Malfetano, J. | Search bioRxiv

bioRxiv2024

Mechanistic insights into structure-based design of a Lyme disease subunit vaccine

The quality of protective immunity plays a critical role in modulating vaccine efficacy, with native antigens often not able to trigger sufficiently strong immune responses for pathogen killing. This warrants creation of structure-based vaccine design, leveraging high-resolution antigen structures for mutagenesis to improve protein stability and efficient immunization strategies. Here, we investigated the mechanisms underlying structure-based vaccine design using CspZ-YA, a vaccine antigen from Borrelia burgdorferi, the bacteria causing Lyme disease (LD), the most common vector-borne disease in the Northern Hemisphere. Compared to wild-type CspZ-YA, we found CspZ-YAI183Y and CspZ-YAC187S required lower immunization frequency to protect mice from LD-associated manifestations and bacterial colonization. We observed indistinguishable human and mouse antigenicity between wild-type and mutant CspZ-YA proteins after native infection or active immunization. This supports our newly generated, high-resolution structures of CspZ-YAI183Y and CspZ-YAC187S, showing no altered surface epitopes after mutagenesis. However, CspZ-YAI183Y and CspZ-YAC187S favored the interactions between helices H and I, consistent with their elevated thermostability. Such findings are further strengthened by increasing ability of protective CspZ-YA monoclonal antibodies in binding to CspZ-YA at a physiological temperature (37{degrees}C). Overall, this study demonstrated enhanced intramolecular interactions improved long-term stability of antigens while maintaining protective epitopes, providing a mechanism for structure-based vaccine design. These findings can ultimately be extended to other vaccine antigens against newly emerging pathogens for the improvement of protective immunity.

immunology↗

bioRxiv2024

Complement therapeutic Factor H-IgG proteins as pre-exposure prophylaxes against Lyme borreliae infections

Lyme disease (LD) is the most common vector-borne disease in the northern hemisphere and is caused by the bacteria Borrelia burgdorferi sensu lato (also known as Lyme borreliae) with no effective prevention available. Lyme borreliae evade complement killing, a critical arm of host immune defense, by producing outer surface proteins that bind to a host complement inhibitor, factor H (FH). These outer surface proteins include CspA and CspZ, which bind to the 6th and 7th short consensus repeats of FH (SCR(6-7)), and the OspE family of proteins (OspE), which bind to the 19th and 20th SCR (SCR19-20). In this study, we produced two chimeric proteins, FH-Fc, containing the Fc region of immunoglobulin G (Fc) with SCR(6-7) or SCR(19-20). We found that both FH-Fc constructs killed B. burgdorferi in the presence of complement and reduced bacterial colonization and LD-associated joint inflammation in vivo. While SCR(6-7)-Fc displayed Lyme borreliae species-specific bacterial killing, SCR(19-20)-Fc versatilely eradicated all tested bacterial species/strains. This correlated with SCR(6-7)-Fc binding to select variants of CspA and CspZ, but SCR(19-20)-Fc binding to all tested OspE variants. Overall, we demonstrated the concept of using FH-Fc constructs to kill Lyme borreliae and defined underlying mechanisms, highlighting the potential of FH-Fc as a pre-exposure prophylaxis against LD infection. AUTHOR SUMMARYTransmitted by ticks, Lyme disease (LD) is the most common vector-borne disease in North America and has experienced an expanded geographical range and increasing number of cases in recent years. No effective prevention is currently available. The causative agent of LD, Borrelia burgdorferi sensu lato (Bbsl), is a complex containing a variety of species. To escape from killing by complement, one of the mammalian host defense mechanisms, Bbsl produces outer surface proteins that bind to a complement inhibitor, factor H (FH). These FH-binding proteins (i.e., CspA, CspZ, and OspE) evade complement by recruiting FH to the bacterial surface. Here we produced two FH-Fc fusion proteins, which combine human immunoglobulin Fc with the human FH domains that bind to Bbsl FH-binding proteins. We found that FH-Fc constructs kill Bbsl in vitro and prevent colonization and LD manifestations in murine models, correlating with these FH-Fc constructs ability to bind to CspA, CspZ, and OspE from respective Bbsl species. These results suggest the possibility of using FH-Fc as a prevention against LD.

microbiology↗