Diagnostic value of glycoprotein band patterns of three serologic enzyme-linked immunoelectrotransfer blot assays for neurocysticercosis

The enzyme-linked immunoelectrotransfer blot (EITB) assay to detect antibodies in serum is a complementary tool for the diagnosis of neurocysticercosis (NCC). Presence of at least one glycoprotein band corresponding to a Taenia solium (T. solium) antigen indicates a positive result; however, EITB assays have multiple glycoprotein bands, and previous work has suggested that band patterns may have additional diagnostic value. We included 58 participants with a definitive diagnosis of NCC who received care at the Instituto Nacional de Neurología y Neurocirugía in Mexico City. Three different EITB tests were applied to participants' serum samples (LDBio, France; US Centers for Disease Control and Prevention [CDC]; and Instituto de Diagnóstico y Referencia Epidemiológicos [InDRE]). There was substantial variability in specific glycoprotein band patterns among the three assays. However, in age- and sex-adjusted logistic regression models, the number of glycoprotein bands was positively associated with the presence of vesicular extraparenchymal cysts (InDRE adjusted odds ratio [aOR] 1.60 p < 0.001; CDC aOR 6.31 p < 0.001; LDBio aOR 2.45 p < 0.001) and negatively associated with the presence of calcified parenchymal cysts (InDRE aOR 0.63 p < 0.001; CDC aOR 0.25 p < 0.001; LDBio aOR 0.44 p < 0.001). In a sensitivity analysis also adjusting for cyst count, results were similar. In all three EITB serum antibody tests, the number of glycoprotein bands consistently predicted cyst stage and location, although magnitude of effect differed.

Immunodiagnosis of human neurocysticercosis: comparative performance of serum diagnostic tests in Mexico

Immunodiagnosis has a supportive role in the diagnosis of neurocysticercosis (NCC). The aim of this study was to compare the validity of seven immunodiagnostic tests among serum samples from 58 patients with NCC, 26 patients with neurological diseases other than NCC, and 15 healthy controls. One test for viable parasite detection (HP10 antigen assay) and six for antibody detection were evaluated. For the entire sample, sensitivities ranged from 55.2% (NOVALISA) to 81.0% (enzyme-linked immunosorbent assay [ELISA] Taenia solium antibody), with the sensitivity of the latter test significantly higher than that of the in-house ELISA Taenia crassiceps, NOVALISA, enzyme-linked immunoelectrotransfer blot (EITB) CDC, and HP10. Overall, specificities were high, ranging from 85.4% (ELISA Ts) to 97.1% (NOVALISA), with no statistically significant differences. Detection of HP10 antigen was significantly associated with the presence of vesicular parasites. The simple and low-cost ELISA Taenia solium antibody Ab instead of EITB is recommended to support NCC diagnosis in both rural and hospital settings in Mexico.

Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea

Background

Onchocerciasis, also known as river blindness, is a parasitic disease. More than 99 percent of all cases occur in Africa. Bioko Island (Equatorial Guinea) is the only island endemic for onchocerciasis in the world. Since 2005, when vector Simulium yahense was eliminated, there have not been any reported cases of infection. This study aimed to demonstrate that updated WHO criteria for stopping mass drug administration (MDA) have been met.

Methodology/Principal findings

A cross-sectional study was conducted from September 2016 to January 2017. Participants were 5- to 9-year-old school children. Onchocerciasis/lymphatic Filariasis (LF, only in endemic districts) rapid diagnostic tests (RDTs) were performed. Blood spots were collected from RDT positive children and 10 percent of the RDT negatives to determine Ov16 and Wb123 IgG4 antibodies through enzyme-linked immunosorbent assay (ELISA). Skin snips were collected from RDT positives. Filarial detection was performed by PCR in positives and indeterminate sera. Black fly collection was carried out in traditional breeding sites. A total of 7,052 children, ranging from 5 to 9 years of age, were included in the study. Four children (0.06%) were Ov16 IgG4 RDT positives, but negative by ELISA Ov16, while 6 RDT negative children tested positive by ELISA. A total of 1,230 children from the Riaba and Baney districts were tested for LF. One child was Wb123 RDT positive (0.08%), but ELISA negative, while 3 RDT negative children were positive by Wb123 ELISA. All positive samples were negative by PCR for onchocerciasis and LF (in blood spot and skin snip). All fly collections and larval prospections in the traditional catching and prospection sites were negative.

Conclusions/Significance

WHO criteria have been met, therefore MDA in Bioko Island can be stopped. Three years of post-treatment surveillance should be implemented to identify any new occurrences of exposure or infection.

Onchocerciasis, commonly called river blindness, is a chronic parasitic disease particularly prevalent in Africa. It is transmitted through the bites of infected Simulium blackflies. Onchocerciasis is endemic in Equatorial Guinea. Huge achievements have been made in human and vector control during the last two decades, especially on Bioko Island. Eliminating onchocerciasis transmission on Bioko is feasible given its isolation from other landmasses, which also reduces the risk of reinvasion by the disease vector. Recently updated WHO guidelines for stopping mass drug administration (MDA) and verifying elimination of human onchocerciasis (2016) established a new critical threshold to verify elimination of onchocerciasis transmission based on novel serological tests. We applied these techniques in a representative sample of 5- to 9-year-old school children. An entomological assessment was also carried out. We found no evidence of current infection or recent transmission. There was no evidence of onchocerciasis vectors, and our results from the sample population meet the current WHO serologic criteria for stopping MDA. Based on these results, we recommended to the Ministry of Health and Social Welfare of Equatorial Guinea that MDA on Bioko Island be stopped and that 3 years of post-treatment surveillance should be undertaken to identify any new occurrences of exposure or infection.

