Serum Bovine Immunoglobulins Improve Inflammation and Gut Barrier Function in Persons with HIV and Enteropathy on Suppressive ART

Main Article Content

Netanya Sandler Utay
Anoma Somasunderam
John E. Hinkle
Bryon W. Petschow
Christopher J. Detzel
Ma Somsouk
Carl J. Fichtenbaum
Eric M. Weaver
Audrey L. Shaw
David M. Asmuth


Background: Systemic inflammation persists in chronic HIV infection and is associated with increased rates of non-AIDS events such as cardiovascular and liver disease. Increased gut permeability and systemic exposure to microbial products are key drivers of this inflammation. Serum-derived bovine immunoglobulin/protein isolate (SBI) supports gut healing in other conditions such as inflammatory bowel disease.

Methods: In this randomized, double-blind study, participants receiving suppressive antiretroviral therapy (ART) with chronic diarrhea received placebo or SBI at 2.5 g BID or 5 g BID for 4 weeks, followed by a 20-week placebo-free extension phase with SBI at either 2.5 or 5 g BID. Intestinal fatty acid binding protein (I-FABP), zonulin, flagellin, lipopolysaccharide (LPS) and LPS-binding protein, and inflammatory markers were measured by ELISA or multiplex assays. Non-parametric tests were used for analysis.

Results: One hundred three participants completed the study. By week 24 SBI significantly decreased circulating levels of I-FABP (-0.35 ng/mL, P = 0.002) and zonulin (-4.90 ng/mL, P = 0.003), suggesting improvement in gut damage, and interleukin-6 (IL-6) (-0.40 pg/mL, P = 0.002), reflecting improvement in systemic inflammation. In participants with the lowest quartile of CD4+ T-cell counts at baseline (189-418 cells/mL), CD4+ T-cell counts increased significantly (26 cells/mL; P = 0.002).

Conclusions: Oral SBI may decrease inflammation and warrants further exploration as a potential strategy to improve gut integrity and decrease systemic inflammation among persons receiving prolonged suppressive ART.

Keywords: HIV infection; CD4 T cell; Serum bovine immunoglobulin protein; Interleukin; Inflammation; Intestine; I-FABP


Download data is not yet available.

Article Details

Author Biography

Netanya Sandler Utay, Department of Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX

Department of Medicine

Assistant Professor


1. Sandler NG, Douek DC. Microbial translocation in HIV infection: causes, consequences and treatment opportunities. Nat Rev Microbiol. 2012;10(9):655-66. PubMed PMID: 22886237. doi: 10.1038/nrmicro2848

2. Hunt PW, Sinclair E, Rodriguez B, Shive C, Clagett B, Funderburg N, Robinson J, Huang Y, Epling L, Martin JN, Deeks SG, Meinert CL, Van Natta ML, Jabs DA, Lederman MM. Gut epithelial barrier dysfunction and innate immune activation predict mortality in treated HIV infection. J Infect Dis. 2014;210(8):1228-38. PubMed PMID: 24755434. Pubmed Central PMCID: PMC4192038. doi: 10.1093/infdis/jiu238

3. Funderburg NT, Andrade A, Chan ES, Rosenkranz SL, Lu D, Clagett B, Pilch-Cooper HA, Rodriguez B, Feinberg J, Daar E, Mellors J, Kuritzkes D, Jacobson JM, Lederman MM. Dynamics of immune reconstitution and activation markers in HIV+ treatment-naive patients treated with raltegravir, tenofovir disoproxil fumarate and emtricitabine. PLoS One. 2013;8(12):e83514. PubMed PMID: 24367599. Pubmed Central PMCID: Pmc3867440. doi: 10.1371/journal.pone.0083514

4. Rasmussen LD, May MT, Kronborg G, Larsen CS, Pedersen C, Gerstoft J, Obel N. Time trends for risk of severe age-related diseases in individuals with and without HIV infection in Denmark: a nationwide population-based cohort study. Lancet HIV. 2015;2(7):e288-98. PubMed PMID: 26423253. doi: 10.1016/s2352-3018(15)00077-6

