5 ms·

Some thoughts on this white paper, with the caveat that I'm not sure how much of what is discussed they have done and how much of it is what they are planning t

by rgejman 13y ago

Some thoughts on this white paper, with the caveat that I'm not sure how much of what is discussed they have done and how much of it is what they are planning to do. The white paper is light on details and I re-iterate my appeal for them to release their data (at least in summary form). My apologies for some of the technical language--I want to write this first and then I can clarify the hard stuff (or you can google it) This vaccine relies on inducing immunity to an HIV peptide* (i.e. a ~9 amino acid cleavage product of an HIV protein) that is predicted to bind to HLA molecules. At first blush, this sounds like a great idea--let's immunize people to the very thing that the immune system is supposed to recognize as bad! Unfortunately, this has been tried lots of times and usually doesn't work very well, if at all. It's been tried in cancer, it's been tried in HIV, it's been tried in practically any system you can imagine. I'm not saying that peptide vaccines don't ever work (hell, my lab has worked on one)--I'm just saying that they have had lots of promise and limited successes. In fact, animals and patients have been immunized to many cleavage products of many cancer associated antigens to little, if any, effect—or effects in animals but not in humans. We can hem and haw all day about what the specific studies show, but suffice it to say that peptide vaccines are an old idea. Perhaps Immunity will get lucky here, but I'd be surprised if there isn't a lab somewhere that has tried immunizing animals to every single breakdown product of HIV proteins already. Immunity's white paper says that their putatively immunogenic human peptide cannot be tested in animal models because it will only bind to human HLA. So they are planning to use a mouse-analog of the human peptide to do their animal testing (or have already done this?). That is, they are planning to use (or maybe have already used?) a completely different peptide (probably 1-3 amino acids different from the human version) in animal studies than what they would use in patients. This may be a significant difference... or it might not be. There's no way to tell a priori. A more classical and IMO better approach would be to identify T cell receptor clones from patients with HIV (or without HIV) that bind to these peptides (using tetramer staining, phage display or some other high-throughput technology), demonstrate that humans are capable of creating T cells that recognize their putatively immunogenic peptide followed by T cell killing assays on cells presenting their peptide of interest. There are other approaches, but that is a commonly used one in the field. * in some places the white paper says "peptides" and in other it says "peptide" so it's not clear if we are talking about 1 peptide or multiple. I think they are mostly talking about multiple peptides, because they want to immunize people no matter their HLA type. Different HLA types bind to different peptides. So if you have HLA A02 you will bind different peptides than if you have HLA A24... and so on for all the different HLA types.

midas007 13y ago
If it were possible, how long / $ would it take to make a transgenic mouse model with the human gene(s)?
- rgejman 13y ago
  There are a lot of moving parts, so it's really hard for me to estimate the cost here. It's done somewhat routinely in some institutions (although it is very, very expensive). You first need to make humanize mice (i.e. mice with human immune systems). Luckily we can make those by taking NOD/SCID mice (an [expensive] immunodeficient mouse line) and then colonize them with human hematopoietic stem cells from a human donor to reconstitue the immune system. Then you have to do a lot of experiments to make sure your humanized mice can mount immune responses. Then, you can test your peptide and see if your humanized mice will make CD8 T cells to your peptide... Finally, you can infect your mice with HIV (now that you have a humanized immune system) and see how your vaccinated vs. unvaccinated mice fare. I have no idea what the downsides of this approach are because I don't work on HIV or with humanized mice--but mice ain't people. So after all that work you'd have shed limited light on what would happen in real people. I would argue that a better approach is to see whether HIV patients have actually made CD8 T cells against these antigens. This can be done more inexpensively and would give you pretty good evidence that your peptide is immunogenic in real people.
reidrubsamen 13y ago
Hi there, Reid from Immunity Project. Thanks for the great question! Would love to talk with you off line about your research, by the way. 1. We have successfully gotten an immune response with memory (by elispot) after a single dose of the PLGA microspheres containing one or two peptides when combined with TLR-4 (MPLA) and TLR-9 (CpG) agonists. We used H2d restricted epitopes to do the study in C57BL/6 mice – this study is done and in the PRJ review process. We are being careful about posting the results in the event we need to re-submit to a journal who would get heartburn if they saw the data posted. 2. We are raising money now to essentially repeat the experiment (on a smaller scale because we think we understand the optimal formulation configuration now) in C57BL/6 NOG mice (with human PBMCs grafted in from a donor with known HLA type). The new experiment starts off looking like the experiment in (1) above: intradermal tail injection, wait 14 days, sacrifice, get the spleen, confirm immune response to peptide target by flurospot. The next part is new: separate CD8 from CD4 cells (from the mouse spleen), infect the CD4 cells with HIV, see if the vaccination attempt was good enough to see p24 antigen suppression and/or a change in the CD4 counts (all in-vitro). We can finish this study in a couple months, assuming the crowd funding keeps going well and we start in a couple weeks. We will use a different mechanism to publish our paper around this experiment so that we can get it out right away in a fashion that will lead to peer review and open access (We just learned about peerj.com – thoughts on that?). Looking forward to hearing your thoughts on our approach.

