Abstract
Porcine parvovirus 1 (PPV1) viral protein (VP) 2 is the primary antigen responsible for inducing specific protective immunity, so it is a desirable target for development of recombinant subunit vaccines to prevent PPV1 disease. The objective of this study was to evaluate repeated doses of a novel VP2-based PPV1 subunit vaccine, namely ReproCyc® ParvoFLEX, for safety in bred pigs and in offspring under experimental settings. Therefore, the investigation of safety at all breeding stages was evaluated in four independent studies involving: pre-breeding gilts (study A), breeding-age gilts and boars (study B), early and late gestating sows and offspring (study C) and lactating sows and offspring (study D). In all four studies, animals were free from PPV1 based on serology and PCR prior to inclusion. All studies comprised one or two vaccinated groups that received the PPV1 subunit vaccine and a negative control group. Thus, safety was established due to the lack of significant differences between the vaccinated groups and the corresponding unvaccinated (negative control) groups. Gilts, sows and boars were evaluated for local and systemic reactions after vaccination as well as for reproductive performance. The survival rate and average daily weight gain (ADWG) from birth to weaning in offspring was evaluated in studies C and D. Additionally, serology was determined in studies A, C and D. The vaccine was shown to be safe with no relevant significant differences between vaccinated and unvaccinated groups in any experiment. Therefore, repeated doses of ReproCyc® ParvoFLEX were safe in target animals at different stages of the reproductive cycle and in offspring, placing this vaccine as a suitable candidate for mass vaccination programs in breeding herds.
Highlights
Porcine parvovirus 1 (PPV1), recently designated as Ungulate parvovirus 1 [1], is one of the most important causes of reproductive failure in pigs worldwide and has implied serious economic losses in swine industries [2, 3]
While most commercial vaccines are based on chemical inactivation of tissue culture-derived virus adjuvanted with oil or aluminum hydroxide, several subunit vaccines have been described at the experimental level, with most based-on expression of the viral VP2 protein [2, 11, 13, 14]
The obtained results are in line with previous reported serological data, in which all sows which received an inactivated whole-PPV1 vaccine seroconverted within 5 weeks [10, 29]. These results indicate that vaccinated pigs seroconverted upon vaccination indicating exposure to the vaccine antigen
Summary
Porcine parvovirus 1 (PPV1), recently designated as Ungulate parvovirus 1 [1], is one of the most important causes of reproductive failure in pigs worldwide and has implied serious economic losses in swine industries [2, 3]. Infection with PPV1 causes stillbirth, mummification of the fetus, embryonic death and infertility (termed SMEDI syndrome) and delayed return of estrus [2, 4]. PPV1 is a small, non-enveloped virus with a single stranded DNA genome structure. It is composed of three structural proteins: viral protein (VP) 1, VP2 and VP3 [8]. The VP2 is generally considered the key protective antigen of PPV1 vaccines [9]
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