A large 1.29 x 10(11) antibody fragment library, based upon variable (V) genes isolated from human B-cells from 160 donors has been constructed and its performance measured against a panel of 28 different clinically relevant antigens. Over 5000 different target-specific antibodies were isolated to the 28 antigens with 3340 identified as modulating the biological function (e.g. antagonism, agonism) of the target antigen. This represents an average of approximately 120 different functionally active antibodies per target. Analysis of a sample of >800 antibodies from the unselected library indicates V gene usage is representative of the human immune system with no strong bias towards any particular V(H)-V(L) pairing. Germline diversity is broad with 45/49 functional V(H) germlines and 28/30 V(lambda) and 30/35 V(kappa) light-chain germlines represented in the sample. The number of functional V(H) germlines and V(kappa) light-chain germlines present is increased to 48/49 and 31/35, respectively, when selected V gene usage is included in the analysis. However, following selection on the antigen panel, V(H)1-V(lambda)1 germline family pairings are preferentially enriched and represent a remarkable 25% of the antigen-specific selected repertoire.

Fusarium Head Blight (FHB) is the number one floral disease of cereals and poses a serious health hazard by contaminating grain with the harmful mycotoxin deoxynivalenol (DON). Fungi adapt to fluctuations in their environment, coordinating development and metabolism accordingly. G-protein coupled receptors (GPCRs) communicate changes in the environment to intracellular G-proteins that direct the appropriate biological response, suggesting that fungal GPCR signalling may be key to virulence. Here we describe the expansion of non-classical GPCRs in the FHB causing pathogen, Fusarium graminearum , and show that class X receptors are highly expressed during wheat infection. We identify class X receptors that are required for FHB disease on wheat, and show that the absence of a GPCR can cause an enhanced host response that restricts the progression of infection. Specific receptor sub-domains are required for virulence. These non-classical receptors physically interact with intracellular G-proteins and are therefore bona fide GPCRs. Disrupting a class X receptor is shown to dysregulate the transcriptional coordination of virulence traits during infection. This amounts to enhanced wheat defensive responses, including chitinase and plant cell wall biosynthesis, resulting in apoplastic and vascular occlusions that impede infection. Our results show that GPCR signalling is important to FHB disease establishment.