title: Unusual outcome of in utero infection and subsequent postnatal super-infection with different PCV2b strains.
abstract: VC2002, isolated from postweaning multisystemic wasting syndrome (PMWS)-affected pig, is a mixture of two porcine circovirus genotype 2b (PCV2b) viruses, K2 and K39. Preliminary experiments disclosed short-term adverse effects of K39, but not K2, on porcine foetuses. These findings led to the hypothesis that infection of immuno-incompetent foetuses with K2 confers a status of immunotolerance, and postnatal super-infection with K39 triggers PMWS. To explore this hypothesis, nine 55-day-old foetuses were inoculated in utero (three with K2-10(4.3)TCID50, three with K39-10(4.3)TCID50 and three with medium), and foeto-pathogenicity examined. At 21 days post-inoculation (dpi), K2 did not induce pathology, whereas pathological effects of K39 were evident. Twenty-four 45-day-old foetuses were subsequently inoculated to examine the long-term effect of K2, including six with K2-high dose-10(4.3)TCID50, six with K2-low dose-10(2.3)TCID50 and 12 mock-inoculated controls. Both doses resulted in five mummified foetuses and one live-born piglet each (69dpi). K2 was recovered from all mummies. K2 and K2-specific antibodies were not detected in serum of the two live-born piglets at birth, indicating full control of K2 infection. The K2-low dose-infected piglet was immunostimulated at day 2, but not the K2-high dose-infected piglet. Both non-stimulated and stimulated K2-infected piglets were super-inoculated with K39 at day 6 or 8 (taken as 0 days post super-inoculation). Low viral replication was observed in the non-stimulated K2-K39 piglet (up to 10(3.3)TCID50/g; identified as K39). In contrast, viral replication was extremely high in the stimulated K2-K39 piglet (up to 10(5.6)TCID50/g) and identified as K2, indicating that K2 infection is controlled during foetal life, but emerges after birth upon immunostimulation. However, none of the piglets showed any signs of PMWS.
authors.affiliation: Laboratory of Virology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
authors.forename: Dipongkor
authors.initials: D
authors.lastname: Saha
authors.forename: Uladzimir U
authors.initials: UU
authors.lastname: Karniychuk
authors.forename: Liping
authors.initials: L
authors.lastname: Huang
authors.forename: Marc
authors.initials: M
authors.lastname: Geldhof
authors.forename: Merijn
authors.initials: M
authors.lastname: Vanhee
authors.forename: David J
authors.initials: DJ
authors.lastname: Lefebvre
authors.forename: Peter
authors.initials: P
authors.lastname: Meerts
authors.forename: Richard
authors.initials: R
authors.lastname: Ducatelle
authors.forename: Jan V
authors.initials: JV
authors.lastname: Doorsselaere
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Nauwynck
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000276:immunology; D018173:Circoviridae Infections / Q000276:immunology / Q000821:virology*; D017925:Circovirus / Q000235:genetics / Q000472:pathogenicity*; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D011247:Pregnancy; D013552:Swine; D013553:Swine Diseases / Q000821:virology*
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral