Improved production by domain inversion of single-chain Fv antibody fragment against high molecular weight proteoglycan for the radioimmunotargeting of melanoma

Bringing cell therapy to tumors: considerations for optimal CAR binder design

Chimeric antigen receptor (CAR)-T cells have revolutionized the immunotherapy of B-cell malignancies and are poised to expand the range of their impact across a broad range of oncology and non-oncology indications. Critical to the success of a given CAR is the choice of binding domain, as this is the key driver for specificity and plays an important role (along with the rest of the CAR structure) in determining efficacy, potency and durability of the cell therapy. While antibodies have proven to be effective sources of CAR binding domains, it has become apparent that the desired attributes for a CAR binding domain do differ from those of a recombinant antibody. This review will address key factors that need to be considered in choosing the optimal binding domain for a given CAR and how binder properties influence and are influenced by the rest of the CAR.

Comparative assessment of the VH-VL and VL-VH orientations of single-chain variable fragments of scorpion toxin-neutralizing antibodies

The present study evaluated the effect of the change in the orientation of the VH-VL variable domains to VL-VH on the physicochemical and functional properties of two scorpion toxin-neutralizing scFvs. The results showed that the level of expression of proteins obtained from the periplasm of E. coli is the factor mainly affected, either with an increase or decrease in the amount of protein recovered. Likewise, the functional recognition activity in the presence of a denaturing agent showed slight variations in the two orientations. In contrast, recognition and biological activity (neutralizing capacity) are maintained. At the interaction level, the change marginally modified the kinetic association and dissociation constants without significantly modifying the value of the affinity constants. Similarly, it was observed that the thermodynamic stability of the proteins did not show significant variations either. These results contrast with some reports of the effect of changing the orientation of domains, suggesting that it is not possible to predict which orientation of the variable domains of an scFv is more favorable or if they are equivalent, as in the case of scFvs previously matured by directed evolution techniques.

Expression of V(H)-linker-V(L) orientation-dependent single-chain Fv antibody fragment derived from hybridoma 2E6 against aflatoxin B1 in Escherichia coli

Aflatoxin B1 (AFB1) is a toxic secondary metabolic product, which threatens human and animal health. Antibody is a key factor for immunoassay against toxic stuff like AFB1, and single-chain Fv antibody fragment (scFv) has become a popular format of genetically engineered antibody. In this study, four hybridoma cell lines against AFB1 were obtained, and then scFvs 2E6 derived from hybridoma cell line 2E6 were constructed in different V(H)/V(L) orientations. Subsequently, scFvs 2E6 were expressed in E. coli BL21(DE3) mainly in the form of inclusion body. SDS-PAGE, Western blot and ELISA were employed to characterize scFvs 2E6. The results revealed that the yield of inclusion body of scFvs 2E6 in either V(H)/V(L) orientation was similar; however, only the scFv in V(H)-linker-V(L) orientation showed anti-AFB1 bioactivity after refolding. The present study underscores the importance of choosing optimal V(H)/V(L) orientation for scFv construction, and scFv may be favorable for immunoassays in food industry.

Anatomical and molecular imaging of skin cancer

Skin cancer is the most common form of cancer types. It is generally divided into two categories: melanoma (∼ 5%) and nonmelanoma (∼ 95%), which can be further categorized into basal cell carcinoma, squamous cell carcinoma, and some rare skin cancer types. Biopsy is still the gold standard for skin cancer evaluation in the clinic. Various anatomical imaging techniques have been used to evaluate different types of skin cancer lesions, including laser scanning confocal microscopy, optical coherence tomography, high-frequency ultrasound, terahertz pulsed imaging, magnetic resonance imaging, and some other recently developed techniques such as photoacoustic microscopy. However, anatomical imaging alone may not be sufficient in guiding skin cancer diagnosis and therapy. Over the last decade, various molecular imaging techniques (in particular single photon emission computed tomography and positron emission tomography) have been investigated for skin cancer imaging. The pathways or molecular targets that have been studied include glucose metabolism, integrin α_vβ₃, melanocortin-1 receptor, high molecular weight melanoma-associated antigen, and several other molecular markers. Preclinical molecular imaging is thriving all over the world, while clinical molecular imaging has not lived up to the expectations because of slow bench-to-bedside translation. It is likely that this situation will change in the near future and molecular imaging will truly play an important role in personalized medicine of melanoma patients.

