Cystic echinococcosis: Development of an intermediate host rabbit model for using in vaccination studies.

The aims of this study were an establishment of the domestic rabbit as an intermediate host for cystic echinococcosis (CE) and to evaluate the potency of the crude germinal layer and the protoscoleces antigens to protect against the CE. Firstly; Two groups of white Newzeland rabbits were infected orally either by 5000 active oncospheres or viable protoscoleces separately. After 20 weeks, the slaughtered rabbits showed the presence of hydatid cysts at different internal organs. Molecular detection of the resulted cysts was conducted. Secondly; 27 rabbits were divided into nine groups (n = 3). Groups 1 and 2 were immunized with the crude germinal layer antigen while the groups 3 and 4 were immunized with the crude protoscoleces antigen. Groups 5 and 6 received the adjuvant mineral oil. Groups 7 and 8 were used as positive control. The last 9 group was kept as a negative control. The obtained results showed a significant high protection percentage of 83.4% and high antibody titer was recorded in groups that received the crude germinal layer antigen comparing with the groups that immunized with the crude protoscoleces antigen as their protection percentage was 66.7% with lower IgG response. In conclusion, the domestic rabbits could be used as a laboratory model for CE. Developing of the germinal layer antigen is more immunogenic than the protoscoleces one and could be used as a promising vaccine. Attention should be directed towards the existing rabbit in the environment adjacent to infected dogs as it could be a part of Echinococcus life cycle.

Prevention and control of cystic echinococcosis.

Human cystic echinococcosis (hydatid disease) continues to be a substantial cause of morbidity and mortality in many parts of the world. Elimination is difficult to obtain and it is estimated that, using current control options, achieving such a goal will take around 20 years of sustained efforts. Since the introduction of current (and past) hydatid control campaigns, there have been clear technological improvements made in the diagnosis and treatment of human and animal cystic echinococcosis, the diagnosis of canine echinococcosis, and the genetic characterisation of strains and vaccination against Echinococcus granulosus in animals. Incorporation of these new measures could increase the efficiency of hydatid control programmes, potentially reducing the time required to achieve effective prevention of disease transmission to as little as 5-10 years.

Nitric oxide-mediated immunosuppression following murine Echinococcus multilocularis infection.

In some parasitic infections immunosuppression is a prominent characteristic of the host-parasite interplay. We have used a murine alveolar echinococcosis (AE) model in susceptible C57BL/6 mice to document a suppressed splenocyte proliferative response to concanavalin A (Con A) at the early (1-month) stage and to Echinococcus multilocularis-crude antigen (Emc-antigen) at the late (4-6-month) stage of chronic infection. Despite proliferative suppression, splenic cytokine production [interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma)] in response to Con A or Emc-antigen stimulation was not suppressed at 1 month postinfection (p.i.). Infection resulted in a strong Mac-1+ cell infiltration of the peritoneal cavity and spleen. Peritoneal cells (PEC) from mice infected at the 1-month stage were rich in macrophages and expressed significantly higher levels of transcripts for the inflammatory cytokine IL-1beta and for tumour necrosis factor-alpha and inducible nitric oxide synthase (iNOS), when compared with PEC from non-infected control mice. Conversely, the IL-10 transcript level remained low and did not change during infection. Spleen cells supplemented with PEC from infected mice induced a marked increase in the levels of nitrite in response to Con A and Emc-antigen stimulation, and also a complete suppression of splenic proliferation. The spleen cells from late-stage infected mice expressed only background levels of IL-10 but greatly increased levels of iNOS, when compared with normal spleen cells. This observation correlated with the immunosuppression demonstrated at the late stage of murine AE. Furthermore, the suppressed splenic proliferative responses observed at the early and late stage were reversed to a large extent by the addition of NG-monomethyl-l-arginine and partially by anti-IFN-gamma. Thus, our results demonstrated that the immunosuppression observed in chronic AE was not primarily dependent on IL-10 but rather on nitric oxide production by macrophages from infected animals.

Identification and characterization of myophilin, a muscle-specific antigen of Echinococcus granulosus.

A muscle-specific gene of Echinococcus granulosus has been identified and characterized. A lambda gt11 clone (10P1), containing an incomplete copy of the gene, was originally isolated from a larval E. granulosus cDNA library by serum antibodies from dogs infected with the parasite. The full-length cDNA sequence was obtained by PCR amplification of cDNA from an adult E. granulosus lambda gt22A library. Southern blot analysis indicated the presence of the gene as a single copy in the genome of E. granulosus and also detected homologous genes in genomic DNA of E. multilocularis and Taenia saginata. The 21.2-kDa protein deduced from the complete cDNA sequence contains two regions of 12 amino acids with similarity to the EF-hand motif of calcium binding proteins. Antibodies raised against the purified 10P1-GST fusion protein detected a 22-kDa antigen in the E. granulosus developmental stages examined. Immunoelectron microscopy localized the native protein in the muscle of the parasite. The amino-acid sequence of the E. granulosus protein shows significant homology to the muscle proteins mp20 of Drosophila melanogaster, chicken SM22 alpha and mammalian calponin, and also to the neuronal protein NP25 of rats. A conserved carboxy-terminal motif of 17 amino acids is present in all the homologous proteins and is proposed to be the characteristic feature of a novel protein family. The term myophilin is proposed for the E. granulosus protein due to its localization and homology to other muscle proteins.

Activation of normal murine B cells by Echinococcus granulosus.

Echinococcus granulosus protoscolex (PSC) infection of BALB/c mice led, after 4 days, to raised numbers of cells forming plaques with trinitrophenyl-treated sheep red cells and bromelain-treated mouse red cells. The findings were similar in athymic and euthymic CBA mice. Activation of B cells was accompanied by secretion of immunoglobulin, as indicated by the reverse plaque technique. In addition, co-culture of PSC with the 7OZ/3 pre-B-cell led to the induction of differentiation, resulting in the expression of surface immunoglobulin (Ig). It is concluded that E. granulosus is a polyclonal activator of B cells inducing both transformation and differentiation, and that the effect is thymus-independent.