Glycan profiles of gp120 protein vaccines from four major HIV-1 subtypes produced from different host cell lines under non-GMP or GMP conditions

Envelope glycoprotein (Env) of human immunodeficiency virus type 1 (HIV-1) is an important target for the development of an HIV vaccine. Extensive glycosylation of Env is an important feature that both protects the virus from antibody responses and serves as a target for some highly potent broadly neutralizing antibodies. Therefore, analysis of glycans on recombinant Env proteins is highly significant. Here we present glycosylation profiles of recombinant gp120 proteins from four major clades of HIV-1 (A, B, C, and AE) produced either as research-grade material in 293 and CHO cells or as two independent lots of clinical material under GMP conditions. Almost all potential N-linked glycosylation sites were at least partially occupied in all proteins. The occupancy rates were largely consistent among proteins produced under different conditions, although a few sites showed substantial variability even between two GMP lots. Our data confirmed previous studies in the field showing high abundance of oligomannose on Env protein, with 40-50% of glycans having Man5-Man9 on all four proteins under all production conditions. Overall the differences in occupancy and glycan forms among Env from different subtypes produced under different conditions were less dramatic than anticipated and antigenicity analysis with a panel of six monoclonal antibodies showed that all four gp120s maintained their antibody-binding profiles, including antibodies that recognize glycan forms. Such findings have major implications to the final production of a clinical HIV vaccine including Env glycoprotein components. IMPORTANCE HIV-1 Env protein is a major target for the development of an HIV-1 vaccine. Env is covered with a large number of sugar-based glycan forms - about 50% of the Env molecular weight is composed of glycans. Glycan analysis of recombinant Env proteins is important to understand its roles in vial pathogenesis and immune responses. The current report presents the first extensive comparison of glycosylation patterns of recombinant gp120 proteins from four major clades of HIV-1 produced in two different cell lines, grown at either laboratory condition or at 50L GMP scale across different lots. Information learned in this study is valuable for the further design and production of HIV-1 Env proteins as the critical components of HIV-1 vaccine formulations

Phosphatidic acid phospholipase A1 mediates ER-Golgi transit of a family of G protein-coupled receptors

The coat protein II (COPII)-coated vesicular system transports newly synthesized secretory and membrane proteins from the endoplasmic reticulum (ER) to the Golgi complex. Recruitment of cargo into COPII vesicles requires an interaction of COPII proteins either with the cargo molecules directly or with cargo receptors for anterograde trafficking. We show that cytosolic phosphatidic acid phospholipase A1 (PAPLA1) interacts with COPII protein family members and is required for the transport of Rh1 (rhodopsin 1), an N-glycosylated G protein-coupled receptor (GPCR), from the ER to the Golgi complex. In papla1 mutants, in the absence of transport to the Golgi, Rh1 is aberrantly glycosylated and is mislocalized. These defects lead to decreased levels of the protein and decreased sensitivity of the photoreceptors to light. Several GPCRs, including other rhodopsins and Bride of sevenless, are similarly affected. Our findings show that a cytosolic protein is necessary for transit of selective transmembrane receptor cargo by the COPII coat for anterograde trafficking

Abnormal Cartilage Development and Altered N-Glycosylation in Tmem165-Deficient Zebrafish Mirrors the Phenotypes Associated with TMEM165-CDG

The Congenital Disorders of Glycosylation (CDG), a group of inherited diseases characterized by defective glycosylation, encompass a wide range of defects including glycosyltransferases, glycosidases, nucleotide-sugar transporters, as well as proteins involved in maintaining Golgi architecture, pH, and vesicular trafficking. Mutations in a previously undescribed protein, TMEM165, were recently shown to cause a new form of CDG, termed TMEM165-CDG. TMEM165-CDG patients exhibit cartilage and bone dysplasia and altered glycosylation of serum glycoproteins. We utilized a morpholino knockdown strategy in zebrafish to investigate the physiologic and pathogenic functions of TMEM165. Inhibition of tmem165 expression in developing zebrafish embryos caused craniofacial abnormalities, largely attributable to fewer chondrocytes. Decreased expression of several markers of cartilage and bone development suggests that Tmem165 deficiency alters both chondrocyte and osteoblast differentiation. Glycomic analysis of tmem165 morphants also revealed altered initiation, processing, and extension of N-glycans, paralleling some of the glycosylation changes noted in human patients. Collectively, these findings highlight the utility of zebrafish to elucidate pathogenic mechanisms associated with glycosylation disorders and suggest that the cartilage and bone dysplasia manifested in TMEM165-CDG patients may stem from abnormal development of chondrocytes and osteoblasts.status: publishe

Mass Spectrometric Quantification of N‑Linked Glycans by Reference to Exogenous Standards

Environmental and metabolic processes shape the profile of glycoprotein glycans expressed by cells, whether in culture, developing tissues, or mature organisms. Quantitative characterization of glycomic changes associated with these conditions has been achieved historically by reductive coupling of oligosaccharides to various fluorophores following release from glycoprotein and subsequent HPLC or capillary electrophoretic separation. Such labeling-based approaches provide a robust means of quantifying glycan amount based on fluorescence yield. Mass spectrometry, on the other hand, has generally been limited to relative quantification in which the contribution of the signal intensity for an individual glycan is expressed as a percent of the signal intensity summed over the total profile. Relative quantification has been valuable for highlighting changes in glycan expression between samples; sensitivity is high, and structural information can be derived by fragmentation. We have investigated whether MS-based glycomics is amenable to absolute quantification by referencing signal intensities to well-characterized oligosaccharide standards. We report the qualification of a set of N-linked oligosaccharide standards by NMR, HPLC, and MS. We also demonstrate the dynamic range, sensitivity, and recovery from complex biological matrices for these standards in their permethylated form. Our results indicate that absolute quantification for MS-based glycomic analysis is reproducible and robust utilizing currently available glycan standards

Route of immunization defines multiple mechanisms of vaccine-mediated protection against SIV

Antibodies are the primary correlate of protection for most licensed vaccines; however, their mechanisms of protection vary, ranging from physical blockade to clearance via the recruitment of innate immunity. Here, we uncover striking functional diversity in vaccine-induced antibodies associated with reduced risk of SIV infection in nonhuman primates. While equivalent levels of protection were observed following intramuscular (IM) and aerosol (AE) immunization, reduced risk of infection was associated IgG-driven antibody-dependent monocyte-mediated phagocytosis in the IM vaccinees, and via vaccine-elicited IgA-driven neutrophil-mediated phagocytosis in AE immunized animals. Thus while route independent correlates indicate a critical role for phagocytic Fc-effector activity in protection from SIV, the site of immunization may drive this Fc-activity via distinct innate effector cells and antibody isotypes. These data identify orthogonal functional humoral mechanisms, initiated by distinct vaccination routes, pointing to critical correlates of immunity that may support the rational design of a protective vaccine against HIV.Bill & Melinda Gates Foundation (OPP1032817)Bill & Melinda Gates Foundation (OPP1114729)National Institutes of Health (U.S.) (R37 AI080289)National Institutes of Health (U.S.) (R01 AI102291)National Institutes of Health (U.S.) (P01 AI120756)National Institutes of Health (U.S.) (R01 AI131975)National Institutes of Health (U.S.) (R01 AI102660