IgG subclass co-expression brings harmony to the quartet model of murine IgG function

Injectable, Tough Alginate Cryogels as Cancer Vaccines

A covalently crosslinked methacrylated (MA)-alginate cryogel vaccine has been previously shown to generate a potent response against murine melanoma, but is not mechanically robust and requires a large 16G needle for delivery. Here, covalent and ionic crosslinking of cryogels are combined with the hypothesis that this will result in a tough MA-alginate cryogel with improved injectability. All tough cryogels can be injected through a smaller, 18G needle without sustaining any damage, while covalently crosslinked-only cryogels break after injection. Cytosine-phosphodiester-guanine (CpG)-delivering tough cryogels effectively activate dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor releasing tough cryogels recruit four times more DCs than blank gels by day 7 in vivo. The tough cryogel vaccine induces strong antigen-specific cytotoxic T-lymphocyte and humoral responses. These vaccines prevent tumor formation in 80% of mice inoculated with HER2/neu-overexpressing DD breast cancer cells. The MA-alginate tough cryogels provide a promising minimally invasive delivery platform for cancer vaccinations.

Interplay of Carbohydrate and Carrier in Antibacterial Glycoconjugate Vaccines

Bacterial infections are a serious health concern and are responsible for millions of illnesses and deaths each year in communities around the world. Vaccination is an important public health measure for reducing and eliminating this burden, and regions with comprehensive vaccination programs have achieved significant reductions in infection and mortality. This is often accomplished by immunization with bacteria-derived carbohydrates, typically in conjunction with other biomolecules, which induce immunological memory and durable protection against bacterial human pathogens. For many species, however, vaccines are currently unavailable or have suboptimal efficacy characterized by short-lived memory and incomplete protection, especially among at-risk populations. To address this challenge, new tools and techniques have emerged for engineering carbohydrates and conjugating them to carrier molecules in a tractable and scalable manner. Collectively, these approaches are yielding carbohydrate-based vaccine designs with increased immunogenicity and protective efficacy, thereby opening up new opportunities for this important class of antigens. In this chapter we detail the current understanding of how carbohydrates interact with the immune system to provide immunity; how glycoengineering, especially in the context of glycoconjugate vaccines, can be used to modify and enhance immune responses; and current trends and strategies being pursued for the rational design of next-generation glycosylated antibacterial vaccines. Graphical Abstract.

N-Terminal Pfs230 Domain Produced in Baculovirus as a Biological Active Transmission-Blocking Vaccine Candidate

Transmission-blocking vaccines have the potential to accelerate malaria parasite elimination by inducing antibodies that block parasite transmission from humans to mosquitoes. Pfs230, a gametocyte surface protein involved in gamete function, has long been a promising candidate. Due to the large size (3,135 amino acids), complex domains, and repeating 6-cysteine (6-Cys) motifs with a multitude of disulfide bonds, the feasibility of expression of a full-length protein has been difficult. A priority focus, therefore, has been on the generation of single domains, including N-terminal fragments. Here we utilized a heterologous expression system, baculovirus, to produce an N-terminal domain of Pfs230 (Pfs230C1). Pfs230C1 (amino acids 443 to 731) with a polyhistidine affinity tag was expressed in Super Sf9 cells. Since the native host lacks glycosylation machinery, a single N585Q mutation was made to eliminate potential N-linked glycosylation. The expressed protein, purified by nickel affinity, ion exchange, and size exclusion chromatography to >90% purity, was present in monomeric form with an observed mass of 33,510 Da (matching oxidized form). Peptide mapping and disulfide analysis confirmed the proper formation of predicted disulfide bonds. Antibodies, generated against Pfs230C1 in mice, bound to the gametocyte in an immunofluorescence assay (IFA) and demonstrated functional activity in both the standard membrane feeding assay (SMFA) and the exflagellation assay (EXA). The biochemical, biophysical, and immunological results reported herein support the continued advancement of an N-terminal Pfs230 antigen (Pfs230C1) as a component of a transmission-blocking vaccine. Our results also support the continued use of the scalable baculovirus expression system for the generation of complex Plasmodium proteins.

