Effects of bovine leukemia virus infection on milk neutrophil function and the milk lymphocyte profile

Abstract

The effects of bovine leukemia virus (BLV) on the immune response have been extensively investigated; however, its effects on mammary gland immunity are only speculative. Although BLV has a tropism for B cells, it can affect both adaptive and innate immunities because these systems share many effector mechanisms. This scenario is the basis of this investigation of the effects of BLV on mammary gland immunity, which is largely dependent upon neutrophilic functions. Thus, the present study sought to examine neutrophilic functions and the lymphocyte profile in the milk of naturally BLV-infected cows. The viability of the milk neutrophils and the percentage of milk neutrophils that produced reactive oxygen species (ROS) or phagocytosed Staphylococcus aureus were similar between BLV-infected and BLV-uninfected dairy cows. Furthermore, the expression of CD62L and CD11b by the milk neutrophils and the percentage of milk neutrophils (CH138+ cells) that were obtained from the udder quarters of the BLV-infected cows were not altered. Conversely, the median fluorescence intensity (MFI) representing intracellular ROS production and the phagocytosis of S. aureus, the expression of CD44 by the milk neutrophils and the percentage of apoptotic B cells were lower in the milk cells from BLV-infected dairy cows, particularly those from animals with persistent lymphocytosis (PL). The lymphocyte subsets were not different among the groups, with the exception of the percentage of CD5−/CD11b− B cells, which was higher in the milk cells from BLV-infected cows, particularly those with PL. Thus, the present study provides novel insight into the implications of BLV infection for mammary gland immunity.

CHANGES IN LEUKOCYTE AND ERYTHROCYTE BLOOD PROFILE AND PARAMETERS UNDER A COMBINED Anaplasma marginale AND BOVINE LEUKEMIA VIRUS INFECTION IN CATTLE

“…The most distinguishing feature of BLV infection, even at low leukocytosis, is the disappearance of the normally correlated links between the counts of different populations of leukocytes, indicating the destruction of the network relationships between them. Importantly, in animals with high leukocytosis, marked neutrophilopenia is observed, which coincides with the literature data on the change in the neutrophil content in milk at BLV infection and high leukocytosis [11]. Given the need for a simpler method for identifying the most infectious animals in industrial herds, it seems appropriate to simultaneously evaluate the viral load (the amount of BLV RNA in the peripheral blood) and the severity of leukocytosis.…”

“…When the pathogen is phagocytized, neutrophils produce free radicals that destroy it. It was found that in milk of cows infected with BLV, neutrophils are significantly reduced [11], while for individuals with leukocytosis and high load of BLV proviral DNA a reduced expression of -interferon (IFN-) by peripheral blood monocytes is characteristic. IFN-γ promotes phagocytosis and production of free radicals by neutrophils, which can, in particular, explain the decrease in neutrophil function along with the decrease in their number in BLV infected cows.…”

“…The combination of all three methods is most effective and allows increasing the reliability of detection of infected cows [1]. However, it should be taken into account that the BLV infection in animals is often accompanied by an increase in the sensitivity to bacterial infectious agents, such as Mycobacterium bovis [9], to Escherichia coli [10], and by an increase in mastitis [11], which may, in turn, lead to changes in the number of peripheral blood leukocytes. Anaplasmosis in cattle caused by Anaplasma marginale (Rikskettsiales: Anaplasmatacea) is another reason of significant economic losses in livestock [12][13][14].…”

Quercetin Promotes the Expression of Genes Involved in Phagocytosis in Bovine Neutrophils

“…The phagocytosis of PI labeled E. coli was assessed via flow cytometry (Della Libera et al, 2015). In brief, neutrophils (2×10 5 neutrophils) were seeded into duplicate wells of a 96-well, flat bottom cell culture plate.…”

Stable infection of a bovine mammary epithelial cell line (MAC-T) with bovine leukemia virus (BLV)

“…BLV infection negatively impacts on dairy production by diminishing the milk yield and increasing deaths and veterinary costs. Moreover, it has been described that BLV infection might lead to a higher susceptibility to other infections due to its effects on immune cells (Della Libera et al, 2015;Emanuelson et al, 1992;Erskine et al, 2011;Frie and Coussens, 2015). In this way, BLV could be related to an increased incidence of mastitis, one of the most common diseases in dairy cattle.…”