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Abstract Background Classical Swine Fever (CSF) is still one of the most economically important viral diseases of pigs. In endemic countries, the disease is controlled mostly through vaccination; hence, the availability of safe and effective vaccines is of utmost importance. Vaccines intended for application in developing countries must also be thermally stable, since the infrastructure needed to maintain a cold chain in those countries is usually lacking. Porvac® is a second-generation subunit marker vaccine against CSF that has demonstrates to be safe and protective. Previous studies have also shown that the vaccine is stable for 1 week at 37 oC and have a shelf life of at least 36 months at 2–8 oC. The aim of this work was to further explore the accelerated stability of Porvac® by assessing the physicochemical properties of the emulsion, and the safety and immunogenicity of the vaccine subjected to more drastic conditions of thermal stress: (1) 25 oC for 12 months; (2) 30oC and 37 oC for one month and (3) 15 days at 37 °C after the cap of the vials had been needle-punctured. Results The vaccine subjected to all these conditions did not show significant changes in the physicochemical properties of the emulsion; did not produce local or systemic adverse reactions in pigs, and the chromatographic profile of the recovered antigen was preserved. All vaccinated swine developed neutralizing antibody titers ≥ 1:1000 at 28 days post vaccination. Conclusions Porvac® is stable in all the experimental conditions tested, even after cap puncture, and retains the capacity to induce high titers of neutralizing antibodies, well above the threshold of protection. These results reinforce the robustness of the vaccine, and support its use as a very attractive alternative to modified live vaccines in developing countries endemic for CSF.

Live attenuated C-strain classical swine fever vaccines provide early onset protection. These vaccines confer effective protection against the disease at 5–7 days post-vaccination. It was previously reported that intramuscular administration of the Porvac® vaccine protects against highly virulent classical swine fever virus (CSFV) “Margarita” strain as early as seven days post-vaccination. In order to identify how rapidly protection against CSFV is conferred after a single dose of the Porvac® subunit vaccine E2-CD154, 15 swine, vaccinated with a single dose of Porvac®, were challenged intranasally at five, three, and one day post-vaccination with 2 × 103 LD50 of the highly pathogenic Cuban “Margarita” strain of the classical swine fever virus. Another five animals were the negative control of the experiment. The results provided clinical and virological data confirming protection at five days post-vaccination. Classical swine fever (CSF)-specific IFNγ T cell responses were detected in vaccinated animals but not detected in unvaccinated control animals. These results provided the first data that a subunit protein vaccine demonstrates clinical and viral protection at five days post-vaccination, as modified live vaccines.

Introducción. Porvac es una vacuna de subunidad contra la peste porcina clásica, cuyo principio activo es la proteína quimérica entre el antígeno E2 y el adyuvante mo- lecular CD154. Se ha demostrado su capacidad para evitar la transmisión transpla- centaria y proteger 7 días después de una dosis. El presente trabajo ha resumido los estudios de seguridad y eficacia de esta vacuna en diferentes edades y condiciones de manejo. Métodos. La vacuna se produjo en condiciones de BPM. Para los ensayos clínicos se emplearon cerdos Dubroc x Yorkshire. Por lo general, se empleó un esquema de 2 dosis los días 0 y 21 y se administraron 2 mL por vía intramuscular. La respuesta de anticuerpos neutralizantes se midió por NPLA. Los ensayos de desafío viral se realiza- ron en áreas controladas. Resultados. Se demostró la seguridad de Porvac en crías y en cerdas gestantes. No se observaron reacciones locales ni sistémicas. El número de crías, su peso y sobrevida fue similar en las cerdas vacunadas y sus controles. Se evidenció la capacidad de Porvac al inducir títulos de anticuerpos neutralizantes (AcN) protectores con diferentes esquemas. Los títulos de AcN calostrales (AcNC) en las crías de madres vacunadas con Porvac® o con VVA y Porvac fueron superiores a 1:200 hasta al menos 8 semanas. Los AcNC fueron suficientes para proteger a las crías frente al reto viral letal. Se demostró que los AcNC no interferían en la vacunación con Porvac en crías a partir de 15 días de nacidas. Finamente, los títulos de AcN inducidos por Porvac persistieron durante 9 meses por encima de 1:2000 y protegieron frente al retoviral. Conclusiones. Los resultados evidenciaron la seguridad de Porvac y su capacidad para inducir una inmunidad robusta y sostenida en los animales desde su nacimiento hasta la muerte, sin ventanas inmunológicas durante todo el ciclo productivo.