Amyloid-related serum protein (SAA) as an indicator of lung infection in cystic fibrosis

Oh my gut! Is the microbial origin of neurodegenerative diseases real?

There is no cure or effective treatment for neurodegenerative protein conformational diseases (PCDs), such as Alzheimer's or Parkinson's diseases, mainly because the etiology of these diseases remains elusive. Recent data suggest that unique changes in the gut microbial composition are associated with these ailments; however, our current understanding of the bacterial role in the pathogenesis of PCDs is hindered by the complexity of the microbial communities associated with specific microbiomes, such as the gut, oral, or vaginal microbiota. The composition of these specific microbiomes is regarded as a unique fingerprint affected by factors such as infections, diet, lifestyle, and antibiotics. All of these factors also affect the severity of neurodegenerative diseases. The majority of studies that reveal microbial contribution are correlational, and various models, including worm, fly, and mouse, are being utilized to decipher the role of individual microbes that may affect disease onset and progression. Recent evidence from across model organisms and humans shows a positive correlation between the presence of gram-negative enteropathogenic bacteria and the pathogenesis of PCDs. While these correlational studies do not provide a mechanistic explanation, they do reveal contributing bacterial species and provide an important basis for further investigation. One of the lurking concerns related to the microbial contribution to PCDs is the increasing prevalence of antibiotic resistance and poor antibiotic stewardship, which ultimately select for proteotoxic bacteria, especially the gram-negative species that are known for intrinsic resistance. In this review, we summarize what is known about individual microbial contribution to PCDs and the potential impact of increasing antimicrobial resistance.

Infection-Mediated Clinical Biomarkers for a COVID-19 Electrical Biosensing Platform

The race towards the development of user-friendly, portable, fast-detection, and low-cost devices for healthcare systems has become the focus of effective screening efforts since the pandemic attack in December 2019, which is known as the coronavirus disease 2019 (COVID-19) pandemic. Currently existing techniques such as RT-PCR, antigen-antibody-based detection, and CT scans are prompt solutions for diagnosing infected patients. However, the limitations of currently available indicators have enticed researchers to search for adjunct or additional solutions for COVID-19 diagnosis. Meanwhile, identifying biomarkers or indicators is necessary for understanding the severity of the disease and aids in developing efficient drugs and vaccines. Therefore, clinical studies on infected patients revealed that infection-mediated clinical biomarkers, especially pro-inflammatory cytokines and acute phase proteins, are highly associated with COVID-19. These biomarkers are undermined or overlooked in the context of diagnosis and prognosis evaluation of infected patients. Hence, this review discusses the potential implementation of these biomarkers for COVID-19 electrical biosensing platforms. The secretion range for each biomarker is reviewed based on clinical studies. Currently available electrical biosensors comprising electrochemical and electronic biosensors associated with these biomarkers are discussed, and insights into the use of infection-mediated clinical biomarkers as prognostic and adjunct diagnostic indicators in developing an electrical-based COVID-19 biosensor are provided.

Amyloidosis in cystic fibrosis

As the life expectancy of patients with cystic fibrosis has increased, greater attention has been paid towards the diagnosis and management of the longer term consequences of the condition. A recognised but rare complication of the disease is the development of secondary amyloidosis. Whilst deposition of amyloid protein has been reported in a high proportion of patients with cystic fibrosis at post-mortem [1] and Serum Amyloid A protein has been shown to correlate with disease activity and response to antibiotics [2], the manifestation of clinical disease remains extremely uncommon. The prognosis for patients with amyloid secondary to cystic fibrosis in published reports has been historically bleak [3-6], however there may be novel approaches in the era of biological therapies. The theoretical potential for an increase in the incidence of secondary amyloid amongst the population of cystic fibrosis patients who are experiencing much longer lifespans means that it is worthwhile to consider the condition and its possible treatments in more detail. We report a case and a review of the literature.

