Immunological aspects of antibody formation against recombinant human therapeutics

Abstract

With about 200 new products in the pipeline, recombinant human (rh) therapeutics are becoming the most dominant class of drugs. One of the reasons to create rh therapeutics was to avoid recognition by the immune system due to foreign origin. Nevertheless, rh therapeutics induced formation of anti-drug antibodies. Aggregation of the therapeutic protein became a major concern, directing the focus on an ancient mechanism of the immune system to recognize repetitive epitopes on pathogens and activation of a non-classical T-cell – B-cell pathway leading to a fast and efficient immune response. It was hypothesized that aggregated rh therapeutics mimic such repetitive epitope carrying pathogens, named T cell independent type 2 antigens. The thesis entitles ‘Immunological aspects of antibody formation against recombinant human therapeutics’ investigated the immunological mechanisms triggered after administration of aggregated rh therapeutics in transgenic mice immune tolerant for the therapeutic of interest. A three step approach was used: (I) Memory formation after administration of aggregated rh therapeutics?, (II) Is the response T cell independent?, (III) Do Marginal Zone B cells influence the immune response against rh therapeutics?. Two model therapeutics were used: (1) rh interferon beta, and (2) recombinant human interferon alpha. Both models showed the absence of memory formation after initial challenge and boost with both aggregated and non-aggregated rh drugs. In addition, a lack of neutralizing antibodies was observed. Though memory was absent, animals had an abundant pool of isotype switched antibodies, a sign for T cell dependency. And indeed, depletion of CD4+ T cells led to a complete abolishment of the antibody formation against aggregated therapeutic. Lastly, it could be shown that the depletion of marginal zone B cells influence the response against rh therapeutics. In conclusions, it was shown that the immune response directed against aggregated rh therapeutics is neither comparable to a classical nor to a T cell independent type 2 antigen. In addition, the presence of naturally occurring antibodies in human blood samples was investigated. It is hypothesized that patients having natural occurring antibodies against a rh therapeutic may be more susceptible to formation of anti-drug antibodies when treated with the rh therapeutic. The presence of naturally occurring antibodies against interferon alpha, beta and gamma and bone morphogenetic proteins 2 and 7 could be found in around 2% of individuals (n=400). Their influence on the immunogenicity of rh therapeutics need to be further explored.