Background/Purpose: Previous works assessing antibody response to pneumococcal polysaccharide vaccine (PPV) in systemic lupus erythematosus (SLE) relied exclusively on the quantitative increase in antibody titers to Streptococcus pneumoniae serotypes irrespective of baseline levels. Few patients were taking immunosuppressive (IM) drugs, none with mycophenolate mofetil (MMF). Our study aims to investigate the effect on PPV immunogenicity of conventional IM drugs for SLE management by means of current evidence-based recommendations from the American Academy of Allergy, Asthma and Immunology.

Methods: We performed a prospective study in which 54 consecutive SLE patients from our cohort were immunized with 23-valent PPV (PPV23) between February 2013 and April 2014. Twenty-eight subjects had been taking IM drugs for ≥ 6 months prior to vaccination and 26 other received no IM medication and prednisone (PDN) ≤ 5 mg/day for the same period before immunization. ELISA was used to assess serum IgG antibody titers specific for 7 pneumococcal serotypes from samples collected immediately before PPV23 injection and also 4-6 weeks thereafter. The primary immunogenicity endpoints were the seroconversion rates (prevaccine titer < 1.3 µg/mL antibody and postvaccine titer ≥ 1.3 µg/mL) and seroconversion rates with a ≥ 2-fold increase in antibody titers. To fulfill the later outcome there should be a response to ≥ 70% of the serotypes tested.

Results: Both groups were similar regarding the mean disease duration (9.1 vs 12.1 years, p= 0.11) and female predominance (92.8% vs 88.4%, p=0.57). However, the patients on IM therapy had higher median SLEDAI-2K score (4 vs 0, p=0.02), were younger (mean age 35.5 vs 43.3 years, p=0.008) and more often used PDN (100% vs76.9%, p=0.02) as well as higher median dose (5 mg/day vs 4.5 mg/day, p=0.01) compared to those off IM therapy. IM treatment comprised optimal doses of MMF in 12 patients, azathioprine (AZA) in 6, intravenous (IV) cyclophosphamide (CYC) in 6, IV CYC switching to MMF or vice versa in 3, and IV CYC switching to AZA in 1. There were no differences between the groups treated or not with IM drugs concerning the overall (53.1% vs 60.3%, respectively; p=0.29) and type-specific seroconversion rates (range 43.7%-77.7% vs 52.4%-90%, respectively; p>0.05 for each serotype) as well as for overall (49.6% vs 58.6%, respectively; p=0.15) and serotype-specific seroconversion rates combined with a ≥ 2-fold increase in antibody titers (range 37.5%-72.2% vs 52.4%-80%, respectively; p>0.05 for each serotype). Both groups did not show significant worsening in mean levels of C3 and C4 complement, percentage of antibodies to dsDNA, and median SLEDAI-2K score.

Conclusion: This is the first study in SLE to evaluate seroconversion rates following PPV and the largest in number of vaccinated patients on IM therapy. Our results suggest an inadequate immunogenicity compared to the general population and no further impairment in response rates by these IM drugs. A large proportion of pneumococcal serotypes remained unprotected in both treatment groups despite vaccination, thus urging immunogenicity studies in SLE patients with the new 13-valent pneumococcal conjugate vaccine.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/humoral-immune-response-to-pneumococcal-polysaccharide-vaccine-in-sle-patients-on-immunosuppressive-therapy-assessment-of-serotypes-without-protective-antibody-levels/