Transplastomic plants yield a multicomponent vaccine against cysticercosis

Low cost vaccines against cysticercosis are needed to fight this parasitosis, especially in developing countries. Herein polycistron arrangements were designed to accomplish the simultaneous expression of multiple protective antigens from Taenia solium in the plant cell as an attractive biofactory and delivery vehicle of vaccines. Transplastomic plants carrying synthetic polycistrons were able to simultaneously express the KETc1, KETc7, KETc12, GK1, and TSOL18/HP6-Tsol antigens; which retained their antigenicity and ability to induce humoral responses in BALB/c mice. These clones may be useful for the production of low-cost cysticercosis vaccine prototypes.

Dermatological manifestations in onchocerciasis: A retrospective study of 400 imported cases

INTRODUCTION

Onchocerciasis is caused by Onchocerca volvulus and mainly leads to pruritus and skin and visual disorders, including blindness. Seventeen million people are infected in 38 countries; 31 of these are in sub-Saharan Africa, six in Latin America and one on the Arabian Peninsula. More than 99% of cases occur in sub-Saharan Africa where 120 million people are at risk of infection. Eye disorders have been well-documented; however, skin disorders have not been described accurately. The objective of our study was to describe the epidemiology, main skin manifestations and treatment of imported onchocerciasis.

MATERIAL AND METHODS

A retrospective study was thus conducted by analysing the main demographic, clinical and treatment data regarding a cohort of 400 patients attending a reference clinical unit over a 17-year period.

RESULTS

Most patients were female (55%) with mean age 37.5±16.7 years. All the migrants came from sub-Saharan countries. The most frequently occurring dermatological symptom was pruritus. Ivermectin had been used as first-line therapy and adverse reactions had been described in 11 patients (3.2%).

CONCLUSIONS

The results indicate the fact that there should be a clinical suspicion of onchocerciasis regarding immigrants from endemic areas having skin lesions compatible with the disease's profile or asymptomatic patients having eosinophilia or unexplained high IgE. Moreover, skin snips from the buttocks region were very fruitful and treatment with ivermectin was seen to be safe. This is the largest case series regarding imported onchocerciasis described up to the present time.

Cystic Echinococcosis Epidemiology in Spain Based on Hospitalization Records, 1997-2012

BACKGROUND

Cystic echinococcosis (CE) is a parasitic disease caused by the tapeworm Echinococcus granulosus. Although present throughout Europe, deficiencies in the official reporting of CE result in under-reporting and misreporting of this disease, which in turn is reflected in the wrong opinion that CE is not an important health problem. By using an alternative data source, this study aimed at describing the clinical and temporal-spatial characteristics of CE hospitalizations in Spain between 1997 and 2012.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a retrospective descriptive study using the Hospitalization Minimum Data Set (CMBD in Spanish). All CMBD's hospital discharges with echinococcosis diagnosis placed in first diagnostic position were reviewed. Hospitalization rates were computed and clinical characteristics were described. Spatial and temporal distribution of hospital discharges was also assessed. Between 1997 and 2012, 14,010 hospitalizations with diagnosis of CE were recorded, 55% were men and 67% were aged over 45 years. Pediatric hospitalizations occurred during the whole study period. The 95.2% were discharged at home, and only 1.7% were exitus. The average cost was 8,439.11 €. The hospitalization rate per 100,000 per year showed a decreasing trend during the study period. All the autonomous communities registered discharges, even those considered as non-endemic. Maximum rates were reached by Extremadura, Castilla-Leon and Aragon. Comparison of the CMBD data and the official Compulsory Notifiable Diseases (CND) reports from 2005 to 2012 showed that official data were lower than registered hospitalization discharges.

CONCLUSIONS

Hospitalizations distribution was uneven by year and autonomous region. Although CE hospitalization rates have decreased considerably due to the success of control programs, it remains a public health problem due to its severity and economic impact. Therefore, it would be desirable to improve its oversight and surveillance, since officially reported data are underestimating the real burden of CE in Spain.

Evidence for Suppression of Onchocerciasis Transmission in Bioko Island, Equatorial Guinea

Onchocerciasis or "river blindness" is a chronic parasitic neglected tropical disease which is endemic both in mainland and insular Equatorial Guinea. We aim to estimate the current epidemiological situation of onchocerciasis in Bioko Island after vector elimination in 2005 and more than sixteen years of Community Directed Treatment with Ivermectin (CDTI) by using molecular and serological approaches for onchocerciasis diagnosis. A community-based cross-sectional study was carried out in Bioko Island from mid-January to mid-February 2014. A total of 544 study participants were recruited. A complete dermatological examination was performed and three skin snips were performed in every participant for parasitological and molecular assessments. Blood spots were also taken for determination of Ov16 IgG4 antibodies trough an “in-house” ELISA assay. Overall, we found 15 out of 522 individuals suffering any onchocerciasis specific cutaneous lesions and 16 out of 528 (3.0%) with onchocercal nodules in the skin. Nodules were significantly associated with age, being more common in subjects older than 10 years than in younger people (3.9% vs. 0%, p = 0.029). Regarding the onchocerciasis laboratory assessment, no positive parasitological test for microfilaria detection was found in the skin snips. The calculated seroprevalence through IgG4 serology was 7.9%. No children less than 10 years old were found to be positive for this test. Only one case was positive for Onchocerca volvulus (O. volvulus) after skin PCR. The present study points out that the on-going mass ivermectin treatment has been effective in reducing the prevalence of onchocerciasis and corroborates the interruption of transmission in Bioko Island. To our knowledge, this is the first time that accurate information through molecular and serological techniques is generated to estimate the onchocerciasis prevalence in this zone. Sustained support from the national program and appropriate communication and health education strategies to reinforce participation in CDTI activities are essential to ensure progress towards onchocerciasis elimination in the country.

