Validation of a severe acute respiratory syndrome coronavirus 2 microneutralization assay for evaluation of vaccine immunogenicity.

As variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to emerge, assessment of vaccine immunogenicity remains a critical factor to support continued vaccination. To this end, an in vitro microneutralization (MN50) assay was validated to quantitate SARS-CoV-2 neutralizing antibodies against prototype and variant strains (Beta, Delta, Omicron BA.1, Omicron BA.5, and XBB.1.5) in human serum. For the prototype strain, the MN50 assay met acceptance criteria for inter-/intra-assay precision, specificity, linearity, and selectivity. The assay was robust against changes to virus/serum incubation time, cell seeding density, virus content per well, cell passage number, and serum interference. Analyte in serum samples was stable up to five freeze/thaw cycles and for up to 12 months of storage at -80 ± 10 °C. Similar results were observed for the variant-adapted MN50 assays. The conversion factor to convert assay result units to WHO international standard units (IU/mL) was determined to be 0.62 for the prototype strain. This MN50 assay will be useful for vaccine immunogenicity analyses in clinical trial samples, enabling assessment of vaccine immunogenicity for ancestral and variant strains as variant-adapted vaccines are developed.

A Phase 3, randomized, non-inferiority study of a heterologous booster dose of SARS CoV-2 recombinant spike protein vaccine in adults.

Due to waning immunity following primary immunization with COVID-19 vaccines, booster doses may be required. The present study assessed a heterologous booster of SII-NVX-CoV2373 (spike protein vaccine) in adults primed with viral vector and inactivated vaccines. In this Phase 3, observer-blind, randomized, active controlled study, a total of 372 adults primed with two doses of ChAdOx1 nCoV-19 (n = 186) or BBV152 (n = 186) at least six months ago, were randomized to receive a booster of SII-NVX-CoV2373 or control vaccine (homologous booster of ChAdOx1 nCoV-19 or BBV152). Anti-S IgG and neutralizing antibodies (nAbs) were assessed at days 1, 29, and 181. Non-inferiority (NI) of SII-NVX-CoV2373 to the control vaccine was assessed based on the ratio of geometric mean ELISA units (GMEU) of anti-S IgG and geometric mean titers (GMT) of nAbs (NI margin > 0.67) as well as seroresponse (≥ 2 fold-rise in titers) (NI margin -10%) at day 29. Safety was assessed throughout the study period. In both the ChAdOx1 nCoV-19 prime and BBV152 prime cohorts, 186 participants each received the study vaccines. In the ChAdOx1 nCoV-19 prime cohort, the GMEU ratio was 2.05 (95% CI 1.73, 2.43) and the GMT ratio was 1.89 (95% CI 1.55, 2.32) whereas the difference in the proportion of seroresponse was 49.32% (95% CI 36.49, 60.45) for anti-S IgG and 15% (95% CI 5.65, 25.05) for nAbs on day 29. In the BBV152 prime cohort, the GMEU ratio was 5.12 (95% CI 4.20, 6.24) and the GMT ratio was 4.80 (95% CI 3.76, 6.12) whereas the difference in the proportion of seroresponse was 74.08% (95% CI 63.24, 82.17) for anti-S IgG and 24.71% (95% CI 16.26, 34.62) for nAbs on day 29. The non-inferiority of SII-NVX-CoV2373 booster to the control vaccine for each prime cohort was met. SII-NVX-CoV2373 booster showed significantly higher immune responses than BBV152 homologous booster. On day 181, seroresponse rates were ≥ 70% in all the groups for both nAbs and anti-S IgG. Solicited adverse events reported were transient and mostly mild in severity in all the groups. No causally related SAE was reported. SII-NVX-CoV2373 as a heterologous booster induced non-inferior immune responses as compared to homologous boosters in adults primed with ChAdOx1 nCoV-19 and BBV152. SII-NVX-CoV2373 showed a numerically higher boosting effect than homologous boosters. The vaccine was also safe and well tolerated.

Safety and Immunogenicity of SARS-CoV-2 Recombinant Spike Protein Vaccine in Children and Adolescents in India: A Phase 2-3 Randomized Clinical Trial.

