Protection studies with recombinant excretory/secretory proteins of Haemonchus contortus

Abstract

The efficacy of two recombinant proteins of Haemonchus contortus was studied in both adult sheep and young lambs. These 15 and 24 kDa excretory/secretory proteins were given combined, either supplemented or not with a glycan-rich insect cell extract. In 9-month-old sheep (trial 1), faecal egg output and worm burden were reduced by 49% and 55%, respectively, after vaccination with rec15/24, and by 46% and 65% after vaccination with rec15/24 and glycan extract. No reduction in egg output or number of worms was found in young lambs using the above recombinant proteins plus glycan-rich extract (trial 2). When trial 1 was repeated (trial 3), the protection could not be reproduced, possibly due to differences in batches of recombinant proteins. In all sheep, independent of their age, rec15/24-specific immunoglobulin (Ig)G1 and IgA titres were present, but 9-month-old protected sheep had significantly higher IgA titres than the lambs. Addition of glycans resulted in lower rec15/24-specific IgG1 and IgA in 9-month-old sheep after challenge. This did not affect the level of protection. A significant negative correlation was found between IgA and worm numbers in protected sheep immunized with rec15/24 supplemented with glycans. Total IgE and rec15/24 specific IgE titres were low. The number of eosinophils, mast cells, sheep mast cell protease (SMCP)+ cells and IgA+ cells did not differ between the protected and unprotected sheep, but the lambs had significantly fewer mast cells independent of their immunization.

Vaccination against Ostertagia ostertagi with subfractions of the protective ES-thiol fraction

“…This will enable us to compare the protective capacity of future recombinant ASPs to that of its native form. Recombinant ASP molecules have been evaluated for A. caninum (Ghosh et al, 1996;Ghosh and Hotez, 1999;Sen et al, 2000), A. ceylanicum (Goud et al, 2004;Mendez et al, 2005), O. volvulus (MacDonald et al, 2004) and H. contortus (Vervelde et al, 2002). These recombinants were produced in bacterial systems and the levels of protection varied between 21 and 79% reduction in parasite burden.…”

“…ASPs belong to a group of evolutionary related secreted proteins called the SCP/tpx-1/Ag5/PR-1/Sc7 www.elsevier.com/locate/vetpar Veterinary Parasitology 149 (2007) [239][240][241][242][243][244][245] family and are present in different organisms such as plants, mammals and nematodes. ASP molecules have previously shown their protective capacity in vaccine trials against Ancylostoma caninum (Ghosh et al, 1996;Ghosh and Hotez, 1999;Sen et al, 2000), A. ceylanicum (Goud et al, 2004;Mendez et al, 2005), Onchocerca volvulus (MacDonald et al, 2004) and Haemonchus contortus (Schallig et al, 1997a,b;Vervelde et al, 2002). The exact function of the ASPs remains unclear, although it is believed that they play a role in parasite infection and transition to parasitism .…”

Comprehensive Analysis of the Secreted Proteins of the Parasite Haemonchus contortus Reveals Extensive Sequence Variation and Differential Immune Recognition

“…Obtained after in vitro cultivation of adult worms in serum-free medium, ESP or its partially purified fractions are able to induce 65 to 90% protection against H. contortus in sheep (1,2), but protective properties have not conclusively been attributed to individual proteins.…”

Toxoplasma gondii Isolates of Free-Ranging Chickens From Rio de Janeiro, Brazil: Mouse Mortality, Genotype, and Oocyst Shedding by Cats

“…To date, studies that use recombinant E. coli fusion proteins in antinematode vaccines have been disappointing with respect to worm burden reductions compared with their corresponding native antigen. For instance, native Haemonchus contortus antigens, such as H11 leucine aminopeptidase, H-gal-GP (comprising developmentally regulated gut proteases), and a 40-kDa antigen with homology to the A. caninum-secreted protein (ASP), each purified from parasite detergent-soluble extracts for secretory products, elicit high degrees of protection in vaccinated sheep or guinea pigs, as evidenced by worm burden reductions, compared with adjuvant-vaccinated control animals (Munn et al, 1997;Sharp and Wagland, 1998;Knox, 2000;Knox and Smith, 2001;Vervelde et al, 2002;Hotez et al, 2003). However, the corresponding genetically engineered fusion proteins expressed FIGURE 2.…”

“…in E. coli do not reproduce this effect (Munn et al, 1997;Sharp and Wagland, 1998;Knox and Smith, 2001;Vervelde et al, 2002). Experimental evidence indicates that the E. coli fusion proteins do not exhibit conformational epitopes that correspond to native proteins or proteins expressed in eukaryotic systems (Munn et al, 1997;Knox and Smith, 2001).…”