Moderate protection is induced by a chimeric protein composed of leucine aminopeptidase and cathepsin L1 against Fasciola hepatica challenge in sheep |
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| Institution: | 1. Department of Pathobiology, Faculty of Science, Mahidol University, Rama VI Rd, Ratchathewi, Bangkok 10400, Thailand;2. Faculty of Allied Health Sciences, Burapha University, Long-Hard Bangsaen Rd, Saen Sook Sub-district, Mueang District, Chonburi 20131, Thailand;3. Department of Anatomy, Faculty of Science, Mahidol University, Rama VI Rd, Ratchathewi, Bangkok 10400, Thailand;4. Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 52000, Thailand;5. Faculty of Animal Science, Silpakorn University, Phetchaburi Campus, Cha-am, Phetchaburi 76120, Thailand;6. Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, 10400, Thailand |
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| Abstract: | Leucine aminopeptidase (FhLAP) and cathepsin L1 (FhCL1) of Fasciola hepatica play a critical role in parasite feeding, migration through host tissue, and immune evasion. These antigens have been tested for immune protection as single components with variable degrees of success. The chimeric-protein approach could improve protection levels against fasciolosis. Previously, we reported the design and construction of a chimeric protein composed of antigenic sequences of FhLAP and FhCL1 of F. hepatica. The goal of the present study was to express and evaluate the immune-protective capacity of this chimeric protein (rFhLAP-CL1) in sheep. Animals were randomly allocated into five groups with five animals in each group. Groups 1, 2 and 3 were immunized twice with 100 μg, 200 μg and 400 μg of rFhLAP-CL1 emulsified with Quil A adjuvant, whereas groups 4 and 5 were the adjuvant control and infection control groups, respectively. The animals were then challenged with 200 metacercariae two weeks after the rFhLAP-CL1 booster. The fluke burden was reduced by 25.5%, 30.7% (p < 0.05) and 46.5% (p < 0.01) in sheep immunized with 100 μg, 200 μg and 400 μg of chimeric protein, respectively, in comparison to the infection control group. There was a reduction of 22.7% (p < 0.05) and 24.4% (p < 0.01) in fecal egg count in groups 2 and 3, respectively, compared to the infection control group. Sheep immunized with chimeric protein produced F. hepatica excretion-secretion product-specific total IgG antibody, which were increased after challenge. Moreover, the levels of rFhLAP-CL1-specific IgG1 and IgG2 isotypes in immunized sheep increased rapidly two weeks after the first immunization and were significantly more elevated than those of the control groups, indicating a mixed Th1/Th2 response. This is a preliminary evaluation of the chimeric protein rFhLAP-CL1 as a possible immunogen against F. hepatica infection in sheep. |
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| Keywords: | Fasciola hepatica Chimeric protein Immunization Sheep |
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