The aim of this study was to evaluate the protective efficacy of the CIRCOQ porcine circovirus type 2 (PCV2) subunit vaccine in piglets with high maternally derived antibodies (MDAs) against disease caused by natural infection with PCV2d. A total of 130 weaned, 21-day-old healthy pigs was allocated into 3 trial groups. The signs of respiratory disorder were higher in unvaccinated pigs than in vaccinated pigs at 13 to 17 weeks old (P < 0.05), 18 to 22 weeks old (P < 0.001), and 23 to 27 weeks old (P < 0.01). The unvaccinated pigs had an early rate of dermatitis at 8 to 12 weeks old (10.0%), 13 to 17 weeks old (30.0%), 18 to 22 weeks old (46.7%), and 23 to 27 weeks old (33.3%), while there were no cases of dermatitis in vaccinated pigs. There was a significant difference (P < 0.05) in the mortality of pigs in the unvaccinated group and the 2-dosed vaccinated group. PCV2 viremia was detected in the blood and peaked at 105 days old in both unvaccinated pigs (Ct-adj = 8.40) and pigs vaccinated with 1 dose (Ct-adj = 6.37), while no detectable PCV2 virus was found in the blood of pigs vaccinated with 2 doses. At 77 and 105 days old, the PCV2 viremia load (Ct-adj) of unvaccinated pigs and those vaccinated with 1 dose was significantly higher (P < 0.05) than that of the 2-dosed vaccinated pigs. The body weight (BW), average weight gain (AWG), and average daily gain (ADG) in both groups of vaccinated pigs were significantly higher (P < 0.05) than those of unvaccinated pigs. The study vaccine was significantly efficacious in protecting vaccinated pigs against clinical symptoms, blood viral load, and mortality, as well as improving productivity, compared with unvaccinated pigs.

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.

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.

The efficacy of 4 commercial porcine reproductive and respiratory syndrome virus (PRRSV) modified-live vaccines (MLV), against PRRSV-1 and PRRSV-2 was evaluated and compared in growing pigs. Two of the vaccines were based on PRRSV-1 and two on PRRSV-2. There were no significant differences between each of the two PRRSV-1 MLV vaccines and the two PRRSV-2 MLV vaccines respectively based on virology, immunological, and pathological evaluations. Vaccination with either of the PRRSV-1 MLV vaccines resulted in reduced PRRSV-1 but not PRRSV-2 viremia. Additionally, vaccination with either of the PRRSV-1 MLV vaccines resulted in reduction of lung lesions and PRRSV-1 positive cells in PRRSV-1 challenged pigs but had no significant effect in PRRSV-2 challenged pigs. In contrast, vaccination with either of the two PRRSV-2 MLV vaccines resulted in the reduction of both PRRSV-1 and PRRSV-2 viremia. The PRRSV-2 MLV vaccines were also able to effectively reduce lung lesions and PRRSV positive cells after challenge with either PRRSV-1 or PRRSV-2. Our data suggest that while vaccination with PRRSV-1 MLV vaccines can be effective against PRRSV-1, only PRRSV-2 MLV vaccines can protect against both Korean PRRSV-1 and PRRSV-2 challenges in this study.

The objective of this study was to compare the protection against challenge with porcine circovirus 2 (PCV2) induced by an experimental vaccine based on open reading frame (ORF) 2 of PCV2 DNA plus an adjuvant (aluminum hydroxide, cobalt oxide, or liposome) and a commercial PCV2 subunit vaccine. A total of 35 colostrum-fed, cross-bred, conventional piglets were randomly divided into 7 groups. The commercial vaccine was more efficacious against PCV2 challenge than the 4 experimental vaccines according to immunologic, virologic, and pathological outcomes. The pigs inoculated with the experimental vaccine containing the liposome adjuvant had significantly higher levels (P < 0.05) of neutralizing antibodies and interferon-γ-secreting cells, and significantly lower levels (P < 0.05) of PCV2 viremia than the pigs inoculated with the other experimental vaccines. The pigs inoculated with the experimental vaccines containing either the liposome adjuvant or the cobalt oxide adjuvant had significantly lower lymphoid lesion scores (P < 0.05) than the pigs in the group inoculated with the PCV2 DNA vaccine dissolved in phosphate-buffered saline. Liposome proved to be a potent adjuvant that efficiently enhanced both humoral and cellular immune responses induced by the PCV2 DNA vaccine.

