Immunogenicity of Pigeon Circovirus Recombinant Capsid Protein in Pigeons

Abstract

Pigeon circovirus (PiCV) is the most frequently diagnosed virus in pigeons and is thought to be one of the causative factors of a complex disease called the young pigeon disease syndrome (YPDS). The development of a vaccine against this virus could be a strategy for YPDS control. Since laboratory culture of PiCV is impossible, its recombinant capsid protein (rCP) can be considered as a potential antigen candidate in sub-unit vaccines. The aim of this basic research was to evaluate the immune response of pigeons to PiCV rCP. Sixty six-week-old carrier pigeons were divided into two groups (experimental immunized with PiCV rCP mixed with an adjuvant, and control immunized with an adjuvant only), and immunized twice in a 21-day interval. On the day of immunization and on two, 23, 39, and 46 days post first immunization (dpv), samples of blood, spleen, and bursa of Fabricius were collected from six birds from each group to examine anti-PiCV rCP IgY, anti-PiCV rCP IgY-secreting B cells (SBC), IFN-γ gene expression, and percentage of T CD3+, CD4+, CD8+, and B IgM+ lymphocytes. The results indicated a correct immune response to PiCV rCP both in humoral and cell-mediated immunity, which was manifested by seroconversion since 23 dpv, by a significantly higher anti-PiCV rCP IgY-SBC number on two and 23 dpv, and significantly higher IFN-γ gene expression since two dpv. There were no significant differences or trends noted between particular T and B lymphocyte subpopulations. To conclude, PiCV rCP may be deemed immunogenic and could be considered as an antigen candidate in sub-unit vaccines against PiCV infections in pigeons.

Comparison of the immune response to vaccination with pigeon circovirus recombinant capsid protein (PiCV rCP) in pigeons uninfected and subclinically infected with PiCV

“…Located on the complementary sense strand ORF, C1, encodes the viral capsid protein (Cap protein, CP) [1, 2]. The CP of circoviruses has been documented to exhibit antigenic properties, as confirmed in the case of porcine circovirus genotype 2 (PCV2), psittacine circovirus, and pigeon circovirus [3–5].…”

The Clinical Infection with Pigeon Circovirus (PiCV) Leads to Lymphocyte B Apoptosis But Has No Effect on Lymphocyte T Subpopulation

“…For this reason, every method used for cell isolation should not lead to cellular death. Unfortunately, bF as well as thymus contain high amounts of fibrous connective tissue, and therefore, collagenase needs to be used during mononuclear cell isolation [21]. The treatment with collagenase leads to cellular death, which is why neither bF nor thymus was used for flow cytometry in our study.…”

“…One of our previous studies has revealed that the secondary immune organ-spleen-could be useful for flow cytometry, because the isolation of splenic mononuclear cells does not require digestion with collagenase, and simple tissue homogenization with the use of a manual grinder is enough. Moreover, high populations of both T and B cells are present in this organ [21,22], and for this reason, we decided to use spleen samples for the isolation of mononuclear cells.…”

“…Mononuclear cells from the whole spleens collected from each bird were isolated with the method described previously [21]. Afterward, the absolute lymphocyte count (ALC) was determined in each sample with a Vi-cell XR automatic cell viability analyzer (Beckman Coulter, Brea, CA, USA).…”

“…The mononuclear cells isolated from spleen samples were standardized to 1 × 10 6 . Next, they were stained for T cells with anti-CD3 (PE) specific monoclonal antibodies obtained in our previous study [21] and for B cells with anti-IgM (FITC) polyclonal antibodies (Biorad, Hercules, CA, USA). After staining, the samples were incubated in darkness on ice for 30 min.…”