Immunoglobulines intraveineuses dans les maladies auto-immunes et inflammatoires : au-delà d’une simple substitution

“Lost sugars” — reality of their biological and medical applications

The glycan chains attached to cell surfaces or to single proteins are highly dynamic structures with various functions. The glycan chains of mammals and of some microorganisms often terminate in sialic acids or α-1,3-galactose. Although these two sugars are completely distinct, there are several similarities in their biological and medical importance. First, one type of sialic acid, N-glycolylneuraminic acid, and the galactose bound by an α-1,3-linkage to LacNAc, that forms an α-gal epitope, were both eliminated in human evolution, resulting in the production of antibodies to these sugars. Both of these evolutionary events have consequences connected with the consumption of foods of mammalian origin, causing medical complications of varying severity. In terms of ageing, sialic acids prevent the clearance of glycoproteins and circulating blood cells, whereas cryptic α-gal epitopes on senescent red blood cells contribute to their removal from circulation. The efficiency of therapeutic proteins can be increased by sialylation. Another common feature is the connection with microorganisms since sialic acids and α-gal epitopes serve as receptors on host cells and can also be expressed on the surfaces of some microorganisms. Whereas, the sialylation of IgG antibodies may help to treat inflammation, the expression of the α-gal epitope on microbial antigens increases the immunogenicity of the corresponding vaccines. Finally, sialic acids and the α-gal epitope have applications in cancer immunotherapy. N-glycolylneuraminic acid is a powerful target for cancer immunotherapy, and the α-gal epitope increases the efficiency of cancer vaccines. The final section of this article contains a brief overview of the methods for oligosaccharide chain synthesis and the characteristics of sialyltransferases and α-1,3-galactosyltransferase.

Natural antibodies against nerve growth factor inhibit in vitro prostate cancer cell metastasis

Prostate cancer is a major cause of death in older men, and bone metastasis is the primary cause of morbidity and mortality in prostate cancer. Prostate is an abundant source of nerve growth factor (NGF) that is secreted by malignant epithelial cells and utilized as an important autocrine factor for growth and metastasis. We previously showed that intravenous gammaglobulin (IVIg) contains natural antibodies against NGF, which inhibit growth and differentiation of the NGF-dependent cell line PC-12. In the present study, we examined the effects of these natural antibodies on in vitro migration or metastasis of two prostate cancer cell lines namely DU-145 and PC-3. Cancer cell migration was assessed using these cell lines in the upper chambers of Matrigel invasion chambers. The effects of IVIg and affinity-purified anti-NGF antibodies on cell migration through membrane into the lower chamber were assessed in dose/response experiments by a colorimetric method. Affinity-purified natural IgG anti-NGF antibody inhibited DU-145 migration by 38% (p = 0.01) and PC-3 migration by 25% (p = 0.02); whereas, a monoclonal anti-NGF antibody inhibited DU-145 migration by 40% (p = 0.01) and PC-3 migration by 37% (p = 0.02), at the same concentration. When IVIg was depleted of NGF-specific IgG by affinity chromatography, there was no significant inhibition of migration of the DU-145 and PC-3 cells at a concentration of 1 mg/well. Removal of the NGF-specific antibody from the IVIg was also demonstrated by a lack of effect on PC-12 cell differentiation. Therefore, IVIg is able to inhibit the migration of prostate cancer cell lines, through Matrigel chambers in vitro, only when the natural NGF-specific antibodies actively are present in IVIg.

Impact of Glycosylation on Effector Functions of Therapeutic IgG

Human IgG has only one conserved glycosylation site located in the Cγ2 domain of the Fc region that accounts for the presence of two sugar moieties per IgG. These IgG sugar cores play a critical role in a number of IgG effector functions. In the present review, we describe the main characteristics of IgG Fc glycosylation and some abnormalities of serum IgG glycosylation. We also discuss how glycosylation impacts on monoclonal antibodies (mAbs) and IVIg effector functions and how these molecules can be engineered. Several therapeutic antibodies have now been engineered to be no- or low-fucose antibodies and are currently tested in clinical trials. They exhibit an increased binding to activating FcγRIIIA and trigger a strong antibody-dependent cell cytotoxicity (ADCC) as compared to their highly-fucosylated counterparts. They represent a new generation of therapeutic antibodies that are likely to show a better clinical efficacy in patients, notably in cancer patients where cytotoxic antibodies are needed.