HIV-1 replication in HIV-infected individuals is significantly reduced when peripheral blood mononuclear cells are superinfected with HSV-1

Impact of actin polymerization and filopodia formation on herpes simplex virus entry in epithelial, neuronal, and T lymphocyte cells

Herpes simplex virus type 1 (HSV-1) has been known as a common viral pathogen that can infect several parts of the body, leading to various clinical manifestations. According to this diverse manifestation, HSV-1 infection in many cell types was demonstrated. Besides the HSV-1 cell tropism, e.g., fibroblast, epithelial, mucosal cells, and neurons, HSV-1 infections can occur in human T lymphocyte cells, especially in activated T cells. In addition, several studies found that actin polymerization and filopodia formation support HSV-1 infection in diverse cell types. Hence, the goal of this review is to explore the mechanism of HSV-1 infection in various types of cells involving filopodia formation and highlight potential future directions for HSV-1 entry-related research. Moreover, this review covers several strategies for possible anti-HSV drugs focused on the entry step, offering insights into potential therapeutic interventions.

Actin Polymerization Is Required for Filopodia Formation Supporting HSV-1 Entry into Activated T Cells

Enhanced HSV-1 production is found in activated T-lymphocytes, but the mechanism is still unknown. In this paper, the HSV-1 entry step in CD3⁺CD4^-CD8^-Jurkat T lymphocytes was investigated. Observation under electron microscopy revealed the level of filopodia formation on the surface of activated Jurkat cells was significantly higher than that of non-activated Jurkat cells especially after adding HSV-1 for 15 min. A significant increase of actin protein was demonstrated in HSV-1 infected, activated Jurkat cells compared to HSV-1 infected, non-activated Jurkat cells. After the cells were treated with 2.5 and 5 µg/mL cytochalasin D, an inhibitor of actin polymerization that causes depolymerization of actin's filamentous form, the actin protein was decreased significantly, resulting in an absence of filopodia formation. In summary, this is the first study revealing that HSV-1 induced filopodia formation through actin polymerization in activated T cells similar to epithelial, mucosal and neuronal cells. This phenomenon supported the virus entry resulting to increased yield of HSV-1 production.

One of the Mechanisms to Increase HSV-1 Uptake in HSV-1-Infected, Activated T Lymphocytes Is the Formation of Filopodia

OBJECTIVES

To explore the host transcription factor E2F-1 and/or any mechanisms that may support viral entry and its effect on the HSV-1 production in anti-CD3-activated Jurkat cells.

METHODS

The expressions of ICP4, HVEM and E2F-1 were studied using reverse transcription-PCR and Western blot. HSV-1 production was determined by plaque titration assay and HSV-1 DNA load was quantified by real-time PCR. The viral uptake was observed by electron microscopy.

RESULTS

In anti-CD3-activated Jurkat cells, there was a significant increase in the HSV-1 production. The expression of ICP4 mRNA after HSV-1 infection occurred 2 h prior to the synthesis of the ICP4 protein, which was significantly higher in activated than nonactivated T cells. There were no significant differences in the expressions of E2F-1 mRNA. The HVEM expression was positively correlated with the HSV-1 DNA in the activated T cells. From the electron micrograph, the formations of filopodia were observed only in HSV-1-infected, activated cells.

CONCLUSIONS

High expressions of viral receptor protein and filopodia formations are the key factors that enhance the HSV-1 entry into activated T lymphocytes, resulting in an increased production of the virus.