Virological and clinical outcomes in outpatients treated with baloxavir or neuraminidase inhibitors for A(H3N2) influenza: A multicenter study of the 2022-2023 season

While clinical trials have illuminated both the virological and clinical efficacy of baloxavir for influenza and post-treatment viral resistance, these aspects warrant further study in real-world settings. In response, we executed a prospective, observational study of the Japanese 2022-2023 influenza season. A cohort of 73 A(H3N2)-diagnosed outpatients-36 treated with baloxavir, 20 with oseltamivir, and 17 with other neuraminidase inhibitors (NAIs)-were analyzed. Viral samples were collected before and after administering an antiviral on days 1, 5, and 10, respectively. Cultured viruses were amplified using RT-PCR and sequenced to detect mutations. Fever and other symptoms were tracked via self-reporting diaries. In the baloxavir cohort, viral detection was 11.1% (4/36) and 0% (0/36) on day 5 and day 10, respectively. Two isolates from day 5 (5.6%, 2/36) manifested I38T/M-substitutions in the polymerase acidic protein (PA). For oseltamivir and other NAIs, viral detection rates were 60.0% (12/20) and 52.9% (9/17) on day 5, and 16.7% (3/18) and 6.3% (1/16) on day 10, respectively. No oseltamivir-resistant neuraminidase mutations were identified after treatment. Median fever durations for the baloxavir, oseltamivir, and other NAI cohorts were 27.0, 38.0, and 36.0 h, respectively, with no significant difference. Two patients harboring PA I38T/M-substitutions did not exhibit prolonged fever or other symptoms. These findings affirm baloxavir's virological and clinical effectiveness against A(H3N2) in the 2022-2023 season and suggest limited clinical influence of post-treatment resistance emergence.

In vitro neuraminidase inhibitory concentrations (IC50) of four neuraminidase inhibitors in the Japanese 2022-23 season: Comparison with the 2010-11 to 2019-20 seasons

To assess the extent of susceptibility to the four neuraminidase inhibitors (NAIs) approved in Japan of the epidemic viruses in the 2022-23 influenza season in Japan, we measured the 50 % inhibitory concentration (IC50) of oseltamivir, zanamivir, peramivir, and laninamivir in influenza virus isolates from patients. Viral isolation was done with specimens obtained prior to and after treatment, and the type/subtype was determined by RT-PCR using type- and subtype-specific primers. The IC50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. Virus isolates, one A(H1N1)pdm09 and 74 A(H3N2), were measured in the 2022-23 season. The geometric mean IC50s of the 74 A(H3N2) isolated prior to treatment were 0.78 nM, 0.66 nM, 2.08 nM, and 2.85 nM for oseltamivir, peramivir, zanamivir, and laninamivir, respectively, comparable to those of the previous ten studied seasons. No A(H3N2) with highly reduced sensitivity to any of the NAIs was found in the 2022-23 season prior to or after drug administration. These results indicate that the sensitivity to these four commonly used NAIs has been maintained, at least for A(H3N2), in the 2022-23 influenza season in Japan, after the 2020-21 and 2021-22 seasons when the prevalence of influenza was extremely low.

Distinct features of SARS-CoV-2 humoral immunity against Omicron breakthrough infection

BACKGROUND

SARS-CoV-2 Omicron breakthrough infection (Omicron-BTI) after vaccination has been frequently observed. A more detailed understanding of the humoral immunity against Omicron-BTI is required.

METHODS

We measured strain-specific live-virus based neutralizing activity, anti-spike IgG, and anti-receptor-binding domain (RBD) IgG titers in individuals with Omicron/BA.1-BTI and directly compared them with controls with diverse combinations of wild-type (WT) mRNA vaccination and infection history.

RESULTS

Omicron-BTI individuals showed markedly higher neutralizing titers against all the WT, Delta, and Omicron strains in convalescent sera, compared with unvaccinated Omicron-infection individuals with only Omicron neutralizing activity. Similar tendencies were found in strain-specific anti-spike and anti-RBD IgG titers. The Omicron-specificity (BA.1/WT neutralizing ratio), Omicron-neutralizing efficiency per antibody unit, and anti-Omicron RBD-directivity of anti-spike antibodies in Omicron-BTI individuals were all significantly lower than those in unvaccinated Omicron-infection individuals, but they were equivalent to or higher than those in uninfected vaccinees. The induction of Omicron-specific neutralizing activity after Omicron-BTI was not weakened for eight months from the last vaccination.

CONCLUSIONS

These findings suggest that cross-reactive vaccine-induced immunity was intensively stimulated following Omicron breakthrough infection, which contributed to Omicron neutralization. Measuring SARS-CoV-2 variant-specific antibody levels as well as neutralizing activity is useful for evaluating humoral immunity after breakthrough infection in the current situation of antigenic gaps between vaccinated and epidemic (Omicron sub-lineages) strains.

Correlation between specific antibody response to wild-type BNT162b2 booster and the risk of breakthrough infection with omicron variants: Impact of household exposure in hospital healthcare workers

BACKGROUND

The emergence of omicron variants exhibiting antigenic changes has led to an increase in breakthrough infection among individuals with a wild-type SARS-CoV-2 vaccine booster. The correlation between post-booster spike-specific antibodies and omicron infection risk remains unclear.

METHODS

This prospective cohort study included SARS-CoV-2-naive healthcare workers with three-dose BNT162b2. Post-booster spike-specific IgG and interferon-γ levels were measured. Breakthrough infection was documented during a 10-month omicron-predominant period. Household and healthcare contacts were followed to identify subsequent infections. The IgG titers were additionally measured at the end of follow-up, and the titers at exposure were estimated from the two-point titers.

RESULTS

Of 333 participants, 89 developed infection, of whom 37 (41.6 %) were household contacts. Kaplan-Meier curves indicated that higher IgG titers were significantly correlated with lower cumulative infection incidence (p = 0.029), whereas the interferon-γ levels were not (p = 0.926). Multivariate Cox analysis showed that increasing IgG titers were associated with a reduced hazard ratio (HR) of 0.26 (95% CI, 0.12-0.55). Household exposure posed a greater infection risk than healthcare exposure (HRs, 11.24 [6.88-18.40] vs. 2.82 [1.37-5.44]). The difference in geometric mean IgG titers of infected and uninfected participants was significant among household contacts (20,244 AU/mL vs. 13,842 AU/mL, p = 0.031). Estimation of IgG titers at exposure showed a significantly higher infection incidence in those exposed with titers of <3,000 AU/mL than in those with higher titers (79.2 % vs. 32.3 %, p < 0.001).

