Effect of dexamethasone on herpes simplex virus replication in mouse neuroblastoma cells (NB41A3): receptor characteristics

Clinical course and spectrum of intensive care unit patients reactivating herpes simplex-1 virus: a retrospective analysis

Background:

Herpes simplex-1 virus (HSV-1) reactivation in the respiratory tract is common in intensive care unit (ICU) patients. However, susceptible ICU populations are poorly defined. Clinical recognition of HSV infection of the respiratory tract is difficult and the impact of such reactivation is not understood.

Materials and Methods:

A retrospective analysis of HSV-1 positive patients encountered over a 5-year period at a multispecialty ICU was carried out. HSV-1 was identified in respiratory secretions using a qualitative polymerase chain reaction (PCR) technique. Patient charts were reviewed for clinical features that would typify HSV-1 respiratory involvement, and the morbidity and mortality risks found with HSV-1 respiratory involvement.

Results:

A review of 48 HSV-1 positive ICU patients showed that patients reactivating HSV in the respiratory tract fell into one of the three categories: (1) septic elderly patients with and without ARDS, (2) immunosuppressed patients, especially those receiving high-dose steroids, and (3) post-thoracotomy patients. Abnormalities suggestive of HSV-1 reactivation in the respiratory tract included, haemorrhagic or excessive respiratory secretions, concomitant orofacial herpes (42%), and bronchoscopic abnormalities (hemorrhagic ulcers and mucosal friability) (83%). Twenty eight percent of the HSV-1 infected patients experienced postextubation stridor. HSV-1 reactivation was associated with extended ventilator stays, significant mortality (42%), and ventilator-associated pneumonias (52%).

Conclusions:

Identification of susceptible populations and definition of clinical features of HSV-1 related respiratory disease can enable diagnosis of HSV-1 infection in ICU patients. Although detection by a PCR technique can rapidly diagnose HSV-1 reactivation, prospective studies are required to clarify HSV disease versus mere shedding, and understand the impact of HSV-1 reactivation in hospitalized patients.

Steroids for deteriorating herpes simplex virus encephalitis

A 16-month-old girl presented with herpes simplex virus type 1 encephalitis with involvement of bilateral parietofrontal lobes, left thalamus and cerebellum. She was treated with intravenous acyclovir. As her condition deteriorated, high-dose methylprednisolone was administered, resulting in remarkable improvement. This case suggests considering a short course of high-dose steroid therapy in severe herpes simplex encephalitis when there is clinical and radiologic deterioration in spite of appropriate antiviral therapy and decreasing viral load in the cerebrospinal fluid.

Optimization of adenoviral production in human embryonic kidney cells using response surface methodology

Adenoviruses are the most commonly used vectors in clinical trials for gene therapy. How to efficiently produce abundant and high-quality adenoviral vectors for therapeutic research is a challenge for biochemical engineers. A recombinant adenovirus carrying a green fluorescent protein (GFP) gene together with an anchorage-dependent 293 cell line is used as a model system for evaluating the effects of chemicals on adenoviral production in this study. Our aim is to develop a formulation to be added to an infection medium that could enhance the in vitro production of adenoviral vectors. Eleven ingredients obtained from a literature survey were screened for their stimulatory effects on adenoviral production using the 50% tissue culture infectious dose (TCID(50)) method. Among these ingredients, sucrose and mannitol when supplemented to the infection medium significantly increased adenovirus titer. Central composite design and response surface methodology were also adopted to determine the optimal concentrations of sucrose and mannitol. The formulation developed, which is composed of DMEM/F12 medium plus 0.54 M sucrose and 0.37 M mannitol, can significantly increase adenoviral production by 13-fold that of the control (DMEM/F12 medium).

Cytosolic glucocorticoid receptor-interacting proteins

Studies of GR-interacting proteins can provide valuable insights into the regulation of GR cellular signalling. The cytoplasmic localization of GR and reports of GR interaction with such a plethora of other cytoplasmic proteins may point to a unique role for GR in modulating and integrating other signalling pathways. A better insight into these interactions could serve as a tool when trying to understand and modify GR signalling.