Onchocerciasis or “river blindness” is a chronic parasitic disease which is mainly found in Sub-Saharan Africa. Onchocerciasis is endemic in both mainland and insular Equatorial Guinea. Huge achievements have been made on onchocerciasis control in Bioko Island in the last years, and the country is moving fast towards elimination. In the new elimination context, monitoring and evaluation activities with more sensitive diagnostic tools become especially necessary in order to confirm that transmission has been interrupted. Previous data on the epidemiological situation of onchocerciasis in Bioko Island are mainly based on microfilaria (MF) skin snip assessments. We aim to create evidence towards the fact that onchocerciasis transmission might have been achieved in Bioko Island after more than sixteen years of onchocerciasis control activities by using molecular and serological technics for onchocerciasis diagnosis.

Towards the development of an oral vaccine against porcine cysticercosis: expression of the protective HP6/TSOL18 antigen in transgenic carrots cells

The Taenia solium HP6/TSOL18 antigen was produced in carrot cells, yielding an immunogenic protein that induced significant protection in an experimental murine model against T. crassiceps cysticercosis when orally administered. This result supports the potential of HP6/TSOL18-carrot as a low-cost anti-cysticercosis vaccine candidate. Cysticercosis is a zoonosis caused by Taenia solium that can be prevented by interrupting the parasite life cycle through pig vaccination. Several injectable vaccine candidates have been reported, but the logistic difficulties and costs for its application limited its use in nationwide control programs. Oral plant-based vaccines can deal with this limitation, because of their easy administration and low cost. A stable expression of the HP6/TSOL18 anti-T. solium cysticercosis protective antigen in carrot calli transformed with an optimized transgene is herein reported. An antigen accumulation up to 14 µg g(-1) of dry-weight biomass was achieved in the generated carrot lines. Mouse immunization with one of the transformed calli induced both specific IgG and IgA anti-HP6/TSOL18 antibodies. A statistically significant reduction in the expected number of T. crassiceps cysticerci was observed in mice orally immunized with carrot-made HP6/TSOL18, in a similar extent to that obtained by subcutaneous immunization with recombinant HP6/TSOL18 protein. In this study, a new oral plant-made version of the HP6/TSOL18 anti-cysticercosis vaccine is reported. The vaccine candidate should be further tested against porcine cysticercosis.

Visceral larva migrans in immigrants from latin america

To determine whether increased migration is associated with an increase in incidence of toxocariasis (visceral larva migrans), we analyzed clinical data obtained from immigrants from Latin America. Although infection with Toxocara sp. roundworm larvae is distributed worldwide, seroprevalence is highest in tropical and subtropical areas.

Painful nail lesions

A man, 58 years of age, presented with a 4 year history of painful lesions of his nails. His previous history included hypertension, diabetes mellitus and hyperlipidaemia. These were treated with enalapril, metformin and simvastatin respectively. He also had asymptomatic skin lesions for over 15 years that had worsened in the past 4 years. His father had similar nail lesions that had been diagnosed as onychomycosis.

Parasite contamination of soil in households of a Mexican rural community endemic for neurocysticercosis

High neurocysticercosis (NC) prevalence was recently determined by a computed tomography (CT) scan study in the community of Tepetzitzintla, State of Puebla, Mexico. The aim of the present work was to evaluate the magnitude of fecal and parasite contamination by Taenia spp. in the soil of households of this community during the four seasons of the year. The toilet, backyard, kitchen, washboard, water containers and corrals of 14 to 26 households were sampled during each season. High Taenia spp. egg intensity was found in 24.2% of the sampled areas. The highest percentage was detected in Spring and the lowest in Summer. Significantly higher levels of Taenia spp. eggs were present in kitchen soil samples. A significant correlation was found between the presence of Taenia spp. eggs in household soil during the Summer, and NC diagnoses of the inhabitants by CT scan. Coproparasitological examinations and anti-cysticercal antibodies were determined in a cohort of inhabitants of the sampled households. Antibody levels and coproparasitological results were not associated with NC. Overall, these results illustrate the high degree of fecal contamination of potential risk to human health in rural communities and could be of use for control programmes.

Taenia solium: Identification and preliminary characterization of a lipid binding protein with homology to the SEC14 catalytic domain

The objective of this work is to identify proteins of the human and porcine parasite, Taenia solium, which may be exploited for control of the parasite. Through screening a cDNA library of T. solium metacestodes, we have identified a novel Sec-14-like Taenia lipid-binding protein that may play an important role in membrane trafficking. The Sec14-like sequence is a single copy gene, encoding a putative polypeptide of 320 amino acids and 36.1 kDa (sec14Tsol protein). Secondary amino acid structural analysis suggested that the sec14Tsol protein might contain two distinct structural domains, an amino-terminal alpha-helix rich domain and a mixed alpha-helix/beta-stand carboxy-terminal zone, showing homology with the conserved SEC14 domain found in a great number of proteins that bind lipids, as the regulators of membrane trafficking between Golgi membrane bilayers. Significantly, therefore, in a phosphoinositide-binding assay, sec14Tsol purified recombinant protein specifically interacted with important lipid regulators of membrane trafficking, with a preference for PI(3)P(2), PI(3,4)P(2), PI(4,5)P(2) and phosphatidic acid. Moreover, the sec14Tsol protein was localized in the Golgi apparatus of transfected cells and in the spiral canal region of T. solium metacestode tegument. As sec14Tsol protein may play an important role in membrane trafficking, its demonstrated localisation in the intact parasite tegument suggests its involvement in the function of the tegument and thus perhaps interaction with the host.

