Cutting Edge: Oseltamivir decreases T cell GM1 expression and inhibits clearance of respiratory syncytial virus: potential role of endogenous sialidase in antiviral immunity

Cell Membrane Sialome: Sialic Acids as Therapeutic Targets and Regulators of Drug Resistance in Human Cancer Management

A cellular sialome is a physiologically active and dynamically changing component of the cell membrane. Sialylation plays a crucial role in tumor progression, and alterations in cellular sialylation patterns have been described as modulators of chemotherapy effectiveness. However, the precise mechanisms through which altered sialylation contributes to drug resistance in cancer are not yet fully understood. This review focuses on the intricate interplay between sialylation and cancer treatment. It presents the role of sialic acids in modulating cell-cell interactions, the extracellular matrix (ECM), and the immunosuppressive processes within the context of cancer. The issue of drug resistance is also discussed, and the mechanisms that involve transporters, the tumor microenvironment, and metabolism are analyzed. The review explores drugs and therapeutic approaches that may induce modifications in sialylation processes with a primary focus on their impact on sialyltransferases or sialidases. Despite advancements in cellular glycobiology and glycoengineering, an interdisciplinary effort is required to decipher and comprehend the biological characteristics and consequences of altered sialylation. Additionally, understanding the modulatory role of sialoglycans in drug sensitivity is crucial to applying this knowledge in clinical practice for the benefit of cancer patients.

Lipid rafts as viral entry routes and immune platforms: A double-edged sword in SARS-CoV-2 infection?

Lipid rafts are nanoscopic compartments of cell membranes that serve a variety of biological functions. They play a crucial role in viral infections, as enveloped viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can exploit rafts to enter or quit target cells. On the other hand, lipid rafts contribute to the formation of immune synapses and their proper functioning is a prerequisite for adequate immune response and viral clearance. In this narrative review we dissect the panorama focusing on this singular aspect of cell biology in the context of SARS-CoV-2 infection and therapy. A lipid raft-mediated mechanism can be hypothesized for many drugs recommended or considered for the treatment of SARS-CoV-2 infection, such as glucocorticoids, antimalarials, immunosuppressants and antiviral agents. Furthermore, the additional use of lipid-lowering agents, like statins, may affect the lipid composition of membrane rafts and thus influence the processes occurring in these compartments. The combination of drugs acting on lipid rafts may be successful in the treatment of more severe forms of the disease and should be reserved for further investigation.

Oseltamivir as rescue therapy for persistent, chronic, or refractory immune thrombocytopenia: a case series and review of the literature

Immune thrombocytopenia (ITP) is an autoimmune disease that results from antibody-mediated platelet destruction and impaired platelet production. Novel therapies have emerged in the last decade, but 15-20% of patients will relapse or fail and require further therapy. We performed a prospective, single-arm intervention study on seven patients with chronic, persistent, or refractory ITP from the Hospital Universitario "Dr. José E González", in Monterrey, Mexico between 2015 and 2019. Eligible patients received oral oseltamivir 75 mg twice daily for 5 days and were followed up for six months. Most patients received a median of three distinct therapies (range 2-6). Four patients (57.1%) received combined therapy. The median time for any response was 55.5 days (range = 14-150). All patients responded at some point in time (ORR = 100%, six had a proportion of loss of response [PR], and one achieved [CR]). Six months after oseltamivir administration, three patients (42.9%) maintained a response, and one patient had a CR (14.3%). Oseltamivir was well tolerated with a good overall response rate and was useful for treating chronic ITP. We observed an initial increase in the number of platelets; however, this response was not maintained.

Effect of oseltamivir phosphate versus placebo on platelet recovery and plasma leakage in adults with dengue and thrombocytopenia; a phase 2, multicenter, double-blind, randomized trial

Background

Thrombocytopenia, bleeding and plasma leakage are major complications of dengue. Activation of endogenous sialidases with desialylation of platelets and endothelial cells may underlie these complications. We aimed to assess the effects of the neuraminidase inhibitor oseltamivir on platelet recovery and plasma leakage in dengue.

Methods

We performed a phase 2, double-blind, multicenter, randomized trial in adult dengue patients with thrombocytopenia (<70,000/μl) and a duration of illness ≤ 6 days. Oseltamivir phosphate 75mg BID or placebo were given for a maximum of five days. Primary outcomes were the time to platelet recovery (≥ 100,000/μl) or discharge from hospital and the course of measures of plasma leakage.

Results

A total of 70 patients were enrolled; the primary outcome could be assessed in 64 patients (31 oseltamivir; 33 placebo). Time to platelet count ≥100,000/μl (n = 55) or discharge (n = 9) were similar in the oseltamivir and placebo group (3.0 days [95% confidence interval, 2.7 to 3.3] vs. 2.9 days [2.5 to 3.3], P = 0.055). The kinetics of platelet count and parameters of plasma leakage (gall bladder thickness, hematocrit, plasma albumin, syndecan-1) were also similar between the groups.

Discussion

In this trial, adjunctive therapy with oseltamivir phosphate had no effect on platelet recovery or plasma leakage parameters.

Trial registration

ISRCTN35227717.

Moderate to severe thrombocytopenia is common in the febrile and/or critical phase of dengue virus infection. Platelets are important for preservation of vascular integrity, especially during inflammation, and low platelet counts may contribute to plasma leakage. Currently, no therapeutic intervention that targets the pathogenic pathway is available for DENV infection, including therapies to prevent or reduce thrombocytopenia or plasma leakage. Oseltamivir phosphate is widely used for prevention and treatment of influenza by inhibiting viral neuraminidase. However, oseltamivir may also inhibit human endogenous neuraminidase involved in sialic acid metabolism, and as such extend the lifespan of platelets. In the phase 2 TOTO trial (Treatment Of Thrombocytopenia with Oseltamivir in acute dengue virus infection: a randomized, placebo controlled, multicenter trial) we investigated the potential of oseltamivir phosphate to shorten the time to platelet recovery and reduce plasma leakage in patients with DENV infection. In this trial involving 70 adult thrombocytopenic patients, hospitalized with acute DENV infection, adjunctive therapy with oseltamivir phosphate did not shorten platelet recovery time compared with placebo. The trial also did not show an effect of adjunctive oseltamivir on plasma leakage parameters. The reasons that oseltamivir had no apparent effect on platelet counts, markers of plasma leakage and glycocalyx distortion in this study remain speculative, but may involve one or more of the following; first, dengue-associated thrombocytopenia and plasma leakage are both multifactorial in origin and targeting neuraminidase alone may be insufficient to impact these processes. Second, oseltamivir phosphate was designed to inhibit viral neuraminidase, and data of its inhibitory actions on human neuraminidases are inconclusive. The finding in this study also suggest that while laboratory works may lead to hypotheses for novel treatment, proof of concept studies are essential to test them in a clinical setting.