Acute phase reactant serum amyloid A in inflammation and other diseases

Acute-phase reactant serum amyloid A (A-SAA) plays an important role in acute and chronic inflammation and is used in clinical laboratories as an indicator of inflammation. Although both A-SAA and C-reactive protein (CRP) are acute-phase proteins, the detection of A-SAA is more conclusive than the detection of CRP in patients with viral infections, severe acute pancreatitis, and rejection reactions to kidney transplants. A-SAA has greater clinical diagnostic value in patients who are immunosuppressed, patients with cystic fibrosis who are treated with corticoids, and preterm infants with late-onset sepsis. Nevertheless, for the assessment of the inflammation status and identification of viral infection in other pathologies, such as bacterial infections, the combinatorial use of A-SAA and other acute-phase proteins (APPs), such as CRP and procalcitonin (PCT), can provide more information and sensitivity than the use of any of these proteins alone, and the information generated is important in guiding antibiotic therapy. In addition, A-SAA-associated diseases and the diagnostic value of A-SAA are discussed. However, the relationship between different A-SAA isotypes and their human diseases are mostly derived from research laboratories with limited clinical samples. Thus, further clinical evaluations are necessary to confirm the clinical significance of each A-SAA isotype. Furthermore, the currently available A-SAA assays are based on polyclonal antibodies, which lack isotype specificity and are associated with many inflammatory diseases. Therefore, these assays are usually used in combination with other biomarkers in the clinic.

Immunonutrition in patients with cyctic fibrosis leads to drop of serum amyloid A and increase of oxidative stress

The aim of the present study is to evaluate of the impact of immunonutrition on parameters of oxidative stress and inflammation in patients with cystic fibrosis and malnutrition. In the 30 patients with cystic fibrosis and long-term enteral nutrition support for malnutrition the effect of standard and immunonutrion sipping on oxidative stress and inflammatory activity parameters was compared. Malonyldialdehyde (MDA) as parameter of oxidative stress and serum amyloid A (SAA), interleukin 1 and 6, hsCRP, IgM, IgA, IgG as parameters of inflammatory activity were examined. Immunonutrition decreased SAA to 17.6 mg/L comparing to 25.6 mg/L when standard nutrition was given (p = 0.014). MDA was 0.66 µM on standard and 0.96 µM on immunonutrition support (p<0.01). The significant negative correlation was recorded between MDA and SAA, hs-CRP, interleukin 6, IgA and IgG. In conclusion, the application of immunonutrition in patients with cystic fibrosis and malnutrition is associated with drop of SAA but with the rise of MDA.

Recombinant expression of Epinephelus lanceolatus serum amyloid A (ElSAA) and analysis of its macrophage modulatory activities

Serum amyloid A (SAA) is an acute-phase protein that plays a crucial role in the inflammatory response. In this study, we identified an SAA homolog from Epinephelus lanceolatus (ElSAA). Molecular characterization revealed that ElSAA contains a fibronectin-like motif that is typical of SAAs. Recombinant ElSAA protein (rElSAA) was produced in E. coli BL21 (DE3) cells and purified as a soluble protein. To analyze its biological activity, mouse Raw264.7 macrophage cells were treated with various concentrations of rElSAA. Expression of several inflammation-related cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, and IL-10, was induced by rElSAA. This protein also triggered macrophage differentiation, as evidenced by increases in cell size and complexity. To determine whether rElSAA regulates macrophage polarization, we assessed gene expression of M1 and M2 markers. The results demonstrated that rElSAA induced the expression of both M1 and M2 markers, suggesting that it promotes the differentiation of macrophages into a mixed M1/M2 phenotype. To evaluate whether rElSAA enhances phagocytosis via an opsonization-dependent mechanism, GFP-labeled E. coli cells were pretreated with rElSAA, followed by incubation with Raw264.7 cells. Flow cytometry was used to monitor the phagocytic uptake of GFP-labeled E. coli by macrophages. Surprisingly, incubating E. coli with rElSAA did not enhance bacterial uptake by macrophages. However, preincubating Raw264.7 cells with various concentrations of rElSAA, followed by infection with E. coli (multiplicity of infection = 20 or 40), resulted in a clear enhancement of macrophage phagocytic capacity. In conclusion, we have identified SAA from E. lanceolatus and have demonstrated that rElSAA promotes inflammatory cytokine production and macrophage differentiation. In addition, rElSAA enhances phagocytosis of bacteria by macrophages via an opsonization-independent mechanism.

