Identification and partial purification of a 26 kilodalton antigen of adult Haemonchus contortus

Recombinant cold shock domain containing protein is a potential antigen to detect specific antibody during early and late infections of Haemonchus contortus in goat

BACKGROUND

Haemonchus contortus (H. contortus) is one of the most important parasites that cause huge economic losses to small ruminant industry worldwide. Effective prognosis and treatment depend upon the early diagnosis of H. contortus infection. To date, no widely-approved methods for the identification of prepatent H. contortus infection are available to identify prepatent H. contortus infection properly. The aim of this study was to evaluate the diagnostic potential of recombinant cold shock H. contortus protein (rHc-CS) during early and late infections of H. contortus in goat.

RESULTS

Purified rHc-CS exhibited a clear band, with a molecular weight about 38 kDa. H. contortus eggs were not detected by fecal egg count technique from feces collected at 0 to 14 days post infection (D.P.I). However, eggs were detected at 21, 28 and 35 D.P.I. Hence, results of immunoblotting assay showed specific anti rHc-CS antibody detection in all goat sera collected at early stage (14 D.P.I) and late stage (21-103 D.P.I) of H. contortus infection. Furthermore, no cross reactivity was observed against Trichinella spiralis, Fasciola hepatica and Toxoplasma gondii or uninfected goats. Among several evaluated rHc-CS indirect-ELISA format variables, favorable antigen coating concentration was found 0.28 μg/well at 37 °C 1 h and overnight at 4 °C. Moreover, optimum dilution ratio of serum and rabbit anti-goat IgG was recorded as 1:100 and 1:4000, respectively. The best blocking buffer was 5% Bovine Serum Albumin (BSA) while the best time for blocking, serum incubation and TMB reaction were recorded as 60, 120 and 10 min, respectively. The cut-off value for positive and negative interpretation was determined as 0.352 (OD450). The diagnostic specificity and sensitivity of the rHc-CS, both were recorded as 100%.

CONCLUSION

These results validated that rHc-CS is a potential immunodiagnostic antigen to detect the specific antibodies during early and late H. contortus infections in goat.

Immunodiagnostic potential of recombinant tropomyosin during prepatent Haemonchus contortus infection in goat

Excretory and secretory products (ESPs) are released by the parasites during Haemonchus contortus (H. contortus) infection. In this study, Tropomyosin (TpMy), one of these ESPs was used to develop western blotting and optimized Enzyme Linked immunosorbent assay (ELISA) for detection of H. contortus during early infection in goat. Microscopic examination was performed parallel for comparison. Recombinant tropomyosin protein was purified successfully. Western blotting results revealed that anti-recombinant H. contortus Tropomyosin (rHc-TpMy) antibodies could recognize the natural proteinand rHc-TpMy antigen did not show any cross-reaction with goat anti-sera of Fasciola hepatica, Trichinella spiralis, and Toxoplasma gondii. Moreover, initial antibodies were detected by both western blotting and indirect ELISA at 14 days post infection (DPI) and persisted till 30 DPI but fecal eggs count couldn't detect the eggs in feces at early stage (7 and 14 DPI). The optimized antigen coating concentration was calculated as 10 μg/ml (P/N Optimum Density₄₅₀ = 4.165) with optimized dilution of serum (1:50) and secondary antibody (1:2500). Positive and negative cutoff value of the indirect-ELISA assay was calculated as 0.392 and 0.344, respectively. Receiver operating characteristic curve analysis validated the cutoff value (0.392) based on a high specificity and sensitivity. Indirect ELISA showed 90% diagnostic sensitivity and 100% diagnostic specificity. In comparison of serological and conventional method, rHc-TpMy based indirect ELISA showed more positive results (30%; 9/30) than microscopic examination (20%; 6/30). These results demonstrated that rHc-TpMy is a potential immunodiagnostic antigen to detect specific antibodies at early stage of infection in goat and serological methods are more reliable as compared to microscopic examination.

Evaluation of different Haemonchus contortus antigens for diagnosis of sheep haemonchosis by ELISA and their cross reactivity with other helminthes

Haemonchus contortus (H. contortus) remains important nematode that infecting sheep all over the world. Truthful diagnosis of haemonchosis needs reliable Enzyme linked immune sorbent assay test as well as the immuno-reactive protein profile of different prepared H. contortus antigens; larval (L), excretory secretory product (ESP) and adult somatic H. contortus (AS). The current study fulfilled that L antigen is the talented antigen for such serological diagnosis. Immunodominant band at molecular weight 57 kDa were answerable for highest specificity and accuracy of positive predictive value of this antigen. Moreover, the highest apparent prevalence value was 92 and 75% obtained by L and ESP antigens, respectively. The results of cross reactivity among AS, Monezia expansa (M. expansa) and Fasciola spp. revealed that AS antigen appeared major cross reactivity with other cestode and trematode. Best dilution of serum was (1:800) to rise above this phenomenon.