Replication of equid herpesvirus-1 (EHV-1) in the testes and epididymides of ponies and venereal shedding of infectious virus

Six Welsh Mountain pony colts were infected intranasally with the Ab4 isolate of EHV-1. Clinical and virological monitoring demonstrated mild upper respiratory tract disease, with nasal shedding of virus and establishment of a cell-associated viraemia. Detailed pathological examination of the urogenital tract was performed post mortem on days 4-9 post-infection (PI). EHV-1 was isolated from the epididymis on day 8 and the testis on day 9 PI, with viral replication in endothelial cells of these organs and an associated necrotizing vasculitis and thrombosis. Productive viral infection of germinal epithelium was not observed. In a further study, three Welsh Mountain pony stallions were infected intranasally with Ab4, which again resulted in mild upper respiratory tract disease and the establishment of a cell-associated viraemia. Semen samples were collected up to day 60 PI. Two stallions showed a decrease in the proportion of morphologically normal sperm. Significant numbers of inflammatory cells were observed in the sperm-rich fraction of ejaculates collected from one stallion between days 16 and 28 PI; infectious virus was recovered from the semen of this animal between days 17 and 25 PI, after the cessation of viraemia. The affected stallion appeared clinically normal over the period of venereal EHV-1 shedding.

Induction of herpes simplex virus type 1 immediate-early gene expression by a cellular activity expressed in Vero and NB41A3 cells after growth arrest-release

Infected cell protein 0 (ICP0), a major immediate-early regulatory protein of herpes simplex virus type 1 (HSV-1), activates expression of all classes of HSV genes as well as a variety of heterologous viral and cellular genes. Previous studies have shown that a cellular activity expressed maximally in Vero cells 8 h after release from growth arrest in the G0/G1 phase of the cell cycle can enhance plaque formation and gene expression of a mutant virus (7134) lacking both copies of the gene encoding ICP0 (W. Cai and P. Schaffer, J. Virol. 65:4078-4090, 1991). This observation suggests that the cellular activity can substitute for ICP0 to activate viral gene expression. To further characterize this cellular activity, Vero and NB41A3 (mouse neuroblastoma) cells were transfected at various times after release from growth arrest with promoter-chloramphenicol acetyltransferase (CAT) constructs containing promoters representing the major kinetic classes of HSV genes, and CAT activity was measured from 2 to 24 h postrelease. The results of these tests demonstrate that CAT expression from immediate-early promoter-CAT plasmids was enhanced 10- and 3-fold when Vero and NB41A3 cells were transfected at 6 and 2 h postrelease, respectively. In contrast, only low levels of immediate-early promoter-driven CAT activity were apparent when cells were transfected at later times postrelease. No significant stimulation of CAT activity was observed from promoter-CAT plasmids containing representative early or late HSV promoters or a heterologous viral (simian virus 40 early) promoter. Differences in the efficiency of uptake of plasmid DNA by cells at various times postrelease did not account for the observed differences in CAT expression. Unlike Vero cells, in which cell division resumed after release from growth arrest, division of NB41A3 cells did not resume. Rather, these cells displayed morphological features suggestive of a differentiated phenotype. Collectively, these findings demonstrate that a cellular activity expressed in Vero and NB41A3 cells after release from growth arrest can activate HSV gene expression by enhancing immediate-early gene expression.

Hormonal modulation of herpes simplex virus replication in a mouse neuroblastoma cell line

In this study, the effect of the synthetic glucocorticoid hormone dexamethasone (DXM) on HSV replication was studied in a DXM receptor-positive mouse neuroblastoma (NB) cell line. In cells treated with 10(-7) M DXM and then infected with HSV, there was a statistically significant 9-18-fold increase in the amount of virus produced in these cells compared to untreated controls. Adsorption kinetic studies with HSV were performed in DXM-treated NB cells and untreated controls. It was found that there was a significant increase in the adsorption rate of HSV in the DXM-treated cells as compared with the controls. During the course of these studies, a strain of NB cells was noted to have lost its ability to stimulate HSV replication following DXM treatment. Receptor binding assays were performed on cytosols prepared from NB cells that responded with an increase in HSV titers to DXM treatment and the new strain of NB cells that was DXM refractile. These latter cells were found to have lost their DXM receptors. These results indicate that the modulation of HSV replication of DXM treated cells was regulated by the presence of DXM receptors in these cells. Once lost, the cells do not respond to DXM treatment with increased HSV replication. These observations may lead to a clinical assay to determine patients with high glucocorticoid levels who may be at risk of recurrent herpes infections.