Serum cathelicidin level is associated with viral etiology and severity of bronchiolitis
2012; Elsevier BV; Volume: 130; Issue: 4 Linguagem: Inglês
10.1016/j.jaci.2012.07.044
ISSN1097-6825
AutoresJonathan M. Mansbach, Pedro A. Piedra, Niels Borregaard, Adrian R. Martineau, Mark I. Neuman, Janice A. Espinola, Carlos A. Camargo,
Tópico(s)Cystic Fibrosis Research Advances
ResumoBronchiolitis is a common childhood acute respiratory infection (ARI) and the leading cause of hospitalization for US infants.1Subcommittee on Diagnosis and Management of BronchiolitisDiagnosis and management of bronchiolitis.Pediatrics. 2006; 118: 1774-1793Crossref PubMed Scopus (852) Google Scholar The 2 most common viral etiologies of severe bronchiolitis (ie, bronchiolitis requiring hospitalization) are respiratory syncytial virus (RSV) and human rhinovirus (HRV).2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google ScholarAlthough low serum 25-hydroxyvitamin D (25[OH]D) levels have been associated with the increased incidence and severity of ARI, randomized controlled trials of vitamin D supplementation have demonstrated mixed results for the prevention of ARIs.3Bartley J. Vitamin D, innate immunity and upper respiratory tract infection.J Laryngol Otol. 2010; 124: 465-469Crossref PubMed Scopus (62) Google Scholar Nonetheless, vitamin D status continues to garner attention as a modifiable risk factor for infectious diseases because it plays a central role in the innate immune system. Hydroxylation of 25(OH)D creates 1,25-dihydroxyvitamin D, which in vitro increases the transcription of the innate immune protein, human cathelicidin antimicrobial peptide 18 (hCAP-18).4Liu P.T. Stenger S. Li H. Wenzel L. Tan B.H. Krutzik S.R. et al.Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response.Science. 2006; 311: 1770-1773Crossref PubMed Scopus (2947) Google Scholar Bronchial epithelial cells and circulating white blood cells produce hCAP-18,5Adams J.S. Hewison M. Unexpected actions of vitamin D: new perspectives on the regulation of innate and adaptive immunity.Nat Clin Pract Endocrinol Metab. 2008; 4: 80-90Crossref PubMed Scopus (608) Google Scholar which is capable of killing a wide variety of viral and bacterial pathogens.3Bartley J. Vitamin D, innate immunity and upper respiratory tract infection.J Laryngol Otol. 2010; 124: 465-469Crossref PubMed Scopus (62) Google Scholar Although 25(OH)D levels are the best measure of overall vitamin D status, it is 1,25-dihydroxyvitamin D that drives the production of hCAP-18. Therefore, when examining the association between vitamin D and infectious disease outcomes, hCAP-18 may provide additional data.As part of a prospective, multicenter study enrolling children younger than 2 years hospitalized with bronchiolitis November through March,2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google Scholar study investigators at 1 Boston site also enrolled children with bronchiolitis discharged home from the emergency department (ED). For all participants at this site, investigators collected clinical data, blood samples, and nasopharyngeal aspirates. Serum 25(OH)D concentration was measured by liquid chromatography-tandem mass spectrometry. ELISA was used to measure serum levels of hCAP-18 (see this article's Online Repository at www.jacionline.org). The nasopharyngeal aspirates were tested for 15 viruses by using real-time PCR.2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google Scholar We hypothesized that hCAP-18 levels would not be associated with the viral etiology of bronchiolitis but that children with low hCAP-18 levels would more likely be hospitalized for 24 or more hours. For the latter hypothesis, we divided the children into 2 groups: 1) discharged home from the ED or hospitalized for less than 24 hours and 2) hospitalized for 24 hours or more. Analysis used descriptive statistics and multivariable logistic regression. This study was approved by the Boston Children's Hospital institutional review board.Of 82 enrolled children, 33 (40%) were discharged home from the ED or hospitalized for less than 24 hours and 49 (60%) were hospitalized for 24 hours or more. Overall, the median age was 5 months (interquartile range, 2-10); 46 (56%) were boys; 39 (47%) were white, 21 (26%) were black, and 22 (27%) were of other or unknown races; 35 (43%) had Hispanic ethnicity. Furthermore, median (interquartile range) levels of key serum tests were as follows: 25(OH)D 