Porcine Reproductive and Respiratory Syndrome (PRRS), Blue-Ear Pig Disease
3. Introduction
The PRRSV is an enveloped, single-stranded positive-sense RNA virus, approximately 50–65 nm in diameter that is classified in the order Nidovirales, family Arteriviridae, genus Arterivirus along with equine arteritis virus, lactate dehydrogenase-elevating virus of mice, and simian hemorrhagic fever virus. Properties of these viruses include the ability to induce prolonged viremia, persistent infections, and replication in macrophages. Being an enveloped virus, PRRSV survivability outside of the host is affected by temperature, pH and exposure to detergents. It is known that PRRSV can survive for extended intervals (>4 months) at temperatures ranging from −70 to −20 °C; however, viability decreases with increasing temperature. Regarding genetic diversity, there are two major prototypes of PRRSV, the European isolate (Lelystad virus, LV) and the North American isolate (VR-2332). Porcine reproductive and respiratory syndrome (PRRS) is an economically important disease of swine, estimated to cost the swine industry in USA approximately US$ 560 million per year. Clinical outbreaks of PRRS were first reported in the late 1980's in the USA; however, the etiology of the disease remained unknown. Clinical signs included severe reproductive failure, post-weaning pneumonia, growth reduction, decreased performance, and increased mortality. Similar clinical outbreaks were reported in Germany in 1990 and were widespread throughout Europe by 1991. In 1991, the etiologic agent, porcine reproductive and respiratory syndrome virus (PRRSV) was identified by investigators in The Netherlands and USA. Today, PRRSV is endemic in the global swine population; however, several countries, including Sweden, Switzerland, New Zealand, and Australia claim to be free of the disease (Cho and Dee, 2006).
4. Host Ranges and Animal Models
Pigs
5. Host Protective Immunity
Infected pigs develop a strong and rapid humoral response but these initial antibodies do not confer protection and can even be harmful by mediating an antibody-dependent enhancement of disease. In contrast, development of neutralising antibodies (NAs) is delayed and generation of cell-mediated immune responses, such as PRRSV-specific interferon (IFN)-gamma secreting cells, is initially erratic. In spite of this, induction of strong and rapid NAs and IFN-gamma responses seem to be required for effective vaccination. PRRSV strongly modulates the host's immune responses. The virus inhibits key cytokines, such as IFN-alpha, and may induce regulatory cytokines, such as interleukin (IL)-10 (Mateu and Diaz, 2008).
II. Vaccine Related Pathogen Genes
1. GP3
Gene Name :
GP3
Sequence Strain (Species/Organism) :
Porcine respiratory and reproductive syndrome virus
Molecule Role Annotation :
A mutation in the GP5 protein attenuates HP-PRRSV in piglets. This mutant (HuN4-F112) induces protection against challenge with wild type HP-PRRSV (Tian et al., 2009).
Description:
Vector pET21a expressed the major envelope glycoprotein (GP5) of porcine reproductive and respiratory syndrome virus (PRRSV) (Pirzadeh and Dea, 1998).
Efficacy:
Following a massive intratracheal challenge with the virulent IAF-Klop strain of PRRSV, DNA-vaccinated pigs were protected from generalized viraemia and the development of typical macroscopic lung lesions that were observed in unvaccinated, virus-challenged controls, as well as in pigs that were immunized with E. coli-expressed GST-ORF5 recombinant fusion protein (Pirzadeh and Dea, 1998).
Description:
Vector pCAGGS expressed the U-optiGP5 fusion gene was generated by linking optiGP5 downstream of ubiquitin. The Kozak sequence, GCCACC, served as the upstream start codon for all three fragments (Hou et al., 2008).
Efficacy:
Four of six pigs in the pCA-U-optiGP5 group were devoid of visible pathological changes that were present in other vaccinated and control animals after challenge (Hou et al., 2008).
Efficacy:
All immunized piglets developed neutralizing antibodies at 10 weeks after primary immunization, whereas there was no detectable neutralizing antibodies in piglets immunized with pCI-ORF5. Neutralizing antibodies are considered to be important in protection against PRRSV (Jiang et al., 2006).
Description:
Vector pIRES1neo expressed GP5, encoded by ORF5, the major envelope protein of the virus harboring neutralizing epitopes (Xue et al., 2004).
Efficacy:
After immunization and viral challenge, two of three pigs immunized with pIRESorf5/IFNgamma were protected from lung lesions that were present in other vaccinated and control animals (Cho and Dee, 2006).
