Unique aspects of adaptive immunity in camelids and their applications

Members of the Camelidae have unique adaptive immunological features that are not widely observed in other species. All camelids are known to have three distinct IgG isotypes - IgG1, IgG2 and IgG3. While IgG1 has a conventional antibody structure, both IgG2 and IgG3 are devoid of light chains and instead possess hypervariable regions in their heavy chain (VHH), while lacking the typical CH1 domain found in heavy chains. VHH domains are increasingly being utilized as "next generation" antibodies, as they have unique biochemical and structural properties including high pH stability as well as a lower molecular weight allowing for increased tissue penetration. These features of VHH domains offer a number of advantages for both biotechnology and clinical applications and are commonly termed "nanobodies". A second unique aspect of the camelid adaptive response is involves T cell-mediated immunity. Characterization of gamma delta (ꝩδ) T cells in camelid species has found they use somatic hypermutation in their T cell receptor gamma (TRG) and delta (TRD) loci to increase the structural stability of their ꝩδ T receptor. The use of somatic hyper mutation to increase the diversity of their T cell repertoire, is a feature that has not been observed in other mammalian species. In addition, in alpacas there is a unique subset of ꝩδ T cells called Vꝩ9Vδ2 T cells. Activation of these cells is dependent upon phosphoantigen (PAg)-mediated interaction with B7-like butyrophilin molecules (BTN-3). This makes alpacas the first species outside of primates to be identified with this unique subset and activation mechanism. Here we review some fundamentals of camelid adaptive immunity that make them distinct from other vertebrate species and their potential applications to human therapies.

Generation and Characterization of a Functional Nanobody Against Inflammatory Chemokine CXCL10, as a Novel Strategy for the Treatment of Multiple Sclerosis

BACKGROUND & OBJECTIVE

Chemokines and their receptors play a pivotal role in the pathogenesis of various autoimmune diseases such as multiple sclerosis, infectious diseases, and also in cancer metastasis via attraction of the pathogenic immune cells into the inflammation sites.

METHODS

Inflammatory chemokine CXCL10 as a T helper (Th)1-chemokine directs chemotaxis of many cell subsets especially Th1 into the central nervous system (CNS) via its receptor CXCR3 and it has been put forward as a potential therapeutic target in the treatment of multiple sclerosis. Nanobodies are the smallest intact antigen binding fragments derived from heavy chain-only antibodies occurring in camelids with unique biochemical and biophysical features which render them superior to conventional antibodies or antibody fragments. Here, we describe the generation, selection, and characterization of CXCL10-specific Nanobodies from camel immunized with CXCL10. The obtained Nanobodies displayed high affinity towards CXCL10 about 10-11-10-8 M.

RESULTS

Then a Nanobody with the highest affinity named 3Nb12 was selected and investigated as a migration inhibitor of CXCR3+ cells. Chemotaxis assay results showed that 3Nb12 blocked CXCL10- CXCR3 binding and potently inhibited chemotaxis of CXCR3-transfected HEK293T cells.

CONCLUSION

The nanobody 3Nb12 might be a promising specific and powerful blocking agent of CXCL10 function, which can be used for diagnostic, therapeutic and research purposes in MS.

Preparation and characterization of a novel nanobody against T-cell immunoglobulin and mucin-3 (TIM-3)

OBJECTIVES

As T-cell immunoglobulin and mucin domain 3 (TIM-3) is an immune regulatory molecule; its blocking or stimulating could alter the pattern of immune response towards a desired condition. Based on the unique features of nanobodies, we aimed to construct an anti-TIM-3 nanobody as an appropriate tool for manipulating immune responses for future therapeutic purposes.

MATERIALS AND METHODS

We immunized a camel with TIM-3 antigen and then, synthesized a VHH phage: mid library from its B cell's transcriptome using nested PCR. Library selection against TIM-3antigen was performed in three rounds of panning. Using phage-ELISA, the most reactive colonies were selected for sub-cloning in soluble protein expression vectors. The Nanobody was purified and confirmed with a nickel-nitrilotriacetic acid (Ni-NTA) column, SDS-PAGE and Western blotting. A flowcytometric analysis was performed to analyze the binding and biologic activities of theTIM-3 specific nanobody with TIM-3 expressing HL-60 and HEK cell lines.

