Field evaluation of novel plant-derived porcine circovirus type 2 vaccine related to subclinical infection.

BACKGROUND: The objective of this field trial was to evaluate the efficacy of a new plant-based porcine circovirus type 2a (PCV2a) vaccine. This vaccine was a recombinant capsid subunit PCV2a vaccine based on the Nicotiana benthamiana expression system. METHODS: Three farms were selected for the study based on their history of subclinical PCV2 infection. A total of 40 18-day-old pigs were randomly allocated to either vaccinated or unvaccinated groups (20 pigs per group; 10 = male and 10 = female). Pigs received a 2.0-mL dose of the plant-based PCV2a vaccine intramuscularly at 21 days of age in accordance with the manufacturer's recommendations, whereas unvaccinated pigs were administered a single dose of phosphate buffered-saline at the same age. RESULTS: Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on all three of the farms. Vaccination of pigs with a plant-based PCV2a vaccine induced high levels of neutralizing antibodies titres against PCV2d and PCV2d-specific interferon-γ secreting cells which resulted in the reduction of PCV2d viral load and reduced lymphoid lesions severity. CONCLUSIONS: The results of this field trial demonstrated cross-protection of PCV2d by a plant-based PCV2a vaccine and a positive effect of pig growth performance with vaccination.

Comparative growth performance of 3 types of combination vaccines containing porcine circovirus 2 and Mycoplasma hyopneumoniae under field conditions.

The objective of this field trial was to compare the effect of 3 different types of combination vaccines on growth performance in pigs under field conditions. The vaccines compared were: a trivalent vaccine containing porcine circovirus type 2a and 2b (PCV-2a/b); and Mycoplasma hyopneumoniae; a mixable bivalent vaccine containing PCV-2a and M. hyopneumoniae; and a ready-to-use bivalent vaccine containing PCV-2a and M. hyopneumoniae. Two farms were selected on the basis of their history of subclinical PCV-2d infection and enzootic pneumonia. A total of 120 pigs on each farm was randomly divided into 4 groups of 30 pigs each. The trivalent-vaccinated group from both farms outperformed each bivalent-vaccinated group in terms of growth performance. Growth performance was significantly improved during the fattening period (70 to 175 d of age) in the mixable bivalent-vaccinated group compared with the ready-to-use bivalent-vaccinated group on 1 farm. The trivalent-vaccinated group elicited higher levels of neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC) against PCV-2d, while simultaneously decreasing the levels of PCV-2d load in blood when compared with the mixable and ready-to-use bivalent-vaccinated groups. The trivalent-vaccinated group also elicited higher levels of IFN-γ-SC against M. hyopneumoniae and lower levels of M. hyopneumoniae load in the larynx when compared with the mixable and ready-to-use bivalent-vaccinated groups. The results of the present study demonstrated that a trivalent vaccine containing PCV-2a/b and M. hyopneumoniae resulted in a more productive parameter, higher immune responses, and less blood-viral and mycoplasmal larynx-loads when compared with the mixable and ready-to-use bivalent vaccines despite the presence of ongoing subclinical PCV-2d infection and enzootic pneumonia on the farms.

L'objectif de cet essai de terrain était de comparer l'effet de trois différents types de vaccins combinés sur les performances de croissance chez les porcs dans des conditions de terrain. Les vaccins comparés étaient : un vaccin trivalent contenant des circovirus porcins de type 2a et 2b (PCV-2a/b) et Mycoplasma hyopneumoniae; un vaccin bivalent mélangeable contenant PCV-2a et M. hyopneumoniae; et un vaccin bivalent prêt à l'emploi contenant le PCV-2a et M. hyopneumoniae. Deux fermes ont été sélectionnées sur la base de leurs antécédents d'infection subclinique par le PCV-2d et de pneumonie enzootique. Un total de 120 porcs dans chaque ferme a été divisé au hasard en quatre groupes de 30 porcs chacun. Le groupe vacciné par les trivalents des deux fermes a surpassé chaque groupe vacciné par les bivalents en termes de performances de croissance. Les performances de croissance ont été significativement améliorées pendant la période d'engraissement (70 à 175 jours d'âge) dans le groupe vacciné bivalent mélangeable par rapport au groupe vacciné bivalent prêt à l'emploi sur une ferme. Le groupe vacciné par trivalent a suscité des niveaux plus élevés d'anticorps neutralisants et de cellules sécrétant de l'interféron-γ (IFN-γ-SC) contre le PCV-2d, tout en diminuant simultanément les niveaux de charge de PCV-2d dans le sang par rapport aux vaccins mélangeables et prêts à l'emploi. Le groupe vacciné trivalent a également provoqué des niveaux plus élevés d'IFN-γ-SC contre M. hyopneumoniae et des niveaux inférieurs de charge de M. hyopneumoniae dans le larynx par rapport aux groupes vaccinés bivalents mélangeables et prêts à l'emploi. Les résultats de la présente étude ont démontré qu'un vaccin trivalent contenant du PCV-2a/b et M. hyopneumoniae entraînait un paramètre plus productif, des réponses immunitaires plus élevées et moins de charges sanguines virales et mycoplasmiques dans le larynx par rapport aux vaccins mélangeables et prêts à l'emploi malgré la présence d'une infection subclinique par le PCV-2d et d'une pneumonie enzootique dans les élevages.(Traduit par Docteur Serge Messier).

