Intratumoral Injection of α-gal Glycolipids Induces Xenograft-Like Destruction and Conversion of Lesions into Endogenous Vaccines

Abstract

This study describes a novel cancer immunotherapy treatment that exploits the natural anti-Gal Ab to destroy tumor lesions and convert them into an endogenous vaccine targeted to APC via FcγR. Anti-Gal constitutes 1% of immunoglobulins in humans and interacts specifically with α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R). The binding of anti-Gal to α-gal epitopes on pig cells mediates xenograft rejection. The proposed method uses glycolipid micelles with multiple α-gal epitopes (α-gal glycolipids). These glycolipids are extracted from rabbit red cell membranes and are comprised of ceramides with carbohydrate chains containing 5–25 carbohydrates, all capped with α-gal epitopes. Efficacy of this treatment was demonstrated in α1,3-galactosyltransferase knockout mice producing anti-Gal and bearing B16 melanoma or B16/OVA producing OVA as a surrogate tumor Ag. These mice are unique among nonprimate mammals in that, similar to humans, they lack α-gal epitopes and can produce the anti-Gal Ab. Intratumoral injection of α-gal glycolipids results in local inflammation mediated by anti-Gal binding to the multiple α-gal epitopes and activation of complement. These glycolipids spontaneously insert into tumor cell membranes. The binding of anti-Gal to α-gal expressing tumor cells induces the destruction of treated lesions as in anti-Gal-mediated xenograft rejection. Anti-Gal further opsonizes tumor cells within the lesion and, thus, targets them for effective uptake by APC that transport the tumor Ags to draining lymph nodes. APC further cross-present immunogenic tumor Ag peptides and elicit a systemic anti-tumor immune response. Similar intratumoral injection of α-gal glycolipids in humans is likely to induce the destruction of treated lesions and elicit a protective immune response against micrometastases.

The Galα1,3Galβ1,4GlcNAc-R (α-Gal) epitope: A carbohydrate of unique evolution and clinical relevance

“…irradiation, injection of ethanol, or thermal ablation), tumor cells within invisible micrometastases that are usually present in the patients, develop within weeks or months into lethal metastases. We have developed a method to use anti-Gal for the destruction of visible lesions and their conversion into endogenous vaccines [127]. These endogenous vaccines elicit an immune response that can target micrometastatic tumor cells and destroy them.…”

Increased Immunogenicity of Tumor-Associated Antigen, Mucin 1, Engineered to Express α-Gal Epitopes: A Novel Approach to Immunotherapy in Pancreatic Cancer

“…Once anti-Gal binds to α-gal epitopes on the cell, its Fc portion readily binds to FcγR III on dendritic cells and macrophages. This interaction induces effective phagocytosis of the anti-Gal-opsonized cells by APC (20)(21)(22). The α-gal epitopes are absent in humans, but are abundantly synthesized on glycolipids and glycoproteins by the glycosyltransferase enzyme, α1,3galactosyltransferase (α1,3GT) within the Golgi apparatus of cells of nonprimate mammals, prosimians, and in New World monkeys (23).…”

Macrophages Recruitment and Activation by α-gal Nanoparticles Accelerate Regeneration and Can Improve Biomaterials Efficacy in Tissue Engineering

“…Since !-gal glycolipids comprise most of the glycolipids in rabbit red blood cell (RBC) membranes and since these cell membranes are the richest source of !-gal glycolipids in mammals [20][21][22][23], rabbit RBC are a convenient natural source for preparation of !-gal liposomes and !-gal nanoparticles [18,19,24]. For this purpose, glycolipids, phospholipids and cholesterol are extracted from rabbit RBC membranes in a solution of chloroform and methanol [25]. The dried extract is sonicated in saline, using a sonication bath, to generate liposomes (size of 1-10µm) that present multiple !-gal epitopes.…”

“…The illustrated glycolipid has 10 sugar units in its carbohydrate chain and two branches (antennae), each capped with an !-gal epitope. !-Gal glycolipids in rabbit RBC membranes are of various lengths ranging from 5 to 40 carbohydrate units carrying 1-8 branches each capped with an !-gal epitope [22,23,25]. The various components of !-gal nanoparticles are illustrated in Fig.…”