Relevance of Rodent Models of Depression in Clinical Practice: Can We Overcome the Obstacles in Translational Neuropsychiatry?

The diagnosis of a mental disorder generally depends on clinical observations and phenomenological symptoms reported by the patient. The definition of a given diagnosis is criteria based and relies on the ability to accurately interpret subjective symptoms and complex behavior. This type of diagnosis comprises a challenge to translate to reliable animal models, and these translational uncertainties hamper the development of new treatments. In this review, we will discuss how depressive-like behavior can be induced in rodents, and the relationship between these models and depression in humans. Specifically, we suggest similarities between triggers of depressive-like behavior in animal models and human conditions known to increase the risk of depression, for example exhaustion and bullying. Although we acknowledge the potential problems in comparing animal findings to human conditions, such comparisons are useful for understanding the complexity of depression, and we highlight the need to develop clinical diagnoses and animal models in parallel to overcome translational uncertainties.

Sustained elevation of kynurenic Acid in the cerebrospinal fluid of patients with herpes simplex virus type 1 encephalitis.

Herpes simplex virus (HSV) type 1 encephalitis (HSE) is a viral infectious disease with commonly occurring neurodegeneration and neurological/cognitive long-term sequelae. Kynurenic acid (KYNA) is a neuroactive tryptophan metabolite, which is elevated in the cerebrospinal fluid (CSF) during viral infection as a result of immune activation. The aim of the study was to investigate the role of endogenous brain KYNA for the long-term outcome of the disease. CSF KYNA concentration was analyzed in 25 HSE patients along the course of the disease and compared with that of 25 age-matched healthy volunteers. Within 3 weeks of admission CSF KYNA of HSE patients was markedly elevated (median 33.6 nM) compared to healthy volunteers (median 1.45 nM). Following a decline observed after 1-2 months, levels of CSF KYNA were elevated more than 1 year after admission (median 3.4 nM range: 1-9 years). A negative correlation was found between initial CSF KYNA concentrations and severity of the long-term sequelae. This study show a marked elevation in CSF KYNA from patients with HSE, most pronounced during the acute phase of the disease and slowly declining along the recovery. We propose that brain KYNA might potentially protect against neurodegeneration while causing a long-lasting loss in cognitive function associated with the disease.

Preparation of 3-substituted-1-isopropyl-1H-pyrazolo[3,4-d]pyrimidin-4-amines as RET kinase inhibitors.

A series of 3-substituted-1-isopropyl-1H-pyrazolo[3,4-d]pyrimidin-4-amines have been designed, synthesized, and evaluated as RET protein kinase inhibitors. On the basis of docking results, a small library of pyrazolopyrimidine compounds with an extended hydrophobic side arm was synthesized. The most promising of the compounds (7a) displayed efficient inhibition in vitro and good selectivity when tested on a panel of kinases. Furthermore, 7a inhibited GDNF-induced RET phosphorylation of ERK1/2 in MCF-7 breast cancer cells at concentrations as low as 100 nM.

Elevation of cerebrospinal fluid interleukin-1ß in bipolar disorder.

BACKGROUND: In recent years, a role for the immune system in the pathogenesis of psychiatric diseases has gained increased attention. Although bipolar disorder appears to be associated with altered serum cytokine levels, a putative immunological contribution to its pathophysiology remains to be established. Hitherto, no direct analyses of cerebrospinal fluid (CSF) cytokines in patients with bipolar disorder have been performed. METHODS: We analyzed CSF cytokine concentrations in euthymic patients with diagnosed bipolar disorder type I (n = 15) or type II (n = 15) and healthy volunteers (n = 30) using an immunoassay-based protein array multiplex system. RESULTS: The mean interleukin (IL)-1ß level (4.2 pg/mL, standard error of the mean [SEM] 0.5) was higher and the IL-6 level (1.5 pg/mL, SEM 0.2) was lower in euthymic bipolar patients than in healthy volunteers (0.8 pg/mL, SEM 0.04, and 2.6 pg/mL, SEM 0.2, respectively). Patients with 1 or more manic/hypomanic episodes during the last year showed significantly higher levels of IL-1ß (6.2 pg/mL, SEM 0.8; n = 9) than patients without a recent manic/hypomanic episode (3.1 pg/mL, SEM 1.0; n = 10). LIMITATIONS: All patients were in an euthymic state at the time of sampling. Owing to the large variety of drugs prescribed to patients in the present study, influence of medication on the cytokine profile cannot be ruled out. CONCLUSION: Our findings show an altered brain cytokine profile associated with the manifestation of recent manic/hypomanic episodes in patients with bipolar disorder. Although the causality remains to be established, these findings may suggest a pathophysiological role for IL-1ß in bipolar disorder.

