Effect of BLV Infection on the Immune Function of Polymorphonuclear Neutrophil in Dairy Cows.

Guanxin Lv,Hai Wang,Jianfa Wang,Rui Wu,Shuai Lian

doi:10.3389/fvets.2021.737608

Abstract

Enzootic bovine leukemia is a late-onset, neoplastic infection caused by the bovine leukemia virus (BLV). BLV infection hinders the function of the immune system and induces other diseases, which negatively affects the performance and health of the infected cows. As the first line of defense against invading foreign pathogenic microorganisms, polymorphonuclear neutrophil (PMN) plays a vital role in the immune system of dairy cows. However, research on the effect of BLV infection on the immune function of PMN in dairy cows is scarce. Therefore, this experiment aimed to elucidate the effects and effect mechanisms of BLV infection on the immune function of PMN in dairy cows with different BLV provirus loads by detecting the chemotaxis, migration, adhesion, phagocytosis, respiratory burst function, and the formation of NETs. The experimental results showed that BLV infection had no significant effect on the phagocytosis of PMN but inhibited their migration and respiratory burst function, and the effects were closely related to the BLV provirus load. Under high BLV provirus load, PMN produced large amounts of NETs, chemokine CXCL7, adhesion molecule CD18, and pro-inflammatory factors IL-8 and TNF-α, triggering inflammatory responses, and tissue damage. The results of this study will help reveal the reason why BLV infection causes the high incidence of mammary gland inflammation in dairy cows.

Highlights

Bovine leukemia virus (BLV), a virus of the Retroviridae family, Deltaretrovirus genus, is closely related to human T-lymphocyte leukemia virus 1 and 2 (HTLV-1, HTLV-2)
The test animals were divided into the healthy group, the L-proviral load (PVL) group, and the high PVL (H-PVL) group based on the results above, with 5 cows in each group for subsequent experiments
The results showed that the PVL in the L-PLV group did not change significantly, while the PVL of H-PVL group were increased to varying degrees

Summary

Introduction

Bovine leukemia virus (BLV), a virus of the Retroviridae family, Deltaretrovirus genus, is closely related to human T-lymphocyte leukemia virus 1 and 2 (HTLV-1, HTLV-2). BLV causes Enzootic Bovine Leukemia (EBL), a disease that has caused widespread epidemics and substantial economic losses to dairy farming worldwide since first discovered in 1871 [1]. 21 countries worldwide have eradicated BLV, most of which are located in Western Europe [2, 3]. BLV mainly infects peripheral blood lymphocytes and monocytes, leading to diminished immune system function, increased susceptibility to multiple infections, and increased disease severity, affecting milk production, milk quality, and cow culling rates [5, 6]

Methods

Results

Conclusion