Developing a vaccine that can differentiate infected and vaccinated animals (DIVA) is a new challenge in the design of a vaccine for porcine reproductive and respiratory syndrome virus (PRRSV). Nonstructural protein 2 (nsp2) is the single largest viral product, and it has multiple roles in polypeptide processing and replication complex formation. Using reverse genetics and an infectious PRRSV cDNA clone, we constructed several deletion mutants in the non-essential region of nsp2. One mutant, which has a 131 amino acid deletion within a relatively conserved region of nsp2, was recovered and found to produce a viable virus. The deleted region was replaced with a peptide tag encoding eight amino acids. A recombinant virus containing the 131 amino acid deletion was found to produce normal virus yields in MARC-145 cells and porcine alveolar macrophages (PAM); however, gross and micro-histopathology showed that the virus was less virulent in pigs. The 131 amino acid peptide was expressed as a recombinant protein and used to coat enzyme-linked immunosorbent assay (ELISA) plates. This peptide was recognized by sera from pigs infected with wild-type virus, but not by sera from pigs infected with the deletion mutant. The results from this study show that nsp2 is an important target for the development of marker vaccines and for virus attenuation.

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1 dose of a BVDV1a and 2a MLV vaccine administered SC or IM prior to breeding helped protect against fetal infection in pregnant heifers exposed to cattle PI with BVDV1b.

BackgroundThe development of the innate and adaptive immune responses to Porcine reproductive and respiratory syndrome virus (PRRSV) after vaccination of 1 day-old pigs with a PRRSV-1 based modified live virus (MLV) vaccine by intramuscular (IM) and intranasal (IN) routes was characterised, before and after challenge with a heterologous PRRSV-1 isolate at 18 weeks post-vaccination. Twenty-five PRRSV-seronegative piglets were used. At 1 day of age, pigs were administered with a single dose of vaccine via the IM (n = 10) or the IN route (n = 10). Control group (n = 5) received saline solution. After vaccination, pigs were bled at days 3, 7, 28, 56, 83, 113 and 125. Levels of cytokines IL-10, IL-8, IFN-α (measured by ELISA tests of serum), TNF-α and IFN-γ (measured by ELISA and ELISPOT, respectively, from stimulated peripheral blood mononuclear cells), and serum neutralising antibodies (NA) to the vaccine strain, were measured.ResultsThe induction of IL-10 was rare, indicating that IL-10 mediated immunomodulation/immune dysfunction was not a feature of this vaccine or of the challenge virus. IL-8 was detected in only two pigs following vaccination, but in the majority of pigs after challenge, indicating that their ability to produce an innate immune response was not impaired. TNF-α was not detected in any vaccinated pigs until day 83. After challenge, only a minority of pigs produced TNF-α. IFN-α was detected in all vaccinated pigs following vaccination, indicating the potential for development of an effective Th1 adaptive immune response. IFN-γ-secreting cells were detected in all vaccinated pigs after vaccination. NA to the vaccine strain were first detected at day 56 in pigs vaccinated by both routes, and remained at similar levels until challenge. After challenge, a boost in NA was observed. The efficacy of the vaccine was demonstrated by reduction of viraemia and nasal shedding after challenge.ConclusionsThe administration of a PRRSV-1 based MLV vaccine to 1 day-old piglets was able to induce an immune response characterised by: (1) undetectable or low levels of IL-10, IL-8 and TNF-α, (2) an increase in IFN-α expression within the first seven days, (3) a gradual increase in the number of antigen-specific IFN-γ-secreting cells, and (4) induction of detectable NA. After challenge with a heterologous strain, there was a rapid boost in NA titres, indicating a priming effect of the vaccine.

