Pathogenicity of porcine deltacoronavirus (PDCoV) strain NH and immunization of pregnant sows with an inactivated PDCoV vaccine protects 5-day-old neonatal piglets from virulent challenge

Transbound Emerg Dis. 2020 Mar;67(2):572-583. doi: 10.1111/tbed.13369. Epub 2019 Sep 30.

Abstract

In this study, the pathogenicity of porcine deltacoronavirus (PDCoV) strain NH (passage 10, P10) was evaluated. We found that PDCoV strain NH is enteropathogenic in 5-day-old pigs. Pathogenicity experiments provided a challenge model for studying the protection efficiency of passive immunity. In order to investigate the protective efficacy of passive immunity in newborn piglets, pregnant sows were vaccinated with either a PDCoV-inactivated vaccine at the Houhai acupoint (n = 5) or DMEM as a negative control (n = 2) using a prime/boost strategy 20 and 40 days before delivery. PDCoV spike (S)-specific IgG and neutralizing antibody (NA) responses were detected in immunized sows and piglets born to immunized sows. PDCoV spike (S)-specific sIgA was also detected in the colostrum and milk of immunized sows. Five days post-farrowing, piglets were orally challenged with PDCoV strain NH (105 TCID50 /piglet). Severe diarrhoea, high levels of viral RNA copies and substantial intestinal villus atrophy were detected in piglets born to unimmunized sows. Only 4 of 31 piglets (12.9%) born to immunized sows in the challenge group displayed mild to moderate diarrhoea, lower viral RNA copies and minor intestinal villi damage compared to piglets born to unimmunized sows post-challenge. Mock piglets exhibited no typical clinical symptoms. The challenge experiment results indicated that the inactivated PDCoV vaccine exhibited 87.1% protective efficacy in the piglets. These findings suggest that the inactivated PDCoV vaccine has the potential to be an effective vaccine, providing protection against virulent PDCoV.

Keywords: inactivated PDCoV vaccine; passive immunity; pathogenicity; piglets; sows.

MeSH terms

  • Animals
  • Antibodies, Neutralizing / immunology
  • Antibodies, Viral / immunology*
  • Colostrum / immunology
  • Coronavirus / immunology*
  • Coronavirus / pathogenicity
  • Coronavirus Infections / prevention & control
  • Coronavirus Infections / veterinary*
  • Coronavirus Infections / virology
  • Diarrhea / veterinary
  • Diarrhea / virology
  • Female
  • Immunization / veterinary*
  • Milk / immunology
  • Pregnancy
  • Swine
  • Swine Diseases / prevention & control*
  • Swine Diseases / virology
  • Vaccines, Inactivated / administration & dosage
  • Viral Vaccines / administration & dosage*
  • Virulence

Substances

  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Vaccines, Inactivated
  • Viral Vaccines