PilVax – a novel peptide delivery platform for the development of mucosal vaccines

Abstract

Peptide vaccines are an attractive strategy to engineer the induction of highly targeted immune responses and avoid potentially allergenic and/or reactogenic protein regions. However, peptides by themselves are often unstable and poorly immunogenic, necessitating the need for an adjuvant and a specialised delivery system. We have developed a novel peptide delivery platform (PilVax) that allows the presentation of a stabilised and highly amplified peptide as part of the group A streptococcus serotype M1 pilus structure (PilM1) on the surface of the non-pathogenic bacterium Lactococcus lactis. To show proof of concept, we have successfully inserted the model peptide Ova324–339 into 3 different loop regions of the backbone protein Spy0128, which resulted in the assembly of the pilus containing large numbers of peptide on the surface of L. lactis. Intranasal immunisation of mice with L. lactis PilM1-Ova generated measurable Ova-specific systemic and mucosal responses (IgA and IgG). Furthermore, we show that multiple peptides can be inserted into the PilVax platform and that peptides can also be incorporated into structurally similar, but antigenically different pilus structures. PilVax may be useful as a cost-effective platform for the development of peptide vaccines against a variety of important human pathogens.

PilVax, a novel Lactococcus lactis‐based mucosal vaccine platform, stimulates systemic and mucosal immune responses to Staphylococcus aureus

“…This is the first demonstration that incorporation of a linear B-cell epitope into the PilVax platform can stimulate local and systemic antibodies after delivery to the nasal mucosa, building on a previous study showing that this approach generates specific antibody responses to OVA 324-339, a model antigen and major histocompatibility complex II epitope. 12 Unsurprisingly, there was no indication that this delivery strategy stimulated cellular immune responses to the FnBP-D3 peptide, nor were heightened or altered cellular or cytokine responses detected after repeated exposure to PilM1. The ability of PilM1 to stimulate protective immunity to a mucosal pathogen was also tested for the first time, revealing that the PilM1 control vaccine caused a significant reduction in S. aureus colonization of the nasal mucosa, masking any potential effect of the FnBP-D3 vaccine antigen.…”

“…The development of antibody responses to the major components of the PilVax platform (Spy0128 and the introduced peptide) has only been assessed in the sera and bronchoalveolar lavage of mice after a full series of vaccinations. 12 The backbone pilus protein Spy0128 stimulates robust antibody responses in mice, therefore, was used to determine how rapidly systemic antibody responses develop over time and whether intranasal vaccination with PilM1 can stimulate a mucosal antibody response at other sites such as the intestine. PilM1-vaccinated mice had significantly elevated serum immunoglobulin (Ig) G and IgA as well as mucosal (stool) IgA antibody responses to Spy0128 at all time points compared with phosphatebuffered saline (PBS)-vaccinated mice (P < 0.0001, Figure 2a).…”

“…[9][10][11] Foreign peptides have been successfully engineered into selected exposed loop regions of the major pilus protein FctA (Spy0128), which is assembled as repeating subunits to form the backbone of each individual pilus, providing the basis of a novel vaccine delivery platform referred to as PilVax. 12 It is estimated that at least one thousand copies of the foreign epitope project from the surface of every bacterium, providing a stable strategy for delivering large amounts of intact peptide antigen to the mucosa. 12 Vaccination of mice with a linear major histocompatibility complex class II binding peptide from ovalbumin (OVA 324-339 ) using the PilVax delivery platform stimulated both systemic and mucosal antibody responses to the introduced peptide.…”

“…12 It is estimated that at least one thousand copies of the foreign epitope project from the surface of every bacterium, providing a stable strategy for delivering large amounts of intact peptide antigen to the mucosa. 12 Vaccination of mice with a linear major histocompatibility complex class II binding peptide from ovalbumin (OVA 324-339 ) using the PilVax delivery platform stimulated both systemic and mucosal antibody responses to the introduced peptide. 12 A related L. lactis expression system, which relies on inserting vaccine candidate proteins in place of the endogenous protein expressed at the tip of S. pyogenes pili, has also demonstrated that this type of approach can stimulate both systemic and mucosal antibody response.…”

“…12 Vaccination of mice with a linear major histocompatibility complex class II binding peptide from ovalbumin (OVA 324-339 ) using the PilVax delivery platform stimulated both systemic and mucosal antibody responses to the introduced peptide. 12 A related L. lactis expression system, which relies on inserting vaccine candidate proteins in place of the endogenous protein expressed at the tip of S. pyogenes pili, has also demonstrated that this type of approach can stimulate both systemic and mucosal antibody response. 13,14 However, this strategy lacks the feature of peptide/protein amplification, as only one copy of the protein is expressed on each pilus.…”