Wenbao Zhang

Concepts in Immunology and Diagnosis of Hydatid Disease

SUMMARY Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and E. multilocularis, which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Both CE and AE are both serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review discusses new concepts and approaches in the immunology and diagnosis of CE, but comparative reference has also been made to AE infection and to earlier pivotal studies of both diseases. The review considers immunity to infection in the intermediate and definitive hosts, innate resistance, evasion of the immune system, and vaccination of intermediate and definitive hosts, and it particularly emphasizes procedures for diagnosis of CE and AE, including the value of immunodiagnostic approaches. There is also discussion of the new advances in recombinant and related DNA technologies, especially application of PCR, that are providing powerful tools in the fields of vaccinology and molecular diagnosis of echinococcosis.

The genome of the hydatid tapeworm Echinococcus granulosus

Cystic echinococcosis (hydatid disease), caused by the tapeworm E. granulosus, is responsible for considerable human morbidity and mortality. This cosmopolitan disease is difficult to diagnose, treat and control. We present a draft genomic sequence for the worm comprising 151.6 Mb encoding 11,325 genes. Comparisons with the genome sequences from other taxa show that E. granulosus has acquired a spectrum of genes, including the EgAgB family, whose products are secreted by the parasite to interact and redirect host immune responses. We also find that genes in bile salt pathways may control the bidirectional development of E. granulosus, and sequence differences in the calcium channel subunit EgCavβ1 may be associated with praziquantel sensitivity. Our study offers insights into host interaction, nutrient acquisition, strobilization, reproduction, immune evasion and maturation in the parasite and provides a platform to facilitate the development of new, effective treatments and interventions for echinococcosis control.

Diagnosis, treatment, and management of echinococcosis

#### Summary points Echinococcosis (hydatid disease) is caused by the larvae of dog and fox tapeworms (cestodes) of the genus Echinococcus (family Taeniidae).1 2 3 This zoonosis is characterised by long term growth of metacestode (hydatid) cysts in humans and mammalian intermediate hosts. The two major species that infect humans are E granulosus and E multilocularis , which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE). A few reported cases of polycystic echinococcosis in Central and South America are caused by E vogeli and E oligarthrus .2 w1 w2 The clinical potential of two other Echinococcus species ( E shiquicus and E felidis ) is unknown.1 2 #### Sources and selection criteria We obtained information from personal reference archives, personal experience, and extensive literature searches of the PubMed and Cochrane databases. We sourced English language papers that were fully published mainly between 2000 and March 2012 using appropriate index terms. …

Mechanisms of Immunity in Hydatid Disease: Implications for Vaccine Development

The Echinococcus organisms, the cause of echinococcosis (hydatid disease), are parasitic helminths with life cycles involving a carnivorous definitive host (usually dog or fox) and an intermediate host (human, ungulate, or rodent). They are complex multicellular pathogens that, despite being under constant barrage by the immune system, are able to modulate antiparasite immune responses and persist and flourish in their mammalian hosts. Understanding how the immune system deals with these parasites is a major challenge. Recent application of modern molecular and immunological approaches has revealed insights on the nature of immune responses generated during the course of hydatid infection, although many aspects of the Echinococcus-host interplay remain unexplored. This review summarizes current understanding of the immunology of echinococcosis, indicates areas where information is lacking, and shows how knowledge of host protective immunity has been translated into the design and development of anti-Echinococcus vaccines for application in intermediate hosts.

Immunology and immunodiagnosis of cystic echinococcosis: an update.

Cystic echinococcosis (CE) is a cosmopolitan zoonosis caused by the larval cystic stage of the dog tapeworm Echinococcus granulosus. This complex multicellular pathogen produces various antigens which modulate the host immune response and promote parasite survival and development. The recent application of modern molecular and immunological approaches has revealed novel insights on the nature of the immune responses generated during the course of a hydatid infection, although many aspects of the Echinococcus-host interplay remain unexplored. This paper summarizes recent developments in our understanding of the immunology and diagnosis of echinococcosis, indicates areas where information is lacking, and suggests possible new strategies to improve serodiagnosis for practical application.

Epidemiology and control of echinococcosis in central Asia, with particular reference to the People's Republic of China

At least 270 million people (58% of the total population) are at risk of cystic echinococcosis (CE) in Central Asia including areas of Mongolia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, Afghanistan, Iran, Pakistan and western China. The annual surgical incidence rate in Uzbekistan and Tadjikistan has been estimated to be as high as 25-27 cases/100,000 with the highest prevalence reaching 10% (range from 0.8 to 11.9%) in some Tibetan communities in western China. Echinococcus transmission in the region is largely associated with social factors including limited community knowledge of echinococcosis, small-scale household animal production, home killing of livestock, and the feeding of dogs with uncooked offal. Alveolar echinococcosis (AE) is also endemic in Central Asia and is recognized as a major problem in some Tibetan communities with up to 6% of villagers infected in some villages. In western China, 5-30% of the population are seropositive against E. granulosus antigens, indicating that a large number of individuals have been exposed to the parasite. Although echinococcosis control programs have been initiated in some countries in Central Asia, control efforts are generally fragmented and uncoordinated. Monthly deworming of dogs with praziquantel (PZQ), as a key measure to control the Echinococcus parasites, has been used in western China. However, the approach has proven difficult in local semi-nomadic communities. Additional control measures including health education, domestic livestock animal treatment/vaccination and dog vaccination are needed in CE-endemic areas to accelerate progress.

