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The objective of this study was to determine the protective properties of the Spanish MLV vaccine Amervac-PRRS® against porcine reproductive and respiratory syndrome virus (PRRSV) infection with the homologous wild-type strain5710. The experimental design comprised eighteen 3-week old pigs randomly divided into three groups. Animals fromgroup A received one dose of MLV vaccine Amervac-PRRS on days –42 and –21. Animals from groups B and C served as infected and uninfected controls, respectively. On day 0, pigs from groups A and B were intranasally challenged with homologous strain 5710 and 18 days after challenge all pigs were euthanized. The results reported in this study show that, although the titre of neutralizing antibodies elicited by vaccination was modest, MLV vaccine Amervac-PRRS® provided protection against homologous PRRSV infection and drastically reduced post-challenge viremia and completely block PRRSV dissemination to peripheral tissues.

This study was designed to evaluate the efficacy of an inactivated vaccine based on a European‐type strain of porcine reproductive and respiratory syndrome virus (prrsv) against the reproductive form of the syndrome in breeding gilts, and any congenital disease in their piglets. Five gilts were vaccinated twice, following the manufacturer's instructions, before they were inseminated. Nine additional gilts remained unvaccinated and served as positive (five gilts) and negative (four gilts) controls. A European wild‐type strain genetically divergent from the vaccine strain was used to challenge the five vaccinated and five unvaccinated positive control gilts at 90 days' gestation. The vaccination of the five seronegative gilts did not produce any clinical signs or adverse reactions. However, the vaccine failed to prevent the clinical signs associated with prrsv infection, viraemia after the challenge and transplacental infection of their piglets. The reproductive performance of the vaccinated gilts was similar to that of the unvaccinated positive controls, and there were no statistically significant differences in most of the parameters tested. However, the preweaning mortality of the piglets born to the vaccinated gilts was significantly lower than that of the piglets born to the positive control gilts.

In a previous study we obtained and characterized in vitro a novel pseudorabies virus (PRV) variant named gIp2 with a TK, gI/gE, 11k and 28k negative phenotype and a duplication of PK gene. The main objective of the present study was to determine the safety and efficacy, as a vaccine candidate, of this recombinant PRV. For this purpose, we used 24 PRV seronegative three weeks old piglets that were divided into five groups of treatment. Piglets of groups A and B were immunized twice with 10 6.5 and 10 5.5 TCID 50 of gIp2, respectively; pigs of group C were vaccinated twice with MLV vaccine Auskipra GN® and pigs of groups D and E were not immunized and served as infected and uninfected controls, respectively. Four weeks after the second immunization pigs of groups A, B, C and D were challenged by intranasal inoculation of 10 6 TCID 50 of the wildtype NIA-3 strain of PRV. No adverse reactions or clinical signs were observed in any group after immunization, indicating that the application of up to 10 times the conventional dose included in a commercial vaccine (i.e. 10 5.5 TCID 50 ) of gIp2 was safe in piglets. Additionally, the inoculation of gIp2 induced an immune response able to provide clinical and virological protection against pseudorabies virus after challenge. In conclusion, the use of gIp2 in piglets as a vaccine virus is safe and induces an immunity comparable to that exerted by commercially available vaccines.Additional key words: immunization, protection, safety, vaccine. Resumen Caracterización biológica de un virus de la enfermedad de Aujeszky recombinanteEn un estudio anterior, nuestro grupo de investigación había obtenido y caracterizado in vitro una nueva variante del virus de la enfermedad de Aujeszky (PRV) denominado gIp2, que presenta un fenotipo TK, gI/gE, 11K y 28K negativo, así como una duplicidad en el gen que codifica la PK. El principal objetivo de este estudio fue determinar la seguridad y eficacia, como candidato vacunal, de este virus recombinante. Para ello utilizamos 24 lechones de tres semanas de vida seronegativos al PRV, que fueron divididos en cinco grupos distintos. Los lechones de los grupos A y B fueron inmunizados dos veces con 10 6.5 y 10 5.5 DI 50 CT del virus gIp2; los lechones del grupo C fueron inmunizados dos veces con la vacuna comercial Auskipra GN® y, finalmente, los lechones de los grupos D y E permanecieron sin inmunizar y se utilizaron como testigos infectados y sin infectar, respectivamente. Cuatro semanas después de la segunda inmunización los lechones de los grupos A, B, C y D fueron desafiados por vía intranasal con 10 6 DI 50 CT de la cepa virulenta NIA-3. Tras la inmunización no se observaron reacciones adversas ni signos clínicos en ninguno de los grupos, indicando que la aplicación de hasta 10 veces la dosis convencional de una vacuna comercial (i.e.10 5.5 DI 50 CT) del virus gIp2 es segura en lechones. Además, la inoculación del virus gIp2 indujo una respuesta inmune capaz de estimular una protección clínica y virológica tras el desafío. En resumen...