Targeted Alteration of Antibody-Based Immunodominance Enhances the Heterosubtypic Immunity of an Experimental PCV2 Vaccine

Despite the availability of commercial vaccines which can effectively prevent clinical signs, porcine circovirus type 2 (PCV2) continues to remain an economically important swine virus, as strain drift, followed by displacement of new subtypes, occurs periodically. We had previously determined that the early antibody responses to the PCV2 capsid protein in infected pigs map to immunodominant but non-protective, linear B cell epitopes. In this study, two of the previously identified immunodominant epitopes were mutated in the backbone of a PCV2b infectious clone, to rationally restructure the immunogenic capsid protein. The rescued virus was used to immunize 3-week-old weanling piglets, followed by challenge with a virulent heterologous PCV2d strain. As expected, immunodominant antibody responses to the targeted epitopes were abrogated in vaccinated pigs, while a broadening of the virus neutralization responses was detected. Vaccinated pigs were completely protected against challenge viral replication, had reduced microscopic lesions in lymphoid organs and gained significantly more body weight when compared to unvaccinated pigs. Thus, the experimental PCV2 vaccine developed was highly effective against challenge, and, if adopted commercially, can potentially slow down or eliminate new strain creation.

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Effects of an Inactivated Porcine Circovirus Type 2 (PCV2) Vaccine on PCV2 Virus Shedding in Semen from Experimentally Infected Boars

Clinical and Vaccine Immunology ◽

10.1128/cvi.05027-11 ◽

2011 ◽

Vol 18 (7) ◽

pp. 1091-1096 ◽

Cited By ~ 9

Author(s):

Hwi Won Seo ◽

Kiwon Han ◽

Duyeol Kim ◽

Yeonsu Oh ◽

Ikjae Kang ◽

...

Keyword(s):

Immunological Response ◽

Porcine Circovirus Type ◽

Porcine Circovirus Type 2 ◽

Porcine Circovirus ◽

Virus Shedding ◽

Pcv2 Vaccine ◽

Group 3 ◽

Group 2 ◽

Negative Controls

ABSTRACTThe objective of the present study was to determine the effect of an inactivated porcine circovirus type 2 (PCV2) vaccine on PCV2b virus shedding in the semen of experimentally infected boars by measuring the immunological response and the PCV2b DNA load in blood and semen. Twelve boars were randomly divided into three groups. The boars in group 1 (n= 4) were immunized with an inactivated PCV2 vaccine and were challenged with PCV2b. The boars in group 2 (n= 4) were only challenged with PCV2b. The boars in group 3 (n= 4) served as negative controls. The number of PCV2 genome copies of PCV2 in the serum and semen were significantly lower in vaccinated challenged boars than in nonvaccinated challenged boars at 7, 10, 14, 21, 32, 35, 42, 49, and 60 days postinoculation. The number of PCV2b genomes in the semen correlated with the number of PCV2b genomes in the blood in both vaccinated challenged (R= 0.714) and nonvaccinated challenged (R= 0.861) boars. The results of the present study demonstrate that the inactivated PCV2 vaccine significantly decreases the amount of PCV2b DNA shedding in semen from vaccinated boars after experimental infection with PCV2b.

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Diagnosis of post-weaning multisystemic wasting syndrome in pigs in Brazil caused by porcine circovirus type 2

Arquivo Brasileiro de Medicina Veterinária e Zootecnia ◽

10.1590/s0102-09352003000500002 ◽

2003 ◽

Vol 55 (5) ◽

pp. 522-527 ◽

Cited By ~ 12

Author(s):

J.R. Ciacci-Zanella ◽

N. Morés

Keyword(s):

