Correlates of acute lower respiratory tract infections in children under 5 years of age in India

BACKGROUND

In developing countries, acute lower respiratory tract infections (ALRTI) cause considerable morbidity, hospitalisation and mortality in children aged <5 years.

METHODS

A prospective case-control study was conducted to identify potential socio-demographic, nutritional and environmental risk factors for ALRTI. The World Health Organization definition for ALRTI was used for cases. Healthy children attending child immunisation services were enrolled as controls.

RESULTS

A total of 214 children, 107 cases and 107 controls, were enrolled. Among the cases, pneumonia, severe pneumonia and very severe disease constituted respectively 23.3%, 47.7% and 29%. Among cases and controls, the male-to-female ratio (1.3:1 vs. 0.9:1) and the proportion of infants (64.5% vs. 70.1%) were identical. Parents' literacy level was negatively associated with ALRTI. On multivariate logistic regression analysis, low socio-economic status (OR 4.89, 95%CI 1.93-12.36), upper respiratory infections in family members (OR 5.32, 95%CI 2.11-13.45), inappropriate weaning period (OR 3.01, 95%CI 1.12-8.07), malnutrition (OR 1.75, 95%CI 1.84-3.67), pallor (OR 7.18, 95%CI 2.08-24.82) and cooking fuel other than liquid petroleum gas (OR 3.58, 95%CI 1.23-10.45) were found to be significant risk factors (P < 0.05).

CONCLUSIONS

The present study identified various risk factors for ALRTI, some of which are modifiable by effective community education and public health measures.

Long-term engraftment of human natural T regulatory cells in NOD/SCID IL2rγc(null) mice by expression of human IL-2

Regulatory T cells are essential to maintain immune homeostasis and prevent autoimmunity. Therapy with in vitro expanded human nT_Regs is being tested to prevent graft versus host disease, which is a major cause for morbidity and mortality associated with hematopoietic stem cell transplantation. Their usefulness in therapy will depend on their capacity to survive, migrate appropriately and retain suppressive activity when introduced into a transplant recipient. The lack of a suitable animal model for studying the in vivo reconstitutive capability of human nT_Regs is a major impediment for investigating the behavior of adoptively transferred nT_Regsin vivo. We show that injection of a plasmid encoding human IL-2 is necessary and sufficient for long term engraftment of in vitro expanded nT_Regs in NOD-SCID IL2rγc^null mice. We also demonstrate that these in vivo reconstituted T_Regs traffic to different organs of the body and retain suppressive function. Finally, in an IL-2 accelerated GVHD model, we show that these in vivo reconstituted T_Regs are capable of preventing severe xenogenic response of human PBMCs. Thus, this novel ‘hu-T_Reg mouse’ model offers a pre-clinical platform to study the in vivo function and stability of human nT_Regs and their ability to modulate autoimmune diseases and GVHD.

P-body components LSM1, GW182, DDX3, DDX6 and XRN1 are recruited to WNV replication sites and positively regulate viral replication

In mammalian cells, proteins involved in mRNA silencing and degradation localize to discrete cytoplasmic foci called processing or P-bodies. Here we show that microscopically visible P-bodies are greatly diminished following West Nile viral infection, but the component proteins are not depleted. On the other hand, many P-body components including LSM1, GW182, DDX3, DDX6 and XRN1, but not others like DCP1a and EDC4 are recruited to the viral replication sites, as evidenced by their colocalization at perinuclear region with viral NS3. Kinetic studies suggest that the component proteins are first released from P-bodies in response to WNV infection within 12 h post-infection, followed by recruitment to the viral replication sites by 24-36 h post-infection. Silencing of the recruited proteins individually with siRNA interfered with viral replication to varying extents suggesting that the recruited proteins are required for efficient viral replication. Thus, the P-body proteins might provide novel drug targets for inhibiting viral infection.

Association of indoor air pollution with acute lower respiratory tract infections in children under 5 years of age

BACKGROUND

Indoor air pollution is an important risk factor for acute lower respiratory tract infections (ALRTI) in developing countries.

AIM

To determine the relationship of indoor air pollution with ALRTI in children under 5 years of age.

