Effect of Prototheca zopfii on neutrophil function from bovine milk

This study was carried to investigate neutrophil function in the presence of Prototheca zopfii. For this purpose, bovine milk neutrophils were incubated in the absence (control) of and presence of P. zopfii, and then they were examined hydrogen peroxide (H₂O₂) production, antioxidant enzyme activities, and phagocytic capacity. Milk was collected from negative “California Mastitis Test” (CMT) quarter from three lactating Holstein cows after induction of leukocytosis with an intramammary infusion of oyster glycogen. H₂O₂ production was measured using the phenol red method. Catalase activity was measured following H₂O₂ reduction at 240 nm and the activity of glutathione reductase was determined by measuring the rate of NADPH oxidation at 340 nm. P. zopfii death was assessed by fluorescent microscopy using acridine orange assay and by colony forming units (CFUs). Comparisons between the groups were initially performed by analysis of variance (ANOVA). Significant differences were then compared using Tukey’s test with a significance coefficient of 0.05. Hydrogen peroxide production, catalase and glutathione reductase activities by neutrophils incubated in presence of P. zopfii were stimulated five times, 21% and 27% respectively, compared to the unstimulated-neutrophils. Neutrophils did not affect P. zopfii death as shown by microscopy and CFUs. These observations led to the conclusion that the P. zopfii promote a high increase of H₂O₂ production by neutrophils from bovine milk during algae exposition accompanied by increase of antioxidant enzyme activities; however, this process did not affect P. zopfii death.