Proteomic characterisation of Echinococcus granulosus hydatid cyst fluid from sheep, cattle and humans

The hydatid cyst fluid (HCF) of Echinococcus granulosus is a complex biological mixture containing a wide range of proteins of both parasite and host origin. Using a combination of in- and off-gel protein fractionation techniques and tandem mass spectrometry 130 HCF proteins were identified from fertile cysts of sheep and human origin and infertile cysts from cattle. Forty-eight proteins were of parasite origin including Antigen 5 and Antigen B--the most abundant parasite proteins, thioredoxin, low-density lipoprotein receptors, cyclophilin and ferritin. Across the three host species the identified HCF proteins were broadly similar although, based on spectral counts, three proteins, including an antigen B isoform, were more abundant in sheep HCF compared with the fluids of cattle and human origin. Eighty-two host proteins were identified in HCF from the three species. Host plasma proteins were the most abundant, although approximately thirty of the host proteins that were identified are not considered constituents of plasma. The identification of parasite heat shock proteins and annexin A13 exclusively in infertile cysts, along with an increased spectral count for cathepsin B, supports the hypothesis of increased cellular stress and apoptosis as the cause of their infertility.

Cloning and Characterisation of Schistosoma japonicum Insulin Receptors

Background Schistosomes depend for growth and development on host hormonal signals, which may include the insulin signalling pathway. We cloned and assessed the function of two insulin receptors from Schistosoma japonicum in order to shed light on their role in schistosome biology. Methodology/Principal Findings We isolated, from S. japonicum, insulin receptors 1 (SjIR-1) and 2 (SjIR-2) sharing close sequence identity to their S. mansoni homologues (SmIR-1 and SmIR-2). SjIR-1 is located on the tegument basal membrane and the internal epithelium of adult worms, whereas SjIR-2 is located in the parenchyma of males and the vitelline tissue of females. Phylogenetic analysis showed that SjIR-2 and SmIR-2 are close to Echinococcus multilocularis insulin receptor (EmIR), suggesting that SjIR-2, SmIR-2 and EmIR share similar roles in growth and development in the three taxa. Structure homology modelling recovered the conserved structure between the SjIRs and Homo sapiens IR (HIR) implying a common predicted binding mechanism in the ligand domain and the same downstream signal transduction processing in the tyrosine kinase domain as in HIR. Two-hybrid analysis was used to confirm that the ligand domains of SjIR-1 and SjIR-2 contain the insulin binding site. Incubation of adult worms in vitro, both with a specific insulin receptor inhibitor and anti-SjIRs antibodies, resulted in a significant decrease in worm glucose levels, suggesting again the same function for SjIRs in regulating glucose uptake as described for mammalian cells. Conclusions Adult worms of S. japonicum possess insulin receptors that can specifically bind to insulin, indicating that the parasite can utilize host insulin for development and growth by sharing the same pathway as mammalian cells in regulating glucose uptake. A complete understanding of the role of SjIRs in the biology of S. japonicum may result in their use as new targets for drug and vaccine development against schistosomiasis.

Diagnosis of Cystic Echinococcosis, Central Peruvian Highlands

High prevalence was confirmed by ultrasonography, radiography, and 2 serologic tests, although usefulness of serologic testing in the field was limited.

Vaccination of Dogs against Echinococcus granulosus the Cause of Cystic Hydatid Disease in Humans

Dogs are pivotal in Echinococcus granulosus transmission to humans, and dog vaccination provides a very practical and cost-effective prevention strategy. We vaccinated dogs with soluble native proteins isolated from protoscoleces of E. granulosus and induced significant suppression of worm growth and egg production. Accordingly, we tested for vaccine efficacy using recombinant proteins derived from a developmentally regulated gene family (egM) specifically expressed in mature adult E. granulosus worms. Three egM genes--egM4, egM9, and egM123--were subcloned into an expression vector that expressed the molecules as soluble glutathione S-transferase (GST) fusion proteins in Escherichia coli. The 3 fusion proteins were purified for dog vaccination trials (3 doses of 80 microg/protein/dog) in which the dogs were challenged and then necropsied 45 days after infection. Compared with worms in the control dogs that received GST, the 3 recombinant proteins induced a very high level of protection (97%-100%) in terms of suppression of worm growth and, especially, of egg development and embryogenesis. We have thus shown that vaccination of the dog host against E. granulosus is feasible when recombinant proteins are used. Because the egg stage is crucial in the echinococcal life cycle, successful suppression of egg development by vaccination would halt transmission to intermediate hosts, thereby effecting long-term control.