Changes in serum amyloid A (SAA), Haptoglobin (Hp) and immunoglobulin concentration in feline infectious peritonitis (FIP) affected cats and in FIP-exposed cats

CHANGES IN SERUM AMYLOID A (SAA), HAPTOGLOBIN (HP) AND IMMUNOGLOBULINS CONCENTRATION IN FELINE INFECTIOUS PERITONITIS (FIP) AFFECTED CATS AND IN FIP-EXPOSED CATS Alessia Giordano, Saverio Paltrinieri, Alessia Colombo, Stefano Comazzi Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Facoltà di Medicina Veterinaria, Università degli Studi di Milano, Via Celoria 10, Milano, Italy The present study was designed in order to identify the proteins responsible of the increase of the 2 and -globulins during FIP and to investigate any possible difference between serum protein profiles of FIP-affected (FA) and FIP-exposed (FE) cats. The study group was composed by 24 controls, 32 cats with FIP (FA), confirmed by post-mortem examinations, and 11 healthy cats (FE) coming from three catteries with high prevalence of FIP. Blood serum was used to perform an electrophoresis on cellulose acetate strips and to detect Serum Amyloid A (SAA) and haptoglobin (Hp), using specific ELISA kits, and IgG and IgM, using immunoradial diffusion kits. All these tests were repeated during the development of the disease in two FA cats and monthly in the group of FE cats. Both FA and FE cats showed higher 2 and -globulins than controls. FA cats had the highest values of SAA and Hp while these proteins were higher in FE cats than controls. IgG and IgM were higher in FA cats than controls. However, the total amounts of 2-, -, and -globulins were higher than those SAA+Hp, IgM and IgG, respectively. Repeated samplings suggest that SAA increases during the development of the disease until a plateau, while 2-globulins and Hp increase at the beginning of the disease, then decrease. In contrast FE cats had a strong but transient increase of SAA just after the onset of FIP and an increase of 2-globulins lasting for more than two months. These results confirm the presence of changes in protein fractions and in some specific proteins during FIP: SAA and Hp contribute to the increase of 2-gobulins, and IgM and IgG to the increase of - and -globulins, respectively. Other proteins with 2 and  motility are involved in the pathogenesis of FIP. Both FA and FE cats show an acute phase response: 2-globulins decrease in FA cats, in part due to a decrease of Hp, but increase in FE cats, most likely due to proteins other than those here investigated. The identification of these proteins may help to understand the mechanisms by which some cats do not develop FIP and to early diagnose the carriers of the virus among FE cats.