Efficacy of an inactivated genotype 2b porcine epidemic diarrhea virus vaccine in neonatal piglets

Abstract

Massive outbreaks of porcine epidemic diarrhea virus (PEDV) recurred in South Korea in 2013-2014 and affected approximately 40% of the swine breeding herds across the country, incurring a tremendous financial impact on producers and consumers. Despite the nationwide use of commercially available attenuated and inactivated vaccines in South Korea, PEDV has continued to plague the domestic pork industry, raising concerns regarding their protective efficacies and the need for new vaccine development. In a previous study, we isolated and serially cultivated a Korean PEDV epidemic strain, KOR/KNU-141112/2014, in Vero cells. With the availability of a cell culture-propagated PEDV strain, we are able to explore vaccination and challenge studies on pigs. Therefore, the aim of the present study was to produce an inactivated PEDV vaccine using the KNU-141112 strain and evaluate its effectiveness in neonatal piglets. Pregnant sows were immunized intramuscularly with the inactivated adjuvanted monovalent vaccine at six and three weeks prior to farrowing. Six-day-old piglets born to vaccinated or unvaccinated sows were challenged with the homogeneous KNU-141112 virus. The administration of the inactivated vaccine to sows greatly increased the survival rate of piglets challenged with the virulent strain, from 0% to approximately 92% (22/24), and significantly reduced diarrhea severity including viral shedding in feces. In addition, litters from unvaccinated sows continued to lose body weight throughout the experiment, whereas litters from vaccinated sows started recovering their daily weight gain at 7 days after the challenge. Furthermore, strong neutralizing antibody responses to PEDV were verified in immunized sows and their offspring, but were absent in the unvaccinated controls. Altogether, our data demonstrated that durable lactogenic immunity was present in dams administrated with the inactivated vaccine and subsequently conferred critical passive immune protection to their own litters against virulent PEDV infection.

Assessment of the safety and efficacy of an attenuated live vaccine based on highly virulent genotype 2b porcine epidemic diarrhea virus in nursing piglets

“…However, only inactivated/killed vaccines against G2b PEDV, which may be incapable of effectively controlling chronic PEDV enzootics, are commercially available in the domestic market. In our previous study, the double-dose immunization of pregnant sows with inactivated G2b vaccines conferred important passive protection to their litters (Baek et al, 2016). However, this study pointed out potential drawbacks of killed vaccines against PED in their effectiveness that does not fully mitigate mortality and morbidity rates of nursing piglets, probably owing to scant lactogenic immunity.…”

“…The onset of PEDV fecal shedding in animals from the vaccinated sows was recorded at different times (3-7 dpc), and its termination varied among piglets, lasting up to 2 weeks after challenge. A recent study revealed that giving sows twice inactivated killed G2b vaccines (K/K vaccination) enhanced the survival rate of piglets against G2b challenge from 0% to 93% and relieved the severity and morbidity of diarrhea, including the fecal shedding of PEDV (Baek et al, 2016). Considering these results, the maternal L/K/K vaccinations applied in the present study were more efficacious than K/K treatment in terms of absolute improvement in survival rate and the significant mitigation of diarrheal severity, including the quantity and duration of viral shedding in stool.…”

A newly isolated Chinese virulent genotype GIIb porcine epidemic diarrhea virus strain: Biological characteristics, pathogenicity and immune protective effects as an inactivated vaccine candidate

“…In addition to molecular evidence, antigenic variations between classical and emerging highly virulent (non-S INDEL) PEDV strains were demonstrated in several serological cross reactivity assays (Kim et al, 2015;Lin et al, 2015aLin et al, , 2015bWang et al, 2015). There are also some studies showed that the highly virulent (non-S INDEL) PEDV strains could provide piglets against homologous challenge (Baek et al, 2016;Lee et al, 2018;Lin et al, 2016b ;Park et al, 2018). Therefore, there is an urgent need for more research aimed at understanding the biological characteristics, pathogenicity, and immune protective effects of the field prevalent strain in the GII genogroup.…”

Vaccines for porcine epidemic diarrhea virus and other swine coronaviruses

“…Many of these are being assessed for their potential to mucosal immunity after oral administration. (Baek et al, 2016;Frederickson et al, 2014;Berube et al, 2015) Virions are inactivated with chemicals.…”

“…PEDV G2-b strains were responsible for recent severe PED epidemics in Asian countries and North America. Considering this fact, South Korean researchers (Baek et al, 2016) tested an inactivated vaccine based on serially cultured G2-b strain KOR/ KNU-141112/2014. Pregnant sows were immunized IM with the inactivated adjuvanted vaccine at 6 and 3 weeks prior to farrowing.…”