5. Tenorio AR, Zheng Y, Bosch RJ, Krishnan S, Rodriguez B, Hunt PW, Plants J, Seth A, Wilson CC, Deeks SG, Lederman MM, Landay AL. Soluble markers of inflammation and coagulation but not T-cell activation predict non-AIDS-defining morbid events during suppressive antiretroviral treatment. J Infect Dis. 2014;210(8):1248-59. PubMed PMID: 24795473. Pubmed Central PMCID: Pmc4192039. doi: 10.1093/infdis/jiu254

6. Perez-Bosque A, Miro L, Maijo M, Polo J, Campbell J, Russell L, Crenshaw J, Weaver E, Moreto M. Dietary intervention with serum-derived bovine immunoglobulins protects barrier function in a mouse model of colitis. American Journal of Physiology: Gastrointestinal and Liver Physiology. 2015;308(12):G1012-8. PubMed PMID: 25882614. doi: 10.1152/ajpgi.00378.2014

7. Henderson AL, Brand MW, Darling RJ, Maas KJ, Detzel CJ, Hostetter J, Wannemuehler MJ, Weaver EM. Attenuation of Colitis by Serum-Derived Bovine Immunoglobulin/Protein Isolate in a Defined Microbiota Mouse Model. Digestive Diseases and Sciences. 2015;60(11):3293-303. PubMed PMID: 26026602. Pubmed Central PMCID: PMC4621698. doi: 10.1007/s10620-015-3726-5

8. Wilson D, Evans MD, Weaver E, Shaw AL, Klein GL. Evaluation of Serum-Derived Bovine Immunoglobulin Protein Isolate in Subjects with Diarrhea-Predominant Irritable Bowel Syndrome. Clinical Medicine Insights: Gastroenterology. 2013;6:49-60.

9. Weinstock LB, Jasion VS. Serum-Derived Bovine Immunoglobulin/Protein Isolate Therapy for Patients with Refractory Irritable Bowel Syndrome. Open Journal of Gastroenterology. 2014;4:329-34.

10. Shafran I, Burgunder P, Wei D, Young HE, Klein G, Burnett BP. Management of inflammatory bowel disease with oral serum-derived bovine immunoglobulin. Therapeutic Advances in Gastroenterology. 2015;8(6):331-9. PubMed PMID: 26557889. Pubmed Central PMCID: PMC4622288. doi: 10.1177/1756283X15593693

11. Horgan A, Maas KJ, Henderson A, Detzel CJ, Weaver EM. Serum-derived bovine immunoglobulin/protein isolate binds to pathogen-associated molecular patterns. FASEB Journal. 2014; 128: Suppl No. 1; 836.6.

12. Weaver EM, Klein GL, DeVries BK, Maas KJ, Shaw AL. Endotoxin Neutralization activity (ENA) of bovine plasma and bovine Immunoglobulin (IgG)-rich fractions as compared to human plasma. FASEB Journal. 2013;27:1079.58.

13. Detzel CJ, Horgan A, Henderson AL, Petschow BW, Warner CD, Maas KJ, Weaver EM. Bovine immunoglobulin/protein isolate binds pro-inflammatory bacterial compounds and prevents immune activation in an intestinal co-culture model. PloS One. 2015;10(4):e0120278. PubMed PMID: 25830826. Pubmed Central PMCID: PMC4382133. doi: 10.1371/journal.pone.0120278

14. Petschow BW, Blikslager AT, Weaver EM, Campbell JM, Polo J, Shaw AL, Burnett BP, Klein GL, Rhoads JM. Bovine immunoglobulin protein isolates for the nutritional management of enteropathy. World Journal of Gastroenterology. 2014;20(33):11713-26. PubMed PMID: 25206275. Pubmed Central PMCID: 4155361. doi: 10.3748/wjg.v20.i33.11713

15. Asmuth DM, Ma ZM, Albanese A, Sandler NG, Devaraj S, Knight TH, Flynn NM, Yotter T, Garcia JC, Tsuchida E, Wu TT, Douek DC, Miller CJ. Oral Serum-Derived Bovine Immunoglobulin Improves Duodenal Immune Reconstitution and Absorption Function in Patients with HIV Enteropathy. AIDS. 2013;27:2207-17. PubMed PMID: 23660579. Pubmed Central PMCID: 3754419. doi: 10.1097/QAD.0b013e328362e54c