METHODS

A prospective, case-control study of risk factors, particularly indoor air pollution, for developing ALRTI in children under 5 years of age was conducted in Udupi District Hospital. The WHO definition of ALRTI was used. Healthy children attending immunisation services were enrolled as controls. Data pertaining to important factors causing indoor air pollution such as cooking fuel other than liquid petroleum gas (LPG) and passive smoking were collected along with potential socio-demographic factors and nutrition in both groups and analysed.

RESULTS

A total of 202 children including 101 cases and 101 controls were studied. The proportions of infants (1-12 months) among cases and controls were 62.4% and 71.3%, respectively. Of those with ALRTI, 24.8% had pneumonia, 45.5% had severe pneumonia and 29.7% had very severe disease. Exposure to passive smoking was not associated with ALRTI. Cooking fuel other than LPG was significantly associated with ALRTI (OR 26.3, 95% CI 10.5-65.7). On logistic regression analysis of multiple risk factors, cooking fuel other than LPG emerged as a significant risk factor for developing ALRTI (adjusted OR 4.73, 95% CI 1.67-13.45) along with poor socio-economic status (adjusted OR 3.38, 95% CI 1.63-7.03). Other than LPG, the main fuels used were wood (95%), kerosene and dung and crop residues.

CONCLUSION

Indoor air pollution caused by using cooking fuel other than LPG and socio-economic factors are significantly associated with ALRTI.

Improved siRNA/shRNA functionality by mismatched duplex

siRNA (small interfering RNA) and shRNA (small hairpin RNA) are powerful and commonly used tools in biomedical research. Currently, siRNAs are generally designed as two 21 nt strands of RNA that include a 19 nt completely complementary part and a 2 nt overhang. However, since the si/shRNAs use the endogenous miRNA machinery for gene silencing and the miRNAs are generally 22 nt in length and contain multiple internal mismatches, we tested if the functionality can be increased by designing the si/shRNAs to mimic a miRNA structure. We systematically investigated the effect of single or multiple mismatches introduced in the passenger strand at different positions on siRNA functionality. Mismatches at certain positions could significantly increase the functionality of siRNAs and also, in some cases decreased the unwanted passenger strand functionality. The same strategy could also be used to design shRNAs. Finally, we showed that both si and miRNA structured oligos (siRNA with or without mismatches in the passenger strand) can repress targets in all individual Ago containing cells, suggesting that the Ago proteins do not differentiate between si/miRNA-based structure for silencing activity.

Ago-2-mediated slicer activity is essential for anti-flaviviral efficacy of RNAi

RNA interference can be mediated by fully complementary siRNA or partially complementary miRNA. siRNAs are widely used to suppress viral replication and the fully complementary siRNA bound Ago-2 in the RISC is known to degrade the target RNA. Although other argonaute proteins lacking slicer activity can also bind oligonucleotides with both si and miRNA structures, whether they can also contribute to antiviral effects is not entirely clear. We tested si and miRNA structured oligos for target repression in dual luciferase assays as well as for inhibition of Dengue and West Nile virus replication in ES cells expressing individual Ago proteins. In luciferase assays, both fully complementary and partially complementary oligos effectively repressed their targets in all individual Ago expressing cell lines, although the efficacy with fully complementary oligos was higher in Ago-2+ cells. However, partially complementary oligos had no effect on virus replication in any cell line, while fully complementary siRNAs were highly effective in Ago-2 expressing, but not in cells expressing other Ago proteins. This occurred irrespective of whether the target sequences were located in the coding region or 3'UTR of the virus. We conclude that Ago-2 slicer activity is essential for anti-viral efficacy of siRNAs and miRNA-mediated translational repression/transcript destabilization is too weak to suppress the abundantly expressed flaviviral proteins.