Importance: The recombinant COVID-19 vaccine NVX-CoV2373 has demonstrated efficacy of approximately 90% in adults; however, its safety and efficacy in children is unknown. Objective: To assess the noninferiority of SII-NVX-CoV2373 in children and adolescents compared to adults and to evaluate its safety in comparison with placebo. Design, Setting, and Participants: This phase 2-3 observer-blind randomized clinical trial was conducted in 2 cohorts, children (aged 2 to 11 years) and adolescents (aged 12 to 17 years) between August 2021 and August 2022. Participants were randomized 3:1 to SII-NVX-CoV2373 or placebo and monitored for 179 days. The participants, study team, and laboratory staff were blinded. This was a multicenter study conducted across 10 tertiary care hospitals in India. Exclusion criteria included previous COVID-19 infection or vaccination, immunocompromised condition, and immunosuppressive medications. Interventions: Two doses of 0.5-mL SII-NVX-CoV2373 or placebo were administered intramuscularly on days 1 and 22. Main Outcomes and Measures: Primary outcomes were geometric mean titer ratio of both anti-spike (anti-S) IgG and neutralizing antibodies (NAbs) between both pediatric age groups to that of adults on day 36. Noninferiority was concluded if the lower bound of 95% CI of this ratio was greater than 0.67 for each age group. Both the antibodies were assessed for the index strain and for selected variants at various time points. Solicited adverse events (AEs) were recorded for 7 days after each vaccination, unsolicited AEs were recorded for 35 days, and serious AEs and AEs of special interest were recorded for 179 days. Results: A total of 460 children in each age cohort were randomized to receive vaccine or placebo. The mean (SD) age was 6.7 (2.7) years in the child cohort and 14.3 (1.6) years in the adolescent cohort; 231 participants (50.2%) in the child cohort and 218 in the adolescent cohort (47.4%) were female. Both anti-S IgG and NAb titers were markedly higher in the SII-NVX-CoV2373 group than in the placebo group on both day 36 and day 180. The geometric mean titer ratios compared to those in adults were 1.20 (95% CI, 1.08-1.34) and 1.52 (95% CI, 1.38-1.67) for anti-S IgG in adolescents and children, respectively; while for NAbs, they were 1.33 (95% CI, 1.17-1.50) and 1.93 (95% CI, 1.70-2.18) in adolescents and children, respectively, indicating noninferiority. SII-NVX-CoV2373 also showed immune responses against variants studied. Injection site reactions, fever, headache, malaise, and fatigue were common solicited AEs. There were no AEs of special interest and no causally related serious AEs. Conclusions and Relevance: SII-NVX-CoV2373 was safe and well tolerated in children and adolescents in this study. The vaccine was highly immunogenic and may be used in pediatric vaccination against COVID-19. Trial Registration: Clinical Trials Registry of India Identifier: CTRI/2021/02/031554.

Immunogenicity and safety of BPZE1, an intranasal live attenuated pertussis vaccine, versus tetanus-diphtheria-acellular pertussis vaccine: a randomised, double-blind, phase 2b trial.

BACKGROUND: Bordetella pertussis epidemics persist as transmission remains unabated despite high acellular pertussis vaccination rates. BPZE1, a live attenuated intranasal pertussis vaccine, was designed to prevent B pertussis infection and disease. We aimed to assess the immunogenicity and safety of BPZE1 compared with the tetanus-diphtheria-acellular pertussis vaccine (Tdap). METHODS: In this double-blind, phase 2b trial at three research centres in the USA, healthy adults aged 18-50 years were randomly assigned (2:2:1:1) via a permuted block randomisation schedule to receive BPZE1 vaccination followed by BPZE1 attenuated challenge, BPZE1 vaccination followed by placebo challenge, Tdap followed by BPZE1 attenuated challenge, or Tdap followed by placebo challenge. On day 1, lyophilised BPZE1 was reconstituted with sterile water and given intranasally (0·4 mL delivered to each nostril), whereas Tdap was given intramuscularly. To maintain masking, participants in the BPZE1 groups received an intramuscular saline injection, and those in the Tdap groups received intranasal lyophilised placebo buffer. The attenuated challenge took place on day 85. The primary immunogenicity endpoint was the proportion of participants achieving nasal secretory IgA seroconversion against at least one B pertussis antigen on day 29 or day 113. Reactogenicity was assessed up to 7 days after vaccination and challenge, and adverse events were recorded for 28 days after vaccination and challenge. Serious adverse events were monitored throughout the study. This trial is registered with ClinicalTrials.gov, NCT03942406. FINDINGS: Between June 17 and Oct 3, 2019, 458 participants were screened and 280 were randomly assigned to the main cohort: 92 to the BPZE1-BPZE1 group, 92 to the BPZE1-placebo group, 46 to the Tdap-BPZE1 group, and 50 to the Tdap-placebo group. Seroconversion of at least one B pertussis-specific nasal secretory IgA was recorded in 79 (94% [95% CI 87-98]) of 84 participants in the BPZE1-BPZE1 group, 89 (95% [88-98]) of 94 in the BPZE1-placebo group, 38 (90% [77-97]) of 42 in the Tdap-BPZE1 group, and 42 (93% [82-99]) of 45 in the Tdap-placebo group. BPZE1 induced broad and consistent B pertussis-specific mucosal secretory IgA responses, whereas Tdap did not induce consistent mucosal secretory IgA responses. Both vaccines were well tolerated, with mild reactogenicity and no serious adverse events related to study vaccination. INTERPRETATION: BPZE1 induced nasal mucosal immunity and produced functional serum responses. BPZE1 has the potential to avert B pertussis infections, which ultimately could lead to reduced transmission and diminished epidemic cycles. These results should be confirmed in large phase 3 trials. FUNDING: ILiAD Biotechnologies.

