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

Abstract

An African swine fever virus (ASFV) gene with similarity to the T-lymphocyte surface antigen CD2 has been found in the pathogenic African isolate Malawi Lil-20/1 (open reading frame [ORF] 8-DR) and a cell culture-adapted European virus, BA71V (ORF EP402R) and has been shown to be responsible for the hemadsorption phenomenon observed for ASFV-infected cells. The structural and functional similarities of the ASFV gene product to CD2, a cellular protein involved in cell-cell adhesion and T-cell-mediated immune responses, suggested a possible role for this gene in tissue tropism and/or immune evasion in the swine host. In this study, we constructed an ASFV 8-DR gene deletion mutant (Δ8-DR) and its revertant (8-DR.R) from the Malawi Lil-20/1 isolate to examine gene function in vivo. In vitro, Δ8-DR, 8-DR.R, and the parental virus exhibited indistinguishable growth characteristics on primary porcine macrophage cell cultures. In vivo,8-DR had no obvious effect on viral virulence in domestic pigs; disease onset, disease course, and mortality were similar for the mutant Δ8-DR, its revertant 8-DR.R, and the parental virus. Altered viral infection was, however, observed for pigs infected with Δ8-DR. A delay in spread to and/or replication of Δ8-DR in the draining lymph node, a delay in generalization of infection, and a 100- to 1,000-fold reduction in virus titers in lymphoid tissue and bone marrow were observed. Onset of viremia for Δ8-DR-infected animals was significantly delayed (by 2 to 5 days), and mean viremia titers were reduced approximately 10,000-fold at 5 days postinfection and 30- to 100-fold at later times; moreover, unlike in 8-DR.R-infected animals, the viremia was no longer predominantly erythrocyte associated but rather was equally distributed among erythrocyte, leukocyte, and plasma fractions. Mitogen-dependent lymphocyte proliferation of swine peripheral blood mononuclear cells in vitro was reduced by 90 to 95% following infection with 8-DR.R but remained unaltered following infection with Δ8-DR, suggesting that 8-DR has immunosuppressive activity in vitro. Together, these results suggest an immunosuppressive role for 8-DR in the swine host which facilitates early events in viral infection. This may be of most significance for ASFV infection of its highly adapted natural host, the warthog.

Safety and immunogenicity of mammalian cell derived and Modified Vaccinia Ankara vectored African swine fever subunit antigens in swine

“…For example, SPAAN (used in Vaxign) identified many spike glycoproteins from Human coronavirus as adhesins (Sachdeva et al, 2005) and the spike protein (S), a membrane component of Severe acute respiratory syndrome coronavirus (SARS-CoV), was identified to be critical for viral pathogenesis (Li et al, 2003b) and experimentally proven to be effective as a vaccine candidate (Bisht et al, 2004). The identified adhesion probability scores for EP402R (CD2v) (score 0.457) and EP153R (score 0.372) correlate with previous reports that have shown that these proteins are involved in ASFV hemadsorption (HA) in vitro (Borca et al, 1998(Borca et al, , 1994bGalindo et al, 2000;Neilan et al, 1999;Rodríguez et al, 1993;Ruiz-Gonzalvo et al, 1996). Adhesion probability scores were identified for B646L/p72 (score 0.25), CP204L/p30 (score 0.363), and E183L/p54 (score 0.566), all previously reported to be potential protective antigens (Argilaguet et al, 2012;Gómez-Puertas et al, 1998;Lokhandwala et al, 2016;Neilan et al, 2004).…”

Human cytomegalovirus UL7, a homologue of the SLAM‐family receptor CD229, impairs cytokine production

“…In addition, this African swine fever virus protein has been shown to have an immunomodulatory role in vivo, by impairment of bystander lymphocyte functionality. 29 In the current study, we report the identification of a CD229 structural homologue encoded by the HCMV gene UL7. This viral product contains an Ig-like domain with significant amino acid identity with the CD229 N-terminal Ig-variable domain responsible for the homophilic interactions that result in T-cell signalling.…”

Vaccine Potential of Two Previously Uncharacterized African Swine Fever Virus Isolates from Southern Africa and Heterologous Cross Protection of an Avirulent European Isolate

“…Coggins (1968) and Vig ario et al (1974) reported that viruses lacking the ability to cause haemadsorption generally tend to be non-virulent or are of reduced virulence due to the deletion of the gene encoding the CD2v protein. This deletion delays the onset of viraemia and dissemination of viruses within infected pigs (Borca et al, 1998) and was previously linked to natural attenuation of ASFV. Nevertheless, other authors have found that certain nonhaemadsorbing ASFVs cause ASF (Leitão et al, 2001).…”