All-cause mortality among patients treated with repurposed antivirals and antibiotics for COVID-19 in Mexico City: A real-world observational study

The aim of our study was to evaluate all-cause mortality risk in patients with laboratory-confirmed COVID-19 in Mexico City treated with repurposed antivirals and antibiotics. This real-world retrospective cohort study contemplated 395,343 patients evaluated for suspected COVID-19 between February 24 and September 14, 2020 in 688 primary-to-tertiary medical units in Mexico City. Patients were included with a positive RT-PCR for SARS-CoV-2; those receiving unspecified antivirals, excluded; and groups of antivirals prescribed in < 30 patients, eliminated. Survival and mortality risks were determined for patients receiving antivirals, antibiotics, both, or none. We assessed the effect of early (<2 days) versus late (>2 days) use of antivirals on mortality in a sub-cohort of patients. Multivariable adjustment, propensity score matching, generalized estimating equations, and calculation of E-values were performed to limit confounding. 136,855 patients were analyzed; mean age 44.2 (SD:16.8) years; 51.3 % were men. 16.6 % received antivirals (3 %), antibiotics (10 %), or both (3.6 %). Antivirals studied were Oseltamivir (n=8414), Amantadine (n=319), Lopinavir-Ritonavir (n=100), Rimantadine (n=61), Zanamivir (n=39), and Acyclovir (n=36). Survival with antivirals (73.7 %, p<0.0001) and antibiotics (85.8 %, p<0.0001) was lower than no antiviral/antibiotic (93.6 %). After multivariable adjustment, increased risk of death occurred with antivirals (HR=1.72, 95 % CI: 1.61-1.84) in ambulatory (HR=4.7, 95 % CI: 3.94-5.62) and non-critical (HR=2.03, 95 % CI: 1.86-2.21) patients. Oseltamivir increased mortality risk in the general population (HR=1.72, 95 % CI: 1.61-1.84), ambulatory (HR=4.79, 95 % CI: 4.01-5.75), non-critical (HR=2.05, 95 % CI: 1.88-2.23), and pregnancy (HR=8.35, 95 % CI: 1.77-39.30); as well as hospitalized (HR=1.13, 95 % CI: 1.01-1.26) and critical patients (HR=1.22, 95 % CI: 1.05-1.43) after propensity score-matching. Early versus late oseltamivir did not modify the risk. Antibiotics were a risk factor in general population (HR=1.13, 95 % CI: 1.08-1.19) and pediatrics (HR=4.22, 95 % CI: 2.01-8.86), but a protective factor in hospitalized (HR=0.81, 95 % CI: 0.77-0.86) and critical patients (HR=0.67, 95 % CI: 0.63-0.72). No significant benefit for repurposed antivirals was observed; oseltamivir was associated with increased mortality. Antibiotics increased mortality risk in the general population but may increase survival in hospitalized and critical patients.

The role of brain innate immune response in lysosomal storage disorders: fundamental process or evolutionary side effect?

Sphingolipidoses are diseases caused by mutations in genes responsible for sphingolipid degradation and thereby lead to sphingolipid accumulation. Most sphingolipidoses have a neurodegenerative manifestation characterized by innate immune activation in the brain. However, the role of the immune response in disease progression is ill-understood. In contrast to infectious diseases, immune activation is unable to eliminate the offending agent in sphingolipidoses resulting in ineffective, chronic inflammation. This paradox begs two fundamental questions: Why has this immune response evolved in sphingolipidoses? What role does it play in disease progression? Here, starting from the observation that sphingolipids (SLs) are elevated also in infectious diseases, I discuss the possibility that the activation of the brain immune response by SLs has evolved as a part of the immune response against pathogens and plays no major role in sphingolipidoses.

Targeting glycosphingolipid metabolism as a potential therapeutic approach for treating disease in female MRL/lpr lupus mice

Glycosphingolipids (GSLs) hexosylceramides and lactosylceramides are elevated in lupus mice and human patients with nephritis. Whereas other renal diseases characterized by increased GSL levels are thought to be a result of upregulated GSL synthesis, our results suggest elevated hexosylceramides and lactosylceramides in lupus nephritis is a result of increased catabolism of ganglioside GM3 due to significantly increased neuraminidase (NEU) activity. Thus, we hypothesized GM3 would be decreased in lupus nephritis kidneys and blocking NEU activity would reduce GSLs and improve disease in lupus mice. Female MRL/lpr lupus mice were treated with water or the NEU inhibitor oseltamivir phosphate at the onset of proteinuria to block GSL catabolism. Age-matched (non-nephritic) female MRL/MpJ lupus mice served as controls. Renal GM3 levels were significantly higher in the nephritic MRL/lpr water-treated mice compared to non-nephritic MRL/MpJ mice, despite significantly increased renal NEU activity. Blocking GSL catabolism increased, rather than decreased, renal and urine GSL levels and disease was not significantly impacted. A pilot study treating MRL/lpr females with GlcCer synthase inhibitor Genz-667161 to block GSL synthesis resulted in a strong significant negative correlation between Genz-667161 dose and renal GSL hexosylceramide and GM3 levels. Splenomegaly was negatively correlated and serum IgG levels were marginally correlated with increasing Genz-667161 dose. These results suggest accumulation of renal GM3 may be due to dysregulation of one or more of the GSL ganglioside pathways and inhibiting GSL synthesis, but not catabolism, may be a therapeutic approach for treating lupus nephritis.

Evaluating the effects of oseltamivir phosphate on platelet counts: a retrospective review

Desialylation of platelets results in platelet clearance by the Ashwell-Morrell Receptors (AMR) found on hepatocytes. Studies suggest that oseltamivir phosphate inhibits human sialidases, enzymes responsible for desialylation, extending the lifespan of circulating platelets. We thus evaluated, the effects of oseltamivir on platelet count (PC) following treatment. Of the 385 patients evaluated for influenza, 283 (73.5%) were influenza-infected. Of the 283 infected patients, 241 (85.2%) received oseltamivir (I + O+) while 42 patients did not (I + O-). One hundred two non-infected patients received oseltamivir (I-O+). The two groups receiving oseltamivir (I + O+, I-O+), demonstrated a statistically greater increase in the PC (57.53 ± 93.81, p = .013 and 50.79 ± 70.59, p = .023, respectively) relative to the group that did not (18.45 ± 89.33 × 10⁹/L). The observed increase in PC was statistically similar (p = .61) in both groups receiving oseltamivir (I + O+, I-O+), suggesting that this effect is independent of influenza. Comparing clinical characteristics between responders and non-responders to oseltamivir treatment showed that only duration of oseltamivir treatment (AOR = 1.30, 95% CI 1.05-1.61, p = .015) was associated with a positive PC response. Our findings suggest a correlation between oseltamivir treatment and an increase in PCs. Future studies assessing the possible uses of oseltamivir in medical conditions characterized by diminished or defective thrombopoiesis are warranted.

Glycosphingolipids and Infection. Potential New Therapeutic Avenues

Glycosphingolipids (GSLs), the main topic of this review, are a subclass of sphingolipids. With their glycans exposed to the extracellular space, glycosphingolipids are ubiquitous components of the plasma membrane of cells. GSLs are implicated in a variety of biological processes including specific infections. Several pathogens use GSLs at the surface of host cells as binding receptors. In addition, lipid-rafts in the plasma membrane of host cells may act as platform for signaling the presence of pathogens. Relatively common in man are inherited deficiencies in lysosomal glycosidases involved in the turnover of GSLs. The associated storage disorders (glycosphingolipidoses) show lysosomal accumulation of substrate(s) of the deficient enzyme. In recent years compounds have been identified that allow modulation of GSLs levels in cells. Some of these agents are well tolerated and already used to treat lysosomal glycosphingolipidoses. This review summarizes present knowledge on the role of GSLs in infection and subsequent immune response. It concludes with the thought to apply glycosphingolipid-lowering agents to prevent and/or combat infections.

