Efficacy of intradermal UNISTRAIN® PRRS vaccination against NADC30/34-like PRRSV-2
Introduction
The porcine reproductive and respiratory syndrome (PRRS) is caused by Betaarterivirus suid (PRRSV), which can be classified into two distinct species, PRRSV-1 and PRRSV-2. According to the sequence analysis, the similarity between PRRSV-1 and PRRSV-2 is about 60%1. Recently, highly pathogenic NADC30/34-like PRRSV-2 strains have been reported in several Asian and American countries, accompanied by severe clinical signs, including respiratory disorders, fever and abortions2,3,4.
This study performed in collaboration with the National Taiwan University aimed to evaluate the humoral and cellular immunities and protectivity of UNISTRAIN® PRRS intradermal vaccination (a PRRSV-1 based live vaccine) against a Taiwan circulating NADC30/34-like PRRSV-2 strain.
Material and methods
10 five-week-old piglets seronegative to PRRSV were randomly separated into two groups.
· Immunized group (n=5): intradermally vaccinated with UNISTRAIN® PRRS (0.2mL).
· Control group (n=5): intradermally administrated 0.2mL of PBS.
Both product administrations were performed using the HIPRADERMIC® device at study week 0. At study week 5, all pigs were challenged with a Taiwan NADC30/34-like PRRSV-2 strain. Blood samples were collected at different timepoints (Fig. 1). Animals were euthanized 8 weeks after immunization and a lung evaluation was performed to determinate its lesion score.
Figure 1. Graphical representation of procedures performed: Vaccination on week 0, PRRSV inoculation on week 5, and blood sampling on weeks 0, 3, 5, 6, 7 and 8. Necropsy and tissue evaluation was performed on week 8.
Results
In immunized animals, PRRSV specific IgG (Fig 2A), NADC30/34-like PRRSV-2 neutralizing antibodies (Fig 2B), and vaccine-like interferon-γ producing cells were successfully elicited (Fig 2C). As expected, no immune response was detected in control animals.
Figure 2. Immune response after vaccination: A) Detection of PRRSV-specific Ig antibody titers by ELISA. The S/P ratio ≥0.4 was considered positive; B) Neutralizing antibody titer against the NADC30/34-like PRRSV 2. Blood samples were collected 5 weeks after immunization. Neutralizing assays were performed in porcine alveolar macrophages; C) Number of spots forming units (SFU) of the UNISTRAIN® PRRS viral-specific IFN-γ producing cells. Porcine peripheral blood mononuclear cells derived from blood samples were stimulated by the vaccine virus and analyzed by ELISPOT; Data is presented as the mean ± standard deviation (error bars). P-value shown as *(<0.05), **(0.01) or ***(<0.001) in the figure.
After the NADC30/34-like PRRSV-2 challenge, the immunized group showed reduction of fever (Fig 3A), reduction of viremia (Fig 3B), increased body weight gain (Fig 3C) and reduction of gross and microscopic lung lesions scores (Fig 3D and 3E) with respect to the control group.
Figure 3. Vaccination efficacy parameters analyzed after the PRRSV-2 challenge: A) Body temperature evolution (ºC); B) Body weight evolution (kg) during experimental phase (Vaccination on week 5 of age; Challenge on week 10 of age); C) Viral load in blood (viraemia) evolution after challenge; D) Gross lung lesion score; E) Microscopic lung lesion score; P-value shown as *(<0.05), **(0.01) or ***(<0.001) in the figure.
Conclusion
The results of this study show that vaccination with one dose of UNISTRAIN® PRRS ID (a PRRSV-1 based vaccine) could promote an immune response to both PRRSV species and provide substantial protection against the NADC30/34-like PRRSV-2 challenge (reduction of body temperature, viraemia, lung lesions and increase in body weight).
All of this suggest that UNISTRAIN® PRRS vaccine provides potential cross-protection against PRRSV-2.
References
1- Zimmerman JJ, Burrough ER, Karriker LA, Schwartz KJ, & Zhang J (2025). Diseases of Swine (12th ed.). John Wiley & Sons.
2- Zhou L, Wang Z, Ding Y, Ge X, Guo X, & Yang H (2015). NADC30-like Strain of Porcine Reproductive and Respiratory Syndrome Virus, China. Emerging infectious diseases, 21(12), 2256–2257. https://doi.org/10.3201/eid2112.150360
3- Ham S & Chae C (2025). Genetic and Pathogenic Characteristic of High Pathogenic Korean NADC34-Like Porcine Reproductive and Respiratory Syndrome Virus. Transboundary and Emerging Diseases, 1838580, 16 pages. https://doi.org/10.1155/tbed/1838580
4- Zhao HZ, Wang FX, Han XY, Guo H, Liu CY, Hou LN, Wang YX, Zheng H, Wang L, & Wen YJ (2022). Recent advances in the study of NADC34-like porcine reproductive and respiratory syndrome virus in China. Frontiers in microbiology, 13, 950402. https://doi.org/10.3389/fmicb.2022.950402
