To describe a case of allergic reaction to intravitreal (IVT) injection of antivascular endothelial growth factor (anti-VEGF) medications in patients with alpha-gal syndrome. A single case was evaluated. A 57-year-old woman with a known diagnosis of alpha-gal syndrome was evaluated. Clinical presentation, prior treatment history, and response to different anti-VEGF agents were reviewed. The patient presented with worsening vision in her right eye due to a subfoveal choroidal neovascular membrane secondary to neovascular age-related macular degeneration in the right eye. She had experienced a systemic allergic reaction following an IVT injection of bevacizumab, but subsequently tolerated ranibizumab without any adverse effects, resulting in improvement in her vision. Bevacizumab, aflibercept, and faricimab are recombinant immunoglobulins produced by DNA technology in Chinese hamster ovary cells, which may contain galactose-α-1,3-galactose (alpha-gal), a potential allergen for patients with alpha-gal syndrome. Patients with alpha-gal syndrome may develop allergic reactions to certain IVT anti-VEGF agents derived from mammalian expression systems. Ranibizumab, produced using an expression and lacking alpha-gal, seems to be a safe and effective option for patients with alpha-gal syndrome requiring IVT anti-VEGF therapy.
30 million years ago, ancestors of Old World primates lost the ability to produce α-gal. In this issue of Cell Host & Microbe, Singh et al. (2021) show that the loss is associated with increased resistance to sepsis, but that this advantage comes alongside a cost of accelerated reproductive senescence.
Chateau A, Oh SY, Tomatsidou A, Brockhausen I, Schneewind O, et al.
Journal of bacteriology •
, the causative agent of anthrax disease, elaborates a secondary cell wall polysaccharide (SCWP) that is required for the retention of surface layer (S-layer) and S-layer homology (SLH) domain proteins. Genetic disruption of the SCWP biosynthetic pathway impairs growth and cell division. SCWP is comprised of trisaccharide repeats composed of one ManNAc and two GlcNAc residues with O-3-α-Gal and O-4-β-Gal substitutions. UDP-Gal, synthesized by GalE1, is the substrate of galactosyltransferases that modify the SCWP repeat. Here, we show that the gene, which encodes a predicted glycosyltransferase with a GT-A fold, is required for O-4-β-Gal modification of trisaccharide repeats. We identify a DXD motif critical for GtsE activity. Three distinct genes, , , and , are required for O-3-α-Gal modification of trisaccharide repeats. Based on the similarity with other three-component glycosyltransferase systems, we propose that GtsA transfers Gal from cytosolic UDP-Gal to undecaprenyl phosphate (C-P), GtsB flips the C-P-Gal intermediate to the side of the membrane, and GtsC transfers Gal onto trisaccharide repeats. The deletion of does not affect growth , suggesting that galactosyl modifications are dispensable for the function of SCWP. The deletion of , , or leads to a loss of viability, yet and can be deleted in strains lacking or We propose that the loss of viability is caused by the accumulation of undecaprenol-bound precursors and present an updated model for SCWP assembly in to account for the galactosylation of repeat units. Peptidoglycan is a conserved extracellular macromolecule that protects bacterial cells from turgor pressure. Peptidoglycan of Gram-positive bacteria serves as a scaffold for the attachment of polymers that provide defined bacterial interactions with their environment. One such polymer, SCWP, is pyruvylated at its distal end to serve as a receptor for secreted proteins bearing the S-layer homology domain. Repeat units of SCWP carry three galactoses in Glycosylation is a recurring theme in nature and often represents a means to mask or alter conserved molecular signatures from intruders such as bacteriophages. Several glycosyltransferase families have been described based on bioinformatics prediction, but few have been studied. Here, we describe the glycosyltransferases that mediate the galactosylation of SCWP.
Chateau A, Lunderberg JM, Oh SY, Abshire T, Friedlander A, et al.
