Antibodies to Tamm-Horsfall Protein Subunits ...

Eur J Clin Chem Clin Biochem 1996; 34:315-317 © 1996 by Walter de Gruyter · Berlin · New York

SHORT COMMUNICATION

Antibodies to Tamm-Horsfall Protein Subunits Prepared In Vitro, in Patients with Acute Pyelonephritis Bojan Jelakovic1, Jasminka Benkovic?, Nada Cikes1, Dusko Kuzmanic1, Tomislav Roncevic1 and Zeljko Krznaric1 1 2

Department of Medicine Clinical Institute of Laboratory Diagnosis University Hospital Center Zagreb, School of Medicine, University of Zagreb, Zagreb, Croatia

Summary: The aim of this study was to determine antibodies to Tamm-Horsfall protein subunits in patients with acute pyelonephritis. The protein subunits used in this determination were prepared by chemical treatment of Tamm-Horsfall protein isolated from the urine of healthy individuals. Values for IgG and IgA were significantly higher (p < 0.05 and p < 0.01 respectively) in patients than in healthy persons, while IgM class antibodies were significantly higher only in the test performed with subunits obtained with 8.3 mol/1 acetic acid (THP-A) (p < 0.05). Values for all three classes determined in the test with THP-A were significantly higher in patients with vesicoureteral reflux than in patients with normal radiological findings (p < 0.05). Antibodies to Tamm-Horsfall protein subunits isolated from the urine of patients with acute pyelonephritis should also be determined.

nosed on the basis of clinical picture and laboratory findings (> 10s bacteria of the same strain per 1 μΐ medium urine flow, erythrocyte sedimentation rate > 25 mm/h, body temperature > 38 °C, lumbar pain and sensitive succussion). Azotaemia was absent in all patients. The patients were divided in two groups on the basis of radiological examination. Twenty one patients (five male and 16 female) with normal radiological findings formed group I, while group II consisted of 4 female patients with vesicoureteral reflux (stage II-III). The control group consisted of 18 subjects who had never suffered from any renal disease and in whom the presence of acute urinary tract infection was ruled out by the history and clinical examination, and who were thus considered healthy.

Introduction

Tamm-Horsfall protein was isolated from the urine of healthy adult male and female subjects by multiple precipitation with 0.58 mmol/1 NaCl as described earlier (17).

The diagnostic procedures available nowadays are neither sufficiently sensitive nor specific to detect penetration of microorganisms into the interstitium and the consequent inflammation. Therefore, the diagnosis of acute pyelonephritis is mainly based on clinical experience (1,2). Since Tamm-Horsfall protein is synthesised in the epithelial cells of the ascending limb of Henle's loop and in the proximal part bf the distal tubule, i.e. in the part of the kidney most frequently damaged by pyelonephritis, many authors (3-8) have proposed that" Tamm-Horsfall protein could be involved in the pathogenesis of pyelonephritis and therefore useful in its diagnosis. Tamm-Horsfall protein is the most abundant protein in normal human urine, where it is found in the form of monomer subunits (Mr 80000) and mainly in the aggregate form (A/r 7 Χ 106). Its physiological role remains unclear (9). According to most authors (9-11) Tamm-Horsfall protein is a "hidden antigen" exposed to the immune system only after pathophysiological alterations. This may lead to formation of antibodies to Tamm-Horsfall protein. The role of antibodies to Tamm-Horsfall protein in the diagnosis of acute pyelonephritis (10—13) and in detection of vesicoureteral reflux (14-16) is still controversial. The presence of antibodies to Tamm-Horsfall protein in the serum of healthy adults and children implies that antibodies to the polymer molecule of Tamm-Horsfall protein may represent antibodies to other glycoproteins which are immunologically cross-reactive to Tamm-Horsfall protein. Therefore, we decided to determine antibodies to Tamm-Horsfall protein subunits, presuming that denaturation will probably reveal more specific epitopes thus allowing a more precise diagnosis of acute pyelonephritis. The protein subunits used in this determination were prepared by chemical treatment of Tamm-Horsfall protein isolated from the urine of healthy individuals.