CONCLUSIONS

Spike-specific antibodies induced by a wild-type SARS-CoV-2 vaccine booster are suggested to be effective in protecting against omicron infection. Household exposure would be a significant source of infection for hospital healthcare workers.

Achievement of sufficient antibody response after a fourth dose of wild-type SARS-CoV-2 mRNA vaccine in nursing home residents

BACKGROUND

Infection control during COVID-19 outbreaks in nursing facilities is a critical public health issue. Antibody responses before and after the fourth (second booster) dose of wild-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in nursing home residents have not been fully characterized.

METHODS

This study included 112 individuals: 54 nursing home residents (mean age: 84.4 years; 35 SARS-CoV-2-naive and 19 previously infected) and 58 healthcare workers (mean age: 47.7 years; 25 SARS-CoV-2-naive and 33 previously infected). Antispike and antinucleocapsid antibody responses to messenger RNA vaccination were evaluated using serum samples collected shortly and 5 months after the third dose, and shortly after the fourth dose.

RESULTS

The median immunoglobulin G (IgG) level in SARS-CoV-2-naive residents was similar to that in SARS-CoV-2-naive healthcare workers after the fourth dose (24,026.3 vs. 30,328.6 AU/mL, p = .79), whereas after the third dose the IgG level of SARS-CoV-2-naive residents was approximately twofold lower than that in SARS-CoV-2-naive healthcare workers. In residents with previous SARS-CoV-2 infection, timing of infection in relation to vaccination affected the kinetics of antibody responses. Residents infected after the third dose showed the highest IgG levels after the fourth dose among all groups (median: 64,328.8 AU/mL), in contrast to residents infected before initiating vaccination with antibody levels similar to those of SARS-CoV-2-naive residents.

CONCLUSIONS

Advanced aged nursing home residents, poor responders in the initial SARS-CoV-2 vaccine series, could achieve sufficient antibody responses after the fourth (second booster) vaccination, comparable to those of younger adults.

SARS-CoV-2 strain-specific anti-spike IgG ELISA utilizing spike protein produced by silkworms

BACKGROUND

A cost-effective and eco-friendly method is needed for the assessment of humoral immunity against SARS-CoV-2 in large populations.

OBJECTIVE

We investigated the performance of an ELISA that uses silkworm-produced proteins to quantify the strain-specific anti-Spike IgG (anti-S IgG) titer.

METHODS

The OD values for the anti-His-tag antibody, a standard material of ELISA quantification, were measured. Correlations between the ELISA for each strain and the Abbott SARS-CoV-2 IgG II Quant assay for the wild type were evaluated with serum samples from nine participants with various infection and vaccination statuses.

RESULTS

Linear dose-responses were confirmed by high coefficients of determination: 0.994, 0.994, and 0.996 for the wild-type, Delta, and Omicron (BA.1) strain assays, respectively. The coefficient of determination for the wild-type and Delta strain assays was high at 0.959 and 0.892, respectively, while the Omicron strain assay had a relatively low value of 0.563. Booster vaccinees showed similar or higher titers against all strains compared to infected persons without vaccination. The Omicron-infected persons without vaccination had lower antibody titers against wild type than did the vaccinated persons.

CONCLUSIONS

This study provides data indicating that the ELISA with silkworm-produced proteins makes it possible to discriminate and quantify the strain-specific anti-S IgG antibody induced by vaccination or infection.

No significant influence of pre-vaccination antipyretic use on specific antibody response to a BNT162b2 vaccine booster against COVID-19

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The influence of antipyretic use before a BNT162b2 booster is of concern.

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Anti-spike IgG titer and adverse reactions were compared by pre/non antipyretic use.

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The geometric mean IgG titer was comparable for the cases and controls.

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The frequency and severity of adverse reactions were also comparable.

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Consistent results were obtained after propensity score matching.

The relation between pre-vaccination antipyretic use and antibody responses to SARS-CoV-2 vaccination has been unclear. We measured the pre- and post-BNT162b2 booster spike-specific IgG titers and recorded antipyretic use and adverse reactions for SARS-CoV-2-naive hospital healthcare workers. The data of 20 cases who used antipyretics within 24 h before vaccination were compared to that of 281 controls. The post-booster geometric mean IgG titers were 15,559 AU/mL (95 % CI, 11,474–21,203) for the cases and 16,850 AU/mL (95 % CI, 15,563–18,243) for the controls (p = 0.622). No significant reduction in the frequency or severity of any of the solicited adverse reactions was found for the cases. Similar results were obtained after adjustment with propensity-score matching for demographic characteristics, baseline IgG titer, and post-vaccination antipyretic use. Antipyretic use within 24 h before vaccination would not affect mRNA COVID-19 vaccine-induced specific antibody responses and that postponement of vaccination due to pre-vaccination antipyretic use would be unnecessary.

Correlation of Postvaccination Fever With Specific Antibody Response to Severe Acute Respiratory Syndrome Coronavirus 2 BNT162b2 Booster and No Significant Influence of Antipyretic Medication

BACKGROUND

A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine booster elicits sufficient antibody responses that protect against coronavirus disease 2019, whereas adverse reactions such as fever have been commonly reported. Associations between adverse reactions and antibody responses have not been fully characterized, nor has the influence of antipyretic use.

METHODS

This is a prospective observational cohort study in Japan, following our prior investigation of BNT162b2 2-dose primary series. Spike-specific immunoglobulin G (IgG) titers were measured for SARS-CoV-2-naive hospital healthcare workers who received a BNT162b2 booster. The severity of solicited adverse reactions, including the highest body temperature, and self-medicated antipyretics were reported daily for 7 days following vaccination through a web-based self-reporting diary.

RESULTS

The data of 281 healthcare workers were available. Multivariate analysis extracted fever after the booster dose (β = .305, P < .001) as being significantly correlated with the specific IgG titers. The analysis of 164 participants with data from the primary series showed that fever after the second dose was associated with the emergence of fever after the booster dose (relative risk, 3.97 [95% confidence interval, 2.48-6.35]); however, the IgG titers after the booster dose were not associated with the presence or degree of fever after the second dose. There were no significant differences in the IgG titers by the use, type, or dosage of antipyretic medication.