16. Asmuth DM, Hinkle JE, LaMarca A, Fichtenbaum CJ, Somsouk M, Utay NS, Shaw AL, Petschow BW, Detzel CJ, Weaver EM. Evaluation of oral serum-derived bovine immunoglobulins in HIV-infected patients with chronic idiopathic diarrhea. HIV Clinical Trials. 2017;18(5-6):205-13. PubMed PMID: 29210625. doi: 10.1080/15284336.2017.1401256

17. Rothman KJ. No adjustments are needed for multiple comparisons. Epidemiology. 1990;1(1):43-6. PubMed PMID: 2081237.

18. Pelsers MM, Namiot Z, Kisielewski W, Namiot A, Januszkiewicz M, Hermens WT, Glatz JF. Intestinal-type and liver-type fatty acid-binding protein in the intestine. Tissue distribution and clinical utility. Clin Biochem. 2003;36(7):529-35. PubMed PMID: 14563446.

19. Fasano A. Zonulin and Its Regulation of Intestinal Barrier Function: The Biological Door to Inflammation, Autoimmunity, and Cancer. Physiological Reviews. 2011;91:151-75. doi: 10.1152/physrev.00003.2008

20. Perez-Bosque A, Miro L, Maijo M, Polo J, Campbell JM, Russell L, Crenshaw JD, Weaver E, Moreto M. Oral Serum-Derived Bovine Immunoglobulin/Protein Isolate Has Immunomodulatory Effects on the Colon of Mice that Spontaneously Develop Colitis. PLoS One. 2016;11(5):e0154823. PubMed PMID: 27139220. Pubmed Central PMCID: Pmc4854409. doi: 10.1371/journal.pone.0154823

21. Valentin N, Camilleri M, Carlson P, Harrington SC, Eckert D, O'Neill J, Burton D, Chen J, Shaw AL, Acosta A. Potential mechanisms of effects of serum-derived bovine immunoglobulin/protein isolate therapy in patients with diarrhea-predominant irritable bowel syndrome. Physiol Rep. 2017;5(5). PubMed PMID: 28275113. Pubmed Central PMCID: Pmc5350178. doi: 10.14814/phy2.13170

22. Ananthakrishnan AN, Luo C, Yajnik V, Khalili H, Garber JJ, Stevens BW, Cleland T, Xavier RJ. Gut Microbiome Function Predicts Response to Anti-integrin Biologic Therapy in Inflammatory Bowel Diseases. Cell Host Microbe. 2017;21(5):603-10.e3. PubMed PMID: 28494241. Pubmed Central PMCID: Pmc5705050. doi: 10.1016/j.chom.2017.04.010

23. Li Y, Ostergaard MV, Jiang P, Chatterton DE, Thymann T, Kvistgaard AS, Sangild PT. Whey protein processing influences formula-induced gut maturation in preterm pigs. J Nutr. 2013;143(12):1934-42. PubMed PMID: 24047702. doi: 10.3945/jn.113.182931

24. Fasano A. Intestinal permeability and its regulation by zonulin: diagnostic and therapeutic implications. Clin Gastroenterol Hepatol. 2012;10(10):1096-100. PubMed PMID: 22902773. Pubmed Central PMCID: Pmc3458511. doi: 10.1016/j.cgh.2012.08.012

25. El Asmar R, Panigrahi P, Bamford P, Berti I, Not T, Coppa GV, Catassi C, Fasano A. Host-dependent zonulin secretion causes the impairment of the small intestine barrier function after bacterial exposure. Gastroenterology. 2002;123(5):1607-15. PubMed PMID: 12404235.

26. Mokkala K, Roytio H, Munukka E, Pietila S, Ekblad U, Ronnemaa T, Eerola E, Laiho A, Laitinen K. Gut Microbiota Richness and Composition and Dietary Intake of Overweight Pregnant Women Are Related to Serum Zonulin Concentration, a Marker for Intestinal Permeability. J Nutr. 2016;146(9):1694-700. PubMed PMID: 27466607. doi: 10.3945/jn.116.235358

27. Malickova K, Francova I, Lukas M, Kolar M, Kralikova E, Bortlik M, Duricova D, Stepankova L, Zvolska K, Pankova A, Zima T. Fecal zonulin is elevated in Crohn's disease and in cigarette smokers. Pract Lab Med. 2017;9:39-44. PubMed PMID: 29034305. Pubmed Central PMCID: Pmc5633835. doi: 10.1016/j.plabm.2017.09.001

