Pediatric Pulrnonology 22:96-100 (1996)

Consequences of Hypogammaglobulinemia and Steroid Therapy in Severe Bronchopulmonary Dysplasia

William Wheeler, MD, Stephen Kurachek, MD, John McNamara, MD, John Fugate, MD, and Nancy Hoogenhous, BSN, MPH

Summary. We retrospectively studied the relation between corticosteroid therapy, hypogam- maglobulinemia (HG), and recurrent infections in 37 infants with moderate to severe bronchopul- monary dysplasia (BPD). Ninteen of the 37 patients had tracheostomies because of chronic respiratory failure. We hypothesized that recurrent infections were most prevalent in infants whose IgG levels remained low at one year of age (persistent HG) and in infants receiving high doses of corticosteroids during the first year of life. We further hypothesized that the duration of HG was strongly correlated with the cumulative first year steroid dose. We also studied the response to intravenous gammaglobulin (IVIG) replacement therapy in this population of BPD infants. Our results showed an association between first year corticosteroid dose, duration of HG (r = 0.49, p < 0.003), and frequency of infections (r = 0.51, p < 0.001). We noted a relatively strong correlation between frequency of infections and duration of HG (r = 0.84, p < 0.0001). Twenty-four of 37 (65%) infants showed persistent HG and 49% had evidence of abnormal specific antibody production. Sixty-four percent of infants studied had reduced lymphocyte responsiveness to mitogen stimulation. Nineteen of 37 (51 Yo) infants required IVlG for an average duration of 17.9 months due to recurrent infections. The average number of infections per year decreased from 10.6 to 2.8 (t = 12.32, p < 0.0001). There were no complications associated with IVlG therapy, but one infant died of bronchiolitis obliterans following heart-lung transplanta- tion. Eight of 37 (22%) infants have persistent immunologic dysfunction requiring ongoing WIG at four years or more of follow-up. We conclude that a substantial number of ill infants with BPD will have immune dysfunction characterized by persistently low IgG levels and reduced specific antibody responsiveness to protein antigens. We speculate that these findings are related to the cumulative dose of corticosteroids received in the first year of life and to the severity of underlying disease. Pediatr Pulmonol. 1996; 22:96-100. o 1996 Wiley-Liss, Inc.

Key words: Hypogammaglobulinemia, bronchopulmonary dysplasia, chronic respira- tory failure of infancy, corticosteroid therapy, intravenous gammaglobulin (IVIG), recurrent infections.

INTRODUCTION

Antibody deficiency and frequent infections have been observed in patients with BPD.'<* We previously described HG in a majority of ventilator-dependent infants with BPD.' Some infants showed persistently low IgG levels past the first year of life. We observed that many of these infants had received large doses of corticosteroids during their first year because of salutary pulmonary effects. This study is an extension of our previous observations. We describe the clinical course and immunologic function of young patients with severe oxygen or ventilator-depen- dent BPD and HG. We hypothesized that the severity and duration of HG were correlated with the dose of corticosteroids received in the first year of life. We further hypothesized that the duration of HG and humoral im- mune dysfunction were associated strongly with clinical infections in this population. Lastly, we explored the pos- sibility that intravenous immunoglobulin replacement therapy might reduce the frequency of infections in these patients. 0 1996 Wiley-Liss, Inc.

METHODS

We retrospectively reviewed the clinical course of 190 infants with BPD followed in our pediatric pulmonology clinic between January 1988 and January 1994. Of these 190 patients, 37 had serial levels of IgG measured and

From the Division of Pulmonary and Critical Care Medicine, Minneap- olis Children's Medical Center, Minneapolis, Minnesota.

Received December 23, 1994; (revision) accepted for publication April 24. 1996.

This study was partially funded through the Pulmonary Research Foun- dation at Minneapolis Children's Medical Center, Minneapolis, Min- nesota.

This work was presented at the International Conference of the Ameri- can Thoracic Society, Boston, Massachusetts, May 21-25, 1994.

Address correspondence and reprint requests to Dr. William B. Wheeler, 2545 Chicago Avenue South, Suite 617, Minneapolis, MN 55404.

WIG and Steroid Therapy in BPD 97

for IVIG therapy. Duration of therapy was determined by a period free of serious infections for 3 to 6 months, and evidence of specific antibody formation (HIB antibody following immunization, isohemagglutinin antibody pro- duction, diphtheria, and/or tetanus antibody production).

