Different populations of A(H1N1)pdm09 viruses in a patient with hemolytic-uremic syndrome.

Respiratory viral infections may have different impacts ranging from infection without symptoms to severe disease or even death though the reasons are not well characterized. A patient (age group 5-15 years) displaying symptoms of hemolytic uremic syndrome died one day after hospitalization. qPCR, next generation sequencing, virus isolation, antigenic characterization, resistance analysis was performed and virus replication kinetics in well-differentiated airway cells were determined. Autopsy revealed hemorrhagic pneumonia as major pathological manifestation. Lung samples harbored a large population of A(H1N1)pdm09 viruses with the polymorphism H456H/Y in PB1 polymerase. The H456H/Y viruses replicated much faster to high viral titers than upper respiratory tract viruses in vitro. H456H/Y-infected air-liquid interface cultures of differentiated airway epithelial cells did reflect a more pronounced loss of ciliated cells. A different pattern of virus quasispecies was found in the upper airway samples where substitution S263S/F (HA1) was observed. The data support the notion that viral quasispecies had evolved locally in the lung to support high replicative fitness. This change may have initiated further pathogenic processes leading to rapid dissemination of inflammatory mediators followed by development of hemorrhagic lung lesions and fatal outcome.

Preparing for the Next Influenza Season: Monitoring the Emergence and Spread of Antiviral Resistance.

Purpose: The relaxation of pandemic restrictions in 2022 has led to a reemergence of respiratory virus circulation worldwide and anticipation of substantial influenza waves for the 2022/2023 Northern Hemisphere winter. Therefore, the antiviral susceptibility profiles of human influenza viruses circulating in Germany were characterized. Methods: Between October 2019 (week 40/2019) and March 2022 (week 12/2022), nasal swabs from untreated patients with acute respiratory symptoms were collected in the national German influenza surveillance system. A total of 598 influenza viruses were isolated and analyzed for susceptibility to oseltamivir, zanamivir and peramivir, using a neuraminidase (NA) inhibition assay. In addition, next-generation sequencing was applied to assess molecular markers of resistance to NA, cap-dependent endonuclease (PA) and M2 ion channel inhibitors (NAI, PAI, M2I) in 367 primary clinical samples. Furthermore, a genotyping assay based on RT-PCR and pyrosequencing to rapidly assess the molecular resistance marker PA-I38X in PA genes was designed and established. Results: While NAI resistance in the strict sense, defined by a ≥ 10-fold (influenza A) or ≥5-fold (influenza B) increase of NAI IC50, was not detected, a subtype A(H1N1)pdm09 isolate displayed 2.3- to 7.5-fold IC50 increase for all three NAI. This isolate carried the NA-S247N substitution, which is known to enhance NAI resistance induced by NA-H275Y. All sequenced influenza A viruses carried the M2-S31N substitution, which confers resistance to M2I. Of note, one A(H3N2) virus displayed the PA-I38M substitution, which is associated with reduced susceptibility to the PAI baloxavir marboxil. Pyrosequencing analysis confirmed these findings in the original clinical specimen and in cultured virus isolate, suggesting sufficient replicative fitness of this virus mutant. Conclusion: Over the last three influenza seasons, the vast majority of influenza viruses in this national-level sentinel were susceptible to NAIs and PAIs. These findings support the use of antivirals in the upcoming influenza season.

Insights into the direct anti-influenza virus mode of action of Rhodiola rosea.