Molecular and functional characterization of a Taenia adhesion gene family (TAF) encoding potential protective antigens of Taenia saginata oncospheres

Two clones from an activated Taenia saginata oncosphere cDNA library, Ts45W and Ts45S, were isolated and sequenced. Both of these genes belong to the Taenia ovis 45W gene family. The Ts45W and Ts45S cDNAs are 997- and 1,004-bp-long, each corresponding to 255 amino acids and with theoretical molecular masses of 27.8 and 27.7 kDa, respectively. Southern blot profiles obtained with Ts45W cDNA as a probe suggest that these two genes are members of a multigene family with tandem organization. The full genomic sequence was determined for the Ts45W gene and a new family member, the Ts45W/2 gene. The genomic sequences of the T. saginata Ts45W and Ts45W/2 genes were at least 2.2 kb in length with four exons separated by three introns. Exons 1 and 4 coded for hydrophobic domains, while, importantly, exons 2 and 3 coded for fibronectin homologous domains. These domains are presumably responsible for the demonstrated cell adhesion and, perhaps, the protective nature of this family of molecules and the acronym TAF (Taenia adhesion family) is proposed for this group of genes. We hypothesize that these TAF proteins and another T. saginata-protective antigen, HP6, have evolved the dual functions of facilitating tissue invasion and stimulating protective immunity to first ensure primary infection and subsequently to establish a concomitant protective immunity to protect the host from death or debilitation through superinfection by subsequent infections and thus help ensure parasite survival.

Echinococcus granulosus (Cestoda, Taeniidae) in the Iberian wolf

The intestinal contents of 27 Iberian wolves (Canis lupus signatus) from Spain were screened for the presence of the taenid cestode Echinococcus granulosus. Four animals were found positive (15% prevalence). The intensity of parasitation was variable (mean 71, range 1-147 E. granulosus per host). Gravid individuals were found in all wolves positive with the parasite. Molecular characterization of the parasite material showed that the wolf strain belongs to the G1 genotype. According to the results, we conclude that the Iberian wolf takes part in the maintenance of the life cycle of this zoonotic parasite in Spain and that this fact could have public health relevance.

Ag-ELISA and PCR for Monitoring the Vaccination of Cattle against Taenia saginata Cysticercosis Using an Oncospheral Adhesion Protein (HP6) with Surface and Secreted Localization

A Taenia saginata oncosphere-derived adhesion protein (HP6) with surface and secreted localization was used to successfully vaccinate calves against oral challenge with T. saginata eggs. In contrast, vaccination using a combination of T. saginata oncosphere-derived peptides, selected on the basis of their antigenic index, and including three derived from the HP6 molecule (HP6-1, HP6-2 and HP6-3), was unsuccessful. This either indicated that the wrong peptides were selected or, in the case of the HP6 protein, that the protective epitope is conformational in nature. The protection experiments were monitored using a parasite antigen detection ELISA (HP10 Ag-ELISA), which allowed the early determination of the success of the vaccination protocol, subsequently confirmed at autopsy. PCR assays were used for the first time to confirm the presence of T. saginata DNA in lesions recovered at autopsy and thus verify the parasite origin of the lesions.

Tsp36, a tapeworm small heat-shock protein with a duplicated α-crystallin domain, forms dimers and tetramers with good chaperone-like activity

Small heat shock proteins (sHSPs), which range in monomer size between 12 and 42 kDa, are characterized by a conserved C-terminal alpha-crystallin domain of 80-100 residues. They generally form large homo- or heteromeric complexes, and typically have in vitro chaperone-like activity, keeping unfolding proteins in solution. A special type of sHSP, with a duplicated alpha-crystallin domain, is present in parasitic flatworms (Platyhelminthes). Considering that an alpha-crystallin domain is essential for the oligomerization and chaperone-like properties of sHSPs, we characterized Tsp36 from the tapeworm Taenia saginata. Both wild-type Tsp36 and a mutant (Tsp36C-->R) in which the single cysteine has been replaced by arginine were expressed and purified. Far-UV CD measurements of Tsp36 were in agreement with secondary structure predictions, which indicated alpha-helical structure in the N-terminal region and the expected beta-sandwich structure for the two alpha-crystallin domains. Gel permeation chromatography and nano-ESI-MS showed that wild type Tsp36 forms dimers in a reducing environment, and tetramers in a non-reducing environment. The tetramers are stabilized by disulfide bridges involving a large proportion of the Tsp36 monomers. Tsp36C-->R exclusively occurs as dimers according to gel permeation chromatography, while the nondisulfide bonded fraction of wild type Tsp36 dissociates from tetramers into dimers under nonreducing conditions at increased temperature (43 degrees C). The tetrameric form of Tsp36 has a greater chaperone-like activity than the dimeric form.

Taenia saginata derived synthetic peptides with potential for the diagnosis of bovine cysticercosis

Immunity in Taeniids is predominantly antibody mediated and thus many serological immuno-determinants will have potential in both protection and diagnosis. The antigenicity of six peptides derived from four potentially protective molecules cloned from a Taenia saginata oncospheres cDNA library have been evaluated as targets for the specific diagnosis of bovine cysticercosis. The six peptides consist of: two peptides (HP6-2 and HP6-3) derived from the sequence of the 18 kDa surface/secreted oncospheral adhesion antigen identified by McAb-HP6, two peptides (Ts45W-1 and Ts45W-5) derived from the sequence of the T. saginata homologue of the T. ovis 45W protective gene family, one peptide (TS45S-10) derived from a T. saginata sequence with significant similarity to the T. ovis 45S protective antigen, and one peptide (TEG-1) derived from the sequence of the T. saginata homologue of Echinococcus spp. main surface protein. Longitudinal studies indicate that T. saginata infected cattle respond to all six peptides by 3-4 weeks post-infection and that the antibody levels remain high for at least 12 weeks post-infection. As protection against Taeniid parasites is predominantly antibody mediated, some of these six peptides may be of value as immuno-prophylactic tools and hence also in assays to determine resistance to infection with the parasite. For diagnosis, on the other hand, only three peptides (HP6-2, TEG-1 and Ts45S-10) performed with the necessary sensitivity and specificity to determine exposure to infection with T. saginata, and now merit an exhaustive evaluation prior to employment as routine diagnostic tools.