Multiplex polymerase chain reaction for the detection and differentiation of 4 porcine circovirus 2 genotypes (PCV-2a, -2b, -2d, and -2e) in clinical samples.

The objective of this study was to develop multiplex polymerase chain reaction (PCR) for the simultaneous detection of porcine circovirus 2 (PCV-2) and differentiation among 4 PCV-2 genotypes (2a, 2b, 2d, and 2e) in collected clinical lymph node samples. The multiplex PCR detected each of 4 PCV-2 genotypes (2a, 2b, 2d, and 2e) to a dilution of 2 × 101 copies/µL. PCV-2a, PCV-2b, PCV-2d, and PCV-2e were propagated in tissues prior to DNA extraction for use in multiplex PCR for the simultaneous detection and differentiation of 4 PCV-2 genotypes. The designed multiplex PCR effectively detected and differentiated various combinations of multiple infection, such as PCV-2a+2b, PCV-2a+2d, PCV-2b+2d, PCV-2a+2e, and PCV-2a+2b+2d, in clinical lymph node samples. The results of this study demonstrated that multiplex PCR testing of clinical samples developed herein was able to simultaneously detect and differentiate among the 4 PCV-2 genotypes (PCV-2a, 2b, 2d, and 2e).

L'objectif de cette étude était de développer une réaction en chaîne par la polymérase multiplex (PCR) pour la détection simultanée du circovirus porcin 2 (PCV-2) et la différenciation entre quatre génotypes PCV-2 (2a, 2b, 2d et 2e) dans des échantillons cliniques de noeuds lymphatique. La PCR multiplex a détecté chacun des quatre génotypes PCV-2 (2a, 2b, 2d et 2e) à une dilution de 2 × 101 copies/µL. Le PCV-2a, le PCV-2b, le PCV-2d et le PCV-2e ont été propagés dans les tissus avant l'extraction de l'ADN pour être utilisés dans la PCR multiplex pour la détection et la différenciation simultanées de quatre génotypes du PCV-2. La PCR multiplex conçue a efficacement détecté et différencié diverses combinaisons d'infections multiples, telles que PCV-2a+2b, PCV-2a+2d, PCV-2b+2d, PCV-2a+2e et PCV-2a+2b+2d, dans les échantillons cliniques de ganglions lymphatiques. Les résultats de cette étude ont démontré que le test PCR multiplex des échantillons cliniques développés ici était capable de détecter et de différencier simultanément les quatre génotypes PCV-2 (PCV-2a, 2b, 2d et 2e).(Traduit par Docteur Serge Messier).

A field efficacy trial of a trivalent vaccine containing porcine circovirus type 2a and 2b, and Mycoplasma hyopneumoniae in three herds.

BACKGROUND: This field trial was designed to evaluate the efficacy of a new trivalent vaccine containing porcine circovirus type 2a and 2b (PCV2a/b), and Mycoplasma hyopneumoniae at three independent locations. METHODS: Three farms were selected based on their history of PCV2 and M. hyopneumoniae co-infection. Each farm housed a total of 60, 3-day-old pigs that were randomly allocated to one of three treatment groups. Pigs were administered the trivalent vaccine intramuscularly with either a 1.0 ml dose at 3 and 24 days of age or a 2.0 ml dose at 21 days of age in accordance with the manufacturer's recommendations. RESULTS: Clinically, the average daily weight gain of the one-dose and two-dose vaccinated groups within all three farms was significantly higher (p < 0.05) than those of unvaccinated animals during the growing (70-112 days of age), finishing (112-175 days of age) and overall (3-175 days of age) stages of production. One-dose and two-dose vaccinated animals elicited neutralizing antibodies and interferon-γ-secreting cells (IFN-γ-SC), which reduced the amount of PCV2 in terms of blood load and reduced the severity of lymphoid lesions when compared with unvaccinated animals. Similarly, one-dose and two-dose vaccinated animals elicited IFN-γ-SC, which reduced the amount of M. hyopneumoniae in terms of laryngeal load and reduced the severity of lung lesions. CONCLUSIONS: The intramuscular administration of either one or two doses of trivalent vaccine was not significantly different in any of the evaluated parameters. The results of field trial demonstrated that the trivalent vaccine was efficacious in the protection of swine herds where PCV2d and M. hyopneumoniae were in active circulation.

