Porcine circovirus type 2 exploits JNK-mediated disruption of tight junctions to facilitate Streptococcus suis translocation across the tracheal epithelium

Abstract

Porcine circovirus type 2 (PCV2) is considered as the primary pathogen of porcine circovirus-associated disease (PCVAD), which results in significant economic losses worldwide. Clinically, PCV2 often causes disease through coinfection with other bacterial pathogens, including Streptococcus suis (S. suis), and especially the highly prevalent S. suis serotype 2 (SS2). The present study determined that continuous PCV2 infection in piglets down-regulates tight junction proteins (TJ) ZO-1 and occludin in the lungs. Swine tracheal epithelial cells (STEC) were used to explore the mechanisms and consequences of disruption of TJ, and an in vitro tracheal epithelial barrier model was established. Our results show that PCV2 infection in STEC decreases the expression levels of ZO-1 and occludin and increases the permeability of the tracheal epithelial barrier, resulting in easier translocation of SS2. Moreover, Western blot analysis indicates that PCV2 infection activates the JNK/MAPK pathway. The disruption of TJ in SETC and increased permeability of the epithelial barrier induced by PCV2 could be alleviated by inhibition of JNK phosphorylation, which indicates that the JNK/MAPK pathway regulates the expression of ZO-1 and occludin during PCV2 infection. This study allows us to better understand the mechanisms of PCV2 coinfection with bacterial pathogens and provides new insight into controlling the occurrence of PCVAD. © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article' s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article'

Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

“…Only three in vitro co-infection studies have been performed using different cell types to study S. suis and PCV-2 co-infection (Table 1 ) [ 21 , 99 , 100 ]. The results of the first study, which used poorly characterized immortalized swine tracheal epithelial cells, showed that although no increased adhesion or invasion of S. suis serotype 2 was observed, the virus pre-infection decreased the expression levels of ZO-1 and occludin, increased cell permeability and contributed to the translocation of S. suis serotype 2 across the tracheal epithelium [ 99 ]. Although this in vitro model suggests a possible role of PCV-2 during the initial steps of co-infection by S. suis , the level of replication of PCV-2 in tracheal and other respiratory epithelia in pigs is limited, since PCV-2 infects mainly lymphoblast and monocytes (101).…”

“…Peripheral blood mononuclear cells collected from co-infected piglets showed higher expression levels of inflammatory cytokines, TLR2 and TLR4 and reduced levels of CD4, CD8 and MHC-II. It was also shown that PCV-2 disrupted the integrity and decreased mRNA and protein levels of tight junctions in the lungs of co-infected animals [ 99 ]. Although the authors showed a reduced antibody response against S. suis in virus-infected animals, a poorly characterized commercial kit available in China only was used [ 21 ].…”

Glaesserella parasuis serotype 4 HPS4-YC disrupts the integrity of the swine tracheal epithelial barrier and facilitates bacterial translocation

“…According to our previous study, an in vitro tracheal epithelial barrier model was constructed with STEC using polytetrafluoroethylene 3 μM pore-size membrane transwells (Corning, USA) [ 18 ]. Transwells containing STEC were uninfected or infected with HPS4-YC (MOI 100) for 4, 6, 8, 12, 18 and 24 h. The transepithelial electrical resistance (TEER) was measured with a Millicell ERS-2 electrical resistance system (Millipore, USA).…”

Preparation and Characterization of a New Monoclonal Antibody Specific Against Lawsonia intracellularis and Its Application in Indirect Immunofluorescence and Immunocytochemistry Assay

“…In addition, Western blotting was performed to evaluate the reactivity of the purified Omp2 protein. The same method was described in the reference with some modifications ( 25 ). Briefly, the purified Omp2 protein was transferred onto a polyvinylidene fluoride (PVDF) membrane (Millipore Corporation, USA) after being separated by 12% SDS-PAGE.…”