Protective immunity against Taenia crassiceps murine cysticercosis induced by DNA vaccination with a Taenia saginata tegument antigen

This study investigated the protective capacity of the recombinant Taenia saginata Tso18 antigen administered as a DNA vaccine in the Taenia crassiceps murine model of cysticercosis. This Tso18 DNA sequence, isolated from a T. saginata oncosphere cDNA library, has homologies with Taenia solium and Echinococcus sp. It was cloned in the pcDNA3.1 plasmid and injected once intramuscularly into mice. Compared to saline-vaccinated control mice, immunization reduced the parasite burden by 57.3-81.4%, while lower levels of non-specific protection were induced in control mice injected with the plasmid pcDNA3.1 (18.8-33.1%) or a plasmid with irrelevant construct, pcDNA3.1/3D15 (33.4-38.8%). Importantly, significant levels of protection were observed between the pcDNA3.1/Tso18 plasmid and pcDNA3.1/3D15 plasmid immunized mice. Mice immunized with pTso18 synthesized low levels of, primarily IgG1 sub-class, antibodies. These antibodies were shown to recognize a 66 kDa antigen fraction of T. crassiceps and T. solium. Splenocytes enriched in both CD4+CD8- and CD4-CD8+ T cells from these vaccinated mice proliferated in vitro when exposed to antigens from both T. solium and T. crassiceps cestodes. Immunolocalization studies revealed the Tso18 antigen in oncospheres of T. saginata and T. solium, in the adult tapeworm and in the tegument of T. solium cysticerci. The protective capacity of this antigen and its extensive distribution in different stages, species and genera of cestodes points to the potential of Tso18 antigen for the possible design of a vaccine against cestodes.

Differential diagnosis of Taenia saginata and Taenia solium infections: from DNA probes to polymerase chain reaction

The objective of this work was the rapid and easy differential diagnosis of Taenia saginata and T. solium. First, a T. saginata size-selected genomic deoxyribonucleic acid (gDNA) library was constructed in the vector lambda gt10 using the 2-4 kb fraction from the parasite DNA digested with EcoR1, under 'star' conditions. After differential screening of the library and hybridization analysis with DNA from T. saginata, T. solium, T. taeniaeformis, T. crassiceps, and Echinococcus granulosus (bovine, porcine, and human), 2 recombinant phages were selected. They were designated HDP1 and HDP2. HDP1 reacted specifically with T. saginata DNA, and HDP2 recognized DNA from both T. saginata and T. solium. The 2 DNA probes were then sequenced and further characterized. HDP1 was a repetitive sequence with a 53 bp monomeric unit repeated 24 times in direct tandem along the 1272 bp fragment, while the 3954 bp HDP2 was not a repetitive sequence. Using the sequencing data, oligonucleotides were designed and used in a polymerase chain reaction (PCR). The 2 selected oligonucleotides from probe HDP1 (PTs4F1 and PTs4R1) specifically amplified gDNA from T. saginata, but not T. solium or other related cestodes, with a sensitivity of < 10 pg of T. saginata gDNA, about the quantity of DNA in one taeniid egg. The 3 oligonucleotides selected from the HDP2 sequence (PTs7S35F1, PTs7S35F2, and PTs7S35R1) allowed the differential amplification of gDNA from T. saginata, T. solium and E. granulosus in a multiplex PCR, again with a sensitivity of < 10 pg. These diagnostic tools have immediate application in the differential diagnosis of T. solium and T. saginata in humans and in the diagnosis of dubious cysts in the slaughterhouse. We also hope to apply them to epidemiological surveys of, for example, soil and water in endemic areas.

Molecular and immunodiagnosis of human filarial nematode infections

The filarial nematodes Wuchereria bancrofti, Brugia malayi and Onchocerca volvulus represent major public health problems in the Tropics. Effective diagnosis of infection with these parasites is required both for administration of drugs to infected individuals and for monitoring of control programs. However parasitological diagnosis is associated with a number of problems including frequently inadequate sensitivity, long pre-patency of infection and inconvenience for patients. For these reasons there has been considerable effort expended in developing other forms of diagnosis, in particular immunoassays for measuring antibody and circulating parasite antigen as well as molecular-biology-based assays for detecting parasite DNA. This article reviews the progress and achievements obtained to date. The latter include the development of ELISAs employing recombinant antigen for detection of antibody to O. volvulus which have both high sensitivity and specificity, the commercial availability of immunoassays to measure circulating antigen in W. bancrofti infection and the generation of specific DNA-based detection systems for all three parasites.

Differential diagnosis of Taenia saginata and Taenia solium infection by PCR

We have designed species-specific oligonucleotides which permit the differential detection of two species of cestodes, Taenia saginata and Taenia solium. The oligonucleotides contain sequences established for two previously reported, noncoding DNA fragments cloned from a genomic library of T. saginata. The first, which is T. saginata specific (fragment HDP1), is a repetitive sequence with a 53-bp monomeric unit repeated 24 times in direct tandem along the 1, 272-bp fragment. From this sequence the two oligonucleotides that were selected (oligonucleotides PTs4F1 and PTs4R1) specifically amplified genomic DNA (gDNA) from T. saginata but not T. solium or other related cestodes and had a sensitivity down to 10 pg of T. saginata gDNA. The second DNA fragment (fragment HDP2; 3,954 bp) hybridized to both T. saginata and T. solium DNAs and was not a repetitive sequence. Three oligonucleotides (oligonucleotides PTs7S35F1, PTs7S35F2, and PTs7S35R1) designed from the sequence of HDP2 allowed the differential amplification of gDNAs from T. saginata, T. solium, and Echinococcus granulosus in a multiplex PCR, which exhibits a sensitivity of 10 pg.