Pathogenicity of Porcine Circovirus Type 2d (PCV2d) in Pigs Infected with PCV2d or Co-infected with Mycoplasma hyopneumoniae and PCV2d or with Porcine Reproductive and Respiratory Syndrome Virus and PCV2d.

The objective of this study was to determine the pathogenicity of porcine circovirus type 2d (PCV2d) in pigs inoculated intranasally with PCV2d alone, PCV2d in combination with Mycoplasma hyopneumoniae or PCV2d in combination with porcine reproductive and respiratory syndrome virus (PRRSV). Pigs infected with PCV2d alone were asymptomatic. All pigs inoculated with either M. hyopneumoniae and PCV2d or with PCV2d and PRRSV developed porcine circovirus-associated disease (PCVAD), as characterized by a sudden onset of clinical signs and disseminated granulomatous inflammation. Inflammation was mainly present in lymph nodes and spleen, and occasionally in liver and kidney. Pigs in both of these dually infected groups also had significantly higher (P <0.05) microscopic lymphoid lesion scores and a significantly higher (P <0.05) number of PCV2-positive cells in lymph node tissue than did pigs inoculated with PCV2d alone. The M. hyopneumoniae and PRRSV combination potentiated the PCV2d load in the blood. Co-infection with PRRSV and PCV2d resulted in a significantly higher blood load of PCV2d compared with the M. hyopneumoniae and PCV2d combination. Successful reproduction of PCVAD in pigs appears to require PCV2d with at least one additional infectious agent, such as M. hyopneumoniae or PRRSV, for the full manifestation of disease.

A Comparison of Pathogenicity and Virulence of Three Porcine Circovirus Type 2 (PCV2) Genotypes (a, b, and d) in Pigs Singularly Inoculated with PCV2 and Dually Inoculated with Mycoplasma hyopneumoniae and PCV2.

The objective of this study was to compare the virulence of three different porcine circovirus type 2 (PCV2) genotypes (PCV2a, PCV2b, and PCV2d) in pigs infected with either one of these three PCV2 genotypes versus pigs dually inoculated with Mycoplasma hyopneumoniae and PCV2. Pigs were inoculated intratracheally with M. hyopneumoniae at 4 weeks of age followed by another intranasal inoculation at 6 weeks of age with one of three PCV2 genotypes. Dual infection with two pathogens produced moderate and severe dyspnea, lethargy, and reduced weight gain in pigs regardless of the PCV2 genotype evaluated compared with pigs only inoculated with PCV2. The overall levels of PCV2d viremia and severity of lymphoid lesions, and PCV2-antigen within lymphoid lesions were significantly higher in pigs dually inoculated with M. hyopneumoniae/PCV2d when compared with all other dually inoculated groups. The level of PCV2 viremia and the production of PCV2-associated lymphoid lesions did not differ significantly among PCV2a, PCV2b, and PCV2d single-inoculated pig groups. The results of this study demonstrated that M. hyopneumoniae potentiated the replication of PCV2d more than it did with the other PCV2 genotypes as measured by lymphoid lesion severity.

Experimental efficacy of a trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae against PCV2d and M. hyopneumoniae challenges.

The purpose of this experimental study was to evaluate the efficacy of a new trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae. Pigs were administered the vaccine intramuscularly as either at 3 and 24 days of age with 1.0 mL or at 21 days of age with 2.0 mL according to the manufacturer's recommendations. The pigs were challenged at 42 days of age with either PCV2d (intranasal route) or M. hyopneumoniae (intratracheal route), or both. No statistical differences were observed between the one-dose and two-dose experiments based on clinical (growth performance), immunological (protective immunity), microbiological (viremia and laryngeal swab), and pathological (pulmonary and lymphoid lesion) outcomes. Pigs in vaccinated/challenged and unvaccinated/unchallenged groups showed significant difference in growth performance compared to pigs in the unvaccinated/challenged group in both dosage experiments. Vaccinated pigs elicited a significant amount of protective immunity for PCV2d-specific neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC) as well as M. hyopneumoniae-specific IFN-γ-SC significantly post-challenge compared to unvaccinated/challenged pigs. Vaccination and challenge reduced the viral load amount of PCV2d in the blood and reduced the M. hyopneumoniae load in laryngeal swab, while simultaneously reducing both pulmonary and lymphoid lesion severity when compared to unvaccinated/challenged pigs. Trivalent vaccination provided good protection against a single PCV2d challenge, single M. hyopneumoniae challenge, and a PCV2d/M. hyopneumoniae dual challenge.

