Passive Transfer of Virus-Specific Antibodies Confers Protection against Reproductive Failure Induced by a Virulent Strain of Porcine Reproductive and Respiratory Syndrome Virus and Establishes Sterilizing Immunity

Abstract

Immune mechanisms mediating protective immunity against porcine reproductive and respiratory syndrome virus (PRRSV) are not well understood. The PRRSV-specific humoral immune response has been dismissed as being ineffective and perhaps deleterious for the host. The function of PRRSV antibodies in protective immunity against infection with a highly abortifacient strain of this virus was examined by passive transfer experiments in pregnant swine. All of a group of pregnant gilts (n = 6) that received PRRSV immunoglobulin (Ig) from PRRSV-convalescent, hyperimmune animals were fully protected from reproductive failure as judged by 95% viability of offspring at weaning (15 days of age). On the other hand, the totality of animals in a matched control group (n = 6) receiving anti-pseudorabies virus (PRV) Ig exhibited marked reproductive failure with 4% survival at weaning. Besides protecting the pregnant females from clinical reproductive disease, the passive transfer of PRRSV Ig prevented the challenge virus from infecting the dams and precluded its vertical transmission, as evidenced by the complete absence of infectious PRRSV from the tissues of the dams and lack of infection in their offspring. In summary, these results indicate that PRRSV-Igs are capable of conferring protective immunity against PRRSV and furthermore that these Igs can provide sterilizing immunity in vivo.

Alternative codon usage of PRRS virus ORF5 gene increases eucaryotic expression of GP5 glycoprotein and improves immune response in challenged pigs

“…Even if high titers of VN antibodies appeared at day 10 post-challenge, the viremia could not be prevented (data not shown) as previously observed [10,26,27]. Nevertheless, one report has demonstrated the protective effect of neutralizing antibodies and their potential to prevent viremia [9].…”

“…These findings suggest also that the amounts of GP5 synthesized in the infected cells, as well as conformation of the protein which may be influenced by the type of oligosaccharide side chains present on the molecule, are apparently crucial to trigger an effective humoral immune response to PRRSV. Since a correlation may exist amongst protection, clinical course of the disease, and seroneutralizing antibody titers [9,10], the present study was designed to increase the efficacy of genetic immunization against antigenic determinants of GP5.…”

Development of an experimental inactivated PRRSV vaccine that induces virus-neutralizing antibodies

“…On the other hand, Labarque et al showed that clearance of virus from lungs and serum coincides with the appearance of VN antibodies in serum and broncho-alveolar lavage fluid [10]. Moreover, experiments where passive transfer of VN antibodies was performed before infection with PRRSV showed that these antibodies are able to fully protect pigs against viremia and reproductive failure [14,20]. These data indicate that although other mechanisms may be involved in protection against PRRSV, the presence of sufficient amounts of VN antibodies contributes to clearance of viremia, can protect against reproductive failure and even can be sufficient to prevent infection.…”

“…The virus is present in a majority of swine producing countries around the world and gives rise to enormous economic losses in the swine industry [17]. Virus-neutralizing (VN) antibodies against PRRSV protect against viremia, virus replication in lungs, transplacental spreading of the virus and reproductive failure [12][13][14]20]. However, VN antibodies only appear in low amounts around 4 weeks or more after PRRSV infection, which is in contrast with the fast appearance of high amounts of nonneutralizing antibodies [7,34].…”

Different immunological features of two genetically distinct type 2 porcine reproductive and respiratory syndrome (PRRS) viruses

“…Thus, it stimulates delayed and weak protective immunity [i.e., serum virus neutralizing (SVN) antibody and interferon (IFN)-γ secreting T cells] which seldom appears until 3 to 4 weeks after infection (Meier et al, 2003;Faaberg et al, 2006;Vanhee et al, 2009). Passively acquired SVN antibody alone was proven to prevent viremia and reproductive failure in pigs challenged with virulent PRRSV strains (Osorio et al, 2002), suggesting the critical role of SVN antibody in the control of virus infection. Nonetheless, cell-mediated immunity (CMI) appears to be essential for the clearance of PRRSV since PRRSV has been detected in lungs and lymph nodes despite the presence of SVN antibodies in serum or bronchoalveloar lavage fluid (Wills et al, 1997;Labarque et al, 2000;Bierk et al, 2001).…”