Multirefractory primary immune thrombocytopenia; targeting the decreased sialic acid content

Patients with multirefractory immune thrombocytopenia (ITP) have limited treatment options. Recent data suggest that specific anti-platelet antibodies may cause destruction of platelets by favoring platelet loss of sialic acid. In this multicenter study 35 patients with ITP, including 16 with multirefractory disease, were analyzed for antiplatelet-antibodies, thrombopoietin (TPO) levels, and platelet desialylation. In selected cases, responses to a novel treatment strategy using oseltamivir were tested. We found that antibodies against GPIbα were overrepresented in multirefractory patients compared to responders (n = 19). In contrast to conventional ITP patients, multirefractory patients exhibited a significant increased platelet activation state (granule secretion) and desialylation (RCA-1 binding) (p < 0.05), and a trend toward higher plasma TPO concentrations. The decreased sialic acid content seemed to be restricted to platelet glycoproteins, since other plasma proteins were not hypoglycosylated. A total of 10 patients with multirefractory ITP having remarkable loss of platelet terminal sialic acids were given oseltamivir phosphate. When the antiviral drug was combined with TPO receptor agonists (TPO-RAs) or with immunosuppressant drugs, platelet responses were observed in 66.7% of patients. All responding patients presented with antibodies reactive only against GPIbα. These findings suggest that desialylation may play a key pathogenic role in some multirefractory ITP patients, and provide diagnostic tools for the identification of such patients. Furthermore, we show that sialidase inhibitor treatment in combination with therapies that help to increase platelet production can induce sustained platelet responses in some patients with anti-GPIbα -mediated thrombocytopenia that have failed previous therapies.

Neuraminidase activity mediates IL-6 production by activated lupus-prone mesangial cells

The development of nephritis is a leading cause of morbidity and mortality in lupus patients. Although the general pathophysiological progression of lupus nephritis is known, the molecular mediators and mechanisms are incompletely understood. Previously, we demonstrated that the glycosphingolipid (GSL) catabolic pathway is elevated in the kidneys of MRL/lpr lupus mice and human lupus patients with nephritis. Specifically, the activity of neuraminidase (NEU) and expression of Neu1, an enzyme in the GSL catabolic pathway is significantly increased. To better understand the role and mechanisms by which this pathway contributes to the progression of LN, we analyzed the expression and effects of NEU activity on the function of MRL/lpr lupus-prone mesangial cells (MCs). We demonstrate that NEU1 and NEU3 promote IL-6 production in MES13 MCs. Neu1 expression, NEU activity, and IL-6 production are significantly increased in stimulated primary MRL/lpr lupus-prone MCs, and blocking NEU activity inhibits IL-6 production. NEU1 and NEU3 expression overlaps IgG deposits in MCs in vitro and in renal sections from nephritic MRL/lpr mice. Together, our results suggest that NEU activity mediates IL-6 production in lupus-prone MCs possibly through an IgG-receptor complex signaling pathway.

Neuraminidase inhibitors for influenza: a systematic review and meta-analysis of regulatory and mortality data

BACKGROUND

Neuraminidase inhibitors (NIs) are stockpiled and recommended by public health agencies for treating and preventing seasonal and pandemic influenza. They are used clinically worldwide.

OBJECTIVES

To (1) describe the potential benefits and harms of NIs for influenza in all age groups by reviewing all clinical study reports (CSRs) of published and unpublished randomised, placebo-controlled trials and regulatory comments; and (2) determine the effect of oseltamivir (Tamiflu(®), Roche) treatment on mortality in patients with 2009A/H1N1 influenza.

METHODS

We searched trial registries, electronic databases and corresponded with regulators and sponsors to identify randomised trials of NIs. We requested full CSRs and accessed regulators' comments. We included only those trials for which we had CSRs. To examine the effects of oseltamivir on 2009A/H1N1 influenza mortality, we requested individual patient data (IPD) from corresponding authors of all included observational studies.

RESULTS

Effect of oseltamivir and zanamivir (Relenza®, GlaxoSmithKline) in the prevention and treatment of influenza: Oseltamivir reduced the time to first alleviation of symptoms in adults by 16.8 hours [95% confidence interval (CI) 8.4 to 25.1 hours]. Zanamivir reduced the time to first alleviation of symptoms in adults by 0.60 days (95% CI 0.39 to 0.81 days). Oseltamivir reduced unverified pneumonia in adult treatment [risk difference (RD) 1.00%, 95% CI 0.22% to 1.49%]; similar findings were observed with zanamivir prophylaxis in adults (RD 0.32%, 95% CI 0.09% to 0.41%). Oseltamivir treatment of adults increased the risk of nausea (RD 3.66%, 95% CI 0.90% to 7.39%) and vomiting (RD 4.56%, 95% CI 2.39% to 7.58%). In the treatment of children, oseltamivir induced vomiting (RD 5.34%, 95% CI 1.75% to 10.29%). Both oseltamivir and zanamivir prophylaxis reduced the risk of symptomatic influenza in individuals (oseltamivir RD 3.05%, 95% CI 1.83% to 3.88%; zanamivir RD 1.98%, 95% CI 0.98% to 2.54%) and in households (oseltamivir RD 13.6%, 95% CI 9.52% to 15.47%; zanamivir RD 14.84%, 95% CI 12.18% to 16.55%). Oseltamivir increased psychiatric adverse events in the combined on- and off-treatment periods (RD 1.06%, 95% CI 0.07% to 2.76%) and the risk of headaches while on treatment (RD 3.15%, 95% CI 0.88% to 5.78%). Effect of oseltamivir on mortality in patients with 2009A/H1N1 influenza: Analysis of summary data of 30 studies as well as IPD of four studies showed evidence of time-dependent bias. After adjusting for time-dependent bias and potential confounding variables, competing risks analysis of the IPD showed insufficient evidence that oseltamivir reduced the risk of mortality (hazard ratio 1.03, 95% CI 0.64 to 1.65).

CONCLUSIONS

Oseltamivir and zanamivir cause small reductions in the time to first alleviation of influenza symptoms in adults. The use of oseltamivir increases the risk of nausea, vomiting, psychiatric events in adults and vomiting in children. Oseltamivir has no protective effect on mortality among patients with 2009A/H1N1 influenza. Prophylaxis with either NI may reduce symptomatic influenza in individuals and in households. The balance between benefits and harms should be considered when making decisions about use of NIs for either prophylaxis or treatment of influenza.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42012002245.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Respiratory syncytial virus infection of newborn CX3CR1-deficient mice induces a pathogenic pulmonary innate immune response

Respiratory syncytial virus (RSV) infects almost all infants by 2 years of age, and severe bronchiolitis resulting from RSV infection is the primary cause of hospitalization in the first year of life. Among infants hospitalized due to RSV-induced bronchiolitis, those with a specific mutation in the chemokine receptor CX3CR1, which severely compromises binding of its ligand CX3CL1, were at a higher risk for more severe viral bronchiolitis than those without the mutation. Here, we show that RSV infection of newborn mice deficient in CX3CR1 leads to significantly greater neutrophilic inflammation in the lungs, accompanied by an increase in mucus production compared with that induced in WT mice. Analysis of innate and adaptive immune responses revealed an early increase in the number of IL-17+ γδ T cells in CX3CR1-deficient mice that outnumbered IFN-γ+ γδ T cells as well as IFN-γ+ NK cells, IFN-γ being host protective in the context of RSV infection. This bias toward IL-17+ γδ T cells persisted at a later time. The lungs of CX3CR1-deficient mice expressed higher levels of IL-1β mRNA and protein, and blockade of IL-1β signaling using IL-1 receptor antagonist significantly reduced the number of IL-17+ γδ T cells in the lungs of infected mice. Blockade of IL-17RC abolished RSV-induced lung pathology in infected CX3CR1-deficient mice. We propose that, in infants harboring mutant CX3CR1, targeting the IL-17R may minimize disease severity and hospitalization in early life.

