The feline acute phase reaction

Degenerative left shift as a prognostic tool in cats

Background

A degenerative left shift (DLS) is reported to be a poor prognostic indicator in dogs and cats. Limited data in dogs and no studies in cats have been published to investigate this claim.

Hypothesis/Objectives

To characterize the feline population affected by DLS and to determine if the presence and severity of DLS are associated with increased risk of euthanasia or death.

Animals

One hundred and eight cats with DLS (cases) and 322 cats without DLS (controls) presented to the University of California, Davis Veterinary Medical Teaching Hospital between April 1, 1995 and April 1, 2010.

Methods

Retrospective case–control study. All cases had a CBC performed within 24 hours of presentation in which immature granulocytic precursors exceeded mature neutrophils. Controls were matched by year of presentation and primary diagnosis. Survival analysis was used to determine risk of death or euthanasia from DLS and other potential predictors of outcome.

Results

Cases were more likely to die or be euthanized in hospital compared to controls (60/108 [56%] versus 107/322 [33%]). DLS was a significant predictor of death or euthanasia in hospitalized cats in both univariate and multivariate analysis (hazard ratio, 1.57; 95% confidence interval, 1.13–2.18). Trend analysis showed an increasing trend in the hazard of euthanasia or death with increasing severity of DLS.

Conclusions and Clinical Importance

Cats with DLS are 1.57 times more likely to die or be euthanized in hospital than cats without DLS. In addition, increasing severity of DLS is associated with increased likelihood of death or euthanasia.

Seasonal trends in nesting leatherback turtle (Dermochelys coriacea) serum proteins further verify capital breeding hypothesis

Serum protein concentrations provide insight into the nutritional and immune status of organisms. It has been suggested that some marine turtles are capital breeders that fast during the nesting season. In this study, we documented serum proteins in neophyte and remigrant nesting leatherback sea turtles (Dermochelys coriacea). This allowed us to establish trends across the nesting season to determine whether these physiological parameters indicate if leatherbacks forage or fast while on nesting grounds. Using the biuret method and agarose gel electrophoresis, total serum protein (median = 5.0 g/dl) and protein fractions were quantified and include pre-albumin (median = 0.0 g/dl), albumin (median = 1.81 g/dl), α1-globulin (median = 0.90 g/dl), α2-globulin (median = 0.74 g/dl), total α-globulin (median = 1.64 g/dl), β-globulin (median = 0.56 g/dl), γ-globulin (median = 0.81 g/dl) and total globulin (median = 3.12 g/dl). The albumin:globulin ratio (median = 0.59) was also calculated. Confidence intervals (90%) were used to establish reference intervals. Total protein, albumin and total globulin concentrations declined in successive nesting events. Protein fractions declined at less significant rates or remained relatively constant during the nesting season. Here, we show that leatherbacks are most likely fasting during the nesting season. A minimal threshold of total serum protein concentrations of around 3.5-4.5 g/dl may physiologically signal the end of the season's nesting for individual leatherbacks. The results presented here lend further insight into the interaction between reproduction, fasting and energy reserves and will potentially improve the conservation and management of this imperiled species.

Monitoring acute phase proteins in retrovirus infected cats undergoing feline interferon-ω therapy

OBJECTIVES

Recombinant feline interferon-ω therapy is an immunomodulator currently used in the treatment of different retroviral diseases including feline immune deficiency virus and feline leukaemia virus. Although its mechanism of action remains unclear, this drug appears to potentiate the innate response. Acute phase proteins are one of the key components of innate immunity and studies describing their use as a monitoring tool for the immune system in animals undergoing interferon-ω therapy are lacking. This study aimed to determine whether interferon-ω therapy influences acute phase protein concentrations namely serum amyloid-A, α-1-glycoprotein and C-reactive protein.

METHODS

A single-arm study was performed using 16 cats, living in an animal shelter, naturally infected with retroviruses and subjected to the interferon-ω therapy licensed protocol. Samples were collected before (D0), during (D10 and D30) and after therapy (D65). Serum amyloid-A and C-reactive protein were measured by specific enzyme-linked immunosorbent assay kits and α-1-glycoprotein by single radial immunodiffusion.

RESULTS

All the acute phase proteins significantly increased in cats undergoing interferon-ω therapy (D0/D65: P<0·05) CLINICAL SIGNIFICANCE: Acute phase proteins appear to be reasonable predictors of innate-immune stimulation and may be useful in the individual monitoring of naturally retroviral infected cats undergoing interferon-ω therapy.

