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Background Human CD200 receptor (CD200R, CD200R1), originally OX2R, is an inhibitory immune checkpoint receptor expressed on many myeloid cells, and lymphocyte populations including CD4 T and ILC2 cells, signaling via DOK2 and Erk/MAP kinases to inhibit the NFkB pathway and cytokine secretion. Its ligand, CD200, is expressed on the surface of tissues including endothelium, epithelia and neurons, where it moderates immune activation particularly at barrier sites including lung, skin and the GI tract. Published evidence, including GWAS studies, implicates dysregulation of the CD200 axis in many allergic, autoimmune and inflammatory diseases. Furthermore, a CD200R agonist antibody has demonstrated efficacy in an early phase clinical trial of moderate to severe atopic dermatitis patients. Methods We have engineered high affinity soluble CD200R agonists, comprising human CD200-Fc proteins with substantially increased (up to 130-fold) monomeric binding affinity for CD200R. Results High affinity human CD200-Fc a) out-performs wild type in inhibiting IL-6 release from a cell line expressing high levels of human CD200R, b) has superior potency to a CD200R agonist antibody in a humanized mouse model of contact hypersensitivity, and c) substantially reduces cell infiltrate in bronchoalveolar lavage fluid in a non-human primate model of airway inflammation. A high affinity murine CD200-Fc has been engineered for additional proof-of-concept studies, and is more potent than wild type in an in vivo model (collagen-induced arthritis). Finally, we describe ARQ-234, a high affinity CD200-Fc protein with antibody-like serum half-life in NHP, due to the introduction of mutations in the Fc domain which increase relative binding to the neonatal Fc receptor at low (endosomal) pH. ARQ-234 is currently in pre-clinical development as a therapeutic for atopic dermatitis. [ABSTRACT FROM AUTHOR]

Virus‐like particles (VLPs) induce strong humoral and cellular responses and have formed the basis of some currently licensed vaccines. Here, we present the method used for the production of R21, a VLP‐based anti‐sporozoite malaria vaccine, under current Clinical Good Manufacturing Practice regulations (cGMP). Previous preclinical studies in BALB/c mice showed that R21 produced almost complete protection against sporozoite challenge with transgenic Plasmodium berghei parasites. Here, we have modified the preclinical production process to enable the production of sufficient quantities of highly pure, clinical‐grade material for use in human clinical trials. The R21 construct was re‐engineered to include a C‐tag to allow affinity‐based separation from the major contaminant alcohol oxidase 1 (AOX 1, ~74 kDa). To our knowledge, this is the first use of C‐tag technology to purify a VLP vaccine candidate for use in human clinical trials. The R21 vaccine has shown high‐level efficacy in an African Phase IIb trial, and multiple clinical trials are underway to assess the safety and efficacy of the vaccine. Our findings support the future use of C‐tag platform technologies to enable cGMP‐compliant biomanufacturing of high purity yeast‐expressed VLP‐based vaccines for early phase clinical trials when clinical grade material is required in smaller quantities in a quick time frame. [ABSTRACT FROM AUTHOR]

T cell immunity can potentially eradicate malignant cells and lead to clinical remission in a minority of patients with cancer. In the majority of these individuals, however, there is a failure of the specific T cell receptor (TCR)-mediated immune recognition and activation process. Here we describe the engineering and characterization of new reagentstermed immune-mobilizing monoclonal TCRs against cancer (ImmTACs). Four such ImmTACs, each comprising a distinct tumor-associated epitope-specific monoclonal TCR with picomolar affinity fused to a humanized cluster of differentiation 3 (CD3)-specific single-chain antibody fragment (scFv), effectively redirected T cells to kill cancer cells expressing extremely low surface epitope densities. Furthermore, these reagents potently suppressed tumor growth in vivo. Thus, ImmTACs overcome immune tolerance to cancer and represent a new approach to tumor immunotherapy., Harnessing the power of adaptive immunity to combat cancer has been a long-term goal of translational immunotherapy. However, although many avenues in this field have been explored over the past [...]

