Date Full Report Received04/29/2015
Date Abstract Report Received04/29/2015
InvestigationInstitution: Iowa State University
Primary Investigator: Luis Gimenez-Lirola
Co-Investigators: Jeffrey Zimmerman, Kyoung-Jin Yoon, Chong Wang, Darin Madson, Jianqiang Zhang, Rodger Main, John Johnson, Korakrit Poonsuk
Funded ByNational Pork Board
Through the proposed approach we tried to the answers PEDV serology questions from the field regarding the association between maternal anti-PEDV antibody and protection of neonates against PEDV. It would allow producers to better assure the sows have been effectively exposed and thereby their pigs effectively protected through colostrum and milk.
The primary objective of this project was to determine correlates between maternal anti-PEDV antibody and protective immunity against PEDV in neonates. The objective was accomplished through two phases of experimental research:
Phase 1. Evaluation of PEDV protection in the context of maternal immunity against PEDV challenge in piglets from immune sows.
• Newborn piglets from 8 PEDV-immune sows were allowed to suckle colostrum for 2 days before they were inoculated with 10^3 TCID50 PEDV. No challenged piglets from 2 PEDV negative sows were included as negative control group. Piglets were monitored for 14 days to observe clinical outcomes, including PEDV real time reverse transcriptase PCR (rRT-PCR) of piglets feces (analyzed as converted CT), survival (%), daily weight, (analyze as weight changes), and daily temperature.
• Specific anti-PEDV antibodies (IgG, IgA, and virus neutralizing) were found in the colostrum and milk of immune sows but not in those from naïve negative control sows. Subsequently, significant levels of specific PEDV antibodies (IgG, IgA, and VN) were found in serum from piglets born to immune sows. Thus, serological results for neonatal piglets that have received colostrum/milk provide a crude means of assessing of transfer and decline of maternal antibodies.
• Results showed that antibody-based detection methods are applicable to monitoring sows for PEDV exposure and evaluate their immune status. The determination of antibody isotypes (IgG, IgA and VN) in serum and colostrum/milk specimens provided valuable information regarding dynamic, timing, sensitivity and source of humoral response against PEDV. Particularly remarkable is the specific role of mucosal IgA and VN antibodies as first and principal line of defense against PEDV infection.
• Following inoculation with PEDV, virus shedding was significantly reduced in piglets that had received passively transferred immunity. Specifically, a linear relationship between colostrum/milk IgA and virus shedding from piglets were observed where piglets receiving milk with higher IgA titers had lower PEDV shedding in feces, suggesting that IgA local gut (milk) antibodies play a crucial role in the clearance of the virus.
Phase 2. Evaluation of PEDV protection in naïve piglets administered specific levels of anti-PEDV antibody.
• Each litter of piglets from 7 PEDV negative sows were administered (intraperitoneally) with 6 specific levels of anti-PEDV antibody [0 (saline solution), 1:80; 1:160; 1:320; 1:640; 1:1280] harvested from phase 1, and subsequently inoculated with 10^3 TCID50 PEDV. Piglets were monitored as in Phase 1.
• PEDV-specific antibody (IgG, IgA, and VN) levels in sera of pigs receiving immune serum intraperitoneally were significantly higher than those that received control saline solution (PBS).
• The proportion of pigs shedding PEDV after inoculation was also lower in pigs receiving any of the 5 levels of immune serum compared to those receiving the control saline solution. However, it was difficult to establish a quantitative correlation between specific antibody levels and protection in terms on reduction of the virus shedding.
• Mortality data reported in that experiment indicate that systemic (serum) antibody titers do not correlate with protection of piglets against PEDV.