An Echinococcus multilocularis Antigen B3 Proteoform That Shows Specific Antibody Responses to Active-Stage Alveolar Echinococcosis

Abstract

e Alveolar echinococcosis (AE), caused by the Echinococcus multilocularis metacestode, represents one of the most frequently fatal zoonoses. Early diagnosis significantly reduces morbidity and mortality associated with AE. Diagnosis of AE largely depends on a combination of imaging and serological tests due to its minimal clinical manifestations. Several antigens derived from the whole worm and protoscolex have been targeted for AE serodiagnosis, while the antigenic properties of E. multilocularis hydatid fluid (EmHF) are unclear. We observed two AE-specific 6-and 8-kDa antigen proteoforms through an immunoproteome array of the EmHF. We identified these proteins as representing an E. multilocularis antigen B3 (EmAgB3) isoform, and the proteins were shown to be encoded by the same gene. We cloned the gene and expressed the recombinant EmAgB3 protein (rEmAgB3) in Escherichia coli. rEmAgB3 exhibited sensitivity of 90.9% (80/88 cases) and specificity of 98.5% (597/606 samples) by immunoblotting. The positive and negative predictive values were 89.9% and 98.6%, respectively. The protein did not show antibody responses to 33 AE sera collected during posttreatment follow-up monitoring. Mouse sera experimentally infected with AE protoscoleces began to demonstrate specific antibody responses to native and recombinant EmAgB3 6 months after infection. At that stage, fully mature metacestode vesicles that harbored the brood capsule, primary cell, and protoscolex were observed within an AE mass(es). The response declined along with worm degeneration. Our results demonstrate that the immune responses to this EmAgB3 isoform were highly correlated with worm viability accompanied with AE progression. rEmAgB3 is a promising biomarker for serological assessment of AE patients.A lveolar echinococcosis (AE), an infection caused by Echinococcus multilocularis metacestodes, is one of the most frequently chronic and fatal zoonoses (1-3). Epidemiological evidence has demonstrated that 0.5 to 6 of 100,000 inhabitants are infected in areas of endemicity of Europe and Central Asia (4, 5). In the Tibetan and Qinghai plateaus in China, the population at risk of infection is estimated to encompass 60 million (6).Two kinds of hosts are intimately involved in the life cycle of E. multilocularis. Domestic and wild canids (definitive hosts) harbor the adult tapeworm in their intestines. The worms produce numerous eggs, which pass out of the host with gravid segments. When wild rodents and humans (intermediate hosts) take in the eggs, oncospheres are activated in the small intestine; they then penetrate the intestinal wall and enter the circulation. They primarily lodge in the liver and grow slowly into multivesiculated metacestode vesicles, in which brood capsules, primary cells, and protoscoleces develop, resulting in AE (1, 7). AE usually presents with a complex of nonspecific liver manifestations that mimic cystadenoma, hepatocellular carcinoma, and liver cirrhosis (8, 9).Diagnosis of AE largely depends on a combination of imaging and serologi...

Spatiotemporal Expression Patterns and Antibody Reactivity of Taeniidae Endophilin B1

“…(several antigen B isoforms) (19,20,37,38), except for a few entities in the case of AE (37). Those proteins are rapidly drained and absorbed with parasite involution and result in minimal antibody responses in chronic cases (19,20,23,39,40).…”

“…AE cases were ultrasonographically diagnosed and grouped into early invasive versus advanced stages (22). The diagnoses were serologically confirmed by immunoblotting with recombinant EmAgB3 (20). NC cases were diagnosed by neuroimaging scans with concomitant positive antibody responses against a recombinant chimeric antigen, assessed by immunoblotting and an enzymelinked immunosorbent assay (ELISA) (23).…”

“…Sera from mice that had been experimentally infected with 1,000 viable AE protoscoleces were analyzed. Mice (5 to 7 per group) were sacrificed serially at 1, 3, 6, 9, and 14 months after infection (20). Sera from swine (n ϭ 3) that had been experimentally infected with 100,000 viable T. solium eggs were serially collected at 1, 2, 3, 4, 6, 8, and 12 months postinfection (25).…”

“…The species were identified by observing specific bands for T. solium (474 bp), T. saginata (629 bp), and T. asiatica (706 bp) by multiplex PCR (18). CE2 cysts and AE masses were collected from naturally infected sheep and experimentally infected mice in Xining (Qinghai Province, China) (19,20). E. granulosus and E. multilocularis adults were collected during necropsies of stray dogs (Chengdu, Qinghai Province, China).…”

“…In clinical practice, several different antigens specific to the active stages of the respective diseases might be superior for initial diagnosis, because some regimens can differentially diagnose NC, CE, and AE with high sensitivity and specificity (19,20,23,(36)(37)(38). TsMEnodoB1 and/or Echinococcus orthologs may be beneficial for follow-up monitoring of patients to evaluate treatment efficacy (16,17,42).…”