Diagnostic Efficacy of a Recombinant Cysteine Protease of Spirometra erinacei Larvae for Serodiagnosis of Sparganosis

The mature domain of a cysteine protease of Spirometra erinacei plerocercoid larva (i.e., sparganum) was expressed in Escherichia coli, and its value as an antigen for the serodiagnosis of sparganosis was investigated. The recombinant protein (rSepCp-1) has the molecular weight of 23.4 kDa, and strongly reacted with the sparganum positive human or mice sera but not with negative sera by immunoblotting. ELISA with rSepCp-1 protein or sparganum crude antigen (SeC) was evaluated for the serodiagnosis of sparganosis using patient's sera. The sensitivity and specificity of ELISA using rSepCp-1 protein were 95.0% (19/20) and 99.1% (111/112), respectively. In contrast, the sensitivity and specificity of ELISA with SeC were 100% (20/20) and 96.4% (108/112), respectively. Moreover, in experimentally infected mice, the sensitivity and specificity of both ELISA assays were 100% for the detection of anti-sparganum IgG. It is suggested that the rSepCp-1 protein-based ELISA could provide a highly sensitive and specific assay for the diagnosis of sparganosis.

Expression of Translationally Controlled Tumor Protein (TCTP) Gene of Dirofilaria immitis Guided by Transcriptomic Screening

Dirofilaria immitis (heartworm) infections affect domestic dogs, cats, and various wild mammals with increasing incidence in temperate and tropical areas. More sensitive antibody detection methodologies are required to diagnose asymptomatic dirofilariasis with low worm burdens. Applying current transcriptomic technologies would be useful to discover potential diagnostic markers for D. immitis infection. A filarial homologue of the mammalian translationally controlled tumor protein (TCTP) was initially identified by screening the assembled transcriptome of D. immitis (DiTCTP). A BLAST analysis suggested that the DiTCTP gene shared the highest similarity with TCTP from Loa loa at protein level (97%). A histidine-tagged recombinant DiTCTP protein (rDiTCTP) of 40 kDa expressed in Escherichia coli BL21 (DE3) showed immunoreactivity with serum from a dog experimentally infected with heartworms. Localization studies illustrated the ubiquitous presence of rDiTCTP protein in the lateral hypodermal chords, dorsal hypodermal chord, muscle, intestine, and uterus in female adult worms. Further studies on D. immitis-derived TCTP are warranted to assess whether this filarial protein could be used for a diagnostic purpose.

Serodiagnosis of Toxocariasis by ELISA Using Crude Antigen of Toxocara canis Larvae

Toxocariasis is a worldwide zoonosis caused by larvae of ascarid nematodes of dogs or cats, Toxocara canis or T. cati. Diagnosis of human toxocariasis currently relies on serology that uses T. canis excretory-secretory antigen to detect specific IgG antibodies by ELISA. We investigated the serodiagnostic efficacy of ELISA using crude antigen of T. canis larvae (TCLA). Serum specimens of 64 clinically confirmed toxocariasis, 115 healthy controls, and 119 other tissue-invading helminthiases were screened by ELISA using TCLA. The ELISA using TCLA showed 92.2% (59/64 patient samples) sensitivity and 86.6% (103/119) specificity. Its positive diagnostic predictivity was 78.7% and negative predictivity was 97.8%. No serum of healthy controls reacted but that of anisakiasis (45.5%), gnathostomiasis (19.2%), clonorchiasis (15.8%), sparganosis (11.1%), and cysticercosis (6.3%) cross-reacted. Immunoblot analysis on TCLA recognized antigenic proteins of 28- and 30-kDa bands in their dominant protein quantity and strong blotting reactivity. The present results indicate that the ELISA using our TCLA antigen is acceptable by the sensitivity and specificity for serodiagnosis of human toxocariasis. ELISA with TCLA is recommended to make differential diagnosis for patients with any sign of organ infiltration and eosinophilia.

Electron Microscopy of the Separated Outer Tegument of the Sparganum and Its Antigenicity

The author reported previously on separation of the outer tegument of the spargana (plerocercoids of Spirometra mansoni) using high concentration of urea solution. To determine which layer of the tegument is separated by this method, an electron microscopic analysis has been processed in this study. It was confirmed that the basement layer of the tegument is separated from the parenchyme of the sparganum. In addition, the antigenicity of the separated outer tegument against the human sparganosis patient sera was evaluated. Numerous antigenic proteins, including 16 and 55 kDa proteins, were noticed in the separated tegument; however, there were no diagnostic 31/36 kDa molecules in this tegument. The molecules reactive with the patient sera in the tegument are to be characterized in future studies.

