Hyposialylated α1-acid glycoprotein inhibits phagocytosis of feline neutrophils

Abstract

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.

An Acute-phase Protein as a Regulator of Sperm Survival in the Bovine Oviduct: Alpha 1-acid-glycoprotein Impairs Neutrophil Phagocytosis of Sperm <i>In Vitro</i>

“…In fact, our results show that desialylating AGP completely abolished the AGP-suppressive effect on both PMN phagocytosis of sperm and superoxide release. These results are in agreement with previous studies showing that desialylating AGP abolished an AGP hepato-protective effect [ 38 ] and anti-apoptotic activity [ 39 ], whereas hyposialylated AGP completely inhibited the phagocytosis of E. coli by feline neutrophils [ 40 ].…”

Relationship between rate of infection and markers of inflammation/immunity in Holy Birman cats with feline coronavirus

“…However, this hypothesis may not be proven since the temporal association between FCoV fecal shedding and the presence of high AGP values was not assessed in this study. Unfortunately, it was not possible to assess whether these changes were associated with peculiarities of the glycosylation pattern of AGP, as demonstrated in previous studies (Ceciliani et al, 2004;Paltrinieri et al, 2007), since the procedure of AGP purification and of assessment of the glycosylation pattern requires high volumes of serum (Ceciliani et al, 2004;Rossi et al, 2013).…”

“…As further support of the protective role of immunity, FIP occurs frequently in young and old cats, that have a less efficient immune system (Pedersen, 2009). Moreover, the comparison of results from FCoV-infected, clinically healthy cats and from cats with FIP showed some differences regarding indicators of innate or cell-mediated immunity, such as lymphocyte subsets, that decrease in blood and lymph nodes in FIP cats but not in FCoV-positive cats (Kipar et al, 1999(Kipar et al, , 2001Paltrinieri et al, 2003), α1-acid glycoprotein (AGP), that increases and is hyposialylated in FIP cats (Ceciliani et al, 2004;Duthie et al, 1997), possibly depressing neutrophil functions (Rossi et al, 2013) and transiently increases and is hypersialylated in FCoV-positive cats Paltrinieri et al, 2007), and proinflammatory cytokines or interferon-γ (IFN-γ) whose expression and serum concentration decreases in FIP cats and increases in FCoV-positive cats (Gelain et al, 2006;Giordano and Paltrinieri, 2009;Gunn-Moore et al, 1998;Kiss et al, 2004).…”

Changes in Serum and Urine SAA Concentrations and Qualitative and Quantitative Proteinuria in Abyssinian Cats with Familial Amyloidosis: A Five‐year Longitudinal Study (2009–2014)

“…Serum then was aliquoted and frozen at −20°C for a maximum of 6 months to measure SAA. In the case of high SAA, the acute phase protein α 1 ‐acid glycoprotein (AGP) was measured on stored sera using a radial immunodiffusion method as previously described …”