Molecular cloning and demonstration of an aminopeptidase activity in a filarial nematode glycoprotein

ES-62 is an abundant phosphorylcholine-containing secreted glycoprotein of the filarial nematode Acanthocheilonema viteae. Using an antiserum directed against the parasite molecule, 3 cDNAs of size, approximately 1.5-1.6 kbp were isolated from an A. viteae expression library. Sequence analysis in combination with N-terminal amino acid sequencing of purified ES-62 revealed that each clone contained a full-length cDNA for ES-62 corresponding to 474 amino acid residues but differed in their 5' and 3' untranslated regions. Characterisation of the 5' end of ES-62 mRNA using 5' rapid amplification of cDNA ends showed that it coded for a signal sequence. Several tryptic peptides were independently sequenced using quadruple-time-of-flight mass spectrometry and used to confirm the cDNA sequence. The mature protein was found to contain three potential N-linked glycosylation sites. Comparison of the derived amino acid sequence of ES-62 with the SwissProt database identified a sequence (between amino acid residues approximately 250 and 350 of mature ES-62) with significant similarity to several bacterial/fungal aminopeptidases. Incubation of ES-62 with leucine-7-amino-4-methylcoumarin as substrate confirmed that ES-62 possessed aminopeptidase activity.

Epidemiological analysis of Trichinella spiralis infections of foxes in Brandenburg, Germany

In a cross-sectional study conducted between March 1993 and February 1995, 7103 indiscriminately collected foxes were examined for Trichinella larvae. A total of 3295 serum samples were serologically investigated with an ELISA based on excretory-secretory antigen. The proportion of serologically positive animals ranged between 3.3% and 17.6% in random samples from individual counties or towns and resulted in an estimated overall prevalence of 7.7% (95% CI: 6.9-8.7%). Trichinella larvae were detected in the muscles of five foxes, corresponding to an estimated prevalence of 0.07% in the total sample (95% CI: 0.02-0.16%). The analysis of DNA of the Trichinella isolates by random amplification of polymorphic DNA (RAPD) lead to the identification of the isolates as Trichinella spiralis. The differences between serological and parasitological findings are discussed.

Immune responses of IL-5 transgenic mice to parasites and aeroallergens

Eosinophils have long been thought to be effectors of immunity to helminths but have also been implicated in the pathogenesis of asthma. Patterns of cytokine production in the host may influence the pathogenesis of these diseases by regulating the activities of eosinophils and other components of the immune response. Mice which constitutively over-express IL-5 have profound and life-long eosinophilia in a restricted number of tissues. Although eosinophils from IL-5 transgenics are functionally competent for a number of parameters considered to be important in inflammation, untreated animals are overtly normal and free of disease. In addition, the responses of these animals when exposed to aeroallergens and helminths present a number of apparent paradoxes. Eosinophil accumulation in tissues adjacent to major airways is rapid and extensive in transgenics exposed to the aeroallergen, but even after treatment with antigen over many months these mice show no evidence of respiratory distress or pathology. Helminth-infected IL-5 transgenics and their non-transgenic littermates develop similar inflammatory responses at mucosal sites and are comparable for a number of T cell and antibody responses, but they differ considerably in their ability to clear some parasite species. The life-cycle of Nippostrongylus brasiliensis is significantly inhibited in IL-5 transgenics, but that of Toxocara canis is not. Our results also suggest that eosinophilia and/or over-expression of IL-5 may actually impair host resistance to Schistosoma mansoni and Trichinella spiralis. The pathogenesis of diseases in which eosinophils are involved may therefore be more complex than previously thought.

Sequence and preliminary characterisation of a Taenia saginata oncosphere gene homologue of the small heat-shock protein family

During antibody screening of a Taenia saginata oncosphere cDNA library a clone (R-Tso2) sharing a high degree of homology at both the DNA and amino acid levels with the small heat-shock protein (shsp) family was identified. The R-Tso2 clone was a full-length sequence (1162 bp) with an open reading frame of 945 bp and 314 amino acids, corresponding to a deduced molecular mass of 35.6 kDa and isoelectric point of 5.6. R-Tso2 had the highest degree of homology with the Schistosoma mansoni major egg antigens, showing the characteristic shsp 100 amino-acid sequence motif duplicated. The R-Tso2 expression product was not immuno-precipitated by any serum from a panel of serum samples obtained from bovine, porcine and human hosts suffering from either T. saginata or T. solium cysticercosis.

Sequence and immunogenicity of the Taenia saginata homologue of the major surface antigen of Echinococcus spp

A clone (R-Tso18) was isolated from a Taenia saginata oncosphere cDNA library by screening with sera from rabbits immunised with oncosphere extract. It contained a full-length cDNA sequence of 1893 bp with an open reading frame of 1680 bp, corresponding to 559 amino acids with a deduced molecular mass of 65.173 kDa and an isoelectric point of 6.08. The R-Tso18 protein showed 80-84% nucleotide identity with the major protoscolex surface antigens of Echinococcus multilocularis (EM10) and E. granulosus (EG10). Preliminary immunogenicity studies employing the radiolabeled R-Tso18 protein in immune co-precipitation assays indicated sero-positivity for T. saginata-infected calf sera (6/13), T. solium cysticercosis human (7/22) and pig (2/2) sera and E. multilocularis (6/10)- and E. granulosus (1/12)-infected human sera, whereas other helminth-infection sera were negative. As immuno-precipitation is a relatively insensitive assay, it was concluded that further studies on the diagnostic potential of the purified recombinant R-Tso18 antigen, or its peptides, are merited.