Efficacy Evaluation of a Bivalent Vaccine Containing Porcine Circovirus Type 2b and Mycoplasma hyopneumoniae Against an Experimental Dual Challenge.

The purpose of this study was to evaluate the efficacy of a new, single-dose bivalent vaccine containing porcine circovirus type 2b (PCV2b) and Mycoplasma hyopneumoniae against a dual PCV2b and M. hyopneumoniae challenge. At -25 days post challenge (dpc, 10 days of age), one pig group (designated as the vaccinated/challenged group) received a single, 1.0 ml dose of bivalent vaccine. Pigs in both the vaccinated/challenged and unvaccinated/challenged groups were then inoculated intranasally with PCV2b and M. hyopneumoniae at 0 dpc (35 days of age). Pigs in vaccinated/challenged group induced significantly higher levels of neutralizing antibodies against PCV2b and cell-mediated immunity against PCV2b and M. hyopneumonia when compared with pigs in unvaccinated/challenged group. The vaccination of pigs with a bivalent vaccine also reduced PCV2b viremia, reduced mycoplasmal nasal shedding, and decreased the severity of both lung and lymphoid lesions for PCV2b and M. hyopneumoniae infection, respectively. The results of this study demonstrated that the evaluated bivalent vaccine was effective in protecting pigs against PCV2b and M. hyopneumoniae infection.

Experimental reproduction of porcine respiratory disease complex in pigs inoculated porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae and followed by inoculation with porcine circovirus type 2.

The aim of this study was to reproduce severe pneumonic lesions, similar to those during naturally-occurring porcine respiratory disease complex, in pigs dually inoculated with porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae at 6 weeks of age, followed by inoculation with porcine circovirus type 2 at two weeks after. Time and sequence of infection with three pathogens mirror Asian field conditions. Microscopically, interstitial pneumonia and peribronchiolar lymphoid hyperplasia are considered the most characteristic lung lesions in infected pigs. The results of the present study demonstrate that inoculation of pigs with these three pathogens can lead to severe interstitial pneumonia with peribronchial or peribronchiolar lymphoid hyperplasia and fibrosis.

Field evaluation of a sing-dose bivalent vaccine of porcine circovirus type 2b and Mycoplasma hyopneumoniae.

BACKGROUND: The field efficacy of a bivalent vaccine containing porcine circovirus type 2b (PCV2b) and Mycoplasma hyopneumoniae was evaluated on three pig farms. METHODS: Three pig farms were used, two of which had a history of subclinical PCV2 and clinical M. hyopneumoniae infections between 84 and 126 days of age while concurrent porcine circovirus-associated disease and clinical M. hyopneumoniae infection between 70 and 105 days of age. Each farm vaccinated pigs with a single dose of a bivalent vaccine at 10 days of age while unvaccinated pigs were administered a single dose of phosphate buffered-saline at the same age. RESULTS: Vaccination improved growth performance and reduced clinical scores significantly (p < .05) when compared with unvaccinated animals. The amount of PCV2d loads in blood and M. hyopneumoniae loads in nasal swabs of vaccinated animals were also significantly lower (p < .05) when compared with unvaccinated animals. Immunologically, vaccinated groups elicited a significantly higher (p < .05) level of protective immunity against PCV2d such as neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC), as well as protective immunity against M. hyopneumoniae such as IFN-γ-SC when compared with unvaccinated animals. Pathologically, vaccination significantly lowered (p < .05) the scores of M. hyopneumoniae-induced pneumonia and PCV2-associated lymphoid lesions when compared with unvaccinated animals. CONCLUSIONS: The evaluated bivalent vaccine provided good protection against PCV2d and M. hyopneumoniae infection under field conditions.

The prevalence of porcine circovirus type 2e (PCV2e) in Korean slaughter pig lymph nodes when compared with other PCV2 genotypes.

The objective of this study was to determine the prevalence of porcine circovirus type 2e (PCV2e) over other PCV2 genotypes (a, b, c and d) from the lymph nodes of 1,550 randomly selected slaughter pigs. Samples were obtained at a rate of five samples per farm from 310 farms between January 2018 and May 2020. Of the 1,550 lymph node samples, PCV2 DNA was detected in 762 (49.20%) samples. Among the 762 PCV2 DNA-positive samples, a single PCV2 genotype was detected in 744 samples, while multiple PCV2 genotypes were only detected in 18 samples. Of the 744 single infection cases, PCV2d was the most prevalent with 709 cases, followed by PCV2b (15 cases), PCV2a (14 cases) and PCV2e (6 cases). Of the 18 multiple infection cases, PCV2a+PCV2d was the most prevalent (7 cases) followed by PCV2b+PCV2d (3 cases), PCV2b+PCV2e (3 cases), PCV2a+PCV2b+PCV2d (3 cases) and PCV2a+PCV2b (2 cases). No PCV2c was detected in any of the single or multiple infection cases. The results of prevalence identified PCV2d as the current dominant genotype, while the newly emerging PCV2e maintained the lowest prevalence among the evaluated swine farms.

