Anan Jongkaewwattana, Ph.D.
Virology and Antibody Technology Research Unit, National Center for Genetic Engineering and Biotechnology, NSTDA, THAILAND
Abstract:
Porcine epidemic diarrhea virus (PEDV) is a causative agent of a highly contagious enteric disease characterized by acute watery diarrhea, vomiting, and a high mortality rate in nursing piglets. Given that neonatal piglets are typically born without maternal antibodies, passive lactogenic immunity (sIgA and IgG) through ingestion of colostrum and milk is crucial for protection against PEDV. Several lines of evidence suggest that oral vaccines that mimic natural PEDV infection in pregnant sows can result in successful protection of suckling piglets by transmitting sufficient amounts of protective antibodies. PEDV that is attenuated in piglets but still capable of infecting swine intestinal cells thus serves as an ideal vaccine candidate.
We have recently developed a reverse genetics system based on an attenuated strain of PEDVAVCT12. Despite its high growth in cell culture, PEDVAVCT12 poorly infects intestinal cells in vivo. Moreover, PEDVAVCT12 is classified in the G1 genogroup, which is antigenically distinct from the G2 genogroup currently circulating globally. Most, if not all, PEDV in the G2 genogroup, however, are highly virulent to piglets and difficult to culture in vitro. To circumvent these issues, we have applied several approaches, such as novel pseudotyping system or Virus-like particle, to understand the mechanism underlying how the virulent G2 and cell-adapted G1 PEDV differently infect host cells. Based on these insights, we constructed and generated several variants of chimeric PEDV in which the spike (S) of PEDVAVCT12 is replaced by that of a cell-adapted, attenuated variant of PEDV in the G2 genogroup. In addition, the chimeric viruses were further manipulated to express foreign proteins such as mCherry fluorescent protein or secreted luciferase, which can be employed in several diagnostic assays such as microneutralization and antiviral screening. Taken together, we demonstrated that the genetic manipulation of PEDV provides a powerful tool to understand the biology of this important pathogen.