Appendix 26. ABO Polymorphism & Infectious Disease Susceptibility

ABO Polymorphism & Disease Susceptibility

Infectious Diseases (1)

Genetic polymorphisms may have played a critical role in defending humans against pathogen invasion. A classical example on how variability is of such importance is the major histo-compatility complex (MHC) genes, which encode for the proteins that present peptide-antigens to T-cells.  Another example is the ABO polymorphism which specifies the end product of specific oligosaccharide antigens. Because ABH antigens are expressed on the surface of various types of cells and are also secreted, differential interactions with infectious pathogens have been suggested, in the past, by association studies and by binding experiments in recent years. Pathogens may have carbohydrate-binding proteins, glycosyltransferases, and/or glycosidases that recognize and bind to ABH antigens, and the host’s ABO phenotype may potentially affect the pathogen adhesion and invasion.  It may also change the constituency of resident bacterial flora in the intestine, and modify the immune response of the host. Additionally, blood group-like antigens are present on some bacteria, and they may interact with host proteins with carbohydrate-binding capacity, such as selectins, galectins, and siglecs.  They may also interact with naturally occurring antibodies.

A.E. Mourant summarized previous results of association studies of diseases, including infectious diseases, with ABO blood group polymorphism in the Oxford Monographs on Medical Genetics (Blood Groups and Diseases: A study of associations of diseases with blood groups and other polymorphisms).

Higher incidences of infection with malaria parasites (in A individuals), plague (O), and smallpox (A) were mentioned in the article.

Relatively recently, differential susceptibility towards Noroviruses has been reported among individuals with different ABO phenotypes. Noroviruses are the leading cause of relatively mild nonbacterial, acute gastroenteritis among adults and are responsible for numerous outbreaks. Noroviruses bind type-1 H antigens, and individuals with O phenotype are more likely to be infected by the viruses, whereas those with B phenotype have decreased risk of infection although different strains exhibit different binding patterns and susceptibility.

Another well-characterized example is Helicobacter pylori. This bacterium can bind to the Lewis b (Leb) oligosaccharide structure, and therefore, infects more readily individuals with certain Lewis and ABO phenotypes. However, it should be mentioned that various strains of H. pylori also use certain sialoglycoconjugates that are unrelated to Lewis or ABO antigens, as receptors when they bind host cells. The routes of infection are not as simple as they were first imagined.

Appendix 27. ABO Polymorphism & Infectious Disease Susceptibility-2

Molecular genetic basis of the blood group ABO system

