Detection of immunoglobulin (Ig) A antibodies against porcine epidemic diarrhea virus (PEDV) in fecal and serum samples

Priscilla F Gerber,Tanja Opriessnig

doi:10.1016/j.mex.2015.10.001

Priscilla F Gerber, Tanja Opriessnig

Open Access

https://doi.org/10.1016/j.mex.2015.10.001

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Abstract

Many assays for detection of antibodies against porcine epidemic diarrhea virus (PEDV) are based on detection of neutralizing antibodies or immunoglobulin (Ig) G in serum samples. However, due to the particular features of the mucosal immune system, presence of serum antibodies against enteric pathogens, such as PEDV, not always correlates with protection. In contrast, anti-PEDV IgA antibodies correlate with protection against subsequent challenges. An indirect PEDV IgA ELISA was previously developed to monitor IgA levels in colostrum and milk samples. In the present paper we describe an adaptation of the protocol for detection of IgA antibodies in serum and fecal samples.•The adapted protocol will aid in future assessment of protective levels of humoral response against PEDV infection by measuring IgA levels in serum and fecal samples.•Fecal samples are non-invasive and easy to collect at any time by animal caretakers and therefore offering advantages over the serum sample collection procedure.•A strong positive correlation between the anti-PEDV levels in fecal and serum samples was identified; however, detection of IgA antibodies was often more successful in serum than in paired fecal samples due to overall lower sample-to-positive (S/P) ratios for the latter sample type.

Highlights

porcine epidemic diarrhea virus (PEDV), a member of the genus Alphacoronavirus in the family Coronaviridae, causes acute diarrhea, vomiting, and dehydration in pigs of any age with often high mortality in neonatal piglets
Presence or absence of PEDV infection was confirmed by RT-PCR on rectal swabs [2,3] and by an IgG immunofluorescence assay (IFA) in serum samples as routinely performed at the Iowa State University Veterinary Diagnostic Lab (ISU-VDL)
PEDV infection has resulted in high economic losses in Asian pig industries, the disease has been reported in 2013 in North America and in 2014 in South America [5] and recent outbreaks have been described in Europe during 2015

Summary

Method details

The present study was designed to adapt an indirect ELISA protocol for the detection of antiporcine epidemic diarrhea virus (PEDV) IgA in serum and fecal samples to compare the capability of detection of IgA in the two different matrix types. Fresh fecal samples and controls were diluted at 1:10 w/v (0.1 g in 0.9 ml) with assay diluent, thoroughly homogenized by vortexing for 30 s and centrifuged at 4000 Â g for 10 min. Serum samples and controls were diluted at 1:100 (3 ml in 300 ml) with assay diluent. Clarified diluted fecal samples or controls were added to each well and incubated at 4 8C for 16–18 h. Diluted samples or controls (100 ml) were added to each well and incubated at 37 8C for 1 h. For the IgA ELISA on fecal samples an S/P ratio less than 0.13 was considered negative and an S/P ratio higher or equal to 0.13 was considered positive. For serum samples an S/P ratio less than 0.14 was considered negative and an S/P ratio higher or equal to 0.14 was considered positive

Method validation

Findings

Background