Coated cross-species antibodies by mannosamine-biotin adduct confer protection against snake venom without eliciting humoral immune response

The effect of haptens on protein-carrier immunogenicity

The immune response against hapten is T-cell-dependent, and so requires the uptake, processing and presentation of peptides on MHC class II molecules by antigen-presenting cells to the specific T cell. Some haptens, following conjugation to the available free amines on the surface of the carrier protein, can reduce its immunogenicity. The purpose of this study was to explore the mechanism by which this occurs. Four proteins were tested as carriers and six molecules were used as haptens. The immune response to the carrier proteins was reduced > 100-fold by some of the haptens (termed carrier immunogenicity reducing haptens--CIRH), whereas other haptens did not influence the protein immunogenicity (carrier immunogenicity non-reducing haptens--nCIRH). Conjugation of the protein to a CIRH affected protein degradation by lysosomal cathepsins, leading to the generation of peptides that differ in length and sequence from those derived from the same native protein or that protein modified with nCIRH. Injection of CIRH-conjugated protein into mice induced an increase in the population of regulatory T cells. The results of this study provide a putative mechanism of action for the reduction of immune response to haptenated proteins.

Modulation of innate immune responses by influenza-specific ovine polyclonal antibodies used for prophylaxis

In the event of a novel influenza A virus pandemic, prophylaxis mediated by antibodies provides an adjunct control option to vaccines and antivirals. This strategy is particularly pertinent to unvaccinated populations at risk during the lag time to produce and distribute an effective vaccine. Therefore, development of effective prophylactic therapies is of high importance. Although previous approaches have used systemic delivery of monoclonal antibodies or convalescent sera, available supply is a serious limitation. Here, we have investigated intranasal delivery of influenza-specific ovine polyclonal IgG antibodies for their efficacy against homologous influenza virus challenge in a mouse model. Both influenza-specific IgG and F(ab')2 reduced clinical scores, body weight loss and lung viral loads in mice treated 1 hour before virus exposure. Full protection from disease was also observed when antibody was delivered up to 3 days prior to virus infection. Furthermore, effective prophylaxis was independent of a strong innate immune response. This strategy presents a further option for prophylactic intervention against influenza A virus using ruminants to generate a bulk supply that could potentially be used in a pandemic setting, to slow virus transmission and reduce morbidity associated with a high cytokine phenotype.