Oral Recombinant Feline Interferon-Omega as an alternative immune modulation therapy in FIV positive cats: clinical and laboratory evaluation

Recombinant-Feline Interferon-Omega (rFeIFN-ω) is an immune-modulator licensed for use subcutaneously in Feline Immunodeficiency virus (FIV) therapy. Despite oral protocols have been suggested, little is known about such use in FIV-infected cats. This study aimed to evaluate the clinical improvement, laboratory findings, concurrent viral excretion and acute phase proteins (APPs) in naturally FIV-infected cats under oral rFeIFN-ω therapy (0.1 MU/cat rFeIFN-ω PO, SID, 90 days). 11 FIV-positive cats were treated with oral rFeIFN-ω (PO Group). Results were compared to previous data from 7 FIV-positive cats treated with the subcutaneous licensed protocol (SC Group). Initial clinical scores were similar in both groups. Independently of the protocol, rFeIFN-ω induced a significant clinical improvement of treated cats. Concurrent viral excretion and APP's variation were not significant in the PO Group. Oral rFeIFN-ω can be an effective alternative therapy for FIV-infected cats, being also an option for treatment follow-up in cats submitted to the licensed protocol.

Haematological and biochemical reference intervals of four feline breeds

Many feline breeds have been generated from a small number of ancestors. Thus, breed-specific peculiarities can be expected, which could include haematological and biochemical measurements. Despite this, there are only a few reports on breed-specific reference intervals (RI). This information is essential in routine practice where results from individual patients are usually compared with an RI. The aim was to compare haematological and biochemical data from clinically healthy Abyssinian, Holy Birman, Norwegian Forest and Siberian cats with published RIs to assess whether the published RIs are acceptable in these breeds. Comparison with established RIs using guidelines from the National Committee for Clinical Laboratory Standards and the American Society of Veterinary Clinical Pathology, revealed a number of breed-related clinicopathological differences. New RIs were established, but in most cases the new RIs overlapped with published RIs, and the use of the breed-specific data would minimally affect the clinical interpretation of laboratory results. Important differences that could result in misinterpretation of laboratory results were as follows: microcytosis and high α2-globulin concentrations in Abyssinian cats; high serum creatinine, α2-globulin and glucose concentrations in Holy Birman cats; high serum alkaline phosphatase activity and calcium and phosphate concentration in Norwegian Forest cats; low β2-globulin and γ-globulin concentrations in Norwegian Forest and Siberian cats. Breed-specific RIs should be used for these analytes. In addition, care should be taken in interpreting clinicopathological data in purebred cats for which specific RIs have not been established.

Hyposialylated α1-acid glycoprotein inhibits phagocytosis of feline neutrophils

Feline α1-acid glycoprotein (fAGP) modifies both its serum concentration and its glycan moiety during diseases. fAGP is hyposialylated in cats with feline infectious peritonitis (FIP), but not in clinically healthy cats or in cats with other diseases. This study was aimed to determine whether hyposialylated fAGP influences phagocytosis. A flow cytometric method based on ingestion of fluoresceinated bacteria and adapted to feline blood was used to assess phagocytosis of leukocytes incubated with 'non-pathological' fAGP (purified from sera with normal concentrations of AGP) and 'pathological' fAGP (purified from sera with >1.5mg/mL hyposialylated AGP). The flow cytometric method provided repeatable results for neutrophils (coefficients of variations, CVs <15%) but not for monocytes (CVs>20%) which had also a high individual variability. Compared with saline solution and with non-pathological fAGP, pathological fAGP significantly decreased phagocytosis in neutrophils and monocytes. This study demonstrated that hyposialylated fAGP down-regulates the phagocytic activity of feline neutrophils.

Role of acute phase proteins in the immune response of rabbits infected with Trypanosoma evansi

The aim of this study was to characterize the response of acute phase proteins (APP) in rabbits experimentally infected with Trypanosoma evansi (T. evansi), and to relate the findings with serum immunoglobulins levels, in order to verify the relation between APP and the immune response of rabbits. A total of 12 animals were used in this experiment and divided into 2 groups, control and infected, of six rabbits each. The experimental period was 118 days, and blood was collected on days 0, 5, 20, 35, 65, 95 and 118 post-infection (PI). The infection with T. evansi stimulated APP and immunoglobulins production, once the infected animals showed an increase in C-reactive protein, haptoglobin, alpha 2-macroglobulin and IgM levels. The elevation in IgM levels observed in this study, when related to the increase in C-reactive protein and haptoglobin levels, suggests the involvement of these proteins in host defense against flagellated protozoa, with possible participation in the control of the parasitemia in rabbits infected with T. evansi.