28. Sarker P, Banik A, Stromberg R, Gudmundsson GH, Raqib R, Agerberth B. Treatment with Entinostat Heals Experimental Cholera by Affecting Physical and Chemical Barrier Functions of Intestinal Epithelia. Antimicrob Agents Chemother. 2017;61(7). PubMed PMID: 28438947. Pubmed Central PMCID: Pmc5487680. doi: 10.1128/aac.02570-16

29. Sereti I, Krebs SJ, Phanuphak N, Fletcher J, Slike B, Pinyakorn S, O'Connell R, Rupert A, Chomont N, Valcour V, Kim J, Robb M, Michael N, Douek D, Ananworanich J, Utay N. Initiation of antiretroviral therapy in early HIV infection reduces but does not abrogate chronic residual inflammation. Clin Infect Dis. 2016:Accepted for publication.

30. Hatano H, Hayes TL, Dahl V, Sinclair E, Lee TH, Hoh R, Lampiris H, Hunt PW, Palmer S, McCune JM, Martin JN, Busch MP, Shacklett BL, Deeks SG. A randomized, controlled trial of raltegravir intensification in antiretroviral-treated, HIV-infected patients with a suboptimal CD4+ T cell response. J Infect Dis. 2011;203(7):960-8. PubMed PMID: 21402547. Pubmed Central PMCID: PMC3068029. doi: 10.1093/infdis/jiq138

31. Hunt PW, Shulman NS, Hayes TL, Dahl V, Somsouk M, Funderburg NT, McLaughlin B, Landay AL, Adeyemi O, Gilman LE, Clagett B, Rodriguez B, Martin JN, Schacker TW, Shacklett BL, Palmer S, Lederman MM, Deeks SG. The immunologic effects of maraviroc intensification in treated HIV-infected individuals with incomplete CD4+ T-cell recovery: a randomized trial. Blood. 2013;121(23):4635-46. PubMed PMID: 23589670. Pubmed Central PMCID: PMC3685899. doi: 10.1182/blood-2012-06-436345

32. Castillo-Mancilla JR, Phillips AN, Neaton JD, Neuhaus J, Collins S, Mannheimer S, Pett S, Touzeau-Romer V, Polizzotto MN, Lundgren JD, Gardner EM, Group ISS. Association of Suboptimal Antiretroviral Therapy Adherence With Inflammation in Virologically Suppressed Individuals Enrolled in the SMART Study. Open Forum Infect Dis. 2018;5(1):ofx275. PubMed PMID: 29362724. Pubmed Central PMCID: PMC5772402. doi: 10.1093/ofid/ofx275

33. Hsu DC, Ma YF, Hur S, Li D, Rupert A, Scherzer R, Kalapus SC, Deeks S, Sereti I, Hsue PY. Plasma IL-6 levels are independently associated with atherosclerosis and mortality in HIV-infected individuals on suppressive antiretroviral therapy. Aids. 2016;30(13):2065-74. PubMed PMID: 27177313. Pubmed Central PMCID: Pmc5586221. doi: 10.1097/qad.0000000000001149

34. Nordell AD, McKenna M, Borges AH, Duprez D, Neuhaus J, Neaton JD. Severity of cardiovascular disease outcomes among patients with HIV is related to markers of inflammation and coagulation. J Am Heart Assoc. 2014;3(3):e000844. PubMed PMID: 24870935. Pubmed Central PMCID: Pmc4309077. doi: 10.1161/jaha.114.000844

35. Rodger AJ, Fox Z, Lundgren JD, Kuller LH, Boesecke C, Gey D, Skoutelis A, Goetz MB, Phillips AN. Activation and coagulation biomarkers are independent predictors of the development of opportunistic disease in patients with HIV infection. J Infect Dis. 2009;200(6):973-83. PubMed PMID: 19678756. Pubmed Central PMCID: Pmc2892757. doi: 10.1086/605447

36. Grund B, Baker JV, Deeks SG, Wolfson J, Wentworth D, Cozzi-Lepri A, Cohen CJ, Phillips A, Lundgren JD, Neaton JD. Relevance of Interleukin-6 and D-Dimer for Serious Non-AIDS Morbidity and Death among HIV-Positive Adults on Suppressive Antiretroviral Therapy. PLoS One. 2016;11(5):e0155100. PubMed PMID: 27171281. Pubmed Central PMCID: Pmc4865234. doi: 10.1371/journal.pone.0155100

