Is it possible to engineer Foxp3+ Tregs from primary T cells?

The most recent paper that asserts they can do it is presented here. It appeared in the journal Science Translational Medicine. This journal is run by Science and is fairly reputable. This research team even established a new biotech company to commercialize their strategy because they are so certain of their data. I’m going to look at how credible their claims are.

In order to introduce a new promoter into the Foxp3 gene in an in vitro activated T cell, they combined specific nuclease ( TALEN ) and virus ( AAV6 ). These were referred to as Tregs edTreg.

the addition of an MND promoter

In an in vitro stimulation assay, the edTregs showed very similar functionality to that found in thymus-derived Treg ( tTrg ) cells, such as no or limited expression of IL-2 and other cytokines. & nbsp,

In a procreation assay, the edTregs were suppressive toward effector T cells, as was to be anticipated from tTrGs. Additionally, since edTregs from IPEX individuals with a defective Foxp3 gene did not exhibit suppression, this crucial function required the endogenous activity of Foxc3.

procreation assay

However, edTregs in the Treg-specific demethylated region( TSDR ) were noticeably different from tTrg levels. The key point is that it is now widely acknowledged that specific and selective epigenetic modification both inside and outside of the Foxp3 gene is necessary to establish Treg identity. However, edTregs conducted in vitro assays and behaved as real tTreds. & nbsp,

How does in vivo work? The plot becomes a little bit hazy at that point. To evaluate edTregs in vivo, the authors used two models. First, they co – transferred edTregs with effector T cells into immunodeficient mice to assess if edTregs could prevent graft versus host disease( GvHD ). They do see reduction of mice mortality with edTregs.

However, there are some inconsistency between experiments describing GvHD model. In one set of experiments it produced 100 % lethality by day 21( see below, red line) while in other set of experiments it produced only 20 % lethality( see above, red line ). & nbsp,

Such inconsistency casts doubts about edTregs ability to inhibit effector T cells in vivo and could explain why the authors did not see much difference in GvHD scores with or without edTregs( see below ).

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This could also explain why the authors did not see improvement in brain inflammation in mice EAE model when co – transferring antigen – specific edTregs with effector T cells.

In summary, this paper has done a lot of interesting in vitro work trying to convince us that their edTregs work as intended. However, in vivo work lacks consistency. It is not surprising. It has been known for some time now that Tregs behave differently in vitro vs. in vivo. Suppression in vivo appears to be strictly antigen – specific phenomenon unlike in vitro where it could be observed antigen – nonspecific manner( even though Treg activation in itself still require presence of cognate antigen ). & nbsp,

posted by David Usharauli

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