Seroprevalence of Antibodies against Anisakis simplex Larvae among Health-Examined Residents in Three Hospitals of Southern Parts of Korea

The present study was performed to estimate the seroprevalence of larval Anisakis simplex infection among the residents health-examined in 3 hospitals in southern parts of Korea. A total of 498 serum samples (1 serum per person) were collected in 3 hospitals in Busan Metropolitan city, Masan city, and Geoje city in Gyeongsangnam-do (Province) and were examined by IgE-ELISA and IgE-western blotting with larval A. simplex crude extract and excretory-secretory products (ESP). The prevalence of antibody positivity was 5.0% and 6.6% with ELISA against crude extracts and ESP, respectively. It was also revealed that infection occurred throughout all age groups and higher in females than in males. A specific protein band of 130 kDa was detected from 10 patients with western blot analysis against crude extract and ESP among those who showed positive results by ELISA. Our study showed for the first time the seroprevalence of anisakiasis in Korea. The allergen of 130 kDa can be a candidate for serologic diagnosis of anisakiasis.

Immunoblot Patterns of Taenia asiatica Taeniasis

Differential diagnosis of Taenia asiatica infection from other human taeniases by serology has been tested. An enzyme-linked immunoelectrotransfer blot (EITB) was applied to subjected human sera and tapeworm materials. Thirty-eight proteins reactive to serum IgG were observed between 121 and 10 kDa in adult worms, and more than 22 serum-reactive components between 97 kDa and 21.5 kDa were observed in eggs of T. asiatica. Antigens of adult T. asiatica revealed immunoblot bands between 120 and 21.5 kDa against T. asiatica infected sera. Antigens of adult Taenia saginata revealed 110-100, 66, 58-56, and 46 kDa immunoblot bands against T. asiatica infected sera. Antigens of adult Taenia solium also revealed 99-97, 68-66, and 46 kDa bands against T. asiatica infected sera. The immunoblot band of 21.5 kDa exhibited specificity to T. asiatica.

Detection of anti-Haemonchus contortus antibodies in sheep by dot-ELISA with immunoaffinity purified fraction of ES antigen during prepatency.

Haemonchosis is a very common disease in small ruminants caused by H. contortus, a blood sucking parasite causing anaemia that may be fatal particularly to young animals. Therefore, detection of the infection during prepatent period is important for early treatment. Excretory-Secretory (ES) protein of H. contortus was purified through immunoaffinity chromatography. Dot -ELISA was performed with crude ES antigen as well as immunoaffinity purified fraction (F-1) with experimental and natural sera of sheep infected with H. contortus. Solid dot formation took place with 4 day, 1, 2 and 3 weeks post infection sera. Dot formation did not take place with negative control serum and uninfected control animal serum. When crude ES antigens was reacted to natural sheep sera having H. contortus infection, 60% sera samples showed solid dot formation whereas in F-1 fraction 75% of the sera samples showed solid dot indicating purified fraction was a more potent antigen. Crude ES and F-1 were also fractionated through SDS-PAGE. ES antigen revealed polypeptides in the range of 10 to 200 kDa of which 26, 32, 60 and 120 kDa were found more prominent. F-1 fraction on SDS-PAGE analysis revealed only four polypeptides of 26, 32, 60, and 120 of which 60 and 120 kDa were found to be most prominent. Results indicate that the purified fraction of ES antigen may be utilized for early diagnosis of haemonchosis. Further studies on cross antigenicity of this fraction with other nematode and trematode needs to be conducted.

Identification of 38kDa Brugia malayi microfilarial protease as a vaccine candidate for lymphatic filariasis.

A FPLC purified 38kDa protease (Bm mf S-7) isolated from B. malayi microfilarial soluble antigen was identified. It showed pronounced reactivity with sera collected from 'putatively immune' asymptomatic and amicrofilaraemic individuals residing in an endemic area for bancroftian filariasis. Further the immune protective activity of Bm mf S-7 antigen was evaluated in susceptible hosts, jirds (Meriones unguiculatus) against B. malayi filarial infection. The antigen showed 89% cytotoxicity against mf and 87-89% against infective (L3) larvae in in vitro antibody dependent cellular cytotoxicity Assay (ADCC) and in situ micropore chamber methods. Bm mf S-7 immunized jirds after challenge infection showed 81.5% reduction in the adult worm burden. The present study has shown that, the 38kDa microfilarial proteases (Bm mf S-7) could stimulate a strong protective immune response against microfilariae and infective larvae in jird model to block the transmission of filariasis. Analysis of IgG subclasses against Bm mf S-7 revealed a significant increase in IgG2 and IgG3 antibodies in endemic normals. Lymphocyte proliferation to Bm mf S-7 was significantly high in endemic normal group as compared to that in clinical and microfilarial carriers. Significantly enhanced levels of IFN-gamma in the culture supernatant of PBMC of endemic normals followed by stimulation with Bm mf S-7 suggest that the cellular response in this group is skewed towards Th 1 type.

Comparative diagnostic potentiality of ELISA and dot-ELISA in prepatent diagnosis of experimental Fasciola gigantica infection in cattle.