Platelet desialylation is a novel mechanism and a therapeutic target in thrombocytopenia during sepsis: an open-label, multicenter, randomized controlled trial

BACKGROUND

Studies in murine models suggested that platelet desialylation was an important mechanism of thrombocytopenia during sepsis.

METHODS

First, we performed a prospective, multicenter, observational study that enrolled septic patients with or without thrombocytopenia to determine the association between platelet desialylation and thrombocytopenia in patients with sepsis, severe sepsis, and septic shock. Gender- and age-matched healthy adults were selected as normal controls in analysis of the platelet desialylation levels (study I). Next, we conducted an open-label randomized controlled trial (RCT) in which the patients who had severe sepsis with thrombocytopenia (platelet counts ≤50 × 10⁹/L) were randomly assigned to receive antimicrobial therapy alone (control group) or antimicrobial therapy plus oseltamivir (oseltamivir group) in a 1:1 ratio (study II). The primary outcomes were platelet desialylation level at study entry, overall platelet response rate within 14 days post-randomization, and all-cause mortality within 28 days post-randomization. Secondary outcomes included platelet recovery time, the occurrence of bleeding events, and the amount of platelets transfused within 14 days post-randomization.

RESULTS

The platelet desialylation levels increased significantly in the 127 septic patients with thrombocytopenia compared to the 134 patients without thrombocytopenia. A platelet response was achieved in 45 of the 54 patients in the oseltamivir group (83.3%) compared with 34 of the 52 patients in the control group (65.4%; P = 0.045). The median platelet recovery time was 5 days (interquartile range 4-6) in the oseltamivir group compared with 7 days (interquartile range 5-10) in the control group (P = 0.003). The amount of platelets transfused decreased significantly in the oseltamivir group compared to the control group (P = 0.044). There was no difference in the overall 28-day mortality regardless of whether oseltamivir was used. The Sequential Organ Failure Assessment score and platelet recovery time were independent indicators of oseltamivir therapy. The main reason for all of the mortalities was multiple-organ failure.

CONCLUSIONS

Thrombocytopenia was associated with increased platelet desialylation in septic patients. The addition of oseltamivir could significantly increase the platelet response rate, shorten platelet recovery time, and reduce platelet transfusion.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-IPR-16008542 .

The mechanisms of delayed onset type adverse reactions to oseltamivir

Oseltamivir is recommended for the treatment and prophylaxis of influenza in persons at higher risk for influenza complications such as individuals with diabetes, neuropsychiatric illnesses, and respiratory, cardiac, renal, hepatic or haematological diseases. However, a recent Cochrane review reported that reduction of antibody production, renal disorders, hyperglycaemia, psychiatric disorders, and QT prolongation may be related to oseltamivir use. The underlying mechanisms are reviewed. There is decisive evidence that administration of a clinically compatible dose of oseltamivir in mice challenged by a respiratory syncytial virus (RSV) that lacks a neuraminidase gene showed symptom-relieving effects and inhibition of viral clearance. These effects were accompanied by decreased level of T cell surface sialoglycosphingolipid (ganglioside) GM1 that is regulated by the endogenous neuraminidase in response to viral challenge. Clinical and non-clinical evidence supports the view that the usual dose of oseltamivir suppresses pro-inflammatory cytokines such as interferon-gamma, interleukin-6, and tumour necrosis factor-alpha almost completely with partial suppression of viral shedding in human influenza virus infection experiment. Animal toxicity tests support the clinical evidence with regard to renal and cardiac disorders (bradycardia and QT prolongation) and do not disprove the metabolic effect. Reduction of antibody production and cytokine induction and renal, metabolic, cardiac, and prolonged psychiatric disorders after oseltamivir use may be related to inhibition of the host’s endogenous neuraminidase. While the usual clinical dose of zanamivir may not have this effect, a higher dose or prolonged administration of zanamivir and other neuraminidase inhibitors may induce similar delayed reactions, including reduction of the antibody and/or cytokine production.

Anti-influenza neuraminidase inhibitor oseltamivir phosphate induces canine mammary cancer cell aggressiveness

Oseltamivir phosphate is a widely used anti-influenza sialidase inhibitor. Sialylation, governed by sialyltransferases and sialidases, is strongly implicated in the oncogenesis and progression of breast cancer. In this study we evaluated the biological behavior of canine mammary tumor cells upon oseltamivir phosphate treatment (a sialidase inhibitor) in vitro and in vivo. Our in vitro results showed that oseltamivir phosphate impairs sialidase activity leading to increased sialylation in CMA07 and CMT-U27 canine mammary cancer cells. Surprisingly, oseltamivir phosphate stimulated, CMT-U27 cell migration and invasion capacity in vitro, in a dose-dependent manner. CMT-U27 tumors xenograft of oseltamivir phosphate-treated nude mice showed increased sialylation, namely α2,6 terminal structures and SLe(x) expression. Remarkably, a trend towards increased lung metastases was observed in oseltamivir phosphate-treated nude mice. Taken together, our findings revealed that oseltamivir impairs canine mammary cancer cell sialidase activity, altering the sialylation pattern of canine mammary tumors, and leading, surprisingly, to in vitro and in vivo increased mammary tumor aggressiveness.

The administration of oseltamivir results in reduced effector and memory CD8+ T cell responses to influenza and affects protective immunity

The clinical benefits of oseltamivir (Tamiflu) are well established, but the effects of antiviral treatment on the immune response are poorly understood. By use of flow cytometric analyses and the mouse model, we thoroughly investigated the impact of such a treatment on the immune response and the generation of protective immunity to influenza. We demonstrated that influenza-specific CD8(+) effector T cell recruitment was reduced up to 81% in the lungs of mice treated with oseltamivir (5 or 50 mg/kg twice daily; EC50 49 nM in vitro) compared to saline controls, but cell generation was unaffected in draining lymph nodes. Importantly, we showed that oseltamivir administration significantly decreased the pools of tissue-resident and circulating effector memory (93.7%) and central memory CD8(+) T cells (45%) compared to saline controls. During heterologous secondary infection, a decreased memory CD8(+) T cell pool combined with reduced generation of secondary influenza-specific effectors in the lymph nodes resulted in 10-fold decreased CD8(+) T cell recall responses, which increased mouse morbidity and delayed viral clearance. Furthermore, antiviral administration led to a significant 5.7-fold decreased production of functional anti-influenza antibodies. Thus, our study demonstrates that antiviral treatment affects the development of the adaptive immune response and protective immunity against influenza.

