Arch Virol (1999) 144: 1191–1200
IFNγ inhibits porcine reproductive and respiratory syndrome
virus replication in macrophages
E. M. Bautista
and T. W. Molitor
Department of Clinical and Population Sciences, College of Veterinary Medicine,
University of Minnesota, St. Paul, Minnesota, U.S.A.
Accepted February 15, 1999
Summary. This study reports the effect of IFN␥ on the replication of porcine
reproductive and respiratory syndrome virus (PRRSV) in macrophages. Pretreat-
ment with IFN␥ profoundly affected PRRSV replication in porcine macrophages
evaluated by reduction in titer and percentage of positive cells. The effect of IFN␥
on PRRSV replication was both dose-dependent and related to the time of ex-
posure. The mechanism of action was not due to blocking virus attachment. The
inhibitory effect on PRRSV replication in macrophages suggests that IFN␥ may
play an important role in protection.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a member of the
newly designated family Arteriviridae  within the order Nidovirales . This
viruscausesreproductivefailureinpregnantsows and respiratory disease in young
pigs[8, 9, 37, 47]. Alveolarmacrophagesappearto be the predominant susceptible
cells for PRRSV replication as evidenced by detection in situ of PRRSV antigens
or viral RNA in vivo [18, 36, 38, 41], and in vitro [3, 29, 47, 49]. Blood monocytes
have been shown to support PRRSV replication in vitro although in a much lesser
extent than in alveolar macrophages [30, 46].
Mature tissue macrophages are derived from blood monocytes, which in turn
have developed from the stem cell in the bone marrow [15, 42, 44]. Macrophages
have important physiological functions and play a central role in cell-mediated
immune responses both as effector cells and as antigen presenting cells. The
Present address: Eli Lilly & Co., Greenﬁeld, IN, U.S.A.