Effects of nerve growth factor and phorbol derivative on reactivation of herpes simplex virus type 1 in cultured cells of latently infected adult mouse trigeminal ganglia

Reactivation of herpes simplex virus type 1 (HSV-1) occurred rapidly in cells of latently infected adult mouse trigeminal ganglia which were cultured in serum-free medium in the presence of sufficient nerve growth factor (NGF). However, HSV-1 reactivation was delayed significantly in ganglionic cultures in the absence of exogenous NGF or in cultures treated with 2-aminopurine in the presence of NGF. The delayed viral reactivation in ganglionic cultures without NGF was accelerated by treatment with phorbol myristate acetate or dibutyryl cyclic AMP. Culture conditions which affected HSV-1 reactivation did not affect replication of HSV-1 in normal ganglionic cultures.     

Severity of experimentally reactivated herpetic eye disease is related to the neurovirulence of the latent virus

The authors examined the eye diseases produced during acute and experimentally reactivated infections of rabbits intranasally inoculated with high and low neurovirulent strains of herpes simplex virus, type-1 (HSV-1). Experimental reactivation of latent trigeminal ganglionic infection was accomplished by an injection of cyclophosphamide followed by one injection of dexamethasone the next day. Neither drug, when given as a single injection, reactivated latent HSV-1 infection. During acute and reactivated phases of high neurovirulent HSV-1 strain infection, many rabbits developed very severe conjunctivitis and keratitis. Some rabbits developed hemorrhagic corneal lesions, and a few became blind. Only a few rabbits with acute and reactivated low neurovirulent virus strain infections developed mild conjunctivitis. The high neurovirulent strain was recovered from tear film more frequently than the low neurovirulent strain during reactivated infections. By use of 3H-labelled DNA prepared from purified virus to probe trigeminal ganglionic tissues in situ, both strains of virus were found to establish ganglionic latency to about the same degree. Reactivation correlated with an increase in the amount of HSV-1 RNA per ganglionic neuron and a change in subcellular location. These studies indicate that the relative neurovirulence of the infecting strain determines the ease with which it can be reactivated from latency and the severity of the reactivated ocular disease produced.     

Acute renal insufficiency in hemorrhagic fever with renal syndrome

PURPOSE: Propranolol, a beta-adrenergic antagonist, has been shown to block hyperthermically-induced ocular recurrence of HSV-1 in mice and reduce spontaneous ocular viral shedding and herpetic corneal lesions in latently infected rabbits. The present study was performed to determine the effect of propranolol on epinephrine iontophoresis-induced ocular recurrence and immunosuppression-induced ocular recurrence in the rabbit eye model. METHODS: New Zealand white rabbits were infected with HSV-1 strain 17Syn+ or McKrae. After latency was established, the animals were injected intramuscularly with saline (placebo), or propranolol (5-200 mg/kg) twice daily, and then induced with epinephrine iontophoresis or cyclophosphamide and dexamethasone administration. Tear film swabs were cultured to determine the frequency of viral shedding. RESULTS: Propranolol administered at a range of doses did not affect the frequency or duration of viral shedding following epinephrine or cyclophosphamide/dexamethasone induction as compared to saline treatment. CONCLUSION: These results demonstrate that propranolol does not significantly reduce ocular HSV-1 shedding following induction by epinephrine iontophoresis or immunosuppression. By inference, these results suggest two possibilities: (1) that viral pathways leading to spontaneous and induced shedding of virus are under separate control mechanisms or (2) in rabbits, these inducers are of such potency that propranolol is ineffectual.     

Recurrent acyclovir-resistant herpes simplex in an immunocompromised patient: can strain differences compensate for loss of thymidine kinase in pathogenesis?

To investigate how acyclovir-resistant (ACVr) herpes simplex virus (HSV) evades drug therapy and causes disease, HSV-1 isolates from a bone marrow transplant (BMT) patient were studied. The patient developed ACVr disease after an initial BMT and, following a second BMT, reactivated ACVr HSV despite high-dose acyclovir prophylaxis. ACVr isolates from each episode contained the same point mutation in the viral thymidine kinase (tk) gene, documenting the emergence, latency, and reactivation of this mutant. The mutants were exceedingly impaired for TK activity in sensitive enzyme, plaque autoradiography, and drug-susceptibility assays. Nevertheless, these mutants and a tk deletion mutant constructed in the same genetic background reactivated from latency in mouse trigeminal ganglia, in contrast to similar mutants from laboratory strains. It is hypothesized that alleles in the clinical isolate compensate for the loss of TK in this animal model. Such genetic variability may be important for ACVr disease in humans.     