Targeting the HIV entry, assembly and release pathways for anti-HIV gene therapy

Targeting the HIV entry and assembly pathways holds promise for development of novel anti-HIV gene therapy vectors. We characterized discrete dominant negative (DN) Gag and Envelope mutants for their anti-HIV-1 activity. We show here that capsid mutants (Q155N and Y164A) are more potent inhibitors of WT HIV than the matrix mutant 1GA. Both the Envelope mutants tested, V513E and R515A, were equally effective and a combination of Gag and Envelope DN genes significantly enhanced potency. Interestingly, the DN mutants acted at multiple steps in the virus life cycle rather than solely disrupting virus release or infection. Inhibition mediated by R515A could be partially attributed to the Envelope cytoplasmic tail, as deletion of R515A tail partially abrogated its DN effect. Finally, the Y164A/R515A double mutant expressed in a lentiviral vector was effective at inhibiting HIV replication in CD34+ hematopoietic stem cell-derived macrophages, demonstrating the therapeutic potential of our approach.

Anaesthetic management of closed mitral valvotomy for severe mitral stenosis with traumatic kyphoscoliosis

A 42-year-old male patient with rheumatic mitral stenosis was posted for percutaneous transluminal mitral commissurotomy. He had associated traumatic kyphoscoliosis and osteoarthritis of hip and knee joints, causing severe permanent flexion of these joints. This position caused technical difficulty in approach to the femoral vessels. So he was rescheduled for closed mitral valvotomy. This also posed similar problems, but was successfully managed.

Advances in synthetic siRNA delivery

The application of RNA interference-based gene silencing technologies has the potential to treat a variety of illness. Preclinical studies and some early clinical trials have already demonstrated the utility of small interfering RNAs (siRNAs) as a potential novel therapy for the treatment of cancer, viral infections, as well as a wide range of additional diseases. To be effective, an siRNA must be taken up by specific cells, enter the cytoplasm, and be loaded onto the Argonaute protein, the catalytic core of the RNA induced silencing complex (RISC) to direct the cleavage of the homologous transcripts. To meet this need, a variety of novel siRNA delivery strategies have been developed. As our understanding of the molecular mechanisms underlying the RNAi pathway has increased so has the ability to rationally design effective silencing and delivery strategies. This review will examine the latest advances in non-viral delivery of siRNA, with special reference to targeted siRNA delivery to specific target tissues and cell types in vivo in preclinical animal models.

Targeted delivery of siRNA to macrophages for anti-inflammatory treatment

Inflammation mediated by tumor necrosis factor-alpha (TNF-alpha) and the associated neuronal apoptosis characterizes a number of neurologic disorders. Macrophages and microglial cells are believed to be the major source of TNF-alpha in the central nervous system (CNS). Here, we show that suppression of TNF-alpha by targeted delivery of small interfering RNA (siRNA) to macrophage/microglial cells dramatically reduces lipopolysaccharide (LPS)-induced neuroinflammation and neuronal apoptosis in vivo. Because macrophage/microglia express the nicotinic acetylcholine receptor (AchR) on their surface, we used a short AchR-binding peptide derived from the rabies virus glycoprotein (RVG) as a targeting ligand. This peptide was fused to nona-D-arginine residues (RVG-9dR) to enable siRNA binding. RVG-9dR was able to deliver siRNA to induce gene silencing in macrophages and microglia cells from wild type, but not AchR-deficient mice, confirming targeting specificity. Treatment with anti-TNF-alpha siRNA complexed to RVG-9dR achieved efficient silencing of LPS-induced TNF-alpha production by primary macrophages and microglia cells in vitro. Moreover, intravenous injection with RVG-9dR-complexed siRNA in mice reduced the LPS-induced TNF-alpha levels in blood as well as in the brain, leading to a significant reduction in neuronal apoptosis. These results demonstrate that RVG-9dR provides a tool for siRNA delivery to macrophages and microglia and that suppression of TNF-alpha can potentially be used to suppress neuroinflammation in vivo.

RNA interference-based therapeutics for human immunodeficiency virus HIV-1 treatment: synthetic siRNA or vector-based shRNA?

IMPORTANCE OF THE FIELD

Despite the clinical benefits of highly active antiretroviral therapy (HAART), the prospect of life-long antiretroviral treatment poses significant problems, which has spurred interest in developing new drugs and strategies to treat HIV infection and eliminate persistent viral reservoirs. RNAi has emerged as a therapeutic possibility for HIV.

AREAS COVERED IN THIS REVIEW

We discuss progress in overcoming hurdles to translating transient and stable RNAi enabling technologies to clinical application for HIV; covering the past 2 - 3 years.