CONCLUSIONS

These results suggest an independent correlation between mRNA vaccine-induced specific IgG levels and post-booster vaccination fever, without any significant influence of fever after the primary series. Antipyretic medications for adverse reactions should not interfere with the elevation of specific IgG titers.

Pronounced antibody elevation after SARS-CoV-2 BNT162b2 mRNA booster vaccination in nursing home residents

Background

Infection control during COVID‐19 outbreaks in nursing facilities is a critical public health issue. Antibody responses before and after the third (booster) dose of SARS‐CoV‐2 vaccination in nursing home residents have not been fully characterized.

Methods

This study included 117 individuals: 54 nursing home residents (mean age, 83.8 years; 39 SARS‐CoV‐2‐naive and 15 previously infected) and 63 healthcare workers (mean age, 45.8 years; 32 SARS‐CoV‐2‐naive and 31 previously infected). Anti‐spike (receptor‐binding domain [RBD]) and anti‐nucleocapsid antibody responses to BNT162b2 mRNA vaccination and their related factors were evaluated using pre‐ (shortly and 6 months after the second dose) and post‐booster vaccination samples.

Results

The median anti‐spike (RBD) IgG level in SARS‐CoV‐2‐naive residents 6 months after the second dose was the lowest among the four groups, with a decreasing rate of over 90%. The median rate of increase before and after the third dose in SARS‐CoV‐2‐naive residents was significantly higher than that in SARS‐CoV‐2‐naive healthcare workers (64.1‐ vs. 37.0‐fold, P = 0.003), with the highest level among the groups. The IgG ratio of SARS‐CoV‐2‐naive residents to healthcare workers after the second and third doses changed from one‐fifth (20%) to one‐half (50%). The rate of increase after the third dose in previously infected individuals was three‐ to fourfold, regardless of residents or healthcare workers.

Conclusions

Advanced aged nursing home residents, poor responders in the initial SARS‐CoV‐2 vaccine series, could obtain sufficient antibody responses with the additional booster dose, despite more than 6 months after the second.

Post-vaccination antibody evaluation for nosocomial SARS-CoV-2 delta variant breakthrough infection

Waning humoral immunity after mRNA vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a significant problem for public health. Breakthrough infection in hospitals over several months after vaccination has not been fully characterized, especially against the delta (B.1.617.2) variant. Here, we describe an outbreak in our hospital in September of 2021, mainly through serological evaluation of the breakthrough infection. This retrospective observational study was done at an emergency and acute care hospital with 204 beds and 486 staff members where most staff members (92.6%) had had their second BNT162b2 vaccination by May of 2021. The peri-infection anti-spike RBD protein IgG (anti-S IgG) titers (lowest values between 11 days before and 7 days after onset or diagnosis) of serum samples from the breakthrough-infected persons were quantified. We also logarithmically estimated the anti-S IgG titers during the exposure period in September of uninfected staff members from their samples collected in May and December 2021. Whole-genome sequencing was done on obtained samples. In this outbreak, twelve persons (ten inpatients and two staff members) were diagnosed with SARS-CoV-2 infection by Loop-Mediated Isothermal Amplification (LAMP) or RT-PCR, eight of whom had been vaccinated twice. Peri-infection anti-S IgG titers could be determined in seven of the eight breakthrough cases, with a geometric mean titer (GMT) of 1,034 AU/ml (95% confidence interval [CI], 398 to 2,686). Among 289 uninfected staff members with data from the two sampling points, the GMT of the estimated anti-S IgG titers during the exposure period in 51 staff members, who were working at the outbreak ward and potentially exposed but uninfected, and 238 other unexposed staff members were 1,458 AU/ml (95% CI, 1,196 to 1,777) and 1,628 AU/ml (95% CI, 1,500 to 1,766), respectively. All viruses from the eight samples for which whole-genome sequencing was available were identified as delta variants. Of the infected persons, one remained asymptomatic throughout the course of treatment, and eleven had an illness of mild to moderate severity, including ten who received monoclonal antibody cocktail (Casirivimab/imdevimab) therapy. Measurement and estimation of anti-spike antibody levels after SARS-CoV-2 vaccination would be helpful for evaluating the risk of breakthrough infection and for determining the necessity of booster vaccination.

Relation of fever intensity and antipyretic use with specific antibody response after two doses of the BNT162b2 mRNA vaccine

BACKGROUND

The reactogenicity of BNT162b2 COVID-19 vaccine has been commonly reported and antipyretic medications are often used for mitigating adverse reactions. Possible associations between the reactogenicity events and specific antibody responses have not been fully investigated, nor has the influence of using antipyretics.

METHODS

Serum samples were collected from hospital healthcare workers with no COVID-19 history and the SARS-CoV-2 spike-specific IgG titer after two doses was measured. Degree of solicited adverse reactions in a day, including the highest body temperature, were reported using a self-reporting diary for five days after each dose. The highest body temperature during the five days was divided into three grades (<37.0 °C, 37.0-37.9 °C, or ≥ 38.0 °C). Self-medicated antipyretics were reported using a questionnaire.

RESULTS

The data of 335 participants were available for analysis. Multivariate analysis extracted the fever grade after the second dose (standardized coefficient beta = 0.301, p < 0.0001), female sex (beta = 0.196, p = 0.0014), and age (beta = -0.119, p = 0.0495) as being significantly correlated with the IgG titers. The positive correlation of the fever grade after the second dose with the IgG titers was also observed when analyzed by sex and age. The use of antipyretics did not interfere with the IgG titers irrespective of the fever grade.

CONCLUSIONS

The fever intensity after the second dose was associated with the IgG titer and antipyretic medications may be beneficial to mitigate the suffering from adverse reactions, without interfering with the acquisition of sufficient antibody responses.

Susceptibility of epidemic viruses to neuraminidase inhibitors and treatment-emergent resistance in the Japanese 2019-20 influenza season

OBJECTIVES

To investigate the susceptibility of epidemic influenza viruses to neuraminidase inhibitors (NAIs) and the emergence of resistant viruses after treatment, a prospective, observational study was done in the 2019-20 Japanese influenza season.

