While the induction of a neutralizing antibody response against HIV remains a daunting goal, data from both natural infection and vaccine-induced immune responses suggest that it may be possible to induce antibodies with enhanced Fc effector activity and improved antiviral control via vaccination. However, the specific features of naturally induced HIV-specific antibodies that allow for the potent recruitment of antiviral activity and the means by which these functions are regulated are poorly defined. Because antibody effector functions are critically dependent on antibody Fc domain glycosylation, we aimed to define the natural glycoforms associated with robust Fc-mediated antiviral activity. We demonstrate that spontaneous control of HIV and improved antiviral activity are associated with a dramatic shift in the global antibody-glycosylation profile toward agalactosylated glycoforms. HIV-specific antibodies exhibited an even greater frequency of agalactosylated, afucosylated, and asialylated glycans. These glycoforms were associated with enhanced Fc-mediated reduction of viral replication and enhanced Fc receptor binding and were consistent with transcriptional profiling of glycosyltransferases in peripheral B cells. These data suggest that B cell programs tune antibody glycosylation actively in an antigen-specific manner, potentially contributing to antiviral control during HIV infection.

IgG molecules are widely used as therapeutic agents either in the form of intact Abs or as Fc fusion proteins. Although efficient binding of the IgG Fc fragment to cellular FcγRs may be essential to achieve a high cytolytic activity, it may be advantageous for other applications to limit or abolish this interaction. Genetic or biochemical approaches have been used to generate these non–FcγR-binding IgG variants. By using soluble versions of FcγRs and monomeric versions of these altered IgG molecules, it was demonstrated that these IgG variants no longer bind to FcγRs. Importantly, however, these assays do not reflect the physiologic interaction of IgG with low-affinity cellular FcγRs occurring in the form of multimeric immune complexes. In this study, we investigated how the size of an immune complex can affect the interaction of normal and various versions of potentially non–FcγR-binding IgG variants with cellular FcγRs. We show that neither the D265A mutation nor EndoS treatment resulting in IgG molecules with only one N-acetylglucosamine and a fucose residue was fully able to abolish the interaction of all IgG subclasses with cellular FcγRs, suggesting that IgG subclass–specific strategies are essential to fully interfere with human FcγR binding.

Exosomes, which are one of the smallest extracellular vesicles released from cells, have been shown to carry different nucleic acids, including microRNAs (miRNAs). miRNAs significantly regulate cell growth and metabolism by posttranscriptional inhibition of gene expression. The rapidly changing understanding of exosomes’ formation and function in delivering miRNAs from cell to cell has prompted us to review current knowledge in exosomal miRNA secretion mechanisms as well as possible therapeutic applications for personalized medicine.

SummaryAnti-CD40 monoclonal antibodies (mAbs) that promote or inhibit receptor function hold promise as therapeutics for cancer and autoimmunity. Rules governing their diverse range of functions, however, are lacking. Here we determined characteristics of nine hCD40 mAbs engaging epitopes throughout the CD40 extracellular region expressed as varying isotypes. All mAb formats were strong agonists when hyper-crosslinked; however, only those binding the membrane-distal cysteine-rich domain 1 (CRD1) retained agonistic activity with physiological Fc gamma receptor crosslinking or as human immunoglobulin G2 isotype; agonistic activity decreased as epitopes drew closer to the membrane. In addition, all CRD2-4 binding mAbs blocked CD40 ligand interaction and were potent antagonists. Thus, the membrane distal CRD1 provides a region of choice for selecting CD40 agonists while CRD2-4 provides antagonistic epitopes.