Specific antibody function testing was performed in 24 of the 37 infants and included antitetanus and antidiph- theria antibody titers by passive hemagglutination (Uni- versity of Minnesota Protein Laboratory) 6 weeks follow- ing immunization with DPT vaccine (Connought, Swiftwater, PA), as well as isohemagglutinin levels. A normal response was a titer 2 1 :SO or a threefold rise in titer from preimmunization levels. Occasionally, other antigens were administered to poorly responsive infants in an effort to assess specific antibody responsiveness (i.e., HIB, MMR, Pneumovax 23, Merck & Co., Inc.). Thirteen of 37 patients had lymphocyte stimulation stud- ies and were assessed for mitogen responsiveness to ConA, pokeweed mitogen, and tetanus antigen using stan- dard techniques.’ Ten of 37 patients had T and B cell function studies using standardized techniques.*

Statistical analysis of continuous group data was per- formed by the two-tailed Bonferroni corrected indepen- dent t test. Comparisons of discrete group data were ana- lyzed using a x2 analysis with Fisher’s Exact Test when applicable. Correlations between variables were assessed by the Pearson Product Moment Test. P values < 0.05 were considered significant.

had adequate clinical data for analysis. All 37 infants required either chronic oxygen or ventilatory support due to their chronic lung disease, and 19 of the 37 required a tracheostomy for chronic ventilatory support. This group of infants represents the severe end of the clinical spectrum of BPD. The patients were followed with serial clinical and radiographic scoring4 and serum immuno- globulin levels (Roche Fara-Incstar, Stillwater, MN). The first clinical scores and IgG levels were obtained between 3 and 6 months of age. Persistent HG was defined as an IgG level <250 mg/dl at 1 year of age.5,6 Each patient was evaluated by thorough hospital and clinic chart review for duration of mechanical ventilation, duration of oxygen therapy, number of infections per year, and cumulative steroid dose received in the first year (mg).

Infection was defined as an acute deterioration in respi- ratory and overall clinical stability secondary to an obvi- ous infectious agent. This was diagnosed by an attending pulmonologist rounding on the infant using the following criteria: Tracheobronchitis was diagnosed when the infant exhibited purulent tracheal secretions, fever, increased respiratory distress, and a pathogenic organism on culture. Pneumonia was diagnosed by the above features plus a new infiltrate on the chest radiograph. Otitis media was diagnosed by otoscopy showing an erythematous or puru- lent tympanic membrane with altered mobility and fever. Abnormal sinus films were necessary for diagnosis of sinusitis. Urinary tract infections, bacteremiahepsis, and enterocolitis were diagnosed by positive body fluid cul- tures for pathogenic viruses or bacteria. These infections adversely affected the patient resulting in increased work of breathing, increased ventilator or oxygen settings, and occasionally admission to the pediatric intensive care unit. Some infections were considered life-threatening. No in- fection was considered trivial in terms of its effect on the infant’s overall status.

Corticosteroid dosing with different steroid prepara- tions was controlled for by converting the corticosteroid dosage to a prednisolone equivalent (in mg).’ Each patient was assessed for the need for gammaglobulin replacement therapy (IVIG) by his attending pulmonologist. Criteria for initiating IVIG included persistently low IgG levels or borderline low IgG levels with absent specific antibody function and evidence of repeated, serious infections. When an infant exhibited recurrent serious infections that impaired weaning of oxygen or ventilation, despite being treated with prophylactic antibiotics, he was considered

I Abbreviations I BPD Bronchopulmonary dysplasia HG Hypogammaglobulinemia IgG Immunoglobulin G IVIG Intravenous gammaglobulin TM Tracheomalacia

RESULTS

The frequency of low IgG (<250 mg/dl) was 81% in the first 6 months of life (30 of 37); 21 of these 37 infants (57%) had an IgG level <200 mg/dl in the first 6 months of life. Over time there was an increase in total IgG level so that at age 1 year, 13 of the 37 (35%) had normal IgG levels >250 mg/dl. There was a moderate association between the initial IgG level and the total steroid dose in the first year of life ( r = -0.42, P = 0.008) and the initial IgG level and the BPD score (r = -0.43, P = 0.005). BPD population and immune function data are shown in Table 1. Twenty-four of the 37 (65%) pa- tients exhibited persistent HG. Patients with persistent HG had significantly worse BPD and radiographic scores, longer duration of ventilation and oxygen support, and significantly lower initial IgG levels than did those pa- tients with a normalized IgG level at 12 months of age. There was an association between the first year corticoste- roid dose and duration of HG (Fig. 1). Patients with persistent HG frequently had reduced specific antibody function and reduced T cell function compared to the group of BPD with normal IgG levels. No patient with an initial IgG level of 2250 mg/dl at six months of age had abnormal specific antibody production to diphtheria or tetanus antigens. Two of seven patients with persistent HG had reduced B cell numbers, and one patient had a

98 Wheeler et al.

TABLE 1-BPD Population Data (Mean 2 1 SD)

