Re: what is a subimmunogenic dose and primer dose in vaccination?

Vaccination in a nutshell is the controlled activation of the immune system with defined biomolecules (usually peptides) or attenuated microbes to generate specific, long-lasting immunity. Often, adjuvants (1) are also added to stimulate the antigen- presenting cells, which collect and deliver antigenic peptides to lymphoid organs where T and B cells await. This intercellular web of interactions and the ensuing selection process determines the extent of activation of the T and B cells, a very small fraction of which will live on to constitute the protective "memory" component of the immune response.

The ideal strategies to ensure a potent, long-lived memory component are still being established. An increasing pool of dedicated immunologists are creating novel vaccines to common infectious diseases as well as self-antigens, such as the ones that are overexpressed in certain cancers. Vaccine delivery is also evolving from the scary long needles of our often nightmarish childhood visits to the physician's office; for example potatoes expressing hepatitis B antigen are being developed to immunize people worldwide via the much more agreeable (and potentially cheaper) oral route (2).

A subimmunogenic dose is one that is below the amount needed to elicit a detectable T or B cell (often measured by serum antibody titer) response. A priming dose is the earliest introduction of antigen into the animal; in other words the first injection of the given vaccine. The major caveat of this definition is that in real life responses always occur to any given perturbation- so the lack of a detectable response could just mean the inability of the detection method to separate signal from noise. Looking for the subtle responses to a subimmunogenic dose might involve purifying rare cells from blood (or biopsy) and gauging their activation using reagents to detect specific proteins via flow cytometry. One could also amplify the signal by using molecular approaches such as single cell RT-PCR, or monitor cell behavior by single-cell imaging techniques such as two-photon microscopy. In any case, using a subimmunogenic dose may be detrimental in that it could elicit tolerance rather than immunity, via immature APCs, regulatory T cells and other mechanisms.

1) See MadSci post 1170830066.Im from Feb 12 22:54:14 2007 on a related subject.
2) Richter LJ, Thanavala Y, Arntzen CJ, Mason HS (2000) Production of hepatitis B surface antigen in transgenic plants for oral immunization Nature Biotechnology 18, 1167 - 1171 doi:10.1038/81153