Successful treatment with oseltamivir phosphate in a patient with chronic immune thrombocytopenia positive for anti-GPIb/IX autoantibody

The management of chronic immune thrombocytopenia (ITP) remains to be a challenge. Oseltamivir phosphate is a sialidase inhibitor agent used to treat influenza in the conventional sense. At present, we demonstrate for the first time that an adult chronic ITP patient with anti-GP Ib/IX autoantibody, who was resistant to corticosteroids, IVIG, recombinant human thrombopoietin, rituximab, danazol and vindesine, but was successfully treated with oseltamivir phosphate. Through flow cytometric analysis of β-galactose and β-GlcNAc exposure on platelet surfaces, we showed that oseltamivir phosphate could reduce the desialylation level of platelet glycoproteins in ITP patient. The substantial alleviation of thrombocytopenia in this case, though not leading to conclusions, lays a foundation for a novel approach for the treatment of ITP.

Neuraminidase inhibitors for preventing and treating influenza in adults and children

BACKGROUND

Neuraminidase inhibitors (NIs) are stockpiled and recommended by public health agencies for treating and preventing seasonal and pandemic influenza. They are used clinically worldwide.

OBJECTIVES

To describe the potential benefits and harms of NIs for influenza in all age groups by reviewing all clinical study reports of published and unpublished randomised, placebo-controlled trials and regulatory comments.

SEARCH METHODS

We searched trial registries, electronic databases (to 22 July 2013) and regulatory archives, and corresponded with manufacturers to identify all trials. We also requested clinical study reports. We focused on the primary data sources of manufacturers but we checked that there were no published randomised controlled trials (RCTs) from non-manufacturer sources by running electronic searches in the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE (Ovid), EMBASE, Embase.com, PubMed (not MEDLINE), the Database of Reviews of Effects, the NHS Economic Evaluation Database and the Health Economic Evaluations Database.

SELECTION CRITERIA

Randomised, placebo-controlled trials on adults and children with confirmed or suspected exposure to naturally occurring influenza.

DATA COLLECTION AND ANALYSIS

We extracted clinical study reports and assessed risk of bias using purpose-built instruments. We analysed the effects of zanamivir and oseltamivir on time to first alleviation of symptoms, influenza outcomes, complications, hospitalisations and adverse events in the intention-to-treat (ITT) population. All trials were sponsored by the manufacturers.

MAIN RESULTS

We obtained 107 clinical study reports from the European Medicines Agency (EMA), GlaxoSmithKline and Roche. We accessed comments by the US Food and Drug Administration (FDA), EMA and Japanese regulator. We included 53 trials in Stage 1 (a judgement of appropriate study design) and 46 in Stage 2 (formal analysis), including 20 oseltamivir (9623 participants) and 26 zanamivir trials (14,628 participants). Inadequate reporting put most of the zanamivir studies and half of the oseltamivir studies at a high risk of selection bias. There were inadequate measures in place to protect 11 studies of oseltamivir from performance bias due to non-identical presentation of placebo. Attrition bias was high across the oseltamivir studies and there was also evidence of selective reporting for both the zanamivir and oseltamivir studies. The placebo interventions in both sets of trials may have contained active substances. Time to first symptom alleviation. For the treatment of adults, oseltamivir reduced the time to first alleviation of symptoms by 16.8 hours (95% confidence interval (CI) 8.4 to 25.1 hours, P < 0.0001). This represents a reduction in the time to first alleviation of symptoms from 7 to 6.3 days. There was no effect in asthmatic children, but in otherwise healthy children there was (reduction by a mean difference of 29 hours, 95% CI 12 to 47 hours, P = 0.001). Zanamivir reduced the time to first alleviation of symptoms in adults by 0.60 days (95% CI 0.39 to 0.81 days, P < 0.00001), equating to a reduction in the mean duration of symptoms from 6.6 to 6.0 days. The effect in children was not significant. In subgroup analysis we found no evidence of a difference in treatment effect for zanamivir on time to first alleviation of symptoms in adults in the influenza-infected and non-influenza-infected subgroups (P = 0.53). Hospitalisations. Treatment of adults with oseltamivir had no significant effect on hospitalisations: risk difference (RD) 0.15% (95% CI -0.78 to 0.91). There was also no significant effect in children or in prophylaxis. Zanamivir hospitalisation data were unreported. Serious influenza complications or those leading to study withdrawal. In adult treatment trials, oseltamivir did not significantly reduce those complications classified as serious or those which led to study withdrawal (RD 0.07%, 95% CI -0.78 to 0.44), nor in child treatment trials; neither did zanamivir in the treatment of adults or in prophylaxis. There were insufficient events to compare this outcome for oseltamivir in prophylaxis or zanamivir in the treatment of children. Pneumonia. Oseltamivir significantly reduced self reported, investigator-mediated, unverified pneumonia (RD 1.00%, 95% CI 0.22 to 1.49); number needed to treat to benefit (NNTB) = 100 (95% CI 67 to 451) in the treated population. The effect was not significant in the five trials that used a more detailed diagnostic form for pneumonia. There were no definitions of pneumonia (or other complications) in any trial. No oseltamivir treatment studies reported effects on radiologically confirmed pneumonia. There was no significant effect on unverified pneumonia in children. There was no significant effect of zanamivir on either self reported or radiologically confirmed pneumonia. In prophylaxis, zanamivir significantly reduced the risk of self reported, investigator-mediated, unverified pneumonia in adults (RD 0.32%, 95% CI 0.09 to 0.41); NNTB = 311 (95% CI 244 to 1086), but not oseltamivir. Bronchitis, sinusitis and otitis media. Zanamivir significantly reduced the risk of bronchitis in adult treatment trials (RD 1.80%, 95% CI 0.65 to 2.80); NNTB = 56 (36 to 155), but not oseltamivir. Neither NI significantly reduced the risk of otitis media and sinusitis in both adults and children. Harms of treatment. Oseltamivir in the treatment of adults increased the risk of nausea (RD 3.66%, 95% CI 0.90 to 7.39); number needed to treat to harm (NNTH) = 28 (95% CI 14 to 112) and vomiting (RD 4.56%, 95% CI 2.39 to 7.58); NNTH = 22 (14 to 42). The proportion of participants with four-fold increases in antibody titre was significantly lower in the treated group compared to the control group (RR 0.92, 95% CI 0.86 to 0.97, I(2) statistic = 0%) (5% absolute difference between arms). Oseltamivir significantly decreased the risk of diarrhoea (RD 2.33%, 95% CI 0.14 to 3.81); NNTB = 43 (95% CI 27 to 709) and cardiac events (RD 0.68%, 95% CI 0.04 to 1.0); NNTB = 148 (101 to 2509) compared to placebo during the on-treatment period. There was a dose-response effect on psychiatric events in the two oseltamivir "pivotal" treatment trials, WV15670 and WV15671, at 150 mg (standard dose) and 300 mg daily (high dose) (P = 0.038). In the treatment of children, oseltamivir induced vomiting (RD 5.34%, 95% CI 1.75 to 10.29); NNTH = 19 (95% CI 10 to 57). There was a significantly lower proportion of children on oseltamivir with a four-fold increase in antibodies (RR 0.90, 95% CI 0.80 to 1.00, I(2) = 0%). Prophylaxis. In prophylaxis trials, oseltamivir and zanamivir reduced the risk of symptomatic influenza in individuals (oseltamivir: RD 3.05% (95% CI 1.83 to 3.88); NNTB = 33 (26 to 55); zanamivir: RD 1.98% (95% CI 0.98 to 2.54); NNTB = 51 (40 to 103)) and in households (oseltamivir: RD 13.6% (95% CI 9.52 to 15.47); NNTB = 7 (6 to 11); zanamivir: RD 14.84% (95% CI 12.18 to 16.55); NNTB = 7 (7 to 9)). There was no significant effect on asymptomatic influenza (oseltamivir: RR 1.14 (95% CI 0.39 to 3.33); zanamivir: RR 0.97 (95% CI 0.76 to 1.24)). Non-influenza, influenza-like illness could not be assessed due to data not being fully reported. In oseltamivir prophylaxis studies, psychiatric adverse events were increased in the combined on- and off-treatment periods (RD 1.06%, 95% CI 0.07 to 2.76); NNTH = 94 (95% CI 36 to 1538) in the study treatment population. Oseltamivir increased the risk of headaches whilst on treatment (RD 3.15%, 95% CI 0.88 to 5.78); NNTH = 32 (95% CI 18 to 115), renal events whilst on treatment (RD 0.67%, 95% CI -2.93 to 0.01); NNTH = 150 (NNTH 35 to NNTB > 1000) and nausea whilst on treatment (RD 4.15%, 95% CI 0.86 to 9.51); NNTH = 25 (95% CI 11 to 116).

