Protective humoral immune response induced by an inactivated porcine reproductive and respiratory syndrome virus expressing the hypo-glycosylated glycoprotein 5

Abstract

Porcine reproductive and respiratory syndrome (PRRS) causes significant economic losses to the swine industry worldwide. Although inactivated and live vaccines are commercially available for the control of PRRS, both types of vaccine have not always proven successful in terms of generating a protective immune response, particularly in the case of inactivated vaccines. In this study, we tested whether an inactivated vaccine could induce a humoral immune response to PRRS during a homologous challenge. Amino acid substitutions were introduced into glycoprotein (GP) 5 of the FL12 strain of the PRRS virus (PRRSV) using site-directed mutagenesis with a pFL12 infectious clone. The substitutions led to double deglycosylation in the putative glycosylation moieties on GP5. The mutant virus was subsequently inactivated with binary ethylenimine. The efficacy of the inactivated mutant virus was compared with that of the inactivated wild-type PRRSV. Only the inactivated mutant PRRSV induced serum neutralizing antibodies at six weeks post-vaccination. The group that was administered the inactivated mutant virus twice exhibited a significantly increased neutralizing antibody titer after a challenge with the virulent homologous strain and exhibited more rapid clearing of viremia compared to other groups, including the groups that were administered either the inactivated mutant or wild-type virus only once and the group that was administered the inactivated wild-type virus twice. Histopathological examination of lung tissue sections revealed that the group that was administered the inactivated mutant virus twice exhibited significantly thinner alveolar septa, whereas the thickness of the alveolar septa of the other groups were markedly increased due to lymphocyte infiltration. These results indicated that the deglycosylation of GP5 enhanced the immunogenicity of the inactivated mutant PRRSV and that twice administrations of the inactivated mutant virus conferred better protection against the homologous challenge. These findings suggest that the inactivated PRRSV that expresses a hypo-glycosylated GP5 is a potential inactivated vaccine candidate and a valuable tool for controlling PRRS for the swine industry.

Ability of ELISAs to detect antibodies against porcine respiratory and reproductive syndrome virus in serum of pigs after inactivated vaccination and subsequent challenge

“…The inactivated PRRS vaccine used in group V belongs to the same subgroup of type 1 as the Lelystad strain with 99% homology to this strain [11]. This was confirmed in our laboratory as well (data not shown).…”

“…Some studies are available that refer to protective immune response after vaccination against PRRSV with a novel killed vaccine [11, 12]. Another study used a killed PRRSV vaccine in previously infected pigs which resulted in increased serum neutralization Ab titers and interferon γ producing cells, although the virus shedding was not affected [18].…”

“…Measured with the IDEXX ELISA, an antibody response can be detected beginning between days 9 and 12 after PRRSV infection or vaccination with attenuated PRRSV live vaccines [2, 6–9] and lasting at least until day 120 after vaccination or challenge [10]. Although the application of certain inactivated PRRSV vaccines seems to prime the immune system and can, according to some studies, lead to a faster and more effective immune response after PRRSV infection [11, 12], no antibody response has been observed with the IDEXX ELISA after vaccination with inactivated PRRSV vaccines [10, 13]. Therefore the question arises as to whether or not other ELISAs are capable of detecting PRRSV specific Ab in the serum of pigs vaccinated with an inactivated PRRSV vaccine.…”

Expression of antigenic epitopes of porcine reproductive and respiratory syndrome virus (PRRSV) in a modified live-attenuated porcine circovirus type 2 (PCV2) vaccine virus (PCV1-2a) as a potential bivalent vaccine against both PCV2 and PRRSV

“…In the present study, we constructed four PCV1-2a chimeric viruses expressing B-cell linear epitopes of PRRSV, which were previously demonstrated to be immunogenic against PRRSV (de Lima et al, 2006;Lee et al, 2014;Mulupuri et al, 2008;Plagemann, 2004b;Vanhee et al, 2011). During the natural course of the disease, PRRSV-specific antibodies typically appear approximately 7-10 dpi.…”

Inactivated porcine reproductive and respiratory syndrome virus vaccine adjuvanted with Montanide™ Gel 01 ST elicits virus-specific cross-protective inter-genotypic response in piglets

“…c o m / l o c a t e / v e t m i c vaccine has the intrinsic risk of reversion to a virulent strain (Kwang et al, 1999). Though PRRS KV vaccine is safe to use in pigs, it elicits insufficient immunity in pigs (Lee et al, 2014). Overall, commercially available PRRS KV vaccine does not induce strong required immune response, and thus failed to protect pigs against viremia to homologous as well as heterologous viral challenges (Nilubol et al, 2004;Scortti et al, 2007;Zuckermann et al, 2007).…”