ABSTRACT. Serum amyloid A (SAA) is one of the major acute phase proteins in cats that has potential to be used as an inflammatory marker. A previous study showed that the human SAA turbidimetric immunoassay (hSAA-TIA) could be used to measure the SAA concentration in cats. The objectives of the present study were to assess use of hSAA-TIA for determining the feline SAA concentration and to evaluate its clinical application. Recombinant feline SAA protein (rfSAA) was expressed in Escherichia coli and purified for SDS-PAGE and immunoblot analysis with anti-human SAA antibodies. The concentration of rfSAA was determined by ELISA and hSAA-TIA. Plasma SAA concentrations were measured in healthy and diseased cats by hSAA-TIA. The time-courses changes in the SAA and α1-acid glycoprotein (AGP) concentrations in the cats after ovariohysterectomy were investigated. In SDS-PAGE, rfSAA was detected as a clear band that reacted with anti-human SAA antibodies. There was significant correlation between the SAA concentration measured by ELISA and hSAA-TIA. The SAA concentration of the diseased cats (n=263) was significantly increased (P<0.01; 0.0-88.9 mg/l, mean: 7.52 mg/l) compared with that in the healthy cats (n=26; 0.0-0.9 mg/l, mean: 0.14 mg/l). No correlation was observed between SAA and WBC in the diseased cats. The SAA concentration changed more rapidly and remarkably than the AGP concentration after ovariohysterectomy. The present study revealed that hSAA-TIA is useful for determination of the feline SAA concentration. Measurement of the SAA concentration, in addition to the WBC count, would be clinically valuable as a routine test to detect inflammation. KEY WORDS: acute phase protein, α1-acid glycoprotein, feline, serum amyloid A, turbidimetric immunoassay.

Canine pancreatitis is a relatively common disorder, and its mortality rate remains high. However, prognostic factors for pancreatitis based on evidence are limited. Moreover, the relationship between changes in C-reactive protein (CRP) concentration—an important prognostic factor for human patients with acute pancreatitis—and the prognosis of dogs with pancreatitis has not been widely studied. Therefore, we examined prognostic factors for canine pancreatitis during the first medical examination and evaluated the usefulness of serial CRP measurements during hospitalization. Sixty-five dogs met the inclusion criteria, including 22 that were hospitalized and treated. In Study 1, a multivariate analysis revealed that three factors— decreased platelet count and a marked (greater than 1,000 µg/l) elevation of specific canine pancreatic lipase (Spec cPL) concentration at the first medical examination, as well as elevated blood urea nitrogen (BUN) and/or creatinine (CRE) level—were significantly different between the survivors and nonsurvivors. Moreover, CRP concentrations on the third and fourth days were significantly different between the two groups in Study 2. An evaluation of the decreased platelet count, remarkable elevation of Spec cPL concentration at the first medical examination, elevation of BUN and/or CRE as well as serial CRP concentration measurements may be useful for predicting the prognosis of canine pancreatitis.

Serum amyloid A (SAA) is reported not only as a marker for the presence of inflammation but also as a prognostic indicator in human beings. In cats, however, there is no report on the association between SAA concentration and prognosis. The objective of the current study was to evaluate SAA concentration as a prognostic marker in diseased cats. A total of 175 cats with neoplastic diseases, inflammatory diseases, and other diseases were retrospectively recruited, and the medical records of these cats, including follow-up data on mortality, were reviewed. Cats were divided into 2 groups according to SAA concentration, and differences in survival between each group were assessed. Median survival time of cats in the elevated SAA (>0.82 mg/l) group was significantly shorter than that in the nonelevated SAA (≤0.82 mg/l) group ( P < 0.001). Furthermore, by multivariate analysis, SAA concentration was shown as a significant and independent prognostic marker in cats with various diseases ( P = 0.015). Serum amyloid A concentration in diseased cats is a useful predictive indicator of prognosis regardless of diagnosis.

Time-course changes in the concentration of serum amyloid A (SAA), a major acute phase protein, were measured in a cat with pancreatitis over an 831-day period and compared with changes in WBC count and feline trypsin-like immunoreactivity (fTLI). SAA concentration was increased at the onset of the disease and gradually decreased over 5 days of treatment with an improvement in the clinical condition. In contrast, fTLI concentration and WBC count were not increased at the onset of the disease but increased gradually during the 5 days of treatment. Long-term monitoring from days 68 to 831 revealed a good correlation between SAA concentration and the reoccurrence of clinical signs in the cat; however, WBC count did not increase even with the exacerbation of disease. These findings suggest that the SAA concentration may be a useful marker for evaluating response to treatment and disease exacerbation in feline pancreatitis.

The serum amyloid A (SAA) concentration is higher in mammary tumors with metastases in both humans and animals. In the present study, the direct effects of recombinant feline SAA (rfSAA) protein on invasiveness of feline mammary carcinoma cells were evaluated. As an indicator of invasiveness, matrix metalloproteinase-9 (MMP-9) expression was investigated in 4 feline mammary carcinoma cell lines of different origins. In 3 of 4 cell lines, MMP-9 expression was significantly increased by rfSAA stimulation. The invasive capacities of feline mammary carcinoma cells were also stimulated by rfSAA. The findings of this study have identified a novel role for SAA in mammary tumorigenesis and suggest that therapeutic strategies targeting SAA may provide new alternatives in treating tumor invasion and metastasis.