Acyclovir inhibition of IDO to decrease Tregs as a glioblastoma treatment adjunct.

Regulatory T cells, Tregs, are a subset of lymphocytes that have immunosuppressive attributes. They are elevated in blood of glioblastoma patients and within this tumor's tissue itself. Indoleamine 2,3-dioxygenase, IDO, converts tryptophan to kynurenine. IDO activity enhances Treg formation by pathways that are unknown. Experimentally, inhibition of IDO decreases Treg function and number in rodents. The common anti-viral agent acyclovir inhibits IDO. Acyclovir may thereby decrease Treg function in glioblastoma. If it can be confirmed that Treg counts are elevated in glioblastoma patients' tumor tissue, and if we can document acyclovir's lowering of tissue Treg counts by a small trial of acyclovir in pre-operative glioblastoma patients, a trial of acyclovir effect on survival should be done given the current poor prognosis of glioblastoma and the well-established safety and low side effect burden of acyclovir.

Oral HIV-exposure elicits mucosal HIV-neutralizing antibodies in uninfected men who have sex with men.

OBJECTIVE: To determine whether oral sexual exposure to HIV-1 (HIV) results in HIV-neutralizing activity in saliva of uninfected men who have sex with infected men? DESIGN: Saliva samples were collected from HIV IgG seronegative men (n = 25) whose male partners were HIV infected and from low-risk healthy controls (n = 22) and analyzed for HIV-neutralizing capacity. METHODS: The presence of neutralizing activity in saliva was tested in a peripheral blood mononuclear cell-based assay using primary HIV isolates. Self-reporting questionnaires described the individuals' sexual behaviors and routes of possible HIV exposure. RESULTS: Of 25 exposed, uninfected individuals (EUI), 21 reported receptive unprotected oral intercourse, whereas three of the 25 reported unprotected anal receptive intercourse. Whole saliva from both EUI and low-risk healthy controls contained HIV-neutralizing activity. However, a significant difference was seen when analyzing the salivary IgA1 fraction: 13 of 25 EUI neutralized HIV, whereas none of the 22 controls had this capacity. The neutralizing capacity of the EUI males persisted during 2 years of follow-up. CONCLUSION: Unprotected oral sex evokes a salivary IgA1-mediated HIV-neutralizing response that persists over time during continuous exposure in uninfected male partners of infected men.

Human glutaredoxin-1 catalyzes the reduction of HIV-1 gp120 and CD4 disulfides and its inhibition reduces HIV-1 replication.

Reduction of intramolecular disulfides in the HIV-1 envelope protein gp120 occurs after its binding to the CD4 receptor. Protein disulfide isomerase (PDI) catalyzes the disulfide reduction in vitro and inhibition of this enzyme blocks viral entry. PDI belongs to the thioredoxin protein superfamily that also includes human glutaredoxin-1 (Grx1). Grx1 is secreted from cells and the protein has also been found within the HIV-1 virion. We show that Grx1 efficiently catalyzes gp120, and CD4 disulfide reduction in vitro, even at low plasma levels of glutathione. Grx1 catalyzes the reduction of two disulfide bridges in gp120 in a similar manner as PDI. Purified anti-Grx1 antibodies were shown to inhibit the Grx1 activity in vitro and block HIV-1 replication in cultured peripheral blood mononuclear cells. Also, the polyanion PRO2000, that was previously shown to prevent HIV entry, inhibits the Grx1- and PDI-dependent reduction of gp120 disulfides. Our findings suggest that Grx1 activity is important for HIV-1 entry and that Grx1 and the gp120 intramolecular disulfides are novel pharmacological targets for rational drug development.