BACKGROUND: The anti-influenza A virus activities and contents of previously isolated most active flavonoids (rhodiosin and tricin) from a standardized hydro-ethanolic R. rosea root and rhizome extract (SHR-5®), did not fully explain the efficacy of SHR-5®. Moreover, the mode of antiviral action of SHR-5® is unknown. PURPOSE: To determine the anti-influenza viral principle of SHR-5® we evaluated i) the combined anti-influenza virus effect of rhodiosin and tricin, ii) the impact of its tannin-enriched fraction (TE), iii) its antiviral spectrum and mode of action, and iv) its propensity for resistance development in vitro. METHODS: The combined anti-influenza virus effect of rhodiosin and tricin and the impact of TE were investigated with cytopathic effect (CPE)-inhibition assays in MDCK cells. A tannin-depleted fraction (TD) and TE were prepared by polyamide column chromatography and dereplicated by LC-MS. Plaque-reduction assays provided insights into the anti-influenza virus profile, the mode of action, and the propensity for resistance development of SHR-5®. RESULTS: Our results i) did not reveal synergistic anti-influenza A virus effects of rhodiosin and tricin, but ii) proved a strong impact of TE mainly composed of prodelphinidin gallate oligomers. iii) TE inhibited the plaque-production of influenza virus A(H1N1)pdm09, A(H3N2), and B (Victoria and Yamagata) isolates (including isolates resistant to neuraminidase and/or M2 ion channel inhibitors) with 50% inhibitory concentration values between 0.12 - 0.53 µg/ml similar to SHR-5®. Mechanistic studies proved a virucidal activity, inhibition of viral adsorption, viral neuraminidase activity, and virus spread by SHR-5® and TE. iv) No resistance development was observed in vitro. CONCLUSION: For the first time a comprehensive analysis of the anti-influenza virus profile of a hydro-ethanolic R. rosea extract (SHR-5®) was assessed in vitro. The results demonstrating broad-spectrum multiple direct anti-influenza virus activities, and a lack of resistance development to SHR-5® together with its known augmentation of host defense, support its potential role as an adaptogen against influenza virus infection.

Trends in respiratory virus circulation following COVID-19-targeted nonpharmaceutical interventions in Germany, January - September 2020: Analysis of national surveillance data.

BACKGROUND: During the initial COVID-19 response, Germany's Federal Government implemented several nonpharmaceutical interventions (NPIs) that were instrumental in suppressing early exponential spread of SARS-CoV-2. NPI effect on the transmission of other respiratory viruses has not been examined at the national level thus far. METHODS: Upper respiratory tract specimens from 3580 patients with acute respiratory infection (ARI), collected within the nationwide German ARI Sentinel, underwent RT-PCR diagnostics for multiple respiratory viruses. The observation period (weeks 1-38 of 2020) included the time before, during and after a far-reaching contact ban. Detection rates for different viruses were compared to 2017-2019 sentinel data (15350 samples; week 1-38, 11823 samples). FINDINGS: The March 2020 contact ban, which was followed by a mask mandate, was associated with an unprecedented and sustained decline of multiple respiratory viruses. Among these, rhinovirus was the single agent that resurged to levels equalling those of previous years. Rhinovirus rebound was first observed in children, after schools and daycares had reopened. By contrast, other nonenveloped viruses (i.e. gastroenteritis viruses reported at the national level) suppressed after the shutdown did not rebound. INTERPRETATION: Contact restrictions with a subsequent mask mandate in spring may substantially reduce respiratory virus circulation. This reduction appears sustained for most viruses, indicating that the activity of influenza and other respiratory viruses during the subsequent winter season might be low,whereas rhinovirus resurgence, potentially driven by transmission in educational institutions in a setting of waning population immunity, might signal predominance of rhinovirus-related ARIs. FUNDING: Robert Koch-Institute and German Ministry of Health.

Prophylaxis and treatment of influenza: options, antiviral susceptibility, and existing recommendations.

Influenza viruses of types A and B attack 5-10% of adults and 20-30% of children, thereby causing millions of acute respiratory infections in Germany annually. A significant number of these infections are associated with complications such as pneumonia and bacterial superinfections that need hospitalization and might lead to death. In addition to vaccines, drugs were developed that might support influenza prevention and that can be used to treat influenza patients. The timely application of anti-influenza drugs can inhibit virus replication, help reduce and shorten the symptoms, and prevent death as well as virus transmission. This review concisely describes the mechanism of action, the potential for prophylactic and therapeutic use, and the knowledge on resistance of anti-influenza drugs approved today. However, the main aim is to give an overview on the recommendations available in Germany for the proper use of these drugs. In doing so, the recommendations published in statements and guidelines of medical societies as well as the German influenza pandemic preparedness plan are summarized with the consideration of specific circumstances and groups of patients.

Zoonotic infection with swine A/H1avN1 influenza virus in a child, Germany, June 2020.

A zoonotic A/sw/H1avN1 1C.2.2 influenza virus infection was detected in a German child that presented with influenza-like illness, including high fever. There was a history of close contact with pigs 3 days before symptom onset. The child recovered within 3 days. No other transmissions were observed. Serological investigations of the virus isolate revealed cross-reactions with ferret antisera against influenza A(H1N1)pdm09 virus, indicating a closer antigenic relationship with A(H1N1)pdm09 than with the former seasonal H1N1 viruses.

Prospective surveillance of antiviral resistance in hospitalized infants less than 12 months of age with A(H3N2) influenza infection and treated with oseltamivir.

