Detection of anti-IFI16 antibodies by ELISA: clinical and serological associations in systemic sclerosis.
OBJECTIVE
To validate the clinical significance of anti-IFI16 autoantibodies in SSc and assess their associations with serological markers of SSc.


METHODS
A semi-quantitative ELISA was used to detect anti-IFI16 autoantibodies in the sera of 344 SSc patients from seven Italian hospitals and 144 healthy controls. SSc-associated autoantibodies [anti-RNA polymerase III (anti-RNAP III) antibodies, anti-centromere, anti-topo I] and IF patterns were evaluated using commercial assays. Statistical analyses were performed to test clinical and serological associations.


RESULTS
The results of this study confirm a significant prevalence (29%) of anti-IFI16 antibodies in the SSc population (n = 344). Anti-IFI16 antibodies were also detected in 30% of the SSc patients who tested negative for both ACAs and anti-topo I (anti-Scl70) antibodies. In this subgroup of patients, anti-IFI16 antibodies were significantly associated with the limited cutaneous form of SSc with a sensitivity of 40% and a specificity of 81%. Moreover, analysis of the distribution of anti-RNAP III antibodies vs anti-IFI16 in the same SSc population showed that they were mutually exclusive. IIF revealed no association between anti-IFI16 and fluoroscopic patterns, due to a lack of IFI16 autoantigen in HEp-2 cells. Anti-IFI16 antibody levels were also significantly associated with heart involvement.


CONCLUSIONS
Anti-IFI16 autoantibodies are frequently detected in SSc, displaying clinical and laboratory associations, and being particularly useful for diagnosis and disease classification in patients who are negative for other SSc serological markers.
Department of Public Health and Microbiology, University of Turin,Turin, Italy.
Silvia
S
Costa
Michele
M
Mondini
Valeria
V
Caneparo
Antonella
A
Afeltra
Paolo
P
Airò
Francesca
F
Bellisai
Paola
P
Faggioli
Roberto
R
Gerli
Milvia
M
Lotzniker
Pier L
PL
Meroni
Gabriella
G
Morozzi
Antonella
A
Radice
Valeria
V
Riccieri
Mirko
M
Scarsi
Gian D
GD
Sebastiani
Renato A
RA
Sinico
Angela
A
Tincani
Marisa
M
Gariglio
Santo
S
Landolfo
D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D000974:Antibodies, Antinuclear / Q000097:blood; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D004264:DNA Topoisomerases, Type I / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000097:blood / Q000276:immunology*; D010750:Phosphoproteins / Q000097:blood / Q000276:immunology*; D012329:RNA, Bacterial / Q000276:immunology; D012595:Scleroderma, Systemic / Q000097:blood* / Q000175:diagnosis / Q000276:immunology*
D000888:Antibodies, Anti-Idiotypic; D000974:Antibodies, Antinuclear; D015415:Biomarkers; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012329:RNA, Bacterial; C096035:RNAIII, Staphylococcus aureus; C538950:anticentromere antibody; C076700:IFI16 protein, human; D004264:DNA Topoisomerases, Type I