Codon Pair Deoptimization (CPD)-Attenuated PRRSV-1 Vaccination Exhibit Immunity to Virulent PRRSV Challenge in Pigs

Abstract

Commercially used porcine respiratory and reproductive syndrome (PRRS) modified live virus (MLV) vaccines provide limited protection with heterologous viruses, can revert back to a virulent form and they tend to recombine with circulating wild-type strains. Codon pair deoptimization (CPD) is an advanced method to attenuate a virus that overcomes the disadvantages of MLV vaccines and is effective in various virus vaccine models. The CPD vaccine against PRRSV-2 was successfully tested in our previous study. The co-existence of PRRSV-1 and -2 in the same herd demands protective immunity against both viruses. In this study, live attenuated PRRSV-1 was constructed by recoding 22 base pairs in the ORF7 gene of the E38 strain. The efficacy and safety of the CPD live attenuated vaccine E38-ORF7 CPD to protect against virulent PRRSV-1 were evaluated. Viral load, and respiratory and lung lesion scores were significantly reduced in animals vaccinated with E38-ORF7 CPD. Vaccinated animals were seropositive by 14 days post-vaccination with an increased level of interferon-γ secreting cells. In conclusion, the codon-pair-deoptimized vaccine was easily attenuated and displayed protective immunity against virulent heterologous PRRSV-1.

Evaluation and Determination of a Suitable Passage Number of Codon Pair Deoptimized PRRSV-1 Vaccine Candidate in Pigs

“…Codon pair de-optimized PRRSV-1 (E38-ORF7 CPD) was passaged in MARC-145 cells [ 29 , 31 , 34 ] and cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum (FBS) and 1% penicillin and streptomycin. The SNU 090485 (PRRSV-1; GenBank accession No: JN315686) was isolated from the lungs of aborted porcine fetuses from a farm in Gyeonggi-do, South Korea in 2009 and was used as the challenge virus.…”

“…The E38-ORF7 CPD attenuated virus, developed in our lab [ 31 ], was serially passaged in MARC-145 cells for up to 40 passages. Virus samples were collected at each 10th passage (after 10, 20, 30, and 40 passages).…”

“…The concept of CPD vaccines has been applied in several viruses, such as HIV-1, RSV, Poliovirus, and PRRSV [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. In a previous study, we successfully applied CPD on the NSP1 gene for PRRSV-2 [ 29 , 30 ] and the ORF7 gene of the PRRSV-1 [ 31 ]. The PRRSV-1 CPD vaccinated pigs were successfully protected from the heterologous challenge virus CBNU0495 (GenBank No:KY434183).…”

Current Status of Vaccines for Porcine Reproductive and Respiratory Syndrome: Interferon Response, Immunological Overview, and Future Prospects

“…The advanced method of Codon Pair Deoptimization (CPD) is also garnering attention for its ability to attenuate a virus, thereby mitigating the shortcomings of MLV vaccines regarding virulence reversion, for example. This method has demonstrated effectiveness in a variety of virus vaccine models [ 164 , 165 ]. A South Korean study applied CPD to introduce silent mutations at the end of the infectious clone, without altering the original amino acid sequences.…”

“…A South Korean study applied CPD to introduce silent mutations at the end of the infectious clone, without altering the original amino acid sequences. This intervention resulted in an increase in PRRSV-specific serum antibody levels and IFN-γ secreting cells two weeks post inoculation, and a notable reduction in gross pathological lesions in the vaccinated subjects [ 165 ]. Several European research groups have introduced a technique known as “infectious subgenomic amplicons (ISA)” utilizing the reverse genetics method.…”