Uso de PCR digital para definir terapéuticas específicas y seguimiento en enfermedades autoinflamatorias / Use of digital PCR to define specific therapeutics and follow-up in autoinflammatory diseases

Las enfermedades autoinflamatorias (AIDs) son un grupo heterogéneo de desórdenes monogénicos o poligénicos, con características de disregulación inmune innata y/o adaptativa, cuyo mecanismo central es la autoinflamación pero también pueden presentarse con autoinmunidad e inmunodeficiencia. En estos últimos años el desarrollo de las tecnologías de secuenciación masiva han provocado una explosión en el descubrimiento de nuevos genes responsables de AIDs monogénicas. Esto remarca la importancia de implementar este tipo de estudios para llegar a un diagnóstico definitivo sobre todo en este grupo de patologías genéticamente muy diversas donde los fenotipos clínicos se solapan. Sin embargo, dada la presencia de variantes de significación incierta (VUS), los resultados pueden no ser concluyentes planteándose la necesidad de desarrollar pruebas funcionales para determinar la patogenicidad de dichas variantes genéticas. En nuestro grupo de trabajo estamos aplicando la PCR digital en gotas (ddPCR), una técnica cuantitativa de 3era generación altamente sensible, especifica y reproducible que no necesita de curvas de calibración, para desarrollar pruebas funcionales que permitan no sólo reclasificar variantes VUS para lograr diagnósticos definitivos sino también estudiar los mecanismos responsables de las principales AIDs que permitan una estratificación de las terapéuticas especificas a aplicar y de esta manera poder contribuir al diagnóstico, tratamiento y seguimiento de nuestros pacientes en forma personalizada. (AU)

Autoinflammatory diseases (AIDs) are a heterogeneous group of monogenic or polygenic disorders, with characteristics of inborn and/or adaptive immune dysregulation, whose central mechanism is autoinflammation but may also present with autoimmunity and immunodeficiency. In recent years the development of massive sequencing technologies has led to an exponential increase in the discovery of new genes responsible for monogenic AIDs. This emphasizes the importance of the implementation of this type of studies to make a definitive diagnosis, especially in this group of genetically very diverse diseases with overlapping clinical phenotypes. However, given the presence of variants of uncertain significance (VUS), the results may not be conclusive, raising the need to develop functional tests to determine the pathogenicity of these genetic variants. In our working group we are applying droplet digital PCR (ddPCR), a highly sensitive, specific and reproducible third generation quantitative technique that does not require calibration curves, to develop functional tests that allow not only to reclassify VUS variants to achieve definitive diagnoses but also to study the mechanisms responsible for the main AIDs that allow for the stratification of specific treatments to be used and thereby contribute to the individualized diagnosis, treatment, and follow-up of our patients (AU)

A 475 years-old founder effect involving IL12RB1: a highly prevalent mutation conferring Mendelian Susceptibility to Mycobacterial Diseases in European descendants.

Mutations in IFNGR1, IFNGR2, IL12RB1, IL12B, STAT1 and NEMO result in a common clinical phenotype known as Mendelian Susceptibility to Mycobacterial Diseases (MSMD). Interleukin-12 receptor beta1 (IL-12Rbeta1) deficiency is the most common genetic etiology for MSMD. Known mutations affecting IL12RB1 are recessively inherited and are associated with null response to both IL-12 and IL-23. Mutation IL12RB1 1623_1624delinsTT was originally described in 5 families from European origin (2 from Germany; 1 from Cyprus, France and Belgium). Interestingly, this same mutation was found in an unexpectedly high prevalence among IL-12Rbeta1 deficient patients in Argentina: 5-out-of-6 individuals born to unrelated families carried this particular change. To determine whether mutation 1623_1624delinsTT represents a DNA mutational hotspot or a founder effect, 34 polymorphic markers internal or proximal to IL12RB1 were studied in the Argentinean and the Belgian patients. A common haplotype spanning 1.45-3.51Mb was shared by all chromosomes carrying mutation 1623_1624delinsTT, and was not detected on 100 control chromosomes. Applying a modified likelihood-based method the age of the most recent common ancestor carrying mutation 1623_1624delinsTT was estimated in 475 years (95% CI, 175-1275), which is the time when the Spaniards initiated the colonization of the Americas. Mutation 1623_1624delinsTT represents the first founder effect described on IL-12Rbeta1, the most frequently affected gene in MSMD, and affecting patients with European ancestors. The reason(s) behind the persistency of this mutation across multiple generations, its relative high prevalence, and any potential selective advantage are yet to be established.

Thirteen years of culture-positive M. bovis-BCG infection in an IL-12Rbeta1 deficient patient: treatment and outcome.

Patients with mutations in the IFNgamma/IL-12 pathway show an exquisite susceptibility to mycobacterial diseases. An IL-12Rbeta1 deficient patient with impaired intestinal absorption suffered from a 13 year culture-positive Mycobacterium bovis-BCG infection with acquired multidrug resistance. A combined parenteral and enteral anti-mycobacterial treatment, including recombinant IFNgamma, helped to clear his infection.