Antibodies to Tamm-Horsfall protein were quantified by direct enzyme immunoassay according to the procedure proposed by Fasth et al. (10) and modified by Benkovic et al. (18). Tamm-Horsfall protein was denaturated with 0.0017 mol/1 sodium-dodecyl-sulphate (THP-S), with 6 mol/1 guanidine hydrochloride (THP-G), with 0.04 mol/1 urea (THP-U) and with 8.3 mol/1 acetic acid (ΤΗΡΑ). Microtitre plates (Behring, Marburg, Germany) were coated with those antigens (10 mg/1 in phosphate buffered saline, pH 7.4) for l h at 37 °C. After emptying the wells, human serum albumin (1 g/1 in phosphate buffered saline, Behring, Marburg, Germany) was added, then incubated for l h at 22 °C, to block the'free binding sites. Thereafter, the plates were washed three times with phosphate buffered saline-Tween 20 and twice with distilled water. Then, serum samples were diluted with phosphate buffered salineTween 20, and 100 μΐ were added per well (for the determination of IgA and IgG class antibodies the dilution was 1 : 5, and for IgM class antibodies 1:10). After incubation for l h at 22 °C, the plates were washed three times with phosphate buffered saline-Tween 20. Secondary antibodies labelled with alkaline phosphate (anti-human IgG, IgA and IgM, Sigma, St. Louis, USA) were then added, having first been diluted with phosphate buffered saline-Tween 20 (IgA, IgG and IgM class antibodies were diluted in the ratios 1 : 4000, 1 : 5000 and 1 : 25000, respectively). After 1-hour incubation at 22 °C and washing with phosphate buffered saline-Tween 20 three times, the substrate p-nitrophenylphosphate, 100 μΐ per well (1 g/1 in diethanolamine buffer, pH 9.8, Sigma, St. Louis, USA) was added. The plates were incubated for 1.5 h in the dark at 22 °C, and colour development interrupted by the addition of 3 mol/1 Na H, 200 μΐ per well (Kemika, Zagreb). Absorbancies were read on a Behring ELISA analyser at a wavelength of 405 nm.

Patients and Methods

The value of 4*blind test", i. e. the absorbance read for the wells coated with several Tamm-Horsfall protein subunits, and the value of unspecific binding, i. e. the absorbance read for the wells to which secondary antibodies had been added, were determined for each microtitre plate. Both values were determined on three occa-

Antibodies to Tamm-Horsfall protein were determined in 25 patients (five male and 20 female) with acute pyelonephritis diag-

Short communication

316 Tab. 1 Values of antibodies to Tamm-Horsfall protein subunits prepared in vitro, in healthy subjects (N = 18)

Discussion

Results

Some reports (10—12) indicate that antibodies to Tamm-Horsfall protein might be valuable in diagnosing acute pyelonephritis. Recently, we reported that determination of antibodies to the native polymer molecule of Tamm-Horsfall protein is of no value in the diagnosis of acute pyelonephritis (18). This is in agreement with results obtained by others (13, 14). As Tamm-Horsfall protein is synthesised as a monomer subunit, it is.Assumed that, following structural alterations due to infection and inflammation, subunits, rather than larger aggregates, penetrate into the interstitium. Therefore, we decided to determine antibodies to the subunits obtained in vitro by splitting the native molecule with different chemical agents, assuming that this would unmask immunologically different epitopes. Antibodies to the polymer molecule of TammHorsfall protein, as well as antibodies to the Tamm-Horsfall protein subunits obtained in vitro, were found in serum of healthy subjects. This could be the consequence of non-specific binding of secondary antibodies to Tamm-Horsfall protein (13), or it could reflect cross-reactivity with other glycoproteins changes during inflammation (9, 19). According to Sandberg et al. (20), reversible alterations of kidney tubule structure can be caused by fever per se. This can expose Tamm-Horsfall protein to the immune system. The highest values determined in healthy subjects were for IgM, which implicates binding of so called "native antibodies". We reported previously (18) that IgM also showed the highest values in the test with native Tamm-Horsfall protein molecule in patients with acute pyelonephritis. This supports the hypothesis that native TammHorsfall protein is a sequestrated antigen (9, 13, 20) without contact to the immune system. On the other hand, the highest levels of antibodies to Tamm-Horsfall protein subunits determined in patients with acute pyelonephritis were those of IgA. As highest values of antibodies to Tamm-Horsfall protein subunits in healthy persons were shown by IgM, the results obtained in this study suggested that the association of IgA with Tamm-Horsfall protein subunits in the serum of patients with acute pyelonephritis could be the consequence of immune system stimulation with Tamm-Horsfall protein subunits. However, one should also keep in mind the observed cross-reactivity between Tamm-Horsfall protein and some bacterial epitopes (4, 7, 8).

