Adenovirus F protein as a delivery vehicle for botulinum B.

BACKGROUND: Immunization with recombinant carboxyl-terminal domain of the heavy chain (Hc domain) of botulinum neurotoxin (BoNT) stimulates protective immunity against native BoNT challenge. Most studies developing a botulism vaccine have focused on the whole Hc; however, since the principal protective epitopes are located within beta-trefoil domain (Hcbetatre), we hypothesize that immunization with the Hcbetatre domain is sufficient to confer protective immunity. In addition, enhancing its uptake subsequent to nasal delivery prompted development of an alternative vaccine strategy, and we hypothesize that the addition of targeting moiety adenovirus 2 fiber protein (Ad2F) may enhance such uptake during vaccination. RESULTS: The Hcbetatre serotype B immunogen was genetically fused to Ad2F (Hcbetatre/B-Ad2F), and its immunogenicity was tested in mice. In combination with the mucosal adjuvant, cholera toxin (CT), enhanced mucosal IgA and serum IgG Ab titers were induced by nasal Hcbetatre-Ad2F relative to Hcbetatre alone; however, similar Ab titers were obtained upon intramuscular immunization. These BoNT/B-specific Abs induced by nasal immunization were generally supported in large part by Th2 cells, as opposed to Hcbetatre-immunized mice that showed more mixed Th1 and Th2 cells. Using a mouse neutralization assay, sera from animals immunized with Hcbetatre and Hcbetatre-Ad2F protected mice against 2.0 LD50. CONCLUSION: These results demonstrate that Hcbetatre-based immunogens are highly immunogenic, especially when genetically fused to Ad2F, and Ad2F can be exploited as a vaccine delivery platform to the mucosa.

Genetic signatures in the envelope glycoproteins of HIV-1 that associate with broadly neutralizing antibodies.

A steady increase in knowledge of the molecular and antigenic structure of the gp120 and gp41 HIV-1 envelope glycoproteins (Env) is yielding important new insights for vaccine design, but it has been difficult to translate this information to an immunogen that elicits broadly neutralizing antibodies. To help bridge this gap, we used phylogenetically corrected statistical methods to identify amino acid signature patterns in Envs derived from people who have made potently neutralizing antibodies, with the hypothesis that these Envs may share common features that would be useful for incorporation in a vaccine immunogen. Before attempting this, essentially as a control, we explored the utility of our computational methods for defining signatures of complex neutralization phenotypes by analyzing Env sequences from 251 clonal viruses that were differentially sensitive to neutralization by the well-characterized gp120-specific monoclonal antibody, b12. We identified ten b12-neutralization signatures, including seven either in the b12-binding surface of gp120 or in the V2 region of gp120 that have been previously shown to impact b12 sensitivity. A simple algorithm based on the b12 signature pattern was predictive of b12 sensitivity/resistance in an additional blinded panel of 57 viruses. Upon obtaining these reassuring outcomes, we went on to apply these same computational methods to define signature patterns in Env from HIV-1 infected individuals who had potent, broadly neutralizing responses. We analyzed a checkerboard-style neutralization dataset with sera from 69 HIV-1-infected individuals tested against a panel of 25 different Envs. Distinct clusters of sera with high and low neutralization potencies were identified. Six signature positions in Env sequences obtained from the 69 samples were found to be strongly associated with either the high or low potency responses. Five sites were in the CD4-induced coreceptor binding site of gp120, suggesting an important role for this region in the elicitation of broadly neutralizing antibody responses against HIV-1.