Table 1.

Homo sapiens, Mus musculus, and Mus dunni Xpr1 clones function as retrovirus receptors when expressed in CHO cells^a

Xpr1 ortholog	Vector titer for LAPSN pseudotype
	Xenotropic retrovirus (NZB virus)	Polytropic retrovirus (MCF 98D virus)	Amphotropic retrovirus (4070A)
hXpr1	4 × 106	3 × 104	<1
mXpr1	40	5 × 107	<1
mdXpr1	2 × 106	6 × 107	<1
None	30	<1	<1

^aHuman, Mus musculus, and Mus dunni Xpr1 cDNAs were cloned into the LXSN retroviral expression vector, retroviruses were made from the vector plasmids by the transfection of HEK 293 cells with each vector and Moloney MLV gag-pol and VSV-G env genes, and CHO cells were exposed to the viruses and grown in G418 medium to select for the neo gene carried by the LXSN vector. To test for the ability of xenotropic, polytropic, and amphotropic retroviruses to infect CHO cells carrying the different xpr1 genes, the cells were exposed to virus harvested from MDTF cells transduced with the LAPSN vector and the indicated replication-competent xenotropic or polytropic retroviruses or to the LAPSN vector produced by PA317 retrovirus packaging cells that express the 4070A amphotropic retrovirus Env protein. Two days later, the CHO cells were stained for alkaline phosphatase (expressed by the LAPSN vector) to determine the vector titer. Results are means of data from two to four experiments.