Objective. We investigated the efficacy and safety of pandemic H1N1 vaccine in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients, and evaluated its correlation with serum cytokine level.
Methods. A total of 43 RA patients and 31 SLE patients were enrolled in the study and were compared with age, sex-matched 40 healthy controls (HC). The blood samples drawn from selected patients before vaccination and in post-vaccination at week 4 were assayed in one session to measure the titers of antibodies against haemagglutinin specific for influenza virus strains: A/California/7/2009 NYMC X-179A (H1N1). Serum IL17 and CXCL13 levels were measured in the same session by enzyme-linked immunosorbent assay. The association of serum cytokine level with anti-influenza antibody titer and mean fold increase (MFI) was investigated. Each specific side effect after vaccination was monitored in both the patients and control groups.
Results. The geometric mean antibody titer (GMT) for pre- and post-vaccination at week 4 was not significantly different between RA and HC, SLE and HC. The seroconversion rate in HC and RA was not significantly different, whereas the seroprotection rate is significantly higher in HC (82.5%) than RA (55.8%) (p＜0.05). MFI in HC, RA, SLE were 19.65, 6.00 and 6.06, which were significantly higher in HC. Serum IL17 level was 6.28±2.89 pg/mL and 7.56±3.34 pg/mL in pre-, post-vaccination SLE patients, 33.85±15.62 pg/mL and 38.04±18.60 pg/mL in RA patients and was significantly lower in SLE patients. Serum CXCL13 level was 518.73± 720.29 pg/mL and 431.53±601.23 pg/mL in pre-, post-vaccination SLE patients, which was significantly higher than HC (149.64±248.81 pg/mL and 147.36±213.92 pg/mL in each pre-, post-vaccination) and was not significantly different with the level of RA patients. In SLE patients, significant correlations were detected between cytokine level and post-vaccination antibody titer (r=0.22 p=0.026 between IL 17 and GMT; r=0.44, p<0.05 between CXCL13 and GMT).
Conclusion. The increase in post-vaccination antibody titer is weaker in both RA and SLE patients group than the HC group. Post-vaccination antibody titer was positively correlated with B lymphocyte chemoattractant and CXCL13 in SLE patients, but not in RA patients.

Keywords: H1N1, IL-17, CXCL 13, Rheumatoid arthritis, Lupus erythematosus