BMC Neuroscience

BMC Neuroscience

1-beta-D-Arabinofuranosyl-E-5-(2-bromovinyl)uracil (brovavir) and acyclovir were compared for their antiviral effects against herpes simplex virus type 1 (HSV-1) model infections in mice. Recent studies have shown the importance of Toll-like receptors (TLRs) in the immune response to HSV-1 infection. Regardless of the route of administration, BVDU effected a significant reduction in the mortality rate of mice infected with herpes simplex virus type 1 if treatment was initiated shortly after virus infection, i.e., day 0 or 2 (or day 4, if BVDU was administered subcutaneously) postinfection, at a dosage of 80 mg/kg per day or higher. Among the 85 patients assessed at 6 months, 30 (35%) had a poor outcome, which led to death in 13 patients (15%) and severe disability in 17 (20%). Characteristics of these patients are presented in Table 1 . At a later time, emotional or physical stress can reactivate the virus to cause an infection of the brain. The 3-year cumulative incidence of herpesvirus-associated encephalitis/myelitis and post-transplant lymphoproliferative disorder (PTLD) was 6.3% ±1.9% and 4.1% ±1.2%, respectively.

These lesions were also associated with severe spatial memory deficits in surviving animals. The trigeminal ganglia harbor latent virus DNA [4, 5]. This might suggest either that the virus presented a diminished replication rate or that the inflammatory response could be enhancing viral clearance in the brain. Brovavir, but not acyclovir, at a dose of 200 mg/kg reduced the mortality. However, the precise mechanisms by which HSV-1 causes death are not clear. Neutrophils may contribute to virus clearance through the release of antiviral cytokines like TNF-α or oxygen and nitrogen reactive species [23]. Neutrophils are the first cells to infiltrate the cornea and they remain the predominant cell type during the development of HSV-1 keratitis [24–26].

Older age was significantly associated with mortality at six months (71 years in deceased patients vs. West Nile virus (WNV): This virus was first isolated from an adult woman with a fever in the West Nile District of Uganda in 1937. Herpesviruses, the family of neurotropic viruses, may cause encephalitis/myelitis of various degrees of severity in immunocompetent individuals [1,2]. Classically, HSE in adult patients manifests as bilateral cerebrocortical lesions in the temporal lobes, with or without parietal and frontal lobe involvement (19). HSV-1 infection control appears to be highly dependent on the cellular immune response, including local tissue cells such as microglia and resident macrophages, as well as inflammatory infiltration by cells such as monocytes and CD8+ T lymphocytes [19–23]. At the same time, trigeminal ganglia and brainstems of CCR5-/- mice revealed an increase of CD4 and/or CD8 T cells [22]. In the present work, there was also a significant change in leukocyte recruitment during HSV-1 brain infection.

The CHO reporter cell lines,22,23 a kind gift from Douglas T. These conflicting results suggest that there is a significant difference between the immune response elicited in the periphery (i.e. cornea) and the response in the CNS in CCR5-/- mice infected with HSV-1. 57 in patients with low morbidity, p=0.04), delayed lumbar puncture (1 day vs. Blood transfusions are the exception; the virus may be passed among people by blood transfusions if the donor is infected. In recipients of allo-HSCT, most post-transplant lymphoproliferative disorder (PTLD) occurs in the early stages of transplantation, and the platelet counts of some patients are too low to perform CNS biopsy. HSV-1 strain 17 syn+ was propagated and titrated using plaque assay on rabbit skin fibroblasts (CCL68; American Type Culture Collection, Manassas, VA).

BMC Neuroscience
The high prevalence of HSV-1 and the considerably increased number of immunosuppressed individuals due to diseases or to therapeutic transplantation, heighten the importance of comprehending the mechanisms of immune defense against the virus in a herpetic encephalitis model. Conversely, it was described a significant decrease in the survival rate of TNFR1−/− mice infected by intracranial route [30]. The use of intracranial route is a way to elicit an immune response directly from the CNS, aiming to exclude immune activation in the periphery. Subsequently, the cells were counted and 1 × 105 cells stained with phycoerythrin-labeled anti-CD25 (mouse monoclonal antibody to human CD25, R-PE conjugate; Caltag Laboratories, Burlingame, CA) 1:200 in PBS, on ice in the dark, for 30 minutes. In contrast to neutrophil increase, the brain of CCR5-/- infected mice showed a reduction of CD8+ cells. CCR5 is a member of the CC family of chemokine receptors that is expressed on a variety of leukocytes, including T cells and macrophages [31]. Moreover, we used a technique of quantitative real time PCR, limiting the risks of false positive samples.

