Broad-spectrum neutralizing antibodies. A powerful and adapted host response ?

Antibody production by B lymphocytes is a well-known effector mechanism of adaptive immunity. These antibodies perform numerous effector functions that contribute to the phagocytosis of extracellular infectious agents and the destruction of infected cells. Some neutralize the infectious agent by blocking its ability to bind to cells, or by inhibiting the membrane fusion machinery used by viruses to penetrate cells. The higher the affinity of antibodies, the more effective they are. Affinity is determined by the contact zone of antibodies with the antigen, the structure of which depends on somatic genetic modifications; the most favorable - resulting in increased affinity for the antigen - are selected during the immune response. Based on these principles, the existence of broad-spectrum neutralizing antibodies capable of neutralizing viral particles by recognition of the binding site or other regions of functional importance and conserved between viral strains has been demonstrated. These antibodies are of high affinity, which implies that the B lymphocytes that produce them have undergone several cycles of somatic mutation and selection, requiring a long time of the order of two to four years. Repeated stimulation with different viruses (e.g. influenza viruses express hemagglutinin H1 then H3) is likely to generate such neutralizing antibodies to numerous viral strains. Such antibodies have been demonstrated in humans against influenza viruses, HIV, respiratory viruses, arboviruses, cytomegalovirus and many others. The practical value of these antibodies lies in their possible use in serotherapy, as currently tested for HIV infection, or as a basis for identifying antigens useful in vaccination (current research efforts concern influenza viruses: towards a universal vaccine? or arboviruses (zika, dengue...)).