Immunogenicity and Protective Activity of Pigeon Circovirus Recombinant Capsid Protein Virus-Like Particles (PiCV rCap-VLPs) in Pigeons (Columba livia) Experimentally Infected with PiCV

Abstract

Pigeon circovirus (PiCV) is the most recurrent virus diagnosed in pigeons and is among the major causative agents of young pigeon disease syndrome (YPDS). Due to the lack of an established laboratory protocol for PiCV cultivation, development of prophylaxis is hampered. Alternatively, virus-like particles (VLPs), which closely resemble native viruses but lack the viral genetic material, can be generated using a wide range of expression systems and are shown to have strong immunogenicity. Therefore, the use of VLPs provides a promising prospect for vaccine development. In this study, transfected human embryonic kidney (HEK-293) cells, a mammalian expression system, were used to express the PiCV capsid protein (Cap), which is a major component of PiCV and believed to contain antibody epitopes, to obtain self-assembled VLPs. The VLPs were observed to have a spherical morphology with diameters ranging from 12 to 26 nm. Subcutaneous immunization of pigeons with 100 µg PiCV rCap-VLPs supplemented with water-in-oil-in-water (W/O/W) adjuvant induced specific antibodies against PiCV. Observations of the cytokine expression and T-cell proliferation levels in spleen samples showed significantly higher T-cell proliferation and IFN- γ expression in pigeons immunized with VLPs compared to the controls (p < 0.05). Experimentally infected pigeons that were vaccinated with VLPs also showed no detectable viral titer. The results of the current study demonstrated the potential use of PiCV rCap-VLPs as an effective vaccine candidate against PiCV.

Molecular detection and phylogenetic analysis of pigeon circovirus from racing pigeons in Northern China

“…Moreover, a similar situation has been found in GuCV [ 47 ] and BFDV [ 48 ]. Since no available cell lines have been found to culture PiCV in vitro [ 49 , 50 ] and lack of commercial antibodies against PiCV Cap protein, it is hard to verify that indeed a full-length natural Cap protein is translated from the described alternative start codons. In all 68 identified Rep proteins, three amino acid motifs named FTLNNP (position 41–46), HLQGF (position 78–82), and YCSK (position 116–119) that putatively associated with RCR [ 2 ] were completely conserved.…”

Pigeon Circovirus over Three Decades of Research: Bibliometrics, Scoping Review, and Perspectives

“…Within the first decade after the short report of Schmidt [ 1 ], retrieved records showed detection of the virus in several other countries including Northern Ireland [ 16 , 34 , 69 , 70 ], Germany [ 15 , 44 ], Italy [ 31 , 71 ], France [ 72 ], Belgium [ 30 , 33 , 34 ], and Japan [ 21 , 38 ]. Meanwhile, between 2003 and 2012, researchers in Czech Republic [ 29 , 32 ], Poland [ 36 , 58 , 67 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 ], Denmark [ 30 ], Slovenia [ 81 , 82 ], Hungary [ 66 , 83 ], United Arab Emirates [ 84 ], Libya [ 85 ], Nigeria [ 83 , 86 ], and Taiwan [ 59 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ] reported first local detections of PiCV. Lastly, during the most recent decade of PiCV research, new publications and reports were also produced from Brazil [ 40 ], Iran [ 94 , 95 ], Iraq […”

“…To date, no commercial vaccine is available to control PiCV infections. Experimental studies on the production of the recombinant capsid protein and the evaluation of its potential use as an antigen for vaccine formulations have been reported in the literature [ 79 , 93 ]. Moreover, probiotics and interferons have also been reportedly explored as alternative and/or supplemental modalities to control the effects of PiCV infections [ 90 , 91 ].…”

“…Additionally, the mechanism by which PiCV infection contributes to the development of YPDS has also been described in various descriptions of certainties, ranging from “assumed to induce immunosuppression”, “possibly by immunosuppression”, to “causes profound immunosuppression”. See [ 22 , 23 , 33 , 40 , 44 , 48 , 58 , 59 , 66 , 67 , 75 , 77 , 79 , 84 , 88 , 89 , 90 , 93 , 94 , 95 , 100 , 101 , 102 , 104 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 ]. To us, these degrees of variability among these descriptors do not seem to correlate with time.…”

“…These are all also while other records explicitly state that YPDS is a consequence of PiCV infection and subsequent immunosuppression, or categorically require specific conditions for YPDS diagnosis, such as the observation of both clinical symptoms and PiCV-specific histological lesions, presence of viral particles, and a demonstration of the presence of a large amount of viral DNA. See [ 22 , 23 , 33 , 40 , 56 , 57 , 58 , 59 , 67 , 77 , 79 , 80 , 90 , 93 , 96 , 100 , 105 , 109 , 110 , 111 , 113 , 117 ].…”