Patients submitted to a procedure that “resets” the immune system were tracked for a year by scientists at a FAPESP-supported research center. Their clinical improvement correlated with renewal of a group of defense cells known as B lymphocytes (image: Colin Behrens/Pixabay)

Published on 02/21/2022

By Karina Ninni  |  Agência FAPESP – Systemic sclerosis affects one in 20,000 people, mainly women aged 30-50. It is a rare and aggressive auto-immune rheumatic disease, in which the replacement of normal tissue with scar tissue causes functional impairment. Among patients with the severe form of the disease, five-year survival rates range from 30% to 50%.

Conventional therapies using immunosuppressive drugs are not very effective, but hematopoietic stem cell (HSC) transplantation has emerged as a promising option. HSCs are multipotent cells that can differentiate into blood cells and immune cells. The mechanisms involved are being studied in Brazil by scientists affiliated with the Center for Cell-Based Therapy (CTC) at the University of São Paulo (USP). In one of their studies, the researchers established the effect of the procedure on the B cell compartment of the immune system (a group of lymphocytes responsible for producing antibodies), correlating it with patient improvement and pointing to other possible future treatment options.

“Systemic sclerosis patients lose what we call immune tolerance, developing autoreactive B and T lymphocytes, which recognize and attack tissue in their own organism. The role of B cells in systemic sclerosis isn’t clearly defined in the literature. We succeeded in discovering a novel action mechanism in HSC transplants whereby B cells play a key role in controlling autoimmunity and permitting remission not long after the treatment,” said Kelen Malmegrim de Farias, a professor at the Ribeirão Preto School of Pharmaceutical Sciences (FCFRP-USP).

“The point is to treat the immune system, which attacks the patient’s organism, and our results are therefore highly promising. It’s a very generic transplant in that it impacts the entire immune system, and it’s also very aggressive, but results like these show that we may be able in future to be more precise in targeting only the cells of interest. This also applies to non-transplant patients treated with immunosuppressive drugs. Knowledge of the action mechanism of each cell involved may enable us to develop more specific therapies,” said rheumatologist Maria Carolina de Oliveira, a professor at the Ribeirão Preto Medical School (FMRP-USP).

Oliveira stressed the gravity of systemic sclerosis. “Patients can’t move, and in many cases can’t even get out of bed. It’s very debilitating,” she said. “The skin thickens on the face and hands, and sometimes on the chest and abdomen. Internal organs may stiffen, including the esophagus, stomach, intestines, kidneys, lungs and heart. When the lungs are affected, the patient has difficulty breathing.”

Malmegrim and Oliveira are members of CTC and co-authors of an article on HSC transplantation published in the journal Rheumatology. The first author is João Rodrigues Lima-Júnior, who has a doctorate from FCFRP-USP in biosciences and biotechnology. 

CTC has been funded since 2000 by FAPESP under its program of Research, Innovation and Dissemination Centers (RIDCs). CTC’s cadre of researchers from USP and the Ribeirão Preto Regional Blood Center includes physicians, biologists, biomedical scientists, pharmacists and veterinarians. The center leads stem cell and cell-based therapy research in Brazil, where it is the only institution with such substantial experience and expertise in transplantation for the treatment of auto-immune diseases, including systemic sclerosis.

Transplants

Irreversible lesions such as “claw hand deformity” due to the disease persist even after an HSC transplant, Oliveira explained, but transplant patients can resume day-to-day activities and live longer.

CTC performs transplants in severe cases involving lung fibrosis and/or widespread skin fibrosis. It has performed some 120 transplants since 2004, with clinical results considered highly positive. “The skin improves and patients can return to work, as well as resuming day-to-day activities like driving, cooking, doing housework, and so on. The lungs and respiratory system stabilize, and the quality of life is enhanced. We already knew about the evidence of clinical improvement, but had yet to discover the mechanisms involved,” Oliveira said.

