Taenia solium, a causative agent of taeniasis and cysticercosis, has evolved a repertoire of lipid uptake mechanisms. Proteome analysis of T. solium excretory-secretory products (TsESP) identified 10 kDa proteins displaying significant sequence identity with cestode hydrophobic-ligand-binding-proteins (HLBPs). Two distinct 362- and 352-bp-long cDNAs encoding 264- and 258-bp-long open reading frames (87 and 85 amino acid polypeptides) were isolated by mining the T. solium expressed sequence tags and a cDNA library screening (TsHLBP1 and TsHLBP2; 94% sequence identity). They clustered into the same clade with those found in Moniezia expansa and Hymenolepis diminuta. Genomic structure analysis revealed that these genes might have originated from a common ancestor. Both the crude TsESP and bacterially expressed recombinant proteins exhibited binding activity toward 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS), which was competitively inhibited by oleic acid. The proteins also bound to cis-parinaric acid (cPnA) and 16-(9-anthroyloxy) palmitic acid (16-AP), but showed no binding activity against 11-[(5-dimethylaminonaphthalene-1-sulfonyl) amino] undecanoic acid (DAUDA) and dansyl-DL-α-aminocaprylic acid (DACA). Unsaturated fatty acids (FAs) showed greater affinity than saturated FAs. The proteins were specifically expressed in adult worms throughout the strobila. The TsHLBPs might be involved in uptake and/or sequestration of hydrophobic molecules provided by their hosts, thus contributing to host-parasite interface interrelationships.

Cyst fluid (CF) of Taenia solium metacestode (TsM) is an important source of serodiagnostic antigens. We have investigated the molecular characteristics of the 120 kDa protein complex in TsM CF purified by fast performance liquid chromatography. The structure of the purified protein was characterized by a variety of proteomic analyses. The protein was found to consist of 2 major components of 42-46 and 22-28 kDa, and shared 3 subunits of 14, 16 and 18 kDa. The 42-46 kDa component was determined to contain 3 additional subunits of 22, 28 and 38 kDa. These 6 subunits were shown to originate from either the 14 or 18 kDa precursor. We assessed the antibody reactivity of the native protein, its individual subunits and the recombinant 14 and 18 kDa proteins, and found that the 120 kDa protein, particularly 14 and 18 kDa subunits revealed high reliability for differentiation of active and mixed stage NC from chronic NC. The subunits of the 120 kDa protein complex identified herein represent some of the low-molecular weight glycoproteins which have been described in several previous studies. Recognizing and understanding the structural and immunological relationship of these proteins will facilitate the development of new serodiagnostic assays.

Phospholipid hydroperoxide glutathione peroxidase (PHGPx; GPx4) plays unique roles in the protection of cells against oxidative stress by catalysing reduction of lipid hydroperoxides. We characterized 2 novel GPx genes from a lung fluke, Paragonimus westermani (designated PwGPx1 and PwGPx2). These single copy genes spanned 6559 and 12 371 bp, respectively, and contained each of 5 intervening introns. The PwGPx2 harboured a codon for Sec and a Sec insertion sequence motif. Proteins encoded by the Paragonimus genes demonstrated a primary structure characteristic to the PHGPx family, including preservation of catalytic and glutathione-binding domains and absence of the subunit interaction domain. Expression of PwGPx1 increased gradually as the parasite matured, whereas that of PwGPx2 was temporally regulated. PwGPx2 was expressed at the basal level from the metacercariae to the 3-week-old juveniles; however, the expression was significantly induced in the 7-week-old immature worms and reached a plateau in the 12-week-old adults and eggs. PwGPx1 and PwGPx2 were largely localized in vitellocytes within vitelline glands and eggs. Oxidative stress-inducible paraquat, juglone and H2O2 substantially augmented the PwGPx1 and PwGPx2 expressions in viable worms by 1.5- to 11-fold. Our results strongly suggested that PwGPxs may actively participate in detoxification of oxidative hazards in P. westermani.