A Modified Variant of <i>Fasciola hepatica</i> FhSAP-2 (mFhSAP-2) as a Recombinant Vaccine Candidate Induces High-Avidity IgG2c Antibodies and Enhances T Cell Activation in C57BL/6 Mice
Background/Objectives: In the past, FhSAP-2, an 11.5 kDa recombinant protein belonging to the <i>Fasciola hepatica</i> saposin-like/NK-lysin family, has been shown to induce over 60% partial protection in immunized rabbits and mice when challenged with <i>F. hepatica</i> meta...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
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| Series: | Vaccines |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-393X/13/5/545 |
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| Summary: | Background/Objectives: In the past, FhSAP-2, an 11.5 kDa recombinant protein belonging to the <i>Fasciola hepatica</i> saposin-like/NK-lysin family, has been shown to induce over 60% partial protection in immunized rabbits and mice when challenged with <i>F. hepatica</i> metacercariae. However, despite FhSAP-2 being a promising vaccine candidate, its hydrophobic nature has made its purification a challenging process. The present study aimed to determine whether a modified 9.8 kDa variant of protein (mFhSAP-2), lacking a string of 16 hydrophobic amino acids at the amino terminus and a dominant Th1 epitope, could retain its immunogenic and Th1-inducing properties. Methods: RAW264.7 cells were stimulated with mFhSAP-2, and TNFα levels were determined. C57BL/6 mice were immunized with mFhSAP-2 alone or emulsified with Montanide ISA50. Total anti-mFhSAP-2 IgG subtypes, along with their avidity and titers, were measured using ELISA. The T cell proliferation index and levels of CD4+/CD8+ and IFNγ/IL-4 ratios were determined. Results: In vitro, mFhSAP-2 induced dose-dependent TNFα production in RAW264.7 cells. In vivo, mice immunized with mFhSAP-2 or mFhSAP-2+ISA50 developed high-avidity IgG2a and IgG2c antibodies at levels that were significantly higher than IgG1 antibody levels. However, the mFhSAP-2+ISA50 formulation induced higher and more homogenous antibody titers than mFhSAP-2, suggesting that an adjuvant may be required to enhance mFhSAP-2 immunogenicity. Immunization with mFhSAP-2+ISA50 also induced significantly higher activated CD4+/CD8+ T cell ratios and IFNγ/IL-4 ratios compared to naïve mice. Conclusions: Our results demonstrate that mFhSAP-2 retained its immunogenicity and Th1-polarizing properties, which were enhanced by the Montanide ISA50 adjuvant. The present study highlights the feasibility of inducing Th1-associated immune responses in mice using mFhSAP-2 as an antigen. Further studies are required to assess the potential application of the mFhSAP-2+ISA50 formulation as a vaccine against <i>F. hepatica</i> in natural hosts such as cattle and sheep, which could contribute to improved control and aid in the prevention and eradication of <i>F. hepatica</i> infection. |
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| ISSN: | 2076-393X |