Combining phage display with SMRTbell next-generation sequencing for the rapid discovery of functional scFv fragments.

Phage display technology in combination with next-generation sequencing (NGS) currently is a state-of-the-art method for the enrichment and isolation of monoclonal antibodies from diverse libraries. However, the current NGS methods employed for sequencing phage display libraries are limited by the short contiguous read lengths associated with second-generation sequencing platforms. Consequently, the identification of antibody sequences has conventionally been restricted to individual antibody domains or to the analysis of single domain binding moieties such as camelid VHH or cartilaginous fish IgNAR antibodies. In this study, we report the application of third-generation sequencing to address this limitation. We used single molecule real time (SMRT) sequencing coupled with hairpin adaptor loop ligation to facilitate the accurate interrogation of full-length single-chain Fv (scFv) libraries. Our method facilitated the rapid isolation and testing of scFv antibodies enriched from phage display libraries within days following panning. Two libraries against CD160 and CD123 were panned and monitored by NGS. Analysis of NGS antibody data sets led to the isolation of several functional scFv antibodies that were not identified by conventional panning and screening strategies. Our approach, which combines phage display selection of immune libraries with the full-length interrogation of scFv fragments, is an easy method to discover functional antibodies, with a range of affinities and biophysical characteristics.

The 5' untranslated mRNA region base content can greatly affect translation initiation in the absence of secondary structures in Prevotella bryantii TC1-1.

It has become clear lately that many bacteria and even whole bacterial phyla do not use the classical Shine-Dalgarno sequence mediated pathway of protein translation initiation. The prominent phylum Bacteroidetes is one of them, and this was shown not only using bioinformatic but also functional reporter gene studies in its representative Prevotella bryantii. The latter studies revealed much higher sensitivity toward secondary structures in 5(') untranslated mRNA regions (5(') UTRs) during translation initiation compared to Escherichia coli. It was proposed that in the absence of Shine-Dalgarno sequence interaction the key elements enabling translation initiation are local absence of secondary structures in 5(') UTRs, and the ribosomal protein S1 which binds to mRNA. Here, we evaluate the 5(') UTRs devoid of secondary structures but containing divergent nucleotide compositions in P. bryantii reporter assay. We show that base composition profoundly affects the amount of the reporter synthesized, and further that these amounts were in agreement with S1 protein binding affinity for adenine/uracil bases in mRNA. This is the first, though indirect, clue that S1 is actually involved in translation initiation in Bacteroidetes and adds the second layer of control beside mRNA secondary structure affecting translation initiation in this phylum.