Isolation of human single chain variable fragment antibodies against specific sperm antigens for immunocontraceptive development

BACKGROUND

Contraceptive vaccines can provide valuable alternatives to current methods of contraception. We describe here the development of sperm-reactive human single chain variable fragment (scFv) antibodies of defined sperm specificity for immunocontraception.

METHODS

Peripheral blood leukocytes (PBL) from antisperm antibody-positive immunoinfertile and vasectomized men were activated with human sperm antigens in vitro, and the complementary DNA prepared and PCR-amplified using primers based on all the variable regions of heavy and light chains of immunoglobulins. The scFv repertoire was cloned into pCANTAB5E vector to create a human scFv antibody library.

RESULTS

Panning of the library against specific sperm antigens yielded several clones, and the four strongest reactive were selected for further analysis. These clones had novel sequences with unique complementarity-determining regions. ScFv antibodies were expressed, purified and analyzed for human sperm reactivity and effect on human sperm function. AFA-1 and FAB-7 scFv antibodies both reacted with fertilization antigen-1 antigen, but against different epitopes. YLP20 antibody reacted with the expected human sperm protein of 48 +/- 5 kDa. The fourth antibody, AS16, reacted with an 18 kDa sperm protein and seems to be a human homologue of the mouse monoclonal recombinant antisperm antibody that causes sperm agglutination. All these antibodies inhibited human sperm function.

CONCLUSIONS

This is the first study to report the use of phage display technology to obtain antisperm scFv antibodies of defined antigen specificity. These antibodies will find clinical applications in the development of novel immunocontraceptives, and specific diagnostics for immunoinfertility.

Monospecific bivalent scFv-SH: effects of linker length and location of an engineered cysteine on production, antigen binding activity and free SH accessibility

Development of tumor targeting pharmaceuticals on a modular platform is an attractive paradigm. Design choices for bispecific (anti-tumor and anti-chelate) pretargeting molecules are increased by the use of scFvs. Because a scFv is monovalent and small in size, its functional affinity and in vivo residence time can be improved through multimerization. ScFv multimers can be covalent or non-covalent. In vivo studies indicate that covalent scFv multimers are preferable. Attachment of scFv modules to scaffolds offers a wide range of possibilities for size and valency. A free thiol introduced at the C terminal end of a scFv (scFv-SH) allows for site-specific covalent attachment to a PEG scaffold without interfering with its antigen (Ag) binding. Although in theory, multimerization of 3 or 4 scFvs can be achieved by direct conjugation, as scFv-SH, to a tri or tetrafunctionalized PEG, it is not a practical option since homogeneous tri and tetrafunctionalized PEG are not readily available. However, the generation of (scFv)(3-4)-PEG molecules through attachment of combinations of di-scFv-SH (tandemly expressed scFvs) and scFv-SH or 2 di-scFv-SH to a bifunctional PEG is a sound approach that also allows for better control of the scFv-PEG conjugate molecular composition. Optimization of the molecular format of the di-scFv-SH module for production as soluble proteins in E. coli, Ag binding and conjugation is reported in this study. ScFvs in the VH-VL format were used for the di-scFv constructs since Fv domain inversion to VL-VH, while not yielding more protein, also abolished Ag binding. The effects on production yield, Ag binding and conjugation potential of the scFv joining linker length and the presence and location of an engineered cysteine were assessed in vitro. Our data indicate that for di-scFv-SH, an increase of the scFv joining linker length results in higher production and better Ag binding; a 20 aa long linker (G(4)S)(4) was the longest linker tested. For the engineered cysteine, three locations were tested; within the scFv joining linker, at the C terminus upstream of the E Tag and as the carboxy terminal aa. The accessibility of the free SH assessed by conjugation of di-scFv-SH to HRP-Mal demonstrated that di-scFv-HRP conjugates are formed with comparable efficiencies when the cysteine is located at the scFv carboxy end. This empirical work provides a framework for the development of bispecific scFv multimers via site-specific attachment of scFv-SH and di-scFv-SH modules to a scaffold.