The hurdles to effective blood stage malaria vaccine design include immune evasion tactics used by the parasite such as redundant invasion pathways and antigen variation among circulating parasite strains. While blood stage malaria vaccine development primarily focuses on eliciting optimal humoral responses capable of blocking erythrocyte invasion, clinically-tested Plasmodium falciparum (Pf) vaccines have not elicited sterile protection, in part due to the dramatically high levels of antibody needed. Recent development efforts with non-redundant, conserved blood stage antigens suggest both high antibody titer and rapid antibody binding kinetics are important efficacy factors. Based on the central role of helper CD4 T cells in development of strong, protective immune responses, we systematically analyzed the class II epitope content in five leading Pf blood stage antigens (RH5, CyRPA, RIPR, AMA1 and EBA175) using in silico , in vitro , and ex vivo methodologies. We employed in silico T cell epitope analysis to enable identification of 67 HLA-restricted class II epitope clusters predicted to bind a panel of nine HLA-DRB1 alleles. We assessed a subset of these for HLA-DRB1 allele binding in vitro , to verify the in silico predictions. All clusters assessed (40 clusters represented by 46 peptides) bound at least two HLA-DR alleles in vitro. The overall epitope prediction to in vitro HLA-DRB1 allele binding accuracy was 71%. Utilizing the set of RH5 class II epitope clusters (10 clusters represented by 12 peptides), we assessed stimulation of T cells collected from HLA-matched RH5 vaccinees using an IFN-γ T cell recall assay. All clusters demonstrated positive recall responses, with the highest responses – by percentage of responders and response magnitude – associated with clusters located in the N-terminal region of RH5. Finally, a statistically significant correlation between in silico epitope predictions and ex vivo IFN-γ recall response was found when accounting for HLA-DR matches between the epitope predictions and donor HLA phenotypes. This is the first comprehensive analysis of class II epitope content in RH5, CyRPA, RIPR, AMA1 and EBA175 accompanied by in vitro HLA binding validation for all five proteins and ex vivo T cell response confirmation for RH5. [ABSTRACT FROM AUTHOR]

Computational vaccinology includes epitope mapping, antigen selection, and immunogen design using computational tools. Tools that facilitate the in silico prediction of immune response to biothreats, emerging infectious diseases, and cancers can accelerate the design of novel and next generation vaccines and their delivery to the clinic. Over the past 20 years, vaccinologists, bioinformatics experts, and advanced programmers based in Providence, Rhode Island, USA have advanced the development of an integrated toolkit for vaccine design called iVAX, that is secure and user-accessible by internet. This integrated set of immunoinformatic tools comprises algorithms for scoring and triaging candidate antigens, selecting immunogenic and conserved T cell epitopes, re-engineering or eliminating regulatory T cell epitopes, and re-designing antigens to induce immunogenicity and protection against disease for humans and livestock. Commercial and academic applications of iVAX have included identifying immunogenic T cell epitopes in the development of a T-cell based human multi-epitope Q fever vaccine, designing novel influenza vaccines, identifying cross-conserved T cell epitopes for a malaria vaccine, and analyzing immune responses in clinical vaccine studies. Animal vaccine applications to date have included viral infections of pigs such as swine influenza A, PCV2, and African Swine Fever. "Rapid-Fire" applications for biodefense have included a demonstration project for Lassa Fever and Q fever. As recent infectious disease outbreaks underscore the significance of vaccine-driven preparedness, the integrated set of tools available on the iVAX toolkit stand ready to help vaccine developers deliver genome-derived, epitope-driven vaccines. [ABSTRACT FROM AUTHOR]