AUTHORS' CONCLUSIONS

Oseltamivir and zanamivir have small, non-specific effects on reducing the time to alleviation of influenza symptoms in adults, but not in asthmatic children. Using either drug as prophylaxis reduces the risk of developing symptomatic influenza. Treatment trials with oseltamivir or zanamivir do not settle the question of whether the complications of influenza (such as pneumonia) are reduced, because of a lack of diagnostic definitions. The use of oseltamivir increases the risk of adverse effects, such as nausea, vomiting, psychiatric effects and renal events in adults and vomiting in children. The lower bioavailability may explain the lower toxicity of zanamivir compared to oseltamivir. The balance between benefits and harms should be considered when making decisions about use of both NIs for either the prophylaxis or treatment of influenza. The influenza virus-specific mechanism of action proposed by the producers does not fit the clinical evidence.

Normalizing glycosphingolipids restores function in CD4+ T cells from lupus patients

Patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE) have multiple defects in lymphocyte signaling and function that contribute to disease pathogenesis. Such defects could be attributed to alterations in metabolic processes, including abnormal control of lipid biosynthesis pathways. Here, we reveal that CD4+ T cells from SLE patients displayed an altered profile of lipid raft-associated glycosphingolipids (GSLs) compared with that of healthy controls. In particular, lactosylceramide, globotriaosylceramide (Gb3), and monosialotetrahexosylganglioside (GM1) levels were markedly increased. Elevated GSLs in SLE patients were associated with increased expression of liver X receptor β (LXRβ), a nuclear receptor that controls cellular lipid metabolism and trafficking and influences acquired immune responses. Stimulation of CD4+ T cells isolated from healthy donors with synthetic and endogenous LXR agonists promoted GSL expression, which was blocked by an LXR antagonist. Increased GSL expression in CD4+ T cells was associated with intracellular accumulation and accelerated trafficking of GSL, reminiscent of cells from patients with glycolipid storage diseases. Inhibition of GSL biosynthesis in vitro with a clinically approved inhibitor (N-butyldeoxynojirimycin) normalized GSL metabolism, corrected CD4+ T cell signaling and functional defects, and decreased anti-dsDNA antibody production by autologous B cells in SLE patients. Our data demonstrate that lipid metabolism defects contribute to SLE pathogenesis and suggest that targeting GSL biosynthesis restores T cell function in SLE.

Early infection with respiratory syncytial virus impairs regulatory T cell function and increases susceptibility to allergic asthma

Immune tolerance is instituted early in life, during which time regulatory T (T(reg)) cells have an important role. Recurrent infections with respiratory syncytial virus (RSV) in early life increase the risk for asthma in adult life. Repeated infection of infant mice tolerized to ovalbumin (OVA) through their mother's milk with RSV induced allergic airway disease in response to OVA sensitization and challenge, including airway inflammation, hyper-reactivity and higher OVA-specific IgE, as compared to uninfected tolerized control mice. Virus infection induced GATA-3 expression and T helper type 2 (T(H)2) cytokine production in forkhead box P3 (FOXP3)(+) T(reg) cells and compromised the suppressive function of pulmonary T(reg) cells in a manner that was dependent on interleukin-4 receptor α (IL-4Rα) expression in the host. Thus, by promoting a T(H)2-type inflammatory response in the lung, RSV induced a T(H)2-like effector phenotype in T(reg) cells and attenuated tolerance to an unrelated antigen (allergen). Our findings highlight a mechanism by which viral infection targets a host-protective mechanism in early life and increases susceptibility to allergic disease.

Sialidases on mammalian sperm mediate deciduous sialylation during capacitation

Sialic acids (Sias) mediate many biological functions, including molecular recognition during development, immune response, and fertilization. A Sia-rich glycocalyx coats the surface of sperm, allowing them to survive as allogeneic cells in the female reproductive tract despite female immunity. During capacitation, sperm lose a fraction of their Sias. We quantified shed Sia monosaccharides released from capacitated sperm and measured sperm sialidase activity. We report the presence of two sialidases (neuraminidases Neu1 and Neu3) on mammalian sperm. These are themselves shed from sperm during capacitation. Inhibiting sialidase activity interferes with sperm binding to the zona pellucida of the ovum. A survey of human sperm samples for the presence of sialidases NEU1 and NEU3 identified a lack of one or both sialidases in sperm of some male idiopathic infertility cases. The results contribute new insights into the dynamic remodeling of the sperm glycocalyx prior to fertilization.

Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children

BACKGROUND

Planning for outbreaks of influenza is a high priority public health issue for national governments. Neuraminidase inhibitors (NIs) are thought to help reduce the symptoms of influenza with several possible mechanisms proposed. NIs have been stockpiled with a view to their widespread use in the event of a pandemic. However, the evidence base for this class of agents remains a source of debate. In a previous review we have documented substantial risks of publication bias of trials of NIs for influenza (60% of patient data from phase III treatment trials of oseltamivir have never been published) and reporting bias in the published trials. Our confidence in the conclusions of previous versions of this review has been subsequently undermined. Since we have become aware of a large number of unpublished trials of NIs in the management of influenza, this review updates and merges existing reviews in this area.

OBJECTIVES

To review clinical study reports of placebo-controlled randomised trials, regulatory comments and reviews ('regulatory information') of the effects of the NIs oseltamivir and zanamivir for influenza in all age groups and appraise trial programmes, rather than single studies.Clinical study reports are very detailed, unpublished clinical trial data containing in-depth descriptions of protocol rationale, methods analysis plans, trial results and organisational documents (such as contracts). A series of clinical studies designed and conducted by one sponsor represents a trial programme of a drug indication (for example treatment of influenza).

SEARCH METHODS

We searched trial registries, cross-referencing published and unpublished sources and corresponded with manufacturers and regulators. We searched the archives of the US Food and Drug Administration (FDA) and European and Japanese regulators. The evidence in this review reflects searches to obtain relevant information up to 12 April 2011.

SELECTION CRITERIA

We included regulatory information based on assessments of randomised controlled trials (RCTs) conducted in people of any age who had either confirmed or suspected influenza, or who had been exposed to influenza in the local community or place of residence. We included information which had been made available by our deadline.