Effect of azithromycin on systemic markers of inflammation in patients with cystic fibrosis uninfected with Pseudomonas aeruginosa

BACKGROUND

While the mechanism of action by which azithromycin exerts positive effects inpatients with cystic fibrosis remains unclear, evidence suggests that azithromycin may act as an immunomodulatory agent. We examined changes in systemic inflammatory markers in a doubleblind, randomized, controlled trial of oral azithromycin in patients 6-18 years of age with cystic fibrosis who were uninfected with Pseudomonas aeruginosa.

METHODS

WBC counts and differential, serum myeloperoxidase (MPO), high-sensitivity C reactive protein (hsCRP), intracellular adhesion molecule 1, IL-6, calprotectin, serum amyloid A (SAA),and granulocyte colony-stimulating factor (G-CSF) were measured at baseline and after 28 and 168 days of treatment in patients receiving either oral azithromycin or placebo.

RESULTS

Inflammatory markers were similar in both groups at baseline. HsCRP, MPO, SAA, calprotectin,and the absolute neutrophil count (ANC) significantly decreased from baseline today 28 in the azithromycin group compared with the placebo group ( P < .05). This treatment effect was sustained at day 168 for ANC, calprotectin, and SAA ( P < .05). Changes in hsCRP, calprotectin,and SAA at day 28 were negatively correlated with changes in FEV 1 (L) and FEV 1(% predicted), as well as both absolute and relative changes in weight ( P < .05). Except for weight (%),the associations remained significant for calprotectin; FEV 1 (L) and weight (%) remained significantly correlated with the 168-day change in hsCRP. The 168-day change in ANC was significantly correlated with changes in lung function, but not in weight; the change in G-CSF was significantly correlated with the change in weight (%) only.

CONCLUSIONS

In patients not infected with P aeruginosa , oral azithromycin significantly reduced neutrophil counts and serum inflammatory markers within 28 days of initiating treatment.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00431964; URL: www.clinicaltrials.gov

Serum amyloid A protein in acute myocardial infarction

Tissue injury including myocardial infarction leads to a variety of changes in plasma proteins commonly referred to as "the acute phase response". In this report the concentrations of serum amyloid A protein (SAA) were measured serially in 6 patients with myocardial infarction and 4 with angina. SAA was found to be increased in all patients with infarction, but in no patients with angina. Significantly increased SAA levels were detected 12 hours after the peak level of creatine kinase, and the concentrations of SAA seemed to correlate to the amount of damaged tissue. The SAA-response was both faster and more extensive than the response of C-reactive protein (CRP), but the correlation between SAA and CRP was very good.

Amyloidosis in cystic fibrosis: A case series

As the life expectancy of patients with cystic fibrosis increases, unusual complications including amyloidosis are increasingly recognised. We report three cases of amyloidosis including a unique case presenting with a hemorrhagic and thrombotic diatheisis. This complication of amyloidosis has never been reported in cystic fibrosis.

Serum amyloid A (SAA) protein and high-sensitivity C-reactive protein (hsCRP) in healthy newborn infants and healthy young through elderly adults

AIM

To determine the levels of serum amyloid A (SAA) protein and high-sensitivity C-reactive protein (hsCRP) in different age groups.

METHODS

Serum samples from 70 healthy newborn infants, 80 blood donors and 81 healthy elderly individuals were analysed using a nephelometric method. The 231 samples were grouped as follows: 35 umbilical cords, 35 newborns, 48 young adults, 28 middle-aged adults, and 85 elderly adults.

RESULTS

Serum levels of both SAA and hsCRP were lower in umbilical cords than in the newborns and young, middle-aged and elderly adults (p<0.0001). The SAA and hsCRP levels were comparable in newborns, and young and middle-age adults, but higher in elderly adults (p<0.0001-0.03). SAA (r2=0.159, p<0.0001) and hsCRP (r2=0.059, p<0.0001) were positively correlated with age and to each other (r2=0.385, p<0.0001).

CONCLUSION

Serum levels of SAA and hsCRP in umbilical cord blood are close to the detection limit and lower than in the other age groups investigated. The elderly have generally higher levels than the younger age groups, which require higher decision levels in inflammatory diseases, including infections. In newborns and young and middle-aged adults, the lower decision levels of 10 mg/l for SAA and 5 mg/l for CRP are suggested.