However, it may wane in later years. Forty-six patients received related donor and 39 received unrelated donor transplants. Briefly, 5 µm brain sections were deparaffinized in xylene and hydrated through graded alcohols and finally in deionized water. The role played by CD8+ lymphocytes in HSV-1 encephalitis is still controversial. While one study reported no significant differences in viral load or viral reactivation when the virus was injected in cornea of mice lacking CD8+ T cells [33], another report showed persistent elevated viral titers in the brain of CD8-deficient, suggesting a role for CD8+ T cells in the control of HSV-1 replication [34]. In the current study, we found no difference in the levels of CD8+ lymphocytes in CCR5-/- mice, thus, these cells cannot account for the decrease in viral load in the brain of CCR5-/- mice. Each experiment was repeated three times.

This may result in an up-regulation of MHC molecules and secretion of more chemotactic molecules [35]. The inflammatory site during encephalitis involves the immune cells cited above and also B cells. However, in that recently published study, not all patients were treated by acyclovir. The virus cycles between the daytime-biting treehole mosquito (Aedes triseriatus) and hosts such as chipmunks and squirrels. The blood EBV- and CMV-DNA were monitored in recipients weekly for the first 3 months, every 2 weeks between 4 to 9 months, monthly between 10 to 24 months and every 3 months between 25 to 36 months post-transplantation. The analysis of lesion distribution and characterization were performed by examination of 10 different coronal brain sections per mouse taken from brain regions relative to bregma at approximately +2.96 mm, +1.46 mm, +1.18 mm, −1.46 mm, −3.3 mm, −3.08 mm, −3.80 mm, −5.02 mm, −5.40 mm, and −6.48 mm (22). Using intravital microscopy, we found that CCR5-/- infected mice presented an increase of leukocyte adhesion to the pial microvasculature.

Bearing in mind that CCR5 is one of the most important receptors in leukocyte migration, this result seems paradoxical. However, one limitation of this technique is the impossibility to identify the kind of leukocyte that roll and adhere in vessels [8]. The reaction was performed at 95°C for 1 minute, 50°C for 1 minute, and 72°C for 1 minute for 40 cycles. Here we found an increase in cerebral chemokine levels, including KC/CXCL1, MIG/CXCL9, MCP-1/CCL2, RANTES/CCL5 and cytokine TNF-α in CCR5-/- infected mice. Blocking the action of CCL5 receptor may result in compensatory mechanisms leading to the overproduction of other chemokines [37]. First, although our sample size was greater than in other studies [8, 10, 11], the number of patients with available CSF samples was still small. Most recently, there were 20 reported cases in New Orleans in 1999.

The diagnosis of herpesvirus-associated CNS-PTLD was based on the criteria of World Health Organization and European Conference on Infections in Leukemia as well as the literature [18,26]. Brain leukocytes obtained from the 30–70% Percoll interface were treated with Fc Block (anti-CD32/CD16, 2% normal rat and 2% normal mouse serum) to inhibit non-specific antibody binding and were stained with anti-mouse immune cell surface markers for 45 min at 4°C [anti-CD45-Allophycocyanin (APC), anti-CD11b-FITC (BD Biosciences, San Jose, CA)] and analyzed by flow cytometry. CXCR3-/- mice infected with HSV-1 in the cornea had an increase in CCL5, CXCL10, and IFN-γ in the brainstem and IL-6 in the brain tissue. In addition, CXCR3-/- infected mice exhibited high levels of chemokines which were coincident with high viral titers in the brainstem. The authors suggested that the absence of CXCR3 expression would suppress the capacity of T cells to respond to HSV-1 infection through limited trafficking to the trigeminal ganglia [39]. The plates were incubated and observed during 5 days. However, it is not clear whether the virus depends on this receptor to enhance viral multiplication or the immune system mounts a different response in its absence, resulting in more efficient viral control.

Our study has several limitations. This is, however, unfeasible and unrealistic. We did not evaluate natural killer cells as well. Other herpesvirus-DNA of blood was negative in both recipients and donors at the time of transplantation. At the end of 90 s, animals were placed on the platform for 15 s to allow them to process the distal cues. There is a possibility that compensatory mechanisms could eventually impact the immune-associated phenotype of CCR5-/- mice. Nevertheless, no differences between non-infected WT and knock out mice were observed in the parameters assessed.

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