Clinical phenotypes and prognosis of cytomegalovirus infection in the pediatric systemic lupus erythematosus: a longitudinal analysis

This retrospective study was conducted in 146 pSLE patients who were seen and followed up at Peking Union Medical College Hospital (PUMCH) between January 2012 and December 2021. The inclusion criteria were as follows: 1) SLE was diagnosed before the age of 18 and was followed up at PUMCH; 2) patients met the SLE classification criteria of the 1997 American Academy of Rheumatology (ACR) or 2019 European League Against Rheumatism (EULAR)/ACR [6, 7]; 3) Patients completed all three CMV screening tests, including CMV-DNA, CMV- phosphoprotein 65 (pp65), and CMV-IgM. The exclusion criteria were as follows: 1) Evidence of other active infections, such as Epstein-Barr virus, parvovirus B19, bacteria, parasites, chlamydia, mycoplasma, fungi, etc.; 2) Overlap syndrome (overlap between pSLE and other rheumatic diseases); 3) Presence of other diseases such as malignancy and severe malnutrition. We manually set a timeframe of 4 weeks to ensure the consistency of timings between SLE clinical data and CMV infections. Clinical data collected within 4 weeks prior to CMV screening included demographic information, clinical presentation, physical examination, laboratory data, and treatment information. The data of the CMV positive group and the negative group were reviewed and compared. Disease activity was evaluated by the SLE Disease Activity Index-2000 (SLEDAI-2K) [8]. CMV-positive pSLE were divided into treatment and non-treatment groups for comparison and analysis.

Many patients were diagnosed and treated in local hospitals, and then transferred to our hospital due to the poor treatment effect or recurrence, so the CMV testing was performed at any time in the SLE process. As long as one or more of the CMV-IgM, CMV-DNA and pp65 antigens in the peripheral blood of pSLE patients are positive, they are considered to be complicated with CMV infection. For pSLE patients who received anti-CMV therapy, the total course of treatment was 3 months, of which the first month received daily intravenous ganciclovir (5 mg/kg, every 12 hours), and the treatment was discontinued after 3 consecutive weeks. Oral ganciclovir (30-50 mg/kg/d) was administered in the first week of the second and third months, respectively.

As shown in Additional file 1, among the 427 patients with pSLE, 129 were excluded because they did not perform all three CMV tests, and some of them completed one or two tests, of which 83 (64.5%) were CMV positive. Of the remaining children, 20 cases were excluded because of overlap syndrome, 132 cases were excluded because of other active infections, and among them, 116 (87.9%) were CMV positive. Finally, 146 eligible SLE were included, of which 109 (74.7%) were complicated with CMV infection (Additional file 2). Among patients with CMV infection, 54 (49.5%) were positive for CMV IgM antibody, 95 (87.2%) for CMV pp65 antigen, and 11 (10.1%) for CMV-DNA. The average age of pSLE patients was 12.01 ± 2.21 years, and the male to female ratio was 1:3.7. The demographics and clinical presentation of the CMV-positive and negative groups were shown in Table 1. The incidence of fever and musculoskeletal involvement in the positive group was significantly higher than that in the negative group (P=0.008). There were no significant differences in age, gender and other clinical manifestations between the two groups. The SLEDAI-2K in the CMV positive group was significantly higher than that in the negative group.

As shown in Table 2, CMV-infected pSLE patients were more prone to hemolytic anemia, elevated liver enzymes, hypoalbuminemia, hypocomplementemia, and multiple autoantibodies including anti-dsDNA antibody, anti-nucleosome antibody, and anti-histone antibody. We observed no significant associations were observed between CMV infection and lymphocyte subsets (Additional file 3).

Because immunosuppressive therapy may reduce immune defense in pSLE patients, we collected all patients' medication within 4 weeks before CMV screening and analyzed the effect of medication on CMV infection. 88 patients (60.3%) received prednisone or immunosuppressive therapy, of which hydroxychloroquine was the most commonly used (N=56, 38.4%), followed by mycophenolate mofetil (MMF) (N= 27, 18.5%) and cyclophosphamide (CTX) (N=16, 11%). Only a few patients received cyclosporine (N=2), tacrolimus (N=2), leflunomide (N=5), belimumab (N=3), sirolimus (N=2) and azathioprine (N=1). There was no statistical difference between the CMV-positive group and the CMV-negative group in the dose of prednisone, the percentage of CTX use, or the percentage of glucocorticoid combined with two or more immunosuppressive agents (Additional file 4).

The stepwise logistic multiple regression analysis was then used to further explore the clinical manifestations for CMV infection in pSLE, based on the univariate analysis results. It showed that anti-dsDNA antibody (P=0.018, OR 3.36, 95% CI 1.22-9.22), hypocomplementemia (P<0.001, OR 5.76, 95% CI 1.06-16.36), SLEDAI-2K score (P=0.031, OR 1.03, 95% CI 1.01-1.18), and musculoskeletal involvement (P=0.039, OR 3.18, 95% CI 1.12-10.24) were all positively associated with CMV infection in pSLE (Fig. 1).

The average SLEDAI-2K was higher in the CMV positive group than that of the CMV negative group [(15.18±7.28) vs (10.22±5.55)] (P<0.001). In our longer follow-up study (up to 10 years), 135 patients were followed up consistently. There has been 49 (36.3%) subsequent flare of SLE in the cohort with an average follow-up of 4.32±3.47 years and the CMV-positive group had more cases of subsequent flare (P=0.001) (Fig. 2A).

Of the 109 SLE patients with CMV infection, 45 (44.6%) relapsed within a median follow-up period of 47±9 months. Kaplan-Meier analysis showed that SLE patients with CMV infection had a significantly higher risk of progression to flare (P = 0.021) (Fig. 2B).

Generalized estimating equations were used to evaluate the changes in disease activity over time in the CMV positive and CMV negative groups (Fig. 3A, Table 3), and the results showed that SLEDAI-2K decreased significantly over time in both groups (P<0.001). There were significant differences in SLEDAI-2K between the two groups at each follow-up time point (P=0.003). The trend of SLEDAI-2K in the two groups over time was similar (P=0.817).

The infection group was further divided into the treatment group and the non-treatment group. The generalized estimating equation was used to evaluate the changes in disease activity in the two groups over time (Fig. 3B, Table 3). The results showed that SLEDAI-2K decreased significantly in both groups over time (P<0.001). There were significant differences in SLEDAI-2K between the two groups at each follow-up time point (P=0.046). There was a significant difference in the trend of SLEDAI-2K between the two groups over time (P=0.001).

Generalized estimating equations were used to evaluate the relationship between pp65 titer and SLEDAI, and the results showed a positive correlation (P <0.001) (Fig. 3C, Table 3).