Journal: Journal of Virology
Article Title: African swine fever virus infection enhances CD14-dependent phagocytosis of porcine alveolar macrophages to promote bacterial uptake and apoptotic body-mediated viral transmission
doi: 10.1128/jvi.00690-25
Figure Lengend Snippet: The upregulated CD14 in bystander PAMs facilitates viral transmission by enabling the phagocytosis of more ASFV-containing apoptotic bodies. ( A ) The supernatants from PAMs infected with ASFV (MOI 1) at 3, 6, 12, and 24 hpi were collected, filtered through a 0.1 µm PVDF filter to remove ASFV, and then added to untreated PAMs for culturing for 3 h. The relative level of CD14 mRNA in PAMs was analyzed by qPCR (mean of three independent experiments ± SD). ( B ) The ASFV-removed supernatants from PAMs at 12 and 24 hpi were cultured with untreated PAMs for 3 h, respectively, and then infected with E. coli -EGFP (MOI 10) for 2 h. The “positive CTRL group” represents PAMs that were infected with unfiltered ASFV before bacterial infection. Flow cytometry was used to detect the phagocytic rate of PAMs (mean of three independent experiments ± SD). hpt, hours post-treatment. ( C ) PAMs were incubated with different cytokines at a concentration of 1 ng/mL (20 ng/mL for GM-CSF) for 3 h. The relative level of CD14 mRNA in PAMs was analyzed by qPCR (mean of four independent experiments ± SD). ( D ) The supernatants from PAMs infected with ASFV (MOI 1) at 12 and 24 hpi were collected, filtered through a 0.1 µm PVDF filter to remove ASFV, and extracted viral DNA. The level of CP204L was analyzed by qPCR, and the copy number was calculated using a standard curve (mean of three independent experiments ± SD). ( E ) PAMs were treated for 3 h with the ASFV-removed supernatant that was treated with DNase (4 U/100 µL) at 37°C for 30 min. The expression of CD14 was detected by flow cytometry (mean of three independent experiments ± SD). ( F, G ) PAMs were pre-treated with the TLR9 inhibitor E6446 (10 µM) for 1 h, and then with extracted viral DNA (24 hpi) for 3 h. The DNA extracted from the filtered supernatant of CTRL PAMs was used as the control. All groups were infected with E. coli -EGFP (MOI 10) for 2 h. CD14 MFI ( F ) and phagocytosis of E. coli -EGFP ( G ) were analyzed by flow cytometry (mean of three independent experiments ± SD). ( H ) PAMs were infected with ASFV-mCherry (MOI 2) for 24 hpi. ApoBDs were observed by IFA. Nuclei were stained with DAPI. Scale bar, 100 µm. ( I ) PAMs were infected with ASFV-mCherry (MOI 2) for 24 hpi. Isolated ApoBDs were observed by IFA. Phosphatidylserine (PS) was stained with Annexin V-Alexa 488 at room temperature for 15 min. The arrows point to only a subset of representative ApoBDs containing ASFV-mCherry. Scale bar, 25 µm. ( J ) PAMs were treated with siCD14 for 24 h, then incubated with ASFV-removed supernatant for another 3 h, and subsequently infected with ApoBDs-mCherry for 1 h. The DNA was extracted, and the level of mCherry was analyzed by qPCR (mean of three independent experiments ± SD). ( K ) PAMs were treated with siCD14 for 24 h, then incubated with ASFV-removed supernatant for another 3 h, and subsequently infected with ApoBDs-mCherry for 12 h. The infection efficiency of PAMs was observed by IFA. Nuclei were stained with DAPI. Representative data from multiple experiments are shown. Scale bar, 100 µm. ( L ) Calculate the percentage of infected PAMs (mean ± SD of 10 samples). ( M ) PAMs were treated with siCD14 for 24 h, then incubated with ASFV-removed supernatant for another 3 h, and subsequently infected with ApoBDs-mCherry for 12 h. The titer of ASFV in PAMs was detected using TCID 50 (mean of three independent experiments ± SD). ( N ) The relative levels of CD14 mRNA in PAMs at 3 hpi were analyzed by qPCR. The control inoculum was harvested from PAMs that had been induced to apoptosis by UV irradiation for 60 min. The supernatant and ApoBDs were isolated from it using the same method as the ASFV inoculum. The supernatant was used as the control for infection with ASFV particles, and the ApoBDs were used as the control for infection with ApoBDs (containing ASFV) (mean of three independent experiments ± SD).
Article Snippet: NF-κB inhibitor BAY 11-7082 (HY-13453), cGAS inhibitor RU.521 (HY-114180), STING inhibitor C176 (HY-112906), TLR9 inhibitor E6446 (HY-12756), and bacterial adhesion inhibitor Sibofimloc (HY-12820) were purchased from MedChemExpress (Monmouth Junction, NJ, USA).
Techniques: Transmission Assay, Infection, Cell Culture, Flow Cytometry, Incubation, Concentration Assay, Expressing, Control, Staining, Isolation, Irradiation