WHAT THE READER WILL GAIN

HIV inhibition can be achieved by transfection of chemically or enzymatically synthesized siRNAs or by DNA-based vector systems expressing short hairpin RNAs (shRNAs) that are processed intracellularly into siRNA. We compare these approaches, focusing on technical and safety issues that will guide the choice of strategy for clinical use.

TAKE HOME MESSAGE

Introduction of synthetic siRNA into cells or its stable endogenous production using vector-driven shRNA have been shown to suppress HIV replication in vitro and, in some instances, in vivo. Each method has advantages and limitations in terms of ease of delivery, duration of silencing, emergence of escape mutants and potential toxicity. Both appear to have potential as future therapeutics for HIV, once the technical and safety issues of each approach are overcome.

Alternative processing of primary microRNA transcripts by Drosha generates 5' end variation of mature microRNA

BACKGROUND

It is generally believed that the miRNA processing machinery ensures the generation of a mature miRNA with a fixed sequence, particularly at its 5' end. However, we and others have recently noted that the ends of a given mature miRNA are not absolutely fixed, but subject to variation. Neither the significance nor the mechanism behind the generation of such miRNA polymorphism is understood. miR-142 is an abundantly expressed miRNA in hematopoietic cells and exhibits a high frequency of 5' end polymorphism.

METHODOLOGY/PRINCIPAL FINDINGS

Here we show that a shift in the Drosha processing of pri-miRNA generates multiple forms of miR-142s in vivo with differing 5' ends that might target different genes. Sequence analysis of several pre-miRNA ends cloned from T cells reveals that unlike many other pri-miRNAs that are processed into a single pre-miRNA, pri-miR-142 is processed into 3 distinct pre-miR-142s. Dicer processing studies suggest that each of the 3 pre-miR-142s is processed into a distinct double-stranded miRNA, giving rise to 4 mature miRNA variants that might regulate different target gene pools.

CONCLUSIONS/SIGNIFICANCE

Thus, alternative Drosha processing might be a novel mechanism for diversification of the miRNA target gene pool.

Lentiviral delivery of short hairpin RNAs

In less than a decade after discovery, RNA interference-mediated gene silencing is already being tested as potential therapy in clinical trials for a number of diseases. Lentiviral vectors provide a means to express short hairpin RNA (shRNA) to induce stable and long-term gene silencing in both dividing and non-dividing cells and thus, are being intensively investigated for this purpose. However, induction of long-term shRNA expression can also cause toxicities by inducing off-target effects and interference with the endogenous micro-RNA (miRNA) pathway that regulates cellular gene expression. Recently, several advances have been made in the shRNA vector design to mimic cellular miRNA processing and to express multiplex siRNAs in a tightly regulated and reversible manner to overcome toxicities. In this review we describe some of these advances, focusing on the progress made in the development of lentiviral shRNA delivery strategies to combat viral infections.

Blocking CD27-CD70 costimulatory pathway suppresses experimental colitis

The pathogenesis of human inflammatory bowel disease (IBD) and most experimental models of IBD is dependent on the activation and expansion of CD4(+) T cells via interaction with mucosal APCs. The costimulatory receptor CD70 is transiently expressed on the surface of conventional dendritic cells, but is constitutively expressed by a unique APC population in the intestinal lamina propria. We used two experimental IBD models to evaluate whether interfering the interaction between CD70 and its T cell ligand CD27 would affect the development of colitis. Adoptive transfer of naive CD27-deficient CD45RB(high) CD4(+) T cells into Rag-1(-/-) mice resulted in significantly less disease than when wild-type CD45RB(high)CD4(+) T cells were used. Moreover, a monoclonal anti-CD70 Ab prevented the disease caused by the transfer of wild-type CD45RB(high) CD4(+) T cells into Rag-1(-/-) mice and the same Ab also ameliorated an established disease. The colitis associated proinflammatory cytokines IL-6, TNF-alpha and IFN-gamma were significantly reduced after anti-CD70 Ab treatment, suggesting an overall reduction in inflammation due to blockade of pathogenic T cell expansion. Anti-CD70 Ab treatment also suppressed trinitrobenzene sulfonic acid-induced colitis in SJL/J mice. Because anti-CD70 Ab treatment suppressed multiple proinflammatory cytokines, this may be a more potent therapeutic approach for IBD than blockade of individual cytokines.