Characterisation and cloning of a calmodulin-like domain protein kinase from Chlamydomonas moewusii (Gerloff)

Traditional herbal medicines with anti-herpes simplex virus type 1 (HSV-1) activity in vivo were examined for their prophylactic effects on recurrent HSV-1 infection in mice. Mice were intradermally infected with HSV-1 in the pinna and recurrent HSV-1 disease was induced by ultraviolet irradiation. Herbal extracts arrested the progression of recurrent HSV-1 disease, reduced the incidence of severe erythema and/or vesicles in the pinna, and/or shortened the period of severe recurrent lesions compared with water-administered mice (P < 0.01 or 0.05). Similarly, the prophylactic treatment of herbal extracts limited the development of recurrent skin lesions induced by stripping with cellophane tape physically. The prophylactic efficacy on recurrence was confirmed by the absence of HSV DNA in the skin lesions. HSV-1 genome was revealed to exist in the trigeminal ganglia but not in the pinna of latently infected mice before stimuli by a nested-polymerase chain reaction assay. After stimuli, HSV-1 genome was detected in both pinna and trigeminal ganglia of latently infected mice administered with water. However, prophylactic treatment decreased the rate of detection of HSV-1 genome in the stimulated pinna. Thus, the herbal extracts exhibited prophylactic efficacy against recurrent HSV-1 disease in mice and modulated the recurrent HSV-1 infection.     

The insulinotropic region of gastric inhibitory polypeptide; fragment analysis suggests the bioactive site lies between residues 19 and 30

9-(4-Hydroxybutyl)-N2-phenylguanine (HBPG) is a new viral thymidine kinase inhibitor that we tested for the ability to prevent recurrences of herpetic keratitis. Eighteen squirrel monkeys (Saimiri scuireus) were infected in both corneas with the Rodanus strain of herpes simplex virus type 1 (HSV-1). All corneas showed typical dendritic keratitis 3 days after infection, followed by spontaneous healing. On day 21, the monkeys were randomized into two coded groups and ocular examinations were begun. One group received intraperitoneal (i.p.) injections of HBPG, 150 mg/kg, in a corn oil suspension every 8 h, and the other group received i.p. injections of the corn oil vehicle only. On day 22, recurrences were induced by reducing the temperature of the room in the late afternoon so that a low of 18 degrees C was achieved during the night. After the morning treatment, room temperature was raised to the normal ambient temperature (24-27 degrees C), and treatment was discontinued. Treatment was reinstituted on day 27, the room temperature was lowered again on day 28, and treatment was again discontinued as before. Third and fourth cycles of treatment and cold stress were begun on days 34 and 69. Ocular examinations were continued until day 73, at which point the code was broken. We found that the HBPG treatment significantly reduced the number of corneas with recurrences during the treatment periods, compared with recurrences in untreated, cold-stressed animals (P = 0.01).     

Reactivation of herpes simplex virus type 1 in the mouse trigeminal ganglion: an in vivo study of virus antigen and cytokines

Reactivation of herpes simplex virus type 1 (HSV-1) in the trigeminal ganglion (TG) was induced by UV irradiation of the corneas of latently infected mice. Immunocytochemistry was used to monitor the dynamics of cytokine (interleukin-2 [IL-2], IL-4, IL-6, IL-10, gamma interferon [IFN-gamma], and tumor necrosis factor alpha [TNF-alpha]) and viral antigen production in the TG and the adjacent central nervous system on days 1 to 4, 6, 7, and 10 after irradiation. UV irradiation induced increased expression of IL-6 and TNF-alpha from satellite cells in uninfected TG. In latently infected TG, prior to reactivation, all satellite cells were TNF-alpha+ and most were also IL-6(+). Reactivation, evidenced by HSV-1 antigens and/or infiltrating immune cells, occurred in 28 of 45 (62%) TG samples. Viral antigens were present in the TG in neurons, often disintegrating on days 2 to 6 after irradiation. Infected neurons were usually surrounded by satellite cells and the foci of immune cells producing TNF-alpha and/or IL-6. IL-4(+) cells were detected as early as day 3 and were more numerous by day 10 (a very few IL-2(+) and/or IFN-gamma+ cells were seen at this time). No IL-10 was detected at any time. Our observations indicate that UV irradiation of the cornea may modulate cytokine production by satellite cells. We confirm that neurons are the site of reactivation and that they probably do not survive this event. The predominance of TNF-alpha and IL-6 following reactivation parallels primary infection in the TG and suggests a role in viral clearance. The presence of Th2-type cytokines (IL-4 and IL-6) indicates a role for antibody. Thus, several clearance mechanisms may be at work.     

