A fault in cells that form a key a part of the immune system may be repaired with a pioneering gene editing technique, finds recent research demonstrated in human cells and mice, led by UCL scientists.

Researchers say the study, published in Science Translational Medicine, may lead to recent treatments for a rare disease of the white blood cells that normally help to regulate the immune system – referred to as regulatory T cells – and those who protect the body from repeat infections and cancer – referred to as effector T cells.

Patients with the condition, referred to as CTLA-4 insufficiency, carry mutations in a gene that cause these T cells to operate abnormally. It leads them to suffer from severe autoimmunity, where their immune system attacks their very own tissues and organs, including their blood cells.

The condition also hampers their immune system’s ‘memory’, meaning patients can struggle to fight off recurring infections by the identical viruses and bacteria. In some cases, it may well also result in lymphomas, a style of blood cancer.

In human cells, using ‘cut’ and ‘paste’ gene editing techniques, using the CRISPR/Cas system, the researchers were capable of goal the faulty gene in T cells taken from patients with CTLA-4 insufficiency and repair the errors. This restored the degrees of CTLA-4 within the cells to those seen in healthy T cells. They were also capable of improve symptoms of the disease in mice with CTLA-4 insufficiency by giving them injections of gene edited (corrected) T cells.

Co-senior writer, Professor Claire Booth, Mahboubian Professor of gene therapy and pediatric immunology at UCL Great Ormond Street Institute of Child Health, said: “It’s really exciting to take into consideration taking this treatment forward to patients. If we are able to improve their symptoms and reduce their risk of getting lymphoproliferative disease this will probably be a significant step forward. This particular paper is vital because we’re using the most recent gene editing techniques to exactly correct these T cells, which is a recent approach in inborn errors of immunity.”

CTLA-4 is a protein produced by T cells that helps to regulate the activity of the immune system. Most individuals carry two working copies of the gene accountable for producing CTLA-4, but those that have just one functional copy produce too little of the protein to sufficiently regulate the immune system.

Currently, the usual treatment for CTLA-4 insufficiency is a bone marrow transplant to interchange the stem cells accountable for producing T cells. But transplants are dangerous and require high doses of chemotherapy and plenty of weeks in hospital. Older patients with CTLA-4 insufficiency are typically not well enough to tolerate the transplant procedure.

Professor Booth said: “Our approach has many positive facets. By correcting the patient’s T cells, we expect it may well improve lots of the symptoms of the disease, similtaneously being much less toxic than a bone marrow transplant. Collecting the T cells is simpler and, correcting the T cells is simpler. With this approach the period of time in hospital the patients would wish could be far less.”

The gene editing approach, developed by the UCL researchers, uses the Nobel-prize winning gene editing technology CRISPR/Cas9 to focus on and snip the faulty CTLA-4 gene in two. Then a corrected sequence of DNA is delivered to the cell using a modified virus. That is then pasted over the faulty a part of the gene using a cellular DNA repair mechanism referred to as homology-directed repair.

This allowed the researchers to preserve necessary sequences throughout the CTLA-4 gene – referred to as the intron – that allow it to be switched on and off by the cell only when needed.

Genes that play critical roles in controlling immune responses are usually not switched on on a regular basis and are very tightly regulated. The technique we now have used allows us to depart the natural (endogenous) mechanisms controlling gene expression intact, similtaneously correcting the error within the gene itself.”

Professor Emma Morris, Co-Senior Writer, Professor of Clinical Cell and Gene Therapy and Director of UCL’s Division of Infection and Immunity

The study was led by Dr Thomas Fox, a Wellcome Trust Clinical PhD Fellow at UCL, and built on work by Dr Pietro Genovese at Dana-Farber/Boston Kid’s Cancer and Blood Disorder Center in Boston, Massachusetts, who’s one among the authors on the study.

Although CTLA-4 insufficiency is rare, the research team say the gene editing therapy they’ve developed for tackling the disease might be a proof of principle of their approach that might be adapted to tackle other conditions.

Professor Morris added: “It is a way of correcting genetic mutations that would potentially be applicable for other diseases. The larger picture is it allows us to correct genes which can be dysregulated or overactive, but in addition allows us to grasp rather more about gene expression and gene regulation.”

Source:

University College London

Journal reference:

Fox, T.A., et al. (2022) Therapeutic gene editing of T cells to correct CTLA-4 insufficiency. Science Translational Medicine. doi.org/10.1126/scitranslmed.abn5811.