Key Gaps in the Knowledge of the Porcine Respiratory Reproductive Syndrome Virus (PRRSV)

Abstract

The porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important swine diseases in the world. It is causing an enormous economic burden due to reproductive failure in sows and a complex respiratory syndrome in pigs of all ages, with mortality varying from 2 to 100% in the most extreme cases of emergent highly pathogenic strains. PRRSV displays complex interactions with the immune system and a high mutation rate, making the development, and implementation of control strategies a major challenge. In this review, the biology of the virus will be addressed focusing on newly discovered functions of non-structural proteins and novel dissemination mechanisms. Secondly, the role of different cell types and viral proteins will be reviewed in natural and vaccine-induced immune response together with the role of different immune evasion mechanisms focusing on those gaps of knowledge that are critical to generate more efficacious vaccines. Finally, novel strategies for antigen discovery and vaccine development will be discussed, in particular the use of exosomes (extracellular vesicles of endocytic origin). As nanocarriers of lipids, proteins and nucleic acids, exosomes have potential effects on cell activation, modulation of immune responses and antigen presentation. Thus, representing a novel vaccination approach against this devastating disease.

Current Swine Respiratory Diseases Morphology in Intensive Swine Production in Serbia

“…The underlying PRRS virus has proved to be diffi cult to control, particularly in areas where there are many pig farms nearby (different family holdings, backyards) and the virus can move around pig farms via aerosols in the wind [82]. Because there are many strains, and new strains are continually evolving, having a recent outbreak of PRRS does not provide any immunity to the next PRRS virus entry and disease outbreak [83]. Various PRRS vaccines are available in Serbia and the modifi ed live PRRS vaccines have been the most frequently used.…”

“…However, it is well known that viral mutation can lead to more pathogenic strains and still, there is a lack of knowledge on how the porcine immune system interacts with all viral proteins. Highly divergent strains make it more diffi cult to develop a universal vaccine for the virus [83]. Several different vaccines against PRRSV have reached the market, and most of them rely upon the modifi ed live virus (MLV).…”

“…Cases have been reported in which new viruses have been introduced as a consequence of MLV vaccines. Presently available vaccines have many limitations in terms of heterologous protection, but some efforts have been made by combining new adjuvant formulations with modifi ed live viruses, DNA and peptide vaccines, as well as extracellular vesicles [83,91]. Many factors are important in disease epidemiology, the main are purchase of animals and semen from PRRS positive herds, increasing herd size and proximity to PRRS infected herds [3,87].…”

Seroprevalences of Classical Swine Fever Virus and Porcine Reproductive and Respiratory Syndrome Virus in Pigs in Hunan Province, China

“…Porcine reproductive and respiratory syndrome virus (PRRSV), an enveloped and single positive-stranded RNA virus, belongs to a member of the family Arteriviridae [7]. It has been determined the key etiologic agent responsible for porcine reproductive and respiratory syndrome (PRRS) since the early 1990s [8]. PRRSV has been epidemic more than 20 years in China, and administration of PRRSV vaccines has provided an e cient protection from the virus infection by reducing clinical signs, decreasing viremia and shortening duration of viral shedding [9].…”

Seroprevalences of classical swine fever virus and porcine reproductive and respiratory syndrome virus in pigs in Hunan Province, China

“…Porcine reproductive and respiratory syndrome virus (PRRSV), an enveloped and single positive-stranded RNA virus, belongs to a member of the family Arteriviridae [7]. It has been determined to be the key etiologic agent responsible for porcine reproductive and respiratory syndrome (PRRS) since the early 1990s [8]. PRRSV has been epidemic for more than 20 years in China, and the administration of PRRSV vaccines has provided e cient protection from the virus by reducing clinical signs, decreasing viremia and shortening the duration of viral shedding [9].…”