Adaptation of African swine fever virus to porcine kidney cells stably expressing CD163 and Siglec1

Abstract

African swine fever virus (ASFV) is a complex large DNA enveloped virus that causes African swine fever (ASF) with a fatality rate of up to 100%, seriously threatening the global swine industry. Due to the strict cell tropism of ASFV, there is no effective in vitro cell line, which hinders its prevention and control. Herein, we analyzed genome-wide transcriptional profiles of ASFV-susceptible porcine alveolar macrophages (PAMs) and non-susceptible cell lines PK15 and 3D4-21, an found that PAM surface pattern recognition receptors (PRRs) were significantly higher and common differential genes were significantly enriched in phagocytosis compared with that observed in PK15 and 3D4-21 cell lines. Therefore, endocytosis functions of host cell surface PRRs may play key roles in ASFV infection in vitro. ASFV was found to be infective to PK15 and 3D4-21 cell lines overexpressing CD163 and Siglec1, and to the PK15S1-CD163 cell line stably expressing CD163 and Siglec1. However, the PK15 and 3D4-21 cell lines overexpressing CD163 or Siglec1 alone were not infectious. Simultaneous interference of CD163 and Siglec1 in PAMs with small interfering RNA (siRNA) significantly reduced the infectivity of ASFV. However, siRNA interference of CD163 and Siglec1 respectively did not affect ASFV infectivity. ASFV significantly inhibited IFN expression levels in PAMs and PK15S1-CD163 cells, but had no effect on PK15 and 3D4-21 cell lines. These results indicate that CD163 and Siglec1 are key receptors for ASFV-infected host cells, and both play a synergistic role in the process of ASFV infection. ASFV inhibits IFN expression in susceptible cells, thereby downregulating the host immune response and evading the immune mechanism. The discovery of the ASFV receptor provides novel ideas to study ASFV and host cell interactions, pathogenic mechanisms, development of receptor blockers, vaccine design, and disease resistance breeding.

Infection of human macrophage-like cells by African swine fever virus

“…IFN-α-induced activation of STAT1 and IRF1 is responsible for the production of IL-10 by human monocytes/macrophages[23]. However, it was shown that ASFV inhibits the expression of type I IFN in susceptible cells[24,25,26]. Consistent with this data, we also observed low levels of IFN-α in the supernatants of Mφ0 cells exposed to the active virus.…”

Assessment of the Macrophage Scavenger Receptor CD163 in Mediating Glaesserella parasuis Infection of Host Cells

“…However, none of the corresponding peptide motifs within porcine CD163 were capable of binding G. parasuis , indicating different pathogen–host interaction mechanisms among different pathogens. We should not totally exclude certain roles of other peptides within CD163 in mediating infection, especially the interaction between CD163 and the virulence factors of G. parasuis , although based on previous reports [ 16 , 18 , 19 , 21 , 22 ] and our investigation, we presume that this possibility is very low.…”

“…Research on S. mutans has mapped their bacterial binding site to the CD163p2 and CD163p3 peptide motifs in the second and third SRCR domains of human CD163, respectively [ 16 ]. In pigs, porcine CD163 has also been proved to be the key receptor of ASFV [ 18 ] and PRRSV [ 19 ]. When lacking the CD163 SRCR5 domain, porcine alveolar macrophages isolated from genome-edited pigs were fully resistant to PRRSV; thus, their normal biological function is just as important [ 30 ].…”

“…The conversed inductions of surface CD163 by virulent strains could also reflect an early inhibition of the inflammatory response, leading to the failure of bacterial clearance during the process of systemic infection. On the other hand, high levels of proteolytically shed CD163 in serum may indicate a shutdown mechanism for excessive inflammatory cytokine production at the later stage of infection, as speculated by Fabriek et al (2009) [ 16 ], while investigating the synergistic roles of CD163 with other receptor(s), such as Siglec1 and ASFV infection [ 18 ], in the process of G. parasuis infection could be a way to uncover the mediating mechanism of CD163. The work on discovering resistant or susceptible candidates of G. parasuis infection never stops, and genome wide screening based on CRISPR/Cas9 technology has started in our lab.…”

“…So far, a collection of studies have supported the idea that CD163 is a binding receptor for some bacteria and viruses during the process of infection [ 16 , 17 ]. In pigs, CD163 acts as a key receptor on host cells for African swine fever virus (ASFV) [ 18 ]. CD163 knockout pigs can survive when exposed to highly pathogenic PRRSV [ 17 , 19 ].…”