Protein profiling of Haemonchus contortus found in sheep of Kashmir valley

Economic losses due to helminth parasites in sheep throughout the world are considerable. Haemonchus contortus is a blood sucking intestinal helminth that lives in the abomasum of small ruminants worldwide. This parasite can be devastating to producers as it causes decreased production levels due to clinical signs such as anaemia, edema and death. For isolation of the proteins of the parasite, a well defined methodology was adopted. The abomasae of sheep in which this parasite resides were collected from abattoirs of various districts and were then carried to laboratory for screening. In case of collection sites falling in far areas, the organs were screened on spot. The parasites were collected in normal saline, washed and stored in 0.05 M PBS with pH of 7.4 at 0 °C. After refrigeration, frozen nematodes were thawed, homogenized and centrifuged at 1,000-15,000 rpm for 15 min. The supernatant was thus collected as a protein mixture and stored at -20 °C. Protein concentration of the samples was estimated by Lowry method. The samples were then analyzed through PAGE and then through SDS-PAGE. Protein estimation of the samples was estimated to be 4.2 mg/ml. The processed parasite samples were then subjected to PAGE and SDS-PAGE to determine the presence of the proteins. It showed high concentration of proteins in its whole protein profile. The proteins were seen as continuous bands intermixing with each other in PAGE analysis. The present study revealed two bands of molecular weights-55 and 33 kDa in PAGE analysis. The proteins when analyzed through SDS-PAGE were mostly found in the range of 25-70 kDa. The SDS-PAGE analysis showed four prominent bands. These bands were of the molecular weights of 66, 40, 33 and 26 kDa. The present work was a challenging one since only a single study was conducted in this region on this aspect and thus obviously was a big task to peep into the field where scanty input was available.

Ion-exchange protocol to obtain antigenic fractions with potential for serodiagnosis of strongyloidiasis

The aim of this study was to fractionate and partially characterize the antigenic extract of filariform larvae of Strongyloides venezuelensis in ion-exchange resin diethylaminoethyl sepharose (DEAE), to obtain antigenic fractions potentially applicable in immunoassays. Somatic antigen (SA) and its fractions DEAE S1 and DEAE S2 - which interacted with the resin - were evaluated by 1-dimensional electrophoresis to obtain protein profiles. SA and its fractions were tested in serum samples for IgG detection by ELISA. Serum samples (n = 155) were analysed: 50 from strongyloidiasis patients (G1), 55 from patients with other parasitic infections (G2) and 50 from healthy volunteers. Sensitivity (Se), specificity (Sp), area under curve (AUC) and likelihood ratios (LR) were calculated. The DEAE S2 fraction provided a high diagnostic value for IgG detection (Se 92·0%, Sp 91·4%, AUC 0·981, LR+ 10·75, LR − 0·09). In conclusion, the DEAE S2 fraction would probably be a source of immunodominant polypeptides for IgG detection in human strongyloidiasis serodiagnosis.

Immunization against Lamb Haemonchosis with a Recombinant Somatic Antigen of Haemonchus contortus (rHcp26/23)

Haemonchosis, caused by the abomasal nematode Haemonchus contortus, is a common parasitic disease of sheep. Our previous results showed that a soluble fraction from adult stages of the nematode (p26/23) induced partial protection against challenge. Recombinant DNA technology was applied to obtain a synthetic protein (rHcp26/23). Immunological assays (ELISA, Western blotting, and immunolocalization), using sera from lambs immunized with p26/23, confirmed the identity of the recombinant protein and demonstrated that the synthetic protein is equivalent to the purified protein employed in the previous immunoprophylaxis studies. Vaccination of lambs with 300 mug of rHcp26/23 and Freund's adjuvant elicited a notable specific antibody response. Immunization did not induce any significant protection after challenge with 16000 infective larvae of H. contortus, and comparable values for parasite faecal egg output, packed cell volume, and abomasal parasite burdens were found in vaccinated and control animals.

Value of Haemonchus longistipes purified antigens in diagnosis of gastro-intestinal nematodes infection in camels

Fractionated Haemonchus longistipes crude antigen revealed 7 protein fractions at molecular weights of 93, 74, 67, 56, 32, 26 and 16 kDa. The bands at 56, 32 and 26 kDa reacted specifically with H. longistipes hyperimmune sera prepared in rabbit (1:100 dilution) using EITB technique. The eluted concentrated fractions as well as crude worm antigens were used in diagnosis of natural infection of Gastro-Intestinal Nematodes (GIN) only or associated with other parasites in camels using ELISA technique. H. longistipes crude antigen and fraction of 26 kDa induced high sensitivity in diagnosis of infection in animals harboring GIN only (sensitivity was 95-100%), while it was 85.0-93.3% with 32 kDa fraction and 55.5-73.3% with that of 56 kDa using ELISA technique. The two H. longistipes eluted protein fractions of 26 and 32 kDa showed higher sensitivity than their crude antigens in diagnosis of GIN infection mixed with other parasites. While, Protein bands of 26 kDa appeared more sensitive than the other protein bands in detection of anti- H. longistipes antibodies at higher serum dilution. With special superiority for fraction of 26 kDa, in comparison with the other antigens, sharp specificity or sensitivity in diagnosis, could not be achieved in this study especially in case of mixed infection with other parasites, where these animals might be immune-compromised.

