13-valent pneumococcal conjugate vaccine immune sera protects against pneumococcal serotype 1, 3, and 5 bacteremia in a neonatal rat challenge model.

PCV7 was first licensed in the United States in 2000 based on clinical efficacy studies. Since the introduction, PCV7 has demonstrated protective effectiveness for each of the vaccine serotypes. More recently, PCV13 has been licensed in more than 60 countries based on serological noninferiority to PCV7 for the shared serotypes and noninferiority to the least immunogenic serotypes of PCV7 for the additional 6 serotypes in PCV13. To evaluate whether the functional antibody responses to serotypes 1, 3, and 5 were sufficient to protect animals challenged with virulent strains of these serotypes, rhesus macaques were immunized with three clinical doses of PCV13. The macaques mounted robust anti-capsular polysaccharide IgG and opsonophagocytic killing (OPA) responses to each serotype contained in the vaccine. Pooled pre-immunization sera and post-immunization serum pools were tested in a neonatal rat bacteremia model. Passive transfer of pooled post-immunization sera, but not pre-immunization sera, protected neonatal rats from lethal IP challenge with serotype 1, 3, or 5 strains. The functional activity of PCV13 immune sera against a virulent type 3 strain was further evaluated using sera from human children immunized with 4 doses of PCV7 or PCV13. Pooled sera from children immunized with PCV13, but not pooled sera from children immunized with PCV7, which does not contain the serotype 3 polysaccharide conjugate, protected neonatal rats from lethal IP challenge with a highly encapsulated and virulent serotype 3 strain. These data suggest that PCV13 will provide protection against pneumococcal serotype 1, 3, and 5 disease in human populations, even at relatively low OPA titers.

Reduction of nasal colonization of nontypeable Haemophilus influenzae following intranasal immunization with rLP4/rLP6/UspA2 proteins combined with aqueous formulation of RC529.

Nontypeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis are common causative agents of human mucosal infections. To formulate a mucosal vaccine against these pathogens, recombinant lipidated P4 (rLP4) and P6 (rLP6) proteins of NTHi and ubiquitous cell surface protein A (UspA) of M. catarrhalis were used for active immunization experiments in a mouse nasal challenge model. BALB/c mice were immunized intranasally with these proteins formulated with a chemically synthesized adjuvant, RC529 in an aqueous formulation (RC529-AF). Three weeks after the last immunization, these animals were challenged intranasally with NTHi strain SR7332.P1 and nasal colonization measured 3 days later. To determine local and systemic immune responses, bronchoalveolar washes (BAW) and sera were collected prior to NTHi challenge. The serum and mucosal samples were analyzed by ELISA for rLP4, rLP6 and UspA2 protein-specific IgG, IgG subclass and IgA antibody titers and bactericidal titers were determined against the TTA24 and 430-345 strains of M. catarrhalis. Results of these experiments show that these proteins combined with RC529-AF administered intranasally to mice elicited (1) significantly increased rLP4/rLP6/UspA2 protein-specific circulating IgG and IgA antibody responses; (2) local rLP4/rLP6/UspA2-specific IgA responses in the respiratory tract; and (3) more than a two log reduction of nasal colonization of NTHi strain SR7332 from the nasal tissues of mice. The serum IgG subclass distribution was predominantly IgG2a, representing a Th1 response. The antiserum also exhibited bactericidal activities to several strains of M. catarrhalis. These data indicate that intranasal immunization with rLP4/rLP6/UspA2 proteins combined with RC529-AF may be able to provide a way for inducing local mucosal immunity and for prevention of otitis media in children.

Immunization with Haemophilus influenzae Hap adhesin protects against nasopharyngeal colonization in experimental mice.

Nontypeable Haemophilus influenzae is a common cause of respiratory tract disease and initiates infection by colonizing the nasopharynx. The H. influenzae Hap adhesin is an autotransporter protein that was discovered because it promotes intimate interaction with human epithelial cells. Hap contains an extracellular domain called Hap(s) that has adhesive and protease activity and an outer membrane domain called Hap(beta) that serves to present Hap(s) on the surface of the cell. Hap(s) purified from nontypeable H. influenzae strain P860295 was used to immunize BALB/c mice intranasally. Immunization stimulated significant mucosal and serum anti-Hap(s) antibody titers, which were augmented by the addition of mutant cholera toxin (CT-E29H) as an adjuvant. Immunization was associated with a marked reduction in the density of nasopharyngeal colonization when mice were challenged with a heterologous strain of nontypeable H. influenzae. These results suggest that intranasal immunization with Hap formulated with CT-E29H may be a valuable vaccine strategy for the prevention of nontypeable H. influenzae disease.

The C-terminal fragment of the internal 110-kilodalton passenger domain of the Hap protein of nontypeable Haemophilus influenzae is a potential vaccine candidate.

Nontypeable Haemophilus influenzae is a major causative agent of bacterial otitis media in children. H. influenzae Hap autotransporter protein is an adhesin composed of an outer membrane Hapbeta region and a moiety of an extracellular internal 110-kDa passenger domain called Hap(S). The Hap(S) moiety promotes adherence to human epithelial cells and extracellular matrix proteins, and it also mediates bacterial aggregation and microcolony formation. A recent work (D. L. Fink, A. Z. Buscher, B. A. Green, P. Fernsten, and J. W. St. Geme, Cell. Microbiol. 5:175-186, 2003) demonstrated that Hap(S) adhesive activity resides within the C-terminal 311 amino acids (the cell binding domain) of the protein. In this study, we immunized mice subcutaneously with recombinant proteins corresponding to the C-terminal region of Hap(S) from H. influenzae strains N187, P860295, and TN106 and examined the resulting immune response. Antisera against the recombinant proteins from all three strains not only recognized native Hap(S) purified from strain P860295 but also inhibited H. influenzae Hap-mediated adherence to Chang epithelial cells. Furthermore, when mice immunized intranasally with recombinant protein plus mutant cholera toxin CT-E29H were challenged with strain TN106, they were protected against nasopharyngeal colonization. These observations demonstrate that the C-terminal region of Hap(S) is capable of eliciting cross-reacting antibodies that reduce nasopharyngeal colonization, suggesting utility as a vaccine antigen for the prevention of nontypeable H. influenzae diseases.