37. Wada NI, Bream JH, Martinez-Maza O, Macatangay B, Galvin SR, Margolick JB, Jacobson LP. Inflammatory Biomarkers and Mortality Risk Among HIV-Suppressed Men: A Multisite Prospective Cohort Study. Clin Infect Dis. 2016. PubMed PMID: 27343547. doi: 10.1093/cid/ciw409

38. Kuller LH, Tracy R, Belloso W, De Wit S, Drummond F, Lane HC, Ledergerber B, Lundgren J, Neuhaus J, Nixon D, Paton NI, Neaton JD. Inflammatory and coagulation biomarkers and mortality in patients with HIV infection. PLoS Medicine. 2008;5(10):e203. PubMed PMID: 18942885.

39. Lederman MM, Calabrese L, Funderburg NT, Clagett B, Medvik K, Bonilla H, Gripshover B, Salata RA, Taege A, Lisgaris M, McComsey GA, Kirchner E, Baum J, Shive C, Asaad R, Kalayjian RC, Sieg SF, Rodriguez B. Immunologic failure despite suppressive antiretroviral therapy is related to activation and turnover of memory CD4 cells. Journal of Infectious Diseases. 2011;204(8):1217-26. PubMed PMID: 21917895. Pubmed Central PMCID: Pmc3218674. doi: 10.1093/infdis/jir507

40. Kasang C, Kalluvya S, Majinge C, Kongola G, Mlewa M, Massawe I, Kabyemera R, Magambo K, Ulmer A, Klinker H, Gschmack E, Horn A, Koutsilieri E, Preiser W, Hofmann D, Hain J, Muller A, Dolken L, Weissbrich B, Rethwilm A, Stich A, Scheller C. Effects of Prednisolone on Disease Progression in Antiretroviral-Untreated HIV Infection: A 2-Year Randomized, Double-Blind Placebo-Controlled Clinical Trial. PLoS One. 2016;11(1):e0146678. PubMed PMID: 26812052. Pubmed Central PMCID: Pmc4727920. doi: 10.1371/journal.pone.0146678

41. Corbeau P, Reynes J. Immune reconstitution under antiretroviral therapy: the new challenge in HIV-1 infection. Blood. 2011;117(21):5582-90. PubMed PMID: 21403129. doi: 10.1182/blood-2010-12-322453

42. Bucy RP, Hockett RD, Derdeyn CA, Saag MS, Squires K, Sillers M, Mitsuyasu RT, Kilby JM. Initial increase in blood CD4(+) lymphocytes after HIV antiretroviral therapy reflects redistribution from lymphoid tissues. Journal of Clinical Investigation. 1999;103(10):1391-8. PubMed PMID: 10330421. Pubmed Central PMCID: PMC408455. doi: 10.1172/JCI5863

43. Benveniste O, Flahault A, Rollot F, Elbim C, Estaquier J, Pedron B, Duval X, Dereuddre-Bosquet N, Clayette P, Sterkers G, Simon A, Ameisen JC, Leport C. Mechanisms involved in the low-level regeneration of CD4+ cells in HIV-1-infected patients receiving highly active antiretroviral therapy who have prolonged undetectable plasma viral loads. Journal of Infectious Diseases. 2005;191(10):1670-9. PubMed PMID: 15838794. doi: 10.1086/429670

44. Sandler NG, Zhang X, Bosch RJ, Funderburg NT, Choi AI, Robinson JK, Fine DM, Coombs RW, Jacobson JM, Landay AL, Douek DC, Tressler R, Read SW, Wilson CC, Deeks SG, Lederman MM, Gandhi RT. Sevelamer does not decrease lipopolysaccharide or soluble CD14 levels but decreases soluble tissue factor, low-density lipoprotein (LDL) cholesterol, and oxidized LDL cholesterol levels in individuals with untreated HIV infection. J Infect Dis. 2014;210(10):1549-54. PubMed PMID: 24864123. Pubmed Central PMCID: Pmc4215074. doi: 10.1093/infdis/jiu305

