Antinuclear antibody-associated autoimmune cytopenia in childhood is a risk factor for systemic lupus erythematosus

ABSTRACT

Autoimmune cytopenia (AIC) in children may be associated with positive antinuclear antibodies (ANA) and may progress to systemic lupus erythematosus (SLE). We evaluated the risk of progression to SLE of childhood-onset ANA-associated AIC. In the French national prospective OBS'CEREVANCE cohort, the long-term outcome of children with ANA-associated AIC (ANA titer ≥1/160) and a subgroup of children who developed SLE were described. ANA were positive in 355 of 1803 (20%) children with AIC. With a median follow-up of 5.8 (range, 0.1-29.6) years, 79 of 355 (22%) patients developed SLE at a median age of 14.5 (1.1-21.4) years; 20% of chronic immune thrombocytopenic purpura, 19% of autoimmune hemolytic anemia, and 45% of Evans syndrome. None of the patients with ANA-negative test developed SLE. Severe manifestations of SLE were observed in 21 patients, and 2 patients died. In multivariate analysis including patients with positive ANA within the first 3 months after AIC diagnosis, age >10 years at AIC diagnosis (relative risk [RR], 3.67; 95% confidence interval [CI], 1.18-11.4; P = .024) and ANA titer >1/160 (RR, 5.28; 95% CI, 1.20-23.17; P = .027) were associated with the occurrence of SLE after AIC diagnosis. ANA-associated AIC is a risk factor for progression to SLE, especially in children with an initial ANA titer >1/160 and an age >10 years at AIC diagnosis. ANA screening should be recommended in children with AIC, and patients with ANA should be monitored long-term for SLE, with special attention to the transition period. This trial was registered at www.ClinicalTrials.gov as #NCT05937828.

Pathogenicity of Proteinase 3-Anti-Neutrophil Cytoplasmic Antibody in Granulomatosis With Polyangiitis: Implications as Biomarker and Future Therapies

Granulomatosis with polyangiitis (GPA) is a rare but serious necrotizing auto-immune vasculitis. GPA is mostly associated with the presence of Anti-Neutrophil Cytoplasmic Antibody (ANCA) targeting proteinase 3 (PR3-ANCA), a serine protease contained in neutrophil granules but also exposed at the membrane. PR3-ANCAs have a proven fundamental role in GPA: they bind neutrophils allowing their auto-immune activation responsible for vasculitis lesions. PR3-ANCAs bind neutrophil surface on the one hand by their Fab binding PR3 and on the other by their Fc binding Fc gamma receptors. Despite current therapies, GPA is still a serious disease with an important mortality and a high risk of relapse. Furthermore, although PR3-ANCAs are a consistent biomarker for GPA diagnosis, relapse management currently based on their level is inconsistent. Indeed, PR3-ANCA level is not correlated with disease activity in 25% of patients suggesting that not all PR3-ANCAs are pathogenic. Therefore, the development of new biomarkers to evaluate disease activity and predict relapse and new therapies is necessary. Understanding factors influencing PR3-ANCA pathogenicity, i.e. their potential to induce auto-immune activation of neutrophils, offers interesting perspectives in order to improve GPA management. Most relevant factors influencing PR3-ANCA pathogenicity are involved in their interaction with neutrophils: level of PR3 autoantigen at neutrophil surface, epitope of PR3 recognized by PR3-ANCA, isotype and glycosylation of PR3-ANCA. We detailed in this review the advances in understanding these factors influencing PR3-ANCA pathogenicity in order to use them as biomarkers and develop new therapies in GPA as part of a personalized approach.

