Priming HIV-1 broadly neutralizing antibody precursors in human Ig loci transgenic mice.

A major obstacle to a broadly neutralizing antibody (bnAb)-based HIV vaccine is the activation of appropriate B cell precursors. Germline-targeting immunogens must be capable of priming rare bnAb precursors in the physiological setting. We tested the ability of the VRC01-class bnAb germline-targeting immunogen eOD-GT8 60mer (60-subunit self-assembling nanoparticle) to activate appropriate precursors in mice transgenic for human immunoglobulin (Ig) loci. Despite an average frequency of, at most, about one VRC01-class precursor per mouse, we found that at least 29% of singly immunized mice produced a VRC01-class memory response, suggesting that priming generally succeeded when at least one precursor was present. The results demonstrate the feasibility of using germline targeting to prime specific and exceedingly rare bnAb-precursor B cells within a humanlike repertoire.

Complete humanization of the mouse immunoglobulin loci enables efficient therapeutic antibody discovery.

If immunized with an antigen of interest, transgenic mice with large portions of unrearranged human immunoglobulin loci can produce fully human antigen-specific antibodies; several such antibodies are in clinical use. However, technical limitations inherent to conventional transgenic technology and sequence divergence between the human and mouse immunoglobulin constant regions limit the utility of these mice. Here, using repetitive cycles of genome engineering in embryonic stem cells, we have inserted the entire human immunoglobulin variable-gene repertoire (2.7 Mb) into the mouse genome, leaving the mouse constant regions intact. These transgenic mice are viable and fertile, with an immune system resembling that of wild-type mice. Antigen immunization results in production of high-affinity antibodies with long human-like complementarity-determining region 3 (CDR3H), broad epitope coverage and strong signatures of somatic hypermutation. These mice provide a robust system for the discovery of therapeutic human monoclonal antibodies; as a surrogate readout of the human antibody response, they may also aid vaccine design efforts.

Mutation of a novel gene results in abnormal development of spermatid flagella, loss of intermale aggression and reduced body fat in mice.

ROSA22 male mice are sterile due to a recessive gene-trap mutation that affects development of the spermatid flagellum. The defect involves the flagellar axoneme, which becomes unstable around the time of its assembly. Despite a subsequent complete failure in flagellar assembly, development of the spermatid head appears normal and the spermatid head is released at the correct stage in spermatogenesis. The mutation is pleiotropic. Although ROSA22 homozygote males have normal levels of circulating testosterone and display normal mating behavior, they do not exhibit intermale aggressive behavior and have reduced body fat. The mutated gene (Gtrgeo22) maps to mouse chromosome 10 and is closely flanked by two known genes, Madcam1 and Cdc34. Ribonuclease protection analysis indicates that expression of the flanking genes is unaffected by the mutation. Gtrgeo22 is expressed at low levels in epithelial cells in several tissues, as well as in testis and brain. Analysis of the peptide coding sequence suggests that Gtrgeo22 encodes a novel transmembrane protein, which contains dileucine and tyrosine-based motifs involved in intracellular sorting of transmembrane proteins. Analysis of the Gtrgeo22 gene product should provide novel insight into the molecular basis for intermale aggression and sperm flagellar development.