Abstract
Antibody-dependent enhancement (ADE) contributes to the pathogenesis of porcine reproductive and respiratory syndrome virus (PRRSV)-persistent infection. However, the mechanisms of PRRSV-ADE infection are still confusing. A clear understanding of the event upon virus infection by the ADE pathway has become crucial for developing efficient intervention of the PRRSV infection. In this study, an ADE assay showed that PRRSV-ADE infection in porcine alveolar macrophages (AMs) significantly decreased the production of interferon-α (IFN-α) and tumor necrosis factor-α (TNF-α), and significantly increased the production of interleukine-10 (IL-10). A gene knockdown assay based on small interfering RNA (siRNA) showed that both Fc gamma receptor I (FcγRI) and FcγRIII in porcine AMs were involved in PRRSV-ADE infection. An activation assay showed that specific activation of FcγRI or FcγRIII in porcine AMs during PRRSV infection not only significantly decreased the production of IFN-α and TNF-α, but also significantly increased the production of IL-10 and significantly facilitated PRRSV replication. In conclusion, our studies suggested that ADE downregulated the production of IFN-α and TNF-α in porcine AMs maybe via FcγRI and FcγRIII, thereby leading to enhanced PRRSV infection.
Highlights
Receptors for the Fc portion (FcγRs) of immunoglobulin G (IgG) belong to the Ig receptor superfamily and are expressed on the surface of most immune cells [1]
porcine reproductive and respiratory syndrome virus (PRRSV)+Immune Complexes (ICs)-infected cells were significantly more than that in culture supernatants of PRRSV+PNIPRRSV+PNI-infected cells at any time point post-infection, showing that PRRSV-Antibody-dependent enhancement (ADE) activity was infected cells at any time point post-infection, showing that PRRSV-ADE activity was present in present in porcine
Our studies showed that PRRSV induced a high level of IFN-α production in porcine alveolar macrophages (AMs) in early infection and slightly that induced a high level of IFN-α production in porcine
Summary
Receptors for the Fc portion (FcγRs) of immunoglobulin G (IgG) belong to the Ig receptor superfamily and are expressed on the surface of most immune cells [1]. FcγRs play important roles in the innate and adaptive immune responses by triggering pleiotropic biological functions, such as release of inflammatory mediators, regulation of cellular activation and differentiation, controlling of peripheral tolerance, processing and presentation of antigens, phagocytosis of microorganisms, endocytosis of immune complexes, antibody-dependent cellular cytotoxicity and antibody protection against viral infection [2,3,4,5]. FcγRs from mammalian species are categorized into the activating (FcγRI, FcγRIIa/IIc, FcγRIII and FcγRIV) and inhibitory (FcγRIIb) receptors [6,7]. The two different types of receptors display coordinate and opposing roles in the immune system. FcγRs are distinguished by their varying affinity for IgG. FcγRI exhibits a high affinity for IgG and is capable of binding monomeric IgG [1]. FcγRII and FcγRIII show a low affinity for monomeric IgG and can only interact effectively with multimeric immune complexes [8].
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