Human SAA ELISA Kit

RACTIVITY	Human
SENSITIVITY	<1.1 ng/mL
ASSAY RANGE	1.1-80 ng/mL
REAGENTS PROVIDED	SAA MICROTITER PLATE  SAA CONJUGATE SAA STANDARD CALIBRATOR DILUENT I CALIBRATOR DILUENT II WASH BUFFER (20X/96 wells, 30X/192 wells) SUBSTRATE A SUBSTRATE B STOP SOLUTION

INTENDED USE

This Human SAA ELISA Kit is to be used for the in vitro quantitative determination of human serum amyloid A (SAA) concentrations in serum, plasma, cell culture supernatant, and other biological fluids.  This kit is intended FOR LABORTORY RESEARCH USE ONLY and is not for use in diagnostic or therapeutic procedures.

INTRODUCTION

Serum Amyloid A (SAA) is an acute-phase protein.  During acute events, the rise in SAA levels is the most rapid and intense increase of all acute phase proteins.  Cytokines such as IL-1, IL-6, and TNF are considered mediators of SAA protein synthesis.  They stimulate hepatocytes in the liver to produce and release SAA into the bloodstream.  When elevated above normal levels SAA is almost exclusively bound to High Density Lipoproteins (HDL), causing SAA to behave like an apolipoprotein - a protein moiety occurring in plasma lipoprotiens.  SAA circulates at trace levels (1-5 µg/mL) during normal conditions; however 4-6 hours after inflammatory stimulus, SAA levels can increase by as much as 1000 fold to remarkably elevated levels (500-1000 µg/mL), thus making SAA a sensitive marker. ^1,2 

Structural analysis revealed this 104 amino acid (a.a.) polypeptide in its native state has a molecular mass of 12-14 kDa.  Serum amyloid A is the serum precursor of amyloid A (AA) protein (8.5 kDa), which is formed when the first 76 a.a.'s of SAA are cleaved.  The human SAA protein is polymorphic being made up of a family of several related proteins (SAA₁ to SAA₄).  SAA genes are located on chromosome 11p.¹ SAA₁ and SAA₂ are similar genes, which differ by 7 amino acids or more, and encode acute-phase SAA's.  SAA₃ appears to be a pseudogene and is substantially different from the others.  SAA₄ does not vary significantly during the acute phase response and is an isoform that is present on HDL during homeostasis.^3,4   Each of the acute phase proteins have a unique function in modulating host immune responses but the role of SAA remains unclear.  It is known that HDL inhibits SAA's function.  This suggests that SAA needs to be released from HDL complexes in order to become active.⁵ Recently it was reported that SAA may have an important pro-inflammatory and immunostimulating role by recruiting neutrophils, monocytes, and T-lymphocytes into inflammatory lesions.^5,6  As a result of SAA's association with HDL, a role in cholesterol metabolism has been proposed.  SAA, after dissociation from HDL, may play a role in cholesterol transport at local tissues sites during inflammation by binding cholesterol.^2,7

High levels of SAA can be seen in patients with acute and chronic inflammation. Secondary amyloidosis may develop as a result prolonged or repeated inflammatory conditions in which SAA levels remain elevated.  This progressive, fatal condition is characterized by a gradual loss of organ function, in which fibrils are deposited in peripheral tissues and major organs.  The fibrils are caused by the incomplete degradation of SAA in which the AA fragment (8.5 kDa) from the original SAA protein has been enzymatically cleaved.  Measuring SAA levels in these patients may be a useful indicator of degree of inflammation and response to therapy.  Inflammatory disorders such as rheumatoid arthritis, juvenile arthritis, ankylosing spondylitis, familial

mediterranean fever, progressive sclerosis as well as chronic infections such as tuberculosis and osteomyelitis are predisposed to developing amyloidosis.^8,9  Measuring SAA levels is also significant in determining pulmonary inflammation in patients with cystic fibrosis,¹⁰ diagnosing and predicting renal allograft rejection,¹¹ determining anti-microbial therapy response in urinary tract infections,¹² opportunistic infections in AIDS,¹³ inflammation in acute viral infections,¹⁴ biocompatiblility of hemodialysis,¹⁵ tissue damage in post-acute myocardial infarction, ¹⁷ and the outcome in severe unstable angina.¹⁶ Also, a differential diagnosis of inflammatory disease may be employed by measuring SAA levels.  Acute viral infections may be distinguished from bacterial infections by determining SAA levels.^14-17  It may be useful to confirm diagnosis of acute viral diseases if SAA is assayed at the same time as C-reactive protein, which is a useful inflammatory marker for bacterial infections and does not rise during viral disease.¹⁶ 

This SAA ELISA is a 2.5-hour solid phase immunoassay readily applicable to measure SAA in serum, plasma, cell culture supernatant, and other biological fluids in the range of 0 to 80 ng/mL.  It showed no cross reactivity with other cytokines tested.  This SAA ELISA is expected to be effectively used for further investigations into the relationship between SAA and the various conditions mentioned.

CITATIONS

1. Muriel Lavie et al. Serum amyloid A has antiviral activity against hepatitis C virus by inhibiting virus entry in a cell culture system. (2006) Hepatology. Volume 44, Issue 6, page 1626-1634.

