Buehring G C, Kramme P M, Schultz R D
School of Public Health, University of California, Berkeley.
Lab Invest. 1994 Sep;71(3):359-65.
Bovine leukemia virus (BLV), a retrovirus, usually causes a subclinical infection of dairy and beef cattle, but in < 1% of infected cattle a B cell lymphoma may develop after several years of infection. BLV is transmitted horizontally among cattle, and infected animals have anti-BLV titers. Expression of BLV antigen, however, is silent in peripheral blood lymphocytes in vivo. The tropism of BLV has been assumed to be limited to B lymphocytes, because no other cell type has been found to harbor the virus in vivo. Since retrovirus-like particles had been identified in milk, and infection can be transmitted by milk, we decided to investigate whether BLV was in mammary epithelial cells.
Pure cultures of mammary epithelial cells were established from cells shed into the milk of 28 cows. BLV was searched in these cultures by immunocytochemistry and the polymerase chain reaction, the specificity of the latter confirmed by Southern blot hybridization and DNA sequencing. BLV was searched immunocytochemically in mammary tissue sections from 12 cows.
Antigenic and/or molecular evidence of BLV was found in the cultured cells of 20 cows. Antigenic evidence of BLV was found in tissue sections from 10 cows, indicating virus expression in vivo. Simultaneous detection of BLV p24 and cytokeratins, localized antigen expression to the mammary epithelial cells.
These indications of BLV in mammary epithelial cells in vivo suggest that BLV is capable of infecting and expressing antigen in glandular epithelium in vivo and has a broader tissue tropism than was previously thought. They raise the question of how persistent mammary infection by BLV may influence the course of bovine lymphoma, and what effect the virus may have on the mammary gland.
牛白血病病毒（BLV）是一种逆转录病毒，通常引起奶牛和肉牛的亚临床感染，但在不到1%的受感染牛中，感染数年之后可能会发展为B细胞淋巴瘤。BLV在牛群中通过水平传播，受感染动物具有抗BLV滴度。然而，BLV抗原在体内外周血淋巴细胞中不表达。由于BLV的嗜性一直被认为仅限于B淋巴细胞，因为尚未发现其他细胞类型在体内携带该病毒。自从在牛奶中鉴定出逆转录病毒样颗粒，并且感染可通过牛奶传播以来，我们决定研究BLV是否存在于乳腺上皮细胞中。
从28头奶牛乳汁中脱落的细胞建立乳腺上皮细胞纯培养物。通过免疫细胞化学和聚合酶链反应在这些培养物中检测BLV，后者的特异性通过Southern印迹杂交和DNA测序得到证实。在12头奶牛的乳腺组织切片中进行免疫细胞化学检测以寻找BLV。
在20头奶牛的培养细胞中发现了BLV的抗原和/或分子证据。在10头奶牛的组织切片中发现了BLV的抗原证据，表明病毒在体内表达。同时检测BLV p24和细胞角蛋白，将抗原表达定位到乳腺上皮细胞。
体内乳腺上皮细胞中存在BLV的这些迹象表明，BLV能够在体内腺上皮中感染并表达抗原，并且其组织嗜性比以前认为的更广。它们提出了以下问题：BLV持续的乳腺感染如何影响牛淋巴瘤的病程，以及该病毒可能对乳腺有什么影响。
