Abstract
To understand the differences in immune responses between early feathering (EF) and late feathering (LF) chickens after infection with avian leukosis virus, subgroup J (ALV-J), we monitored the levels of prolactin, growth hormone and the immunoglobulins IgG and IgM in the serum of LF and EF chickens for 8 weeks. Moreover, we analysed the expression of immune-related genes in the spleen and the expression of PRLR, SPEF2 and dPRLR in the immune organs and DF-1 cells by qRT–PCR. The results showed that ALV-J infection affected the expression of prolactin, growth hormone, IgG and IgM in the serum. Regardless of whether LF and EF chickens were infected with ALV-J, the serum levels of the two hormones and two immunoglobulins in EF chickens were higher than those in LF chickens (P < 0.05). However, the expression of immune-related genes in the spleen of positive LF chickens was higher than that in the spleen of positive EF chickens. In the four immune organs, PRLR and SPEF2 expression was also higher in LF chickens than in EF chickens. Furthermore, the dPRLR expression of positive LF chickens was higher than that of negative LF chickens. After infection with ALV-J, the expression of PRLR in DF-1 cells significantly increased. In addition, overexpression of PRLR or dPRLR in DF-1 cells promoted replication of ALV-J. These results suggested that the susceptibility of LF chickens to ALV-J might be induced by dPRLR.
Highlights
Avian leukosis virus (ALV) is an oncogenic retrovirus that causes immunosuppression and neoplastic diseases [1]
Regardless of the ALV-J infection status, the serum Growth hormone (GH) levels of late feathering (LF) chickens were always lower than those of early feathering (EF) chickens (Figures 1C, D). One explanation for these results is that PRL can bind to both prolactin receptor (PRLR) and DPLR in LF chickens, which may lead to lower PRL levels in LF chickens than in EF chickens
The results showed that the expression of the PRLR and sperm flagellar 2 (SPEF2) genes in each immune organ was significantly higher in LF chickens than in EF chickens (P < 0.05)
Summary
Avian leukosis virus (ALV) is an oncogenic retrovirus that causes immunosuppression and neoplastic diseases [1]. ALV-J has been found to infect many egg-type stocks and local Chinese breeds, Sex identification of chicks can be based on the difference in rates of feather growth, which can be divided into an early feathering (EF) type and a late feathering (LF) type. Both the EF and LF types contain the prolactin receptor (PRLR) and sperm flagellar 2 (SPEF2) genes in their genetic structure. Breeders use the different feather growth rates for sex determination and have found that EF and LF chickens respond differently to ALV-J infection. Some White Leghorn breeders have reported reduced production and slightly higher mortality in female progeny from dams
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