The first isolation of porcine circovirus type 2e from a Korean pig.

This study describes the first isolation and genetic characterization of the newly emerging porcine circovirus type 2e (PCV2e) from Korean pigs. The PCV2e isolate did not produce a cytopathic effect in PCV-free PK-15 cells; therefore, PCV2e infection was demonstrated by immunohistochemistry with polyclonal PCV2a antibodies and polymerase chain reaction with primers specific for PCV2e. As the infected PCV-free PK-15 cells were passaged, the amount of infectious virus correlated with an increase in the amount of viral DNA (i.e., a decrease in the cycle threshold values. A full genomic analysis of the PCV2e strain SNUVR199711 was performed and showed that the genome is 1,777 nucleotides in length.

A Dual Swine Challenge With Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae Used to Compare a Combination of Mixable Monovalent PCV2 and Monovalent M. hyopneumoniae Vaccines With a Ready-to Use PCV2 and M. hyopneumoniae Bivalent Vaccine.

The present study evaluated the efficacy of swine vacciation using a combination of mixable monovalents for porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae against a ready-to-use bivalent vaccine under experimental conditions. Pigs at 21 days of age were administered either a combination of two mixable monovalent vaccines or a bivalent vaccine containing PCV2 and M. hyopneumoniae. Vaccination was followed with an M. hyopneumoniae challenge at 42 days of age (-14 days post challenge, dpc) and a PCV2d challenge at 56 days of age (0 dpc). Each vaccinated and challenged group was compared with the unvaccinated and challenged group for clinical, microbiological, immunologic, and pathologic differences. Clinically, two vaccinated and challenged groups showed minimal respiratory diseases that was characterized by occasionally coughing and sneezing. A significant difference was not calculated in the average daily weight gain, nasal shedding of M. hyopneumoniae, and pathological lesions between two vaccinated and challenged groups. A combination of two monovalent vaccines mixed into a combo prior to vaccination followed by challenge resulted in increased numbers of PCV2d-specific interferon-γ secreting cells at 21 dpc and a significant reduction in PCV2d viremia at 14 dpc when compared with the ready-to-use bivalent-vaccinated and challenged groups. These results offer supporting evidence that vaccination during the weaning to finishing period against M. hyopneumoniae and PCV2 is efficacious for controlling diseases caused by these two pathogens.

A modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine protects late-term pregnancy gilts against a heterologous PRRSV-2 challenge.

The objective of this study was to evaluate the efficacy of a modified-live virus (MLV) porcine reproductive and respiratory syndrome virus (PRRSV) vaccine against a heterologous PRRSV-2 challenge in late-term pregnancy gilts under experimental conditions. Eighteen gilts were randomly assigned to vaccinated-challenged, unvaccinated-challenged, and unvaccinated-unchallenged groups (n = 6 gilts per group). Pregnant gilts in the vaccinated-challenged and unvaccinated-unchallenged groups were able to carry their pregnancies to full term and farrowed after 114 to 115 days of gestation. In contrast, pregnant gilts in the unvaccinated-challenged group did not reach full term and farrowed early, after 104 to 108 days of gestation. Pregnant gilts vaccinated with the PRRSV-2 MLV vaccine exhibited a reduction in PRRSV-2 viremia. At the time of challenge with PRRSV-2, vaccinated gilts had relatively low levels of neutralizing antibody titers (≤ 1:16 titer), whereas the number of interferon-γ-secreting cells (IFN-γ-SC) was consistently at protective levels (IFN-γ-SC, ≥ 150 per million). Induction of cell-mediated immunity, as measured by PRRSV-2-specific IFN-γ-SC, correlated with a reduction in PRRSV-2 viremia. Duration of immunity was a minimum of 19 wk. Taken together, the results presented here suggest that vaccination of gilts with a PRRSV-2 MLV vaccine can protect against a heterologous PRRSV-2 challenge and improve the reproductive performance of late-term pregnancy gilts.