BACKGROUND: Infants exhibit elevated influenza virus loads and prolonged viral shedding, which may increase the risk for resistance development, especially in cases of suboptimal exposure to antiviral therapy. METHODS: We performed a prospective surveillance of hospitalized infants undergoing oseltamivir therapy during the 2008-2009 and 2011-2012 influenza seasons at two paediatric hospitals in Germany. A total of 37 infants less than 1 year of age with laboratory confirmed influenza A(H3N2) infection received oseltamivir as per physician's order for 5 days (2008-2009 season: 2 mg/kg twice daily; 2011-2012 season: 2.0 mg/kg; 2.5 mg/kg and 3.0 mg/kg twice daily for infants <1 month; 2-3 months and 4-12 months, respectively). Virus load, the susceptibility to neuraminidase inhibitors (NAIs), and the presence of molecular markers of resistance to NAIs was assessed for influenza viruses recovered from respiratory samples collected at baseline and during follow-up visits. RESULTS: Overall, 73% of the infants continued to shed viral RNA detectable by reverse transcription (RT)-PCR after dose number 10 of oseltamivir; 12 infants shed viruses, 2 of them (both 9 months of age) shed resistant viruses. Resistance was characterized by ≥1,000-fold increase of 50% inhibitory concentration (IC50) for oseltamivir, up to 50-fold for zanamivir and elevated Km values when compared to susceptible A(H3N2) strains. Sanger sequencing revealed the selection of the NA-R292K substitution in both instances (after dose number 10 on day 6). CONCLUSIONS: Our data suggest that it may be relevant to monitor antiviral resistance systematically in all infants, considering that the European Medicines Agency has recently extended the licensure for oseltamivir to include full-term infants.

Pharmacokinetics of Oral and Intravenous Oseltamivir Treatment of Severe Influenza B Virus Infection Requiring Organ Replacement Therapy.

BACKGROUND AND OBJECTIVES: Patients with severe influenza virus infection, multi-organ failure and organ replacement therapy may absorb and metabolize neuraminidase inhibitors differently. Systematic pharmacokinetic/pharmacodynamic clinical trials are currently lacking in this high-risk group. Inadequate dosing increases the risk of treatment failure and drug resistance, especially in severely ill patients with elevated virus loads. This study aims to explore the impact of organ replacement therapy on oseltamivir drug concentrations. METHODS: Serial pharmacokinetic/pharmacodynamic measurements and Sieving coefficients were assessed in two patients with severe influenza B infection requiring organ replacement therapy. RESULTS: Patient #1, a 9-year-old female with severe influenza B virus infection, biventricular assist device, and continuous veno-venous hemodiafiltration, received 75 mg oral oseltamivir twice-daily for 2 days, then intravenous oseltamivir with one-time renoprotective dosing (40 mg), followed by regular intravenous administration of 100 mg twice-daily. Plasma oseltamivir carboxylate concentrations were stable initially, but only regular administration of 100 mg resulted in virus load decline and clinical improvement. Patient #2, a 28-year-old female with influenza B virus infection requiring extracorporeal membrane oxygenation, received 75 mg oral oseltamivir twice-daily, resulting in erratic oseltamivir blood concentrations. In both patients, drug concentrations remained well within safety margins. CONCLUSIONS: In severe cases with multi-organ failure, administration of 100 mg intravenous oseltamivir twice-daily provided reliable drug concentrations, as opposed to renoprotective and oral dosing, thereby minimizing the risk of treatment failure and drug resistance. Evidence-based pediatric dosing recommendations and effective intravenous antiviral treatment modalities are needed for intensive care patients with life-threatening influenza disease.

Influenza viruses - antiviral therapy and resistance.

Influenza is a serious and frequently underestimated, but vaccine preventable disease. The adamantane derivates rimantadine and amantadine and the neuraminidase inhibitors zanamivir and oseltamivir are the only antiviral drugs currently approved in Europe for therapy and prophylaxis of influenza infections. Resistance to these drugs occurs due to mutations within the therapeutic target proteins M2 ion channel protein and viral neuraminidase. An unexpected occurrence of oseltamivir-resistant seasonal A(H1N1) viruses was detected in winter 2007/2008. The prevalence of these viruses increased rapidly and nearby all viruses circulating during the following seasons were resistant to oseltamivir. The A(H1N1)pdm09 viruses replaced the former seasonal A(H1N1) subtype during the 2009-2010 influenza season. Fortunately, resistance to neuraminidase inhibitors was detected in A(H1N1)pdm09, A(H3N2) and influenza B viruses only sporadically and was treatment related mostly. Comprehensive analyses of circulating viruses showed a high prevalence of A(H3N2) influenza viruses that are resistant to adamantane derivates since 2004/2005 and a progressive trend in the prevalence of resistant viruses up to 100% in following seasons. The M2 ion channel protein of A(H1N1)pdm09 viruses is associated with the Eurasian avian-like swine lineage and thus show "natural" resistance to adamantane derivates. Therefore, only neuraminidase inhibitors are recommended for influenza treatment today. This manuscript summarizes the occurrence and spread of antiviral resistant influenza viruses and highlights the importance for developing and/or approving new antiviral compounds.