Human onchocerciasis in Nigeria: isotypic responses and antigen recognition in individuals with defined cutaneous pathology

Antigen (Ag)-specific isotype responses to Onchocerca volvulus Ag (OvAg) were assessed by enzyme-linked immunosorbent assay and immunoblot in 123 residents of a mesoendemic area in northern Nigeria and 16 Nigerians from a nonendemic area. Individuals from an endemic area were divided into six groups on the basis of cutaneous onchocercal pathology: acute papular onchodermatitis (APOD), chronic papular onchodermatitis (CPOD), lichenified onchodermatitis (LOD), atrophy (ATR), depigmentation (DPM) and normal skin, high microfilarial load (NSHMF). Immunoglobulin (Ig)G1-4 levels were all significantly associated with residence in an endemic area after controlling for age and sex (all P values = 0.0001). Both IgG1 and IgG3 were significantly associated with onchocercal clinical category after controlling for age, sex, and microfilarial load (P = 0.0031 and 0.0035, respectively). The IgG1 and IgG3 responses were both highest in LOD and lowest in NSHMF and ATR, respectively. A significant inverse association was found between IgG1 levels and microfilarial load after controlling for age, sex, and clinical category (P = 0.0061). On immunoblotting, 20 (44.4%) of 45 individual onchocerciasis sera contained IgG4 antibodies against a band of 29-31 kD, which was not recognized by pooled sera from individuals with other filarial infections. There was heterogeneity of antigen recognition within each of the onchocercal clinical groups, which together with the small numbers examined by immunoblotting, limits interpretation. Nevertheless, some differences in patterns of antigen recognition were found between the onchocercal groups. The LOD group demonstrated prominent immunoreactivity in IgG1 and IgG3 while a general paucity of low molecular weight reactivity was seen with NSHMF in IgG1-3 subclasses, but there was no specific banding pattern that differentiated NSHMF from those with pathology. Comparison of microfilariae-positive (mf+) and mf- individuals with onchocercal skin disease revealed significantly higher levels of all IgG subclasses and higher overall scores on semiquantitative assessment of immunoblots for IgG1, IgG2, and IgG4 for mf+ individuals. Differing isotypic responses may play a role in the pathogenesis of the clinical spectrum of cutaneous onchocerciasis.

Identification of Onchocerca volvulus collagen as an antigen mainly recognized by antibodies in chronic hyper-reactive onchodermatitis (sowda)

An Onchocerca volvulus expression library was differentially screened to identify a molecular marker distinguishing sowda (lichenified onchodermatitis) from other onchocerciasis forms. One clone, PG3, was recognized by pooled sera from patients with sowda, but not by pooled sera from patients with generalized onchocerciasis; it was not recognized by sera from patients with lymphatic filariasis or other helminth infections. The DNA of PG3 hybridized strongly with O. volvulus Eco RI-digested DNA, but not with DNA from Brugia spp., Trichinella spp., and humans. A weak reaction was observed with DNA from O. gibsoni and Acanthocheilonema viteae. The PG3 DNA sequence showed a high homology with both human and nematode collagens. Confirmation of the collagen-like nature of the sowda-specific PG3 product was obtained by amino terminal sequencing of the PG3 expression product, as well as by demonstrating its susceptibility to collagenase digestion. The characteristic recognition of the O. volvulus collagen specified by clone PG3 was confirmed by measuring antibody levels to the expressed product in individual sowda and generalized onchocerciasis sera, respectively. Identification of a nematode collagen antigen mainly recognized in sowda patients raises the possibility that this extreme form of dermatitis might arise through cross-reactivity between anti-O. volvulus collagen antibodies and human collagen. However, a relationship between the PG3 recognition by antibodies and the sowda pathogenesis could not be demonstrated.

EU experimental study on wild boar trichinellosis

From January 1994 onwards the Council Directive 92/45 EEC concerning the examination of wild game meat for trichinellosis is valid. Laboratory methods required are identical to those used for the examination of pork. In an international experiment the suitability of these methods to control wild boar meat was tested. Required meat parts of experimentally with T. spiralis infected wild boars were shipped to seven laboratories in Europe under code. It was concluded that trichinoscopy and pool sample digestion methods meant for pork examination could equally well be used for control of wild boar meat. The so called Trichomatic method required a few adaptations. Moreover it was demonstrated that extra washing procedures were required to prevent cross contamination between samples with Trichomatic equipment.

The differentiation of parasitic nematodes using random amplified polymorphic DNA

DNA from species and races of plant parasitic nematodes (Meloidogyne, Globodera and Heterodera) and a human parasitic nematode (Trichinella) were subjected to polymerase chain reaction amplification using one arbitrary primer (M-10). This technique results in relatively simple DNA profiles that include polymorphic markers known as random amplified polymorphic DNA (RAPDs). The RAPD profiles of the plant nematode species of Meloidogyne made possible the identification of M. incognita and M. hapla, but no differences were found between the patterns of M. javanica, M. arenaria and M. graminicola. Moreover, the four races of M. incognita were indistinguishable by this primer. In contrast, when races of the plant nematode Globodera rostochiensis (Ro1 and Ro2/3) were studied under the same RAPDs conditions, a race specific profile allows these two most devastating races to be differentiated. When DNAs of eight Trichinella isolates were subjected to RAPD studies, four different patterns were identified, corresponding to the four Trichinella clusters previously defined by isozyme polymorphism.

A longitudinal study of porcine serological responses to experimental infections with T-1 and T-3 Spanish Trichinella isolates

Comparison of antibody response and antigen recognition was made by ELISA and western-blot analysis in pig experimental infections by T-1 and T-3 Spanish Trichinella isolates. Two groups of Iberian pigs were experimentally infected with 150 larvae/kg body weight of GM-1 and C-76 Spanish Trichinella isolates as representatives of T-1 and T-3 gene pools respectively. Antibody levels and antigen recognition were measured on days -14, 0, 6, 16, 20, 27, 34, 49, 63 and 82 after infection by ELISA and western-blotting assays. Antibody response against C-76 infection was significantly delayed and lower than against GM-1. The two Trichinella isolates were indistinguishable, however, by western blotting analysis, although recognition of larval antigens was quantitatively higher than adult ones. Interestingly, the principle larval antigenic components recognized by pigs were those recognized by the monoclonal anti-sera NIM-M1. Finally, there were no serological patterns indicative of the stage of infection ("antibody windows") discriminating, for example between early versus late infections.