L'objectif de la présente étude était d'évaluer dans des conditions expérimentales l'efficacité d'un vaccin à virus vivant modifié (MLV) du virus du syndrome reproducteur et respiratoire porcin (PRRSV) contre une infection défi avec un PRRSV-2 hétérologue chez des cochettes en fin de gestation. Dix-huit cochettes furent assignées de manière aléatoire à un des groupes suivants: vaccinées-infectées, non-vaccinées-infectées et non-vaccinées-non-infectées (n = 6 cochettes par groupe). Les cochettes gestantes dans les groupes vaccinées-infectées et non-vaccinées-non-infectées furent en mesure de mener leur gestation à terme et ont mis-bas après 114 à 115 jours de gestation. À l'opposé, les cochettes gestantes du groupe (témoin) non-vaccinées-infectées ne se sont pas rendues à terme et ont mis-bas plus tôt, après 104 à 108 jours de gestation. Les cochettes gestantes vaccinées avec le vaccin PRRSV-2 MLV ont montré une réduction de la virémie à PRRSV-2. Au moment de l'infection-défi avec le PRRSV-2, les cochettes vaccinées avaient des titres relativement bas d'anticorps neutralisants (titre ≤ 1:16), alors que le nombre de cellules secrétant de l'interféron-γ (IFN-γ-SC) était constamment à des niveaux de protection (IFN-γ-SC, ≥ 150 par million). L'induction de l'immunité à médiation cellulaire, telle que mesurée par l'IFN-γ-SC spécifique à PRRSV-2, corrélait avec une réduction de la virémie à PRRSV-2. La durée de l'immunité était d'un minimum de 19 sem. Pris dans son ensemble, les résultats présentés ici suggèrent que la vaccination des cochettes avec un vaccin PRRSV-2 MLV peut protéger contre une infection-défi avec un PRRSV-2 hétérologue et améliorer les performances de reproduction des cochettes en fin de gestation.(Traduit par Docteur Serge Messier).

Comparative study of the virulence of 3 major Korean porcine circovirus type 2 genotypes (a, b, and d).

The objective of this study was to compare the virulence of 3 major Korean porcine circovirus type 2 (PCV2) genotypes in terms of clinical signs, PCV2 viremia and antibody titers, lymphoid lesions, and PCV2-antigen within lymphoid lesions in experimentally infected pigs. Pigs were infected at 7 weeks with PCV2a, PCV2b, and PCV2d strains and necropsied at 28 days post-infection. No statistical differences were observed in clinical signs, PCV2 viremia and antibody titers, lymphoid lesions scores, and numbers of PCV2 antigens among the 3 major Korean PCV2 genotypes. The results of this study indicate that the 3 major Korean PCV2 genotypes, PCV2a, PCV2b, and PCV2d, have similar virulence.

L'objectif de la présente étude était de comparer la virulence de trois génotypes majeurs de circovirus porcine de type 2 (PCV2) coréens en termes de signes cliniques, virémie de PCV2 et titres d'anticorps, lésions lymphoïdes et antigènes de PCV2 à l'intérieur des lésions lymphoïdes chez des porcs infectés expérimentalement. Les porcs furent infectés à 7 semaines d'âge avec les souches PCV2a, PCV2b et PCV2d et soumis à une nécropsie 28 jours post-infection. Aucune différence significative ne fut observée dans les signes cliniques, la virémie de PCV2 et les titres d'anticorps, les pointages de lésions lymphoïdes et les nombres d'antigènes de PCV2 pour les trois génotypes majeurs de PCV2 coréens. Les résultats de cette étude indiquent que les trois génotypes majeurs de PCV2 coréens, PCV2a, PCV2b et PCV2d ont une virulence similaire.(Traduit par Docteur Serge Messier).

A comparison of two commercially available porcine reproductive and respiratory syndrome virus (PRRSV) modified-live virus vaccines analyzing the growth performance in 1-day-old vaccinated swine located on endemic farms co-circulating PRRSV-1 and PRRSV-2.

The objective of this study was to compare the efficacy of a porcine reproductive and respiratory syndrome virus (PRRSV)-1 and PRRSV-2 modified-live virus (MLV) vaccines when administered at 1 day of age under field conditions. The piglets elicited anti-PRRSV antibodies at 1 day of age even in the presence of maternally derived antibodies. The number of PRRSV-2 genomic copies in the sera of pigs from the PRRSV-2 MLV-vaccinated pigs was significantly (P<0.05) lower when compared to PRRSV-1 MLV-vaccinated pigs. The average daily gain in PRRSV-2 MLV-vaccinated pigs was significantly (P<0.05) higher when compared to both PRRSV-1 MLV-vaccinated and unvaccinated pigs. This study demonstrated that vaccination as early as 1 day of age was effective against PRRSV infection.