Background: Estimates of current global rabies mortality range from 26,000 to 59,000 deaths per annum. Although pre-exposure prophylaxis using inactivated rabies virus vaccines (IRVs) is effective, it requires two to three doses and is regarded as being too expensive and impractical for inclusion in routine childhood immunization programmes. Methodology/ Principal findings: Here we report the development of a simian-adenovirus-vectored rabies vaccine intended to enable cost-effective population-wide pre-exposure prophylaxis against rabies. ChAdOx2 RabG uses the chimpanzee adenovirus serotype 68 (AdC68) backbone previously shown to achieve pre-exposure protection against rabies in non-human primates. ChAdOx2 differs from AdC68 in that it contains the human adenovirus serotype 5 (AdHu5) E4 orf6/7 region in place of the AdC68 equivalents, enhancing ease of manufacturing in cell lines which provide AdHu5 E1 proteins in trans. We show that immunogenicity of ChAdOx2 RabG in mice is comparable to that of AdC68 RabG and other adenovirus serotypes expressing rabies virus glycoprotein. High titers of rabies virus neutralizing antibody (VNA) are elicited after a single dose. The relationship between levels of VNA activity and rabies virus glycoprotein monomer-binding antibody differs after immunization with adenovirus-vectored vaccines and IRV vaccines, suggesting routes to further enhancement of the efficacy of the adenovirus-vectored candidates. We also demonstrate that ChAdOx2 RabG can be thermostabilised using a low-cost method suitable for clinical bio-manufacture and ambient-temperature distribution in tropical climates. Finally, we show that a dose-sparing effect can be achieved by formulating ChAdOx2 RabG with a simple chemical adjuvant. This approach could lower the cost of ChAdOx2 RabG and other adenovirus-vectored vaccines. Conclusions/ Significance: ChAdOx2 RabG may prove to be a useful tool to reduce the human rabies death toll. We have secured funding for Good Manufacturing Practice- compliant bio-manufacture and Phase I clinical trial of this candidate. [ABSTRACT FROM AUTHOR]

An abstract of the article "Engineered Gag-specific T-cell Receptors Redirect Polyclonal CD81 T-cells to Clear HIV-1-infected CD41 T-cells from ART-treated Patients" by Hongbing Yang and colleagues is presented.

Plasmodium falciparum reticulocyte-binding protein homolog 5 (RH5) is a leading blood-stage malaria vaccine antigen target, currently in a phase 2b clinical trial as a full-length soluble protein/adjuvant vaccine candidate called RH5.1/Matrix-M. We identify that disordered regions of the full-length RH5 molecule induce non-growth inhibitory antibodies in human vaccinees and that a re-engineered and stabilized immunogen (including just the alpha-helical core of RH5) induces a qualitatively superior growth inhibitory antibody response in rats vaccinated with this protein formulated in Matrix-M adjuvant. In parallel, bioconjugation of this immunogen, termed "RH5.2," to hepatitis B surface antigen virus-like particles (VLPs) using the "plug-and-display" SpyTag-SpyCatcher platform technology also enables superior quantitative antibody immunogenicity over soluble protein/adjuvant in vaccinated mice and rats. These studies identify a blood-stage malaria vaccine candidate that may improve upon the current leading soluble protein vaccine candidate RH5.1/Matrix-M. The RH5.2-VLP/Matrix-M vaccine candidate is now under evaluation in phase 1a/b clinical trials., Competing Interests: Declaration of interests S.J.D. is an inventor on patent applications relating to RH5 malaria vaccines and antibodies, is a co-founder of and shareholder in SpyBiotech, and has been a consultant to GSK on malaria vaccines. A.M.M. has been a consultant to GSK on malaria vaccines, has an immediate family member who is an inventor on patent applications relating to RH5 malaria vaccines and antibodies, and is a co-founder of and shareholder in SpyBiotech. M.R.H. is an inventor on patents relating to peptide targeting via spontaneous amide bond formation and is a co-founder of and shareholder in SpyBiotech. S.B. is an inventor on patent applications relating to vaccines made using spontaneous amide bond formation and is a co-founder of, shareholder in, and employee of SpyBiotech. J.J. is an inventor on patent applications relating to vaccines made using spontaneous amide bond formation and is a co-founder of and shareholder in SpyBiotech. R.A.D. is an inventor on patent applications relating to vaccines made using spontaneous amide bond formation and shareholder in SpyBiotech. L.D.W.K., J.R.B., D.Q., A.M.L., S.E.S., B.G.W., K. McHugh, I.C., S.J.F., and D.P. are inventors on patent applications relating to RH5 malaria vaccines and/or antibodies., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The development of a highly effective vaccine remains a key strategic goal to aid the control and eventual eradication of Plasmodium falciparum malaria. In recent years, the reticulocyte-binding protein homolog 5 (RH5) has emerged as the most promising blood-stage P. falciparum candidate antigen to date, capable of conferring protection against stringent challenge in Aotus monkeys. We report on the first clinical trial to our knowledge to assess the RH5 antigen - a dose-escalation phase Ia study in 24 healthy, malaria-naive adult volunteers. We utilized established viral vectors, the replication-deficient chimpanzee adenovirus serotype 63 (ChAd63), and the attenuated orthopoxvirus modified vaccinia virus Ankara (MVA), encoding RH5 from the 3D7 clone of P. falciparum. Vaccines were administered i.m. in a heterologous prime-boost regimen using an 8-week interval and were well tolerated. Vaccine-induced anti-RH5 serum antibodies exhibited cross-strain functional growth inhibition activity (GIA) in vitro, targeted linear and conformational epitopes within RH5, and inhibited key interactions within the RH5 invasion complex. This is the first time to our knowledge that substantial RH5-specific responses have been induced by immunization in humans, with levels greatly exceeding the serum antibody responses observed in African adults following years of natural malaria exposure. These data support the progression of RH5-based vaccines to human efficacy testing.