Imatinib mesylate experience of young patients with chronic myeloid leukemia in chronic phase—Care to cure

7072

Background: Chronic myeloid leukemia (CML) with introduction of imatinib has been transformed into a chronic illness. The options of treatment in a patient less than 35 years include imatinib or allogenic stem cell transplantation. Hence we studied this unique subset to look at the response rates, adverse effects, progression free survival, and overall survival with imatinib mesylate. Methods: 477 patients with Philadelphia positive CML in chronic phase were retrospectively analyzed from January 2002 to December 2007 at Cancer Institute (WIA), Chennai, India. Standard criteria were used for response evaluation and adverse effects. Results: A total of 248 young CML patients with age less than 35 years (51.9%) were diagnosed in chronic phase. The median age of study population was 27 years (4–35). The male to female ratio was 1.9: 1. Risk stratification was done using Sokal index and were classified into low (32.3%), intermediate (50.4%), and high (17.3%). All patients received imatinib 400 mg as the initial dose. Complete hematological remission (CHR) was seen in 96.7%.Cytogenetic (FISH) and molecular (RTPCR) monitoring was possible in 53.2% and 17.3%, respectively. 72% of the patients had major cytogenetic response. Major molecular response was seen in 34.8% while complete molecular response occurred in 23.2% of the patients. Primary and secondary imatinib failure was seen in 3.1% and 16.9%, respectively. 6.7% had grade 3 and grade 4 hematological toxicities. The other common non hematological toxicities included pedal edema (13.7%), hypo or hyper pigmentation (60.0%), hyalgia (14.5%), diarrhea (1.6%), and liver dysfunction (1.6%). None of the patients discontinued imatinib due to toxicities. The 3-year DFS and OS was 86.2% and 89.5%, respectively. Patients with male sex (p = 0.04), spleen > 8 cm (p = 0.02), high sokal index (p = 0.02), and loss of CHR (p < 0.001) were associated with poor outcome. Conclusions: Imatinib in young patients have an excellent tolerance and response. A small subset does not respond to therapy or develop resistance during treatment. Hence it is essential to identify these poor responders and to offer stem cell transplantation at the earliest.

No significant financial relationships to disclose.

Concurrent generation of effector and central memory CD8 T cells during vaccinia virus infection

It is generally thought that during the contraction phase of an acute anti-viral T cell reponse, the effector T cells that escape activation-induced cell death eventually differentiate into central memory T cells over the next several weeks. Here we report that antigen-specific CD8T cells with the phenotype and function of central memory cells develop concomitantly with effector T cells during vaccinia virus (vv) infection. As soon as 5 days after an intraperitoneal infection with vv, we could identify a subset of CD44^hi and CD62L⁺ vv-specific CD8 T cells in the peritoneal exudate lymphocytes. This population constituted approximately 10% of all antigen-specific T cells and like central memory T cells, they also expressed high levels of CCR7 and IL-7R but expressed little granzyme B. Importantly, upon adoptive transfer into naïve congenic hosts, CD62L⁺, but not CD62L⁻ CD8 T cells were able to expand and mediate a rapid recall response to a new vv challenge initiated 6 weeks after transfer, confirming that the CD62L⁺ vv-specific CD8 T cells are bonafide memory cells. Our results are thus consistent with the branched differentiation model, where effector and memory cells develop simultaneously. These results are likely to have implications in the context of vaccine design, particularly those based on vaccinia virus recombinants.