Evaluation of the efficacy of a trivalent vaccine mixture against a triple challenge with Mycoplasma hyopneumoniae, PCV2, and PRRSV and the efficacy comparison of the respective monovalent vaccines against a single challenge.

BACKGROUND: The objective of this study was to assess the efficacy of a trivalent vaccine mixture and compare it to the respective monovalent vaccines against Mycoplasma hyopneumoniae, porcine circovirus type 2 (PCV2), and porcine reproductive and respiratory syndrome virus (PRRSV). RESULTS: Pigs that were triple challenged with M. hyopneumoniae, PCV2, and PRRSV following vaccination with the trivalent vaccine mixture exhibited a significantly better growth performance when compared to unvaccinated and challenged pigs. A statistical difference was not found when comparing pig populations which were vaccinated with the trivalent vaccine followed by a triple challenge and pigs vaccinated with monovalent M hyopneumoniae vaccine followed by mycoplasmal single challenge in the following areas: M. hyopneumoniae nasal shedding, the number of M. hyopneumoniae-specific interferon-γ secreting cells (IFN-γ-SC), and mycoplasmal lung lesion scores. Pigs vaccinated with the trivalent vaccine mixture followed by a triple challenge resulted in a similar reduction of PCV2 viremia, an increase in the number of PCV2-specific IFN-γ-SC and reduction in interstitial lung lesion scores when compared to pigs vaccinated with a PCV-2 vaccine and challenged with PCV2 only. Lastly, there was a significant difference in the reduction of PRRSV viremia, an increase in PRRSV-specific IFN-γ-SC and a reduction of interstitial lung lesion scores between pigs vaccinated with the trivalent vaccine mixture followed by a triple challenge and pigs vaccinated with a monovalent PRRSV vaccine followed by PRRSV challenge only. CONCLUSION: The trivalent vaccine mixture was efficacious against a triple challenge of M. hyopneumoniae, PCV2, and PRRSV. The trivalent vaccine mixture, however, did not result in equal protection when compared against each respective monovalent vaccine, with the largest vaccine occurring within PRRSV.

Effectiveness of a commercial porcine reproductive and respiratory syndrome virus (PRRSV) subunit vaccine against heterologous PRRSV-1 and PRRSV-2 challenge in late-term pregnant gilts.

The objective of the present study was to evaluate the efficacy of a commercial porcine reproductive and respiratory syndrome virus (PRRSV) subunit vaccine against heterologous PRRSV-1 and PRRSV-2 challenge in late-term pregnant gilts. Gilts were vaccinated intramuscularly 56 and 35 days antepartum (on days 58 and 79 of gestation) and challenged intranasally 21 days antepartum (on day 93 of gestation) with PRRSV-1 or PRRSV-2. Regardless of the challenge strain's genotype, the vaccinated gilts carried their pregnancies to term and farrowed between days 114 and 115 of gestation. All the unvaccinated gilts aborted, between days 105 and 110 of gestation. The vaccinated gilts had a significantly lower level (P < 0.05) of PRRSV viremia and significantly higher levels (P < 0.05) of virus-neutralizing antibodies and interferon-γ-secreting cells compared with the unvaccinated gilts. The mean number of PRRSV-positive cells per area of fetal tissue examined did not differ significantly between the litters from the vaccinated and unvaccinated gilts. The data presented here indicate that vaccination in late-term pregnancy with PRRSV subunit vaccine is efficacious against reproductive failure due to heterologous PRRSV-1 and PRRSV-2 infection.

L'objectif de la présente étude était d'évaluer l'efficacité d'un vaccin sous-unitaire commercial contre le virus du syndrome reproducteur et respiratoire porcin (VSRRP) lors d'une infection défi avec des souches de VSRRP-1 et VSRRP-2 hétérologues chez des cochettes en fin de gestation. Les cochettes furent vaccinées par voie intramusculaire 56 et 35 jours ante-partum (aux jours 58 et 79 de la gestation) et infectées par voie intra-nasale 21 jours ante-partum (jour 93 de la gestation) avec VSRRP-1 ou VSRRP-2. Sans égard au génotype de la souche utilisée pour l'infection défi, les cochettes vaccinées ont mené leur gestation à terme et ont mis-bas entre les jours 114 et 115 de la gestation. Toutes les cochettes non-vaccinées ont avorté, entre les jours 105 et 110 de gestation. Les cochettes vaccinées avaient un niveau significativement plus faible (P < 0,05) de virémie à VSRRP et des niveaux significativement plus élevés (P < 0,05) d'anticorps viraux neutralisants et de cellules secrétant de l'interféron-γ comparativement aux cochettes non-vaccinées. Le nombre moyen de cellules positives pour VSRRP par surface de tissu foetal examiné ne différait pas significativement entre les portées des cochettes vaccinées et non-vaccinées. Les résultats présentés ici indiquent que la vaccination en fin de gestation avec un vaccin sous-unitaire anti-VSRRP est efficace contre les problèmes reproducteurs causés par une infection par des souches hétérologues de VSRRP-1 et VSRRP-2.(Traduit par Docteur Serge Messier).

