Transformation of human lymphocytes by Epstein-Barr virus is inhibited by phosphonoacetic acid

[Acute respiratory distress syndrome complicating Ebstein-Barr virus pneumonia]

Introduction

Chez l’adulte immunocompétent, l’Epstein Barr (EBV) entraîne une maladie autolimitée spontanément résolutive.

Observation

Un syndrome de détresse respiratoire aigu (SDRA) compliquant une pneumonie grave à EBV est rapporté avec le recours à une ventilation artificielle prolongée. Le diagnostic était confirmé par l’usage des sérologies spécifiques et la recherche de la charge d’ADN virale par PCR. À part la stratégie protectrice de la ventilation mécanique, le traitement médical a compris l’utilisation de l’Acyclovir et les immunoglobulines polyclonales dans la phase précoce ainsi que des corticoïdes systémiques dans la phase tardive. La guérison était progressive et complète.

Conclusion

La pneumonie à EBV compliquée d’un SDRA chez les immunocompétents existe. Sa prise en charge est un défi diagnostique et thérapeutique.

Formation of intranuclear replication compartments of Epstein-Barr virus with redistribution of BZLF1 and BMRF1 gene products

The localizations of the Epstein-Barr virus immediate-early transcriptional activator BZLF1 protein ZEBRA, of the BMRF1 early antigen diffuse component (EA-D), and of viral DNA replication were studied in the Burkitt's lymphoma cell line Akata treated with anti-human immunoglobulin antibodies. Prompt and sequential appearance of ZEBRA, EA-D, and viral DNA was observed in about 70% of the cells. At early times after activation, ZEBRA had a diffuse intranuclear distribution, but later it was concentrated in globular regions within the nucleus. EA-D appeared first in a finely stippled pattern and then in a diffuse pattern. At late times, EA-D concentrated in globular regions similar to those with ZEBRA. Double staining for ZEBRA and EA-D revealed that ZEBRA followed the morphological changes of EA-D with a 1-2 hr delay and that both finally coalesced in the same structures, where in situ hybridization localized replicating viral DNA. The redistribution of both ZEBRA and EA-D to these compartments depended upon the replication of lytic viral DNA. These findings indicate that these globular regions are sites for viral replication and that transcription of EBV late genes may be regulated in these structures.

Effects of phosphonoformic and phosphonoacetic acids on developing enamel of rat molars

The effect of a single subcutaneous injection of different dosages of phosphonoformic or phosphonoacetic acid on the developing dental tissues of the rat molar was studied. The substances were injected at different rat ages and effects on the developing teeth were analyzed by means of histochemistry of frozen sections and scanning electron microscopy. Molars of rats injected at the age of 10 or 15 days showed no pathologic changes. Administration of phosphonoacetic acid in a dosage of 10 or 20 mg P/kg b.w. had no demonstrable effect on the dental tissues in any of the animals. Phosphonoformic or phosphonoacetic acid in a dosage of 10 or 30 mg P/kg b.w. respectively induced subameloblastic cysts 24 h after injection to 4-7-day-old rats. The cysts were mainly localized on the mesial sides of the cusps under ameloblasts in the late secretory stage. Calcified depositions were seen in the ameloblastic layer lining the cystic cavities. A thin zone, the staining of which indicated a high mineral content, was seen in the outermost enamel layer under the cysts. A few days later, enamel hypoplasias were seen in areas previously occupied by cysts. A lightly stained line was observed in the enamel matrix demarcating the amount of enamel matrix formed before and after the injection. Hypoplastic lesions were also noted in the enamel surface of newly erupted molars. These findings suggest that the two injected monophosphonates can induce pathologic changes in the developing enamel organ and hypoplasias in the enamel.