A glycoprotein (27 kDa) was isolated from crude somatic antigen of Fasciola gigantica by two steps affinity chromatography and was used in early detection of experimental fasciolosis in cattle by indirect ELISA and in dot-ELISA formats. Although, anti-27 kDa antibodies could be detected after 3 weeks post infection (WPI) by dot - ELISA which was one week later than indirect ELISA. The test, dot-ELISA, was more convenient in field application. By the test (dot-ELISA) the infection could be equally detected in animals infected with 100, 200 and 300 metacercariae of F. gigantica with high sensitivity. Further, the antigen (27 kDa) was not found to react with goat sera infected with Paramphistomum epiclitum, which are giving strong reaction to homologous immature and mature fluke antigens of P. epiclitum.

Modification of carbohydrate compositions of 31/36 kDa proteins of plerocercoids (sparganum) of Spirometra mansoni grown in different intermediate hosts

We purified specific 31/36 kDa antigenic molecules from sparganum in different intermediate hosts (snakes and mice) and analyzed their monosaccharide compositions. Compositional analysis showed that glucose and mannose concentrations were 2-3 fold higher in the 31/36 kDa molecule purified from snakes than those from mice. This result implies that antigenic glycoproteins of sparganum from snakes might be modified in mammalian sparganosis with respect to their carbohydrate composition.

Recent advances in serodiagnosis for cysticercosis.

Neurocysticercosis (NCC) caused by infection with the larval stage of Taenia solium is an important cause of neurological disease worldwide. Up to the present, many studies on characterizing species-specific antigens of T. solium have been done and several high quality antigens for serodiagnosis are available. Hence the research on serodiagnosis has been shifted to the next phase, stable production of diagnostic antigens using molecular techniques. In order to establish an enzyme-linked immunosorbent assay (ELISA) using recombinant proteins, we carried out molecular cloning and identified four diagnostic antigen candidates (Ag1, Ag1V1, Ag2, and Ag2V1). Recombinant proteins, except Ag2V1, were successfully expressed using an Escherichia coli expression system. Immunoblot analysis using NCC patient sera detected recombinant proteins. But as reactivity to rAg1 was too weak, Ag1 was not suitable for the immunodiagnosis antigen. Therefore Ag1V1 and Ag2 were chosen for ELISA antigens and Ag1V1/Ag2 chimeric protein was expressed. Of 49 serum samples from NCC patients confirmed to be seropositive by immunoblot analysis, 44 (89.7%) were positive by ELISA. Serum samples from patients with other parasitic infections did not recognized Ag1V1/Ag2 chimeric protein. Ag1V1/Ag2 chimeric protein obtained in this study is of value for differential immunodiagnosis.

Immune response of electroeluted detergent soluble 29 kDa antigen from Setaria digitata (Von Linstow).

Filariasis is one of the typical parasitic infections which cause immune suppression during the course of infection in both humans and experimental animals. A 29 kDa protein isolated from detergent soluble antigen of S. digitata showed maximum inhibition of cell mediated immune response. The heat inactivated 29 kDa protein was found to be devoid of property of suppression of immune response in the host. Histological study of spleen of BALB/C mice immunized with 29 kDa protein showed changes in regions of spleen such as follicle, trabeculae, capsule, reticuloendothelial cells and eosinophils. The 29 kDa protein, the most reactive of the detergent soluble proteins produced partial suppression of immune response, thereby contributing to the factors responsible for the survival of filarial parasites in hosts.

Immunodiagnostic moieties in somatic and excretory/secretory antigens of Fasciola gigantica.

Immunodiagnostic potential fractions in fluke antigens and excretory/secretory (E/S) antigen of F. gigantica have been identified using double immunodiffusion (DID), immunoelectrophoresis (IEP) and sodium dodecyl sulphate (SDS) PAGE electrophoresis. Hyperimmunised rabbits elicited considerable level of antibody response with few precipitin lines showing reaction of identity in DID suggesting presence of some common fractions in all antigens. Mature fluke somatic (MFSAg) and immature fluke somatic (IMFSAg) antigens showed exactly similar pattern of precipitin lines in both DID and IEP. Antibodies to experimentally infected rabbits with F. gigantica were also detected by DID using MFSAg and E/S antigens at 4 weeks post infection. However, out of 6-7 fractions obtained from Sephadex G-200 column chromatography in MFSAg and IMFSAg antigens only F3, F4 and F5 along with E/S antigen were able to detect antibodies by DID. Mature fluke and E/S antigen separated out in 9 bands in the range of 12 to 95 kDa and 5 bands in the range of 12 to 29 kDa respectively of which proteins of molecular weight 12, 15, 18, 28 and 29 kDa were common in both antigens. Therefore, it appears that immunodiagnostic fractions of antigens may be present in between 12 and 29 kDa.