METHODS

Influenza viruses were isolated before and twice after treatment, the first at day 5 and the second at day 10. The 50% inhibitory concentrations (IC₅₀s) to oseltamivir, zanamivir, peramivir, and laninamivir were measured and compared with those of 2010-11 to 2018-19 seasons. NA amino acid sequences were analyzed by next generation sequencing (NGS).

RESULTS

The IC₅₀ geometric means of the NAIs for 128 A(H1N1)pdm09, 2 A(H3N2), and 33 B were comparable to those of the previous seasons. Only 2 (1.6%) A(H1N1)pdm09 with significantly high IC₅₀ to oseltamivir were found pretreatment. No A(H3N2) or B had resistance. Treatment-emergent oseltamivir resistance was found in 2 among 33 oseltamivir-treated A(H1N1)pdm09, only at the second follow-up. The NGS indicated a rapid increase in the proportion of H275Y to wild type, from 0% to almost 100% between days 5 and 10.

CONCLUSIONS

These results suggest the continued effectiveness of these NAIs for epidemic influenza in Japan. Treatment-emergent resistant H275Y A(H1N1)pdm09 viruses were detected after oseltamivir treatment, rapidly replacing the wild type.

Reducing influenza virus transmission: the value of antiviral treatment

Prompt antiviral treatment has the potential to reduce influenza virus transmission to close contacts, but rigorous data on the magnitude of treatment effects on transmission are limited. Animal model data indicate that rapid reductions in viral replication after antiviral treatment reduce the risk of transmission. Observational and clinical trial data with oseltamivir and other neuraminidase inhibitors indicate that prompt treatment of household index patients seems to reduce the risk of illness in contacts, although the magnitude of the reported effects has varied widely across studies. In addition, the potential risk of transmitting drug-resistant variants exists with all approved classes of influenza antivirals. A controlled trial examining baloxavir treatment efficacy to reduce transmission, including the risk of transmitting virus with reduced baloxavir susceptibility, is currently in progress. If reduced transmission risk is confirmed, modeling studies indicate that early treatment could have major epidemiologic benefits in seasonal and pandemic influenza.

Virological and clinical outcomes in outpatients treated with baloxavir or oseltamivir: A Japanese multicenter study in the 2019-2020 influenza season

Although the virological and clinical efficacies of baloxavir for influenza and the post-treatment emergence of variant viruses have been reported in clinical trials, its efficacies have not been fully investigated in clinical settings. This prospective, observational investigator-initiated study was conducted during the 2019-2020 Japanese influenza season. In outpatients receiving baloxavir or oseltamivir, nasopharyngeal samples were obtained on day 1 before treatment and on the scheduled days 5 and 10 after treatment. RT-PCR and sequencing were performed to detect polymerase acidic protein (PA) E23X/I38X and neuraminidase (NA) H275Y variants in clinical and cultivated samples. Fever and illness-related symptoms were recorded using self-reporting diaries. Overall, 116 outpatients, 76 treated with baloxavir (34 under 12 years) and 40 with oseltamivir (32 under 12 years), were eligible. Of these, 91 were infected with A (H1N1)pdm09 (78.4%), of which 58 received baloxavir and 33 received oseltamivir. PA variants were detected in clinical (1.7%, 1/58; 3.8%, 1/26 for children under 12 years) and isolated (3.4%, 2/58; 3.8%, 1/26 for children under 12 years) samples obtained on day 5 after baloxavir treatment, but not on day 10. The isolation frequencies of A (H1N1)pdm09 on days 5 and 10 after baloxavir treatment were 5.2% (3/58) and 0.0% (0/58), respectively. Of the three viruses isolated on day 5, two (66.7%, 2/3) were PA I38 T/F variants with reduced baloxavir susceptibility. The isolation frequencies of A (H1N1)pdm09 on days 5 and 10 after oseltamivir treatment were 30.3% (10/33) and 6.1% (2/33), respectively. Only the two viruses isolated on day 10 were NA H275Y variants. The median duration of fever in baloxavir and oseltamivir recipients was 22.3 and 27.5 h, respectively. No patients with PA or NA variants showed prolonged durations of fever. Baloxavir was virologically effective for influenza in the clinical setting of the 2019-2020 Japanese season. Variant emergence after baloxavir treatment was limited to the early post-treatment stage.

Genetic testing and serological screening for SARS-CoV-2 infection in a COVID-19 outbreak in a nursing facility in Japan

Background

The Pandemic of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has critically impacted the spread of infection within nursing facilities. We evaluated the usefulness of genetic and serological tests conducted during a COVID-19 outbreak in a nursing facility in Japan.

Methods

After the first identification of SARS-CoV-2 infection, a comprehensive, facility- and/or unit-wide PCR testing from nasopharyngeal swabs was repeatedly performed in a three-unit facility including 99 residents with dementia and 53 healthcare personnel. Additionally, PCR testing was conducted separately for residents and staff with fever of ≥37.5 °C. Facility-wide serological testing, including rapid kit testing and quantitative assay, was conducted twice over 1 month apart.

Results

A total of 322 PCR and 257 antibody tests were performed. 37 (24.3%) of the 152 individuals (25/99 residents, 25.3%; 12/53 staff, 22.6%) were identified as PCR-positive. Seven residents died with a mortality of 7.1% (7/99). Among the 37 individuals, 10 (27.0%) were asymptomatic at the time of testing. PCR positivity was concentrated on one unit (Unit 1) (20/30 residents, 66.7%; 9/14 staff, 64.3%). The other units showed a limited spread of infection. In unit-wide and separate tests, PCR positivity detection was highly prevalent (22.9 and 44.4%, respectively) in Unit 1, compared with that in the other units. Serological testing identified two additional infected residents with a negative PCR result and showed that no staff was newly identified as infected.

Conclusions

Thorough PCR testing, in combination with comprehensive and separate tests, is critical for managing COVID-19 outbreaks in nursing facilities, particularly, in units considered an epicenter. Serological testing is also beneficial for tracing contacts, confirming the number of infected individuals, and authorizing the termination of the outbreak.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05972-5.

Clinical significance of SARS-CoV-2-specific IgG detection with a rapid antibody kit for COVID-19 patients

Background

The longitudinal observation of the detection of antibody responses to SARS‐CoV‐2 using antibody kits during the clinical course of COVID‐19 is not yet fully investigated.

