Veterinary Immunology and Immunopathology 148 (2012) 116–125 Contents lists available at SciVerse ScienceDirect Veterinary Immunology and Immunopathology j o ur nal ho me p age: w ww.elsevier.com/locate/vetimm Effect of the host cell line on the vaccine efficacy of an attenuated porcine reproductive and respiratory syndrome virus Gabriela Calzada-Nova a , Robert J. Husmann a , William M. Schnitzlein a , Federico A. Zuckermann a,b,∗ a Department of Pathobiology, College of Veterinary Medicine, University of Illinois, 2001 South Lincoln Avenue, Urbana, IL, USA b Aptimmune Biologics, Inc., 60 Hazelwood Dr., Urbana, IL, USA a r t i c l e i n f o Keywords: Host cell Cell line Adaptation Vaccine Efficacy Macrophage Attenuated virus PRRSV Viremia ZMAC cells a b s t r a c t The abilities of the modified-live Prime Pac (PP) strain of porcine reproductive and respira- tory syndrome virus (PRRSV), propagated in either traditional simian cells (MARC-145) or in a novel porcine alveolar macrophage cell line (ZMAC), to confer pigs protection against subsequent PRRSV challenge were compared. Eight week-old pigs were injected with PP virus grown in one of the two cell types and then exposed 4 weeks later to the “atypical” PRRSV isolate NADC-20. Control animals were similarly challenged or remained PRRSV- naïve. While the average adjusted body weight (aabw) of the strict control group increased 22% by 10 days post challenge (pc), this value for the non-vaccinated, challenged group dropped 4%. In contrast, prior immunization with PP virus, regardless of its host cell source, ameliorated this effect by affording a >9% rise in aabw. Likewise, nearly equivalent pro- tection was extended to both groups of vaccinates in regards to the temporal elimination of their pc clinical distress and viremia. However, the PP virus propagated in ZMAC cells appeared to be more efficacious since four of the six pigs receiving this biologic cleared the challenge virus from the their lungs by 10 days pc as compared to only one member of the other vaccinated group. Notably, the predominant quasispecies in the ZMAC cell-prepared PP virus stock contained a highly conserved N-glycosylation site at position 184 in its gly- coprotein 2 while this entity was underrepresented in the MARC-145 cell grown biologic. Since glycoprotein 2 is involved in infectivity, such additional glycosylation may enhance virus replication in porcine alveolar macrophages. © 2012 Elsevier B.V. All rights reserved. 1. Introduction During the last twenty years, porcine reproductive and respiratory syndrome (PRRS) has emerged as a major eco- nomic problem for the pork industry worldwide (Lunney et al., 2010). The etiological agent, PRRS virus (PRRSV), has a positive-strand RNA genome and is a member of the Arteriviridae family. PRRSV infections can result in ∗ Corresponding author at: Department of Pathobiology, College of Veterinary Medicine, University of Illinois, 2001 South Lincoln Avenue, Urbana, IL, USA. Tel.: +1 217 333 7767; fax: +1 217 244 7421. E-mail address: fazaaa@illinois.edu (F.A. Zuckermann). decreased farrowing rates, increased pre-weaning mor- talities and respiratory distress in finishing pigs (Rossow, 1998). The severity of the disease depends on the degree of virulence of the virus isolate, the age of the afflicted animal and the status of concomitant infections ranging from mild to severe presentations with the latter resulting in high rates of mortality (Mengeling et al., 2000; Halbur, 2003; Zimmerman et al., 2006; Zhou et al., 2008). The host immune response to PRRSV infection is characterized by polyclonal B cell activation (Lamontagne et al., 2001; Butler et al., 2007), a robust induction of virus-specific non-neutralizing antibodies and a relatively weak genera- tion of virus-specific IFN- secreting cells whose presence gradually increases during the ensuing, several months 0165-2427/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.vetimm.2012.05.008