Investigating associations between intestinal alterations and parasite load according to Bifidobacterium spp. and Lactobacillus spp. abundance in the gut microbiota of hamsters infected by Leishmania infantum

Abstract

BACKGROUND Visceral leishmaniasis (VL) is a tropical neglected disease with high associated rates of mortality. Several studies have highlighted the importance of the intestinal tract (IT) and gut microbiota (GM) in the host immunological defense. Data in the literature on parasite life cycle and host immune defense against VL are scarce regarding the effects of infection on the IT and GM. OBJECTIVES This study aimed to investigate changes observed in the colon of Leishmania infantum-infected hamsters, including alterations in the enteric nervous system (ENS) and GM (specifically, levels of bifidobacteria and lactobacilli). METHODS Male hamsters were inoculated with L. infantum and euthanised at four or eight months post-infection. Intestines were processed for histological analysis and GM analysis. Quantitative polymerase chain reaction (qPCR) was performed to quantify each group of bacteria: Bifidobacterium spp. (Bf) and Lactobacillus spp (LacB). FINDINGS Infected hamsters showed histoarchitectural loss in the colon wall, with increased thickness in the submucosa and the mucosa layer, as well as greater numbers of intraepithelial lymphocytes. Forms suggestive of amastigotes were seen inside mononuclear cells. L. infantum infection induced changes in ENS, as evidenced by increases in the area of colonic enteric ganglia. Despite the absence of changes in the levels of Bf and LacB during the course of infection, the relative abundance of these bacteria was associated with parasite load and histological alterations. MAIN CONCLUSIONS Our results indicate that L. infantum infection leads to important changes in the colon and suggest that bacteria in the GM play a protective role.

A New Target Organ of Leishmania (Viannia) braziliensis Chronic Infection: The Intestine

“…Ganglionitis and periganglionitis have been reported in hamsters infected with L. (V.) braziliensis (Santos et al, 2018b) and L. infantum (Passos et al, 2020), but our article is the first to numerically and morphometrically evaluate the neurons of both ENS plexuses. The infiltration of immune cells in the ganglia can lead to neuronal degeneration and consequently cause cell dysfunction and loss (De Giorgio et al, 2004).…”

“…To evaluate ileum morphology and cellularity, sets with semiserial 5 μm transverse histological sections were prepared and stained using different techniques. Histopathological evaluations and morphometric analyses of ileal walls, enterocytes, and intraepithelial lymphocytes (IELs) were performed on sets stained with hematoxylin and eosin (HE) (Santos et al, 2018b;Passos et al, 2020). Goblet cells producing different mucins were counted in Alcian blue pH 1.0 (AB 1.0), Alcian blue pH 2.5 (AB 2.5), and periodic acid-Schiff (PAS) stained sets (1; Santos et al, 2018b).…”

“…The heights and widths of villi were measured using the same images. The base, middle, and apex of villi were measured first, and then the average of these values resulted in the final value (Santos et al, 2018b;Passos et al, 2020). For each animal, the heights and widths of 80 enterocytes and their respective nuclei were measured in images captured with a 100x objective lens (Santos et al, 2018b).…”

“…The effect of Leishmania infection in the gastrointestinal tract is the topic of studies that evaluated different segments of the intestine of dogs (Figueiredo et al, 2014;Silva et al, 2016;Silva et al, 2018) and rodents (Souza et al, 2019;Lewis et al, 2020;Passos et al, 2020) with visceral leishmaniasis (VL). In human VL, the presence of amastigote forms in intestinal tissues may be related to episodes of diarrhea (Baba et al, 2006;Soria Loṕez et al, 2016;Raina et al, 2017) or not (Chattopadhyay et al, 2020).…”

Avaliação dos desfechos de infecção in vitro e em modelo experimental no hamster com diferentes isolados clínicos de Leishmania infantum

“…Na medicina veterinária a coprofagia é causada por verminose, estresse, doenças metabólicas e alimentação restritiva, inadequada e/ou carente de nutrientes (MEYER, et al, 2014;EDWARD, 2020). Visto que, em infecções com L. infantum a mudança da microbiota intestinal pode estar associada a carga parasitária e alterações histológicas (PASSOS et al, 2020;LEWIS et al, 2020), hipotetizamos que mudanças ocorridas na microbiota devido ao parasitismo intestinal com translocação bacteriana para o fígado e perda de peso progressiva durante a LV causando o comportamento acima descrito dos hamsters devido o comprometimento na metabolização hepática, tal relação será investigada por outro estudo realizado pelo nosso grupo. Adicionalmente, a copofragia pode estar relacionada, também, ao estresse causado pelo desconforto dos sinais clínicos e pelos distúrbios metabólitos devido às alterações hepáticas e má absorção de nutrientes pelo intestino decorrentes da LV.…”