Moderna Vaccine and the Immune Response: How Vaccines Work
Influenza vaccines are ready to trigger an immune reaction by mimicking virus infection. They're usually manufactured using inactivated or killed virus particles.
Taken from various circulating influenza strains. Inactive
fractioned viral components contain the sub-Varian particles hemagglutinin HA
and neuraminidase NA.
Photo by Artem Podrez |
In Canada, influenza vaccines are administered via
intramuscular injection. These fractioned particles containing the foreign
antigens hemagglutinin and neuraminidase are released from the vaccine into the
bloodstream.
There they are met with an immune response mediated by
various immune cells, including macrophages T lymphocytes or T-cells and B
lymphocytes or B-cells.
A major mechanism of action involves macrophage phagocytosis
of hemagglutinin, breaking it into smaller components. After ingestion
macrophages display the hemagglutinin antigen on their surface in combination
with a specific receptor known as the major histocompatibility complex or MHC.
T-cells are now able to recognize and bind foreign antigens
that are associated with the MHC. Upon binding to the MHC receptor, T-cells
become activated and proliferate into either cytotoxic T-cells, regulatory
suppressor T-cells, or helper T-cells.
Activated helper T-cells, Express hemagglutinin receptors
specific to the vaccine strand on their surface and play a major role in
antibody generation and memory B-cells activation.
Unlike T-cells, B-cells are able to ingest hemagglutinin
independent of the MHC. Once internalized B-cells processed the hemagglutinin
antigen and presented on their surface in combination with an MHC
When activated helper t-cells interact with activated B-cells
expressing antigen MHC receptors. They begin secreting lymphokines which have
several effects. Lymphokines trigger activated B-cell proliferation which leads
to either their differentiation into memory B-cells or into plasma cells.
Plasma cells produce hemagglutinin antibodies specific to the
strain of influenza contained in the vaccine. Memory B-cells aid in future
immune response when exposed to an active influenza virus.
When an infected host sneezes towards an uninfected person
the nasopharynx is exposed to aerosol droplets containing whole live influenza
virus. Once inhaled the influenza virus attempts viral colonization of
nasopharyngeal epithelial cells.
Assuming that the vaccine strain matches that of the live
virus. Hemagglutinin antibodies block the viral attachment of live influenza
virus to host epithelial cells and overall disease is either avoided or
diminished in severity.