The objective of this study was to evaluate a new recombinant chimeric vaccine against porcine reproductive and respiratory syndrome virus (PRRSV). The subunit vaccine, PRRSFREE, from Reber Genetics, Taiwan, Republic of China, is based on a plasmid containing a detoxified Pseudomonas exotoxin carrying open reading frame (ORF) 7, 1b, and 5 and 6 chimeric subunits of types 1 and 2 PRRSV. Pigs were injected intramuscularly with 2.0 mL of the vaccine at 21 and 42 d of age, according to the manufacturer's recommendation. At the age of 63 d the pigs were inoculated intranasally with either type 1 or type 2 PRRSV. Regardless of the genotype of the challenging PRRSV, the vaccinated challenged pigs had significantly lower (P < 0.05) mean rectal temperature, respiratory score, lung lesion score, and amount of PRRSV antigen within areas of interstitial pneumonia, along with overall lower levels of viremia due to type 1 or type 2 PRRSV compared with the unvaccinated challenged pigs. The vaccinated challenged pigs also had significantly higher (P < 0.05) numbers of interferon-γ secreting cells compared with the unvaccinated challenged pigs. This study demonstrated that the new vaccine provides protection against respiratory disease from heterologous types 1 and 2 PRRSV challenge in growing pigs.

Commercial vaccines against Porcine circovirus type 2 (PCV2) are widely used on swine farms. Marked body weight variation at marketing age is a problem on conventional pig farms using all-in/all-out barn management. The aim of this study was to investigate whether PCV2 infection could be a factor influencing body weight variation. Seven conventional farms that routinely used PCV2 vaccination were selected, and 60 serum samples from light and heavy pigs at each site were tested for PCV2 antibody titers and viremia. At 3 farms the mean antibody titer, proportion of viremic pigs, and virus load differed significantly between the light and heavy groups. These preliminary results suggest that PCV2 infection may be a factor contributing to weight variation in vaccinated market-age hogs.

Objective: To evaluate onset of protection induced by modified-live virus (MLV) bovine viral diarrhea virus (BVDV) vaccine administered 7, 5, or 3 days before inoculation with type 1b BVDV (strain NY-1). Animals: 40 calves. Procedures: Calves were assigned to 4 groups: an unvaccinated control group or groups vaccinated with MLV vaccine containing BVDV types 1a and 2 at 7, 5, or 3 days, before inoculation with NY-1 BVDV. Blood samples were collected for leukocyte counts, serum virus neutralization, and virus isolation (VI); nasal swab specimens (NSSs) were obtained for VI, and rectal temperatures were monitored for 14 days after inoculation. Results: No significant differences in leukocyte counts or rectal temperatures were detected after BVDV inoculation in vaccinated calves. Vaccinated calves had reduced viremia and viral shedding after inoculation, compared with results for unvaccinated calves. On day 5 after inoculation, a higher proportion of calves vaccinated 3 days before inoculation had positive VI from NSSs, compared with NSS VI results for calves vaccinated 5 and 7 days before inoculation. Unvaccinated calves had leukopenia on days 3, 5, and 6 and had higher rectal temperatures on days 7 and 8 after inoculation, compared with temperatures before inoculation. All unvaccinated calves had ≥ 1 positive VI result from NSSs 3 to 11 days after inoculation, and 4 became viremic. Conclusions and Clinical Relevance: MLV BVDV vaccine prevented fever, viremia, and leukopenia in calves challenge inoculated with NY-1 BVDV. A high proportion of calves vaccinated 3 days before inoculation shed BVDV after inoculation.

The early release of cytokines by cells involved in innate immunity is an important host response to intracellular pathogens. Gamma interferon (IFN-gamma) is an important cytokine produced during the early stages of an infection by macrophages, natural killer (NK) cells, and other cell types, and it is also a central cytokine mediator for the induction of cellular or Th1 immunity. To better understand innate and adaptive immune responses after infection with Porcine reproductive and respiratory syndrome virus (PRRSV), we investigated serum IFN-gamma concentrations and the duration of viremia. For 2 strains of atypical PRRSV, IFN-gamma was detectable in swine serum soon after infection and lasted for approximately 3 wk. Serum concentrations of IFN-gamma peaked at about 10 d after inoculation and returned to approximately baseline levels by day 22. However, individual pigs manifested short, sporadic increases in the serum concentration of IFN-gamma from 18 to 50 d after inoculation. Prior vaccination blocked the serum IFN-gamma response associated with homologous virus challenge and altered the kinetics of the response after heterologous challenge. Two other respiratory viruses of pigs, Porcine respiratory coronavirus and Swine influenza virus, do not appear to induce serum IFN-gamma. The early production of IFN-gamma in PRRSV-infected pigs might result from activation of NK cells, a response that is more characteristic of immune pathways stimulated by intracellular bacterial and protozoan infections.