Journal of bacteriology •
, the causative agent of anthrax disease, elaborates a secondary cell wall polysaccharide (SCWP) that is essential for bacterial growth and cell division. SCWP is comprised of trisaccharide repeats with the structure, [→4)-β-ManNAc-(1→4)-β-GlcNAc(3-α-Gal)-(1→6)-α-GlcNAc(3-α-Gal, 4-β-Gal)-(1→] The genes whose products promote the galactosylation of SCWP are not yet known. We show here that the expression of , encoding a UDP-glucose 4-epimerase necessary for the synthesis of UDP-galactose, is required for SCWP galactosylation. The mutant assembles surface (S) layer and S layer-associated proteins that associate with ketal-pyruvylated SCWP via their S layer homology domains similarly to wild-type , but the mutant displays a defect in γ-phage murein hydrolase binding to SCWP. Furthermore, deletion of diminishes the capsulation of with poly-d-γ-glutamic acid (PDGA) and causes a reduction in bacterial virulence. These data suggest that SCWP galactosylation is required for the physiologic assembly of the cell wall envelope and for the pathogenesis of anthrax disease. Unlike virulent isolates, strain CDC684 synthesizes secondary cell wall polysaccharide (SCWP) trisaccharide repeats without galactosyl modification, exhibits diminished growth in broth cultures, and is severely attenuated in an animal model of anthrax. To examine whether SCWP galactosylation is a requirement for anthrax disease, we generated variants of strains Sterne 34F2 and Ames lacking UDP-glucose 4-epimerase by mutating the genes and We identified as necessary for SCWP galactosylation. Deletion of decreased the poly-d-γ-glutamic acid (PDGA) capsulation of the vegetative form of and increased the bacterial inoculum required to produce lethal disease in mice, indicating that SCWP galactosylation is indeed a determinant of anthrax disease.
Oh SY, Lunderberg JM, Chateau A, Schneewind O, Missiakas D
Journal of bacteriology •
The secondary cell wall polysaccharide (SCWP) is thought to be essential for vegetative growth and surface (S)-layer assembly in Bacillus anthracis; however, the genetic determinants for the assembly of its trisaccharide repeat structure are not known. Here, we report that WpaA (BAS0847) and WpaB (BAS5274) share features with membrane proteins involved in the assembly of O-antigen lipopolysaccharide in Gram-negative bacteria and propose that WpaA and WpaB contribute to the assembly of the SCWP in B. anthracis Vegetative forms of the B. anthracis wpaA mutant displayed increased lengths of cell chains, a cell separation defect that was attributed to mislocalization of the S-layer-associated murein hydrolases BslO, BslS, and BslT. The wpaB mutant was defective in vegetative replication during early logarithmic growth and formed smaller colonies. Deletion of both genes, wpaA and wpaB, did not yield viable bacilli, and when depleted of both wpaA and wpaB, B. anthracis could not maintain cell shape, support vegetative growth, or assemble SCWP. We propose that WpaA and WpaB fulfill overlapping glycosyltransferase functions of either polymerizing repeat units or transferring SCWP polymers to linkage units prior to LCP-mediated anchoring of the polysaccharide to peptidoglycan. The secondary cell wall polysaccharide (SCWP) is essential for Bacillus anthracis growth, cell shape, and division. SCWP is comprised of trisaccharide repeats (→4)-β-ManNAc-(1→4)-β-GlcNAc-(1→6)-α-GlcNAc-(1→) with α-Gal and β-Gal substitutions; however, the genetic determinants and enzymes for SCWP synthesis are not known. Here, we identify WpaA and WpaB and report that depletion of these factors affects vegetative growth, cell shape, and S-layer assembly. We hypothesize that WpaA and WpaB are involved in the assembly of SCWP prior to transfer of this polymer onto peptidoglycan.
Yilmaz B, Portugal S, Tran TM, Gozzelino R, Ramos S, et al.
Cell •
Glycosylation processes are under high natural selection pressure, presumably because these can modulate resistance to infection. Here, we asked whether inactivation of the UDP-galactose:β-galactoside-α1-3-galactosyltransferase (α1,3GT) gene, which ablated the expression of the Galα1-3Galβ1-4GlcNAc-R (α-gal) glycan and allowed for the production of anti-α-gal antibodies (Abs) in humans, confers protection against Plasmodium spp. infection, the causative agent of malaria and a major driving force in human evolution. We demonstrate that both Plasmodium spp. and the human gut pathobiont E. coli O86:B7 express α-gal and that anti-α-gal Abs are associated with protection against malaria transmission in humans as well as in α1,3GT-deficient mice, which produce protective anti-α-gal Abs when colonized by E. coli O86:B7. Anti-α-gal Abs target Plasmodium sporozoites for complement-mediated cytotoxicity in the skin, immediately after inoculation by Anopheles mosquitoes. Vaccination against α-gal confers sterile protection against malaria in mice, suggesting that a similar approach may reduce malaria transmission in humans.
Toyama A, Nakagawa H, Matsuda K, Sato TA, Nakamura Y, et al.
