Foie et maladies parasitaires

Surveillance on the status of immune cells after Echinnococcus granulosus protoscoleces infection in Balb/c mice

Background

Cystic echinococcosis is a global parasitic disease caused by infection with Echinococcus granulosus larvae with potentially life-threatening complications in humans. To date, the status of the immune cells believed to be associated with the pathogenicity of E. granulosus infection has not been demonstrated clearly.

Methodology/Principal Findings

In this study, we developed a multiplex flow cytometry assay to investigate the systemic immune status of innate and adaptive immunity at 30, 180, 360 days post-infection (dpi) in mice infected with E. granulousus. At 30 dpi, an increase in the number of CD11b⁺ and CD11c⁺ antigen-presenting cells (APCs) was observed. This was accompanied by the slight down-regulated expression of the co-stimulatory molecule MHC-II, indicating the impairment of APCs in early infection through the release of secretory-excretory products. In all infected groups, we observed a significant increase in innate immune cells, including APCs and GR-1⁺ cells, and a dramatic increase in the myeloid-derived suppressor cells (MDSC) expressing CD11b⁺/GR-1⁺. Moreover, the upregulation of the activated markers CD69, CD44, CD40L, and the downregulation of CD62L were observed in the CD4⁺ and CD8⁺ T cells following infection. Regulatory T cells expressing CD4⁺/CD25⁺/FoxP₃⁺ increased significantly over the course of infection.

Conclusions

Our findings demonstrate that the microenvironment in the peripheral immune system after E. granulosus infection changes in subtle but detectably ways, especially during the persistent period of infection. We found that T cells were activated following infection, but observed that the significant increase of immunosuppressive cells such as MDSC and Treg cells could inhibit T cell response to E. granulosus antigens. We suggest these cells may play a neglected but key role in the downregulation of the immune response in long-term parasitic infection. Understanding the basic functions and temporal interactions of these immunosuppressive cells will pave the way for new strategies of parasite vaccine design.

Imaging aspects and non-surgical interventional treatment in human alveolar echinococcosis

Alveolar echinococcosis (AE) of the liver caused by the metacestode of the fox tapeworm Echinococcus multilocularis is characterized by a multivesicular structure surrounded by an extensive fibro-inflammatory host reaction. The lesions behave like a slow-growing liver cancer, without sharp limits between the parasitic tissue and the liver parenchyma. Invasion of biliary and vascular walls is another hallmark of this severe disease. Moreover, the poor vascularization of the parasitic mass often leads to necrosis in the central part of the lesion. This explains why liver abscess due to superimposed bacterial infection of the necrotic area may occur in this disease. Currently, a range of imaging techniques can be used at the different stages of management of AE. For diagnosis, ultrasonography remains the first line examination. For a more accurate disease evaluation, aiming to guide the surgical strategy, computerized tomography, Magnetic Resonance (MR) imaging, including cholangio-MR imaging are of importance, providing useful complementary information. More recently, Positive-Emission Tomography using [18F] fluoro-deoxyglucose has been developed for the follow-up of inoperable AE patients under long-term benzimidazoles therapy. This approach seems very promising to assess inflammatory activity and thereby to indirectly depict parasitic activity. Non-surgical interventional procedures, mainly percutaneous biliary and/or centro-parasitic abscesses drainages, are currently a major aspect in the care of incurable AE patients and have largely contributed to the improvement of survival in this situation during the past 20 years. They may also be used as a bridge before a curative surgical procedure in symptomatic patients presenting a life-threatening bacterial and/or fungal infection. It is also very useful in inoperable patients to overcome similar infectious episodes.