T cell-specific siRNA delivery suppresses HIV-1 infection in humanized mice

Evaluation of the therapeutic potential of RNAi for HIV infection has been hampered by the challenges of siRNA delivery and lack of suitable animal models. Using a delivery method for T cells, we show that siRNA treatment can dramatically suppress HIV infection. A CD7-specific single-chain antibody was conjugated to oligo-9-arginine peptide (scFvCD7-9R) for T cell-specific siRNA delivery in NOD/SCIDIL2rgamma-/- mice reconstituted with human lymphocytes (Hu-PBL) or CD34+ hematopoietic stem cells (Hu-HSC). In HIV-infected Hu-PBL mice, treatment with anti-CCR5 (viral coreceptor) and antiviral siRNAs complexed to scFvCD7-9R controlled viral replication and prevented the disease-associated CD4 T cell loss. This treatment also suppressed endogenous virus and restored CD4 T cell counts in mice reconstituted with HIV+ peripheral blood mononuclear cells. Moreover, scFvCD7-9R could deliver antiviral siRNAs to naive T cells in Hu-HSC mice and effectively suppress viremia in infected mice. Thus, siRNA therapy for HIV infection appears to be feasible in a preclinical animal model.

miRNA profiling of naïve, effector and memory CD8 T cells

microRNAs have recently emerged as master regulators of gene expression during development and cell differentiation. Although profound changes in gene expression also occur during antigen-induced T cell differentiation, the role of miRNAs in the process is not known. We compared the miRNA expression profiles between antigen-specific naïve, effector and memory CD8+ T cells using 3 different methods-small RNA cloning, miRNA microarray analysis and real-time PCR. Although many miRNAs were expressed in all the T cell subsets, the frequency of 7 miRNAs (miR-16, miR-21, miR-142-3p, miR-142-5p, miR-150, miR-15b and let-7f) alone accounted for ∼60% of all miRNAs, and their expression was several fold higher than the other expressed miRNAs. Global downregulation of miRNAs (including 6/7 dominantly expressed miRNAs) was observed in effector T cells compared to naïve cells and the miRNA expression levels tended to come back up in memory T cells. However, a few miRNAs, notably miR-21 were higher in effector and memory T cells compared to naïve T cells. These results suggest that concomitant with profound changes in gene expression, miRNA profile also changes dynamically during T cell differentiation. Sequence analysis of the cloned mature miRNAs revealed an extensive degree of end polymorphism. While 3′end polymorphisms dominated, heterogeneity at both ends, resembling drosha/dicer processing shift was also seen in miR-142, suggesting a possible novel mechanism to generate new miRNA and/or to diversify miRNA target selection. Overall, our results suggest that dynamic changes in the expression of miRNAs may be important for the regulation of gene expression during antigen-induced T cell differentiation. Our study also suggests possible novel mechanisms for miRNA biogenesis and function.

Impaired immune response to vaccinia virus inoculated at the site of cutaneous allergic inflammation

BACKGROUND

Patients with atopic dermatitis (AD) exposed to the vaccinia virus (VV) smallpox vaccine have an increased risk of developing eczema vaccinatum.

OBJECTIVE

To investigate the effects of local allergic skin inflammation on vaccinia immunity.

METHODS

BALB/c mice were epicutaneously sensitized with ovalbumin (OVA) to induce allergic skin inflammation or with saline control, then inoculated with an attenuated VV strain by skin scarification or intraperitoneally. After 8 days, serum IgG anti-VV and cytokine secretion by splenocytes were measured.

RESULTS

Mice inoculated with VV at sites of epicutaneous sensitization with OVA, but not control mice inoculated at saline exposed sites, developed satellite pox lesions and had impaired secretion of T(H)1 cytokines in response to VV, decreased VV specific serum IgG(2a), increased VV specific serum IgG(1), and impaired upregulation of IFN-alpha, but not the cathelicidin-related antimicrobial peptide, at the infection site. The VV immune response of OVA-sensitized mice inoculated with VV at distant skin sites or intraperitoneally was normal.

CONCLUSION

Local immune dysregulation at sites of allergic skin inflammation underlies the impaired T(H)1 immune response to VV introduced at these sites and the increased susceptibility to develop satellite pox lesions, a characteristic of eczema vaccinatum in patients with AD.

CLINICAL IMPLICATIONS

In a mouse model of AD, inoculation of VV at inflamed skin sites is associated with increased numbers of satellite pox lesions and an abnormal immune response to the virus. This may contribute to the susceptibility of patients with AD to virus dissemination after smallpox vaccination.