Recrudescence of herpes simplex virus type 1 in latently infected rats after trauma to oral tissues

Tooth extraction in rats was used to trigger a latent HSV-1 infection. HSV-1 was inoculated unilaterally in the rat palates. Eight weeks later two molars were removed bilaterally. The trigeminal ganglia were co-cultivated and HSV-1 was isolated from 63% of the ganglia on the infected sides but from only 11% on control sides. The immune response pattern was analysed by immunoblotting of rat serum, and strong reactivity to HSV-1 specific cell polypeptides and glycoproteins (ICP6, gC, pgC, gD) was seen after reactivation. The extraction sockets were histopathologically evaluated and showed healing on the infected side in 26% compared to 63% in contralateral control sockets. The effect of acyclovir (ACV) treatment was elucidated and was found to influence the subsequent development of antibodies and to promote healing of the sockets. Vesiculation in intra- and subepithelial tissue was present on the infected side in 58% but in only 12% of ACV-treated animals. The present study in rats has shown that a latent HSV-1 infection can be established and reactivated by tooth extraction. Reactivation resulted in delayed healing of sockets on the latently infected side but not on the contralateral control side. HSV-1 reactivation was demonstrated serologically by immunoblotting. Healing was significantly promoted by administration of ACV, which also supports the contention that HSV-1 interferes with the healing process.     

Mode of action of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl) cycloprop-1'-yl]methyl]guanine (A-5021) against herpes simplex virus type 1 and type 2 and varicella-zoster virus

The mode of action of (1'S,2'R)-9-([1', 2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl)guanine (A-5021) against herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus (VZV) was studied. A-5021 was monophosphorylated at the 2' site by viral thymidine kinases (TKs). The 50% inhibitory values for thymidine phosphorylation of A-5021 by HSV-1 TK and HSV-2 TK were comparable to those for penciclovir (PCV) and lower than those for acyclovir (ACV). Of these three agents, A-5021 inhibited VZV TK most efficiently. A-5021 was phosphorylated to a mono-, di-, and triphosphate in MRC-5 cells infected with HSV-1, HSV-2, and VZV. A-5021 triphosphate accumulated more than ACV triphosphate but less than PCV triphosphate in MRC-5 cells infected with HSV-1 or VZV, whereas HSV-2-infected MRC-5 cells had comparable levels of A-5021 and ACV triphosphates. The intracellular half-life of A-5021 triphosphate was considerably longer than that of ACV triphosphate and shorter than that of PCV triphosphate. A-5021 triphosphate competitively inhibited HSV DNA polymerases with respect to dGTP. Inhibition was strongest with ACV triphosphate, followed by A-5021 triphosphate and then (R,S)-PCV triphosphate. A DNA chain elongation experiment revealed that A-5021 triphosphate was incorporated into DNA instead of dGTP and terminated elongation, although limited chain extension was observed. Thus, the strong antiviral activity of A-5021 appears to depend on a more rapid and stable accumulation of its triphosphate in infected cells than that of ACV and on stronger inhibition of viral DNA polymerase by its triphosphate than that of PCV.     

Diagnostic and therapeutic retrograde ureterorenoscopy (URS)

Two recent studies provided new evidence on the latency of HSV-1 DNA in 15.5% of olfactory bulbs and in 72.5% of trigeminal nerves from human corpses at forensic postmortems (1) and in 35% of 40 autopsied human brains (2). In the latter brains, latent HSV-1 DNA was found in the olfactory bulbs, amygdala, hippocampus, brain stem, and trigeminal ganglia. Although in these studies it is not known by which route HSV-1 entered the olfactory bulbs and brain, experimental studies in mice (3) revealed that injection of HSV-1 into the olfactory bulbs leads to virus migration into the brain amygdala and hippocampus via the olfactory nerve and locus coeruleus. If the olfactory ciliary nerve epithelium is the port of entry of HSV-1 into the olfactory bulbs and brain in humans as well, protection of the nose against HSV-1 infection may be needed to prevent virus latency in neurons in the amygdala and hippocampus (3). Infection of humans by HSV-1 was estimated to increase from 18.2% in the 0-20 year population group to 100% in persons older than 60 years (1), indicating that worldwide human populations at all ages are at risk of brain infection by the olfactory nerve route. In addition, both primary infection and reactivation of latent DNA in the brain may lead to damage of neurons in the brain involved in memory, learning, and behavior, as observed in infected, acyclovir-treated mice (3). The current introduction of a live apathogenic varicella-zoster virus (VZV) vaccine to immunize children against chickenpox (4) may suggest that the time is ripe for immunization of children and adults against HSV-1 infections, especially infections by the olfactory nerve route, to prevent potential brain damage.