RESULTS

Specific 15kD band representing for nanobody was observed on the gel and confirmed with Western blotting. The nanobody showed significant specific immune-reactivity against TIM-3 with a relatively high binding affinity. The nanobody significantly suppressed the proliferation of TIM-3 expressing HL-60 cell line.

CONCLUSION

Finally, we successfully prepared a functional anti-humanTIM-3 specific nanobody with a high affinity and an anti-proliferative activity on an AML cell line in vitro.

Nanobodies as Versatile Tools to Understand, Diagnose, Visualize and Treat Cancer

Since their discovery, nanobodies have been used extensively in the fields of research, diagnostics and therapy. These antigen binding fragments, originating from Camelid heavy-chain antibodies, possess unusual hallmarks in terms of (small) size, stability, solubility and specificity, hence allowing cost-effective production and sometimes outperforming monoclonal antibodies. In this review, we evaluate the current status of nanobodies to study, diagnose, visualize or inhibit cancer-specific proteins and processes. Nanobodies are highly adaptable tools for cancer research as they enable specific modulation of targets, enzymatic and non-enzymatic proteins alike. Molecular imaging studies benefit from the rapid, homogeneous tumor accumulation of nanobodies and their fast blood clearance, permitting previously unattainable fast tumor visualization. Moreover, they are endowed with considerable therapeutic potential as inhibitors of receptor-ligand pairs and deliverers of drugs or drug-loaded nanoparticles towards tumors. More in vivo and clinical studies are however eagerly awaited to unleash their full potential.

Recombinant expression and purification of human placental growth factor 1 and specific camel heavy chain polyclonal antibody preparation

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Unlike VEGF, PlGF is dispensable for normal cell development as well as playing various roles in pathological angiogenesis which occurs in tissue ischemia, inflammation, and malignancy. The PlGF-1 has been considered as a potential candidate for the diagnosis and targeting of pathological angiogenesis. Camelidae serum contains an important fraction of functional antibodies, called heavy-chain antibodies (HcAbs) that are naturally devoid of light chains. Camelid HcAbs recognize their cognate antigens by a single variable-domain, referred to as VHH or Nanobody. Here, we describe the expression and purification of recombinant human PlGF-1 (rhPlGF-1). This protein was subsequently used for the preparation of camel heavy chain polyclonal antibody against rhPlGF-1. The recombinant expression plasmid pET-26b-hPlGF-1 was introduced into Escherichia coli BL21 cells to express the rhPlGF-1 protein. Purified rhPlGF-1 was used to immunize camel, the specific reactivity of HcAb was determined with ELISA and western blot. Western blot analysis indicated that the antiserum specifically reacted to the recombinant protein. The rhPlGF-1 protein and its antibody may be used for the development of detection assays needed for clinical research.

Variable fragment of heavy chain antibody against TP region of Hepatitis B Virus polymerase inhibits replication of hepatitis B virus in vitro

AIM: To study a functional variable fragment of heavy chain (VH) antibody against the terminal protein (TP) region of hepatitis B virus (HBV) polymerase (Pol) and its inhibition on the replication of HBV in vitro.

METHODS: The TP region of HBV Pol secreted by the HepG2.2.15 cells was used as an antigen, and the antibodies were selected with protein fragment complementation assay (PCA). The VH antibody gene was cloned into expression vector pZeoSV2(+), and then pZeoSV2(+)-VH was transfected into HepG2.2.15 cells. The contents of HBV DNA in the cells were detected by fluorescent quantitative polymerase chain reaction (FQ-PCR).

RESULTS: Three antibodies against the TP region of HBV were selected. The replication of HBV was markedly inhibited by the anti-TP Pol VH antibodies. The contents of HBV DNA in the pZeoSV2(+)-VH transfected cells (Group C) were significantly higher than those in the non-transfected and pZeoSV2(+) transfected cells (Group A and C)(Supernate: 3.480±0.32 vs 5.268±0.07, 5.105±0.78, P<0.05; Intracellular: 5.718±0.15 vs 7.716±0.74, 7.394±0.97, P<0.05).

CONCLUSION: The anti-TP Pol VH antibodies can inhibit the replication of HBV in HepG2.2.15 cells.