Flow cytometric detection of alpha-1-acid glycoprotein on feline circulating leucocytes

OBJECTIVE

To assess whether alpha-1-acid glycoprotein (AGP) can be detected on the membrane of feline circulating leucocytes.

DESIGN

The presence of AGP on circulating leucocytes was investigated in both clinically healthy cats and cats with different diseases. A group of feline coronavirus (FCoV)-positive cats, comprising cats with feline infectious peritonitis (FIP) and cats not affected by FIP but seropositive for FCoV, were included in this study because the serum concentration of AGP increases during FCoV infection.

PROCEDURE

Flow cytometry (using an anti-feline AGP antibody), serum protein electrophoresis, routine haematology and measurement of the serum AGP concentration were performed using blood samples from 32 healthy cats (19 FCoV-seropositive), 13 cats with FIP and 12 with other diseases (6 FCoV-seropositive). The proportion of cats with AGP-positive leucocytes in the different groups (e.g. controls vs sick; FIP vs other diseases, etc.) or in cats with different intensities of inflammatory response was compared using a Chi-square test.

RESULTS

AGP-positive leucocytes were found in 23% of cats. Compared with controls, the proportion of patients with positive granulocytes and monocytes was higher among sick cats (especially cats with diseases other than FIP) and cats with high serum AGP concentration, but not in cats with leucocytosis or that were FCoV-seropositive.

CONCLUSION

AGP-positive leucocytes can be found in feline blood, especially during inflammation. Conversely, no association between AGP-positive leucocytes and FIP was found. Further studies are needed to elucidate the mechanism responsible for this finding and its diagnostic role in cats with inflammation.

Acute phase proteins in animals

Acute phase proteins (APP) were first identified in the early 1900s as early reactants to infectious disease. They are now understood to be an integral part of the acute phase response (APR) which is the cornerstone of innate immunity. APP have been shown to be valuable biomarkers as increases can occur with inflammation, infection, neoplasia, stress, and trauma. All animals--from fish to mammals--have demonstrable APP, but the type of major APP differs by species. While the primary application of these proteins in a clinical setting is prognostication, studies in animals have demonstrated relevance to diagnosis and detection and monitoring for subclinical disease. APP have been well documented in laboratory, companion, and large animals. With the advent of standardized and automated assays, these biomarkers are available for use in all fields of veterinary medicine as well as basic and clinical research.

Acute phase proteins in healthy and sick cats

Serum acute phase protein concentrations are used as diagnostic, therapeutic and prognostic markers in human and, less frequently, in animal medicine. The aim of this study was to determine how the health status and signalment of the cat are associated with concentrations of acute phase proteins. Generally, medians of the positive acute phase proteins appeared to be higher in sick cats compared to healthy cats. In multivariable regression models, log-transformed serum amyloid A concentration was higher in older cats, in sick and in female cats, while log-transformed α1-acid glycoprotein and haptoglobin concentrations were higher in older cats and were associated with interactions of health status (sick/healthy) and gender (male/female). The data from healthy cats in this study contribute to the limited knowledge of normal reference ranges for this species. This study highlights the potential of acute phase proteins as diagnostic markers in sick cats, but also emphasises that the signalment of the cat needs to be taken into consideration.

Shedding of chlamydiae in relation to titers of serum chlamydiae-specific antibodies and serum concentrations of two acute-phase proteins in cats without conjunctivitis

OBJECTIVE

To investigate shedding of chlamydiae from conjunctiva and genital tracts of cats without clinical signs of conjunctivitis or other infectious disease in relation to their titers of serum antibodies against chlamydiae and to serum amyloid A (SAA) and serum α(1)-acid glycoprotein (AGP) concentrations.

ANIMALS

62 healthy cats.

PROCEDURES

Serum from each cat was analyzed for antibodies against chlamydiae and for SAA and AGP concentrations. Swab samples from the conjunctival sac and genital tract were analyzed with a real-time PCR assay for Chlamydiaceae.

RESULTS

4 of 8 of cats with high antibody titers (ie, 1,600) shed chlamydiae, but only from the conjunctiva. Chlamydiae could not be detected in samples from cats with lower antibody titers nor from any genital tract samples. In cats with antibody titers of 1,600, mean ± SD SAA concentration was significantly higher when chlamydiae were detected in conjunctival swab samples (3.9 ± 1.0 mg/L) than when no chlamydiae were detected (1.4 ± 1.0 mg/L). However, SAA concentration was greater than the limit for an acute-phase response in only one of those cats. There was no significant difference in serum AGP concentrations between cats with high titers that were or were not shedding chlamydiae. Nine of 30 (30%) cats (5 with and 4 without detectable serum antibodies against chlamydiae) that had been mated developed reproductive disorders.