Evaluation of novel second-generation RSV and influenza rapid tests at the point of care.

Acute respiratory infections represent common pediatric emergencies. Infection control warrants immediate and accurate diagnoses. In the past, first-generation respiratory syncytial virus (RSV) rapid tests (strip tests) have shown suboptimal sensitivities. In 2013, the Food and Drug Administration licensed a second-generation RSV rapid test providing user-independent readouts (SOFIA™-RSV) using automated fluorescence assay technology known to yield superior results with influenza rapid testing. We are reporting the first point-of-care evaluation of the SOFIA™-RSV rapid test. In the Charité Influenza-Like Disease Cohort, 686 nasopharyngeal samples were tested in parallel with SOFIA™-RSV and SOFIA™-Influenza A+B. Compared to real-time PCR, SOFIA™-RSV sensitivities/specificities were 78.6%/93.9%, respectively (SOFIA™-Influenza A: 80.6%/99.3%). Performance was greatest in patients below 2 years of age with a test sensitivity of 81.8%. RSV sensitivities were highest (85%) in the first 2 days of illness and with nasopharyngeal compared to nasal swabs (P=0.055, McNemar's test). Second-generation RSV and influenza rapid testing provides highly accurate results facilitating timely patient cohortation and management.

Inhibitory potency of flavonoid derivatives on influenza virus neuraminidase.

The constant risk of emerging new influenza virus strains that are resistant to established inhibitors like oseltamivir leaves influenza neuraminidase (NA) a prominent target for drug design. The inhibitory activity of several flavonoid derivatives was experimentally tested in comparison to oseltamivir for the NA expressed by the seasonal influenza virus strains A/California/7/09 (A(H1N1)pdm09), A/Perth/16/09 (A(H3N2)), and B/Brisbane/60/08. IC50 values of polyphenols confirmed moderate inhibition in the µM range. Structurally, the amount and site of glycosylation of tested flavonoids have no significant influence on their inhibitory potency. In a pharmacophore-based docking approach the structure-activity relationship was evaluated. Molecular dynamics simulations revealed highly flexible parts of the enzyme and the contribution of salt bridges to the structural stability of NA. The findings of this study elucidate the impact of flavonoids on viral neuraminidase activity and the analysis of their modes of action provide valuable information about the mechanism of NA inhibition.

Quantitative influenza follow-up testing (QIFT)--a novel biomarker for the monitoring of disease activity at the point-of-care.

BACKGROUND: Influenza infections induce considerable disease burden in young children. Biomarkers for the monitoring of disease activity at the point-of-care (POC) are currently lacking. Recent methodologies for fluorescence-based rapid testing have been developed to provide improved sensitivities with the initial diagnosis. The present study aims to explore the utility of second-generation rapid testing during longitudinal follow-up of influenza patients (Rapid Influenza Follow-up Testing = RIFT). Signal/control fluorescent readouts (Quantitative Influenza Follow-up Testing = QIFT) are evaluated as a potential biomarker for the monitoring of disease activity at the POC. METHODS AND FINDINGS: RIFT (SOFIA) and QIFT were performed at the POC and compared to blinded RT-PCR at the National Reference Centre for Influenza. From 10/2011-4/2013, a total of 2048 paediatric cases were studied prospectively; 273 cases were PCR-confirmed for influenza. During follow-up, RIFT results turned negative either prior to PCR (68%), or simultaneously (30%). The first negative RIFT occurred after a median of 8 days with a median virus load (VL) of 5.6×10∧3 copies/ml and cycle threshold of 37, with no evidence of viral rebound. Binning analysis revealed that QIFT differentiated accurately between patients with low, medium and high viral titres. QIFT increase/decrease showed 88% agreement (sensitivity = 52%, specificity = 95%) with VL increase/decrease, respectively. QIFT-based viral clearance estimates showed similar values compared to PCR-based estimates. Variations in viral clearance rates were lower in treated compared to untreated patients. The study was limited by use of non-invasive, semi-quantitative nasopharyngeal samples. VL measurements below the limit of detection could not be quantified reliably. CONCLUSIONS: During follow-up, RIFT provides a first surrogate measure for influenza disease activity. A "switch" from positive to negative values may indicate a drop in viral load below a critical threshold, where rebound is no longer expected. QIFT may provide a useful tool for the monitoring of disease burden and viral clearance at the POC.

