Generation of microglia specific reagents from phage displayed peptide libraries.

The present report concerns the generation of specific markers and the establishment of a selection procedure for microglia specific molecules from phage displayed peptide libraries. Negative selection against a mouse monocytic cell line (IC-21) and positive selection against primary mouse microglia was combined in the selection procedures using a mixture of two random peptide libraries displayed on phage. In a first set of experiments, one clone was selected that bound microglia and IC-21 cells to equal extent, and three clones that bound to unsorted primary microglia to substantially higher levels than to IC-21 cells. In the second series of experiments, microglia and IC-21 cells were mixed and CD45-positive microglia cells were collected using a FACS sorter. From the latter selection series, three clones were found that preferentially bound to microglia cells. The binding of one of the six selected microglia specific phage clones, clone V-1:19, was competed/inhibited in experiments using soluble synthetic peptides corresponding to the binding motif of the phage clone. The specific inhibition to microglia cells by this synthetic peptide was effective in the concentration range of 0.5-20 microM. The preferential binding of clone V-1:19 to microglia like cells was further demonstrated by staining a panel of cell lines and purified primary mouse microglia.

Human neutralizing human immunodeficiency virus type 2-specific Fab molecules generated by phage display.

A panel of human immunodeficiency virus type 2 (HIV-2)-neutralizing, recombinant Fab fragments was generated by using the phage display technique. The combinatorial library was derived from an asymptomatic, HIV-2-seropositive individual and constructed on the surface of filamentous phage by using the pComb3 phagemid vector and then screened against native HIV-2 envelope glycoprotein (gp125). Ten of 30 Fab fragments generated displayed strong reactivity in an ELISA and were therefore selected for further study. Six of these possessed neutralizing capacity, with titres varying from 20 to 80 against the homologous HIV-2 strain, and one also had a weak neutralizing capacity against a heterologous HIV-2 isolate, K135. Sequencing of the heavy chain CDR3 regions showed that the gp125-specific Fabs represented individual clones. These reagents may be useful for studies on the conformational structures of the HIV-2 envelope antigens and their immunogenicity, which may help in vaccine design. Furthermore, the cloned Fab genes may be transformed into whole IgG for eukaryotic expression, and as such used for therapeutic and immunoprophylactic studies in HIV-2-infected macaques and, possibly, for human immunoprophylaxis against HIV-2.