Persistence of human immunodeficiency virus (HIV) in a latent state in long-lived CD4+ T-cells is a major barrier to eradication. Latency-reversing agents that induce direct or immune-mediated cell death upon reactivation of HIV are a possible solution. However, clearance of reactivated cells may require immunotherapeutic agents that are fine-tuned to detect viral antigens when expressed at low levels. We tested the antiviral efficacy of immune-mobilizing monoclonal T-cell receptors against viruses (ImmTAVs), bispecific molecules that redirect CD8+ T-cells to kill HIV-infected CD4+ T-cells. T-cell receptors specific for an immunodominant Gag epitope, SL9, and its escape variants were engineered to achieve supraphysiological affinity and fused to a humanised CD3-specific single chain antibody fragment. Ex vivo polyclonal CD8+ T-cells were efficiently redirected by immune-mobilising monoclonal T-cell receptors against viruses to eliminate CD4+ T-cells from human histocompatibility leukocyte antigen (HLA)-A*0201-positive antiretroviral therapy-treated patients after reactivation of inducible HIV in vitro. The efficiency of infected cell elimination correlated with HIV Gag expression. Immune-mobilising monoclonal T-cell receptors against viruses have potential as a therapy to facilitate clearance of reactivated HIV reservoir cells.

Tumor-associated human telomerase reverse transcriptase (hTERT) is expressed in >85% of human tumors but not in most normal cells. As a result, this antigen has received considerable attention from those interested in cancer immunotherapy. Specifically, there has been strong interest in MHC class I-associated peptides derived from hTERT because these are expressed on the cell surface and thus may enable the targeting of tumor cells. Much of this interest has focused on peptide 540-548, ILAKFLHWL, which was predicted to exhibit the strongest binding to the common HLA A*0201 presenting molecule. The hTERT(540-548) peptide is currently being assessed in therapeutic vaccination trials; however, there is controversy surrounding whether it is naturally processed and presented on the surface of neoplastic cells. Here, we generate two highly sensitive reagents to assess the presentation of hTERT(540-548) on tumor cells: (a) a CD8(+) CTL clone, and (b) a recombinant T-cell receptor (TCR) that binds with picomolar affinity and a half-life exceeding 14 h. This TCR enables the identification of individual HLA A2-hTERT(540-548) complexes on the cell surface. The use of both this TCR and the highly antigen-sensitive CTL clone shows that the hTERT(540-548) peptide cannot be detected on the surface of tumor cells, indicating that this peptide is not a naturally presented epitope. We propose that, in future, rigorous methods must be applied for the validation of peptide epitopes used for clinical applications.

The last two decades have seen the development of an expanding array of monoclonal antibodies, which are proving to be effective treatments for both cancer and autoimmune disease. A related protein, the human T-cell receptor (TCR), is able to access a new range of targets for which antibodies are unsuitable, and is being developed as a new class of protein therapeutics. Similar to antibodies, TCRs have a specific target and therefore a limited potential for side effects; however, a possible drawback with these receptors is that their natural affinity is low. This problem has recently been overcome using phage display to increase TCR affinity up to a million-fold.