CONCLUSIONS AND CLINICAL RELEVANCE

Clinically normal cats with high chlamydiae-specific antibody titers can shed and thus transmit chlamydiae. Venereal spread from cats without clinical signs of infection is likely not common.

Performances of different diagnostic tests for feline infectious peritonitis in challenging clinical cases

Objectives: Feline infectious peritonitis (FIP) can be difficult to diagnose. Histopathology is considered the gold standard test but immunohistochemistry (IHC) is mandatory to confirm/exclude the disease. This study aimed to assess the performances of tests carried out in vivo or at postmortem examination in challenging cases in which FIP was confirmed or excluded based on IHC or on adequate follow‐up.

Methods: Twelve cases (four without FIP, eight with FIP) were retrospectively studied. Clinical findings, serum protein electrophoresis (SPE), analysis of the effusions (AE), antifeline coronavirus serology, serum concentration of α1‐acid glycoprotein (AGP) and histopathology were classified as consistent, doubtful or non‐consistent with FIP. Sensitivity, specificity and concordance (κ) with the final diagnosis were calculated.

Results: Concordance was absent for serology (κ=−0·08) and AE (κ=−0·52), poor for histopathology (κ=0·09), fair for SPE (κ=0·25) and perfect for AGP (κ=1·00). Sensitivity was high for AGP (100%) and low for AE (50%), SPE (37·5%) and histopathology (37·5%). Specificity was high for AGP or histopathology (100%) and low for SPE (50%) and AE (0%).

Clinical Significance: IHC must always be performed to confirm FIP. If this is not possible, when histopathology is controversial, elevated AGP concentrations may support the diagnosis of FIP.

Acute phase response in Chinese soft-shelled turtle (Trionyx sinensis) with Aeromonas hydrophila infection

Chinese soft-shelled turtle (Trionyx sinensis) is an important culture reptile. However, little is known about its acute phase response (APR) caused by bacteria. Serum amyloid A (SAA) is a major acute phase protein (APP). In this study, a turtle SAA homologue was identified and described in reptiles. The full-length cDNA of turtle SAA was 554 bp and contained a 381 bp open reading frame (ORF) coding for a protein of 127 aa. Similar to other known SAA genes, the turtle SAA gene contained three exons and two introns. The promoter region of turtle SAA gene contained the consensus binding sites for nuclear factor (NF)-κB and c-Rel. The turtle SAA amino acid sequence shared the highest identity to avian SAA sequences. Meantime, we present the first systematic study with expression levels of five genes encoding APPs in immune response caused by Aeromonas hydrophila infection. After infection, turtle SAA mRNA was induced in liver at 8h, then increased more than 1200-fold at 2d; in spleen and kidney, the SAA mRNAs were also induced during 8h-7d, but the level was far lower than that in the liver. The complement 3 (C3), fibrinogen-gamma chain (Fb-G) and cathepsin L (CathL) mRNAs were increased in liver at 2d, whereas the albumin (ALB) mRNA was significantly decreased during 8h-7d. Our studies suggest that the APR in turtle with A. hydrophila infection is similar to that in mammals, and SAA is a major indicator of bacterial infection, especially at early stage, in reptiles. Additionally, the different expression patterns of five APP genes observed in present studies could provide clues for understanding the innate immune mechanisms in the APR of reptiles.

Assay validation and diagnostic applications of major acute-phase protein testing in companion animals

The use of major acute-phase proteins (APPs) for assessment of health and disease in companion animals has increased within the last decade because of increased knowledge in the field and increased access to appropriate assay systems for detection of relevant APPs, which are highly species specific. Despite evidence being restricted almost solely to proven excellent overlap performance of these markers in detecting inflammatory activity, clinically relevant studies at higher evidence levels do exist. The available body of literature shows a clear, but seemingly untapped, potential for more extended routine clinical use of major APP testing in companion animal medicine.

Leucogram and serum acute phase protein concentrations in queens submitted to conventional or videolaparoscopic ovariectomy

Thirty health queens were submitted to ovariectomy by conventional technique or by videolaparoscopy. In order to study the intensity of inflammatory response by means of acute phase protein analysis and white blood cell count, serum samples were taken before and until 144 hours after the surgical procedures. The protein concentrations that were significantly increased 24 hours after surgical procedures were: ceruloplasmin, hemopexin, haptoglobin, and α1-acid glycoprotein, 69.8%, 103.5%, 117.3%, and 199.0%, respectively, for conventional ovariectomy; and 22.3%, 46.1%, 79.8%, and 74.6%, respectively, for laparoscopic ovariectomy. Therefore, inflammatory response was more intense in queens submitted to conventional ovariectomy. Results indicate that the increase or decrease in acute phase proteins, as well as in white blood cells count, may be useful in the evaluation of inflammatory response induced by these surgical procedures.