Safety and immunogenicity of SII-NVX-CoV2373 (COVID-19 vaccine) in adults in a phase 2/3, observer-blind, randomised, controlled study.

Background: NVX-CoV2373, a Covid-19 vaccine was developed in the USA with ∼90% efficacy. The same vaccine is manufactured in India after technology transfer (called as SII-NVX-CoV2373), was evaluated in this phase 2/3 immuno-bridging study. Methods: This was an observer-blind, randomised, phase 2/3 study in 1600 adults. In phase 2, 200 participants were randomized 3:1 to SII-NVX-CoV2373 or placebo. In phase 3, 1400 participants were randomized 3:1 to SII-NVX-CoV2373 or NVX-CoV2373 (940 safety cohort and 460 immunogenicity cohort). Two doses of study products (SII-NVX-CoV2373, NVX-CoV2373 or placebo) were given 3 weeks apart. Primary objectives were to demonstrate non-inferiority of SII-NVX-CoV2373 to NVX-CoV2373 in terms of geometric mean ELISA units (GMEU) ratio of anti-S IgG antibodies 14 days after the second dose (day 36) and to determine the incidence of causally related serious adverse events (SAEs) through 180 days after the first dose. Anti-S IgG response was assessed using an Enzyme-Linked Immunosorbent Assay (ELISA) and neutralizing antibodies (nAb) were assessed by a microneutralization assay using wild type SARS CoV-2 in participants from the immunogenicity cohort at baseline, day 22, day 36 and day 180. Cell mediated immune (CMI) response was assessed in a subset of 28 participants from immunogenicity cohort by ELISpot assay at baseline, day 36 and day 180. The total follow-up was for 6 months. Trial registration: CTRI/2021/02/031554. Findings: Total 1596 participants (200 in Phase 2 and 1396 in Phase 3) received the first dose. SII-NVX-CoV2373 was found non-inferior to NVX-CoV2373 (anti-S IgG antibodies GMEU ratio 0.91; 95% CI: 0.79, 1.06). At day 36, there was more than 58-fold rise in anti-S IgG and nAb titers compared to baseline in both the groups. On day 180 visit, these antibody titers declined to levels slightly lower than those after the first dose (13-22 fold-rise above baseline). Incidence of unsolicited and solicited AEs was similar between the SII-NVX-CoV2373 and NVX-CoV2373 groups. No adverse event of special interest (AESI) was reported. No causally related SAE was reported. Interpretation: SII-NVX-CoV2373 induced a non-inferior immune response compared to NVX-CoV2373 and has acceptable safety profile. Funding: SIIPL, Indian Council of Medical Research, Novavax.

Efficacy and safety of a universal influenza A vaccine (MVA-NP+M1) in adults when given after seasonal quadrivalent influenza vaccine immunisation (FLU009): a phase 2b, randomised, double-blind trial.

BACKGROUND: In animal, epidemiological, and human challenge studies, a pre-existing T-cell response to internal proteins of influenza A has been associated with improved virological and disease outcomes. The aim of this study was to assess whether inducing additional responses to conserved CD4 and CD8 T-cell antigens provides added benefit to standard influenza vaccination. METHODS: We designed a phase 2b, randomised, placebo-controlled, double-blind trial of a recombinant viral-vectored vaccine (modified vaccinia Ankara expressing virus nucleoprotein and matrix protein 1; MVA-NP+M1), which has been shown to induce both CD4 and CD8 T cells, at eight outpatient clinical trial sites in Australia over two consecutive influenza seasons. We recruited non-immunosuppressed adults (≥18 years) who had received the 2019 quadrivalent influenza vaccine (QIV) vaccine within 28 days before study enrolment and randomisation (day 0). Participants were randomly assigned (1:1) according to a computer-generated random sequence to receive one dose of 1·5 × 108 plaque-forming units of MVA-NP+M1 or saline (placebo) intramuscularly. Randomisation was stratified by age (<65 years or ≥65 years). The patients and trial assessors were masked to treatment assignment. During the subsequent influenza seasons, participants with symptoms related to respiratory illness or influenza-like illness were to attend the clinic within 72 h of symptom onset for two nasal swabs for influenza testing by quantitative RT-PCR. The primary endpoint was the incidence rate of laboratory-confirmed influenza in the intention-to-treat (ITT) population. Safety (solicited adverse events within 7 days and unsolicited adverse events within 28 days after study vaccination, and serious adverse events for the study duration) was assessed in all randomly assigned participants who received at least one vaccination (according to the treatment received). The trial is registered with ClinicalTrials.gov, NCT03880474. FINDINGS: Between April 2 and June 14, 2019, 2152 adults were randomly allocated and received MVA-NP+M1 (n=1077) or placebo (n=1075), comprising the efficacy (ITT) analysis set. Participants were followed up throughout the 2019 Australia influenza season (May 1 to Oct 15, 2019). 419 (19·5%) of 2152 participants were aged 65 years or older. The incidence of laboratory-confirmed influenza did not differ between the MVA-NP+M1 group (35 of 1077 participants; 3·25% [95% CI 2·31-4·44]) and the placebo group (23 of 1075; 2·14% [1·39-3·14]; Fisher's exact p=0·14). 23 severe solicited local injection site reactions were reported in 13 (0·6%) of 2152 participants, 22 of which were reported in the MVA-NP + M1 group (in 12 [1·1%] participants). 100 severe systemic events were reported in 45 (4·2%) MVA-NP + M1 recipients, and 20 were reported in 14 (1·3%) placebo recipients. Three unsolicited grade 3 events in three participants (two headache and one nausea, all in the MVA-NP+M1 group) were deemed vaccine related. 21 serious adverse events were reported in 18 (1·7%) of 1077 participants in the MVA-NP+M1 group and 25 serious adverse events were reported in 22 (2·0%) of 1075 participants in the placebo group; none were considered vaccine related. The trial was stopped after one season for futility on the recommendation of the data monitoring committee. INTERPRETATION: MVA-NP+M1 was well tolerated with no vaccine-associated serious adverse events. A vaccine designed to induce moderate T-cell responses to the cross-reactive internal proteins of influenza A did not lead to improved incidence when given within 28 days after standard QIV immunisation. A greater magnitude of T-cell response with a different vaccine or regimen, or localisation in the lungs via alternative delivery, such as intranasal or aerosol, might be successful and require further investigation. FUNDING: Vaccitech.

