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Construction of Recombinant HVT Expressing PmpD, and Immunological Evaluation against Chlamydia psittaci and Marek's
Shanshan Liu1, Wei Sun2, Jun Chu3
1Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University,Beijing 100193, China; Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agricultural and Forestry Sciences, Beijing 100097, China.
Abstract:
Chlamydia psittaci (C. psittaci) is an obligate intracellular zoonotic pathogen that can be transmitted to humans from birds. No efficacious commercial vaccine is available for clearing chlamydial infection due to lack of potential vaccine candidates and effective delivery vehicles. Herpesvirus of turkeys (HVT) is an efficacious commercially available vaccine against Marek's Disease virus (MDV). In this study, a recombinant HVT-delivered vaccine against C. psittaci and Marek's disease was developed and examined. The 5'-terminus of pmpD gene (pmpD-N) encoding the N-terminal fragment of polymorphic membrane protein D of C. psittaci was inserted into a nonessential region of HVT genome using reverse genetics based on an infectious bacterial artificial chromosome (BAC) clone of HVT. The recombinant virus (rHVT-pmpD-N) was recovered from primary chicken embryo fibroblast (CEF) cells by transfection of modified HVT BAC DNA containing the pmpD-N gene. The rHVT-pmpD-N construct was confirmed to express PmpD-N by immunoblot and immunofluorescence. The rHVT-pmpD-N was stable during 20 passages in vitro. The growth kinetics of rHVT-pmpD-N was comparable to that of parental HVT in vitro and in vivo. One-day-old SPF chickens inoculated subcutaneously with rHVT-pmpD-N displayed increased PmpD-specific antibody levels and a vigorous PmpD-specific lymphocyte proliferation response using HVT vector or CEF cells as control. Furthermore, the percentage of CD4+ cells was significantly elevated in rHVT-pmpD-N-immunized birds as compared to the parental HVT. All chickens vaccinated with rHVT-pmpD-N or parental HVT were protected completely against challenge with a very virulent strain of Marek's Disease virus (MDV) RB-1B. Post challenge with C. psittaci CB7 strain, a significant decrease in respiratory distress, lesions and Chlamydia load was found in the rHVT-pmpD-N-vaccinated group compared to the parental HVT. In conclusion, our study suggests that the rHVT-pmpD-N live vaccine may be viable as a candidate dual vaccine that provides protection against both very virulent MDV and C. psittaci.
Insights
A new dual vaccine using a modified Herpesvirus of turkeys (HVT) successfully protected chickens against Marek's disease virus (MDV) and Chlamydia psittaci (C. psittaci). This recombinant HVT-delivered vaccine (rHVT-pmpD-N) offers a promising solution for poultry health.
Area of Science:
- Veterinary Virology
- Immunology
- Vaccine Development
Background:
- Chlamydia psittaci (C. psittaci) is a zoonotic pathogen causing avian chlamydiosis, with no current commercial vaccine.
- Herpesvirus of turkeys (HVT) is an established vaccine for Marek's disease virus (MDV).
- Developing a dual vaccine for both diseases is highly desirable for poultry health.
Purpose of the Study:
- To develop and evaluate a recombinant HVT-delivered vaccine expressing a C. psittaci antigen (pmpD-N).
- To assess the vaccine's efficacy against MDV and C. psittaci challenges.
- To investigate the immunological responses induced by the recombinant vaccine.
Main Methods:
- A recombinant HVT (rHVT-pmpD-N) was constructed by inserting the C. psittaci pmpD-N gene into the HVT genome using reverse genetics.
- The recombinant virus was characterized for gene expression, stability, and growth kinetics.
- Chickens were vaccinated and challenged with MDV and C. psittaci to evaluate protection and immune responses (antibody, lymphocyte proliferation, CD4+ T cells).
Main Results:
- The rHVT-pmpD-N vaccine was successfully constructed, stable, and expressed the target antigen.
- Vaccinated chickens showed increased PmpD-specific antibodies and lymphocyte proliferation.
- rHVT-pmpD-N vaccination provided complete protection against MDV and significantly reduced C. psittaci infection severity.
Conclusions:
- The recombinant HVT-delivered vaccine (rHVT-pmpD-N) is a viable candidate for a dual vaccine.
- This approach offers protection against both Marek's disease virus and Chlamydia psittaci.
- The study highlights the potential of HVT as a vector for developing novel poultry vaccines.
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