Assessing the functionality of viral entry-associated domains of porcine reproductive and respiratory syndrome virus during inactivation procedures, a potential tool to optimize inactivated vaccines

Abstract

-Porcine reproductive and respiratory syndrome virus (PRRSV) causes severe economic losses in the pig industry worldwide. Currently, vaccines based on inactivated PRRSV provide limited protection of pigs against infection, most likely because viral epitopes associated with the induction of neutralizing antibodies are not or poorly conserved during inactivation. To analyze the effect of inactivation procedures on the interaction of PRRSV with receptors involved in virus entry, a new assay was set up in this study. Viral entry-associated domains are most likely important for the induction of neutralizing antibodies, since neutralizing antibodies block interaction of PRRSV with cellular receptors. To investigate the interaction of PRRSV with the cellular receptors upon different inactivation procedures, attachment to and internalization of inactivated PRRSV into macrophages were monitored. AT-2 could not inactivate PRRSV completely and is therefore not useful for vaccine development. PRRSV inactivated with ultraviolet light, binary ethyleneimine and gamma irradiation, which all mainly have an effect at the genomic level, showed no difference compared to control live virus at all levels of virus entry, whereas PRRSV treated with formaldehyde, glutaraldehyde and pH changes, which all have a modifying effect on proteins, was not able to internalize into macrophages anymore. These results suggest that inactivation with methods with a main effect on the viral genome preserve PRRSV entry-associated domains and are useful for future development of an effective inactivated vaccine against PRRSV. Although PRRSV incubation at 37°C can completely inactivate PRRSV with preservation of entry-associated domains, this method is not recommended for vaccine development, since the mechanism is yet unknown.PRRSV / inactivation / vaccine / entry-associated domain / sialoadhesin

Inactivated virus vaccines from chemistry to prophylaxis: merits, risks and challenges

“…This has also been shown for PRRSV, where BEI could inactivate PRRSV with the preservation of the viral entry-associated domains [41]. Furthermore, the inactivation of FMDV with BEI did not affect the antigenity of FMDV [70].…”

“…PRRSV is not sensitive for AT-2 and could not be inactivated by it [41]. For PRRSV, disulfide brigdes between nucleocapsid proteins are important for virus infection, but as stated above, these disulfide bridges remain unaffected by AT-2 [55].…”

“…These domains may be important for the induction of protective immunity, as neutralizing antibodies are directed to the viral epitopes that are involved in the attachment to the PRRSV receptors and internalization into the host cell [40]. Since crosslinking of viral entry-associated domains might interfere with the subsequent presentation of viral-neutralizing epitopes to cells of the adaptive immune system, this procedure is not useful for inactivated PRRSV vaccine development [41]. Modification of the virion structure on inactivation with formaldehyde is also reported for FMDV [3], HIV [42] and canine parvovirus [43].…”

“…Similar to formaldehyde, glutaraldehyde could inactivate PRRSV but did not preserve the viral entry-associated domains and is therefore not useful for inactivated PRRSV vaccine development [41]. Glutaraldehyde was also shown to change the conformational structure of infectious bussal disease virus [52].…”

“…This procedure for virus inactivation for KV vaccines has been investigated for HIV [42], PRRSV [41] and RSV [53].…”