Antibody responses against flagellin in mice orally immunized with attenuated Salmonella vaccine strains.

Salmonella fIagellin has been repeatedly used as a carrier for heterologous peptide epitopes either as a parenterally delivered purified antigen or as a parenterally/orally-administered, flagellated, live, attenuated vaccine. Nonetheless, the ability to induce specific antibody responses against the flagellin moiety, fused or not with heterologous peptide, has not usually been reported in mice orally inoculated with a live, attenuated, flagellated Salmonella strain. In this work we evaluated the immunogenicity of flagellin in mice following oral inoculation with an aroA Salmonella enterica serovar Dublin SL5929 strain, which expressed plasmid-encoded recombinant hybrid flagellin fused to the CTP3 epitope (amino acids 50-64) of cholera toxin B-subunit. In contrast to parenterally immunized mice, no significant CTP3- or flagellin-specific antibody responses either in sera (IgG) or feces (IgA) were detected following repeated oral delivery of the recombinant Salmonella strain to C57BL/6 mice. Similarly, flagellin-specific antibody responses were also not detected in mice immunized with strain SL5930, which expressed a nonhybrid flagellin. The lack of flagellin-specific antibody responses was not associated with deficient Peyer patch colonization or spleen invasion. Moreover, stabilization of the flagellin-coding gene by integration into the host chromosome did not significantly improve flagellin-specific antibody responses following administration by the oral route. Taken together, these results suggest that flagellin does not represent an efficient peptide carrier for activation of antibody responses in mice orally immunized with live, attenuated Salmonella strains.

A randomized 'blinded' comparison of two doses of antivenom in the treatment of Bothrops envenoming in São Paulo, Brazil.

An earlier study in São Paulo state suggested that the dose for patients with mild or moderate envenoming by Bothrops snakes (mainly Bothrops jararaca) could be effectively decreased to 4 ampoules (40 mL) of Brazilian Brothrops polyspecific antivenom. The present 'blinded' study examined the lowest dose studied in the first trial (equivalent to 4 x 10 mL ampoules) and half that dose of antivenom (equivalent to 2 x 10 mL ampoules) in 2 similar groups of 170 patients who were comparable in all respects before treatment. The majority of patients showed rapid clinical improvement after treatment with either dose regimen and rapid restoration of blood coagulability and cessation of bleeding. There was no apparent difference between the 2 groups of patients in any respect. The study confirmed that, in such patients, the dose of antivenom can be decreased from 4 ampoules to 2 ampoules without reduction of therapeutic efficacy, and it is highly likely that this reduction will result in a decrease of early anaphylactic reactions caused by the antivenom.