34 ng/mL (28-40) and hCAP-18 218 ng/mL (130-382). The 2 most commonly identified viruses were RSV (76%) and HRV (18%). Both RSV and HRV were identified in 6% of the children, and no virus was identified in 5% of the children. There was neither a significant correlation between 25(OH)D and hCAP-18 levels (ρ = −0.12; P = .26) nor a significant association between 25(OH)D and hospitalization for 24 hours or more (P = .50).Median hCAP-18 levels were lower among children with RSV only or RSV in combination with non-HRV viruses than among children with HRV only or HRV in combination with non-RSV viruses (median [interquartile range], 159 ng/mL [118-243] vs 497 ng/mL [401-577]; P < .001). Interestingly, the median hCAP-18 level for the 5 children in whom both RSV and HRV were identified was between these 2 values (382 ng/mL [296-406]). There was no association between 25(OH)D levels and viral etiology.As shown in Table I, children with hCAP-18 levels less than the median (<218 ng/mL) were significantly more likely to be hospitalized for 24 hours or more than were children with hCAP-18 levels above the median (78% vs 41%; P = .001). In multivariable analysis (Table II) adjusting for age, sex, and race, children with serum hCAP-18 levels of less than 218 ng/mL were more likely to be hospitalized for 24 hours or more (adjusted odds ratio, 5.7; 95% CI, 2.0-16.2; P = .001). Premature birth was excluded from the final multivariable model because it was not significantly associated with hCAP-18 values (Table I) and did not materially change the results of other model factors. We did not collect information about prior ARIs.Table ICharacteristics of children presenting to the ED with bronchiolitis by serum hCAP-18 levelshCAP-18 < 218 ng/mL (n = 41)hCAP-18 ≥ 218 ng/mL (n = 41)P valuen%n%Age (mo).39 0-1.9922615 2-5.917411434 6-2415372151Sex1.00 Male23562356 Female18441844Race.04 White15372459 Black10241127 Other or missing1639615 Hispanic18441741.82Insurance.10 Private22542050 Public17411230 None or unknown25820Premature birth.12 ≤37 wk1332717 >37 wk28683483Admission status <24 h or ED-only9222459.001 ≥24 h32781741 Open table in a new tab Table IIMultivariable predictors of hospitalization for 24 hours or more among children presenting to the ED with bronchiolitisCharacteristicOdds ratio95% CIP valueAge (mo) 0-1.91.80.4-7.6.43 2-5.91.00.4-3.1.93 6-241.0(reference)Sex Male1.0(reference) Female1.00.4-2.5.92Race White1.0(reference) Non-white0.60.2-1.7.32hCAP-18 (serum) (ng/mL) <2185.72.0-16.2.001 ≥2181.0(reference) Open table in a new tab One possible reason that we found no relationship between the 25(OH)D and hCAP-18 levels is that the majority of children had 25(OH)D levels of more than 30 ng/mL.6Bhan I. Camargo Jr., C.A. Wenger J. Ricciardi C. Ye J. Borregaard N. et al.Circulating levels of 25-hydroxyvitamin D and human cathelicidin in healthy adults.J Allergy Clin Immunol. 2011; 127 (e1301): 1302-1304Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar, 7Leow L. Simpson T. Cursons R. Karalus N. Hancox R.J. Vitamin D, innate immunity and outcomes in community acquired pneumonia.Respirology. 2011; 16: 611-616Crossref PubMed Scopus (87) Google Scholar In a study of 60 healthy adults, Bhan et al6Bhan I. Camargo Jr., C.A. Wenger J. Ricciardi C. Ye J. Borregaard N. et al.Circulating levels of 25-hydroxyvitamin D and human cathelicidin in healthy adults.J Allergy Clin Immunol. 2011; 127 (e1301): 1302-1304Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar found no significant correlation between 25(OH)D and hCAP-18 among adults with 25(OH)D levels of more than 32 ng/mL (r = 0.12; P = .58), but among adults with 25(OH)D levels of 32 ng/mL or less, there was a significant correlation (r = 0.45; P = .005).Associations between 25(OH)D levels and specific viral etiology have been recognized,8Mansbach J.M. Camargo Jr., C.A. Acute respiratory infections.in: Litonjua A. Vitamin D and lung: mechanism and disease associations. Humana, New York, NY2012: 181-200Crossref Scopus (3) Google Scholar but the association between hCAP-18 levels and viral etiology is novel. In our data, children with lower hCAP-18 levels were significantly more likely to have RSV bronchiolitis than HRV bronchiolitis. Although the pathogenesis of this relationship is beyond the scope of our data, children with low hCAP-18 levels may be more susceptible to RSV or alternatively, the hCAP-18 levels may be lowered in the presence of