Objectives

To understand the significance of the detection of anti‐SARS‐CoV‐2 antibodies, particularly IgG, using a rapid antibody kit, during the clinical course of COVID‐19 patients with different severities.

Methods

Sixty‐three serum samples from 18 patients (5 asymptomatic and 13 symptomatic patients) were retrospectively examined using a commercial SARS‐CoV‐2 IgM/IgG antibody kit. PCR positivity of patient samples was also examined as a marker of current SARS‐CoV‐2 infection.

Results

IgG antibodies were detected in all cases in this study. The IgG detection rates reached 100.0% in samples collected on day 13 or later. IgG seropositivity after an initial negative status was observed in 13 patients (3/5 asymptomatic and 10/13 symptomatic cases). Interestingly, the persistence of both PCR and IgG positivity was detected in seven cases, of which three were asymptomatic. The longest overlap duration of the PCR and IgG positivity was 17 days in asymptomatic status.

Conclusions

SARS‐CoV‐2‐specific IgG production can be detected in all infected individuals, using a rapid antibody kit, irrespective of clinical status. However, these findings suggest that, in some infected individuals, particularly those with asymptomatic status, the presence of virus‐specific IgG antibodies does not imply prompt viral clearance.

Baloxavir Marboxil for Prophylaxis against Influenza in Household Contacts

BACKGROUND

Baloxavir marboxil (baloxavir) is a polymerase acidic protein (PA) endonuclease inhibitor with clinical efficacy in the treatment of uncomplicated influenza, including in outpatients at increased risk for complications. The postexposure prophylactic efficacy of baloxavir in the household setting is unclear.

METHODS

We conducted a multicenter, double-blind, randomized, placebo-controlled trial to evaluate the postexposure prophylactic efficacy of baloxavir in household contacts of index patients with confirmed influenza during the 2018-2019 season in Japan. The participants were assigned in a 1:1 ratio to receive either a single dose of baloxavir or placebo. The primary end point was clinical influenza, as confirmed by reverse-transcriptase-polymerase-chain-reaction testing, over a period of 10 days. The occurrence of baloxavir-selected PA substitutions associated with reduced susceptibility was assessed.

RESULTS

A total of 752 household contacts of 545 index patients were randomly assigned to receive baloxavir or placebo. Among the index patients, 95.6% had influenza A virus infection, 73.6% were younger than 12 years of age, and 52.7% received baloxavir. Among the participants who could be evaluated (374 in the baloxavir group and 375 in the placebo group), the percentage in whom clinical influenza developed was significantly lower in the baloxavir group than in the placebo group (1.9% vs. 13.6%) (adjusted risk ratio, 0.14; 95% confidence interval [CI], 0.06 to 0.30; P<0.001). Baloxavir was effective in high-risk, pediatric, and unvaccinated subgroups of participants. The risk of influenza infection, regardless of symptoms, was lower with baloxavir than with placebo (adjusted risk ratio, 0.43; 95% CI, 0.32 to 0.58). The incidence of adverse events was similar in the two groups (22.2% in the baloxavir group and 20.5% in the placebo group). In the baloxavir group, the viral PA substitutions I38T/M or E23K were detected in 10 (2.7%) and 5 (1.3%) participants, respectively. No transmission of these variants from baloxavir-treated index patients to participants in the placebo group was detected; however, several instances of transmission to participants in the baloxavir group could not be ruled out.

CONCLUSIONS

Single-dose baloxavir showed significant postexposure prophylactic efficacy in preventing influenza in household contacts of patients with influenza. (Funded by Shionogi; Japan Primary Registries Network number, JapicCTI-184180.).

Automatic detection of early gastric cancer in endoscopic images using a transferring convolutional neural network

Endoscopic image diagnosis assisted by machine learning is useful for reducing misdetection and interobserver variability. Although many results have been reported, few effective methods are available to automatically detect early gastric cancer. Early gastric cancer have poor morphological features, which implies that automatic detection methods can be extremely difficult to construct. In this study, we proposed a convolutional neural network-based automatic detection scheme to assist the diagnosis of early gastric cancer in endoscopic images. We performed transfer learning using two classes (cancer and normal) of image datasets that have detailed texture information on lesions derived from a small number of annotated images. The accuracy of our trained network was 87.6%, and the sensitivity and specificity were well balanced, which is important for future practical use. We also succeeded in presenting a candidate region of early gastric cancer as a heat map of unknown images. The detection accuracy was 82.8%. This means that our proposed scheme may offer substantial assistance to endoscopists in decision making.

Immune Responses to a Recombinant Glycoprotein E Herpes Zoster Vaccine in Adults Aged 50 Years or Older

Background

The herpes zoster subunit vaccine (HZ/su), consisting of varicella-zoster virus glycoprotein E (gE) and AS01_B Adjuvant System, was highly efficacious in preventing herpes zoster in the ZOE-50 and ZOE-70 trials. We present immunogenicity results from those trials.

Methods

Participants (ZOE-50: ≥50; ZOE-70: ≥70 years of age) received 2 doses of HZ/su or placebo, 2 months apart. Serum anti-gE antibodies and CD4 T cells expressing ≥2 of 4 activation markers assessed (CD4²⁺) after stimulation with gE-peptides were measured in subcohorts for humoral (n = 3293) and cell-mediated (n = 466) immunogenicity.

Results

After vaccination, 97.8% of HZ/su and 2.0% of placebo recipients showed a humoral response. Geometric mean anti-gE antibody concentrations increased 39.1-fold and 8.3-fold over baseline in HZ/su recipients at 1 and 36 months post-dose 2, respectively. A gE-specific CD4²⁺ T-cell response was shown in 93.3% of HZ/su and 0% of placebo recipients. Median CD4²⁺ T-cell frequencies increased 24.6-fold (1 month) and 7.9-fold (36 months) over baseline in HZ/su recipients and remained ≥5.6-fold above baseline in all age groups at 36 months. The proportion of CD4 T cells expressing all 4 activation markers increased over time in all age groups.

Conclusions

Most HZ/su recipients developed robust immune responses persisting for 3 years following vaccination.

Clinical Trials Registration

NCT01165177; NCT01165229.