BackgroundThe objective of the study was to evaluate the influence of maternally derived antibodies (MDA) on the efficacy of a PRRSV-1 based attenuated vaccine, when administered in 1 day-old piglets by the intramuscular route. The protective immunity of the modified live virus vaccine was evaluated in pigs born from seropositive sows, vaccinated at 1 day of age, upon inoculation with a PRRSV-1 isolate. The animals were challenged when the levels of MDAs detected by seroneutralization test (SNT) in the non-vaccinated control group became undetectable (10 weeks after vaccination).ResultsA protective effect of vaccination was observed since a significant reduction of viral load in serum compared to the control group was detected in all sampling days after challenge; efficacy was supported by the significant reduction of nasal and oral shedding as well as in rectal temperatures. Clinical signs were not expected after the inoculation of a PRRSV-1 subtype 1 challenge strain. However, the challenge virus was able to develop fever in 61% of the control pigs. Vaccination had a positive impact on rectal temperatures since the percentage of pigs that had fever at least once after challenge was reduced to 31% in vaccinated animals, and control pigs had significantly higher rectal temperatures than vaccinated pigs 3 days post-challenge. The lack of a vaccination effect in body weight gain was probably due to the short evaluation period after challenge (10 days). In the vaccinated group, 9/16 pigs (56%) experienced an increase in ELISA S/P ratio from the day of vaccination to 67 days post-vaccination. All vaccinated pigs were seropositive before challenge, indicating the development of an antibody response following vaccination even in the face of MDAs. In contrast to ELISA results, only 2/16 vaccinated pigs developed neutralizing antibodies detectable by a SNT that used a subtype 1 MA-104 adapted strain. Even in the absence of SN antibodies, vaccinated pigs were protected from challenge with a heterologous strain. The role of cell-mediated immunity should be considered, if protection was not mediated by SN antibodies only.ConclusionsThe efficacy of the attenuated PRRSV-1 vaccine in 1-day-old pigs seropositive to PRRSV prior to a PRRSV-1 challenge was demonstrated by improvement of clinical, virological and immunological variables. With the current experimental design, maternal immunity did not interfere with the development of a protective immune response against a PRRSV-1 challenge, after vaccination of 1 day-old pigs. Confirmation of these results under field conditions will be needed.

bEnzootic pneumonia, resulting from infection with Mycoplasma hyopneumoniae, is of considerable economic importance to the pig industry and normally is controlled through active vaccination of piglets. We have demonstrated that administration of an inactivated Mycoplasma hyopneumoniae vaccine to piglets less than 1 week old is efficacious under field conditions and reduces the level of lung lesions observed in comparison to that in control pigs. Here, the results of two separate studies, one in piglets with and the second one in piglets without maternal antibodies, conducted to satisfy the requirements of the European Pharmacopoeia (monograph no. 07/2009:2448), are reported. Piglets received either minimal titer Suvaxyn MH-One or saline at less than 1 week of age and were challenged with Mycoplasma hyopneumoniae 2 weeks later. The number of lung lesions was recorded 4 weeks after challenge, and bronchial swab and lung tissue specimens were analyzed for quantification of Mycoplasma hyopneumoniae DNA. In the presence and absence of maternal antibodies, vaccination of piglets at less than 1 week of age was efficacious, with vaccinated piglets having significantly lower percentages of lung with lesions and lower Mycoplasma hyopneumoniae counts detected in bronchial swab and lung tissue specimens at necropsy. In conclusion, the vaccination of piglets at 1 week of age with Suvaxyn MH-One is efficacious in the presence of high levels of maternal antibodies. E nzootic pneumonia in pigs is a serious problem for commercial operations. The disease can result from infection with Mycoplasma hyopneumoniae, is characterized mainly by a nonproductive cough (1), and is responsible for considerable economic losses in pig production worldwide (2, 3), resulting from higher feed conversion, decreased body weight gains, and increased medication costs. Studies have shown that infection with M. hyopneumoniae also predisposes pigs to subsequent infection by other bacterial pathogens, such as Actinobacillus (formerly Haemophilus) pleuropneumoniae (4), or Pasteurella multocida (5). Apart from coinfections, factors such as the management of the animals, their environment, and their general health status can also affect the severity of mycoplasmal disease. Therefore, strategies for the control of enzootic pneumonia are extremely important in pig production.The majority of piglets in commercial systems are routinely vaccinated against M. hyopneumoniae, and numerous studies have evaluated the efficacy and safety of vaccines under field conditions (6-8). Vaccination of pigs has been shown to reduce body weight losses and the prevalence of pigs actually observed with (pneumonic) lung lesions, as well as the severity of lesions in those pigs that are affected. Piglets are often infected by M. hyopneumoniae from their mothers (3), and field prevalence studies have indicated that between 1.5% and 4% of 1-and 3-week-old piglets tested with either nasal swabs or necropsies show positive PCR results for M. hyopneumoniae (9).We demonstrated previously...

