The neonatal Fc receptor (FcRn) promotes antibody recycling through rescue from normal lysosomal degradation. The binding interaction is pH-dependent with high affinity at low pH, but not under ...physiological pH conditions. Here, we combined rational design and saturation mutagenesis to generate novel antibody variants with prolonged half-life and acceptable development profiles. First, a panel of saturation point mutations was created at 11 key FcRn-interacting sites on the Fc region of an antibody. Multiple variants with slower FcRn dissociation kinetics than the wildtype (WT) antibody at pH 6.0 were successfully identified. The mutations were further combined and characterized for pH-dependent FcRn binding properties, thermal stability and the FcγRIIIa and rheumatoid factor binding. The most promising variants, YD (M252Y/T256D), DQ (T256D/T307Q) and DW (T256D/T307W), exhibited significantly improved binding to FcRn at pH 6.0 and retained similar binding properties as WT at pH 7.4. The pharmacokinetics in human FcRn transgenic mice and cynomolgus monkeys demonstrated that these properties translated to significantly prolonged plasma elimination half-life compared to the WT control. The novel variants exhibited thermal stability and binding to FcγRIIIa in the range comparable to clinically validated YTE and LS variants, and showed no enhanced binding to rheumatoid factor compared to the WT control. These engineered Fc mutants are promising new variants that are widely applicable to therapeutic antibodies, to extend their circulation half-life with obvious benefits of increased efficacy, and reduced dose and administration frequency.
Because of their favorable properties as macromolecular drugs, antibodies are a very successful therapeutic modality for interfering with disease-relevant targets in the extracellular space or at the ...cell membrane. However, a large number of diseases involve cytosolic targets and designing antibodies able to efficiently reach intracellular compartments would expand the antibody-tractable conditions. Here, we genetically fused cell penetrating peptides (CPPs) at various positions to an antibody targeting cancer cells, evaluated the developability features of the resulting antibody-peptide fusions and the ability of selected constructs to reach the cytosol. We first determined positions in the IgG structure that were permissive to CPP incorporation without destabilizing the antibody. Fusing CPPs to the C-terminus of the light chain and either before or after the hinge had the least effect on antibody developability features. These constructs were further evaluated for cell penetration efficiency. Two out of five tested CPPs significantly enhanced antibody penetration into the cytosol, in particular when fused before or after the hinge. Finally, we demonstrate that specific antibody binding to the cell surface target is necessary for efficient cell penetration of the CPP-antibody fusions. This study provides a solid basis for further exploration of therapeutic antibodies for intracellular targets.
There is an urgent need for an efficacious vaccine against tuberculosis (TB). Cellular immune responses are key to an effective protective response against TB. Recombinant adenovirus (rAd) vectors ...are especially suited to the induction of strong T-cell immunity and thus represent promising vaccine vehicles for the prevention of TB. We have previously reported on rAd vector serotype 35, the serotype of choice due to low preexisting immunity worldwide, which expresses a unique fusion protein of Mycobacterium tuberculosis antigens Ag85A, Ag85B, and TB10.4 (Ad35-TBS). Here, we demonstrate that Ad35-TBS confers protection against M. tuberculosis when administered to mice through either an intranasal or an intramuscular route. Histological evaluation of lung tissue corroborated the protection and, in addition, demonstrated differences between two mouse strains, with diffuse inflammation in BALB/c mice and distinct granuloma formation in C57BL/6 mice. Epitope mapping analysis in these mouse strains showed that the major T-cell epitopes are conserved in the artificial fusion protein, while three novel CD8 peptides were discovered. Using a defined set of T-cell epitopes, we reveal differences between the two mouse strains in the type of protective immune response, demonstrating that different antigen-specific gamma interferon (IFN-γ)-producing T cells can provide protection against M. tuberculosis challenge. While in BALB/c (H-2d) mice, a dominant CD8 T-cell response was detected, in C57BL/6 (H-2b) mice, more balanced CD4/CD8 T-cell responses were observed, with a more pronounced CD4 response in the lungs. These results unify conflicting reports on the relative importance of CD4 versus CD8 T-cell responses in protection and emphasize the key role of IFN-γ.
It remains important to develop the next generation of influenza vaccines that can provide protection against vaccine mismatched strains and to be prepared for potential pandemic outbreaks. To ...achieve this, the understanding of the immunological parameters that mediate such broad protection is crucial.
In the current study we assessed the contribution of humoral and cellular immune responses to heterosubtypic protection against H5N1 induced by a Matrix-M (MM) adjuvanted seasonal influenza vaccine by serum transfer and T-cell depletion studies.
We demonstrate that the heterosubtypic protection against H5N1 induced by MM adjuvanted vaccine is partially mediated by antibodies. The serum contained both H5N1 cross-reactive hemagglutinin (HA)- and neuraminidase (NA)-specific antibodies but with limited virus neutralizing and no hemagglutination inhibiting activity. The cross-reactive antibodies induced antibody-dependent cellular cytotoxicity (ADCC) in vitro, suggesting a role for the Fc part of the antibodies in protection against H5N1. Besides H5N1 specific antibody responses, cross-reactive HA- and NA-specific T-cell responses were induced by the adjuvanted vaccine. T-cell depletion experiments demonstrated that both CD4+ and CD8+ T cells contribute to protection.