Early detection of influenza A and B infection in infants and children using conventional and fluorescence-based rapid testing.

BACKGROUND: The appropriate management of infants and children with influenza depends on the accurate and timely diagnosis, ideally at the point of care (POC). OBJECTIVES: To evaluate the use of simultaneous RSV/influenza rapid testing with QuickVue™ test strips as well as (the use of) novel, fluorescence-based, rapid influenza antigen testing (SOFIA™) in infants and children with influenza-like illness (ILI). STUDY DESIGN: The Study was conducted in a real-time surveillance program at the Charité Department of Pediatrics in collaboration with the National Reference Centre for Influenza at the Robert Koch Institute (RKI) in Berlin, Germany (Charité Influenza-Like Disease=ChILD Cohort). RESULTS: During the 2010/2011 influenza season, 395 infants and children were simultaneously tested using QuickVue™ FluA&B and RSV10 rapid tests at POC compared to independent RT-PCR. Sensitivities were 62.7/67.8% for Influenza/RSV overall, but highest in infants <1 year with 76.0/76.2%. The evaluation of the fluorescence-based rapid test SOFIA™ with frozen laboratory samples (derived from the 2008/2009 and 2010/2011 national surveillance) yielded sensitivities of 97.7/86.7/86.7/81.7% for influenza A(H1N1)pdm09/A(H3N2)/B-Victoria/B-Yamagata in samples with CT values <34, and 80.2/79.8/67.5/62.5% for all CT values combined. The same method used at POC with 649 consecutive ChILD patients in 2011-2012 yielded sensitivity/specificity/PPV/NPV values of 78.9/99.7/96.6/97.3%. Again, sensitivities were highest in infants (85.7%) and small children <2 years (88%). CONCLUSIONS: Fluorescence-based rapid antigen testing provides a highly sensitive and specific tool for POC diagnostics of acute influenza in the paediatric age group, especially in infants and small children <2 years, when viral loads are at their peak and treatment decisions are imminent.

Virus load kinetics and resistance development during oseltamivir treatment in infants and children infected with Influenza A(H1N1) 2009 and Influenza B viruses.

BACKGROUND: Infants and small children are the most effective transmitters of influenza, while bearing a high risk of hospitalization and adverse disease outcomes. This study aims to investigate virus load kinetics and resistance development during oseltamivir therapy in infants and children infected with influenza A(H1N1) 2009 and influenza B viruses. METHODS: Virus load in nasopharyngeal samples and phenotypic/genotypic neuraminidase inhibitor resistance were determined at baseline, at day 5 and in additional follow-up samples, if available. Patient-specific viral clearance indices CLν(i) were determined along with estimates of the time required to achieve nondetectable virus load. RESULTS: No evidence of baseline oseltamivir resistance was detected in 36 patients infected with influenza A(H1N1) 2009 (n = 27) or influenza B (Victoria, Yamagata; n = 9) before oseltamivir therapy. On average, viral loads were lower for influenza type B (median = 5.9·10/mL) than for drug-resistant (median = 2.6·10/mL) and sensitive A(H1N1) 2009 (median = 4.8·10/mL), P = 0.04 and P = 0.09, respectively. Time required to achieve nondetectable virus load was significantly longer in drug-resistant A(H1N1) 2009 (median 15.4 days) compared with drug-sensitive A(H1N1) 2009 (P = 0.003; median 7.7 days) and drug-sensitive influenza B (P = 0.001; median 5 days). No evidence of viral rebound was observed once viral clearance was achieved. CONCLUSIONS: Our data indicate that influenza subtyping in combination with baseline viral load measurements might help to optimize the duration of antiviral therapy in the individual child. Lower than expected virologic response rates in patients without malabsorption or compliance issues may suggest resistance development.

Genotypic and phenotypic resistance of pandemic A/H1N1 influenza viruses circulating in Germany.

