Several rabies virus (RV) vaccine strains containing an aspartic acid (Asp) or glutamic acid (Glu) instead of an arginine (Arg) at position 333 of the RV glycoprotein (G) are apathogenic for immunocompetent mice even after intracranial inoculation. However, we previously showed that the nonpathogenic phenotype of the highly attenuated RV strain SPBNGA, which contains a Glu at position 333 of G, is unstable when this virus is passaged in newborn mice. While the Glu 333 remained unchanged after five mouse passages, an Asn 194 3Lys 194 mutation occurred in RV G. This mutation was associated with increased pathogenicity for adult mice. Using site-directed mutagenesis to exchange Asn 194 with Lys 194 in the G protein of SPBNGA, resulting in SPBNGA-K, we show here that this mutation is solely responsible for the increase in pathogenicity and that the Asn 194 3Lys 194 mutation does not arise when Asn 194 is exchanged with Ser 194 (SPBNGA-S). Our data presented indicate that the increased pathogenicity of SPBNGA-K is due to increased viral spread in vivo and in vitro, faster internalization of the pathogenic virus into cells, and a shift in the pH threshold for membrane fusion. These results are consistent with the notion that the RV G protein is a major contributor to RV pathogenesis and that the more pathogenic RVs escape the host responses by a faster spread than that of less pathogenic RVs.

Antidepressants produce various immunomodulatory effects, as well as an attenuation of the behavioral responses to immune challenges, such as lipopolysaccharide (LPS). To explore further the effects of antidepressants on neuroimmune interactions, rats were treated daily with either fluoxetine (Prozac) or saline for 5 weeks, and various behavioral, neuroendocrine, and immune functions were measured following administration of either LPS or saline. Chronic fluoxetine treatment significantly attenuated the anorexia and body weight loss, as well as the depletion of CRH-41 from the median eminence and the elevation in serum corticosterone levels induced by LPS. Chronic treatment with imipramine also attenuated LPS-induced adrenocortical activation. In rats and in mice, which normally display a biphasic body temperature response to LPS (initial hypothermia followed by hyperthermia), chronic treatment with fluoxetine completely abolished the hypothermic response and facilitated and strengthened the hyperthermic response. The effects of antidepressants on the responsiveness to LPS are probably not mediated by their effects on peripheral proinflammatory cytokine production, because LPS-induced expression of TNFSeveral lines of evidence indicate that antidepressants produce various immunomodulatory effects. In depressed patients, the effects of antidepressants are variable and seem to be related to the immune status of the patients at the initiation of the treatment. When depression was associated with immune activation, antidepressants reduced immune function and cytokine secretion. For example, the increased plasma levels of IL-6 during acute depression were normalized by 8-week treatment with fluoxetine (Sluzewska et al. 1995), the increased monocyte counts in depressed patients were reduced following 6-weeks treatment with tricyclic antidepressants (TCAs) (Seidel et al. 1996), and the increased numbers of leukocytes and neutrophils were also reduced by antidepressant treatment (Maes et al. 24 , NO . 5 1997). On the other hand, when immune functions were found to be normal, antidepressants had no immunological effects; for example, chronic moclobemide treatment had no effect on monocytes functions, TNF ␣ production or IFN ␥ levels (Landmann et al. 1997). Moreover, in a study of depressed patients who exhibited immune suppression before treatment, the TCA clomipramine increased the production of IL-1 ␤ , IL-2, and IL-3 (Weizman et al. 1994).In experimental animals, TCAs as well as selective serotonin reuptake inhibitors (SSRIs) produce mainly immune suppression and anti-inflammatory effects. For example, antidepressant treatment in vivo inhibited the increased acute phase response in olfactory bulbectomized rats, a useful animal model of depression (Song and Leonard 1994), reduced the production of interleukin-1 (IL-1) and IL-2 in a chronic mild stress model of depression (Kubera et al. 1996), inhibited immune activation in rats with experimental allergic neuritis (Zhu et al. 1994), and produced anti-inflammatory ...