The values of antibodies to Tamm-Horsfall protein measured in healthy subjects are shown in table 1. The values for IgG were significantly lower than values for IgA and IgM antibodies determined in the test with THP-S and THP-A (p < 0.01) and in the test performed with THP-U and THP-G subunits as antigen (p < 0.05).

Values for IgG and IgA in tests with Tamm-Horsfall protein subunits were significantly higher in patients with acute pyelonephritis. They were also higher than values observed in the test with the native molecule (18). This might further confirm the presumption that antibodies to Tamm-Horsfall protein subunits indeed denote

IgG

IgA

IgM

THP-S

0.00a (0-0.03)

0.20 (0.13-0.27)

0.26 (0.17-0.32)

THP-A

0.00a (0-0.09)

0.10 (0.01-0.29)

0.65 (0.18-1.18)

THP-U

0.09b (0-0.31)

0.31 (0.04-0.60)

0.42 (0.21-0.56)

THP-G

0.09b (0.04-0.20)

0.20 (0.09-0.50)

0.88 (0.81-1.40)

Values are expressed as median and range p < 0.01; b p < 0.05 vs. IgA and IgM classes THP-S = subunit obtained by splitting with 0.0017 mol/1 sodiumdodecyl-sulphate THP-A = subunit obtained by splitting with 8.3 mol/1 acetic acid THP-U = subunit obtained by splitting with 0.04 mol/1 urea THP-G = subunit obtained by splitting with 6 mol/1 guanidine hydrochloride a

sions and their means were calculated. The values of antibodies to each Tamm-Horsfall protein subunit were also determined on three occasions and the mean value of the three determinations was calculated. The data thus obtained were statistically processed on a PC using Quickstat and Microstat programs. As the results distribution was unusual for all antibody classes, the significance of the differences was determined by non-parametric methods, i.e. by the Mannlyhitney U test and the Kruskall-Wallis test.

Table 2 presents values for antibodies to Tamm-Horsfall protein determined in patients with acute pyelonephritis. In the test performed with THP-A subunits, values for IgA and IgM were significantly higher (p < 0.01) than the values of these classes and for IgG measured in tests using other subunits as antigens. Table 3 shows the results of tests performed in patients with acute pyelonephritis and vesicoureteral reflux. The values for IgG, IgA and IgM measured in the test with THP-A subunit were higher (p < 0.05; p < 0.01; p < 0.01, respectively) than the values obtained in tests with other subunits. The values for IgG were higher in patients with acute pyelonephritis than in healthy subjects (p < 0.05), irrespective of the presence of vesicoureteral reflux. In patients with vesicoureteral reflux, the values for IgA were significantly higher than in healthy subjects, as measured in tests using THP-S, THP-U and THP-G (p < 0.05) and in the test using THP-A subunit (p < 0.01). In patients without yesicoureteral reflux, differences between patients and healthy subjects were statistically significant when the tests were performed with THP-A, THP-U and THP-G subunits (p < 0.05). The IgM class of antibodies was significantly higher in patients with acute pyelonephritis, of the presence of vesicoureteral reflux, but only when the test was performed with THP-A subnit as antigen (p < 0.05). Values of all three classes were significantly higher in patients with vesicoureteral reflux compared with the values determined in patients with normal radiological findings (p < 0.05).