HIV-1 neutralizing activity is correlated with increased levels of chemokines in saliva of HIV-1-exposed uninfected individuals.

AIM: Mucosal HIV-1 exposure stimulates a variety of mucosal immune responses, including IgA1-mediated virus neutralization, even in the absence of an established infection. We hypothesized that other immune molecules might also contribute to the HIV-1 neutralizing activity observed in the mucosal secretions of HIV-1 exposed uninfected individuals. METHODS: Saliva samples were collected from HIV-1 seronegative high-risk female sex workers (FSW) from Nairobi. Samples were also collected from HIV-1 IgG positive FSW and HIV-1 IgG negative low-risk women from the same geographical area. In all samples, IgA2, secretory leukocyte protease inhibitor (SLPI), regulated on activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein 1 alpha and beta (MIP-1alpha and -beta) and monocyte chemoattractant protein-1 (MCP-1) were quantified. The IgA1-depleted saliva samples were subsequently tested for neutralizing capacity in a PBMC-based neutralization assay using a primary HIV-1 clade A isolate to determine biological relevance of the measured molecules. RESULTS: HIV-1 specific neutralization was present in the IgA1-depleted fraction from saliva of both HIV-1 seropositive (9 of 10) and high-risk individuals (36 of 45) but not in HIV-1 IgG-negative control subjects (0 of 8). In the high-risk individuals, higher levels of CC-chemokines were seen in those that could neutralize HIV-1 as compared with those that could not (P<0.05). CONCLUSION: The HIV-1 neutralizing activity in saliva of HIV-1-exposed high-risk individuals is not only mediated by IgA1, but is also present in IgA1-depleted fractions and is associated with increased levels of CC-chemokines. Such innate immune factors may be important in limiting HIV-1 mucosal transmission.

The antimicrobial peptide LL-37 inhibits HIV-1 replication.

The antimicrobial peptide LL-37 is the only cathelicidin that has been described in humans. LL-37 exerts chemotactic, immunomodulatory and angiogenic effects; activities that are mediated through binding to the formyl peptide receptor like (FPRL)-1 receptor. Agonistic ligation of FPRL-1 can also induce down-regulation of HIV-1 chemokine receptors and reduce susceptibility to HIV-1 infection in vitro. Therefore, we have evaluated the capacity of LL-37 to inhibit HIV-1 infection in vitro. Here we demonstrate that LL-37 inhibits HIV-1 replication in PBMC, including primary CD4(+) T cells. This inhibition was readily reproduced using various HIV-1 isolates without detectable changes in the target cell expression of HIV-1 chemokine receptors. Accordingly, the HIV-1 inhibitory effect was shown to be independent of FPRL-1 signalling. Given the epithelial expression of LL-37, it may contribute to the local protection against HIV-1 infection.

Plasma and mucosal fluid from HIV type 1-infected patients but not from HIV type 1-exposed uninfected subjects prevent HIV type 1-exposed DC from infecting other target cells.

Highly exposed persistently seronegative (HEPS) individuals have previously been shown to mount HIV-1-specific humoral and cellular immune responses in the mucosa, despite their uninfected status. It is thus possible that HEPS individuals are protected from HIV-1 infection at the mucosal level. Recent work supports the hypothesis that dendritic cells are involved in the establishment of a mucosal HIV-1 infection as well as the dissemination to other target cells. However, no previous study has investigated if samples collected from HEPS individuals have the capacity to prevent HIV-1 infection in the presence of dendritic cells in vitro. We therefore established an assay that measures HIV-1 neutralization in cocultures of HIV-1-exposed dendritic cells (DC) and PBMC. Plasma and cervicovaginal lavage (CVL) samples from HIV-1-infected patients and HEPS individuals, enrolled in a well-characterized sex worker cohort in Kenya, were evaluated. Most plasma and CVL samples of HIV-1-infected patients neutralized HIV-1 in the DC/PBMC cocultures. Neither plasma nor CVL samples of most HEPS individuals had this capacity. However, they readily neutralized HIV-1 infection of PBMC alone. This may suggest that protection against HIV-1 infection in HEPS individuals occurs prior to interaction between HIV-1-exposed DC and other target cells.

