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Discussion topics from Pandemic Influenza, 2nd Edition
Edited by Jonathan Van-Tam, MBE BmedSci (Hons) BMBS DM FFPH FRSPH, Professor of Health Protection University of Nottingham, UK and Chloe Sellwood, BSc (Hons) PhD FRSPH DipHEP, Pandemic and Seasonal Influenza Resilience Manager, NHS London, UK
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Virology and immunology
L Haaheim and J Oxford
How do antibodies against haemagglutinin (HA) and neuraminidase (NA) differ in the way they interfere with the viral replication cycle?
Antibodies against HA will bind to the virus and prevent it binding to the host cell, i.e. the antibodies are neutralizing. Antibodies to NA will typically block or reduce the release of newly made virus particles from an already infected cell, i.e. these antibodies will dampen the replication of virus and thus reduce the clinical symptoms and how contagious an infected individual is to others.
How do the adamantane and neuraminidase-inhibitor drugs work?
The adamantane drugs interfere with the proton transport function of the M2 protein (the ion channel) located in the viral membrane (hence are known as M2-channel blockers). As a consequence, genetic material from the virus cannot enter the cell and take advantage of the cellular machinery, and the replication cycles come to a halt. The neuraminidase-inhibitor drugs block the function of the viral NA enzyme and thus inhibit the release of newly made virus particles from an already infected cell.
What role does cell mediated immunity play in combating influenza infection?
Cell-mediated immunity will not block the initial infection but rather destroy virus-infected cells. This is a reciprocal cooperation between the humoral (antibody generating) and cellular (cytotoxic T-cells) arms of the immune response, thus strengthening and modifying both.
What is immunological memory?
Immunological memory is the adaptive immunity's ability to respond quicker and stronger to a subsequent stimulation of foreign material. This foreign material can be a new infection with an identical or related virus. When we are âprimed', i.e. have experienced an earlier encounter with an infectious agent or a vaccine, the memory so generated will help us combat a subsequent infection much more efficiently.
"Cross-protective immunity: where immunity to one antigen provides partial or complete protection against similar antigens."