Transvascular delivery of small interfering RNA to the central nervous system

A major impediment in the treatment of neurological diseases is the presence of the blood-brain barrier, which precludes the entry of therapeutic molecules from blood to brain. Here we show that a short peptide derived from rabies virus glycoprotein (RVG) enables the transvascular delivery of small interfering RNA (siRNA) to the brain. This 29-amino-acid peptide specifically binds to the acetylcholine receptor expressed by neuronal cells. To enable siRNA binding, a chimaeric peptide was synthesized by adding nonamer arginine residues at the carboxy terminus of RVG. This RVG-9R peptide was able to bind and transduce siRNA to neuronal cells in vitro, resulting in efficient gene silencing. After intravenous injection into mice, RVG-9R delivered siRNA to the neuronal cells, resulting in specific gene silencing within the brain. Furthermore, intravenous treatment with RVG-9R-bound antiviral siRNA afforded robust protection against fatal viral encephalitis in mice. Repeated administration of RVG-9R-bound siRNA did not induce inflammatory cytokines or anti-peptide antibodies. Thus, RVG-9R provides a safe and noninvasive approach for the delivery of siRNA and potentially other therapeutic molecules across the blood-brain barrier.

Cutting Edge: Distinct NK receptor profiles are imprinted on CD8 T cells in the mucosa and periphery during the same antigen challenge: role of tissue-specific factors

NK cell receptors (NKRs) modulate T lymphocyte responses by modifying the Ag activation threshold. However, what governs their expression on T cells remains unclear. In this study we show that different NKRs are imprinted on CD8 T cells in the gut mucosa and periphery during the same Ag challenge. After a viral, bacterial, and tumor challenge, most CD8 peritoneal exudate lymphocytes expressed NKG2A but not 2B4. In contrast, most CD8 intraepithelial lymphocytes exhibited 2B4 but not NKG2A. Our data suggest that tissue-specific factors may determine the pattern of NKR expression. In the gut, CD70 licensing appears to promote 2B4 induction on mucosal CD8 T cells. Conversely, retinoic acid produced by the intestinal dendritic cells may suppress NKG2A expression. Thus, tissue-specific factors regulate NKR expression and may confer T cells with differing effector functions in a tissue and site-specific manner.

Interfering antiviral immunity: application, subversion, hope?

RNA interference (RNAi), initially recognized as a natural antiviral mechanism in plants, has rapidly emerged as an invaluable tool to suppress gene expression in a sequence-specific manner in all organisms, including mammals. Its potential to inhibit the replication of a variety of viruses has been demonstrated in vitro and in vivo in mouse and monkey models. These results have generated profound interest in the use of this technology as a potential treatment strategy for viral infections for which vaccines and drugs are unavailable or inadequate. In this review, we discuss the progress made within the past 2–3 years towards harnessing the potential of RNAi for clinical application in viral infections and the hurdles that have yet to be overcome.

A single siRNA suppresses fatal encephalitis induced by two different flaviviruses

BACKGROUND

Japanese encephalitis virus (JEV) and West Nile virus (WNV) are neurotropic flaviviruses that can cause acute encephalitis with a high fatality rate. Currently there is no effective treatment for these infections.

METHODS AND FINDINGS

We tested RNA interference (RNAi)-based intervention to suppress lethal JE and WN encephalitis in mice. To induce RNAi, we used either lentivirally expressed short hairpin RNA (shRNA) or synthetic short interfering RNA (siRNA). As target, we selected the cd loop-coding sequence in domain II of the viral Envelope protein, which is highly conserved among all flaviviruses because of its essential role in membrane fusion. Using as a target a species-specific sequence in the cd loop that is conserved only among the different strains of either JEV or WNV, we could achieve specific protection against the corresponding virus. However, by targeting a cross-species conserved sequence within the cd loop, we were able to protect mice against encephalitis induced by both viruses. A single intracranial administration of lentivirally delivered shRNA or lipid-complexed siRNA before viral challenge or siRNA treatment after viral challenge was sufficient for protection against lethal encephalitis.

CONCLUSIONS

RNAi-based intervention affords near complete protection from both JEV- and WNV- induced encephalitis in mice. Our results show, to our knowledge for the first time, that siRNA can be used as a broad-spectrum antiviral agent for treating encephalitis caused by multiple related viruses.