Inhibition of IL-2R and SLA class II expression on stimulated lymphocytes by a suppressor activity found in homogenates of African swine fever virus infected cultures

Abstract

Virus free supernatants (VFS) obtained by ultracentrifugation of homogenates of African swine fever (ASF) virus infected cultures inhibited the proliferative response and the expression in peripheral blood mononuclear cells of two activation molecules, the IL-2 receptor (IL-2R) and the swine MHC class II antigens (SLA II), induced by several stimuli (lectins, PMA plus the calcium ionophore A23187 or specific antigen). This inhibition was time dependent: no effect was seen on IL-2R expression when VFS was added after 48 h, when the expression of this molecule reached its maximum. However at this time the proliferative response was still inhibited. The presence of VFS in the cultures was necessary to inhibit both the IL-2R expression and the proliferation of cells. In these conditions the addition of exogenous IL-2 to the cultures failed to restore the IL-2R expression and the proliferation shown by control stimulated cells. Furthermore, the IL-2 activity found in supernatants from cell cultures stimulated with Con A in the presence of VFS was even higher than in cultures stimulated without VFS. The inhibition observed suggests an important impairment of host immunocompetence in ASF infected swine.

Deletion of a CD2-Like Gene,8-DR, from African Swine Fever Virus Affects Viral Infection in Domestic Swine

“…Significant inhibition of lectin-dependent lymphocyte proliferation in PBMC cultures infected with ASFV or those incubated in the presence of virus-free infected cell extracts has been previously described (5,6,18,61). While the nature of the responsible inhibitory factor(s) is unknown, it appears to be a soluble protein with a molecular mass estimated to be between 40 and 80 kDa (6,18). Notably, a soluble hemagglutinin, made up of 51-kDa monomers, has been identified in the medium of cultures infected with some ASFV isolates (49).…”

Apoptosis: a Mechanism of Cell Killing and Lymphoid Organ Impairment During Acute African Swine Fever Virus Infection

“…ASFV infects cells of the mononuclear phagocytic system in vitro (Casal eta]., 1984) and in vivo (Ramiro-Ib~ifiez eta]., 1995), interfering with immune responses mediated by macrophages, and macrophage functions such as phagocytic activity (Martins et al, 1988). It has been described that after in vitro infection, there is modulation of SLA-I and -II molecules, as well as other surface markers with central roles in the immune response (Canals et at., 1995 ;Gonzalez-Juarrero et aL, I992;Ramiro-Ib~fiez, 1995). On the other hand, ASFV-induced immunosuppression has been demonstrated by the inability of lymphocytes to proliferate in response to mitogenic lectins (Gonzalez et al, 1990;Wardley, 1982).…”