A comparative study of the efficacy of a porcine reproductive and respiratory syndrome subunit and a modified-live virus vaccine against respiratory diseases in endemic farms.

The efficacy of a porcine reproductive and respiratory syndrome (PRRS) subunit vaccine was evaluated and compared with a modified-live virus (MLV) vaccine under field conditions. Three farms were selected based on their history of respiratory diseases caused by co-infection with both PRRSV-1 and PRRSV-2. In each farm, 60 pigs were randomly allocated to 2 vaccinated and 1 unvaccinated groups (20 pigs per group). One group of pigs were administered the PRRS subunit vaccine at 21 and 42 days of age and another group administered the PRRS MLV vaccine at 21 days of age. The subunit vaccine had similar efficacy and, in some instances, performed even better than the MLV vaccine. Vaccination of pigs with either of the PRRS vaccines resulted in significantly improved growth performance in Farm B but not in Farm C. In Farm A, pigs vaccinated with the PRRS subunit vaccine had a better growth performance statistically compared to those vaccinated with the PRRS MLV vaccine. At the peak of PRRSV-1 and PRRSV-2 viremia, neutralizing antibodies and T-cell responses against PRRSV-1 and PRRSV-2 were at low levels suggesting that either vaccine is only able to provide a partial protection against co-circulating PRRSV-1 and PRRSV-2.

L'efficacité d'un vaccin sous-unitaire contre le syndrome reproducteur et respiratoire porcin (SRRP) a été évaluée et comparée à un vaccin vivant modifié (VVM) dans des conditions de terrain. Trois fermes furent sélectionnées sur la base de leur historique de maladies respiratoires causées par co-infection par VSSRP-1 et VSRRP-2. Sur chaque ferme, 60 porcs furent répartis de manière aléatoire à deux groupes vaccinés et un groupe non-vacciné (20 porcs par groupe). Un groupe de porcs a reçu le vaccin SRRP sous-unitaire à 21 et 42 j d'âge et un autre groupe a reçu le VVM SRRP à 21 j d'âge. Le vaccin sous-unitaire avait une efficacité similaire, et en certaines occasions, performait mieux que le VVM. La vaccination des porcs avec un ou l'autre des vaccins SRRP, a résulté en une amélioration significative des performances de croissance pour la Ferme B mais pas pour la Ferme C. Sur la Ferme A, les porcs vaccinés avec le vaccin sous-unitaire SRRP présentaient de meilleures performances de croissance comparativement à ceux vaccinés avec le VVM du SRRP. Au pic de la virémie de VSRRP-1 et VSRRP-2, les réponses en anticorps neutralisants et en cellules T contre VSRRP-1 et VSRRP-2 étaient faibles ce qui suggère que les deux vaccins ne sont en mesure que de fournir une protection partielle contre une co-infection par VSRRP-1 et VSRRP-2.(Traduit par Docteur Serge Messier).

Evaluation of a porcine circovirus type 2a (PCV2a) vaccine efficacy against experimental PCV2a, PCV2b, and PCV2d challenge.

The objective of this study was to compare the efficacy of a commercial porcine circovirus type 2a (PCV2a) subunit vaccine against experimental PCV2a, PCV2b, and PCV2d challenge. A total of 105 pigs were randomly divided into 7 groups (15 pigs per group). At 21 days old the pigs were intramuscularly administered the PCV2a vaccine as a 1.0 mL dose. Four weeks following vaccination, pigs were challenged with either Korean PCV2a, PCV2b, or PCV2d. All vaccinated pigs showed a significant (P < 0.05) reduction of clinical signs, PCV2 viremia, lymphoid lesions, and lymphoid PCV2 antigen levels compared to unvaccinated control pigs. Vaccination resulted also in significantly higher (P < 0.05) titers of neutralizing antibody against PCV2, and an increase in the frequency of PCV2-specific interferon-γ secreting cells (IFN-γ-SC). The vaccine showed similar protection among the vaccinated groups regardless of the genotype of the challenge. Interestingly, vaccinated pigs had higher levels of neutralizing antibody titers against PCV2a compared to PCV2b or PCV2d while the number of PCV2a-, PCV2b-, and PCV2d-specific IFN-γ-SC were similar. Taken together, the results presented here demonstrate that a PCV2a vaccine can be effective against experimental PCV2a, PCV2b, and PCV2d challenge.