2. Steven Bozinovski et al. Serum amyloid a is a biomarker of acute exacerbations of chronic obstructive pulmonary disease.  Am. J. Respir. Crit. Care Med. Vol. 177, No. 3 (2008), pp. 269-278.

3. Sander I. van Leuven et al. Enhanced atherogenesis and altered high density lipoprotein in patients with Crohn's disease. (2007) Journal of Lipid Research Volume 48. 2640-6.

4. Smith DJ et al. Reduced soluble receptor for advanced glycation end-products in COPD. (2011) Eur. Respir. J. 37(3):516-22.

5. Sukkar, MB.  Soluble RAGE is deficient in neutrophilic asthma and COPD.  (2012) Eur. Respir. J. 39(3):721-9.

6. Patricia G. Wilson et al. Serum Amyloid A, but Not C-Reactive Protein, Stimulates Vascular Proteoglycan Synthesis in a Pro-Atherogenic Manner.  Am J Pathol. Dec 2008; 173(6): 1902–1910.

7. Qiulin Liao et al. Serum proteome analysis for profiling protein markers associated with carcinogenesis and lymph node metastasis in nasopharyngeal carcinoma.  Clin Exp Metastasis. Jun 2008; 25(4): 465–476.

8. Hutchinson AF et al. Identifying viral infections in vaccinated Chronic Obstructive Pulmonary Disease (COPD) patients using clinical features and inflammatory markers. Influenza Other Respir Viruses. 2010 Jan; 4(1):33-9.

9. Nelson TL et al. Inflammatory markers are not altered by an eight week dietary alpha-linolenic acid intervention in healthy abdominally obese adult males and females. Cytokine. 2007 May; 38(2):101-6.

10. Johannes HM Levels et al. High-density lipoprotein proteome dynamics in human endotoxemia. Proteome Sci. 2011; 9: 34.

11. Wu TL et al.  Establishment of an in-house ELISA and the reference range for serum amyloid A (SAA): complementarity between SAA and C-reactive protein as markers of inflammation.  Clin Chim Acta. 2007 Feb; 376(1-2):72-6.

12. Leo Stockfelt et al. Short-term chamber exposure to low doses of two kinds of wood smoke does not induce systemic inflammation, coagulation or oxidative stress in healthy humans.  Inhal Toxicol. Jul 2013; 25(8): 417–425.

13. José L López-Campos et al. Determination of inflammatory biomarkers in patients with COPD: a comparison of different assays. BMC Med Res Methodol. 2012; 12: 40.

14. Anna A Richards et al. Birth Weight, Season of Birth and Postnatal Growth Do Not Predict Levels of Systemic Inflammation in Gambian Adults. Am J Hum Biol. Jul 2013; 25(4): 457–464.

15. Guojun Zhang et al.  Serum amyloid A: A new potential serum marker correlated with the stage of breast cancer.  Oncol Lett. Apr 1, 2012; 3(4): 940–944.

16. Hutchinson AF, Black J, Thompson MA, Bozinovski S, Brand CA, Smallwood DM, Irving LB, Anderson GP.Identifying viral infections in vaccinated Chronic Obstructive Pulmonary Disease (COPD) patients using clinical features and inflammatory markers. Influenza Other Respir Viruses 2010; 1(4):33-9.

17. Franssen R, Schimmel AW, van Leuven SI, Wolfkamp SC, Stroes ES, Dallinga-Thie GM.In Vivo Inflammation Does Not Impair ABCA1-Mediated Cholesterol Efflux Capacity of HDL. Cholesterol 2012; (2012):610741.

18. Stockley R, De Soyza A, Gunawardena K, Perrett J, Forsman-Semb K, Entwistle N, Snell N.Phase II study of a neutrophil elastase inhibitor (AZD9668) in patients with bronchiectasis. Respir Med 2013; 4(107):524-33.

19. Santoso A, Kaniawati M, Bakri S, Yusuf I. Secretory Phospholipase A2 Is Associated with the Odds of Acute Coronary Syndromes through Elevation of Serum Amyloid-A Protein. Int J Angiol 2013; 1(22):49-54.

20. Thompson JC, Jayne C, Thompson J, Wilson PG, Yoder MH, Webb N, Tannock LR. A brief elevation of serum amyloid A is sufficient to increase atherosclerosis. J Lipid Res 2015; 2(56):286-93.

20. Wilson PG, Thompson JC, Shridas P, McNamara PJ, de Beer MC, de Beer FC, Webb NR, Tannock LR.Serum Amyloid A Is an Exchangeable Apolipoprotein. Arterioscler Thromb Vasc Biol 2018; 8(38):1890-1900.

20. Arellano-Orden E, Calero C, López-Ramírez C, Sánchez-López V, López-Villalobos JL, Abad Arranz M, Blanco-Orozco A, Otero-Candelera R, López-Campos JL.Evaluation of lung parenchyma, blood vessels, and peripheral blood lymphocytes as a potential source of acute phase reactants in patients with COPD. Int J Chron Obstruct Pulmon Dis 2019; (14):1323-1332.

21. Stockfelt L, Sallsten G, Almerud P, Basu S, Barregard L.Short-term chamber exposure to low doses of two kinds of wood smoke does not induce systemic inflammation, coagulation or oxidative stress in healthy humans. Inhal Toxicol. 2013 Jul;25(8):417-25.