Recent publications suggest PCV2 vaccine-induced protection is superior when the vaccine and challenge are closely matched. PCV2’s evolutionary rate, propensity for recombination, and genotype shifting, all provide rationale for modernizing PCV2 vaccines. One mechanism to increase a vaccine’s epitope breadth is by designing a bivalent vaccine. The objective of these studies was to evaluate efficacy of a monovalent (PCV1-2 chimera, cPCV2a or cPCV2b) and bivalent (cPCV2a–cPCV2b) vaccine in terms of homologous and heterologous efficacy. In Study A, pigs were vaccinated with cPCV2a or saline and challenged with PCV2a or PCV2b. In Study B, pigs were vaccinated with cPCV2a, cPCV2a–cPCV2b bivalent, or saline, and challenged with PCV2a. In Study C, pigs were vaccinated with cPCV2b, cPCV2a–cPCV2b bivalent, or saline, and challenged with PCV2b. In all studies vaccines and saline were administered intramuscularly to pigs at three to four weeks of age. Virulent PCV2b or PCV2a was administered to all animals approximately three weeks post-vaccination. Both mono and bivalent vaccinated groups demonstrated significantly lower viremia, percent of animals ever viremic, percent of animals with lymphoid depletion and/or histiocytic replacement, and percent of animals with PCV2 colonization of lymphoid tissues compared to saline controls. In Study A, a biologically relevant, though not significantly different, improvement in homologous versus heterologous protection was observed. In Studies B and C, biologically superior efficacy of the bivalent cPCV2a–cPCV2b vaccine compared to either monovalent vaccine was demonstrated. Taken together, cross-protection among mismatched PCV2 vaccine and challenge genotypes is not 100%; a bivalent PCV2 vaccine may provide the best opportunity to broaden coverage to circulating strains of PCV2.

PRRSV is one of the most important viruses in the global swine industry and is often controlled by the use of modified live virus (MLV) vaccines. This study assessed the impact of a PRRSV-1 MLV vaccine applied to 1-day-old piglets challenged on day 28 of life with a PRRSV-1 field isolate (AUT15-33). Twenty-one piglets were vaccinated within 24 h of birth (T02), whereas 20 piglets were left unvaccinated (T01). Necropsy was performed two weeks post-challenge. Comparing the two groups, T02 piglets showed significantly higher (p = 0.017) average daily weight gain. In addition, significantly lower (p < 0.0001) PRRSV RNA loads were measured in serum of T02 piglets at all investigated time points. All T01 piglets were viremic and shed virus in nasal swabs, whereas only 71.4 % and 38.1 % of the T02 group were viremic or shed virus, respectively. Piglets from T02 had significantly higher numbers (p < 0.0001) of IFN-γ producing lymphocytes compared to T01. At necropsy, differences in gross and histologic lung lesions were statistically significant (p = 0.012 and p < 0.0001, respectively) between the two groups. Hence, this MLV vaccine administered to 1-day-old piglets was able to protect piglets against PRRSV infection at weaning.