Construction, purification, and immunogenicity of recombinant cystein-cystein type chemokine receptor 5 vaccine

The Role of Natural Antibodies to CC Chemokine Receptor 5 in HIV Infection

The CC chemokine receptor 5 (CCR5) is responsible for immune and inflammatory responses by mediation of chemotactic activity in leukocytes, although it is expressed on different cell types. It has been shown to act as co-receptor for the human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV). Natural reactive antibodies (Abs) recognizing first loop (ECL1) of CCR5 have been detected in several pools of immunoglobulins from healthy donors and from several cohorts of either HIV-exposed but uninfected subjects (ESN) or HIV-infected individuals who control disease progression (LTNP) as well. The reason of development of anti-CCR5 Abs in the absence of autoimmune disease is still unknown; however, the presence of these Abs specific for CCR5 or for other immune receptors and mediators probably is related to homeostasis maintenance. The majority of anti-CCR5 Abs is directed to HIV binding site (N-terminus and ECL2) of the receptor. Conversely, it is well known that ECL1 of CCR5 does not bind HIV; thus, the anti-CCR5 Abs directed to ECL1 elicit a long-lasting internalization of CCR5 but not interfere with HIV binding directly; these Abs block HIV infection in either epithelial cells or CD4+ T lymphocytes and the mechanism differs from those ones described for all other CCR5-specific ligands. The Ab-mediated CCR5 internalization allows the formation of a stable signalosome by interaction of CCR5, β-arrestin2 and ERK1 proteins. The signalosome degradation and the subsequent de novo proteins synthesis determine the CCR5 reappearance on the cell membrane with a very long-lasting kinetics (8 days). The use of monoclonal Abs to CCR5 with particular characteristics and mode of action may represent a novel mode to fight viral infection in either vaccinal or therapeutic strategies.

Production of Human Cu,Zn SOD with Higher Activity and Lower Toxicity in E. coli via Mutation of Free Cysteine Residues

Although, as an antioxidant enzyme, human Cu,Zn superoxide dismutase 1 (hSOD1) can mitigate damage to cell components caused by free radicals generated by aerobic metabolism, large-scale manufacturing and clinical use of hSOD1 are still limited by the challenge of rapid and inexpensive production of high-quality eukaryotic hSOD1 in recombinant forms. We have demonstrated previously that it is a promising strategy to increase the expression levels of soluble hSOD1 so as to increase hSOD1 yields in E. coli. In this study, a wild-type hSOD1 (wtSOD1) and three mutant SOD1s (mhSOD1s), in which free cysteines were substituted with serine, were constructed and their expression in soluble form was measured. Results show that the substitution of Cys111 (mhSOD1/C111S) increased the expression of soluble hSOD1 in E. coli whereas substitution of the internal Cys6 (mhSOD1/C6S) decreased it. Besides, raised levels of soluble expression led to an increase in hSOD1 yields. In addition, mhSOD1/C111S expressed at a higher soluble level showed lower toxicity and stronger whitening and antiradiation activities than those of wtSOD1. Taken together, our data demonstrate that C111S mutation in hSOD1 is an effective strategy to develop new SOD1-associated reagents and that mhSOD1/C111S is a satisfactory candidate for large-scale production.

A Linear Epitope in the N-Terminal Domain of CCR5 and Its Interaction with Antibody

The CCR5 receptor plays a role in several key physiological and pathological processes and is an important therapeutic target. Inhibition of the CCR5 axis by passive or active immunisation offers one very selective strategy for intervention. In this study we define a new linear epitope within the extracellular domain of CCR5 recognised by two independently produced monoclonal antibodies. A short peptide encoding the linear epitope can induce antibodies which recognise the intact receptor when administered colinear with a tetanus toxoid helper T cell epitope. The monoclonal antibody RoAb 13 is shown to bind to both cells and peptide with moderate to high affinity (6x10^8 and 1.2x10⁷ M^-1 respectively), and binding to the peptide is enhanced by sulfation of tyrosines at positions 10 and 14. RoAb13, which has previously been shown to block HIV infection, also blocks migration of monocytes in response to CCR5 binding chemokines and to inflammatory macrophage conditioned medium. A Fab fragment of RoAb13 has been crystallised and a structure of the antibody is reported to 2.1 angstrom resolution.

High level expression, purification and characterization of recombinant CCR5 as a vaccine candidate against HIV

Cysteine-cysteine chemokine receptor type 5 (CCR5) is an important co-receptor for human immunodeficiency virus (HIV) infection and CCR5 neutralizing agents have proven efficient in patients suffering from HIV infection. Here, we expressed and purified various CCR5 vaccines named rCCR5, PADRE-rCCR5, GST-C1 and GST-C2 composed of different epitopes of CCR5. Results showed that vaccines containing multiple epitopes (rCCR5 and PADRE-rCCR5) induced stronger immune responses than single-epitope ones (GST-C1 and GST-C2). In addition, the elicited antibodies can specifically bind CCR5(+) U937 but not CCR5(-) Wish cells. These results demonstrate that the CCR5 vaccines are useful for further research, especially for the in vitro preclinical evaluation of their potential as biological CCR5 neutralizing agents.

HIV blocking antibodies following immunisation with chimaeric peptides coding a short N-terminal sequence of the CCR5 receptor

The chemokine receptor CCR5 is required for cellular entry by many strains of HIV, and provides a potential target for molecules, including antibodies, designed to block HIV transmission. This study investigates a novel approach to stimulate antibodies to CCR5. Rabbits were immunised with chimaeric peptides which encode a short fragment of the N-terminal sequence of CCR5, as well as an unrelated T cell epitope from Tetanus toxoid. Immunisation with these chimaeric peptides generates a strong antibody response which is highly focused on the N-terminal CCR5 sequence. The antibody to the chimaeric peptide containing an N-terminal methionine also recognises the full length CCR5 receptor on the cell surface, albeit at higher concentrations. Further comparison of binding to intact CCR5 with binding to CCR5 peptide suggest that the receptor specific antibody generated represents a very small fragment of the total anti-peptide antibody. These findings are consistent with the hypothesis that the N-terminal peptide in the context of the intact receptor has a different structure to that of the synthetic peptide. Finally, the antibody was able to block HIV infection of macrophages in vitro. Thus results of this study suggest that N-terminal fragments of CCR5 may provide potential immunogens with which to generate blocking antibodies to this receptor, while avoiding the dangers of including T cell auto-epitopes.