Our study demonstrates that cross-protection against H5N1 induced by MM adjuvanted seasonal virosomal influenza vaccine requires both the humoral and cellular arm of the immune system.
Monoclonal antibodies (mAbs) for therapeutic applications should be as similar to native human antibodies as possible to minimize their immunogenicity in patients. Several transgenic animal platforms ...are available for the generation of fully human mAbs. Attributes such as specificity, efficacy and Chemistry, Manufacturing and Controls (CMC) developability of antibodies against a specific target are typically established for antibodies obtained from one platform only. In this study, monoclonal antibodies (mAbs) cross-reactive against human and cynomolgus LAMP1 were derived from the human immunoglobulin transgenic TRIANNI mouse and OmniChicken® platforms and assessed for their specificity, sequence diversity, ability to bind to and internalize into tumor cells, expected immunogenicity and CMC developability. Our results show that the two platforms were complementary at providing a large diversity of mAbs with respect to epitope coverage and antibody sequence diversity. Furthermore, most antibodies originating from either platform exhibited good manufacturability characteristics.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for one of the worst pandemics in modern history. Several prevention and treatment strategies have been designed and ...evaluated in recent months either through the repurposing of existing treatments or the development of new drugs and vaccines. In this study, we show that L-carnitine tartrate supplementation in humans and rodents led to significant decreases of key host dependency factors, notably angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2), and Furin, which are responsible for viral attachment, viral spike S-protein cleavage, and priming for viral fusion and entry. Interestingly, pre-treatment of Calu-3, human lung epithelial cells, with L-carnitine tartrate led to a significant and dose-dependent inhibition of the infection by SARS-CoV-2. Infection inhibition coincided with a significant decrease in ACE2 mRNA expression levels. These data suggest that L-carnitine tartrate should be tested with appropriate trials in humans for the possibility to limit SARS-CoV-2 infection.
Highlights • We evaluated Ad26 and Ad35 vectors expressing the RSV fusion protein as a RSV vaccine. • Induction of potent humoral and cellular immune responses in immunized mice. • Durable protective ...immunity against RSV A and B in immunized cotton rats. • No signs of enhanced disease, not even after breakthrough infection in animals that received a suboptimal vaccine dose.
Monoclonal antibodies (mAbs) are among the fastest growing and most effective therapies for myriad diseases. Multispecific antibodies are an emerging class of novel therapeutics that can target more ...than one tumor- or immune-associated modulators per molecule. The combination of different binding affinities and target classes, such as soluble or membrane-bound antigens, within multispecific antibodies confers unique pharmacokinetic (PK) properties. Numerous factors affect an antibody’s PK, with affinity to the neonatal Fc receptor (FcRn) a key determinant of half-life. Recent work has demonstrated the potential for humanized FcRn transgenic mice to predict the PK of mAbs in humans. However, such work has not been extended to multispecific antibodies. We engineered mAbs and multispecific antibodies with various Fc modifications to enhance antibody performance. PK analyses in humanized FcRn transgenic mouse (homozygous Tg32 and Tg276) and non-human primate (NHP) models showed that FcRn-binding mutations improved the plasma half-lives of the engineered mAbs and multispecific antibodies, while glycan engineering to eliminate effector function did not affect the PK compared with wild-type controls. Furthermore, results suggest that the homozygous Tg32 mouse model can replace NHP models to differentiate PK of variants during lead optimization, not only for wild-type mAbs but also for Fc-engineered mAbs and multispecific antibodies. This Tg32-mouse model would enable prediction of half-life and linear clearance of mAbs and multispecific antibodies in NHPs to guide the design of further pharmacology/safety studies in this species. The allometric exponent for clearance scaling from Tg32 mice to NHPs was estimated to be 0.91 for all antibodies.
Despite the significant therapeutic advances provided by immune-checkpoint blockade and chimeric antigen receptor T cell treatments, many malignancies remain unresponsive to immunotherapy. Bispecific ...antibodies targeting tumor antigens and activating T cell receptor signaling have shown some clinical efficacy; however, providing co-stimulatory signals may improve T cell responses against tumors. Here, we developed a trispecific antibody that interacts with CD38, CD3 and CD28 to enhance both T cell activation and tumor targeting. The engagement of both CD3 and CD28 affords efficient T cell stimulation, whereas the anti-CD38 domain directs T cells to myeloma cells, as well as to certain lymphomas and leukemias. In vivo administration of this antibody suppressed myeloma growth in a humanized mouse model and also stimulated memory/effector T cell proliferation and reduced regulatory T cells in non-human primates at well-tolerated doses. Collectively, trispecific antibodies represent a promising platform for cancer immunotherapy.
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