Technologies for Proteome-Wide Discovery of Extracellular Host-Pathogen Interactions

Martinez-Martin, Nadia

PPIs than most biochemical approaches, these biophysical techniques have not been exploited for large-scale ePPI discovery, possibly due to the low throughput of the available instrumentation and the overall difficulties for generation of the relevant protein libraries. These studies, among many others, have demonstrated the power of the classical biochemical and biophysical techniques for detection of host-pathogen interactions. Nevertheless, these approaches require previous knowledge of the pathogen-encoded proteins responsible for binding and the ability to produce such proteins as recombinant reagents, which may be challenging, as exemplified by the production of hCMV entry complexes [21, 66] . Alternative methods have been utilized in those cases where there is no previous knowledge of the pathogen proteins required for interaction with the host cells. In this regard, the screening of large collections of monoclonal antibodies raised against membrane proteins has proven particularly useful to identify receptors that mediate viral entry. Back in the early 80s, the discovery of CD4 as an entry receptor for the human immunodeficiency virus type 1 (HIV) significantly impacted our understanding of viral pathogenesis and subsequent development of therapeutics [23, 24] . In this case, the well-defined tropism of the virus determined the choice of over 100 antibodies directed against human leukocyte differentiation antigens, of which only antibodies that recognized the surface receptor CD4 blocked viral infection [23] . It is worth noting that similar monoclonal antibody screens have also been utilized for unbiased characterization of viral blockers. For example, Colonno and colleagues performed a screen of more than 2,000 hybridomas from mice immunized with preparations of plasma membranes from human cells and were able to find one antibody that blocked rhinovirus binding to its cell surface receptor [25] , identified as the intercellular cell adhesion molecule 1 (ICAM-1) in subsequent studies [26] .