DATA COLLECTION AND ANALYSIS

We indexed regulatory information in two purpose-built instruments and reconstructed trials using CONSORT statement-based templates. To progress to Stage 2 (full analysis) we sought manufacturer explanations of discrepancies in the data. GlaxoSmithKline (GSK) offered us individual patient data and responded to our queries, but Roche did not provide us with complete clinical study reports. In Stage 2 we intended to analyse trials with validated data (i.e. assuming our validation questions aimed at clarifying omissions and discrepancies were resolved). No studies progressed to Stage 2. We carried out analyses of the effects of oseltamivir on time to first alleviation of symptoms and hospitalisations using the intention-to-treat (ITT) population and tested five hypotheses generated post-protocol publication.

MAIN RESULTS

We included and analysed data from 25 studies (15 oseltamivir and 10 zanamivir studies). We could not use data from a further 42 studies due to insufficient information or unresolved discrepancies in their data. The included trials were predominantly conducted in adults during influenza seasons in both hemispheres. A small number of studies were conducted in older people residing in care homes and in people with underlying respiratory diseases. The studies had adequate randomisation and blinding procedures, but imbalances in the analysis populations available (ITT influenza-infected) left many of the studies at risk of attrition bias. All the studies were sponsored by manufacturers of NIs. Time to first alleviation of symptoms in people with influenza-like illness symptoms (i.e. ITT population) was a median of 160 hours (range 125 to 192 hours) in the placebo groups and oseltamivir shortened this by around 21 hours (95% confidence interval (CI) -29.5 to -12.9 hours, P < 0.001; five studies) but there was no evidence of effect on hospitalisations based on seven studies with a median placebo group event rate of 0.84% (range 0% to 11%): odds ratio (OR) 0.95; 95% CI 0.57 to 1.61, P = 0.86). These results are based on the comprehensive ITT population data and are unlikely to be biased. A post-protocol analysis showed that participants randomised to oseltamivir in treatment trials had a reduced odds being diagnosed with influenza (OR 0.83; 95% CI 0.73 to 0.94, P = 0.003; eight studies), probably due to an altered antibody response. Zanamivir trials showed no evidence of this. Due to limitations in the design, conduct and reporting of the trial programme, the data available to us lacked sufficient detail to credibly assess a possible effect of oseltamivir on complications and viral transmission. We postponed analysis of zanamivir evidence because of the offer of individual patient data (IPD) from its manufacturer. The authors have been unable to obtain the full set of clinical study reports or obtain verification of data from the manufacturer of oseltamivir (Roche) despite five requests between June 2010 and February 2011. No substantial comments were made by Roche on the protocol of our Cochrane Review which has been publicly available since December 2010.

AUTHORS' CONCLUSIONS

We found a high risk of publication and reporting biases in the trial programme of oseltamivir. Sub-population analyses of the influenza infected population in the oseltamivir trial programme are not possible because the two arms are non-comparable due to oseltamivir's apparent interference with antibody production. The evidence supports a direct oseltamivir mechanism of action on symptoms but we are unable to draw conclusions about its effect on complications or transmission. We expect full clinical study reports containing study protocol, reporting analysis plan, statistical analysis plan and individual patient data to clarify outstanding issues. These full clinical study reports are at present unavailable to us.

Current work and future possibilities for the management of severe influenza: using immunomodulatory agents that target the host response

In this article, we argue the case that the excessive inflammatory response seen in severe influenza contributes to severe illness and death by disabling oxidative phosphorylation in mitochondria, leading to reduced cellular levels of ATP. When the mitochondrial permeability transition is induced, cells cannot die by apoptosis in the face of reduced ATP levels, because apoptosis depends upon ATP availability, and so cells undergo necrosis. Cellular necrosis causes release of proinflammatory molecules such as high mobility group box 1 protein and mitochondrial DNA, and these could contribute to the prolongation of inflammation during severe influenza. With these concepts in mind, we discuss how immunomodulatory agents that prevent cellular necrosis (by restoring mitochondrial function) and limit inflammation are promising influenza treatments.

Role of lipid rafts in liver health and disease

Liver diseases are an increasingly common cause of morbidity and mortality; new approaches for investigation of mechanisms of liver diseases and identification of therapeutic targets are emergent. Lipid rafts (LRs) are specialized domains of cellular membranes that are enriched in saturated lipids; they are small, mobile, and are key components of cellular architecture, protein partition to cellular membranes, and signaling events. LRs have been identified in the membranes of all liver cells, parenchymal and non-parenchymal; more importantly, LRs are active participants in multiple physiological and pathological conditions in individual types of liver cells. This article aims to review experimental-based evidence with regard to LRs in the liver, from the perspective of the liver as a whole organ composed of a multitude of cell types. We have gathered up-to-date information related to the role of LRs in individual types of liver cells, in liver health and diseases, and identified the possibilities of LR-dependent therapeutic targets in liver diseases.

Differential pathogenesis of respiratory syncytial virus clinical isolates in BALB/c mice

Airway mucus is a hallmark of respiratory syncytial virus (RSV) lower respiratory tract illness. Laboratory RSV strains differentially induce airway mucus production in mice. Here, we tested the hypothesis that RSV strains differ in pathogenesis by screening six low-passage RSV clinical isolates for mucogenicity and virulence in BALB/cJ mice. The RSV clinical isolates induced variable disease severity, lung interleukin-13 (IL-13) levels, and gob-5 levels in BALB/cJ mice. We chose two of these clinical isolates for further study. Infection of BALB/cJ mice with RSV A2001/2-20 (2-20) resulted in greater disease severity, higher lung IL-13 levels, and higher lung gob-5 levels than infection with RSV strains A2, line 19, Long, and A2001/3-12 (3-12). Like the line 19 RSV strain, the 2-20 clinical isolate induced airway mucin expression in BALB/cJ mice. The 2-20 and 3-12 RSV clinical isolates had higher lung viral loads than laboratory RSV strains at 1 day postinfection (p.i.). This increased viral load correlated with higher viral antigen levels in the bronchiolar epithelium and greater histopathologic changes at 1 day p.i. The A2 RSV strain had the highest peak viral load at day 4 p.i. RSV 2-20 infection caused epithelial desquamation, bronchiolitis, airway hyperresponsiveness, and increased breathing effort in BALB/cJ mice. We found that RSV clinical isolates induce variable pathogenesis in mice, and we established a mouse model of clinical isolate strain-dependent RSV pathogenesis that recapitulates key features of RSV disease.

Oseltamivir treatment of mice before or after mild influenza infection reduced cellular and cytokine inflammation in the lung

BACKGROUND

Lung inflammation is a critical determinant of influenza infection outcomes but is seldom evaluated in animal studies of oseltamivir (OS), which have focused on viral titre and survival.

OBJECTIVES

To study the effects of pre- and post-infection dosing with OS on viral replication and inflammation in a mouse model of non-lethal influenza infection.

METHODS

BALB/c mice were infected with a laboratory-adapted H3N1 strain of influenza. In pre-dosing studies, OS was gavaged twice daily (1 and 10 mg/kg/day) from 4 hours prior to infection and continuing for 5 days (d) post-infection (p.i). In the second post-infection dosing study, dosing at 10 mg/kg/day began at 24-48 hours p.i. Mice were dissected at d3, d5 and d7 p.i. (pre-dosing study) and d5 p.i. (post-dosing study). Lung viral titres were determined by plaque assay. Bronchoalveolar lavage fluid (BALF) was collected and used for the quantitation of inflammatory cells and mediators.

