A team led by the Vall d'Hebron Research Institute (VHIR) has developed a new method to improve the diagnosis of scleroderma. This technique, a pioneer in the study of this disease, allows detecting with great sensitivity the autoantibodies of each patient, which serve as biomarkers of the evolution of the disease and allow a more personalised follow-up. The study, led by Translational Immunology and Systemic Diseases groups at VHIR, has been published in the Journal of Autoimmunity.

Scleroderma is a very heterogeneous autoimmune disease characterised by hardening of the skin and involvement of internal organs. "The determination of autoantibodies is essential both for the diagnosis and for the follow-up of these patients, as they are related to the evolution and severity of the disease", explain Dr. Carmen Pilar Simeón and Dr. Alfredo Guillén, members of the Internal Medicine Department and of the Systemic Autoimmune Diseases area at Vall d'Hebron Hospital and principal investigators of the Systemic Diseases group at VHIR.

Autoantibodies are molecules of the immune system that attack the body's own structures. Currently, there are different techniques and commercial test kits to detect them. However, current commercial techniques have limitations. In addition, there is a lot of variability between patients and the types of autoantibodies they present, which means that, in a high percentage of patients, it is not possible to find these markers and diagnosis and follow-up are more difficult.

A new technique for the detection of autoantibodies

In scleroderma, patients develop autoantibodies that can recognise and attack ribonucleoprotein (RNP) complexes in the patient's own cells. These complexes are structures made up of proteins and RNA molecules that perform essential functions within the cell.

In this study, the VHIR team has used a new technique, called RIP-Seq, to detect with greater precision the RNP to which autoantibodies bind in patients with scleroderma.

How does RIP-Seq work?

This technique is divided into two main steps:

1. RNA immunoprecipitation (RNA IP): In this step, patient sera are used to capture RNP complexes. If the serum contains autoantibodies against any of these complexes, they bind to the corresponding RNP complexes.
2. Massive RNA sequencing: This allows the RNAs of the RNP complexes obtained in the first step to be analysed and precisely identified. This generates a comprehensive map of potential autoantibody targets in scleroderma patients.

This second step is the main novelty of the technique compared to standard methods. The identification of individual RNAs is usually done by less sensitive and less comprehensive techniques. "The use of massive sequencing allows us to directly analyse the RNA and identify its complete sequence in a systematic way. It offers much greater sensitivity and precision and allows us to identify biomarkers that could have gone undetected with other methods", explains Janire Perurena, a specialist in the Immunology Department at Vall d'Hebron University Hospital and researcher in the Translational Immunology group at VHIR.

Towards more specific biomarkers for scleroderma

As Dr Roger Colobran, head of the Translational Immunology group at VHIR, explains, this study represents a breakthrough in the diagnosis of scleroderma, "as it allows the detection of new autoantibodies that may have diagnostic and prognostic value for patients, so that more patients can be monitored much more closely and their survival and quality of life can be improved".

In fact, thanks to the RIP-Seq methodology, this study has identified potential targets for new autoantibodies in scleroderma, which should be validated in subsequent studies. These new autoantibodies may be important for stratifying patients and defining their prognosis. Along these lines, the same group that conducted this study recently discovered the anti-NVL autoantibody in a subgroup of scleroderma patients who are at increased risk of developing cancer.

The study published now has been conducted in collaboration with the Infection and Immunity in Paediatric Patients group at VHIR, the Institute of Parasitology and Biomedicine López-Neyra (IPBLN-CSIC) in Granada, the Príncipe Felipe Research Centre (CIPF) and the University of Bath.