Medical conditions at enrollment do not impact efficacy and safety of the adjuvanted recombinant zoster vaccine: a pooled post-hoc analysis of two parallel randomized trials

In two pivotal efficacy studies (ZOE-50; ZOE-70), the adjuvanted recombinant zoster vaccine (RZV) demonstrated >90% efficacy against herpes zoster (HZ).Adults aged ≥50 or ≥70 years (ZOE-50 [NCT01165177]; ZOE-70 [NCT01165229]) were randomized to receive 2 doses of RZV or placebo 2 months apart. Vaccine efficacy and safety were evaluated post-hoc in the pooled (ZOE-50/70) population according to the number and type of selected medical conditions present at enrollment.At enrollment, 82.3% of RZV and 82.7% of placebo recipients reported ≥1 of the 15 selected medical conditions. Efficacy against HZ ranged from 84.5% (95% Confidence Interval [CI]: 46.4-97.1) in participants with respiratory disorders to 97.0% (95%CI: 82.3-99.9) in those with coronary heart disease. Moreover, efficacy remained >90% irrespective of the number of selected medical conditions reported by a participant.As indicated by the similarity of the point estimates, this post-hoc analysis suggests that RZV efficacy remains high in all selected medical conditions, as well as with increasing number of medical conditions. No safety concern was identified by the type or number of medical conditions present at enrollment.

In vitro neuraminidase inhibitory concentration (IC50) of four neuraminidase inhibitors in the Japanese 2017-18 season: Comparison with the 2010-11 to 2016-17 seasons

To assess the extent of susceptibility to the four most commonly used neuraminidase inhibitors (NAIs) of the viruses epidemic in the 2017-18 Japanese influenza season, we measured the 50% inhibitory concentration (IC₅₀) for influenza virus isolates from patients and compared them with the results from the 2010-11 to 2016-17 seasons. Viral isolation was done with specimens obtained prior to treatment, and the type and subtype was determined by RT-PCR using type- and subtype-specific primers. The IC₅₀ was determined by a neuraminidase inhibition assay using a fluorescent substrate. A total of 237 virus isolates, 50 A(H1N1)pdm09, 92 A(H3N2), and 95 B were measured. No A(H1N1)pdm09 with highly reduced sensitivity for oseltamivir was found in the 2017-18 season. No isolates with highly reduced sensitivity to the four NAIs have been found for A(H3N2) or B from the 2010-11 to 2017-18 seasons. The geometric mean IC₅₀s of the four NAIs were quite consistent during the eight studied seasons. These results indicate that the sensitivity to the four commonly used NAIs has been maintained.

Consecutive influenza surveillance of neuraminidase mutations and neuraminidase inhibitor resistance in Japan

Background

The large consumption of neuraminidase inhibitors (NAIs) for the treatment of influenza virus infections places Japan at risk of becoming the epicenter of the global spread of NAI‐resistant viruses.

Objective

To clarify NA amino acid mutations of epidemic influenza viruses in Japan and their related NAI resistance.

Methods

A total of 1791 samples, including 396 A/H1N1pdm09, 1117 A/H3N2, and 278 B isolates, were collected to determine of their 50% inhibitory concentration (IC₅₀) values by NAIs (oseltamivir, zanamivir, peramivir, and laninamivir) during the Japanese seasons from 2011‐2012 to 2016‐2017. Then, 380 samples including 49 A/H1N1pdm09, 251 A/H3N2, and 80 B isolates were sequenced for the entire NA genes.

Results

Neuraminidase inhibitor‐resistant A/H1N1pdm09 viruses were detected at a frequency of 1.3% (5/396 isolates) in the epidemic seasons. None of the A/H3N2 and B viruses developed resistance to any of the four NAIs during the six seasons. Only five and 13 AA mutations were detected in the NA catalytic sites of A/H1N1pdm09 and A/H3N2 viruses, respectively. No mutations were observed in the catalytic sites of B viruses. Four of the five mutations in the catalytic sites of A/H1N1pdm09 consisted of H275Y, which was related to high resistance to oseltamivir and peramivir. Most (10/13) of the catalytic site mutations in A/H3N2 were associated with MDCK‐passaged induction (D151G/N). Finally, no mutations related to substantial NAI resistance were detected in the A/H3N2 and B viruses examined.

Conclusion

These findings suggest that the NA catalytic sites of influenza viruses are well preserved. Even in Japan, no spread of NAI‐resistant viruses has been observed, and A/H1N1pdm09 viruses carrying H275Y remain limited.

Duration of fever and other symptoms after the inhalation of laninamivir octanoate hydrate in the 2016/17 Japanese influenza season; comparison with the 2011/12 to 2015/16 seasons

The duration of fever and symptoms after laninamivir octanoate hydrate (laninamivir) inhalation were investigated in the Japanese 2016/17 influenza season and the results were compared with those of the 2011/12 to 2015/16 seasons. A total of 1278 patients were evaluated for the duration of fever and symptoms in the six studied seasons. In the 2016/17 season, the influenza types/subtypes of the patients were 6 A (H1N1)pdm09 (2.9%), 183 A (H3N2) (87.6%), and 20 B (9.6%). The respective median durations of fever for A (H1N1)pdm09, A (H3N2), and B were 38.0, 33.0, and 38.5 h, without significant difference (p = 0.9201), and the median durations of symptoms were 86.5, 73.0, and 99.0 h, with significant difference (p = 0.0342). The median durations of fever and symptoms after laninamivir inhalation were quite consistent for the six studied seasons for A (H1N1)pdm09, A (H3N2), and B, without any significant differences. The percentage of patients with unresolved fever patients displayed a similar pattern through the six studied seasons for all these virus types. There was no significant difference in the duration of fever or symptoms between the Victoria and Yamagata lineages in the 2016/17 season and those of the previous studied seasons. Over the seasons tested, ten adverse drug reactions (ADRs) were reported from 1341 patients. The most frequent ADR was diarrhea and all ADRs were self-resolving and not serious. These results indicate the continuing clinical effectiveness of laninamivir against influenza A (H1N1)pdm09, A (H3N2), and B, with no safety issues.