Acute phase response in animals: a review

The acute phase response is a complex systemic early-defense system activated by trauma, infection, stress, neoplasia, and inflammation. Although nonspecific, it serves as a core of the innate immune response involving physical and molecular barriers and responses that serve to prevent infection, clear potential pathogens, initiate inflammatory processes, and contribute to resolution and the healing process. Acute phase proteins, an integral part of the acute phase response, have been a focus of many applications in human diagnostic medicine and recently have been identified in common animal species. Potential applications to diagnosis, prognosis, assessment of animal health, and laboratory animal welfare are readily apparent.

Neutrophil survival factors (TNF-alpha, GM-CSF, and G-CSF) produced by macrophages in cats infected with feline infectious peritonitis virus contribute to the pathogenesis of granulomatous lesions

Feline infectious peritonitis (FIP) is a feline coronavirus (FCoV)-induced fatal disease of domestic and wild cats. The infiltration of neutrophils into granulomatous lesions is unusual for a viral disease, but it is a typical finding of FIP. This study aimed to investigate the reason for the lesions containing neutrophils in cats with FIP. Neutrophils of cats with FIP were cultured, and changes in the cell survival rate were assessed. In addition, the presence or absence of neutrophil survival factors was investigated in specimens collected from cats with FIP. Furthermore, it was investigated whether macrophages, one of the target cells of FIPV infection, produce neutrophil survival factors (TNF-alpha, GM-CSF, and G-CSF). We showed that virus-infected macrophages overproduce neutrophil survival factors, and these factors act on neutrophils and up-regulate their survival. These observations suggest that sustained production of neutrophil survival factors by macrophages during FCoV infection is sufficient for neutrophil survival and contributes to development of granulomatous lesions.

Neuroimmune regulation in immunocompetence, acute illness, and healing

Adaptive immunocompetence is maintained by growth hormone (GH), prolactin (PRL), and vasopressin (VP). Innate or natural immunocompetence depends on cytokines, hormones (especially of the hypothalamus-pituitary-adrenal axis), and catecholamines. The acute phase response (APR, or acute febrile illness) is an emergency defense reaction whereby the adaptive, T cell-dependent, immune reactions are suppressed and the innate immune function is dramatically amplified. Infection and various forms of injury induce APR. Cytokines [interleukin (IL)-1beta, tumor necrosis factor-alpha, and IL-6] stimulate corticotropin-releasing hormone (CRH) and VP secretion and cause a "sympathetic outflow." Colony-stimulating factors activate leukocytes. CRH is a powerful activator of the pituitary adrenocortical axis and elevates glucocorticoid (GC) levels. Cytokines, GCs, and catecholamines play fundamental roles in the amplification of natural immune defense mechanisms. VP supports the APR at this stage. However, VP remains active and is elevated for a longer period than is CRH. VP, but not CRH, is elevated during chronic inflammatory diseases. VP controls adaptive immune function and stimulates adrenocorticotropic hormone (ACTH) and PRL secretion. PRL maintains the function of the thymus and of the T cell-dependent adaptive immune system. The ACTH-adrenal axis stimulates natural immunity and of suppressor/regulatory T cells, which suppress the adaptive immune system. VP also has a direct effect on lymphoid cells, the significance of which remains to be elucidated. It is suggested that VP regulates the process of recovery from acute illness.

Association between faecal shedding of feline coronavirus and serum alpha1-acid glycoprotein sialylation

The sialylation pattern of serum alpha1-acid glycoprotein (AGP) in non-symptomatic cats infected by feline coronavirus (FCoV) and its possible relationship with the amount of FCoVs shed in faeces were investigated. Blood from three specific pathogen-free cats (group A) and from 10 non-symptomatic FCoV-positive cats from catteries with low (group B, three cats) or high (group C, seven cats) levels of faecal shedding were collected monthly. AGP was purified from serum and Western blotting followed by lectin-staining of alpha(2,3)-linked and alpha(2,6)-linked sialic acid. Faecal shedding was quantified in group C by quantitative polymerase chain reaction. Variations of AGP sialylation were recorded only in cats from group C, on which viral shedding peaked before the occurrence of feline infectious peritonitis (FIP) in the cattery, and decreased 1 month later, when serum AGP had an increase of alpha(2,3)-linked sialic acid. These results suggest that hypersialylation of AGP may be involved in host-virus interactions.