Herpes simplex virus typeⅠ induces an autophagic response and accelerates the fragmentation of apolipoproteins E protein

OBJECTIVE How infection of Herpes simplex virus typeⅠ(HSV-1) induces enhancement of autophagy.MEHTODS The wild type HSV-1 strain Kos 1.1 was propagated in Vero cells and purified.SK-N-SH cells seeded in DMEM/F12 were exposed to HSV-1 with 6 h or 12 h and multiplicity of infection(MOI) for 10 or 40 in each experiment.The infectious titers of the HSV-1 samples were determined by plaque assays.MDC staining to test the number of autophagosome within the cell after infection with time and moi was indicated in each experiment.At the molecular level,Western blotting and immunofluorescence analyses were done to study the expression of the proteins related to the cell autophagy.The mRNA transcribed from the gene related to autophagy was quantified by reverse transcription followed by real-time PCR.After intranasal infection of different transgenic mice,immunoflurorence studies were done to detected the expression of Aβ42 and proteins related to autophagy from the brain sections.Morris water maze experiment was performed to test the change of spatial learning and memory between different transgenic mice.RESULTS SK-N-SH cell showed time-and moi-dependent increase of MDC positive staining after HSV-1 infection.Western blotting analysis showed that LC3-Ⅱ was less in mock-infected cells but it was detected after 12 h from 10 to 40 moi HSV-1 infected cells.The level increased in a viral concentration-dependent manner.In agreement with the Western blotting results,direct fluorescence microscopy revealed that the signals of LC3 were consistent with their localization on autophagic compartments.P62,another protein related to autophagoysome formation,also increased with MOI.15 ku fragment of intracellular apolipoproteins E(APOE) protein increased after infection,but at the mRNA level it remained the same.The expression of APP showed less decrease but intracellular Aβ42 increased significantly compared with the mock group.Within the brain,after intranasal infection for 7 d,autophagy related proteins LC3 b and P62 increased as well,at the same time Aβ42 was found co-localized with LC3 b within the cell.Behavior test revealed that 17-month-old APOE4 mice had pool spatial learning and memory after infection compared with other groups.CONCLUSION HSV-1 induces an autophagic response and accelerates the fragmentation of APOE protein.