Parasite Burden in Hamsters Infected with Two Different Strains of Leishmania (Leishmania) infantum: “Leishman Donovan Units” versus Real-Time PCR

Abstract

To develop and test new therapeutics and immune prophylaxis strategies for visceral leishmaniasis (VL), understanding tissue parasitism evolution after experimental infection with Leishmania infantum is important. Experimental infection in a hamster model (Mesocricetus auratus) reproduces several typical aspects of canine and human VL that are closely related to the inoculum’s route. We quantified the parasitism in the liver and spleen of hamsters experimentally infected by various routes (intradermal, intraperitoneal, and intracardiac [IC]) and different strains of L. infantum (MHOM/BR/74/PP75 and Wild) and compared two different methodologies to evaluate tissue parasitism (Leishman Donovan units [LDU] and real-time qPCR). In addition, the quantification of specific total-IgG in the serum of uninfected and infected hamsters was determined by ELISA. The animals were followed for 1, 3, 6 and 9 months post-infection for survival analysis. We found that infection with the Wild strain by the IC route resulted in higher mortality. Positive antibody (IgG) responses were detected with higher peaks at 6 and 9 months in the IC group inoculated with PP75 strain. However, in animals infected with the Wild strain the IgG levels were elevated in all infected groups during all the time evaluated. We also observed by LDU analysis that the IC route lead to higher parasitism in the liver and spleen with both strains. Furthermore, qPCR showed higher sensitivity for identifying animals with low parasitic burden. In conclusion, qPCR can be useful for assessing parasitism in the spleen and liver of a hamster model infected with L. infantum independent of the route of infection, and this technique may become an essential tool for assessing parasite density in the hamster model after experimental treatment or immunization with potential vaccine candidates.

Causes and consequences of higher Leishmania infantum burden in patients with kala‐azar: a study of 625 patients

“…However, in the present study, which included a larger sample population, patients with HIV had a median blood parasite burden that was approximately three times higher than that in patients without HIV coinfection. While bone marrow parasitism may be organ specific, DNA detected in the blood reflects the level of parasitism in the body overall, as previously described in both animals and humans . Unfortunately, CD4+ counts were not registered in the database, and its influence on the parasite burden could not be ascertained.…”

Wnt5a Signaling Promotes Host Defense againstLeishmania donovaniInfection

“…After air-drying, the smears were fixed in absolute methanol, stained with Giemsa, and examined using a 1003 oil immersion objective and a Leica DFC450c camera. Parasite load was calculated as LeishmanDonovan units by counting the number of amastigotes per 1000 host nuclei and multiplying it by tissue weight (29).…”

Performance of LBSap Vaccine after Intradermal Challenge with L. infantum and Saliva of Lu. longipalpis: Immunogenicity and Parasitological Evaluation

“…PCR conditions were as follows: an initial denaturation step at 95uC for 10 min followed by 40 cycles of denaturation at 95uC for 15 s and annealing/extension at 60uC for 1 min. Standard curves were prepared for each run using known quantities of pGEMH T plasmids (Promega, USA) containing inserts of interest [32]. In order to verify the integrity of the samples, the same procedure was carried out for the GAPDH gene (115 bp fragment GenBank accession number AB038240).…”