by rgejman 13y ago

midas007 13y ago

If it were possible, how long / $ would it take to make a transgenic mouse model with the human gene(s)?

rgejman 13y ago
There are a lot of moving parts, so it's really hard for me to estimate the cost here. It's done somewhat routinely in some institutions (although it is very, very expensive). You first need to make humanize mice (i.e. mice with human immune systems). Luckily we can make those by taking NOD/SCID mice (an [expensive] immunodeficient mouse line) and then colonize them with human hematopoietic stem cells from a human donor to reconstitue the immune system. Then you have to do a lot of experiments to make sure your humanized mice can mount immune responses. Then, you can test your peptide and see if your humanized mice will make CD8 T cells to your peptide... Finally, you can infect your mice with HIV (now that you have a humanized immune system) and see how your vaccinated vs. unvaccinated mice fare. I have no idea what the downsides of this approach are because I don't work on HIV or with humanized mice--but mice ain't people. So after all that work you'd have shed limited light on what would happen in real people. I would argue that a better approach is to see whether HIV patients have actually made CD8 T cells against these antigens. This can be done more inexpensively and would give you pretty good evidence that your peptide is immunogenic in real people.

reidrubsamen 13y ago

Hi there, Reid from Immunity Project. Thanks for the great question! Would love to talk with you off line about your research, by the way. 1. We have successfully gotten an immune response with memory (by elispot) after a single dose of the PLGA microspheres containing one or two peptides when combined with TLR-4 (MPLA) and TLR-9 (CpG) agonists. We used H2d restricted epitopes to do the study in C57BL/6 mice – this study is done and in the PRJ review process. We are being careful about posting the results in the event we need to re-submit to a journal who would get heartburn if they saw the data posted. 2. We are raising money now to essentially repeat the experiment (on a smaller scale because we think we understand the optimal formulation configuration now) in C57BL/6 NOG mice (with human PBMCs grafted in from a donor with known HLA type). The new experiment starts off looking like the experiment in (1) above: intradermal tail injection, wait 14 days, sacrifice, get the spleen, confirm immune response to peptide target by flurospot. The next part is new: separate CD8 from CD4 cells (from the mouse spleen), infect the CD4 cells with HIV, see if the vaccination attempt was good enough to see p24 antigen suppression and/or a change in the CD4 counts (all in-vitro). We can finish this study in a couple months, assuming the crowd funding keeps going well and we start in a couple weeks. We will use a different mechanism to publish our paper around this experiment so that we can get it out right away in a fashion that will lead to peer review and open access (We just learned about peerj.com – thoughts on that?). Looking forward to hearing your thoughts on our approach.