In the case of intracellular pathogens, an exclusive humoral immune response is ineffective.
Subsequently, the protein is broken down at the proteasome into short fragments (peptides) that are imported into the endoplasmic reticulum via the transporter associated with antigen processing, allowing them to bind to MHCI-molecules that are subsequently secreted to the cell surface.
The presentation of the peptides on MHC-I complexes on the cell surface is necessary for a cellular immune response.
[5][6] The first use of a viral vector for vaccination – a Modified Vaccinia Ankara Virus expressing HBsAg – was published by Bernard Moss and colleagues.
Viral vectors had previously been approved as ebola vaccines.