RESUMEN

Mitogen-activated protein kinases (MAPKs) are a family of serine-threonine protein kinases involved in many cellular processes, including cell proliferation, differentiation, inflammation, and cell death. Activation of several MAPKs, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), p38, and c-Jun N-terminal kinase (JNK), results in stimulation of activator protein 1 (AP-1), which promotes gene transcription. Previous studies have demonstrated that varicella-zoster virus (VZV) infection activates ERK1/2, p38, and JNK to promote viral replication, but the underlying mechanism(s) is unclear. To identify viral proteins responsible for the activation of MAPK, we used a proteomic approach to screen viral proteins for AP-1 promoter activation by an AP-1-luciferase reporter assay. We found that VZV ORF12 protein, located in the tegument of virions, enhances AP-1 reporter activity. This effect of ORF12 protein was markedly inhibited by a MAPK/ERK kinase 1 and 2 (MEK1/2) inhibitor (U0126), partially blocked by a p38 inhibitor (SB202190), but not inhibited by a JNK inhibitor (SP600125). Expression of VZV ORF12 protein in cells resulted in phosphorylation of ERK1/2 and p38 but not JNK. Infection of cells with a VZV ORF12 deletion mutant resulted in reduced levels of phosphorylated ERK1/2 (p-ERK1/2) compared to infection with wild-type VZV. Furthermore, deletion of ORF12 rendered VZV-infected cells more susceptible to staurosporine-induced apoptosis. In conclusion, VZV ORF12 protein activates the AP-1 pathway by selectively triggering the phosphorylation of ERK1/2 and p38. Cells infected with a VZV ORF12 deletion mutant have reduced levels of p-ERK1/2 and are more susceptible to apoptosis than cells infected with wild-type VZV.

Asunto(s)

RESUMEN

The acute involution of the thymus is induced by either exogenous or endogenous factors, including some infections (infection type involution). The present study was focused on both detection and immunocytochemical analysis of NGF immunopositive mast cells in child thymus with acute infection-induced involution. Autopsy thymus specimens from children with infection diseases (Sepsis, Encephalomyelitis, Varicella) were examined at light and electron microscopic level and compared to normal infantile thymuses. We observed a redistribution of NGF immunopositive mast cells in infection-affected child thymus, which lobular architecture was collapsed. A positive correlation between the degree of the involutive changes, increased distribution and enhanced NGF immunoreactivity of mast cells was defined. The possible involvement of NGF immunopositive mast cells in the process of acute thymus involution is discussed.

Asunto(s)

RESUMEN

The severity of varicella infection in 124 expatriates from the Asian continent was compared to that in 120 Saudi nationals, seen in Arar Central Hospital, Arar, Saudi Arabia, between January 1992 and December 1994. Persistent fever (defined as a raised body temperature more than 37.4 degrees C lasting more than 5 days), extensive skin eruptions (defined as extensive, when more than 50% of the body surface was affected) and transient elevation of hepatic enzymes (aspartate transaminases > 37 U/L and alanine transaminases > 40 U/L) after excluding other possible causes, occurred significantly more in expatriates than in Saudis. The mean duration of the illness in expatriates was 15.9 +/- 3.41 days as compared to a mean duration of 13.1 +/- 3.52 days in Saudis. This difference was statistically significant (p < 0.01 Student's t-test). The findings in this study suggest that varicella infection runs a more severe course in expatriates from the Asian continent as compared to the Saudis. Treatment with the antiviral agent acyclovir may be indicated in this group of expatriates with varicella infection.

Asunto(s)

RESUMEN

Replication-defective retroviral vectors were created that contained chimeric genes composed of either the albumin (ALB) or the alpha-fetoprotein (AFP) transcriptional regulatory sequences linked to the coding domain of the thymidine kinase gene from Varicella zoster virus (VZV TK). These viruses were used to infect the human hepatoblastoma cell line, HepG2. Subsequent to infection, the infected cells were single-cell cloned. The level of expression of VZV TK from the chimeric genes correlated with the level of endogenous expression of ALB or AFP in most clones, indicating that the transcription of the chimeric VZV TK gene is controlled in a similar manner to the endogenous ALB or AFP genes, and that sites of viral integration are less important to overall gene expression. Most importantly, as the expression of the endogenous ALB gene was modified, so was expression of VZV TK from the ALB/VZV TK chimeric gene. This demonstrates that retroviruses can deliver a chimeric gene containing tissue-specific transcriptional regulatory sequences that can respond to endogenous cell regulatory signals resulting in regulated gene expression.

Asunto(s)

RESUMEN

A sensitive enzyme assay with 125I-iododeoxyuridine as substrate and cytidine triphosphate as phosphate donor was used for the direct detection of varicella zoster virus (VZV) deoxythymidine kinase (TK) in human serum. Sera sampled during the incubation period of varicella from 2 patients, a 42-year-old man and his 11-year-old son, have been analysed for TK activity. A simultaneous increase in cellular and VZV TK activity, starting 5 to 3 days before the onset of clinical varicella, was observed.

Asunto(s)

RESUMEN

An enzyme that catalyzes the conversion of CDP to 2'-dCDP in the presence of dithiothreitol (DTT) was detected in ammonium sulfate fractionated-extracts of varicella zoster virus (VZV)-infected cells. This ribonucleotide reductase was antigenically distinguishable from the isofunctional eucaryotic enzyme as well as the ribonucleotide reductases induced by herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). The VZV-induced enzyme was purified to the extent that most of the contaminating enzymes, which would significantly deplete the substrate, were removed. The VZV-induced ribonucleotide reductase exhibited maximum activity in the absence of ATP and/or magnesium and was only weakly inhibited by 2'-deoxynucleoside triphosphates. Furthermore, ADP, UDP and GDP competitively inhibited CDP reduction with Ki (Km) values of 15, 20, 1.8 and 0.88 microM, respectively. These kinetic properties were very similar to those of the correspondingly purified ribonucleotide reductases induced by HSV-1 [Averett et al., J. biol. Chem. 258, 9831 (1983)] and HSV-2 [Averett et al., J. Virol. 52, 981 (1984)] and were dissimilar to the allosterically regulated mammalian enzyme. A723U, an inactivator of HSV-1 ribonucleotide reductase that potentiates the anti-HSV-1 activity of acyclovir [Spector et al., Proc. natn. Acad. Sci. U.S.A. 82, 4254 (1985)], also appeared to inactivate this VZV-induced ribonucleotide reductase and to potentiate the anti-VZV activity of acyclovir.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)