RSV.Importantly, hCAP-18 levels have been associated previously with clinical outcomes. For example, lower serum hCAP-18 levels (mean, 619 ± 329 ng/mL) at the initiation of chronic hemodialysis were independently associated with increased 1-year mortality (odds ratio, 2.6; 95% CI, 1.4-5.0) due to infection.9Gombart A.F. Bhan I. Borregaard N. Tamez H. Camargo Jr., C.A. Koeffler H.P. et al.Low plasma level of cathelicidin antimicrobial peptide (hCAP18) predicts increased infectious disease mortality in patients undergoing hemodialysis.Clin Infect Dis. 2009; 48: 418-424Crossref PubMed Scopus (123) Google Scholar Furthermore, in adults hospitalized with community-acquired pneumonia, lower values of serum cathelicidin (median, 69 ng/mL; range, 13-263) were marginally associated with a higher 30-day mortality in unadjusted analyses (P = .053).7Leow L. Simpson T. Cursons R. Karalus N. Hancox R.J. Vitamin D, innate immunity and outcomes in community acquired pneumonia.Respirology. 2011; 16: 611-616Crossref PubMed Scopus (87) Google Scholar In our data, lower hCAP-18 levels were independently associated with bronchiolitis hospitalization for 24 hours or more, but the reasons for the variability in serum hCAP-18 values between the 2 cited studies and our data are unclear.In this prospective study of children presenting to the ED with bronchiolitis, most children had normal 25(OH)D levels. However, their hCAP-18 levels varied widely and, for the first time, we identified that low levels of hCAP-18, rather than 25(OH)D levels, were associated with RSV-only infections and an increased severity of bronchiolitis. When examining the association between vitamin D status and infectious disease outcomes, hCAP-18 levels may provide an additional, clinically relevant biomarker, especially in populations with normal 25(OH)D levels. Bronchiolitis is a common childhood acute respiratory infection (ARI) and the leading cause of hospitalization for US infants.1Subcommittee on Diagnosis and Management of BronchiolitisDiagnosis and management of bronchiolitis.Pediatrics. 2006; 118: 1774-1793Crossref PubMed Scopus (852) Google Scholar The 2 most common viral etiologies of severe bronchiolitis (ie, bronchiolitis requiring hospitalization) are respiratory syncytial virus (RSV) and human rhinovirus (HRV).2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google Scholar Although low serum 25-hydroxyvitamin D (25[OH]D) levels have been associated with the increased incidence and severity of ARI, randomized controlled trials of vitamin D supplementation have demonstrated mixed results for the prevention of ARIs.3Bartley J. Vitamin D, innate immunity and upper respiratory tract infection.J Laryngol Otol. 2010; 124: 465-469Crossref PubMed Scopus (62) Google Scholar Nonetheless, vitamin D status continues to garner attention as a modifiable risk factor for infectious diseases because it plays a central role in the innate immune system. Hydroxylation of 25(OH)D creates 1,25-dihydroxyvitamin D, which in vitro increases the transcription of the innate immune protein, human cathelicidin antimicrobial peptide 18 (hCAP-18).4Liu P.T. Stenger S. Li H. Wenzel L. Tan B.H. Krutzik S.R. et al.Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response.Science. 2006; 311: 1770-1773Crossref PubMed Scopus (2947) Google Scholar Bronchial epithelial cells and circulating white blood cells produce hCAP-18,5Adams J.S. Hewison M. Unexpected actions of vitamin D: new perspectives on the regulation of innate and adaptive immunity.Nat Clin Pract Endocrinol Metab. 2008; 4: 80-90Crossref PubMed Scopus (608) Google Scholar which is capable of killing a wide variety of viral and bacterial pathogens.3Bartley J. Vitamin D, innate immunity and upper respiratory tract infection.J Laryngol Otol. 2010; 124: 465-469Crossref PubMed Scopus (62) Google Scholar Although 25(OH)D levels are the best measure of overall vitamin D status, it is 1,25-dihydroxyvitamin D that drives the production of hCAP-18. Therefore, when examining the association between vitamin D and infectious disease outcomes, hCAP-18 may provide additional data. As part of a prospective, multicenter study enrolling children younger than 2 years hospitalized with bronchiolitis November through March,2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google Scholar study investigators at 1 Boston site also enrolled children with bronchiolitis discharged home from the emergency department (ED). For all participants at this site, investigators collected clinical data, blood samples, and nasopharyngeal aspirates. Serum 25(OH)D concentration was measured by liquid chromatography-tandem mass spectrometry. ELISA was used to measure serum levels of hCAP-18 (see this article's Online Repository at www.jacionline.org). The nasopharyngeal aspirates were tested for 15 viruses by using real-time PCR.2Mansbach J.M. Piedra P.A. Teach S.J. Sullivan A.F. Forgey T. Clark S. et al.Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis.Arch Pediatr Adolesc Med. 2012; 166: 700-706Crossref PubMed Scopus (239) Google Scholar We hypothesized that hCAP-18 levels would not be associated with the viral etiology of bronchiolitis but that children with low hCAP-18 levels would more likely be hospitalized for 24 or more hours. For the latter hypothesis, we divided the children into 2 groups: 1) discharged home from the ED or hospitalized for less than 24 hours and 2) hospitalized for 24 hours or more. Analysis used descriptive statistics and multivariable logistic regression. This study was approved by the Boston Children's Hospital institutional review board. Of 82 enrolled children, 33 (40%) were discharged home from the ED or hospitalized for less than 24 hours and 49 (60%) were hospitalized for 24 hours or more. Overall, the median age was 5 months (interquartile range, 2-10); 46 (56%) were boys; 39 (47%) were white, 21 (26%) were black, and 22 (27%) were of other or unknown races; 35 (43%) had Hispanic ethnicity. Furthermore, median (interquartile range) levels of key serum tests were as follows: 25(OH)D 34 ng/mL (28-40) and hCAP-18 218 ng/mL (130-382). The 2 most commonly identified viruses were RSV (76%) and HRV (18%). Both RSV and HRV were identified in 6% of the children, and no virus was identified in 5% of the children. There was neither a significant correlation between 25(OH)D and hCAP-18 levels (ρ = −0.12; P = .26) nor a significant association between 25(OH)D and hospitalization for 24 hours or more (P = .50). Median hCAP-18 levels were lower among children with RSV only or RSV in combination with non-HRV viruses than among children with HRV only or HRV in combination with non-RSV viruses (median [interquartile range], 159 ng/mL [118-243] vs 497 ng/mL [401-577]; P < .001). Interestingly, the median hCAP-18 level for the 5 children in whom both RSV and HRV were identified was between these 2 values (382 ng/mL [296-406]). There was no association between 25(OH)D levels and viral etiology. As shown in Table I, children with hCAP-18 levels less than the median (<218 ng/mL) were significantly more likely to be hospitalized for 24 hours or more than were children with hCAP-18 levels above the median (78% vs 41%; P = .001). In multivariable analysis (Table II) adjusting for age, sex, and race, children with serum hCAP-18 levels of less than 218 ng/mL were more likely to be hospitalized for 24 hours or more (adjusted odds ratio, 5.7; 95% CI, 2.0-16.2; P = .001). Premature birth was excluded from the final multivariable model because it was not significantly associated with hCAP-18 values (Table I) and did not materially change the results of other model factors. We did not collect information about prior ARIs. One possible reason that we found no relationship between the 25(OH)D and hCAP-18 levels is that the majority of children had 25(OH)D levels of more than 30 ng/mL.6Bhan I. Camargo Jr., C.A. Wenger J. Ricciardi C. Ye J. Borregaard N. et al.Circulating levels of 25-hydroxyvitamin D and human cathelicidin in healthy adults.J Allergy Clin Immunol. 2011; 127 (e1301): 1302-1304Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar, 7Leow L. Simpson T. Cursons R. Karalus N. Hancox R.J. Vitamin D, innate immunity and outcomes in community acquired pneumonia.Respirology. 2011; 16: 611-616Crossref PubMed Scopus (87) Google Scholar In a study of 60 healthy adults, Bhan et al6Bhan I. Camargo Jr., C.A. Wenger J. Ricciardi C. Ye J. Borregaard N. et al.Circulating levels of 25-hydroxyvitamin D and human cathelicidin in healthy adults.J Allergy Clin Immunol. 