Characterization of Cellular and Humoral Immune Responses After IBV Infection in Chicken Lines Differing in MBL Serum Concentration

Abstract

Chickens from two inbred lines selected for high (L10H) or low (L10L) mannose-binding lectin (MBL) serum concentrations were infected with infectious bronchitis virus (IBV), and innate as well as adaptive immunological parameters were measured throughout the experimental period. Chickens with high MBL serum concentrations were found to have less viral load in the trachea than chickens with low MBL serum concentrations indicating that these chickens were less severely affected by the infection. This study is the first to show that MBL expression is present in the lungs of healthy chickens and that the expression is upregulated at days 3 postinfection (p.i.) in L10H chickens. Furthermore, in the liver of infected chickens, the MBL expression was upregulated at day 7 p.i., despite the fact that the MBL serum concentrations were decreased below baseline at that time point. The number of TCRcd + CD8a + cells in the blood of noninfected chickens increased from week 0 to 3 p.i. However, the number of cells was higher in L10H chickens than in L10L chickens throughout the experiment. No increase was observed in the number of TCRcd + CD8a + cells in the blood of the infected L10H and L10L chickens. The numbers of B cells at week 3 p.i. were higher for noninfected L10L chickens than for the other chickens. No differences were observed between the infected and noninfected L10H chickens or between the infected L10H and L10L chickens. Furthermore, at week 3 p.i., the number of monocytes was higher in infected and noninfected L10H chickens than in the infected and noninfected L10L chickens. Thus, these results indicate that MBL is produced locally and may be involved in the regulation of the cellular immune response after an IBV infection. However, MBL did not appear to influence the humoral immune response after IBV infection in this study.

Chicken mannose binding lectin has antiviral activity towards infectious bronchitis virus

“…Similar observations have been done in mice, where MBL was present in bronchoalveolar lavage fluid of influenza A virus (IAV-H1N1) infected, but not in that of healthy mice (Reading et al, 1997). Indeed, after IBV infection an increase in cMBL gene expression was measured in the trachea of chicken (Kjaerup et al, 2014b), but whether this leads to an increased cMBL production and secretion needs to be confirmed. Interestingly, serum cMBL showed an acute response during IBV infection with an approximately two-fold increase in concentration (Juul-Madsen et al, 2011;Nielsen et al, 1998Nielsen et al, , 1999.…”

“…The complement activation in chickens appeared to be correlated with the cMBL concentration in serum (Juul-Madsen et al, 2003) suggesting that opsonization via complement might play a role to reduce virus titers. Indeed, reduced viral loads were observed in trachea in chickens with high MBL serum concentrations compared to those having low MBL (Kjaerup et al, 2014b). However, as many other genes are differentially expressed between the high and low MBL producing chicken breeds (Hamzic et al, 2016) the contribution of other factors cannot be ruled out.…”

“…Recent evidence showed that chicken mannose binding lectin (cMBL) plays a role in immunity against both viral and bacterial pathogens in chickens (Kjaerup et al, 2014b;Norup et al, 2009;Ulrich-Lynge et al, 2015. Chicken MBL seems to be important for shaping both the innate and the adaptive immune response for IBV (Hamzic et al, 2016;Juul-Madsen et al, 2011;Kjaerup et al, 2014b).…”

“…Recent evidence showed that chicken mannose binding lectin (cMBL) plays a role in immunity against both viral and bacterial pathogens in chickens (Kjaerup et al, 2014b;Norup et al, 2009;Ulrich-Lynge et al, 2015. Chicken MBL seems to be important for shaping both the innate and the adaptive immune response for IBV (Hamzic et al, 2016;Juul-Madsen et al, 2011;Kjaerup et al, 2014b). Chickens with relatively high concentrations of cMBL appeared to clear IBV quicker and showed reduced viral titers in trachea compared to chickens with low cMBL levels (Juul-Madsen et al, 2011;Kjaerup et al, 2014a).…”

CD59 association with infectious bronchitis virus particles protects against antibody-dependent complement-mediated lysis

“…IBV is a highly contagious pathogen of poultry and has caused extensive economic losses to the poultry industry globally [15]. Mannose-binding lectin can inhibit IBV replication in the trachea by activating the complement system [16,17], but the role of host complement regulators in IBV infection remains unclear. In the present study, we investigated the association of CD59 protein with IBV virions and its potential role in IBV infection, in view of the fact that CD59 is a distinct complement regulator that prevents MAC [C5b-9(n)] formation at the terminal pathway of complement activation [18,19].…”