A flow cytometric assessment of the lymphocyte immunophenotypes in dogs naturally infected with Babesia rossi

Abstract

Immunity to Babesia infection requires both innate and acquired responses, including both cell mediated- and humoral responses. The aims of this study were to investigate the variation in selected peripheral blood lymphocyte phenotypes in dogs with virulent babesiosis at presentation and over time post treatment, and to determine whether these correlated with the severity of clinical signs. Forty-four dogs naturally infected with Babesia rossi were studied and 5 healthy dogs were included as controls. Babesia-infected dogs were divided into complicated or uncomplicated groups based on clinical signs and in-house laboratory assays. Blood samples were collected from the jugular vein at admission, prior to any treatment, and at 24 hours and 48 - 72 hours. Leukocytes were incubated with canine specific, fluorochrome conjugated anti- cluster of differentiation (CD)3, anti-CD4, anti-CD8, and anti-B cell markers. The percentage CD3+ lymphocytes in the complicated group was significantly lower compared to the controls (P = 0.014) and uncomplicated group (P = 0.007). The percentage CD4+ T lymphocytes in the complicated group was significantly lower compared to the controls (P = 0.027) and uncomplicated group (P = 0.014). Both the complicated and uncomplicated groups expressed a significantly lower percentage CD8+ T lymphocytes compared to the control group (P<0.001 and P = 0.005, respectively). The percentage B lymphocytes was significantly higher in the complicated group at 48 - 72 hours compared to the percentage at presentation. These findings could indicate the presence of a functional immune suppression in dogs with complicated babesiosis, secondary to increased apoptosis or redistribution of effector lymphocytes and/or a combination of other immune modulatory mechanisms induced by B. rossi infection.