The mucosal antibody repertoire of the cervical mucosa in commercial sex workers from Nairobi, Kenya, who are highly sexually exposed to human immune deficiency virus type-1 (HIV-1) but remain persistently IgG seronegative (HEPS), may represent a novel source of broadly neutralizing monoclonal antibodies (mAbs) against HIV-1. Mucosal IgA specific for HIV-1 envelope (Env) subunit gp41 has been suggested as a correlate of protection in HEPS individuals. The in depth studies at both the gene and function level required to confirm their role in HIV-1 resistance are possible only using recombinant monoclonal IgAs. Human mAbs have traditionally been selected from libraries displayed on the surface of microorganisms (phage, yeast). However, due to inherent limitations, such techniques may not be optimal for isolating such rare mAbs from a pool of cervical B cells. We have developed an antibody selection system based on surface display on mammalian cells and used this technology to isolate four novel monoclonal antibodies, against linear epitopes on gp41, from the IgA repertoire of the cervical mucosa in Kenyan HEPS. Furthermore, three of the four mAbs were shown to bind with surface expressed consensus clade B and clade C Env on mammalian cells. Characterization of the variable region cDNA of the two strongest binding mAbs reveals extensive somatic mutations with a bias of replacement mutations clustering in the complementary determining regions (CDR) indicating antigen-driven affinity maturation had occurred. Affinity matured monoclonal IgAs, such as these, may play a role in the identification of new, vulnerable epitopes on HIV-1, or act as a component in a topical microbicide.

The mucosal antibody repertoire of the cervical mucosa in commercial sex workers from Nairobi, Kenya, who are highly sexually exposed to human immune deficiency virus type-1 (HIV-1) but remain persistently IgG seronegative (HEPS), may represent a novel source of broadly neutralizing monoclonal antibodies (mAbs) against HIV-1. Mucosal IgA specific for HIV-1 envelope (Env) subunit gp41 has been suggested as a correlate of protection in HEPS individuals. The in depth studies at both the gene and function level required to confirm their role in HIV-1 resistance are possible only using recombinant monoclonal IgAs. Human mAbs have traditionally been selected from libraries displayed on the surface of microorganisms (phage, yeast). However, due to inherent limitations, such techniques may not be optimal for isolating such rare mAbs from a pool of cervical B cells. We have developed an antibody selection system based on surface display on mammalian cells and used this technology to isolate four novel monoclonal antibodies, against linear epitopes on gp41, from the IgA repertoire of the cervical mucosa in Kenyan HEPS. Furthermore, three of the four mAbs were shown to bind with surface expressed consensus clade B and clade C Env on mammalian cells. Characterization of the variable region cDNA of the two strongest binding mAbs reveals extensive somatic mutations with a bias of replacement mutations clustering in the complementary determining regions (CDR) indicating antigen-driven affinity maturation had occurred. Affinity matured monoclonal IgAs, such as these, may play a role in the identification of new, vulnerable epitopes on HIV-1, or act as a component in a topical microbicide.

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