In vitro neuraminidase inhibitory concentration (IC50) of four neuraminidase inhibitors in the Japanese 2016-17 season: Comparison with the 2010-11 to 2015-16 seasons

To assess the extent of susceptibility to the four most commonly used neuraminidase inhibitors (NAIs) in the viruses epidemic in the 2016-17 Japanese influenza season, we measured the 50% inhibitory concentration (IC₅₀) of these NAIs for influenza virus isolates from patients and compared them with the results from the 2010-11 to 2015-16 seasons. Viral isolation was done with specimens obtained prior to treatment, and the type and subtype was determined by RT-PCR using type- and subtype-specific primers. The IC₅₀ was determined by a neuraminidase inhibition assay using a fluorescent substrate. A total of 276 virus isolates, 6 A (H1N1)pdm09 (2.2%), 249 A (H3N2) (90.2%), and 21 B (7.6%), had the IC₅₀ measured for the four NAIs. B isolates included 11 (52.4%), 9 (42.9%), and one (4.8%) of the Victoria, Yamagata, and undetermined strains, respectively. No A (H1N1)pdm09 with highly reduced sensitivity for oseltamivir was found in the 2016-17 season. No isolate with highly reduced sensitivity to the four NAIs have been found for A (H3N2) or B from the 2010-11 to 2016-17 seasons. No significant trend of increase or decrease was found in the geometric mean IC₅₀s of the four NAIs during the seven studied seasons. These results indicate that the sensitivity to the four commonly used NAIs has been maintained and that any change in the effectiveness of these NAIs would be minute. Common usage of NAIs for patient treatment has not been a driving force in the selection of NAI resistant viruses.

Spread of predominant neuraminidase and hemagglutinin co-mutations in the influenza A/H3N2 virus genome

Genetic variation of influenza neuraminidase (NA), unlike for hemagglutinin (HA), has not been fully characterized. Therefore, we determined the relation between mutations in the NA and HA genome segments of 205 influenza A/H3N2 viruses isolated from patients in Japan during the five seasons from 2010 to 2015. The amino acid (AA) sequences of the NA and HA proteins in these isolates were then determined. In the 2011-2012 season, there was the emergence of isolates with NA and HA sequences containing AA93G (NA93G) and AA278K (HA278K), respectively (24/48 isolates, 50.0%). This was in contrast to NA93D-HA278N being detected exclusively in the previous 2010-2011 season (24/24 isolates, 100.0%). The isolates with the NA93G-HA278K substitutions became predominant in the following 2012-2013 season (95.8%, 46/48 isolates). The NA and HA phylogenetic trees of the 2011-2012 and 2012-2013 seasons were segregated by clades with NA93D-HA278N or NA93G-HA278K. In the subsequent 2013-2014 and 2014-2015 seasons, the strong relationship between NA93D-HA278N and NA93G-HA278K observed in the previous seasons, was no longer present and NA93G-HA278N (33/52 isolates, 63.5% in the 2014-2015 season) became predominant. In addition, the clades within the NA and HA trees could no longer be segregated based on NA AA93 and HA AA278. These findings suggest that the co-mutation of NA and HA AA sequences is present and may contribute to the formation of an epidemic lineage.

Is seasonal vaccination a contributing factor to the selection of influenza epidemic variants?

Influenza A/H3N2 viruses are the most common and virulent subtypes for humans. Antigenic drift, changes in antigenicity through the accumulation of mutations in the hemagglutinin (HA) gene is chiefly responsible for the continuing circulation of A/H3N2 viruses, resulting in frequent updates of vaccine strains based on new variant analyses. In humans, these drift-related mutations are considered to be primarily caused by the immune pressure elicited by natural infection. Whether or not the immune pressure elicited by vaccination (vaccine pressure) can have a certain effect on drift-related mutations is unclear. Recently, our findings suggested the possible effect of vaccine pressure on HA mutations by directly comparing amino acid differences from the corresponding vaccine strains between isolates from vaccinated and unvaccinated patients. It is possible that influenza vaccine pressure selects variants genetically distant from the vaccine strains. Considering the effect of vaccine pressure on HA mutations would contribute to further understanding the mechanism of antigenic drift, which would be helpful for predicting future epidemic viruses.

A cross sectional survey measuring sero-incidence of pertussis infection among Japanese junior and senior high school students in 2013 and 2014

Pertussis in adolescents has been increasingly documented in recent years, but diagnosis from the clinical symptoms is difficult. Serological diagnosis with IgG antibody to pertussis toxin (IgG PT) is useful for detecting pertussis cases in this population. However, no serological criterion for recent infection has been fully validated and large-scale, longitudinal serological data among Japanese junior and senior high school students are lacking. Paired serum samples of 3243 junior and senior high school students, collected in 2013 and 2014, were analyzed for IgG PT and its relationship to possible risk factors. Regression analysis showed an average decrease of 35% in IgG PT between 2013 and 2014. In 2013, 4.4% of the students showed IgG PT levels ≥100EU/mL, as did 3.7% in 2014. The seroincidence, defined as [IgG PT] change from <100 in 2013 to ≥100EU/mL in 2014, was 10.3 cases per 1000 person-years. A 4-fold rise in IgG PT was seen in 2.1% of the students, with significant differences between schools and significant correlations to two risk factors, "over 2weeks coughing" and "exposure to a person with over 2weeks coughing". A substantial number of students had IgG PT ≥100EU/mL despite the observed 35% yearly decrease in IgG PT level. The local foci of ≥4-fold IgG PT increase in specific schools suggests the persistent circulation of B. pertussis in Japanese adolescents. The results also support a "≥4-fold rise in IgG PT" as a useful component of the sero-epidemiological surveillance for pertussis.

Age-Specific Profiles of Antibody Responses against Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is one of the most prevalent causative agents of lower respiratory tract infections worldwide, especially in infants around 3 to 4 months old. Infants at such a young age have maternally-transferred passive antibodies against RSV but do not have active immune systems efficient enough for the control of RSV infection. In order to elucidate age-specific profiles of immune responses against RSV protection, antibody responses were examined by using blood samples in both acute and convalescent phases obtained from child patients and adult patients. In addition to the serum neutralization activity, antibody responses to the RSV fusion protein (F protein) were dissected by analyzing levels of total IgG, IgG subclasses, the binding stability, and the levels of antibody for the neutralization epitopes. It was suggested that children's antibody responses against RSV are matured over months and years in at least 5 stages based on 1) levels of the neutralization titer and IgG3 for F protein in the convalescent phase, 2) geometric mean ratios of the neutralization titers and levels of IgG1 and IgG2 for F protein in the convalescent phase compared to those levels in the acute phase, 3) the affinity maturation of IgG for F protein and the cross reactivity of IgG for RSV glycoproteins of groups A and B, 4) levels of neutralization epitope-specific IgG, and 5) augmentation of overall antibody responses due to repetitive RSV infection.