Non-sexually transmitted infectious diseases of the oral, nasal, and vaginal mucosae

The skin and mucous membranes are the principal barriers to invasion of the body by microorganisms. Besides functioning as a mechanical barrier, the mucosae are endowed with an array of still poorly characterized specific and nonspecific host defense capabilities. These include the production of mucus, secretory immunoglobulin (IgA), lysozyme, lactoferrin, and alpha-antitrypsin, in conjunction with a low-grade exudation of leukocytes.¹ In addition, the mucosal surfaces of the upper respiratory, gastrointestinal, and lower vaginal and urinary tracts support a large number of “nonpathogenic” microorganisms that comprise the so-called “normal flora.” This commensal flora plays an important and complex role in protecting the host from microbial invasion. Mechanisms for this protection likely include the following: (1) competition for the same nutrients (interference); (2) competition for the same receptors on host cells (tropism); (3) production of bacteriocins, that is, bacterial products that are toxic to other organisms, usually of the same species; and (4) stimulation of crossprotective immune factors such as the “natural antibodies.”¹

The “normal” flora is inconstant and may be altered by dietary factors, debilitation, hormonal events (such as menstruation, pregnancy, and possibly use of oral contraceptives), personal hygiene, medications, intercurrent infection, and probably many others. Antibiotic therapy and menstruation can have a profound effect on the composition of this group of microorganisms.² Disturbance of the delicate host-commensal relationship may cause a clinically significant infection due to these “nonpathogens.” This may occur in response to the aforementioned factors (eg, pregnancy predisposing to vaginal candidiasis) or because of disruption of the anatomic barrier (eg, local mucosal infection at a site of trauma, or injury from cytotoxic drugs) or in association with exogenous infection (eg, rhinoviral infection leading to secondary bacterial otitis media). Invasion by “normal flora” may result in serious systemic illness. A clear example of the latter is the development of infective endocarditis caused by viridans streptococci following a dental procedure.

Structure-activity studies on phosphonoacetate

Phosphonoacetic acid is a selective antiherpesvirus agent. More than 100 congeners of phosphonoacetic acid were evaluated in vitro and in vivo to understand structure-activity relationships in the hope of designing a superior analog. Results showed that the antiherpesvirus activity had highly specific structural requirements. Neither the carboxylic nor the phosphono groups could be replaced. The distance between these two groups is important. Increase of this distance caused complete loss of activity. However, if this distance was maintained, the addition of groups to the methylene carbon resulted in a reduction, but not loss, of activity. On the other hand, decrease of the carbon chain to formic acid did not deteriorate its antiherpes activity. All analogs tested had lower activity than the parent compound. However, some compounds with decreased activity in vitro appeared to have favorable pharmacological properties in vivo.

Epstein-Barr virus transformation of human B lymphocytes despite inhibition of viral polymerase

Epstein-Barr virus transformed human lymphocytes despite the presence of up to 500 microM acyclovir [9-(2-hydroxyethoxymethyl)guanine], a viral DNA polymerase inhibitor. The transformed cells contained multiple Epstein-Barr virus genome copy numbers. Functional viral DNA polymerase is probably not required for cell transformation and the initial amplification of the viral genome.

Long internal direct repeat in Epstein-Barr virus DNA

The nucleotide sequence of the long internal reiteration. IR1, of Epstein-Barr Virus DNA has been determined. The repeat unit is 3,071 base pairs which are 66.8% guanine plus cytosine. There is a CCAAT sequence 39 nucleotides 5' to a TATAA, which could indicate a promotor for transcription. The longest open reading frame is 1,124 base pairs. Also within IR1 is a sequence homologous to the papovavirus origin of DNA replication. The ori-like sequence is within a long palindromic region which is 500 base pairs overall. The palidromic region shares common features with the Alu family members and with eucaryotic transposable elements. The juncture between the short unique region (U1) and IR1 is also sequenced. The transition occurs in BamHI-C at 1,214 base pairs before the BamHI site in the first repeat of IR1. The transition from IR1 to the rightward unique region (U2) has been reported to be at 636 base pairs after the BamHI site in the last repeat of IR1. Thus, relative to the start of IR1 at the juncture with U1, the last copy of IR1 is a partial repeat which contains only the beginning 1,850 base pairs.

