If a patient has been exposed to a particular type of AAV already, their immune system might have developed antibodies that could neutralize the effects of that vector.
How do I know if a patient is already exposed to AAV? cuz after antibodies neutralize AAV the are memory cells that help synthesize antibodies upon re-exposure. So how to confirm if a patient has already exposed to AAV? will they be circulation antibodies even after neutralizing AAV?
For e.g if patient A exposed to AAV and patient B control never exposed to AAV
If I isolate memory B cells from both patients and expose those cells to AAV and check for antibodies against AAV thur ELISA, will that work?
No... antibodies are made by plasma cells, which are from B cells. There are also antibody secreting cells (B cells) in circulating which can be stimulated if you want to look at antibody production. There are memory B cells... but there are also long lived plasma cells. Even the short lived ones can stay around for up to months.
But as for antibody titer, which is what you are asking... in general terms, if a person is exposed to AAV, they should have circulating antibodies. And if they are currently infected, the antibody titer will go up, not down. Only after the infection is cleared and no stimulation is present will you start to see a decrease after about a month or so... For patients... just collect serum and do the antibody titer... that's the easiest way to determine if anyone has been exposed.
Also... I thought adeno virus is so common that most people are exposed to it by childhood. Are there people who have never been exposed to it? You might need to be strain specific to find a naive person...
As for the T cells... T cells are required for T cell dependent antibodies. One of the major roles for T cells is to push for isotype switching among a host of other things.
@Shen-An Hwang
Plasma cell are differentiated cells from precursors B cells. If they are exposed in childhood will they still have circulation antibodies? This is exactly what I want to know why will antibodies circulates when there is no antigen/virus for a long time. Unless T cell or APC encounter one in the blood stream (if we plan to induce).
"For patients... just collect serum and do the antibody titer... that's the easiest way to determine if anyone has been exposed."
This is to check if they were recently exposed to AAV?. Typically for viral disease say Dengue we see a rise in IgM after a primary infection than IgG keeps circulation for over 60 years. Thus helps in detecting past infection!
In case of AAV can past infection be identified say 10-15 years back.
I agree with Shen-An Hwang, Simple ELISA test will confirm and it also good to have positive ctrl and low limit of detection ELISA assay.
It depends... If you look at childhood vaccination titers.. some last longer than others. And not everyone respond the same, so some have titers for much longer than others. I don't know if anyone has done any studies on how long adeno viral titers last.
As to why some titers last so long... I always assumed that it was long lived plasma cells. I didn't think these cells need much stimulation to keep producing antibodies.
I thought you just wanted to decide whether the patients were ever exposed. Or are you trying to differentiated between patients/subjects who are infected currently versus those that were infected long ago? If you want to induce a recall response to AAV antigen, you can do that too. PBMC culture is probably the easiest, (whole blood should work too...although there might be other considerations that might be needed for these). If you have the antigen that you want, stimulate the PBMC culture with it, and see if you induce antibody production (I haven't tried this yet). With this, you will also have a T cell recall response with cytokine production.
As to if you can detect antibody from an infection years ago... I have no idea. Most of the paper that I've seen often associate presence of titers with age, which from the natural infection stand point makes sense. The only way to do this study is to have medical or vaccine records from that far back and track down the person. There is one study that looked at army trainees. They sort of correlated the increase in lack of vaccine titers to when the adenoviral vaccine was halted...so.. maybe??
https://academic.oup.com/jid/article/178/6/1776/849138
Yes I wanted to decide whether the patients were ever exposed and whether that can be done via circulating antibodies or thru PBMC culture as u said for PBMC I need specific antigen to stimulate AAV to recall response.
I doubt if there will be any circulating antibodies against AAV after 15-20 years?
Okay so plasma cells keep secreting antibodies irrespective of whether the virus neutralized or absent. I though it would just stay dormant in form of memory B cell and get evoked by antigen there after memory B cells differentiate into plasma cell. So they are long-lived plasma cells.
From what I remember, once a plasma cells becomes a plasma cell, I didn't think that they become dormant. Becuase once why they stop, they usually die. And from what I remember, I'm pretty sure plasma cells don't need "stimulation" as we usually define in terms of antigens to keep producing antibodies. They probably require environmental cues such as certain cytokines in the environment...but this is just a guess.
Yes, for the PBMC, you will need the antigen. The reason I say specific is usually for recall we differentiate between strains (most of my work in infectious diseases was with bacteria).
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