Development of a recombinant antigen‐based ELISA for the sero‐detection of porcine lymphotropic herpesviruses

Abstract

Xenotransplantation using pigs as donor species carries a risk for the activation of latent porcine herpesviruses and potential transmission to the human recipient. The porcine lymphotropic herpesviruses (PLHV-1, -2, -3) are widespread in domestic pigs and closely related to the human gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus, causing lymphoproliferative disorders. PLHV-1 has been associated with a porcine post-transplantation lymphoproliferative disorder (PTLD), affecting miniature swine after experimental transplantation. In human xenotransplantation, PLHV might be transferred to the transplant recipient and cause PTLD or related diseases. The elimination of PLHV from donor pigs is therefore necessary, and requires the availability of nucleic-acid- and antibody-based detection methods. The N- and C-terminal parts (gB1 and gB2) of the glycoprotein B gene of PLHV-1, -2 and -3 were cloned and expressed in Escherichia coli. Antisera were raised in mice. PLHV PCR was performed as published earlier. An ELISA was developed, using recombinant glycoprotein B of PLHV-1 as the antigen, and used for the analysis of groups of pigs, differing by age and origin. Seropositivity ranged from 38% (piglets) to 90% (gilts) and 100% (breeding sows, miniature pigs and pigs for slaughter). In comparison, PCR products of PLHV were found in the blood of 0 to 80% of the pig groups. Additionally, a group of 12 piglets was tested repeatedly after birth until the age of 156 days. A decline of antibodies was found during the first 3 weeks after birth, followed by a rise in most pigs during the weeks thereafter. PLHV PCR products in the blood were only observed later than 3 weeks after birth. Newborn pigs may be passively protected by maternal antibodies against PLHV infection during the first 3 weeks post partum. The rise of antibody titers thereafter and the appearance of PLHV sequences in the blood possibly indicates de novo infection by contact to the infected mother sow. The PLHV-ELISA may aid in breeding PLHV-free pigs.