Validation of a single-step, single-tube reverse transcription loop-mediated isothermal amplification assay for rapid detection of SARS-CoV-2 RNA.

Introduction. The SARS-CoV-2 pandemic of 2020 has resulted in unparalleled requirements for RNA extraction kits and enzymes required for virus detection, leading to global shortages. This has necessitated the exploration of alternative diagnostic options to alleviate supply chain issues.Aim. To establish and validate a reverse transcription loop-mediated isothermal amplification (RT- LAMP) assay for the detection of SARS-CoV-2 from nasopharyngeal swabs.Methodology. We used a commercial RT-LAMP mastermix from OptiGene in combination with a primer set designed to detect the CDC N1 region of the SARS-CoV-2 nucleocapsid (N) gene. A single-tube, single-step fluorescence assay was implemented whereby 1 µl of universal transport medium (UTM) directly from a nasopharyngeal swab could be used as template, bypassing the requirement for RNA purification. Amplification and detection could be conducted in any thermocycler capable of holding 65 °C for 30 min and measure fluorescence in the FAM channel at 1 min intervals.Results. Assay evaluation by assessment of 157 clinical specimens previously screened by E-gene RT-qPCR revealed assay sensitivity and specificity of 87 and 100%, respectively. Results were fast, with an average time-to-positive (Tp) for 93 clinical samples of 14 min (sd±7 min). Using dilutions of SARS-CoV-2 virus spiked into UTM, we also evaluated assay performance against FDA guidelines for implementation of emergency-use diagnostics and established a limit-of-detection of 54 Tissue Culture Infectious Dose 50 per ml (TCID50 ml-1), with satisfactory assay sensitivity and specificity. A comparison of 20 clinical specimens between four laboratories showed excellent interlaboratory concordance; performing equally well on three different, commonly used thermocyclers, pointing to the robustness of the assay.Conclusion. With a simplified workflow, The N1 gene Single Tube Optigene LAMP assay (N1-STOP-LAMP) is a powerful, scalable option for specific and rapid detection of SARS-CoV-2 and an additional resource in the diagnostic armamentarium against COVID-19.

Safety, tolerability, and immunogenicity of influenza vaccination with a high-density microarray patch: Results from a randomized, controlled phase I clinical trial.