A species-specific oligonucleotide DNA probe for the identification of Meloidogyne incognita

A genomic library of Meloidogyne incognita Race 1 has been prepared in the bacteriophage lambda gt10 and screened for specific DNA sequences by hybridization with radio-isotope labelled total genomic DNA from a number of Meloidogyne species. One clone isolated (MR1 #15), although not totally species specific, clearly showed preferential hybridization to M. incognita. Following subcloning and sequencing of the 255 bp insert, four stretches of the sequence corresponding to oligonucleotides of approximately equal length (approximately 70 bp) were synthesized and examined for specificity. One of them, MR1 #15.2, showed the necessary specificity to be used as a diagnostic tool.

Surface antigens of male worms and microfilariae of Onchocerca gibsoni

Living adult males and microfilariae of the cattle filarial parasite Onchocerca gibsoni were externally labelled with radioactive iodine using the iodogen and Bolton-Hunter procedures. Characterization of labelled surface proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis revealed clear cut differences in the two life cycle stages. In addition, the two radiolabelling procedures yielded some differences in the profiles of radiolabelled surface proteins for both adults and microfilariae. Immunoprecipitation analysis revealed a number of labelled antigens recognized by antibodies in human onchocerciasis serum pools, thereby demonstrating the usefulness of O. gibsoni as a model in Onchocerca volvulus vaccine studies. The reactivity of microfilarial antigens extended to antibodies from other human nematode infections, whereas male surface antigens, particularly those of low molecular weight, were Onchocerca specific. This indicates that O. gibsoni can provide a convenient source of specific diagnostic antigen.

DNA polymorphisms within Spanish Trichinella isolates

A total of 13 Spanish Trichinella isolates were characterised by DNA analysis. Genomic DNA cross-hybridisation tests revealed two distinct groups that exhibited weak cross-reactions. Further diagnostic subdivision was attempted according to restriction-fragment polymorphism using a cloned T. spiralis DNA repetitive fragment as a probe, but no major difference between the two Trichinella groups was observed.

Cloning of specific diagnostic antigens of Onchocerca volvulus

Specific, serological diagnosis is one of the main goals in onchocerciasis research. To date this objective has been hampered by (a) scarcity of parasite material, and (b) antigenic cross-reaction between Onchocerca volvulus and other nematode species. In order to obtain specific antigens, and in amounts suitable for study, molecular biological techniques have been adopted. A lambda gt11 cDNA expression library prepared from O. volvulus adult female worms was screened using infected human sera from onchocerciasis patients and rabbit hyperimmune sera raised against Onchocerca and genus-specific Onchocerca antigen extracts. Five clones were selected and their inserts expressed as beta-galactosidase fusion proteins. The fusion proteins were examined using individual sera from patients with O. volvulus or Wuchereria bancrofti infections. Three of the fusion proteins were recognised by more than 80% of O. volvulus sera and exhibited weak reactivity with a few W. bancrofti sera. One of these three clones was recognised to a significantly greater degree by sera from sowda than from generalised onchocerciasis patients.

Cloning of a species-specific DNA probe from Onchocerca gibsoni

A genomic library of Onchocerca gibsoni has been prepared in the vector lambda-gt10 and has been screened for specific DNA sequences by hybridization with radiolabelled total genomic DNA from a number of Onchocerca species. A clone--fOGI--has been isolated which does not interact with DNA prepared from O. gutturosa, O. lienalis, O. ochengi, O. cervicalis or O. volvulus (both Liberian and Mexican isolates). In addition, no hybridization is observed with host (cattle) DNA. fOGI can detect as little as 100-200 pg of O. gibsoni DNA. It is thus concluded that fOGI has the sensitivity to detect microfilariae of O. gibsoni found in the skin of cattle and the specificity to differentiate them from closely related species living in the same environment.

Specific and cross-reacting antibodies in human responses to Onchocerca volvulus and Dracunculus medinensis infections

Immunoelectroblotting and enzyme-linked immunosorbent assay were used to identify non-cross-reacting antigenic components of Dracunculus medinensis and the filarial worms Onchocerca volvulus, Loa loa, Wuchereria bancrofti, Brugia malayi, and Mansonella ozzardi. Parasite specific serodiagnostic ELISA systems for onchocerciasis and dracunculiasis were devised based on these findings. Phosphate buffered saline extracts of adult worms were passed through a column of monoclonal antibodies to phosphorylcholine (PC). Crude and PC-depleted extracts were reacted on ELISA plates with individual sera from subjects infected with a range of nematodes. Binding of total antibody (Ig) or IgG class antibody and IgG4 subclass antibody was revealed using goat antihuman-Ig-phosphatase conjugate, or appropriate mouse monoclonal antihuman-Ig-type-specific reagents, followed by goat antimouse-Ig-phosphatase conjugate. Specificity of ELISA was improved by restricting reaction to the host's IgG4 antibody subclass, and/or by removing PC determinants from crude antigens. In parallel immunoelectroblots, crude and PC-depleted extracts probed with pooled sera showed potentially useful diagnostic antigens, including a 12 kDa protein from D. medinensis and 14, 18, and 27 kDa proteins from O. volvulus. Two Onchocerca specific ELISA systems non-reactive with antibodies to D. medinensis were devised.

Comparative study on polypeptide patterns of larvae of Trichinella isolates by two-dimensional electrophoresis

The two-dimensional patterns (isoelectrofocusing-IEF/polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate-SDS) of S3 fractions of muscle larvae of four Trichinella isolates were compared. The comparative study concerned six groups of polypeptides. It was observed that the Garkavi isolate of Trichinella pseudospiralis was clearly different from the other isolates, and it showed the simplest IEF/SDS polypeptide pattern. The C-76 isolate of T. nelsoni had only four of the six groups, distinguishing it from the GM-1 isolate of T. spiralis and the Boev isolate of T. nativa that showed all the indicated groups.