APOBEC3 proteins expressed
in mammary epithelial cells are packaged into retroviruses
and can restrict transmission of milk-borne virions
Okeoma CM, Huegel AL, Lingappa J, Feldman MD, Ross SR.
Cell Host Microbe 8:534-43, 2010
Viruses, including retroviruses like human immunodeficiency
virus (HIV) and mouse mammary tumor virus (MMTV), are transmitted
from mother to infants through milk. Lymphoid cells and antibodies
are thought to provide mammary gland and milk-borne immunity.
In contrast, little is known about the role of mammary epithelial
cells (MECs). The APOBEC3 family of retroviral restriction
factors is highly expressed in macrophages and lymphoid and
dendritic cells. We now show that APOBEC3 proteins are also
expressed in mouse and human MECs. Lymphoid cell-expressed
APOBEC3 restricts in vivo spread of MMTV to lymphoid and
mammary tissue. In contrast, mammary gland-expressed APOBEC3
is packaged into MMTV virions and decreases the infectivity
of milk-borne viruses. Moreover, APOBEC3G and other APOBEC3
genes are expressed in human mammary cells and have the potential
to restrict viruses produced in this cell type. These data
point to a role for APOBEC3 proteins in limiting infectivity
of milk-transmitted viruses.