Immunological and histopathological studies in a rodent model infected with Leishmania infantum promastigotes or amastigotes

Abstract

Infection with Leishmania infantum promastigotes (group I) and amastigotes (group II) was evaluated over 32 weeks, using Syrian golden hamsters as an experimental model. Spleen cells strongly responded to the specific antigen at 12 (group I) and 16 weeks (group II) post-inoculation (p.i.) and lower stimulation index values coincided with the parasite burden peak. Western-blot analysis detected antibodies during the 1st week p.i. and the number of recognized proteins increased with the time of infection, reaching a maximum at the peak parasite burden. Histopathology revealed hypoplasia in spleen white pulp and the liver showed a periportal infiltration of inflammatory cells and small granulomas, becoming increasingly more severe as the infection developed. Both organs exhibited a secondary amyloid deposition at the end of the experiment, especially the spleen. In this study, progressive visceral disease was observed as in natural human and canine infections; however, the incubation period was longer in the promastigote than in the amastigote infection.Parasites L. infantum zymodeme MON-1 (MCAN/PT/94/IMT 205) promastigotes were obtained from the liver and the spleen of infected hamsters cultured in Novy-MacNeal-Nicolle (NNN) medium. The parasites were maintained at 24°C in HO-MEM medium (Gibco BRL) supplemented with 10% heat-inactivated fetal calf serum Parasitol

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

“…Compared with the LDU index, the qPCR also demonstrated a higher parasite burden in the liver and spleen in the animals infected with the Wild strain by the IC route. These results confirm those obtained by other authors that evaluated parasitism in spleen and liver by others methods [6], [7], [21], [22].…”

“…Our results are consistent with Requena et al [7] who associated the strong humoral response in hamsters experimentally infected with L. infantum to the presence of clinical signs and elevated parasite tissue density. Other studies have shown a relationship between parasite load and high antibody titers in hamsters experimentally infected with different forms and species of Leishmania [6], [21], [22], [29]. Thus, similarly to human and canine LV, the evaluation of anti- Leishmania antibody is an important tool in monitoring the establishment of infection in the hamster model.…”

“…Given the number of amastigotes per 1000 nuclei cells but without consideration of the organ weight, the spleen appeared to be more parasitized than the liver. Higher splenic parasitism has been shown by many other researchers in studies that used hamsters experimentally infected by L. infantum and/or L. donovani with different infective forms (amastigote and promastigote) and routes of inoculation [6], [7], [19], [21], [22], [47]. The discrepancy in results presented by others authors can be explained because of the use of limiting dilution for assessing parasitism in spleen and liver without including organ weight in the calculation of parasite load.…”

“…The quantification of parasitism in hamsters experimentally infected with L. infantum or L. donovani is generally determined by classical methods, such as limiting dilution and/or by Leishman Donovan units (LDU) according to Stauber [19]; however, these methods exhibit low sensitivity [20], [21], [22]. The development of a technique that allows quantifying the amastigotes in different parasitized tissues is extremely important to evaluate the impact of parasitism in experimentally infected hamsters.…”

Mechanisms of resistance and susceptibility to experimental visceral leishmaniosis: BALB/c mouse versus syrian hamster model

“…The pathological features reported during VL include hypoplasia of the white pulp in the spleen, hepatic granulomas and the deposition of a secondary amyloid substance both in the spleen and the liver [32,33]. Also, other studies of active VL have reported that infected hamsters develop glomerulonephritis associated with deposition of immunoglobulins and parasite antigens (immune complexes) in the kidneys.…”