The transplant is autologous, so no donor is required. “We collect healthy stem cells from the patient and deep-freeze them,” Oliveira said. “The procedure is performed entirely at the Ribeirão Preto Regional Blood Center, where CTC is based. We administer a mixture of immunotherapy and chemotherapy, a combination of drugs that destroys the blood cells and immune cells produced in the bone marrow. We then thaw and re-implant the stem cells. This basically resets the immune system. The stem cells will create new bone marrow, new blood, and a new immune system, which won’t attack the organism any longer.”

Not all systemic sclerosis patients are eligible for HSC transplantation. “The risk is too great in mild cases, which can be treated fairly satisfactorily with immunosuppressants, the most widely used drugs for this purpose,” Oliveira said. “In very severe cases with irreversible lesions, the risk is that the procedure won’t produce any improvement. Selection is one of the hardest parts of the process. Physicians tend to prescribe transplantation for patients who are already severely ill. We need to alert rheumatologists to the importance of diagnosing patients early enough to make HSC transplantation worthwhile. Many professionals still see it as a last resort. Furthermore, because it’s a rare disease, few people have experience in dealing with it and will often mistakenly diagnose lupus or rheumatoid arthritis.” 

The age limit for the transplant at CTC is 60, she added, explaining that rebuilding the immune system takes about two and a half to three years. “We stop giving the patient immunosuppressants, we take great care to avoid infections, and of course, we have to redo all the person’s vaccines. Patient follow-up continues for five years after the procedure,” she said.

Environmental trigger

In their study of B cells, the researchers collected peripheral blood from 22 patients before the transplant and at intervals of 30, 60, 120, 180 and 360 days afterward. “Once we’ve shut down the immune system, we infuse the stem cells, and the hematopoietic and immune systems reinitialize,” Malmegrim said. “B cells, formed in the bone marrow, recover faster than T cells, which we discussed in our first article. One or two months after the transplant, the B cell compartment has already rebounded. In the latest study, reported in Rheumatology, we analyze what happens in the first year after the transplant, assessing the patients after one, two, four months and so on, up to a year afterward, and focusing on B cells.”

The cells were analyzed by flow cytometry (a technique used to examine chemical and physical characteristics of cells or particles in suspension) and functional assays. The biological characteristics of B cells analyzed included cytokine production, signaling pathways, and the suppressive capacity of regulatory B cells. According to Malmegrim, the results showed that B cells are deregulated in systemic sclerosis patients. Before the transplant, there are more memory B cells, which produce the autoantibodies that attack the patient’s tissue, and fewer young B cells, which scientists call naïve as they have not yet learned to recognize antigens that should trigger antibody production.

“Regulatory B cells are important, as they’re responsible for blocking pathogenic immune responses, which can lead to tissue damage,” she said. “Systemic sclerosis patients have fewer regulatory B cells, which are also functionally weakened. After the transplant, the number of these cells rises and their suppressive capacity increases. In addition, the frequency of naïve B cells rises, and that of memory B cells falls.”

Correlation studies conducted at a later stage showed a clinical improvement corresponding to this impact of the transplant on B cells. “It’s only possible to manipulate the patient’s immune system so successfully because auto-immune diseases don’t only involve genetic factors. Autologous transplantation wouldn’t work if they did. There’s always a trigger, which is usually environmental. So there has to be a genetic predisposition and a trigger that sets off the disease. We know very little about the triggers for systemic sclerosis and other auto-immune diseases,” Malmegrim said. 

HSC transplants to treat systemic sclerosis are not on the list of procedures offered by the national health system (SUS) in Brazil or covered by private health insurance plans. For Oliveira, inclusion is a long-term battle. “HSC transplants are considered standard treatment in Europe and the US, where they’re covered by insurance and other health plans,” she said. “Here in Brazil, we’ve fought for inclusion by the SUS. The procedure isn’t expensive. In fact, it can even be considered cheap compared to the cost to public health services if they have to treat systemic sclerosis patients for the rest of their lives, paying for hospital stays, oxygen and so on.”

The article “Autologous hematopoietic stem cell transplantation restores the suppressive capacity of regulatory B cells in systemic sclerosis patients” is at: doi.org/10.1093/rheumatology/keab257.

 

Source: https://agencia.fapesp.br/37988