Description:
Vector pIRES1neo expressed GP5, encoded by ORF5, the major envelope protein of the virus harboring neutralizing epitopes (Xue et al., 2004).
Efficacy:
After immunization and viral challenge, one of three pigs immunized with pIRESorf5/IL-2 was protected from lung lesions that were present in other vaccinated and control animals (Xue et al., 2004).
Description:
Vector pIRES1neo expressed N, encoded by ORF7, which forms the nucleocapsid protein of the virus, and it is likely to contain virus-specific T cell epitopes (Xue et al., 2004).
Efficacy:
After immunization and viral challenge, one of three pigs immunized with pIRESorf7/IL-2 was protected from lung lesions that were present in other vaccinated and control animals (Xue et al., 2004).
IV. References
1. An et al., 2018: An CH, Nazki S, Park SC, Jeong YJ, Lee JH, Park SJ, Khatun A, Kim WI, Park YI, Jeong JC, Kim CY. Plant synthetic GP4 and GP5 proteins from porcine reproductive and respiratory syndrome virus elicit immune responses in pigs. Planta. 2018; 247(4); 973-985. [PubMed: 29313103].
2. Cho and Dee, 2006: Cho JG, Dee SA. Porcine reproductive and respiratory syndrome virus. Theriogenology. 2006; 66(3); 655-662. [PubMed: 16730057].
3. Hou et al., 2008: Hou YH, Chen J, Tong GZ, Tian ZJ, Zhou YJ, Li GX, Li X, Peng JM, An TQ, Yang HC. A recombinant plasmid co-expressing swine ubiquitin and the GP5 encoding-gene of porcine reproductive and respiratory syndrome virus induces protective immunity in piglets. Vaccine. 2008; 26(11); 1438-1449. [PubMed: 18262692].
4. Jiang et al., 2006: Jiang Y, Xiao S, Fang L, Yu X, Song Y, Niu C, Chen H. DNA vaccines co-expressing GP5 and M proteins of porcine reproductive and respiratory syndrome virus (PRRSV) display enhanced immunogenicity. Vaccine. 2006; 24(15); 2869-2879. [PubMed: 16446016].
5. Mateu and Diaz, 2008: Mateu E, Diaz I. The challenge of PRRS immunology. Veterinary journal (London, England : 1997). 2008; 177(3); 345-351. [PubMed: 17644436].
6. Mokhtar et al., 2017: Mokhtar H, Biffar L, Somavarapu S, Frossard JP, McGowan S, Pedrera M, Strong R, Edwards JC, Garcia-Durán M, Rodriguez MJ, Stewart GR, Steinbach F, Graham SP. Evaluation of hydrophobic chitosan-based particulate formulations of porcine reproductive and respiratory syndrome virus vaccine candidate T cell antigens. Veterinary microbiology. 2017; 209; 66-74. [PubMed: 28228336].
7. Pirzadeh and Dea, 1998: Pirzadeh B, Dea S. Immune response in pigs vaccinated with plasmid DNA encoding ORF5 of porcine reproductive and respiratory syndrome virus. The Journal of general virology. 1998; 79 ( Pt 5); 989-999. [PubMed: 9603313].
8. Subramaniam et al., 2017: Subramaniam S, Piñeyro P, Derscheid RJ, Madson DM, Magstadt DR, Meng XJ. Dendritic cell-targeted porcine reproductive and respiratory syndrome virus (PRRSV) antigens adjuvanted with polyinosinic-polycytidylic acid (poly (I:C)) induced non-protective immune responses against heterologous type 2 PRRSV challenge in pigs. Veterinary immunology and immunopathology. 2017; 190; 18-25. [PubMed: 28778318].
9. Tian et al., 2009: Tian ZJ, An TQ, Zhou YJ, Peng JM, Hu SP, Wei TC, Jiang YF, Xiao Y, Tong GZ. An attenuated live vaccine based on highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) protects piglets against HP-PRRS. Veterinary microbiology. 2009; 138(1-2); 34-40. [PubMed: 19339125].
10. Xue et al., 2004: Xue Q, Zhao YG, Zhou YJ, Qiu HJ, Wang YF, Wu DL, Tian ZJ, Tong GZ. Immune responses of swine following DNA immunization with plasmids encoding porcine reproductive and respiratory syndrome virus ORFs 5 and 7, and porcine IL-2 and IFNgamma. Veterinary immunology and immunopathology. 2004; 102(3); 291-298. [PubMed: 15507312].
