Passive immunization does not provide protection against experimental infection with Mycoplasma haemofelis

Abstract

Mycoplasma haemofelis (Mhf) is the most pathogenic feline hemotropic mycoplasma. Cats infected with Mhf that clear bacteremia are protected from Mhf reinfection, but the mechanisms of protective immunity are unresolved. In the present study we investigated whether the passive transfer of antibodies from Mhf-recovered cats to naïve recipient cats provided protection against bacteremia and clinical disease following homologous challenge with Mhf; moreover, we characterized the immune response in the recipient cats. Ten specified pathogen-free (SPF) cats were transfused with pooled plasma from cats that had cleared Mhf bacteremia; five control cats received plasma from naïve SPF cats. After homologous challenge with Mhf, cats were monitored for 100 days using quantitative PCR, hematology, blood biochemistry, Coombs testing, flow cytometry, DnaK ELISA, and red blood cell (RBC) osmotic fragility (OF) measurement. Passively immunized cats were not protected against Mhf infection but, compared to control cats, showed significantly higher RBC OF and B lymphocyte (CD45R/B220+) counts and occasionally higher lymphocyte, monocyte and activated CD4+ T lymphocyte (CD4+CD25+) counts; they also showed higher bilirubin, total protein and globulin levels compared to those of control cats. At times of peak bacteremia, a decrease in eosinophils and lymphocytes, as well as subsets thereof (B lymphocytes and CD5+, CD4+ and CD8+ T lymphocytes), and an increase in monocytes were particularly significant in the passively immunized cats. In conclusion, passive immunization does not prevent bacteremia and clinical disease following homologous challenge with Mhf, but enhances RBC osmotic fragility and induces a pronounced immune response.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0361-x) contains supplementary material, which is available to authorized users.

Evaluation of endothelial glycocalyx injury biomarkers in feline hemotropic mycoplasmosis

“…Hyperbilirubinemia is associated with severe hemolytic anemia and liver damage in cats with feline hemotropic mycoplasmosis 1 , 34 . It has been reported that during severe erythrocyte destruction, the capacity of the liver to metabolize bilirubin is exceeded and hyperbilirubinemia develops 35 . In the present study, the increased total and direct bilirubin concentrations in cats with feline hemotropic mycoplasmosis were interpreted as excessive bilirubin production due to intravascular and extravascular hemolysis and exceeding hepatic bilirubin clearance capacity 35 .…”

“…It has been reported that during severe erythrocyte destruction, the capacity of the liver to metabolize bilirubin is exceeded and hyperbilirubinemia develops 35 . In the present study, the increased total and direct bilirubin concentrations in cats with feline hemotropic mycoplasmosis were interpreted as excessive bilirubin production due to intravascular and extravascular hemolysis and exceeding hepatic bilirubin clearance capacity 35 . In addition, the high AST and LDH enzyme activities determined in cats with hemotropic mycoplasmosis may be related to hemolysis, and the high phosphorus levels may be related to the release of excessive amounts of phosphorus from erythrocytes as a result of intravascular hemolysis 25 .…”