Repeat array in Epstein-Barr virus DNA is related to cell DNA sequences interspersed on human chromosomes

The third internal repeat (IR3) simple repeat array in Epstein-Barr virus (EBV) DNA has a high degree of homology to a reiterated component of cell DNAs. 32P-Labeled human or mouse DNAs hybridize to the IR3 sequence on Southern blots of viral DNA. EBV IR3 probe identifies many restriction enzyme fragments on Southern blots of human and mouse DNAs that have extensive homology to IR3. Cytological hybridization shows that IR3 is homologous to at least one region on each human chromosome except the Y chromosome.

Incorporation into DNA of the base analog 2-aminopurine by the Epstein-Barr virus-induced DNA polymerase in vivo and in vitro

The Epstein-Barr virus (EBV)-induced intracellular DNA polymerase was assayed in vitro for the ability to utilize the mutagenic nucleotide analog 2-aminopurine deoxyribose triphosphate (d2apTP), incorporating it as the corresponding monophosphate into DNA or poly[d)(A-T)] template. Bacteriophage T4, lymphocyte alpha, and the EBV particle-associated DNA polymerases were assayed simultaneously for direct comparison. Unlike these three polymerases, which were capable of distinguishing between d2apTP and dATP with a strong preference for the latter, the EBV-induced DNA polymerase only weakly distinguished between dATP and d2apTP and incorporated substantial amounts of d2apTP into template. Detergent-treated lymphocyte nuclei undergoing a high level of EBV DNA synthesis were shown to incorporate the 2-aminopurine analog of dATP into viral DNA. The relative inability of the EBV-induced DNA polymerase to distinguish between the two purine nucleotides reported here is consistent with previous reports on the ready incorporation of other nucleotide analogs into DNA polymerases induced by other herpesviruses. Because most antiherpes agents currently in use or under study are nucleotide analogs, the viral mutagenic properties of these drugs should be examined.

On the continuous culturing of B.95-8 cells in the presence of phosphonoacetic acid

Lymphoblastoid B.95-8 cells were cultured for four months and three weeks in the presence of increasing concentrations (50--200 microgram/ml) of phosphonoacetic acid (PAA). Several weeks after removal of the PAA, the cultures, in parallel with untreated B.95-8 cells, were tested for the presence of: 1) Epstein-Barr virus (EBV) viral capsid antigen (VCA), and b) transformation of human cord blood lymphocytes. There was no difference in the percentage of cells exhibiting VCA in the B.95-8 PAA treated and untreated cells. However, transformation assays indicated 10 times less transforming virus in culture supernatant harvested from B.95-8 cultures treated with PAA, as compared with the control cultures. Electron microscopic studies indicated the presence of virus particles in B.95-8 control cells and their almost complete absence in the PAA-treated cells.

Mechanism of the establishment of Epstein-Barr virus genome-containing lymphoid cell lines from infectious mononucleosis patients: studies with phosphonoacetate

A concentration of disodium phosphonoacetate (PA) has been defined which will reduce the synthesis of infectious EB virus in a producer cell line to 1% of control values but which will not affect the growth of EB virus-transformed cells in a 12-week colony-forming assay. When total mononuclear cells or T-lymphocyte-depleted mononuclear cells from the blood of acute IM patients were cultured in the presence of PA at the above concentration, the regular establishment of EB virus genome-containing cell lines seen in control cultures was almost totally abolished. In further experiments, when T-lymphocyte-depleted IM mononuclear cells were co-cultivated with foetal cells of the opposite sex in the presence and absence of PA, cell lines of mixed or of exclusively foetal origin were obtained not only from control co-cultures but also on those rare occasions when transformed foci developed in PA-treated co-cultures. The results suggest that all cell lines derived from the blood of IM patients are initiated in culture by a two-step process of virus release and secondary infection, and argue against the occurrence of any direct outgrowth of IM cells transformed by the virus in vivo.