Safety and immunogenicity of 26-valent group a streptococcus vaccine in healthy adult volunteers.

BACKGROUND: Group A streptococcus (GAS) causes illness ranging from uncomplicated pharyngitis to life-threatening necrotizing fasciitis, toxic shock, and rheumatic fever. Attempts to develop an M protein-based vaccine have been hindered by the fact that some M proteins elicit both protective antibodies and antibodies that cross-react with human tissues. New molecular techniques have allowed the previous obstacles to be largely overcome. METHODS: The vaccine is comprised of 4 recombinant proteins adsorbed to aluminum hydroxide that contain N-terminal peptides from streptococcal protective antigen and M proteins of 26 common pharyngitis, invasive, and/or rheumatogenic serotypes. Thirty healthy adult subjects received intramuscular 26-valent GAS vaccine (400 microg) at 0, 1, and 4 months, with clinical and laboratory follow-up for safety and immunogenicity using assays for tissue cross-reactive antibodies, type-specific M antibodies to 27 vaccine antigens, and functional (opsonization) activity of M protein antibodies. RESULTS: The incidence of local reactogenicity was similar to that for other aluminum hydroxide-adsorbed vaccines in adults. No subject developed evidence of rheumatogenicity or nephritogenicity, and no induction of human tissue-reactive antibodies was detected. Overall, 26 of 27 antigenic peptides evoked a >4-fold increase in the geometric mean antibody titer over baseline. The mean log2 fold-increase in serum antibody titer (+/- standard error of the mean) for all 27 antigens was 3.67 +/- 0.21. A significant mean log2 reduction in streptococcal bacterial counts in serum samples obtained after immunization was seen in opsonization assays for all M serotypes. CONCLUSIONS: On the basis of epidemiological data demonstrating that the majority of cases of pharyngitis, necrotizing fasciitis, and other invasive streptococcal infections are caused by a limited number of serotypes, this 26-valent vaccine could have significant impact on the overall burden of streptococcal disease.

Safety and immunogenicity of a recombinant multivalent group a streptococcal vaccine in healthy adults: phase 1 trial.

CONTEXT: Group A streptococcal infections and their sequelae represent a global health problem. Recent advances have allowed previous obstacles associated with group A streptococcal vaccine development to be overcome. OBJECTIVE: To preliminarily evaluate the safety and immunogenicity of ascending doses of a recombinant fusion peptide group A streptococcal vaccine containing N-terminal M protein fragments from serotypes 1, 3, 5, 6, 19, and 24 in healthy volunteers. DESIGN, SETTING, AND PARTICIPANTS: An open-label, uncontrolled, dose-ascending phase 1 vaccine trial of 28 healthy adult volunteers aged 18 to 50 years recruited from the metropolitan area of Baltimore, Md, between October 5, 1999, and February 26, 2003, using newspaper advertisements and posted fliers, and evaluated in the outpatient facility of the Center for Vaccine Development. INTERVENTIONS: Each volunteer received 3 spaced intramuscular injections of 50 microg (n = 8), 100 micro g (n = 10), or 200 microg (n = 10) of hexavalent group A streptococcal vaccine formulated with aluminum hydroxide into the deltoid muscle of alternating arms. MAIN OUTCOME MEASURES: Assessments of clinical safety, including elicitation of antibodies that cross-react with host tissues, and immunogenicity as measured by enzyme-linked immunosorbent assay (ELISA) and assays of opsonophagocytic- and bactericidal-antibody responses. RESULTS: One year of intensive follow-up revealed the vaccine to be well tolerated. There was no evidence of tissue cross-reactive antibodies or immunological complications. At the highest (200 microg) dose, vaccination elicited significant increases in geometric mean antibody levels to all 6 component M antigens by ELISA (all P<.01) and to 5 of 6 M types in the opsonophagocytosis assay (all P<.05). In addition, postvaccination increases in serum bactericidal activity of at least 30% were observed in 31 (55%) of 56 assays. CONCLUSION: These results provide the first evidence in humans that a hybrid fusion protein is a feasible strategy for evoking type-specific opsonic antibodies against multiple serotypes of group A streptococcus without eliciting antibodies that cross-react with host tissues, which represents a critical step in the development of a vaccine.

Immunogenicity of a 26-valent group A streptococcal vaccine.

A multivalent vaccine containing amino-terminal M protein fragments from 26 different serotypes of group A streptococci was constructed by recombinant techniques. The vaccine consisted of four different recombinant proteins that were formulated with alum to contain 400 microg of protein per dose. Rabbits were immunized via the intramuscular route at 0, 4, and 16 weeks. Immune sera were assayed for the presence of type-specific antibodies against the individual recombinant M peptides by enzyme-linked immunosorbent assay and for opsonic antibodies by in vitro opsonization tests and indirect bactericidal tests. The 26-valent vaccine was highly immunogenic and elicited fourfold or greater increases in antibody levels against 25 of the 26 serotypes represented in the vaccine. The immune sera were broadly opsonic and were bactericidal against the majority of the 26 different serotypes. Importantly, none of the immune sera cross-reacted with human tissues. Our results indicate that type-specific, protective M protein epitopes can be incorporated into complex, multivalent vaccines designed to elicit broadly protective opsonic antibodies in the absence of tissue-cross-reactive antibodies.

Intranasal immunization with multivalent group A streptococcal vaccines protects mice against intranasal challenge infections.

We have previously shown that a hexavalent group A streptococcal M protein-based vaccine evoked bactericidal antibodies after intramuscular injection. In the present study, we show that the hexavalent vaccine formulated with several different mucosal adjuvants and delivered intranasally induced serum and salivary antibodies that protected mice from intranasal challenge infections with virulent group A streptococci. The hexavalent vaccine was formulated with liposomes with or without monophosphorylated lipid A (MPL), cholera toxin B subunit with or without holotoxin, or proteosomes from Neisseria meningitidis outer membrane proteins complexed with lipopolysaccharide from Shigella flexneri. Intranasal immunization with the hexavalent vaccine mixed with these adjuvants resulted in significant levels of antibodies in serum 2 weeks after the final dose. Mean serum antibody titers were equivalent in all groups of mice except those that were immunized with hexavalent protein plus liposomes without MPL, which were significantly lower. Salivary antibodies were also detected in mice that received the vaccine formulated with the four strongest adjuvants. T-cell proliferative assays and cytokine assays using lymphocytes from cervical lymph nodes and spleens from mice immunized with the hexavalent vaccine formulated with proteosomes indicated the presence of hexavalent protein-specific T cells and a Th1-weighted mixed Th1-Th2 cytokine profile. Intranasal immunization with adjuvanted formulations of the hexavalent vaccine resulted in significant levels of protection (80 to 100%) following intranasal challenge infections with type 24 group A streptococci. Our results indicate that intranasal delivery of adjuvanted multivalent M protein vaccines induces protective antibody responses and may provide an alternative to parenteral vaccine formulations.