Serum amyloid A (SAA): a concise review of biology, assay methods and clinical usefulness

Serum amyloid A (SAA) is a family of proteins encoded in a multigene complex. Acute phase isotypes SAA1 and SAA2 are synthesized in response to inflammatory cytokines. SAA and C-reactive protein (CRP) are now the most sensitive indicators for assessing inflammatory activity. In viral infection and kidney allograft rejection, SAA proved more useful than CRP. Development of convenient assay methods for SAA will facilitate its use in clinical laboratories.

[Secondary kidney amyloidosis and mucoviscidosis]

BACKGROUND

Due to the improvement in cystic fibrosis management, life expectancy has risen; on the other hand, longer survival has led to new complications, including secondary renal amyloidosis, which has been so far very uncommonly reported.

CASE REPORTS

Secondary nephropathic amyloidosis was seen in two 25-year and 22-year-old adults with cystic fibrosis. Both had developed recurrent pulmonary infections due to Pseudomonas aeruginosa over several years. One patient died after 2 years of progressive kidney failure.

CONCLUSION

Severe renal insufficiency due to secondary amyloidosis may complicate the course of cystic fibrosis and become the main prognosis factor in adults.

Serum amyloid A: an acute phase apolipoprotein and precursor of AA amyloid

Serum amyloid A is an acute phase protein complexed to HDL as an apoprotein. The molecular weight is 11.4-12.5 kDa in different species and the protein has from 104 to 112 amino acids, without or with an insertion of eight amino acids at position 72. The protein is very well conserved throughout evolution, indicating an important biological function. The N-terminal part of the molecule is hydrophobic and probably responsible for the lipid binding properties. The most conserved part is from position 38 to 52 and this part is therefore believed to be responsible for the until now unknown biological function. The protein is coded on chromosome 11p in man, and chromosome 7 in mice, and found in all mammals until now investigated, and also in the Peking duck. In the rat a truncated SAA mRNA has been demonstrated, but no equivalent serum protein has been reported. Acute phase SAA is first of all produced in hepatocytes after induction by cytokines, but extrahepatic expression of both acute phase and constitutive SAA proteins have been demonstrated. Several cytokines, first of all IL-1, IL-6 and TNF are involved in the induction of SAA synthesis, but the mutual importance of these cytokines seems to be cell-type specific and to vary in various experimental settings. The role of corticosteroids in SAA induction is somewhat confusing. In most in vitro studies corticosteroids show an enhancing or synergistic effect with cytokines on SAA production in cultured cell. However, in clinical studies and in vivo studies in animals an inhibitory effect of corticosteroids is evident, probably due to the all over anti-inflammatory effect of the drug. Until now no drug has been found that selectively inhibits SAA production by hepatocytes. Effective anti-inflammatory or antibacterial treatment is the only tool for reducing SAA concentration in serum and reducing the risk of developing secondary amyloidosis. The function of SAA is still unclear. Interesting theories, based on current knowledge of the lipid binding properties of the protein and the relation to macrophages, in the transportation of cholesterol from damaged tissues has been advanced. A putative role in cholesterol metabolism is supported by the findings of SAA as an inhibitor of LCAT. The potential that SAA is a modifying protein in inflammation influencing the function of neutrophils and platelets is interesting and more directly related to the inflammatory process itself.(ABSTRACT TRUNCATED AT 400 WORDS)

Preparation of anti-canine serum amyloid A (SAA) serum and purification of SAA from canine high-density lipoprotein

Antiserum to canine serum amyloid A (SAA) was prepared in rabbits by immunization with crude SAA which was prepared from high-density lipoprotein 3 (HDL3) obtained from canine acute-phase serum. The antiserum was absorbed for contaminating antibodies by affinity chromatography using Sepharose 4B coupled with normal canine serum proteins. The rabbit anti-canine SAA serum reacted with a protein and formed a single precipitin line at the position of the alpha 1-region of the immunoelectrophoresis of canine acute-phase serum but did not react with the normal canine serum on immunoelectrophoresis. The antibody to canine SAA was also confirmed by Western blotting analysis. Canine SAA was purified as a low molecular weight protein component from crude SAA by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) after gel filtration chromatography. Purified canine SAA had a molecular weight of 15,000 as estimated by SDS-PAGE. This SAA level was found by enzyme-linked immunosorbent assay (ELISA) to increase 1 day after inoculation with Bordetella bronchiseptica to 9.0-20.1 times the preinoculation value.

