Active and Passive Intranasal Immunizations with Streptococcal Surface Protein C5a Peptidase Prevent Infection of Murine Nasal Mucosa-Associated Lymphoid Tissue, a Functional Homologue of Human Tonsils

Abstract

C5a peptidase, also called SCPA (surface-bound C5a peptidase), is a surface-bound protein on group A streptococci (GAS), etiologic agents for a variety of human diseases including pharyngitis, impetigo, toxic shock, and necrotizing fasciitis, as well as the postinfection sequelae rheumatic fever and rheumatic heart disease. This protein is highly conserved among different serotypes and is also expressed in human isolates of group B, C, and G streptococci. Human tonsils are the primary reservoirs for GAS, maintaining endemic disease across the globe. We recently reported that GAS preferentially target nasal mucosa-associated lymphoid tissue (NALT) in mice, a tissue functionally analogous to human tonsils. Experiments using a C5a peptidase loss-of-function mutant and an intranasal infection model showed that this protease is required for efficient colonization of NALT. An effective vaccine should prevent infection of this secondary lymphoid tissue; therefore, the potential of anti-SCPA antibodies to protect against streptococcal infection of NALT was investigated. Experiments showed that GAS colonization of NALT was significantly reduced following intranasal immunization of mice with recombinant SCPA protein administered alone or with cholera toxin, whereas a high degree of GAS colonization of NALT was observed in control mice immunized with phosphate-buffered saline only. Moreover, administration of anti-SCPA serum by the intranasal route protected mice against streptococcal infection. These results suggest that intranasal immunization with SCPA would prevent colonization and infection of human tonsils, thereby eliminating potential reservoirs that maintain endemic disease.

Human Serum Induces Streptococcal C5a Peptidase Expression

“…Genetic polymorphisms alter the functional activity of C5a peptidase (5) but do not affect its ability to bind fibronectin (40). Overall, its conserved nucleotide sequence in several ␤-hemolytic streptococcal species, its ubiquitous expression, and its surface localization make it a good vaccine candidate for S. agalactiae, as well as S. pyogenes, infections (10,21,29,32).…”

Group A Streptococcal Vaccine Candidates: Potential for the Development of a Human Vaccine

“…Mucosal immunization stimulates both a humoral immune response in blood and mucosal secretions (Batzloff et al 2005Bessen and Fischetti 1988;Bronze et al 1992;Hall et al 2004;Ji et al 1997;Kawabata et al 2001;Park and Cleary 2005;Guzmán et al 1999;Schulze et al 2001Schulze et al , 2006Yokoyama and Harabuchi 2002;Olive et al 2007). Protection against GAS infection as a result of mucosal immunization is most likely due to prevention of colonization by secretory IgA and IgG at the site of infection.…”

“…Passive immunization experiments have also been used to demonstrate passive protection at the mucosa. Mouse antiserum raised by intranasal immunization with C5a peptidase when administered to mice intranasally has been shown to protect against pharyngeal colonization by GAS (Park and Cleary 2005). Passive immunization demonstrates the capacity of antigen specific antibodies to protect against GAS infection, and may also provide an alternate treatment for invasive GAS diseases (Basma et al 1998;Kaul et al 1999).…”

“…Most murine models to evaluate mucosal immunity in response to GAS antigens have utilized intranasal or perioral immunization in the presence of the non-toxic B subunit of cholera toxin (CTB) Fischetti 1988, 1990;Bronze et al 1992;Olive et al 2002;Hall et al 2004;Schulze et al , 2006Batzloff et al 2006;Kawabata et al 2001;Park and Cleary 2005;Guzmán et al 1999;Yokoyama and Harabuchi 2002). While CTB is not approved for human use it is one of the most commonly employed adjuvants for assessing vaccine potential at mucosal surfaces in animal models.…”

“…Pharyngeal colonization rates are measured by determining the colony forming units present in the pharynx from as early as 20 h post infection up to 10-15 days post intranasal or perioral challenge either by throat swab (Batzloff et al 2005;Fischetti 1988, 1990;Bronze et al 1992Bronze et al , 2006Ji et al 1997) or by homogenizing mouse snout samples ). Alternatively, Park and Cleary (2005) visualized and quantified pharyngeal colonization by utilizing luciferase expressing GAS strains and a chargecoupled device camera system at both 24 and 48 h post infection.…”