To investigate the involvement of various cellular and humoral aspects of immunity in the clearance of rabies virus from the central nervous system, (CNS), we studied the development of clinical signs and virus clearance from the CNS in knockout mice lacking either B and T cells, CD8+ cytotoxic T cells, B cells, alpha/beta interferon (IFN-α/β) receptors, IFN-γ receptors, or complement components C3 and C4. Following intranasal infection with the attenuated rabies virus CVS-F3, normal adult mice of different genetic backgrounds developed a transient disease characterized by loss of body weight and appetite depression which peaked at 13 days postinfection (p.i.). While these animals had completely recovered by day 21 p.i., mice lacking either B and T cells or B cells alone developed a progressive disease and succumbed to infection. Mice lacking either CD8+ T cells, IFN receptors, or complement components C3 and C4 showed no significant differences in the development of clinical signs by comparison with intact counterparts having the same genetic background. However, while infectious virus and viral RNA could be detected in normal control mice only until day 8 p.i., in all of the gene knockout mice studied except those lacking C3 and C4, virus infection persisted through day 21 p.i. Analysis of rabies virus-specific antibody production together with histological assessment of brain inflammation in infected animals revealed that clearance of CVS-F3 by 21 days p.i. correlated with both a strong inflammatory response in the CNS early in the infection (day 8 p.i.), and the rapid (day 10 p.i.) production of significant levels of virus-neutralizing antibody (VNA). These studies confirm that rabies VNA is an absolute requirement for clearance of an established rabies virus infection. However, for the latter to occur in a timely fashion, collaboration between VNA and inflammatory mechanisms is necessary.

SummaryThe polyclonal stimulation of T cells by bacterial superantigens is involved in the pathogenesis of the toxic shock syndrome in certain staphylococcal and streptococcal infections. Here we describe the onset and kinetics of superantigen-induced cytokine production in situ in spleens of normal BALB/c mice monitored at the level of cytokine mRNA expression by in situ hybridization. Messenger RNAs for interleukin 2 (IL-2), interferon % and tumor necrosis factors (TNF) c~ and/3 were not expressed at detectable levels in spleens of unstimulated animals but became visible already 30 min after intraperitoneal application of 50/~g staphylococcal enterotoxin B. All mRNA levels showed peak expression approximately 3 h after injection and a slow decrease up to 24 h after injection. Expression of the mRNAs was restricted to the T cell-dependent area of the periarteriolar lymphatic sheets of the spleen. Interestingly, TNF-oe mRNA showed a biphasic response, the early appearing mRNA had the same localization as the other mRNAs, whereas after 3 h TNF-ol mRNA showed a broader distribution indicating a second cell population producing TNF-o~. The expression of IL-2 and TNF proteins in the serum increased in parallel to the observed mRNA changes with a slight delay. The presence of macrophages was not required for the expression of the cytokine mRNAs in the spleen as the expression was unchanged in macropbage-depleted mice. Only the second phase of TNF-c~ mRNA expression was abrogated in such animals. The expression of all mRNAs was completely suppressed by prior administration of cyclosporin A. These data show that nonphagocytic cells are the essential superantigen-presenting cells in vivo and indicate that at least part of the pathogenetic TNF-ol is T cell derived. n in situ analysis of a T cell response should provide information on the distribution of induced events in the affected organs and on the kinetics of the response. In contrast, in vitro experiments allow only a vague approximation of the kinetics of an immune response and do not give much information on the significance of cellular interactions for the events in vivo. It is therefore surprising that such analyses in vivo have only rarely been performed so far, possibly because of the usually low frequency of responding cells in antigen-specific immune reactions.The study of a superantigen response has the advantage that a superantigen activates a large fraction of T cells by a mechanism closely resembling antigen recognition. Superantigens, such as the staphylococcal enterotoxins, cross-link variable parts of the TCR with MHC class II antigens on APCs. Consequences of this massive T cell activation are the transient expansion of the stimulated T cell subset followed by death and development of anergy in these cells, and eventually shocklike symptoms due to a burstlike expression of different cytokines (1, 2).TNF has been reported to play a critical role in the development of superantigen-induced toxic shock because an antibody against TNF has a protective eff...

Background and purpose: Intraglandular injection of botulinum toxin (BoNT) leads to a transient denervation of the submandibular gland and this is associated with reduced salivary secretion. The purpose of the present study was to verify whether temporary acinar atrophy occurs simultaneously with chemical denervation of the glands. Experimental approach: Tissue specimens of the right submandibular gland taken from 18 Wistar rats after intraglandular injection of BoNT A, BoNT B, or a combination of both were examined. As a sham control, an equivalent volume of saline was injected into the left submandibular gland. Morphometric measurements, immunohistochemistry, electron microscopy and western blot analysis were used to analyse the morphological and functional changes of the denervated glands. Key results: Morphological and ultrastructural analyses of the cell organelles and secretory granula showed a clear atrophy of the acini, which was more prominent in glands injected with the combination of BoNT/A and B. Morphometric measurements of the glandular acini revealed a significant reduction of the area of the acinar cells after injection of BoNT (P ¼ 0.031). The expression of amylase was significantly reduced in BoNT treated glands. Conclusions and implications: Intraglandular application of BoNT induces structural and functional changes of the salivary glands indicated by glandular atrophy. These effects may be due to glandular denervation induced by the inhibition of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) involved in acetylcholine release at the neuroglandular junction and also specially inhibition of those involved in exocytosis of the granula of the acinar cells.