Persistent HG Normalized HG ( 2 1 2 mos) (<12 mos) N = 24 N = 13 P

Birth weight (g) Gestational age (wk) BPD score (0-15) Radiographic score (0-10) Ventilator duration (mos) O2 therapy duration (mos) Initial IgG level (mgldl) IgA level (mg/dl) Low IgG duration (mo) 12 mos steroid dose (mg) Low specific antibody function (%) Low T cell function (%) Infectionslyear Need IgG (%) TM (%)

1164 t 792 28.5 t 4.1 9.0 t 2.5 5.8 t 1.8

17.3 t 14.2 30.2 t 15.9 147 t 78 31 t 26

27.9 t 15.8 796 t 421 17/21 (81%) 7/11 (64%)

11 2 3 71 75

1208 2 418 29.6 2 3.1 5.7 t- 2.6 3.9 2 1.8 5.1 2 8.1

10.3 t 11.9 286 t 156 61 t- 54 4.1 t 3.4 387 t- 285 1/3 (33%) 0/2 (0%)

4 2 2 17 25

0.86 0.42

0.001 0.007 0.01

0.001 0.01 0.05

0.0001 0.005 0.05 0.19

0.0001 0.002 0.004

Duration low lgG (mos.)

8o 1- 60

J ::I I ~

500 1,000 k ” I 0

0

1st Year Steroid Dose (mg.)

Fig. 1. Relationship between the first-year corticosteroid dose and the duration of HG in infants with BPD.

r=.49, p< 003

reduced percentage of T lymphocytes. IgA deficiency was noted in 7 of 37 patients (19%), and these levels normalized over time in all but one patient. A low IgA level was not correlated with frequency of infections or the first-year steroid dose. One of 37 patients died from bronchiolitis obliterans, following heart-lung trans- plantation.

Types of infections in BPD are shown in Table 2. Tracheobronchitis, pneumonia, and otitis media were the most commonly encountered infections. The average number of mucosal or systemic infections per patient per year was 9.7 (range: 3-20). Local pediatrician or family physician records were not reviewed, so this number may actually be hgher than the listed one. There was a strong correlation between the number of infections per year and the first year cumulative steroid dose (Fig. 2). There was also a significant correlation between the duration

TABLE 2-Types of Infections in 37 Patients With BPD

Infection N Percent of total

Purulent tracheobronchitis 114 33 Otitis medidsinusitis’ 92 26 Pneumonia 53 15

Urinary tract infection 21 6

Enterocolitis 16 4.5

Sepsis/bacteremia 38 11

Pyogenic skin infections 16 4.5

‘Only two patients had radiographically documented sinusitis.

1st Year Steroid Dose(mg.) 2,000 I 1,500

1,000

500

0 5 10 15 20 25 0

Number Infections/yr. r = .51 , pc ,001

Fig. 2. Relationship between annual frequency of infections and first year cumulative steroid dose in infants with BPD.

of low IgG levels and the number of infections per year (Fig. 3).

Despite prophylactic antibiotic therapy, 19 of 37 infants were deemed appropriate for IVIG replacement therapy due to recurrent infections. The number of infections in this group significantly decreased with IVIG therapy from

IVlG and Steroid Therapy in BPD 99

humoral or cellular immune response to protein antigens. Most patients studied had normal T and B cell enumera- tion studies. This suggests that the nature of the immuno- logic defect is one of impaired antibody responsiveness, which differentiates the persistent HG group from infants with transient HG of infancy.",l2

Lederman et a1.2 observed prolonged and persistent HG in infants receiving chronic corticosteroid therapy in the first year of life. Our data show a moderate correlation between the dose of steroids given in the first year and multiple variables, including the duration of low IgG levels and the severity of BPD as reflected by the BPD score. Because we did not have a control population of severe BPD who did not receive corticosteroids, it is impossible to separate the true effects of corticosteroid therapy versus severity of BPD on IgG levels. This is a significant flaw in our study and limits a definite conclu- sion to our hypothesis. We speculate, however, that pro- longed and high-dose corticosteroid therapy results in a catabolic effect, reducing the infant's ability to make specific antibodies to protein antigens. The sicker patients are usually the ones in need of antiinflammatory therapy; thus the finding of lower IgG levels in the more severe BPD patients. Adverse effects of corticosteroid therapy in BPD have been reported and include adrenal suppression, hypertension, increased susceptibility to infections, hy- pertrophic cardiomyopathy, and increased catabolism with poor growth ~elocity. '~- '~ Our data suggests that in the moderate to severe BPD patient, prolonged corticoste- roid therapy may be associated with reduced immune functions.