A new marine-derived sulfoglycolipid triggers dendritic cell activation and immune adjuvant response

Dendritic Cells (DCs) recognize infectious non-self molecules and engage the adaptive immune system thereby initiating long lasting, antigen-specific responses. As such, the ability to activate DCs is considered a key tool to enhance the efficacy and quality of vaccination. Here we report a novel immunomodulatory sulfolipid named β-SQDG18 that prototypes a class of natural-derived glycolipids able to prime human DCs by a TLR2/TLR4-independent mechanism and trigger an efficient immune response in vivo. β-SQDG18 induces maturation of DC with the upregulation of MHC II molecules and co-stimulatory proteins (CD83, CD86), as well as pro-inflammatory cytokines (IL-12 and INF-γ). Mice immunized with OVA associated to β-SQDG18 (1:500) produced a titer of anti-OVA Ig comparable to traditional adjuvants. In an experimental model of melanoma, vaccination of C57BL/6 mice with β-SQDG18-adjuvanted hgp10 peptide elicited a protective response with a reduction in tumour growth and increase in survival.

Human IgG2- and IgG4-expressing memory B cells display enhanced molecular and phenotypic signs of maturity and accumulate with age

The mechanisms involved in sequential immunoglobulin G (IgG) class switching are still largely unknown. Sequential IG class switching is linked to higher levels of somatic hypermutation (SHM) in vivo, but it remains unclear if these are generated temporally during an immune response or upon activation in a secondary response. We here aimed to uncouple these processes and to distinguish memory B cells from primary and secondary immune responses. SHM levels and IgG subclasses were studied with 454 pyrosequencing on blood mononuclear cells from young children and adults as models for primary and secondary immunological memory. Additional sequencing and detailed immunophenotyping with IgG subclass-specific antibodies was performed on purified IgG⁺ memory B-cell subsets. In both children and adults, SHM levels were higher in transcripts involving more downstream-located IGHG genes (esp. IGHG2 and IGHG4). In adults, SHM levels were significantly higher than in children, and downstream IGHG genes were more frequently utilized. This was associated with increased frequencies of CD27⁺IgG⁺ memory B cells, which contained higher levels of SHM, more IGHG2 usage, and higher expression levels of activation markers than CD27⁻IgG⁺ memory B cells. We conclude that secondary immunological memory accumulates with age and these memory B cells express CD27, high levels of activation markers, and carry high SHM levels and frequent usage of IGHG2. These new insights contribute to our understanding of sequential IgG subclass switching and show a potential relevance of using serum IgG2 levels or numbers of IgG2-expressing B cells as markers for efficient generation of memory responses.

Borrelia burgdorferi Manipulates Innate and Adaptive Immunity to Establish Persistence in Rodent Reservoir Hosts

Borrelia burgdorferi sensu lato species complex is capable of establishing persistent infections in a wide variety of species, particularly rodents. Infection is asymptomatic or mild in most reservoir host species, indicating successful co-evolution of the pathogen with its natural hosts. However, infected humans and other incidental hosts can develop Lyme disease, a serious inflammatory syndrome characterized by tissue inflammation of joints, heart, muscles, skin, and CNS. Although B. burgdorferi infection induces both innate and adaptive immune responses, they are ultimately ineffective in clearing the infection from reservoir hosts, leading to bacterial persistence. Here, we review some mechanisms by which B. burgdorferi evades the immune system of the rodent host, focusing in particular on the effects of innate immune mechanisms and recent findings suggesting that T-dependent B cell responses are subverted during infection. A better understanding of the mechanisms causing persistence in rodents may help to increase our understanding of the pathogenesis of Lyme disease and ultimately aid in the development of therapies that support effective clearance of the bacterial infection by the host’s immune system.