4C3 Human Monoclonal Antibody: A Proof of Concept for Non-pathogenic Proteinase 3 Anti-neutrophil Cytoplasmic Antibodies in Granulomatosis With Polyangiitis

Granulomatosis with polyangiitis (GPA) is a severe autoimmune vasculitis associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA) mainly targeting proteinase 3 (PR3), a neutrophilic serine proteinase. PR3-ANCA binding to membrane-bound PR3 on neutrophils induce their auto-immune activation responsible for vascular lesions. However, the correlation between PR3-ANCA level and disease activity remains inconsistent, suggesting the existence of non-pathogenic PR3-ANCA. In order to prove their existence, we immortalized B lymphocytes from blood samples of GPA patients in remission having persistent PR3-ANCA to isolate non-activating PR3-ANCA. We obtained for the first time a non-activating human IgG1κ anti-PR3 monoclonal antibody (mAb) named 4C3. This new mAb binds soluble PR3 with a high affinity and membrane-bound PR3 on an epitope close to the PR3 hydrophobic patch and in the vicinity of the active site. 4C3 is able to bind FcγRIIA and FcγRIIIB and has a G2F glycosylation profile on asparagine 297. 4C3 did not induce activation of neutrophils and could inhibit human polyclonal PR3-ANCA-induced activation suggesting that 4C3 is non-pathogenic. This characteristic relies on the recognized epitope on PR3 rather than to the Fc portion properties. The existence of non-pathogenic PR3-ANCA, which do not activate neutrophils, could explain the persistence of high PR3-ANCA levels in some GPA patients in remission and why PR3-ANCA would not predict relapse. Finally, these results offer promising perspectives particularly regarding the understanding of PR3-ANCA pathogenicity and the development of new diagnostic and therapeutic strategies in GPA.

Prospective study of anterior chest wall involvement in ankylosing spondylitis and psoriatic arthritis

A prospective study of anterior chest wall involvement was conducted in 50 ankylosing spondylitis patients and 50 psoriatic arthritis patients in the absence of palmoplantar pustulosis. All patients underwent a physical examination, tomograms, and a radionuclide bone scan. Magnetic resonance imaging with gadolinium was done in some cases. Half the patients in both groups had anterior chest wall involvement. Enthesitis was the mechanism of the lesions. The manubriosternal symphysis and sternocostoclavicular joints were the most common sites of involvement, although other entheses in the region were affected in some patients.

[Incidence of signs indicating psoriatic rheumatism in radiological involvement of fingers and toes. Apropos of 193 cases of psoriatic arthropathy]

On the basis of 193 cases of psoriatic arthropathy, the authors sought the incidence and rapidity of onset of signs suggestive of this type of rheumatic disorder when there are radiological lesions of the fingers and toes. They conclude that when such radiological lesions exist, signs suggestive of psoriatic arthropathy are frequent (90%), early (85% of cases of psoriatic arthropathy present for less than 5 years) and predominantly involve the distal parts of the fingers and toes (85.5%). The authors consider that the signs which distinguish psoriatic arthropathy from rheumatoid arthritis are due to an extrasynovial process of enthesopathic origin.

[HLA-B and psoriatic rheumatism. Study of 193 cases]

Study of the HLA-B grouping of 193 patients with psoriatic arthropathy (PA), compared with that of a control series consisting of 2,706 healthy subjects representative of the French population, revealed a statistically significant link between PA and antigens B27, B17 and B16. In contrast to reported findings of earlier studies, the authors found no link between an HLA-B antigen and any particular topographical or anatomical form of PA. Antigen B27 was not statistically significantly linked with axial forms of PA nor did it protect against peripheral forms. There were neither more cases of peripheral involvement nor less of axial involvement among non-B27 PA patients. The only statistically significant link which could be shown was that between antigen B27 and sacroiliac involvement in recent PA, present for less than 10 years. The authors conclude that in 60 per cent of cases, PA is associated with a particular antigen: B16, B17 or B27. Involvement of the sacroiliac joints is more common in cases of B27 PA and above all occurs earlier than in others. Regardless of its HLA group, PA as it progresses shows an increasingly clear mixture of spinal, peripheral and sacroiliac lesions, which forms the basis of the originality of this condition.