Clinical relevance of serum amyloid A protein monitoring in urinary tract infections

We have evaluated the clinical relevance of monitoring acute phase proteins in severe urinary tract infection. Body temperature, white blood cell count, erythrocyte sedimentation rate, serum amyloid A protein (SAA), C-reactive protein (CRP), alpha-1-antichymotrypsin (ACT) and alpha-1-acid glycoprotein (AGP) were determined daily in sera from 18 treated patients. Two patterns of response could be identified: responders and non-responders whose therapy had to be changed. Mean values for each acute phase protein were calculated daily in both responders and non-responders. Statistical evaluation of the significance between the means for each protein was also performed on a daily basis and showed P < 0.01 for SAA and CRP on day 3, for ACT on day 5, and for AGP on day 6. SAA and CRP appear to be the most reliable markers for antimicrobial therapy monitoring in patients with urinary tract infections.

Serum amyloid A protein in acute viral infections

Concentrations of serum amyloid A protein (SAA) were measured in 254 children with viral diseases, including measles, varicella, rubella, mumps, echo-30 meningitis, chronic hepatitis B and C, and in eight with Kawasaki disease. Latex agglutination nephelometric immunoassay was used for assaying SAA. In 191 out of 195 patients (98%), SAA concentrations became markedly raised in the acute phase of the viral disease: measles (97%), varicella (100%), mumps (95%), and echo-30 meningitis (99%) with mean titres of 82.4, 80.5, 60.2, 75.2, and 101.1 micrograms/ml respectively. This increase in SAA was followed by a rapid return to normal concentrations (< 5 micrograms/ml) during convalescence. Remarkably higher concentrations of SAA (mean 1630 micrograms/ml) were detected in the acute phase of patients with Kawasaki disease, but in most of the children with chronic hepatitis B or C, the titres of SAA remained normal. There was no close correlation between SAA and serum concentrations for alpha 1-acid glycoprotein, beta 2-microglobulin, transferrin, and IgG. There was a clear correlation between SAA and C reactive protein concentrations, although SAA showed a greater incremental change than C reactive protein in the acute phase. In the acute phase of these viral diseases, 56% of the patients had raised SAA concentrations (> or = 5 micrograms/ml) with normal C reactive protein concentrations (< 5 micrograms/ml). These results indicate that SAA could be useful as an inflammatory marker in children with acute viral infections.

Production of serum amyloid A and C-reactive protein by HepG2 cells stimulated with combinations of cytokines or monocyte conditioned media: the effects of prednisolone

The hepatic production of the acute phase proteins in response to inflammatory cytokines, and the interaction of corticosteroids within this response, has been the subject of considerable recent research. In this study we have examined the effects of the corticosteroid prednisolone on the production of IL-1 alpha and IL-1 beta by lipopolysaccharide (LPS)-stimulated monocytes, and the ability of the monocyte conditioned media (MOCM) obtained under these conditions to induce human hepatoma HepG2 cells to produce serum amyloid A (SAA) and C-reactive protein (CRP). We also examined the production of SAA and CRP by HepG2 cells exposed to different combinations and concentrations of recombinant human (rh) IL-1 alpha, rhIL-1 beta, rhIL-6, recombinant human tumour necrosis factor-alpha (rhTNF-alpha) and prednisolone. The findings indicate: (i) prednisolone substantially inhibits the production of both IL-1 alpha and IL-1 beta by LPS-stimulated monocytes. The MOCM from prednisolone-treated monocytes induced less SAA and CRP production by HepG2 cells; (ii) IL-1 alpha and IL-1 beta both induced CRP and SAA synthesis by HepG2 cells, but only in the presence of IL-6. IL-1 beta was the more potent inducer for SAA production, but for CRP production IL-1 alpha and IL-1 beta were equivalent; (iii) prednisolone enhances the production of SAA by HepG2 cells, but does not enhance the production of CRP; (iv) TNF-alpha in the presence or absence of IL-6 and/or prednisolone did not induce the production of SAA or CRP by HepG2 cells. These findings offer a tenable solution to a disparate production of SAA compared with CRP in corticosteroid-treated cystic fibrosis (CF) patients.