RESULTS

Pre-infection dosing of OS reduced total cells, neutrophils and macrophages in BALF. With pre- or post-infection dosing, the pro-inflammatory mediators TNF-α, IL-1β, IL-6 and granulocyte-macrophage colony-stimulating factor, the neutrophil chemokines keratinocyte-derived chemokine and MIP-1α and the macrophage chemokine MCP-1 were reduced in BALF. Pre-dosing with 1 mg/kg OS did not reduce viral titres, while 10 mg/kg slightly reduced viral titres at d3 and d5 p.i.

CONCLUSIONS

Oseltamivir reduced the inflammatory response to influenza when given pre- or post-infection. This anti-inflammatory effect may contribute to the clinical benefit of OS.

Beta-glucosylceramide ameliorates liver inflammation in murine autoimmune cholangitis

We have demonstrated spontaneous development of autoimmune cholangitis, similar to human primary biliary cirrhosis, in mice expressing a dominant negative form of the transforming growth factor-beta receptor (dnTGF-betaRII) restricted to T cells. The autoimmune cholangitis appears to be mediated by autoreactive CD8(+) T lymphocytes that home to the portal tracts and biliary system. Because the liver pathology is primarily secondary to CD8(+) T cells, we have determined herein whether administration of beta-glucosylceramide (GC), a naturally occurring plant glycosphingolipid, alters the natural history of disease in this model. We chose GC because previous work has demonstrated its ability to alter CD8(+) T cell responses and to down-regulate tissue inflammation. Accordingly, dnTGF-betaRII mice were treated with either GC or control for a period of 18 weeks beginning at 6 weeks of age. Importantly, in mice that received GC, there was a significant decrease in the frequency and absolute number of autoreactive liver-infiltrating CD8(+) T cells, accompanied by a significant decrease in activated CD44(high) CD8(+) T cell populations. Further, there was a significant reduction in portal inflammation in GC-treated mice. Interestingly, there were no changes in anti-mitochondrial antibodies, CD4(+) T cells, CD19(+) B cells or natural killer (NK) T cell populations, indicating further that the beneficial effects of GC on liver inflammation were targeted specifically to liver-infiltrating CD8(+) T cells. These data suggest that further work on GC in models of CD8(+) T-mediated inflammation are needed and point to a new therapeutic venue for potentially treating and/or modulating autoimmune disease.

Differential regulation of GM1 and asialo-GM1 expression by T cells and natural killer (NK) cells in respiratory syncytial virus infection

We previously reported that respiratory syncytial virus (RSV) infection increases lung CD8(+) T cell GM1 expression. The related lipid asialo-GM1 (ASGM1) is expressed by T cells in viral infection and by natural killer (NK) cells. The in vivo co-expression of GM1 and ASGM1 by immune cells is not defined. Here we analyzed lung lymphocyte GM1 and ASGM1 expression in RSV-infected mice. GM1 and ASGM1 were coordinately upregulated by activated CD8(+) T cells in RSV-infected BALB/c and C57BL/6 mice. In contrast, RSV infection had no effect on constitutively high NK cell GM1 expression, while increasing NK cell ASGM1 expression. GM1 and ASGM1 co-localized in lipid raft structures in NK and CD8(+) T cells sorted from the lungs of RSV-infected mice. Anti-ASGM1 Ab treatment of RSV-infected BALB/c mice depleted GM1/ASGM1-expressing NK cells and GM1/ASGM1-expressing T cells, reduced lung IFN-gamma levels, increased viral load, delayed viral clearance, and reduced illness. STAT1(-/-) mice are more susceptible to RSV replication and disease than wild-type mice. In RSV-infected STAT1(-/-) mice, anti-ASGM1 Ab altered cytokine levels, but in contrast to BALB/c mice, antibody treatment had no effect on viral load or illness. Taken together, GM1 and ASGM1 expression are differentially regulated by T and NK cells in RSV infection. Also, GM1/ASGM1-expressing cells are important for control of RSV in BALB/c mice, whereas STAT1(-/-) mice clear RSV by an alternative pathway.

Lipid rafts and T-lymphocyte function: implications for autoimmunity

Experimental evidence indicates that the mammalian cell membrane is compartmentalized. A structural feature that supports membrane segmentation implicates assemblies of selected lipids broadly referred to as lipid rafts. In T-lymphocytes, lipid rafts are implicated in signalling from the T-cell antigen receptor (TCR) and in localization and function of proteins residing proximal to the receptor. This review summarizes the current literature that deals with lipid raft involvement in T-cell activation and places particular emphasis in recent studies investigating lipid rafts in autoimmunity. The potential of lipid rafts as targets for the development of a new class of immune-modulating compounds is discussed.

Limited inhibitory effects of oseltamivir and zanamivir on human sialidases

Oseltamivir (Tamiflu) and zanamivir (Relenza), two extensively used clinically effective anti-influenza drugs, are viral sialidase (also known as neuraminidase) inhibitors that prevent the release of progeny virions and thereby limit the spread of infection. Recently mortalities and neuropsychiatric events have been reported with the use of oseltamivir, especially in pediatric cases in Japan, suggesting that these drugs might also inhibit endogenous enzymes involved in sialic acid metabolism, including sialidase, sialyltransferase, and CMP-synthase, in addition to their inhibitory effects on the viral sialidase. The possible inhibition could account for some of the rare side effects of oseltamivir. However, there has been little direct evidence in regard to the sensitivities of animal sialidases to these drugs. Here, we examined whether these inhibitors might indeed affect the activities of human sialidases, which differ in primary structures and enzyme properties but possess tertiary structures similar to those of the viral enzymes. Using recombinant enzymes corresponding to the four human sialidases identified so far, we found that oseltamivir carboxylate scarcely affected the activities of any of the sialidases, even at 1 mM, while zanamivir significantly inhibited the human sialidases NEU3 and NEU2 in the micromolar range (K(i), 3.7 +/- 0.48 and 12.9 +/- 0.07 microM, respectively), providing a contrast to the low nanomolar concentrations at which these drugs block the activity of the viral sialidases.

A nonsynonymous SNP in human cytosolic sialidase in a small Asian population results in reduced enzyme activity: potential link with severe adverse reactions to oseltamivir

The use of oseltamivir, widely stockpiled as one of the drugs for use in a possible avian influenza pandemic, has been reported to be associated with neuropsychiatric disorders and severe skin reactions, primarily in Japan. Here we identified a nonsynonymous SNP (single nucleotide polymorphism) in dbSNP database, R41Q, near the enzymatic active site of human cytosolic sialidase, a homologue of virus neuraminidase that is the target of oseltamivir. This SNP occurred in 9.29% of Asian population and none of European and African American population. Our structural analyses and Ki measurements using in vitro sialidase assays indicated that this SNP could increase the unintended binding affinity of human sialidase to oseltamivir carboxylate, the active form of oseltamivir, thus reducing sialidase activity. In addition, this SNP itself results in an enzyme with an intrinsically lower sialidase activity, as shown by its increased Km and decreased Vmax values. Theoretically administration of oseltamivir to people with this SNP might further reduce their sialidase activity. We note the similarity between the reported neuropsychiatric side effects of oseltamivir and the known symptoms of human sialidase-related disorders. We propose that this Asian-enriched sialidase variation caused by the SNP, likely in homozygous form, may be associated with certain severe adverse reactions to oseltamivir.