Analytical chemistry •
Site-specific characterization of glycoform heterogeneity currently requires glycan structure assignment and glycopeptide quantification in two independent experiments. We present here a new method combining multiple reaction monitoring mass spectrometry with energy-resolved structural analysis, which we termed "energy-resolved oxonium ion monitoring". We demonstrated that monitoring the yields of oligosaccharide-derived fragment ions (oxonium ions) over a wide range of collision induced dissociation (CID) energy applied to a glycopeptide precursor exhibits a glycan structure-unique fragmentation pattern. In the analysis of purified immunoglobulin glycopeptides, the energy-resolved oxonium ion profile was shown to clearly distinguish between isomeric glycopeptides. Moreover, limit of detection (LOD) of glycopeptide detection was 30 attomole injection, and quantitative dynamic range spanned 4 orders magnitude. Therefore, both quantification of glycopeptides and assignment of their glycan structures were achieved by a simple analysis procedure. We assessed the utility of this method for characterizing site-specific N-glycan microheterogeneity on therapeutic antibodies, including validation of lot-to-lot glycoform variability. A significant change in the degree of terminal galactosylation was observed in different production lots of trastuzumab and bevacizumab. Cetuximab Fab glycosylation, previously known to cause anaphylaxis, was also analyzed, and several causative antigens including Lewis X motifs were quantitatively detected. The data suggests that energy-resolved oxonium ion monitoring could fulfill the regulatory requirement on the routine quality control analysis of forthcoming biosimilar therapeutics.
Kim ES, Mauer AM, William WN, Tran HT, Liu D, et al.
Cancer •
Cetuximab in combination with docetaxel was examined in chemotherapy-refractory/resistant patients with advanced nonsmall-cell lung cancer (NSCLC) to determine response rate, survival, safety, and pharmacokinetics (PK). Patients had evidence of epidermal growth factor receptor (EGFR) expression (> or =1 +) and tumor progression during or disease recurrence within 3 months after chemotherapy. Cetuximab was administered weekly (400 mg/m(2) initial; 250 mg/m(2) thereafter). Docetaxel was administered every 3 weeks (75 mg/m(2)). A response in 3 of the first 21 patients was required to continue accrual to the target sample size of 50 patients. Confirmed responses included 1 complete response (1.8%), 10 partial responses (18.2%), and 20 with stable disease (36.4%). The response rate was 20% (95% confidence interval [CI], 10.4% to 33.0%) and median time to disease progression was 104 days. There were no differences in PK parameters of docetaxel alone or with cetuximab. The most common grade 3 of 4 adverse events were leukopenia (27.3%) and acne (21.8%). Four patients (7.3%) discontinued due to allergic reaction. The median overall survival (OS) was 7.5 months with a 1-year survival of 35%. Cetuximab in combination with docetaxel was well tolerated. The response rate supports more definitive evaluation of this combination in the second-line setting.
Herbst RS, Arquette M, Shin DM, Dicke K, Vokes EE, et al.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology •
This multicenter phase II study was undertaken to define the efficacy and safety of cetuximab, an antiepidermal growth factor receptor chimeric human and murine monoclonal antibody, administered with cisplatin to patients with refractory metastatic or recurrent squamous cell carcinoma of the head and neck (SCCHN). One hundred thirty-two patients were to receive two 3-week cycles with cisplatin/paclitaxel or cisplatin/fluorouracil. Patients (n = 30) with a complete or partial response continued standard therapy. Seventy-six patients with stable disease (SD; n = 51) or progressive disease (PD/1; n = 25) received combination therapy with cetuximab (400 mg/m2 intravenously on day 1, then 250 mg/m2/wk) and cisplatin (75 or 100 mg/m2 intravenously on day 1 every 3 weeks). The protocol was subsequently amended to enroll patients who had developed PD within 90 days after platinum-based therapy (PD/2; n = 54). Five patients (20%) in PD/1, three patients (6%) in PD/2, and nine patients (18%) with SD achieved an objective response. Median duration of response was 4.2, 4.1, and 7.4 months for the PD/1, PD/2, and SD groups, respectively, with median overall survival times of 6.1, 4.3, and 11.7 months. The most common toxicities were anemia, acne-like skin rash, leukopenia, fatigue and malaise, and nausea and vomiting. Seven patients (5%) developed a grade 3 or 4 hypersensitivity reaction to cetuximab. Cetuximab and cisplatin is an active regimen in refractory SCCHN. The relative contribution of cetuximab is better defined in a single-agent trial. Cetuximab did not exacerbate cisplatin toxicity but was associated with skin rash in a majority of patients and occasional serious allergic reactions. Further study of this compound is warranted.