2011; 127 (e1301): 1302-1304Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar found no significant correlation between 25(OH)D and hCAP-18 among adults with 25(OH)D levels of more than 32 ng/mL (r = 0.12; P = .58), but among adults with 25(OH)D levels of 32 ng/mL or less, there was a significant correlation (r = 0.45; P = .005). Associations between 25(OH)D levels and specific viral etiology have been recognized,8Mansbach J.M. Camargo Jr., C.A. Acute respiratory infections.in: Litonjua A. Vitamin D and lung: mechanism and disease associations. Humana, New York, NY2012: 181-200Crossref Scopus (3) Google Scholar but the association between hCAP-18 levels and viral etiology is novel. In our data, children with lower hCAP-18 levels were significantly more likely to have RSV bronchiolitis than HRV bronchiolitis. Although the pathogenesis of this relationship is beyond the scope of our data, children with low hCAP-18 levels may be more susceptible to RSV or alternatively, the hCAP-18 levels may be lowered in the presence of RSV. Importantly, hCAP-18 levels have been associated previously with clinical outcomes. For example, lower serum hCAP-18 levels (mean, 619 ± 329 ng/mL) at the initiation of chronic hemodialysis were independently associated with increased 1-year mortality (odds ratio, 2.6; 95% CI, 1.4-5.0) due to infection.9Gombart A.F. Bhan I. Borregaard N. Tamez H. Camargo Jr., C.A. Koeffler H.P. et al.Low plasma level of cathelicidin antimicrobial peptide (hCAP18) predicts increased infectious disease mortality in patients undergoing hemodialysis.Clin Infect Dis. 2009; 48: 418-424Crossref PubMed Scopus (123) Google Scholar Furthermore, in adults hospitalized with community-acquired pneumonia, lower values of serum cathelicidin (median, 69 ng/mL; range, 13-263) were marginally associated with a higher 30-day mortality in unadjusted analyses (P = .053).7Leow L. Simpson T. Cursons R. Karalus N. Hancox R.J. Vitamin D, innate immunity and outcomes in community acquired pneumonia.Respirology. 2011; 16: 611-616Crossref PubMed Scopus (87) Google Scholar In our data, lower hCAP-18 levels were independently associated with bronchiolitis hospitalization for 24 hours or more, but the reasons for the variability in serum hCAP-18 values between the 2 cited studies and our data are unclear. In this prospective study of children presenting to the ED with bronchiolitis, most children had normal 25(OH)D levels. However, their hCAP-18 levels varied widely and, for the first time, we identified that low levels of hCAP-18, rather than 25(OH)D levels, were associated with RSV-only infections and an increased severity of bronchiolitis. When examining the association between vitamin D status and infectious disease outcomes, hCAP-18 levels may provide an additional, clinically relevant biomarker, especially in populations with normal 25(OH)D levels. We thank Tate F. Forgey, MA, and Ashley F. Sullivan, MS, MPH, for coordinating the project and Claire L. Kelland, MSc, and Charlotte Horn for their technical assistance. Details of hCAP ELISAhCAP-18 is quantitated by ELISA with recombinant hCAP-18 as standard. Although the level of hCAP-18 in the serum has been found to be equivalent to the level in plasma, the development of ELISA was performed by using plasma.E1Sorensen O. Cowland J.B. Askaa J. Borregaard N. An ELISA for hCAP-18, the cathelicidin present in human neutrophils and plasma.J Immunol Methods. 1997; 206: 53-59Crossref PubMed Scopus (169) Google Scholar This ELISA was found to have a detection limit of 0.084 ng/mL with an intra- and interassay coefficient of variation of 6.3% or less. The details of this laboratory test are described in an article by Sorensen et al.E1Sorensen O. Cowland J.B. Askaa J. Borregaard N. An ELISA for hCAP-18, the cathelicidin present in human neutrophils and plasma.J Immunol Methods. 1997; 206: 53-59Crossref PubMed Scopus (169) Google Scholar hCAP-18 is quantitated by ELISA with recombinant hCAP-18 as standard. Although the level of hCAP-18 in the serum has been found to be equivalent to the level in plasma, the development of ELISA was performed by using plasma.E1Sorensen O. Cowland J.B. Askaa J. Borregaard N. An ELISA for hCAP-18, the cathelicidin present in human neutrophils and plasma.J Immunol Methods. 1997; 206: 53-59Crossref PubMed Scopus (169) Google Scholar This ELISA was found to have a detection limit of 0.084 ng/mL with an intra- and interassay coefficient of variation of 6.3% or less. The details of this laboratory test are described in an article by Sorensen et al.E1Sorensen O. Cowland J.B. Askaa J. Borregaard N. An ELISA for hCAP-18, the cathelicidin present in human neutrophils and plasma.J Immunol Methods. 1997; 206: 53-59Crossref PubMed Scopus (169) Google Scholar
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