this study we have characterized four strains of L. infantum in terms of molecular typing, in vitro cultivation and differentiation. Two strains were isolated from HIV+ patients with visceral leishmaniasis (Bibiano and E390M), one strain was isolated from a cutaneous lesion in an immunocompetent patient (HL) and another internal reference strain causative of visceral leishmaniasis (ST) also from an immunocompetent patient was used for comparison. For this objective, we have compared their virulence by in vitro and in vivo infectivity in a murine model of visceral leishmaniasis.ResultsMolecular typing unraveled a new k26 sequence attributed to MON-284 zymodeme and allowed the generation of a molecular signature for the identification of each strain. In vitro cultivation enabled the production of promastigotes with comparable growth curves and metacyclogenesis development. The HL strain was the most infective, showing the highest parasite loads in vitro that were corroborated with the in vivo assays, 6 weeks post-infection in BALB/c mice. The two strains isolated from HIV+ patients, both belonging to two different zymodemes, revealed different kinetics of infection.ConclusionDifferences in in vitro and in vivo infectivity found in the murine model were then attributed to intrinsic characteristics of each strain. This work is supported by other studies that present the parasite’s inherent features as factors for the multiplicity of clinical manifestations and severity of leishmaniasis.

Characterisation of the ex vivo virulence of Leishmania infantum isolates from Phlebotomus perniciosus from an outbreak of human leishmaniosis in Madrid, Spain

“…In this study, the median values of parasite load per BCN150-infected cells were considered representative samples (reference values) of our experiments using this well-characterized L. infantum strain. As expected at 24 h after infection [29,31], we detected a reduction in BCN150-infected the intracellular parasite load (for all three strains) compared to cells at the initial time point of infection (Figure 1C-D), which was more apparent in BMMø and BMDC. As previously described [31], the number of BMDC containing intracellular parasites dropped significantly between 4 h to 24 h. After the slight decrease observed at 24 h, the mean number of amastigotes per infected BMDC decreased at later time points, although the parasite burdens in cells infected with the BOS1FL1 and POL2FL7 isolates remained greater compared to cells infected with the BCN150 strain.…”

Can Attenuated Leishmania Induce Equally Effective Protection as Virulent Strains in Visceral Leishmaniasis?

“…To understand the strain-specific immunomodulation mechanisms that lead to protection to re-infection we used two strains of L. infantum, one dermotropic (HL) and the other viscerotropic (ST), which presented differential onset and progression of VL in mice. As previously shown [136], HL was able to colonize the spleen, liver and bone marrow in higher extent than ST parasites 6 weeks after infection (Figure 1, Infection bars). We hypothesized that these differences in infectivity could lead to distinct levels of protection.…”

“…In the re-infection experiments, animals were infected for 6 weeks with HL or ST strains as before and challenged intraperitoneally with 10 8 promastigotes of the same or the other strain; 6 weeks after challenge they were sacrificed (Re-inf HL and Re-inf ST bars). (A) Spleen, (B) liver and (C) femoral bone marrow were recovered for quantification of the parasite load by real time PCR [136]. Bars represent means ± SD of 5 to 9 animals of one experiment representative of two independent.…”

More than just exosomes: distinct Leishmania infantum extracellular products potentiate the establishment of infection

“…All the antibodies were used at a 1:100 dilution. Cells were then washed and resuspended in 150 μl flow cytometry buffer [28]. Flow cytometric acquisitions were performed in a FACSCanto TM II (BD) and analysed with FlowJo software v10 (TreeStar, Ashland, OR, USA).…”