BACKGROUND: The Vaxxas high-density microarray patch (HD-MAP) consists of a high density of microprojections coated with vaccine for delivery into the skin. Microarray patches (MAPs) offer the possibility of improved vaccine thermostability as well as the potential to be safer, more acceptable, easier to use, and more cost-effective for the administration of vaccines than injection by needle and syringe (N&S). Here, we report a phase I trial using the Vaxxas HD-MAP to deliver a monovalent influenza vaccine that was to the best of our knowledge the first clinical trial to evaluate the safety, tolerability, and immunogenicity of lower doses of influenza vaccine delivered by MAPs. METHODS AND FINDINGS: HD-MAPs were coated with a monovalent, split inactivated influenza virus vaccine containing A/Singapore/GP1908/2015 H1N1 haemagglutinin (HA). Between February 2018 and March 2018, 60 healthy adults (age 18-35 years) in Melbourne, Australia were enrolled into part A of the study and vaccinated with either: HD-MAPs delivering 15 µg of A/Singapore/GP1908/2015 H1N1 HA antigen (A-Sing) to the volar forearm (FA); uncoated HD-MAPs; intramuscular (IM) injection of commercially available quadrivalent influenza vaccine (QIV) containing A/Singapore/GP1908/2015 H1N1 HA (15 µg/dose); or IM injection of H1N1 HA antigen (15 µg/dose). After 22 days' follow-up and assessment of the safety data, a further 150 healthy adults were enrolled and randomly assigned to 1 of 9 treatment groups. Participants (20 per group) were vaccinated with HD-MAPs delivering doses of 15, 10, 5, 2.5, or 0 µg of HA to the FA or 15 µg HA to the upper arm (UA), or IM injection of QIV. The primary objectives of the study were safety and tolerability. Secondary objectives were to assess the immunogenicity of the influenza vaccine delivered by HD-MAP. Primary and secondary objectives were assessed for up to 60 days post-vaccination. Clinical staff and participants were blind as to which HD-MAP treatment was administered and to administration of IM-QIV-15 or IM-A/Sing-15. All laboratory investigators were blind to treatment and participant allocation. Two further groups in part B (5 participants per group), not included in the main safety and immunological analysis, received HD-MAPs delivering 15 µg HA or uncoated HD-MAPs applied to the forearm. Biopsies were taken on days 1 and 4 for analysis of the cellular composition from the HD-MAP application sites. The vaccine coated onto HD-MAPs was antigenically stable when stored at 40°C for at least 12 months. HD-MAP vaccination was safe and well tolerated; any systemic or local adverse events (AEs) were mild or moderate. Observed systemic AEs were mostly headache or myalgia, and local AEs were application-site reactions, usually erythema. HD-MAP administration of 2.5 µg HA induced haemagglutination inhibition (HAI) and microneutralisation (MN) titres that were not significantly different to those induced by 15 µg HA injected IM (IM-QIV-15). HD-MAP delivery resulted in enhanced humoral responses compared with IM injection with higher HAI geometric mean titres (GMTs) at day 8 in the MAP-UA-15 (GMT 242.5, 95% CI 133.2-441.5), MAP-FA-15 (GMT 218.6, 95% CI 111.9-427.0), and MAP-FA-10 (GMT 437.1, 95% CI 254.3-751.3) groups compared with IM-QIV-15 (GMT 82.8, 95% CI 42.4-161.8), p = 0.02, p = 0.04, p < 0.001 for MAP-UA-15, MAP-FA-15, and MAP-FA-10, respectively. Higher titres were also observed at day 22 in the MAP-FA-10 (GMT 485.0, 95% CI 301.5-780.2, p = 0.001) and MAP-UA-15 (367.6, 95% CI 197.9-682.7, p = 0.02) groups compared with the IM-QIV-15 group (GMT 139.3, 95% CI 79.3-244.5). Results from a panel of exploratory immunoassays (antibody-dependent cellular cytotoxicity, CD4+ T-cell cytokine production, memory B cell (MBC) activation, and recognition of non-vaccine strains) indicated that, overall, Vaxxas HD-MAP delivery induced immune responses that were similar to, or higher than, those induced by IM injection of QIV. The small group sizes and use of a monovalent influenza vaccine were limitations of the study. CONCLUSIONS: Influenza vaccine coated onto the HD-MAP was stable stored at temperatures up to 40°C. Vaccination using the HD-MAP was safe and well tolerated and resulted in immune responses that were similar to or significantly enhanced compared with IM injection. Using the HD-MAP, a 2.5 µg dose (1/6 of the standard dose) induced HAI and MN titres similar to those induced by 15 µg HA injected IM. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR.org.au), trial ID 108 ACTRN12618000112268/U1111-1207-3550.

Safety, tolerability, acceptability and immunogenicity of an influenza vaccine delivered to human skin by a novel high-density microprojection array patch (Nanopatch™).

BACKGROUND: Injection using needle and syringe (N&S) is the most widely used method for vaccination, but requires trained healthcare workers. Fear of needles, risk of needle-stick injury, and the need to reconstitute lyophilised vaccines, are also drawbacks. The Nanopatch (NP) is a microarray skin patch comprised of a high-density array of microprojections dry-coated with vaccine that is being developed to address these shortcomings. Here we report a randomised, partly-blinded, placebo-controlled trial that represents the first use in humans of the NP to deliver a vaccine. METHODS: Healthy volunteers were vaccinated once with one of the following: (1) NPs coated with split inactivated influenza virus (A/California/07/2009 [H1N1], 15 µg haemagglutinin (HA) per dose), applied to the volar forearm (NP-HA/FA), n = 15; (2) NPs coated with split inactivated influenza virus (A/California/07/2009 [H1N1], 15 µg HA per dose), applied to the upper arm (NP-HA/UA), n = 15; (3) Fluvax® 2016 containing 15 µg of the same H1N1 HA antigen injected intramuscularly (IM) into the deltoid (IM-HA/D), n = 15; (4) NPs coated with excipients only, applied to the volar forearm (NP-placebo/FA), n = 5; (5) NPs coated with excipients only applied to the upper arm (NP-placebo/UA), n = 5; or (6) Saline injected IM into the deltoid (IM-placebo/D), n = 5. Antibody responses at days 0, 7, and 21 were measured by haemagglutination inhibition (HAI) and microneutralisation (MN) assays. FINDINGS: NP vaccination was safe and acceptable; all adverse events were mild or moderate. Most subjects (55%) receiving patch vaccinations (HA or placebo) preferred the NP compared with their past experience of IM injection with N&S (preferred by 24%). The antigen-vaccinated groups had statistically higher HAI titres at day 7 and 21 compared with baseline (p < 0.0001), with no statistical differences between the treatment groups (p > 0.05), although the group sizes were small. The geometric mean HAI titres at day 21 for the NP-HA/FA, NP-HA/UA and IM-HA/D groups were: 335 (189-593 95% CI), 160 (74-345 95% CI), and 221 (129-380 95% CI) respectively. A similar pattern of responses was seen with the MN assays. Application site reactions were mild or moderate, and more marked with the influenza vaccine NPs than with the placebo or IM injection. INTERPRETATION: Influenza vaccination using the NP appeared to be safe, and acceptable in this first time in humans study, and induced similar immune responses to vaccination by IM injection.

