Prevention and Immunotherapy of Secondary Murine Alveolar Echinococcosis Employing Recombinant EmP29 Antigen

Abstract

Alveolar echinococcosis (AE) is caused by infection with the larval stage of the tapeworm Echinococcus multilocularis. An increasing understanding of immunological events that account for the metacestode survival in human and murine AE infection prompted us to undertake explorative experiments tackling the potential of novel preventive and/or immunotherapeutic measures. In this study, the immunoprotective and immunotherapeutic ability of recombinant EmP29 antigen (rEmP29) was assessed in mice that were intraperitoneally infected with E. multilocularis metacestodes. For vaccination, three intraperitoneal injections with 20μg rEmP29 emulsified in saponin adjuvants were applied over 6 weeks. 2 weeks after the last boost, mice were infected, and at 90 days post-infection, rEmP29-vaccinated mice exhibited a median parasite weight that was reduced by 75% and 59% when compared to NaCl- or saponin–treated control mice, respectively. For immunotherapeutical application, the rEmP29 (20μg) vaccine was administered to experimentally infected mice, starting at 1 month post-infection, three times with 2 weeks intervals. Mice undergoing rEmP29 immunotherapy exhibited a median parasite load that was reduced by 53% and 49% when compared to NaCl- and saponin–treated control mice, respectively. Upon analysis of spleen cells, both, vaccination and treatment with rEmP29, resulted in low ratios of Th2/Th1 (IL-4/IFN-γ) cytokine mRNA and low levels of mRNA coding for IL-10 and IL-2. These results suggest that reduction of the immunosuppressive environment takes place in vaccinated as well as immunotreated mice, and a shift towards a Th1 type of immune response may be responsible for the observed increased restriction of parasite growth. The present study provides the first evidence that active immunotherapy may present a sustainable route for the control of AE.

Immune Exhaustion of T Cells in Alveolar Echinococcosis Patients and Its Reversal by Blocking Checkpoint Receptor TIGIT in a Murine Model

“…Such observations are consistent with the effect of TIGIT on the generation of mature immunoregulatory dendritic cells; its role on the inhibition of TNF‐α secretion is also consistent with the dramatic effect of TNF gene deletion shown on E. multilocularis infection susceptibility in mice . Our results are also in line with observations that anti‐PD‐L1 mAb or recombinant EmP29 antigen administration result in a change of Treg and/or T h 2/T h 1 ratio, which may be responsible for partial restriction of metacestode growth . However, in most studies, positive results of immunotherapy were observed when the biotherapeutic agent was administered at time of infection, thus preventing the establishment of the metacestode, which is not applicable to the clinical situation.…”

“…(40) Our results are also in line with observations that anti-PD-L1 mAb or recombinant EmP29 antigen administration result in a change of Treg and/or T h 2/T h 1 ratio, which may be responsible for partial restriction of metacestode growth. (8,41) However, in most studies, positive results of immunotherapy were observed when the biotherapeutic agent was administered at time of infection, thus preventing the establishment of the metacestode, which is not applicable to the clinical situation. Our results revealed a reduction in the number and size of hepatic infectious lesions with metacestode structures after an anti-TIGIT treatment that was initiated 12 weeks after the beginning of infection, an observation that was rarely reported after chemotherapy or immunotherapy in studies in AE patients and mouse models.…”

Immunoregulation in larval Echinococcus multilocularis infection

“…Furthermore, EmTIP evoked a strong release of IFN‐γ by CD4 + T cells, hence suggesting that the secretion of this factor as a result of its role in parasite development could ‘secondarily’ induce a potentially protective Th1 response . The most recently identified EmP29 was shown to induce nonspecific in‐vitro T‐lymphocyte proliferation and a lower ratio of Th2/Th1 (IL‐4/IFN‐γ), cytokine mRNA and low mRNA levels of IL‐10 and IL‐2 . Vaccination and active immunotherapy employing rEmP29 antigen had a significant inhibitory effect on the secondary infection with E. multilocularis metacestodes in mice, and yielded thus a reduced parasite infection intensity (load) when compared to mock‐treated control animals .…”

“…The most recently identified EmP29 was shown to induce nonspecific in‐vitro T‐lymphocyte proliferation and a lower ratio of Th2/Th1 (IL‐4/IFN‐γ), cytokine mRNA and low mRNA levels of IL‐10 and IL‐2 . Vaccination and active immunotherapy employing rEmP29 antigen had a significant inhibitory effect on the secondary infection with E. multilocularis metacestodes in mice, and yielded thus a reduced parasite infection intensity (load) when compared to mock‐treated control animals .…”

Proteomic Analysis of Excretory-Secretory Products of Mesocestoides corti Metacestodes Reveals Potential Suppressors of Dendritic Cell Functions

“…corti endophilin is considerably similar to Echinococcus spp. P29 proteins, which were shown to be highly efficient host protective antigens when used as vaccines [ 51 , 52 ]. A similar role for M .…”