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Effect of Porcine Epidemic Diarrhea Virus Infectious Doses on Infection Outcomes in Naive Conventional Neonatal and Weaned Pigs.

ABSTRACT: Porcine epidemic diarrhea virus (PEDV) was identified in the United States (U.S.) swine population for the first time in April 2013 and rapidly spread nationwide. However, no information has been published regarding the minimum infectious dose (MID) of PEDV in different pig models. The main objective of this study was to determine the oral minimum infectious dose of PEDV in naïve conventional neonatal piglets and weaned pigs. A U.S. virulent PEDV prototype isolate (USA/IN19338/2013) with known infectious titer was serially ten-fold diluted in virus-negative cell culture medium. Dilutions with theoretical infectious titers from 560 to 0.0056 TCID50/ml together with a medium control were orogastrically inoculated (10ml/pig) into 7 groups of 5-day-old neonatal pigs (n = 4 per group) and 7 groups of 21-day-old weaned pigs (n = 6 per group). In 5-day-old pigs, 10ml of inoculum having titers 560-0.056 TCID50/ml, corresponding to polymerase chain reaction (PCR) cycle threshold (Ct) values 24.2-37.6, resulted in 100% infection in each group; 10ml of inoculum with titer 0.0056 TCID50/ml (Ct>45) caused infection in 25% of the inoculated pigs. In 21-day-old pigs, 10ml of inoculum with titers 560-5.6 TCID50/ml (Ct 24.2-31.4) resulted in 100% infection in each group while 10ml of inoculum with titers 0.56-0.0056 TCID50/ml (Ct values 35.3 ->45) did not establish infection in any pigs under study conditions as determined by clinical signs, PCR, histopathology, immunohistochemistry, and antibody response. These data reveal that PEDV infectious dose is age-dependent with a significantly lower MID for neonatal pigs compared to weaned pigs. This information should be taken into consideration when interpreting clinical relevance of PEDV PCR results and when designing a PEDV bioassay model. The observation of such a low MID in neonates also emphasizes the importance of strict biosecurity and thorough cleaning/disinfection on sow farms.

SUBMITTER: Thomas JT

PROVIDER: S-EPMC4594914 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Publications

Effect of Porcine Epidemic Diarrhea Virus Infectious Doses on Infection Outcomes in Naïve Conventional Neonatal and Weaned Pigs.

Thomas Joseph T JT Chen Qi Q Gauger Phillip C PC Giménez-Lirola Luis G LG Sinha Avanti A Harmon Karen M KM Madson Darin M DM Burrough Eric R ER Magstadt Drew R DR Salzbrenner Holly M HM Welch Michael W MW Yoon Kyoung-Jin KJ Zimmerman Jeffrey J JJ Zhang Jianqiang J

PloS one 20151006 10

Porcine epidemic diarrhea virus (PEDV) was identified in the United States (U.S.) swine population for the first time in April 2013 and rapidly spread nationwide. However, no information has been published regarding the minimum infectious dose (MID) of PEDV in different pig models. The main objective of this study was to determine the oral minimum infectious dose of PEDV in naïve conventional neonatal piglets and weaned pigs. A U.S. virulent PEDV prototype isolate (USA/IN19338/2013) with known i ...[more]

PMID: 26441071

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Project description:BackgroundPorcine epidemic diarrhea virus (PEDV) causes diarrhea in all ages of pigs with 50-100% mortality rates in neonatal piglets. In the United States, inactivated and subunit PEDV vaccines for pregnant sows are available, but fail to induce sufficient protection in neonatal piglets farrowed from PEDV naïve sows. A safe and efficacious live attenuated vaccine that can prime mucosal immune responses is urgently needed. In this study, we evaluated the safety and efficacy of two attenuated PEDV vaccine candidates, the emerging non-S INDEL PEDV strain PC22A at the 100th cell culture passage level - Clone no. 4 (P100C4) and at the 120th passage level (P120), in weaned pigs.ResultsFour groups of 40-day-old weaned pigs were inoculated orally with PEDV PC22A-P3 (virulent), -P100C4, -P120, and mock, respectively, and challenged with the P3 virus at 24 days post-inoculation (dpi). After inoculation, P3 caused diarrhea in all pigs with a high level of fecal viral RNA shedding. P100C4 and P120 did not cause diarrhea in pigs, although viral RNA was detected in feces of all pigs, except for one P100C4-inoculated pig. Compared with the P120 group, P3- and P100C4-inoculated pigs had higher serum PEDV-specific IgG and viral neutralizing (VN) antibody (Ab) titers at 14 dpi. After the challenge, no pigs in the P3 group but all pigs in the P100C4, P120, and mock groups had diarrhea. Compared with the P120 group, pigs in the P100C4 group had a more rapid decline in fecal PEDV RNA shedding titers, higher titers of serum PEDV-specific IgG, IgA, and VN Abs, and higher numbers of intestinal IgA Ab-secreting cells.ConclusionsPEDV PC22A P100C4 and P120 were fully attenuated in weaned pigs but failed to elicit protection against virulent P3 challenge. P100C4 induced higher PEDV-specific antibody responses than P120 post inoculation resulting in a greater anamnestic response post challenge. Therefore, P100C4 potentially could be tested as a priming vaccine or be further modified using reverse genetics. It also can be administered in multiple doses or be combined with inactivated or subunit vaccines and adjuvants as a PEDV vaccination regimen, whose efficacy can be tested in the future.

Dataset Information

Effect of Porcine Epidemic Diarrhea Virus Infectious Doses on Infection Outcomes in Naive Conventional Neonatal and Weaned Pigs.

Publications

Effect of Porcine Epidemic Diarrhea Virus Infectious Doses on Infection Outcomes in Naïve Conventional Neonatal and Weaned Pigs.

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