Delivery of Echinococcus granulosus antigen EG95 to mice and sheep using recombinant vaccinia virus

Trained immunity: a cutting edge approach for designing novel vaccines against parasitic diseases?

The preventive situation of parasitosis, a global public health burden especially for developing countries, is not looking that good. Similar to other infections, vaccines would be the best choice for preventing and controlling parasitic infection. However, ideal antigenic molecules for vaccine development have not been identified so far, resulting from the complicated life history and enormous genomes of the parasites. Furthermore, the suppression or down-regulation of anti-infectious immunity mediated by the parasites or their derived molecules can compromise the effect of parasitic vaccines. Comparing the early immune profiles of several parasites in the permissive and non-permissive hosts, a robust innate immune response is proposed to be a critical event to eliminate the parasites. Therefore, enhancing innate immunity may be essential for designing novel and effective parasitic vaccines. The newly emerging trained immunity (also termed innate immune memory) has been increasingly recognized to provide a novel perspective for vaccine development targeting innate immunity. This article reviews the current status of parasitic vaccines and anti-infectious immunity, as well as the conception, characteristics, and mechanisms of trained immunity and its research progress in Parasitology, highlighting the possible consideration of trained immunity in designing novel vaccines against parasitic diseases.

The Recombinant Eg.P29-Mediated miR-126a-5p Promotes the Differentiation of Mouse Naive CD4+ T Cells via DLK1-Mediated Notch1 Signal Pathway

Cystic echinococcosis (CE) is a zoonotic parasitic disease spread worldwide caused by Echinococcus granulosus (Eg), which sometimes causes serious damage; however, in many cases, people are not aware that they are infected. A number of recombinant vaccines based on Eg are used to evaluate their effectiveness against the infection. Our previous report showed that recombinant Eg.P29 (rEg.P29) has a marvelous immunoprotection and can induce Th1 immune response. Furthermore, data of miRNA microarray in mice spleen CD4⁺ T cells showed that miR-126a-5p was significantly elevated 1 week after immunization by using rEg.P29. Therefore, in this perspective, we discussed the role of miR-126a-5p in the differentiation of naive CD4⁺ T cells into Th1/Th2 under rEg.P29 immunization and determined the mechanisms associated with delta-like 1 homolog (DLK1) and Notch1 signaling pathway. One week after P29 immunization of mice, we found that miR-126a-5p was significantly increased and DLK1 expression was decreased, while Notch1 pathway activation was enhanced and Th1 response was significantly stronger. The identical conclusion was obtained by overexpression of mmu-miR-126a-5p in primary naive CD4⁺ T cells in mice. Intriguingly, mmu-miR-126a-5p was significantly raised in serum from mice infected with protoscolex in the early stages of infection and markedly declined in the late stages of infection, while has-miR-126-5p expression was dramatically reduced in serum from CE patients. Taken together, we show that miR-126a-5p functions as a positive regulator of Notch1-mediated differentiation of CD4⁺ T cells into Th1 through downregulating DLK1 in vivo and in vitro. Hsa-miR-126-5p is potentially a very promising diagnostic biomarker for CE.

The Immunization of Protoscolices P29 DNA Vaccine on Experimental Cystic Echinococosis in Balb/c Mice

PURPOSE

Cystic Echinococosis is one of the important parasitic diseases that is considered as a problem economics and health in many parts of the world. Many efforts have been performed for controlling the disease in the world. To reach a reliable vaccine against Cystic Echinococosis is one of the important duty of governments. Several antigen of hydatid cyst for vaccine candidate have been evaluated. In this study, P-29 antigen has been used for this purpose.

METHODS

E.g P29 antigen was cloned in Escherichia coli and transfected into the Chinese hamster ovary cell for antigen proliferation and used for vaccination in Balb/c mice. The recombinant antigen E.g-29 was shown using Western blot test. Two dilution of DNA vaccine (pCEgP-29) including 50 µg/100 µl and 100 µg/100 µl were prepared. Twenty four Balb/C male 6-8 week mouse were divided in 4 groups. The groups were included in 2 vaccination groups (pcEg.P29 50 µg/100 µl and 100 µg/100 µl dilution) as immunized groups and 2 groups of plasmid and PBS as control. The mice were injected intramuscularly 3 times with 2 weeks interval. After 3 weeks from last injection, all groups were challenged intraperitonealy with 2000 protoscolices. After 5 months, the mice were euthanized by ketamine/xylasine injection and number, size, and weight of cysts were recorded.

