Anti-cardiolipin and anti-phosphatidylglycerol antibodies prepared against bacterial phospholipids

Liposomes: from August Wassermann to vaccines against COVID-19

Background and Purpose

The development of vaccines against the SARS-CoV-2 virus has become a big challenge for many countries in 2020-2022. mRNA vaccines were shown to be effective and safe and have been widely used worldwide in the fight against the COVID-19 pandemic. The fundamental factor in creating mRNA vaccines, which ensures effective delivery of mRNA to the host cells, is the composition of lipid nanoparticles, namely the presence of ionized charged lipids, which ensures the binding of mRNA molecules. However, the significant role of liposomes in the development of liposomal vaccines and identification of immunochemical reactions involving lipids should be assessed in the context of the development of the pioneering idea of August Wassermann about the use of liposomal antigens in the diagnosis and immunoprophylaxis of serious human diseases.

Experimental Approach

The review is devoted to the use of liposomal antigens as antigen-delivery systems for diagnosis and immunoprophylaxis.

Key Results

Studies of cardiolipin antigen in serodiagnosis of syphilis became the foundation of antibodies in diagnosing various infectious diseases and pathological conditions, such as tuberculosis, lupus erythematosus, COVID-19, borreliosis, etc. Identification of antiphospholipid antibodies (mainly anticardiolipin) and today is the most important diagnostic tool for antiphospholipid syndrome.

Conclusion

The liposomal system first proposed in 1906 for the diagnosis of syphilis evolved more than a century later into mRNA vaccines, which are used today in the fight against the COVID-19 pandemic.

Demonstration of high specificity antibodies against phosphatidylserine

Anti-phosphatidylserine antibodies were raised in rabbits immunized with phosphatidylserine-polyacrylamide gels and with phosphatidylserine-cytochrome c vesicles. A solid-phase immunoenzymatic assay (ELISA) was developed to study the immune serum. The optimal conditions were defined and the technique used to obtain quantitative results. The anti-phosphatidylserine serum diluted to 1/1000 was tested against several phospholipids and was found to be highly specific to phosphatidylserine. This represents the first experimental demonstration of the specificity of antibodies raised against phosphatidylserine.

The structural specificity of anti-phospholipid antibodies in autoimmune disease

Antibodies to phospholipids represent a unique set of incompletely characterized antibodies prevalent in patients with systemic lupus erythematosus and related autoimmune disorders. Little is known concerning their induction and pathogenesis. Here we provide an overview of what is currently known about these antibodies and explore the possibility that they interact with and are perhaps specific for unusual lipid structures. Particular attention is given to the physical chemical nature and phase behaviour of associated putative lipid antigens. This analysis suggests that alterations in the phospholipid architecture of cell membranes may play an important role in the immunoregulation of autoimmunity.

Immunological properties of glycolipids from membranes of Acholeplasma laidlawii

Glycolipids, the predominant class of lipids in the membranes of Acholeplasma laidlawii, are the haptenic determinants that react with anti-A. Laidlawii serum to fix complement. The predominant complement-fixing activity of the membrane glycolipids was associated with the monoglucoysyl diglyceride, diglucosyl diglyceride, glycerlphosphoryl diglucosyl diglyceride (GPDD), and an unknown lipid B, which did not react with ninhydrin but release glucose and glycerol and traces of phosphorus upon hydrolysis. The glycolipids monoglucosyl diglyceride and diglucosyl diglyceride or GPDD and unknown lipid B were paired as a result of their cross-reactions with selective antisera prepared with the aid of reconstituted membrane complexes containing membrane lipids. Reconstituted membrane complexes assembled from [14C]monoglucosyl diglyceride and delipidated membrane proteins gave optimal complement fixation titers before saturation of the complexes with the ]14C]monoglucosyl diglyceride. The phosphoglycolipid of the membrane, GPDD, was anticomplementary as a pure lipid, a cholesterol liposome, and a reconstituted membrane complex. This anticomplementary activity, which was caused by 3 mug of pure GPDD, affected both human and guinea pig complement. Although human C1, C4, C3, and C5 were not inhibited by GPDD, C2 was inhibited 10-fold by reconstituted membrane complexes containing 150 mug of GPDD. A role for this phosphoglycolipid is discussed in the hypothetical mechanism of inhibition of C2 attachment to SAC1, 4 sites.