Tab. 2 Values of antibodies to Tamm-Horsfall protein subunits prepared in vitro, in patients with acute pyelonephritis (N = 21)

IgG

IgA

IgM

THP-S

0.26b (0.17-0.45)

0.38 (0.18-0.45)

THP-A

0.30b (0.20-0.55)

4.12a-c (1.84-5.00)

0.35 (0.15-0.32) 319 a,c (1.76-4.50)

THP-U

0.20b (0.12-0.70)

0.67b (0.56-0.170)

0.32 (0.20-0.64)

THP-G

0.1 9b (0.12-0.54)

0.94b (0.50-0.188)

0.78 (0.51-1.33)

THP-S = subunit obtained by splitting with 0.0017 mol/1 sodiumdodecyl-sulphate THP-A = subunit obtained by splitting with 8.3 mol/1 acetic acid THP-U = subunit obtained by splitting with 0.04 mol/1 urea THP^G = subunit obtained by splitting with 6 mol/1 guanidine hydrochloride a p < 0.01 vs. values measured in tests with THP-S, THP-U and THi>-G, as well as vs. IgG b p < 0.05; c v p < 0.01 vs. healthy subjects '

317

Short communication contact with the immune system. This contact is particularly possible in patients with vesicouretcral reflux, where Tamm-Horsfall protein penetrates by intrarenal reflux into the renal interstitium. Tab. 3 Values of antibodies to Tamm-Horsfall protein subunits prepared in vitro, in patients with acute pyelonephritis and vesicoureteral reflux (N = 4)

IgG

IgA

IgM

0.43C (0.35-0.74)

0.48 (0.27-1.67)

(0.17-1.93)

0.49C (0.43-1.58) 1873 b.d.e (3.37-19.11)

10.81b-c-c (1.25-13.49)

THP-U

0.20C (0.08-1.03)

0.97C (0.48-1.29)

0.48 (0.10-0.250)

THP-G

0.28C (0.33-0.66)

0.99C (0.71-1.57)

0.88 (0.51-1.33)

THP-S THP-A

147 a.c.e

THP-S = subunit obtained by splitting with 0.0017 mol/1 sodiumdodecyl-sulphate THP-A = subunit obtained by splitting with 8.3 mol/1 acetic acid THP-U = subunit obtained by splitting with 0.04 mol/1 urea THP-G = subunit obtained by splitting with 6 mol/1 guanidine hydrochloride a p < 0.05; b p < 0.01 vs. values obtained in tests with THP-S, THP-U and THP-G subunits c p < 0.05; d p < 0.01 vs. healthy subjects e p < 0.05 vs. patients without vesicoureteral reflux

In tine with this statement is the observation that the levels of antibodies to Tamm-Horsfall protein are higher in patients with acute pyelonephritis and vesicoureteral reflux than in patients with acute pyelonephritis and normal radiological findings. Higher values of antibodies to Tamm-Horsfall protein in patients with vesicoureteral reflux have already been reported (15, 16). Marier et al. (14) even proposed determination of antibodies to Tamm-Horsfall protein as a useful test for identifying patients with vesicoureteral reflux. In patients with acute pyelonephritis, the highest values were found when the test was performed with the Tamm-Horsfall protein subunit obtained in vitro by splitting with acetic acid (ΤΗΡΑ). Values measured in this test were significantly higher than those in tests with other subunits, and higher than the values determined in healthy subjects. Patients with acute pyelonephritis and vesicoureteral reflux have significantly higher values of all three classes of antibodies than patients with normal radiological findings. We suppose that splitting with acetic acid could either unmask more immunogenic epitopes or it could uncover epitopes which are cross-reactive with bacterial ones. Although we found differences in the values for antibodies (IgG and IgA classes) to Tamm-Horsfall protein subunits prepared in vitro between patients with acute pyelonephritis and healthy persons, the question of whether antibodies to Tamm-Horsfall protein could be of use in diagnosing acute pyelonephritis, and, probably, vesicoureteral reflux requires further investigation. The higher values for antibodies to Tamm-Horsfall protein subunits compared with those for antibodies to Tamm-Horsfall polymer (18) confirm moreover that the native Tamm-Horsfall protein molecule is not directly related to the immune system. Since changes in the glycosylation of some glycoproteins have been observed during infections (21), antibodies to the Tamm-Horsfall protein monomer subunits isolated from the urine of patients with acute pyelonephritis should also be determined.

