Characterization of the Humoral Immune Response to Porcine Reproductive and Respiratory Syndrome (PRRS) Virus Infection

Abstract

The development of the humoral immune response against porcine reproductive and respiratory syndrome (PRRS) virus was monitored by an indirect fluorescent antibody (IFA) test, immunoperoxidase monolayer assay (IPMA), enzyme-linked immunosorbent assay (ELISA), and serum virus neutralization (SVN) test over a 105-day period in 8 pigs experimentally infected with ATCC strain VR-2402. Specific antibodies against PRRS virus were first detected by the IFA test, IPMA, ELISA, and the SVN test 9-11, 5-9, 9-13, and 9-28 days postinoculation (PI), respectively, and reached their maximum values by 4-5, 5-6, 4-6, and 10-11 weeks PI, respectively, thereafter. After reaching maximum value, all assays showed a decline in antibody levels. Assuming a constant rate of antibody decay, it was estimated by regression analysis that the ELISA, IFA, IPMA, and SVN antibody titers would approach the lower limits of detection by approximately days 137, 158, 324, and 356 PI, respectively. In this study, the immunoperoxidase monolayer assay appeared to offer slightly better performance relative to the IFA test, ELISA, and SVN test in terms of earlier detection and slower rate of decline in antibody titers. Western immunoblot analysis revealed that antibody specific for the 15-kD viral protein was present in all pigs by 7 days PI and persisted throughout the 105-day observation period. Initial detection of antibodies to the 19-, 23-, and 26-kD proteins varied among pigs, ranging from 9 to 35 days PI. Thereafter, the antibody responses to these 3 viral proteins of PRRS virus continued to be detected throughout the 105-day study period.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the carrier state in porcine reproductive and respiratory syndrome virus infection

“…Viral and mock ( cell) antigens were prepared simultaneously, as described previously (Yoon et al, 1995) with some modifications. Cells were subjected to 2 freeze-thaw (minus 80° C/22° C) cycles.…”

Diagnostic Performance of a Reverse Transcription-Polymerase Chain Reaction Test for Porcine Reproductive and Respiratory Syndrome Virus

“…The use of PI day 7 samples as positive controls was justified on the basis of our experience with PRRS virus and of numerous publications indicating that pigs infected with PRRS virus are viremic on PI day 7. 3,5,[13][14][15]19,21 Of the 102 experimentally infected animals, VI from PI day 7 serum samples was attempted on 85 pigs, and all were VI positive. VI was not done on the remaining 17 pigs, but all were ELISA positive by PI day 21 or earlier.…”

“…7 The stx primer pairs are 90% homologous to sequences in stx1 and stx2 genes. 14,21 The stx primers generated a 230-bp fragment in positive PCR assays. Positive controls were DNA from enterohemorrhagic E. coli O157: H7 and a calf strain of attaching and effacing E. coli (serotype O5:NM).…”

“…Of the 195 negative pigs, 102 were intranasally inoculated under experimental conditions with the same lot of PRRS virus (isolate ISU-P). 21 Serum samples collected on postinoculation (PI) day 7 were used as known positive samples to estimate diagnostic sensitivity. The use of PI day 7 samples as positive controls was justified on the basis of our experience with PRRS virus and of numerous publications indicating that pigs infected with PRRS virus are viremic on PI day 7.…”

Evaluation of Enzyme-Linked Immunosorbent Assay (ELISA)and Immunofluorescent Antibody (IFA) Test for the Detection of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Antibody in Pigs from Conventional Farms.

“…Recently, however, the ELISA has been developed and has increasingly displaced the IFA for diagnostic assay because of its simple protocol and high sensitivity [6,11,22,30]. The judgement of the ELISA results was analyzed in gnotobiotic pigs experimentally infected with the PRRSV and a cut-off point was set at an S/P ratio of 0.4 [30]. However, conventional pigs reared at commercial farms often show a non-specific reaction in serological tests due to the antigenic stimuli of various microorganisms.…”