The effect of reinfection with Neodiplostomum seoulensis on the histopathology and activities of brush border membrane bound enzymes in the rat small intestine

Dose-response effects of multiple Ascaris suum exposures and their impact on lung protection during larval ascariasis

BACKGROUND

Human ascariasis is the most prevalent geohelminthiasis worldwide, affecting approximately 446 million individuals. In regions with endemic prevalence, the majority of infected adults are frequently exposed to the parasite and tend to have a low parasite load. Further studies are necessary to provide more evidence on the dynamics of infection and to elucidate the possible mechanisms involved in regulating protection, especially during the acute phase, also known as larval ascariasis. The aim of this study is to compare the impact of lung function between single and multiple infections in a murine model.

METHODS

We infected BALB/c mice considering the frequency of exposures: single-exposure-SI; twice-exposures-RE 2x and thrice-exposures-RE 3x, and considering the doses of infection: 25 eggs-RE 25; 250 eggs-RE 250 and 2,500 eggs-RE 2500, followed by infection challenge with 2,500 eggs. From this, we evaluated: parasite burden in lungs, cellular and humoral response, histopathological and physiological alterations in lungs.

RESULTS

The main results showed a reduction of parasite burden in the reinfected groups compared to the single-infected group, with protection increasing with higher exposure and dose. Furthermore, the RE 250 group exhibited a decrease of parasite burden close to RE 2500, but with less tissue damage, displaying the most favorable prognosis among the reinfected groups.

CONCLUSION

Our research indicates a dose-dependent relationship between antibody production and the intensity of the immune response required to regulate the parasite burden.

Echinostomes and Other Intestinal Trematode Infections

Intestinal trematodes are among the most common types of parasitic worms. About 76 species belonging to 14 families have been recorded infecting humans. Infection commonly occurs when humans eat raw or undercooked foods that contain the infective metacercariae. These parasites are diverse in regard to their morphology, geographical distribution and life cycle, which make it difficult to study the parasitic diseases that they cause. Many of these intestinal trematodes have been considered as endemic parasites in the past. However, the geographical limits and the population at risk are currently expanding and changing in relation to factors such as growing international markets, improved transportation systems, new eating habits in developed countries and demographic changes. These factors make it necessary to better understand intestinal trematode infections. This chapter describes the main features of human intestinal trematodes in relation to their biology, epidemiology, host-parasite relationships, pathogenicity, clinical aspects, diagnosis, treatment and control.

Immunological underpinnings of Ascaris infection, reinfection and co-infection and their associated co-morbidities

Human ascariasis is the most common and prevalent neglected tropical disease and is estimated that ~819 million people are infected around the globe, accounting for 0.861 million years of disability-adjusted life years in 2017. Even with the existence of highly effective drugs, the constant presence of infective parasite eggs in the environment contribute to a high reinfection rate after treatment. Due to its high prevalence and broad geographic distribution Ascaris infection is associated with a variety of co-morbidities and co-infections. Here, we provide data from both experimental models and humans studies that illustrate how complex is the interaction of Ascaris with the host immune system, especially, in the context of reinfections, co-infections and associated co-morbidities.

Multiple Exposures to Ascaris suum Induce Tissue Injury and Mixed Th2/Th17 Immune Response in Mice

Ascaris spp. infection affects 800 million people worldwide, and half of the world population is currently at risk of infection. Recurrent reinfection in humans is mostly due to the simplicity of the parasite life cycle, but the impact of multiple exposures to the biology of the infection and the consequences to the host's homeostasis are poorly understood. In this context, single and multiple exposures in mice were performed in order to characterize the parasitological, histopathological, tissue functional and immunological aspects of experimental larval ascariasis. The most important findings revealed that reinfected mice presented a significant reduction of parasite burden in the lung and an increase in the cellularity in the bronchoalveolar lavage (BAL) associated with a robust granulocytic pulmonary inflammation, leading to a severe impairment of respiratory function. Moreover, the multiple exposures to Ascaris elicited an increased number of circulating inflammatory cells as well as production of higher levels of systemic cytokines, mainly IL-4, IL-5, IL-6, IL-10, IL-17A and TNF-α when compared to single-infected animals. Taken together, our results suggest the intense pulmonary inflammation associated with a polarized systemic Th2/Th17 immune response are crucial to control larval migration after multiple exposures to Ascaris.

Immunology and pathology of intestinal trematodes in their definitive hosts

This review examines the significant literature on the immunology and pathology of intestinal trematodes in their definitive hosts. We emphasize information on selected species in six families for which the literature on these topics is extensive. The families are Brachylaimidae, Diplostomidae, Echinostomatidae, Gymnophallidae, Heterophyidae, and Paramphistomidae. For most of these families, coverage is considered under the following headings: (i) background; (ii) pathology of the infection; (iii) immunology of the infection; (iv) immunodiagnosis; and (v) human infection. Some of these heading have been subdivided further, based on the literature available on a particular topic. Following this coverage, we include a final section on the important topical literature on selected trematodes in families other than the six mentioned above.

Expression patterns of proliferating cell nuclear antigen in the small intestine of mice infected with Metagonimus yokogawai and Metagonimus Miyata type

Genus Metagonimus has been a subject of taxonomic debates for several years. In morphological aspects, M. yokogawai has been thought to have three subtypes, namely Yokogawa type (M. yokogawai in strict sense), Miyata type and Koga type, But differences in the intestinal pathology induced by these subtypes have not been studied yet. In this study we compared the pathological reactions induced by M. yokogawai and Metagonimus Miyata type using proliferating cell nuclear antigen (PCNA) index. Metacercariae (Mc) of M. yokogawai were collected by artificial digestion of Plecoglossus altivelis and Mc of Metagonimus Miyata type were collected from Zacco platypus. Three hundreds Mc of each species were infected orally to ICR mice. The mice were sacrificed at 3, 6, 10, 16 and 23 days after infection and the small intestines were resected into three portions (proximal, middle, and distal). Immunohistochemical staining for PCNA was done using PC-10 (DAKO-PCNA, CA, USA). The PCNA indices in M. yokogawai infected group on the 6th and 23rd day after infection were lower than in the control and Miyata type infected groups (p < 0.05) from all of the three intestinal regions. On the other hand, the control group and Metagonimus Miyata type infected group did not make any differences in PCNA indices. The villus/crypt (V/C) ratio was also decreased significantly in M. yokogawai infected mice but not in Metagonimus Miyata type infected ones. It is suggested that M. yokogawai induce villous atrophy through a decrease in the cell proliferation at the crypt. The results of this study suggested that M. yokogawai induce more serious intestinal pathology than Metagonimus Miyata type.

IgA response in mice infected with Neodiplostomum seoulensis

To observe the production of IgA in Balb/c mice with neodiplostomiasis, 20 mice were infected with each 200 metacercariae of Neodiplostomum seoulenis. Sera and the duodenums were obtained 3, 7, 14, 28 days post-infection (PI) from five mice each group. Neodiplostomum specific IgA in serum by the enzyme-linked immunosorbent assay increased from 7 days PI and persisted till 28 days PI. Immunohistochemistry for IgA was done with sections of the duodenum. The IgA-positive reaction was generally seen in the lamina propria and submucosa. Some of epithelial cells were positive at 7 and 14 days PI. The present finding showed that Neodiplostomun specific IgA antibody increased in serum and that there was local reaction of IgA in the mucosa and submucosa of the duodenum but not directly related with worm expulsion.