Derivatives of imidazotriazine and pyrrolotriazine C-nucleosides as potential new anti-HCV agents.

Previous investigations identified 2'-C-Me-branched ribo-C-nucleoside adenosine analogues, 1, which contains a pyrrolo[2,1-f][1,2,4]triazin-4-amine heterocyclic base, and 2, which contains an imidazo[2,1-f][1,2,4]triazin-4-amine heterocyclic base as two compounds with promising anti-HCV in vitro activity. This Letter describes the synthesis and evaluation of a series of novel analogues of these compounds substituted at the 2-, 7-, and 8-positions of the heterocyclic bases. A number of active new HCV inhibitors were identified but most compounds also demonstrated unacceptable cytotoxicity. However, the 7-fluoro analogue of 1 displayed good potency with a promising cytotherapeutic margin.

Discovery and Synthesis of C-Nucleosides as Potential New Anti-HCV Agents.

Nucleoside analogues have long been recognized as prospects for the discovery of direct acting antivirals (DAAs) to treat hepatitis C virus because they have generally exhibited cross-genotype activity and a high barrier to resistance. C-Nucleosides have the potential for improved metabolism and pharmacokinetic properties over their N-nucleoside counterparts due to the presence of a strong carbon-carbon glycosidic bond and a non-natural heterocyclic base. Three 2'CMe-C-adenosine analogues and two 2'CMe-guanosine analogues were synthesized and evaluated for their anti-HCV efficacy. The nucleotide triphosphates of four of these analogues were found to inhibit the NS5B polymerase, and adenosine analogue 1 was discovered to have excellent pharmacokinetic properties demonstrating the potential of this drug class.

Characterization of drug-resistant influenza virus A(H1N1) and A(H3N2) variants selected in vitro with laninamivir.

Neuraminidase inhibitors (NAIs) play a major role for managing influenza virus infections. The widespread oseltamivir resistance among 2007-2008 seasonal A(H1N1) viruses and community outbreaks of oseltamivir-resistant A(H1N1)pdm09 strains highlights the need for additional anti-influenza virus agents. Laninamivir is a novel long-lasting NAI that has demonstrated in vitro activity against influenza A and B viruses, and its prodrug (laninamivir octanoate) is in phase II clinical trials in the United States and other countries. Currently, little information is available on the mechanisms of resistance to laninamivir. In this study, we first performed neuraminidase (NA) inhibition assays to determine the activity of laninamivir against a set of influenza A viruses containing NA mutations conferring resistance to one or many other NAIs. We also generated drug-resistant A(H1N1) and A(H3N2) viruses under in vitro laninamivir pressure. Laninamivir demonstrated a profile of susceptibility that was similar to that of zanamivir. More specifically, it retained activity against oseltamivir-resistant H275Y and N295S A(H1N1) variants and the E119V A(H3N2) variant. In vitro, laninamivir pressure selected the E119A NA substitution in the A/Solomon Islands/3/2006 A(H1N1) background, whereas E119K and G147E NA changes along with a K133E hemagglutinin (HA) substitution were selected in the A/Quebec/144147/2009 A(H1N1)pdm09 strain. In the A/Brisbane/10/2007 A(H3N2) background, a large NA deletion accompanied by S138A/P194L HA substitutions was selected. This H3N2 variant had altered receptor-binding properties and was highly resistant to laninamivir in plaque reduction assays. Overall, we confirmed the similarity between zanamivir and laninamivir susceptibility profiles and demonstrated that both NA and HA changes can contribute to laninamivir resistance in vitro.

A zanamivir dimer with prophylactic and enhanced therapeutic activity against influenza viruses.