Comparison of serum amyloid A and C-reactive protein as indicators of lung inflammation in corticosteroid treated and non-corticosteroid treated cystic fibrosis patients

Serum amyloid A (SAA) and C-reactive protein (CRP) levels were compared in 830 serum samples from 155 cystic fibrosis (CF) patients. Correlation coefficients were calculated for all samples (r = 0.73), for samples from non-corticosteroid treated (CFNS) patients (n = 698, r = 0.80), and for samples from corticosteroid treated (CFS) patients (n = 132, r = 0.35). SAA was the more sensitive indicator of pulmonary inflammation when SAA and CRP were compared to pulmonary function tests of 49 hospitalized patients at admission and discharge. CRP levels were significantly (p less than .05) lower at admission in CFS patients than in CFNS patients, whereas SAA levels were not significantly different between the two groups. All nine CFS patients hospitalized had elevated SAA levels (average 22 times above normal limits) at admission, while only six had elevated CRP levels (average 3.7 times above normal limits) at admission. In the 40 CFNS patients both SAA and CRP levels were significantly elevated at admission. In each case SAA and CRP levels declined as pulmonary functions improved with effective antimicrobial therapy. In three instances SAA levels increased during hospitalization while CRP levels did not. In each case, rising SAA levels indicated clinical deterioration associated with evolving resistance of P. aeruginosa which required a change in antibiotic therapy.

A monoclonal antibody sandwich immunoassay for serum amyloid A (SAA) protein

An antibody sandwich immunoassay using two purified rat monoclonal antibodies to human serum amyloid A was developed and used to measure serum amyloid A in human serum. The assay was specific, sensitive, reproducible, and reliable and does not require denaturation of the specimen prior to assay. Serum amyloid A purified by hydrophobic interaction chromatography of acute phase human serum afforded a reliable standard for the assay. A significant (r = 0.69) correlation for SAA and C reactive protein values was found for 180 patient samples analyzed.

Comparative study of C reactive protein and serum amyloid A protein in experimental inflammation

The responses of C reactive protein, measured by radial immunodiffusion and radioimmunoassay, and serum amyloid A protein, measured by radial immunodiffusion, were compared in eight subjects with inflammation induced experimentally by intradermal injection of monosodium urate crystals. A significant increase in serum amyloid A was noted after a lag phase of eight hours, the increase in median concentration at 48 hours being about eightfold. A parallel but less marked increase was found in C reactive protein when measured by radioimmunoassay (fourfold increase in median concentration at 48 hours) after a small but significant decrease during the lag phase. The changes in C reactive protein remained within the reference range and were not detectable by radial immunodiffusion.

Use of ethanol-eluted hydrophobic interaction chromatography in the purification of serum amyloid A

A two-step procedure for the purification of the acute-phase reactant serum amyloid A from serum is described. A hydrophobic interaction chromatography medium, octyl-Sepharose CL4B, eluted with increasing concentrations of EtOH was used as the first step in the purification. The concentrate from this step was applied to a gel filtration column of Sephacryl S-200 and eluted with 10% formic acid. The overall recovery of purified serum amyloid A from serum was 56%. This represents the first time that serum amyloid A has been purified without the use of high concentrations of guanidine or urea. The method presented could easily be scaled up to allow the purification of large quantities of serum amyloid A or readily adapted to the purification of other serum apolipoproteins.

Properties of four acute phase proteins: C-reactive protein, serum amyloid A protein, alpha 1-acid glycoprotein, and fibrinogen

