Adjuvant effects of mannose-binding lectin ligands on the immune response to infectious bronchitis vaccine in chickens with high or low serum mannose-binding lectin concentrations

Abstract

Mannose-binding lectin (MBL) plays a major role in the immune response as a soluble pattern-recognition receptor. MBL deficiency and susceptibility to different types of infections have been subject to extensive studies over the last decades. In humans and chickens, several studies have shown that MBL participates in the protection of hosts against virus infections. Infectious bronchitis (IB) is a highly contagious disease of economic importance in the poultry industry caused by the coronavirus infectious bronchitis virus (IBV). MBL has earlier been described to play a potential role in the pathogenesis of IBV infection and the production of IBV-specific antibodies, which may be exploited in optimising IBV vaccine strategies. The present study shows that MBL has the capability to bind to IBV in vitro. Chickens from two inbred lines (L10H and L10L) selected for high or low MBL serum concentrations, respectively, were vaccinated against IBV with or without the addition of the MBL ligands mannan, chitosan and fructooligosaccharide (FOS). The addition of MBL ligands to the IBV vaccine, especially FOS, enhanced the production of IBV-specific IgG antibody production in L10H chickens, but not L10L chickens after the second vaccination. The addition of FOS to the vaccine also increased the number of circulating CD4+ cells in L10H chickens compared to L10L chickens. The L10H chickens as well as the L10L chickens also showed an increased number of CD4-CD8α-γδ T-cells when an MBL ligand was added to the vaccine, most pronouncedly after the first vaccination. As MBL ligands co-administered with IBV vaccine induced differences between the two chicken lines, these results indirectly suggest that MBL is involved in the immune response to IBV vaccination. Furthermore, the higher antibody response in L10H chickens receiving vaccine and FOS makes FOS a potential adjuvant candidate in an IBV vaccine.

Chicken mannose binding lectin has antiviral activity towards infectious bronchitis virus

“…For mammalian MBL, direct virus neutralization through interaction with viral glycoproteins, thereby blocking virus binding to receptors on host cells, has been described before (Brown et al, 2010;Ip et al, 2005;Ji et al, 2005;Zhou et al, 2010). Here, we observed that rcMBL binds two IBV strains, IBV-Beaudette and IBV-M41, in line with a previous observation with an unspecified IBV strain (Kjaerup et al, 2014a). As spike proteins of all other IBV strains are, while diverse in sequence, heavily glycosylated (with approximately 30 predicted N-linked glycosylation sites), it is expected that rcMBLs antiviral activity extends beyond IBV geno-or serotypes.…”

“…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).…”

Mannose-binding lectin and ficolin-2 do not influence humoral immune response to hepatitis B vaccine

“…Interestingly, a recent study in chickens has successfully explored a vaccine preparation that contains an MBL ligand able to inhibit MBL binding and activation of the lectin pathway of complement, in order to achieve a sufficient antibody response after vaccination [33]. A similar approach would certainly be feasible in humans in addition to systemic inhibition of MBL by recombinant human C1 inhibitor [34].…”

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

“…Receptors such as the toll-like receptor (TLR) 3, TLR7, and TLR2/6 may initiate the local trachea innate immune response upon IBV recognition (21,57). Since mannosebinding lectin (MBL) binds to IBV (36), early events in the immune response to IBV infection may involve MBL by opsonization of free virions, by complement activation at mucosal sites, or by inhibition of the virus entry through sialic acid-dependent receptors (21,31,32,47,63). In mammals, the complement system has been suggested to be important in T-cell activation together with the production of types I and II interferons (IFNs) and other mediators, which trigger the antiviral state of neighboring cells and the influx of T cells to the local tissue (35).…”