Presence of HIV-1 neutralizing IgA antibodies in primary HIV-1 infected patients.

The initial control of viral replication during primary HIV-1 infection is dominated by CD8+ T-cell mediated responses. Neutralizing IgG to autologous virus is first detected in serum weeks after this response when the viraemia has already declined. However, the mucosal and systemic HIV-1 neutralizing IgA response during primary HIV-1 infection in patients treated with HAART has not been studied previously. The presence of HIV-1 neutralizing IgA antibodies in serum (n=10 patients) and semen (n=6 patients) samples was tested against a laboratory adapted HIV-1 isolate and against primary HIV-1 isolates, representing different clades and phenotypes. The patients received HAART during the study period and were followed from primary HIV-1 infection and up to 72 weeks. Overall, HIV-1 neutralizing IgA activity could be demonstrated in serum from 5 of 10 primary HIV-1 infected patients at inclusion, although the response was restricted to only 1 of the 4 tested isolates. In semen samples, HIV-1 neutralizing IgA activity was seen in 2 of 5 patients against at least 1 of the HIV-1 isolates. In conclusion, a restricted but early neutralizing IgA response can be detected in serum and semen in primary infected patients treated with HAART.

Dichotomy between CD1a+ and CD83+ dendritic cells in lymph nodes during SIV infection of macaques.

The prevalence and differentiation of dendritic cells (DC) in lymphoid tissue of simian immunodeficiency virus (SIV)-infected cynomolgus monkeys was studied during disease progression. Lymph node biopsies were consecutively obtained from clinical rapid and slow progressors until the development of disease consistent with simian acquired immunodeficiency syndrome (sAIDS) occurred. Quantitative evaluation of CD1a+ DC and the expression of DC antigens related to maturation (CD83, DC-LAMP and S100b) were performed at the single cell level by in situ image analysis. Despite a persistent prevalence of CD1a+ DC in lymphoid tissue during disease progression, there was a subsequent drop of mature CD83+, DC-LAMP+ and S100b+ DC, correlating with the decline of CD4+ T cells in blood. Thus, disease progression to sAIDS was associated with impaired maturation of DC, and lack of CD83, DC-LAMP and S100b expression.

Cross-protection against mucosal simian immunodeficiency virus (SIVsm) challenge in human immunodeficiency virus type 2-vaccinated cynomolgus monkeys.

In this study we compared the efficacy of live attenuated human immunodeficiency virus type 2 (HIV-2) vaccine alone versus boosting with live non-pathogenic HIV-2 following priming with ALVAC HIV-2 (recombinant canarypox virus expressing HIV-2 env, gag and pol). Six monkeys were first inoculated intravenously with live HIV-2(SBL-6669) and 7 to 10 months later were challenged intrarectally with 10 MID(50) of cell-free simian immunodeficiency virus (SIV) strain SIVsm. One monkey was completely protected against SIV infection and all five monkeys that became SIV-infected showed a lower virus replication and an initial lower virus load as compared with a parallel group of six control animals. In another experiment five monkeys were immunized either three times with ALVAC HIV-2 alone or twice with ALVAC HIV-2 and once with purified native HIV-2 gp125. The monkeys were then challenged with HIV-2 given intravenously and finally with pathogenic SIVsm given intrarectally. After challenge with SIVsm, three of five monkeys were completely protected against SIVsm infection whereas the remaining two macaques became SIV-infected but with limited virus replication. In conclusion, vaccination with an ALVAC HIV-2 vaccine followed by exposure to live HIV-2 could induce cross-protection against mucosal infection with SIVsm and seemed to be more efficient than immunization with a live HIV-2 vaccine only.