In response to the rapid global spread of an antigenically novel A/H1N1 influenza virus in 2009, the World Heath Organization (WHO) recommended surveillance and monitoring for antiviral resistance of influenza viruses. We designed and evaluated pyrosequencing (PSQ)-based genotypic assays for high-throughput analysis of the susceptibility of pandemic A/H1N1 influenza viruses to neuraminidase (NA) inhibitors. A total of 1570 samples circulating in Germany between April 2009 and April 2010 were tested for determination of molecular markers of resistance to the NA inhibitors oseltamivir and zanamivir, and 635 of them were evaluated by phenotypic fluorescence-based assay with MUNANA substrate. Eight (0.5%) viruses were resistant to oseltamivir due to the H274Y NA substitution (N2 numbering). Six of these oseltamivir-resistant cases were treatment-related; four of them were selected in immunocompromised patients, two in patients suffered from chronic diseases. The two remaining oseltamivir-resistant viruses seem to have evolved in the absence of drug treatment and were isolated from immunocompetent healthy patients. All tested A/H1N1 pandemic viruses were sensitive to zanamivir. In addition, analysis of 1011 pandemic A/H1N1 virus samples by a PSQ-based assay according to the WHO protocol revealed the presence of mutation S31N in the M2 protein that conferred resistance to M2 ion channel inhibitors. Our data demonstrate a low incidence of oseltamivir-resistant pandemic A/H1N1 influenza variants isolated under drug selection pressure as well as community-acquired or naturally evolving viruses.

A new and rapid genotypic assay for the detection of neuraminidase inhibitor resistant influenza A viruses of subtype H1N1, H3N2, and H5N1.

The neuraminidase of influenza viruses is the target of the inhibitors oseltamivir and zanamivir. Recent reports on influenza viruses with reduced susceptibility to neuraminidase inhibitors (NAI) are a cause for concern. Several amino acid substitutions, each as a consequence of one single nucleotide mutation, are known to confer resistance to NAI. An increase of NAI-resistant viruses appears to be likely as a result of a wider application of NAI for treatment and prophylaxis of seasonal influenza infections. Monitoring the occurrence and spread of resistant viruses is an important task. Therefore, RT-PCR assays were developed with subsequent pyrosequencing analysis (PSQ-PCR). These assays allow a rapid, high-throughput and cost-effective screening of subtype A/H1N1, A/H3N2, and A/H5N1 viruses. Various specimens such as respiratory swabs, allantoic fluid, or cell-propagated viruses can be used and results are available within hours. Several A/H1N1, A/H3N2, and A/H5N1 viruses isolated from human and avian specimens were tested to evaluate the method. Positive controls encoding resistance-associated mutations were created using site-directed mutagenesis. The results obtained with these controls showed that the assay can discriminate clearly the wild-type virus from a mutant virus. The detection limit of minor virus variants within the viral quasispecies amounts to 10%.

Human gammadelta T cells as mediators of chimaeric-receptor redirected anti-tumour immunity.

Human peripheral blood gammadelta T cells (Vgamma9(+) Vdelta2(+)) can be selectively expanded in vivo by the systemic administration of aminobisphosphonates without prior antigen priming. To assess the potential of human gammadelta T cells to serve as effector cells of specific anti-tumour immunity, we expanded peripheral blood-derived gammadelta T cells and transduced them with recombinant retrovirus encoding G(D2)- or CD19-specific chimaeric receptors. Flow cytometric analysis of T cells from four individual donors cultured in the presence of zoledronate at day 14 of culture showed selective enrichment of the gammadelta T cell population (Vgamma9(+) Vdelta2(+) CD3(+) CD4(-) CD8(-)) to 73-96% of total CD3(+) T cells. Retroviral gene transfer resulted in chimaeric receptor surface expression in 73 +/- 12% of the population. Transduced gammadelta T cells efficiently recognized antigen-expressing tumour cell targets, as demonstrated by target-specific upregulation of CD69 and secretion of interferon-alpha. Moreover, transduced gammadelta T cells efficiently and specifically lysed the antigen-expressing tumour targets. They could be efficiently expanded in vitro and maintained in culture for prolonged periods. Zoledronate-activated human gammadelta T cells expressing chimaeric receptors may thus serve as potent and specific anti-tumour effector cells. Their responsiveness to stimulation with aminobisphosphonates may enable the selective re-expansion of adoptively transferred T cells in vivo, permitting long lasting anti-tumour immune control.