Characterisation of Haemonchus contortus-derived cell populations propagated in vitro in a tissue culture environment and their potential to induce protective immunity in sheep

Cell populations derived from viable Haemonchus contortus L(3) larvae were propagated in vitro in a tissue culture environment for a prolonged period (>48 months). Microscopic evaluation of H. contortus-derived cell populations revealed gross morphological characteristics highly analogous to those described for cell types originating from species of plant nematodes propagated in vitro in a tissue culture environment for a briefer period of time (<6 months). The characterisation of extracts harvested from tissue culture populations of H. contortus-derived cells by SDS-PAGE analysis detected molecular fractions of approximately 29, 45, 55, and 200-kDa that closely correlated with reports for preparations obtained from intact/viable H. contortus larvae. Complementary investigations detected the dual biochemical expression of phosphohydrolase and aminopeptidase-M activities based on the hydrolysis of the synthetic enzyme-specific substrates, para-nitrophenylphosphate and leucine-para-nitroanaline, respectively. The identification of phosphohydrolase and aminopeptidase-M-like biochemical activity in fractions harvested from H. contortus-derived cell populations and propagated in vitro in tissue culture served as evidence validating their parasitic-origin. Further validation of H. contortus-derived cell populations propagated in tissue culture entailed the formulation of Triton X-100 extracts containing potential immunoprotective antigens with SEAM adjuvant and its administration by intramuscular injection (100 microg total protein) to healthy sheep (n=8) on day 0 (left rear-limb) and day +14 (right rear-limb). Animals on day 28 subsequently received a single oral challenge of 10,000 infective L(3)-stage H. contortus larvae. Applying ELISA methodologies, increases in antigen-specific IgM and IgG were detected in ovine serum samples. Interpretation of experimental findings revealed that sheep with the greatest antigen-specific humoral immune responses (IgG titre 1/3125) also demonstrated a degree of reduced abomasal H. contortuslarvae burdens (60% reduction). Polyclonal antibody from immunoprotected sheep was subsequently found to recognise both the: (i), digestive tract; and (ii), antigen extracts associated with intact/viable H. contortus larvae. These experimental findings reveal the potential feasibility of propagating parasite-derived cell populations in an in vitro tissue culture environment in a manner that retains their ability to express immunoprotective antigenic fractions.

Serodiagnosis of haemonchosis with a somatic antigen (Hc26) in several breeds of sheep

Sera from 53 sheep belonging to Castellano, Churro, Manchego, and Merino breeds were analyzed to test the diagnostic value of a 26-kD antigen from adult Haemonchus contortus at prepatency and early and late patency of experimental haemonchosis. Animals that received zero, 1, or 2 infections with the parasite were tested. In addition, sera from 20 experimentally infected and 10 noninfected Texel sheep were used to test the antigen. Sera from 37 infected animals at prepatency as well as at patency in primary and secondary infection were found positive with the 26-kD antigen. However, sera from 10 animals with the lowest worm burdens (second infection) did not recognize the antigen during early patency (day 28 postinfection). IgG1 was the only isotype implicated in antigen recognition because IgG2, IgA, and IgM, in the same sera, showed no reactivity with the peptide. Antigen specificity was confirmed because hyperimmune sera against infective larvae and adult stages of the most common gastrointestinal nematodes found in natural infections in sheep (Trichostrongylus colubriformis and Teladorsagia circumcincta) did not recognize this peptide. The antigen was recognized only by anti-adult H. contortus hyperimmune sera and appeared to be absent in the L3 parasite stage. In addition, the partial N-terminal amino acid sequence of the diagnostic peptide is reported.

Vaccination of Manchego lambs against Haemonchus contortus with a somatic fraction (p26/23) of adult parasites

A low molecular weight fraction from adult Haemonchus contortus containing two peptides (p26/23) was used to vaccinate Manchego female lambs between 3.5 and 5 months of age. Immunizing injections were given three times on days 0, 14 and 28 of the experiment. On day 43, lambs were challenged with 400 third stage larvae/kg live weight. Vaccination induced a lengthening of prepatent periods, significant reduction (> 60%) in mean faecal egg counts and smaller variations in packed cell volume values. At necropsy, average worm burden in the vaccinated lambs was significantly lower (61.6%) than that found in unvaccinated challenged animals. A clear correlation was found between protection and serum antibody response in immunized lambs.

Immunological control of gastrointestinal nematode infections

Control of nematode parasitism by an active manipulation of the host immune response has been a goal of veterinary and medical parasitologists for decades. The reality of achieving this goal has been questioned vigorously and demonstrations of the feasibility of using immunological control under field conditions are minimal. Nevertheless, with the rapid growth of modern biotechnology and the identification of novel parasite molecules as vaccine targets, the potential for success in this area has recently generated considerable excitement. The induction and regulation of the ruminant immune response against nematode parasites can be controlled either by management programs which include anthelmintic treatment or by vaccination. Both approaches will be discussed in this session.