OBJECTIVES: Emerging drug resistance to antiviral therapies is an increasing challenge for the treatment of influenza virus infections. One new antiviral compound, BTA938, a dimeric derivative of the viral neuraminidase inhibitor zanamivir, contains a 14-carbon linker bridging two zanamivir moieties. In these studies, we evaluated antiviral efficacy in cell cultures infected with influenza virus and in mouse models of lethal influenza using H1N1pdm09, H3N2 and oseltamivir-resistant (H275Y) viruses. METHODS: In vitro activity was evaluated against 22 strains of influenza virus. Additionally, in vivo studies compared the efficacy of BTA938 or zanamivir after intranasal treatment. We also tested the hypothesis of a dual mode of action for BTA938 using scanning electron microscopy (SEM). RESULTS: BTA938 inhibited the viruses at nanomolar concentrations in vitro with a median 50% effective concentration value of 0.5 nM. In mouse models, the dimer provided ∼10-fold greater protection than zanamivir. The data also showed that a single low dose (3 mg/kg) protected 100% of mice from an otherwise lethal oseltamivir-resistant (H275Y) influenza virus infection. Remarkably, a single prophylactic treatment (10 mg/kg) administered 7 days before the challenge protected 70% of mice and when administered 1 or 3 days before the challenge it protected 90% of mice. Additionally, SEM provides evidence that the increased antiviral potency may be mediated by an enhanced aggregation of virus on the cell surface. CONCLUSIONS: In vitro and in vivo experiments showed the high antiviral activity of BTA938 for the treatment of influenza virus infections. Moreover, we demonstrated that a single dose of BTA938 is sufficient for prophylactic and therapeutic protection in mouse models.

CRM1-mediated nuclear export of dengue virus RNA polymerase NS5 modulates interleukin-8 induction and virus production.

Although all established functions of dengue virus NS5 (nonstructural protein 5) occur in the cytoplasm, its nuclear localization, mediated by dual nuclear localization sequences, is essential for virus replication. Here, we have determined the mechanism by which NS5 can localize in the cytoplasm to perform its role in replication, establishing for the first time that it is able to be exported from the nucleus by the exportin CRM1 and hence can shuttle between the nucleus and cytoplasm. We define the nuclear export sequence responsible to be residues 327-343 and confirm interaction of NS5 and CRM1 by pulldown assay. Significantly, greater nuclear accumulation of NS5 during infection due to CRM1 inhibition coincided with altered kinetics of virus production and decreased induction of the antiviral chemokine interleukin-8. This is the first report of a nuclear export sequence within NS5 for any member of the Flavivirus genus; because of its high conservation within the genus, it may represent a target for the treatment of diseases caused by several medically important flaviviruses.

The biarsenical dye Lumio exhibits a reduced ability to specifically detect tetracysteine-containing proteins within live cells.

Investigating the localisation of proteins within live cells via fluorescence microscopy typically involves the fusion of the protein of interest to a large fluorescent protein such as green fluorescent protein (GFP). Alternate fluorescent labelling technologies such as the fluorescent biarsenical dye molecules (e.g. FlAsH, ReAsH) are preferable to the use of large fusion proteins in many respects and allow greater flexibility in terms of the location of the labelling site. We assessed the ability of the FlAsH-derived biarsenical dye molecule Lumio to label a range of tetracysteine containing proteins within live cells and report that although in some circumstances Lumio is capable of positively detecting such proteins, the sensitivity and specificity of labelling is significantly reduced, making the Lumio-labelling system unsuitable for the detection of a wide range of protein within live cells.

Nuclear localization of dengue virus nonstructural protein 5 through its importin alpha/beta-recognized nuclear localization sequences is integral to viral infection.

Dengue virus nonstructural protein 5 (NS5) is a large multifunctional protein with a central role in viral replication. We previously identified two nuclear localization sequences (NLSs) within the central region of dengue virus type-2 (DENV-2) NS5 ('aNLS' and 'bNLS') that are recognized by the importin alpha/beta and importin beta1 nuclear transporters, respectively. Here, we demonstrate the importance of the kinetics of NS5 nuclear localization to virus production for the first time and show that the aNLS is responsible. Site-specific mutations in the bipartite-type aNLS or bNLS region were introduced into a reporter plasmid encoding green fluorescent protein fused to the N-terminus of DENV-2 NS5, as well as into DENV-2 genomic length complementary DNA. Mutation of basic residues in the highly conserved region of the bNLS did not affect nuclear import of NS5. In contrast, mutations in either basic cluster of the aNLS decreased NS5 nuclear accumulation and reduced virus production, with the greatest reduction observed for mutation of the second cluster (K(387)K(388)K(389)); mutagenesis of both clusters abolished NS5 nuclear import and DENV-2 virus production completely. The latter appeared to relate to the impaired ability of virus lacking nuclear-localizing NS5, as compared with wild-type virus expressing nuclear-localizing NS5, to reduce interleukin-8 production as part of the antiviral response. The results overall indicate that NS5 nuclear localization through the aNLS is integral to viral infection, with significant implications for other flaviviruses of medical importance, such as yellow fever and West Nile viruses.

Dengue virus RNA polymerase NS5: a potential therapeutic target?