45. Tenorio AR, Chan ES, Bosch RJ, Macatangay BJ, Read SW, Yesmin S, Taiwo B, Margolis DM, Jacobson JM, Landay AL, Wilson CC. Rifaximin has a marginal impact on microbial translocation, T-cell activation and inflammation in HIV-positive immune non-responders to antiretroviral therapy - ACTG A5286. J Infect Dis. 2015;211(5):780-90. PubMed PMID: 25214516. Pubmed Central PMCID: Pmc4334803. doi: 10.1093/infdis/jiu515

46. Somsouk M, Dunham RM, Cohen M, Albright R, Abdel-Mohsen M, Liegler T, Lifson J, Piatak M, Gorelick R, Huang Y, Wu Y, Hsue PY, Martin JN, Deeks SG, McCune JM, Hunt PW. The immunologic effects of mesalamine in treated HIV-infected individuals with incomplete CD4+ T cell recovery: a randomized crossover trial. PLoS One. 2014;9(12):e116306. PubMed PMID: 25545673. Pubmed Central PMCID: Pmc4283685. doi: 10.1371/journal.pone.0116306

47. Bandera A, De Benedetto I, Bozzi G, Gori A. Altered gut microbiome composition in HIV infection: causes, effects and potential intervention. Curr Opin HIV AIDS. 2018;13(1):73-80. PubMed PMID: 29045252. doi: 10.1097/coh.0000000000000429

48. Nixon DE, Bosch RJ, Chan ES, Funderburg NT, Hodder S, Lake JE, Lederman MM, Klingman KL, Aberg JA. Effects of atorvastatin on biomarkers of immune activation, inflammation, and lipids in virologically suppressed, human immunodeficiency virus-1-infected individuals with low-density lipoprotein cholesterol < 130 mg/dL (AIDS Clinical Trials Group Study A5275). J Clin Lipidol. 2017;11(1):61-9. PubMed PMID: 28391912. Pubmed Central PMCID: Pmc5407297. doi: 10.1016/j.jacl.2016.09.017

49. Piconi S, Trabattoni D, Gori A, Parisotto S, Magni C, Meraviglia P, Bandera A, Capetti A, Rizzardini G, Clerici M. Immune activation, apoptosis, and Treg activity are associated with persistently reduced CD4+ T-cell counts during antiretroviral therapy. Aids. 2010;24(13):1991-2000. PubMed PMID: 20651586. doi: 10.1097/QAD.0b013e32833c93ce

50. McComsey GA, Whalen CC, Mawhorter SD, Asaad R, Valdez H, Patki AH, Klaumunzner J, Gopalakrishna KV, Calabrese LH, Lederman MM. Placebo-controlled trial of prednisone in advanced HIV-1 infection. Aids. 2001;15(3):321-7. PubMed PMID: 11273211.

51. Funderburg NT, Jiang Y, Debanne SM, Labbato D, Juchnowski S, Ferrari B, Clagett B, Robinson J, Lederman MM, McComsey GA. Rosuvastatin reduces vascular inflammation and T-cell and monocyte activation in HIV-infected subjects on antiretroviral therapy. J Acquir Immune Defic Syndr. 2015;68(4):396-404. PubMed PMID: 25514794. Pubmed Central PMCID: Pmc4334694. doi: 10.1097/qai.0000000000000478

52. Hsue P, Deeks SG, Ishai AE, Hur S, Li D, Sterman F, Lalezari J, Rupert A, Ganz P, Tawakol A. IL-1β inhibition significantly reduces atherosclerotic inflammation in treated HIV. Conference on Retroviruses and Opportunistic Infections. 2017:126.

53. Desai A, Grolleau-Julius A, Yung R. Leukocyte function in the aging immune system. Journal of Leukocyte Biology. 2010;87(6):1001-9. PubMed PMID: 20200405. Pubmed Central PMCID: PMC4057658. doi: 10.1189/jlb.0809542

54. Gutierrez F, Padilla S, Masia M, Iribarren JA, Moreno S, Viciana P, Hernandez-Quero J, Aleman R, Vidal F, Salavert M, Blanco JR, Leal M, Dronda F, Perez Hoyos S, del Amo J, Co RM. Patients' characteristics and clinical implications of suboptimal CD4 T-cell gains after 1 year of successful antiretroviral therapy. Curr HIV Res. 2008;6(2):100-7. PubMed PMID: 18336257.

Most read articles by the same author(s)