RESULTS

Immunization rate was up to 93% in vaccinated group when compared with the control group.

CONCLUSION

The results of this study showed that rEg.P29 could be considered as an effective vaccine for controlling of E. granulosus prevalence in intermediated host.

Promising Technologies in the Field of Helminth Vaccines

Helminths contribute a larger global burden of disease than both malaria and tuberculosis. These eukaryotes have caused human infections since before our earliest recorded history (i.e.: earlier than 1200 B.C. for Schistosoma spp.). Despite the prevalence and importance of these infections, helminths are considered a neglected tropical disease for which there are no vaccines approved for human use. Similar to other parasites, helminths are complex organisms which employ a plethora of features such as: complex life cycles, chronic infections, and antigenic mimicry to name a few, making them difficult to target by conventional vaccine strategies. With novel vaccine strategies such as viral vectors and genetic elements, numerous constructs are being defined for a wide range of helminth parasites; however, it has yet to be discussed which of these approaches may be the most effective. With human trials being conducted, and a pipeline of potential anti-helminthic antigens, greater understanding of helminth vaccine-induced immunity is necessary for the development of potent vaccine platforms and their optimal design. This review outlines the conventional and the most promising approaches in clinical and preclinical helminth vaccinology.

Current situation and future prospects of Echinococcus granulosus vaccine candidates: A systematic review

Cystic echinococcosis is a worldwide zoonotic disease, represents a threat for livestock and humans, manifests as a quiescent, subclinical and chronic hydatid cyst infection. The disease imposes high expenditures and economic losses in medical and veterinary. Prophylactic vaccination would be one of the effective preventive health care against echinococcosis. During the last decades, many studies have characterized the protective antigens of Echinococcus granulosus and their role in immunization of various animal host species. Herein, we aimed to systematically evaluate and represent the best antigens as possible vaccine candidates for cystic echinococcosis. Data were systematically searched from five databases including ProQuest, PubMed, Scopus, ScienceDirect and Web of Science, up to 1 February 2020. Two reviewers independently screened and assessed data extraction and quality assessment. A total of 47 articles were eligible for inclusion criteria in the current study. The most common antigens used for vaccination against E. granulosus were EG95 and antigen B. Freund's adjuvant and Quil A have been predominantly utilized. In addition, regarding the antigen delivery, animal models, measurement of immune responses and reduction in hydatid cyst have been discussed in the text. The data demonstrated that DNA vaccines with antigen B and recombinant protein vaccines based on EG95 antigen have the best results and elicited protective immune responses.

Immunoprotection of recombinant Eg.P29 against Echinococcus granulosus in sheep

OBJECTIVE

This study aims to investigate the immunoprotection of recombinant Eg.P29 (rEg.P29) vaccine and analyze the underlying mechanism in sheep.

METHODS

Three groups of male sheep were immunized subcutaneously with rEg.P29 and PBS, Freund's complete adjuvant as controls, respectively. After prime-boost vaccination, the sheep were challenged with encapsulated Echinococcus granulosus eggs. The percentage of protection in sheep was determined 36 weeks after the infection. Humoral immune response was analyzed for specific IgG, IgG1, IgG2, IgM and IgE levels. Moreover, cytokines including interferon (IFN)-γ, interleukin (IL)-2, IL-4,and IL-10 were also evaluated.

RESULTS

Immunization with rEg.P29 induced protective immune responses up to 94.5 %, compared with immunoadjuvant group. The levels of specific IgG, IgG1, IgG2, and IgE as well as IFN-γ, IL-2, and IL-4 significantly increased after two immunizations (P < 0.05); however, the levels of IgM and IL-10 did not show difference.

CONCLUSION

rEg.P29 showed Immunoprotection and induced Th1 and Th2 immune responses; hence, rEg.P29 is a potential vaccine for E. granulosus infection.