Dengue fever (DF)/dengue haemorrhagic fever (DHF) is the most common arthropod-borne viral infection, where it is now estimated that 2.5-3 billion people world-wide are at risk of infection. Currently there is no available treatment, in the form of vaccine or drug, making eradication of the mosquito vector the only viable control measure, which has proved costly and of limited success. There are a number of different vaccines undergoing testing, but whilst a dengue vaccine is clearly desirable, there are several issues which make live-attenuated vaccines problematic. These include the phenomenon of antibody-dependent enhancement (ADE) and the possibility of recombination of attenuated vaccine strains with wild-type flavivirus members reverting vaccines to a virulent form. Until we gain a better understanding of these issues and their associated risks, the safety of any live dengue vaccine cannot be assured. It therefore may be safer and more feasible for therapeutic-based approaches to be developed as an alternative to live vaccines. As our understanding of dengue molecular biology expands, new potential targets for drugs are emerging. One of the most promising is the dengue non-structural protein 5 (NS5), the largest and most highly conserved of the dengue proteins. This review examines the unique properties of NS5, including its functions, interactions, subcellular localisation and regulation, and looks at ways in which some of these may be exploited in our quest for effective drugs.

CRM1-dependent nuclear export of dengue virus type 2 NS5.

The dengue virus multidomain RNA polymerase NS5 has been observed in the nucleus in mammalian infected cell systems. We previously showed that NS5 nuclear localization is mediated by two nuclear targeting signals within the NS5 interdomain region that are recognized by distinct members of the importin superfamily of intracellular transporters. Intriguingly, we have recently found that NS5 also possesses the ability to be exported from the nucleus by the importin family member CRM1 (exportin 1) both in Vero cells transfected to express NS5, and in dengue virus type 2 infected Vero cells, based on use of the CRM1-specific inhibitor leptomycin B (LMB). LMB treatment of Vero cells resulted in increased nuclear accumulation in both systems, and interestingly in the latter, resulted in an alteration in the kinetics of virus production. Our results imply that subcellular trafficking of NS5 at particular times in the infectious cycle may be central to the kinetics of virus production; perturbing this trafficking may represent a viable approach to develop new antiviral therapeutics.

Functional analysis and annotation of the virulence plasmid pMUM001 from Mycobacterium ulcerans.

The presence of a 174 kb plasmid called pMUM001 in Mycobacterium ulcerans, the first example of a mycobacterial plasmid encoding a virulence determinant, was recently reported. Over half of pMUM001 is devoted to six genes, three of which encode giant polyketide synthases (PKS) that produce mycolactone, an unusual cytotoxic lipid produced by M. ulcerans. In this present study the remaining 75 non-PKS-associated protein-coding sequences (CDS) are analysed and it is shown that pMUM001 is a low-copy-number element with a functional ori that supports replication in Mycobacterium marinum but not in the fast-growing mycobacteria Mycobacterium smegmatis and Mycobacterium fortuitum. Sequence analyses revealed a highly mosaic plasmid gene structure that is reminiscent of other large plasmids. Insertion sequences (IS) and fragments of IS, some previously unreported, are interspersed among functional gene clusters, such as those genes involved in plasmid replication, the synthesis of mycolactone, and a potential phosphorelay signal transduction system. Among the IS present on pMUM001 were multiple copies of the high-copy-number M. ulcerans elements IS2404 and IS2606. No plasmid transfer systems were identified, suggesting that trans-acting factors are required for mobilization. The results presented here provide important insights into this unusual virulence plasmid from an emerging but neglected human pathogen.

Common evolutionary origin for the unstable virulence plasmid pMUM found in geographically diverse strains of Mycobacterium ulcerans.

The 174-kb virulence plasmid pMUM001 in Mycobacterium ulcerans epidemic strain Agy99 harbors three very large and homologous genes that encode giant polyketide synthases (PKS) responsible for the synthesis of the lipid toxin mycolactone. Deeper investigation of M. ulcerans Agy99 resulted in identification of two types of spontaneous deletion variants of pMUM001 within a population of cells that also contained the intact plasmid. These variants arose from recombination between two 8-kb sections of the same plasmid sequence, resulting in the loss of a 65-kb region bearing two of the three mycolactone PKS genes. Investigation of nine diverse M. ulcerans strains by using PCR and Southern hybridization for eight pMUM001 gene sequences confirmed the presence of pMUM001-like elements (collectively called pMUM) in all M. ulcerans strains. Physical mapping of these plasmids revealed that like M. ulcerans Agy99, three strains had undergone major deletions in their mycolactone PKS loci. Online liquid chromatography-sequential mass spectrometry analysis of lipid extracts confirmed that strains with PKS deletions were unable to produce mycolactone or any related cometabolites. Interstrain comparisons of the plasmid gene sequences revealed greater than 98% nucleotide identity, and the phylogeny inferred from these sequences closely mimicked the phylogeny from a previous multilocus sequence typing study in which chromosomally encoded loci were used, a result that is consistent with the hypothesis that M. ulcerans diverged from the closely related organism Mycobacterium marinum by acquiring pMUM. Our results suggest that pMUM is a defining characteristic of M. ulcerans but that in the absence of purifying selection, deletion of plasmid sequences and a corresponding loss of mycolactone production readily arise.