The number of infections per year in the persistent HG group was striking. These infections were primarily of mucosal surfaces involving the upper and lower respira- tory tract, the gastrointestinal tract, and the genitourinary tract and caused significant morbidity for the infants; 11 % of infections were systemic, involving the bloodstream. There was a moderate correlation ( r = .51) between the frequency of infections and the first-year corticosteroid dose. There was an even stronger correlation ( r = 34) between the frequency of infections and the duration of a low IgG level. Eight patients developed 38 systemic infections with bacteremia andlor clinical sepsis. All were patients with gastrostomy, tracheostomy, and on chronic steroid therapy. Systemic fungal disease was not seen, suggesting intact cell-mediated immunity. The most com- monly seen infections were tracheobronchitis or pneumo- nia, and these most often occurred in tracheotomized patients with a disrupted muscosal barrier. Despite the use of prophylactic antibiotics in all infants with persistent HG, 19 of 24 required IVIG replacement therapy for an average of 17.9 months (range: 2-70 months). This ther- apy resulted in a highly significant reduction in mucosal or systemic infections and improved well-being of the patients. Once it was determined that ongoing IVIG ther-

-0 20 40 60 80 Duration of low IgG (rnos)

r= 8 4 , p< 0001

Fig. 3. Relation between duration of low IgG levels and fre- quency of infections in infants with BPD.

10.6 infections per year to 2.8 infections per year ( t = 12.32; P = .OOOl). No patient developed invasive systemic disease after starting IVIG. The presence of TM was correlated with multiple variables, including the first- year steroid dose, the BPD score, and the duration of HG ( P < .01). After 4 years of follow-up, 8 of 37 (22%) patients carry the diagnosis of chronic immune dysfunc- tion, and they still require ongoing IVIG replacement therapy. One patient has agammaglobulinemia. All of these patients exhibit decreased specific antibody re- sponses to tetanus toxoid and diphtheria antigen and suffer from recurrent infections if taken off IVIG.

DISCUSSION

Preterm infants without BPD have a high incidence of transient HG in the first few months of life. These low levels are related to a decreased gestational age, and they usually normalize by 8 to 12 months of age.g IVIG replacement therapy is not necessary in this population of infants. Moderately to severely affected infants with BPD also may show very low IgG levels in the first few months of life as observed by Ledermad and Malik.'O The significance of a low IgG level has been unclear in the minds of many clinicians caring for infants with BPD. Our data show that a persistently low IgG level of <250 mg/dl at 12 months of age is associated with an increased frequency of mucosal or systemic infections and with specific antibody dysfunction. In studying this group of persistently HG infants, we have confirmed the findings of Lederman2 that specific antibody responsiveness is diminished. Postimmunization responses to tetanus tox- oid or diphtheria antigen were decreased in 81% of pa- tients studied. Reduced isohemagglutinin levels were ob- served in these patients as well. In 11 patients T cell mitogen responsiveness was assessed and found to be decreased in 7 infants (64%). These findings suggest a decreased ability to process antigen and mount a normal

100 Wheeler et al.

apy was necessary, an indwelling central venous line was secured for ongoing replacement therapy. These data confirm the findings of Malik and coworkers’0 that IVIG is helpful in reducing infections in BPD. Treatment with IVIG was discontinued when the patient showed signs of specific antibody production (i.e., normal isohemag- glutinin levels) and remained infection-free for 3 months or longer during a trial off IVIG. In no case were compli- cations of IVIG infusions seen such as hypotension, ana- phylaxis, or hepatitis A, B, or C.

Limitations of our study are significant because these data were retrospectively collected in an unblinded fash- ion. In addition, the lack of a severe BPD control group who did not receive large doses of corticosteroids makes definitive conclusions regarding the effects of steroid dos- ing impossible. We must consider these results as prelimi- nary, given the methodological flaws present. However, despite these limitations, the clinical observations about infections and immunity in this select group of severe BPD infants appear valid.

We conclude that there is a high incidence of hypogam- maglobulinemia in infants with moderate to severe BPD. A majority of patients will remain persistently HG at 1 year of age, and this is related to the severity of BPD and the cumulative corticosteroid dose given in the first year of life. The immune dysfunction is characterized by a reduction in specific antibody production to protein antigens and manifests itself as recurrent mucosal and systemic infections. Treatment with IVIG appears effec- tive in reducing the frequency of infections. Further work should be done in this population to assess the specific effects of corticosteroid therapy on immunomodulation and the development of humoral immunity. Future clinical studies should be prospectively designed in a blinded fashion to assess therapeutic interventions such as IVIG.

ACKNOWLEDGMENTS

We thank Ms. Deb Gerrety for her excellent help in manuscript preparation, Stephanie Bisson, R.N. and Su- zanne Sanders for data acquisition, and Linda Johnson, Ph.D. for assistance with statistical analysis of the data.

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