Mannose-binding lectin and complement mediate follicular localization and enhanced immunogenicity of diverse protein nanoparticle immunogens

Abstract

Nanoparticle (NP) vaccine formulations promote immune responses through multiple mechanisms. We recently reported that mannose-binding lectin (MBL) triggers trafficking of glycosylated HIV Env-immunogen NPs to lymph node follicles. Here, we investigate effects of MBL and complement on NP forms of HIV and other viral antigens. MBL recognition of oligomannose on gp120 nanoparticles significantly increases antigen accumulation in lymph nodes and antigen-specific germinal center (GC) responses. MBL and complement also mediate follicular trafficking and enhance GC responses to influenza, HBV, and HPV particulate antigens. Using model protein nanoparticles bearing titrated levels of glycosylation, we determine that mannose patches at a minimal density of 2.1 3 10 À3 mannose patches/nm 2 are required to trigger follicular targeting, which increases with increasing glycan density up to at least $8.2 3 10 À3 patches/nm 2 . Thus, innate immune recognition of glycans has a significant impact on humoral immunity, and these findings provide a framework for engineering glycan recognition to optimize vaccine efficacy.

Antigen- and scaffold-specific antibody responses to protein nanoparticle immunogens

“…This suggests that despite its relatively large size, the poorly immunogenic HIV-1 Env may impart less antigenic competition with the nanoparticle scaffold than the other more immunogenic antigens. Alternatively, more efficient trafficking of HIV-1 Env immunogens to lymph nodes due to the high oligomannose glycan density on Env 25 , 81 , 82 may be another mechanism by which the immunogenicity of the underlying I53-50 scaffold is increased. Furthermore, the ratio of antigen-specific over anti-I53-50 titers for the HIV-1 Env groups was consistently less than 1 at all time points, while the other nanoparticle immunogen groups exhibited ratios equal to or greater than 1 ( Figures 3 E and S6 A).…”

Prevaccination Glycan Markers of Response to an Influenza Vaccine Implicate the Complement Pathway

“…Immunogens that can bind MBL2 and activate complement increase response to immunogens including influenza in mouse models. 48 , 49 In line with this, deletion of the downstream complement component C3 in mice was found to lower antibody response to both live influenza virus and influenza antigen. 50 There is also evidence that C2 deficiency may be associated with weak antibody response to pneumococcal vaccines.…”

“… , The role of complement in vaccine efficacy is unclear, although several studies have found a direct link. , Complement can be triggered both by immune lectins, such as MBL2 and ficolins, or by antibodies. Immunogens that can bind MBL2 and activate complement increase response to immunogens including influenza in mouse models. , In line with this, deletion of the downstream complement component C3 in mice was found to lower antibody response to both live influenza virus and influenza antigen . There is also evidence that C2 deficiency may be associated with weak antibody response to pneumococcal vaccines .…”

“…Glycoproteomics showed that Le a was enriched in complement components such as C4BP. Multiple studies argue a direct connection between complement activation and vaccine efficacy, although the exact mechanisms are still unclear. − Our data argue that this may partly be due to the importance of glycoforms in mediating complement, which have not previously been considered. Further studies to explore how glycans such as Le a influence the functions of serum glycoproteins are warranted, especially in regard to components of the complement system and the predictive ability of glycoforms to identify nonresponders to specific vaccines.…”

“…As previously mentioned, engagement of MBL and complement has recently been shown to increase response to immunogens including influenza in mouse models. 48 , 49 Whether the changes in high mannose observed in high responders are related to this phenomenon is a point for further analysis.…”