Clinical Signs ◽

Rflp Analysis ◽

Porcine Circovirus Type ◽

Porcine Circovirus Type 2 ◽

Porcine Circovirus ◽

Nested Polymerase Chain Reaction ◽

Wasting Syndrome ◽

Thymus Atrophy ◽

Granulomatous Lymphadenitis

This report describes the first preliminary characterization of porcine circovirus type 2 (PCV2) isolates from pigs affected with post-weaning multisystemic wasting syndrome (PMWS) in Brazil. Diseased pigs were examined at necropsy and by histopathology. Macroscopic and microscopic analyses revealed lesions reported to be typical of PMWS, which included, respectively, emaciation, enlargement of lymph nodes, thymus atrophy and interstitial pneumonia, and granulomatous lymphadenitis with syncytial cells, among others. Using nested polymerase chain reaction (PCR) or imunoperoxidase it was possible to detected DNA or antigen of PCV2, respectively. The PCR' s amplified fragment could be differentiated from PCV1 and PCV2 from one another by restriction fragment length polymorphism (RFLP) analysis. PCV2 DNA was detected in 70% (14/20) of samples of pigs with clinical signs and lesions associated with PMWS. This study shows that PCV2 is associated with lesions and symptoms indicative of PMWS in pigs. It is also shown that the Brazilian PCV2 isolates may have variation in their genome.

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Two Amino Acid Mutations in the Capsid Protein of Type 2 Porcine Circovirus (PCV2) Enhanced PCV2 Replication In Vitro and Attenuated the Virus In Vivo

Journal of Virology ◽

10.1128/jvi.78.24.13440-13446.2004 ◽

2004 ◽

Vol 78 (24) ◽

pp. 13440-13446 ◽

Cited By ~ 78

Author(s):

M. Fenaux ◽

T. Opriessnig ◽

P. G. Halbur ◽

F. Elvinger ◽

X. J. Meng

Keyword(s):

Capsid Protein ◽

Vaccine Development ◽

Porcine Circovirus Type ◽

Postweaning Multisystemic Wasting Syndrome ◽

Porcine Circovirus ◽

Entire Genome ◽

Wasting Syndrome

ABSTRACT Porcine circovirus type 2 (PCV2) is the primary causative agent of postweaning multisystemic wasting syndrome (PMWS) in pigs. To identify potential genetic determinants for virulence and replication, we serially passaged a PCV2 isolate 120 times in PK-15 cells. The viruses harvested at virus passages 1 (VP1) and 120 (VP120) were biologically, genetically, and experimentally characterized. The PCV2 VP120 virus replicated in PK-15 cells to a titer similar to that of the PK-15 cell line-derived nonpathogenic PCV1 but replicated more efficiently than PCV2 VP1 with a difference of about 1 log unit in the titers. The complete genomic sequences of viruses at passages 0, 30, 60, 90, and 120 were determined. After 120 passages, only two nucleotide mutations were identified in the entire genome, and both were located in the capsid gene: the mutations were located at nucleotide positions 328 (C328G) and 573 (A573C). The C328G mutation, in which a proline at position 110 of the capsid protein changed to an alanine (P110A), occurred at passage 30 and remained in the subsequent passages. The second mutation, A573C, resulting in a change from an arginine to a serine at position 191 (R191S), appeared at passage 120. To experimentally characterize the VP120 virus, 31 specific-pathogen-free pigs were randomly divided into three groups. Ten pigs in group 1 received phosphate-buffered saline as negative controls. Each pig in group 2 (11 pigs) was inoculated intramuscularly and intranasally with 104.9 50% tissue culture infective doses (TCID50) of PCV2 VP120. Each pig in group 3 (10 pigs) was similarly inoculated with 104.9 TCID50 of PCV2 VP1. Viremia was detected in 9 of 10 pigs in the PCV2 VP1 group with a mean duration of 3 weeks, but in only 4 of 11 pigs in the PCV2 VP120 group with a mean duration of 1.6 weeks. The PCV2 genomic copy numbers in serum in the PCV2 VP1 group were significantly higher than those in the PCV2 VP120 group (P < 0.0001). Gross and histopathologic lesions in pigs inoculated with PCV2 VP1 were more severe than those inoculated with PCV2 VP120 at both day 21 and 42 necropsies (P = 0.0032 and P = 0.0274, respectively). Taken together, the results from this study indicated that the P110A and R191S mutations in the capsid of PCV2 enhanced the growth ability of PCV2 in vitro and attenuated the virus in vivo. This finding has important implications for PCV2 vaccine development.

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