References 1. Sheldon C, Gonzales R. Differentiation of upper and lower urinary tract infections: how and when? Med Clin N Am 1984; 68:321-33. 2. Pappas P. Laboratory in diagnosis and management of urinary tract infections. Med Clin N Am 1991; 75:313-32. 3. Sobel J. Bacterial etiologic agents in the pathogenesis of urinary tract infections. Med Clin N Am 1991; 75:253-73. 4. Shachner M, Miniter P, Mayrer A, Andriole V. Interaction of Tamm-Horsfall protein with bacterial extracts. Kidney Int 1987; 31:77-84. 5. Fowler J, Mariano M, Lau J. Interaction of urinary TammHorsfall protein with transitional cells and transitional epithelium. J Urol 1987; 138:446-8. 6. Leasley R, Levison M, Host defense mechanism in pathogenesis of urinary tract infections. Med Clin N Am 1991; 75:275-86. 7. Reinhart H, Obedeanu N, Merzbach D, Sobel J. Effect of Tamm-Horsfall protein in chemoluminiscence response of polymorphonuclear leukocytes to uropathogenic E. coli. J Infect Dis 1991; 164:404-6. 8. Kurijama S, Silverblatt F. Effect of Tamm-Horsfall urinary glycoprotein on phagocytosis and killing of type 1-fimbriated Escherichia coli. Infect Immun 1986; 51:193-8. 9. Kumar L, Mushmore I. Tamm-Horsfall protein-uromodulin (1950-1990). Kidney Int 1990; 37:1395-401. 10. Fasth A, Hanson L, Jodal U. Antibodies to Hamm-Horsfall protein associated with urinary tract infection in girls. J Pediatr 1979; 95:54-60. 11. Hanson L, Fasth A, Jodal U. Autoantibodies to Hamm-Horsfall protein, a tool for diagnosing the level of urinary tract infection. Lancet 1976; 31:226-8. 12. Fasth A, Bengston U, Kaijser B, Wieslander J. Antibodies to Tamm-Horsfall protein associated with renal damage and urinary tract infection in adults. Kidney Int 1981; 20:500-4.

13. Avis P. Autoantibodies to Tamm-Horsfall glycoprotein: an artifact of technique? Contr Nephrol 1984; 39:305-15. 14. Marier R, Fong E, Janse M, Hodson C, Richards F, Andriole C. Antibody to Tamm-Horsfall protein in patients with urinary tract obstruction and vesicoureteral reflux. J Infect Dis 1987; 138:781-9. 15. Lynn K, Bailey R, Groufsky A, Hunt J, Bean A, MyGiven A. Antibodies to the urinary Tamm-Horsfall protein in patients with urinary tract infection, reflux nephropathy, urinary obstruction. Contr Nephrol 1984; 39:296-304. 16. Vasth A, Hanson L, Asscher W. Autoantibodies to TammHorsfall protein in detection of vesicoureteric reflux and kidney scarring. Arch Dis in Child 1977; 52:560-2. 17. Cvoriscec D. Tamm-Horsfall protein i znacenje njegova odredivanja u endemskoj nefropatiji [Dissertation] Zagreb: University of Zagreb, 1988. 18. Benkovic J, Jelakovic B, Cikes N. Antibodies to Tamm-Horsfall protein in patients with acute pyelonephritis. Eur J Clin Chem Clin Biochem 1994; 32:337-40. 19. Hoops T, Rindler M. Isolation of the cDNA encoding glycoprotein-2 (GP-2) in the major zymogen granule membrane protein cross-reactivity. J Biol Chem 1991; 266:4257-63. 20. Sandberg T, Fasth A. Association between fever and the antibody response to Tamm-Horsfall protein in urinary tract infection. Scand J Urol Nephrol 1987; 138:781-9. 21. Turner G. N-glycolysation of serum protein in disease and its investigation using lectins. Clin Chim Acta 1992; 208:14972. Received October 16, 1995/Januaiy 15. 1996 Corresponding author: Bojan Jelakovic, MD, Department of Medicine, University Hospital Center, School of Medicine, University of Zagreb, Kispaticeva 12, HR-10000 Zagreb, Croatia