Four plasma proteins, referred to as positive acute phase proteins because of increases in concentration following inflammatory stimuli, are reviewed: C-reactive protein (CRP), serum amyloid A protein (SAA), alpha 1-acid glycoprotein (AAG), and fibrinogen. The CRP and SAA may increase in concentration as much as 1000-fold, the AAG and fibrinogen approximately twofold to fourfold. All are synthesized mainly in the liver, but each may be produced in a number of extrahepatic sites. The role of cytokines in induction of the acute phase proteins is discussed, particularly the multiple functional capabilities of interleukin-6 (IL-6). Other cytokines that regulate acute phase gene expression and protein synthesis include IL-1, tumor necrosis factor alpha, interferon gamma, as well as other stimulatory factors and cofactors. The physicochemical characteristics of each protein are reviewed together with the molecular biology. For each protein, the known biological effects are detailed. The following functions for CRP have been described: reaction with cell surface receptors resulting in opsonization, enhanced phagocytosis, and passive protection; activation of the classical complement pathway; scavenger for chromatin fragments; inhibition of growth and/or metastases of tumor cells; modulation of polymorphonuclear function; and a few additional diverse activities. The role of plasma SAA is described as a precursor of protein AA in secondary amyloidosis; other functions are speculative. AAG may play an immunoregulatory role as well as a role in binding a number of diverse drugs. In addition to clot formation, new data are described for binding of fibrinogen and fibrin to complement receptor type 3. Finally, the concentration of each protein is discussed in a wide variety of noninfectious and infectious disease states, particularly in connective tissue diseases. The quantification of the proteins during the course of various acute and chronic inflammatory disorders is useful in diagnosis, therapy, and in some cases, prognosis.

Serum amyloid protein A (SAA): an indicator of inflammation in AIDS and AIDS-related complex (ARC)

The acute phase protein serum amyloid A (SAA) and C-reactive protein (CRP) were measured in a group of 30 homo- and bisexual males with AIDS, 31 males with AIDS-related complex (ARC) and 23 healthy male homosexual controls (HC) in Copenhagen. The mean values of SAA and CRP were significantly higher in the AIDS group compared to the two other groups. SAA was elevated also in the ARC group, whereas the mean CRP value was normal. No increase in SAA and CRP was found in the HC group. The AIDS patients with Pneumocystis carinii infections had the highest SAA values, those with Kaposi's sarcoma the lowest. The elevations in SAA and CRP preceded episodes of acute opportunistic infections often by several days before the infectious agents were identified. We conclude that patients with AIDS are able to establish an acute phase response as reflected by elevated SAA and CRP, and that measurement of these proteins may be of diagnostic and prognostic value.

Acute phase response of serum amyloid A protein and C reactive protein to the common cold and influenza

C reactive protein (CRP) and serum amyloid A protein (SAA) are sensitive and rapid acute phase reactants, and their measurement for monitoring inflammatory disease and assessing the prognosis in secondary amyloidosis is gaining widespread acceptance. The changes in these proteins in eight subjects suffering from natural colds, 15 subjects with experimentally induced colds (rhinoviruses E1, 3, 9, 14, or 31), and eight with experimentally induced influenza (A/Eng/40/83) were studied. SAA concentration increased in 21 of the 23 subjects with natural or experimental rhinovirus colds (mean increase 95 mg/l); CRP concentration increased in 11 (mean increase 11 mg/l). All subjects with influenza showed pronounced increases in SAA concentrations (mean increase 642 mg/l) while six showed increases in CRP concentration (mean increase 22 mg/l). All these increases were highly significant (p less than 0.001). Asymptomatic excretors of both rhinovirus and influenza virus showed significant increases in SAA concentration (p = 0.015 for rhinovirus and p less than 0.001 for influenza virus) but not in CRP concentration. No changes in SAA or CRP values were seen in 12 volunteers after challenge with saline. These observations suggest that caution is required in the interpretation of estimations of SAA concentration and that it may be too sensitive an acute phase protein for clinical use as its concentration may be raised in both trivial and asymptomatic viral infections.

Amyloid-related serum protein (SAA) during and after pregnancy in healthy women and women with rheumatic disease

The usefulness of amyloid-related serum protein (SAA) as an indicator of disease activity has been evaluated in 11 patients with rheumatoid arthritis (RA), 2 patients with psoriatic arthritis (PA) and 13 patients with ankylosing spondylitis (AS) prospectively studied during and after pregnancy. For comparison, SAA levels were recorded serially during and after pregnancy in 28 healthy pregnant women. SAA levels were unaltered by gestation and thus within the normal range during normal pregnancy, but were raised in healthy pregnant women with episodes of intercurrent infections. In RA and AS patients, SAA concentrations correlated to disease activity during and after pregnancy. Serial levels of SAA and C-reactive protein in healthy women and patients paralleled each other with the most pronounced inflammatory response displayed by SAA. We conclude that SAA is a sensitive and reliable indicator of inflammatory events both in the pregnant and non-pregnant state.