•

Children's antibody responses against RSV are matured over months and years in at least 5 stages.

•

Age-specific profiles of antibody responses after RSV infection are proposed.

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The profile of IgG3 specific to F protein reflects infants' own antibody response after RSV infection.

In this study, antibody responses to respiratory syncytial virus (RSV) were evaluated by quantitative and qualitative multivariate analyses of acute and convalescent sera from patients infected with RSV. The results suggested that the profiles of antibody responses after RSV infections are delineated by independent factors such as the development of children's immune system and the natural infection with RSV in the presence or absence of maternal antibodies.

Effect of seasonal vaccination on the selection of influenza A/H3N2 epidemic variants

The effect of vaccination on the dynamics of influenza virus variants remains largely unknown in humans, unlike in poultry. In this study, we compared influenza hemagglutinin (HA) gene sequences isolated from vaccinated and unvaccinated populations with the yearly vaccine strains. In total, 181 influenza A/H3N2 virus samples isolated from 82 vaccinated and 99 unvaccinated patients (2011-15, four Japanese influenza seasons) were genetically analyzed using a next-generation sequencer. Amino acid (AA) differences from corresponding vaccine strains were found in 74 of 329 HA1 sites. There was a maximum of four AA differences within the epitopes in the former three seasons (2011-14) and fifteen in the latter season (2014-15). Deviation to a greater number of AA differences was found more significantly in the isolates from vaccinated patients as compared to unvaccinated patients (P=0.0005 in 2011-14; P=0.0096 in 2014-15). AA difference rates within epitopes were also significantly higher in the isolates from vaccinated patients than from unvaccinated patients (2.64% vs. 2.14% for 2011-14, P=0.033; 7.78% vs. 6.59% for 2014-15, P=0.058). The AA differences at seven sites (48I-278K, 128A-142G, 145S, 158K, and 193S) became dominant in the following seasons. In all of these sites, the dominance was retained during the mismatch of isolates with the vaccine strains and was lost after vaccine match. Our data suggest that in humans, immune pressure induced by vaccination works to select influenza variants genetically distant from vaccine strains.

Duration of fever and other symptoms after the inhalation of laninamivir octanoate hydrate for influenza treatment; comparison among the four Japanese influenza seasons from 2011-2012 to 2014-2015

The duration of fever and other symptoms as markers of the clinical effectiveness of laninamivir octanoate hydrate (laninamivir) were investigated in the Japanese 2014-2015 influenza season and the results were compared with those of the previous three seasons, 2011-2012 to 2013-2014. From these four seasons, the data of 636 influenza A(H3N2) and 128 influenza B patients was available for analysis. No significant difference was found in their baseline characteristics. The median duration of fever for all A(H3N2) patients ranged from 32.0 to 41.0 h. The duration of fever in the 2014-2015 season was significantly shorter than that in the 2012-2013 and 2013-2014 seasons (p = 0.0204 and 0.0391, respectively), but the differences were within nine hours. The median duration of symptoms for A(H3N2) ranged from 80.0 to 89.0 h, with no significant difference among the four seasons (p = 0.2222). The median duration of fever for B patients ranged from 43.0 to 50.0 h, with no significant difference among the four seasons. The duration of the symptoms for B varied by season, but no significant difference was found among the four seasons. Over the four seasons, 44 adverse events were reported from among 921 patients, with all resolving without treatment. These results indicate the continuing effectiveness of laninamivir against influenza A(H3N2) and B, with no safety issues. It is unlikely that the clinical use of laninamivir has caused viral resistance in the currently epidemic viruses.

Long-acting Neuraminidase Inhibitor Laninamivir Octanoate as Post-exposure Prophylaxis for Influenza

BACKGROUND

A single administration of laninamivir octanoate, a long-acting neuraminidase inhibitor, has been proven to be effective in the treatment of influenza but not for post-exposure prophylaxis.

METHODS

We conducted a double-blind, multicenter, randomized, placebo-controlled study to determine if a single administration of laninamivir octanoate 40 mg was superior to placebo for post-exposure prophylaxis. Eligible participants who had cohabited with an influenza patient within 48 hours of symptom onset were randomly assigned (1:1:1) to 1 of 3 groups: 40 mg of laninamivir octanoate single administration (LO-40SD), 20 mg of laninamivir octanoate once daily for 2 days (LO-20TD), or placebo. The primary efficacy endpoint was the proportion of participants who developed clinical influenza (defined as influenza virus positive, an axillary temperature >37.5°C, and at least 2 symptoms) over a 10-day period.

RESULTS

A total of 803 participants were enrolled, with 801 included in the primary analysis. The proportions of participants with clinical influenza were 4.5% (12/267), 4.5% (13/269), and 12.1% (32/265) in the LO-40SD, LO-20TD, and placebo groups, respectively. A single administration of laninamivir octanoate 40 mg significantly reduced the development of influenza compared with placebo (P = .001). The relative risk reductions compared with the placebo group were 62.8% and 63.1% for the LO-40SD and LO-20TD groups, respectively. The incidence of adverse events in the LO-40SD group was similar to that of the LO-20TD and placebo groups.

CONCLUSIONS

A single administration of laninamivir octanoate was effective and well tolerated as post-exposure prophylaxis to prevent the development of influenza.

CLINICAL TRIALS REGISTRATION

JapicCTI-142679.

[Neuraminidase Amino Acid Sequences of Influenza A/H3N2 and B Viruses Isolated from Influenza Patients in the 2014/15 Japanese Influenza Season]

BACKGROUND

Neuraminidase (NA) is a surface protein essential for influenza virus replication. NA inhibitors are commonly used for the treatment of influenza patients in Japan. Several mutations that reduce the effect of NA inhibitors have been reported. We sequenced the whole NA segment of isolated virus from influenza patients and investigated the relation between the NA amino acid sequence and the 50％ inhibitory concentration (IC_50) of four NA inhibitors.

MATERIALS AND METHODS

Forty A/H3N2 and 19 B influenza virus isolated from patients in the 2014/15 influenza season were analyzed. The IC_50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. Viral RNA was amplified by RT-PCR and the genome was sequenced using a next generation sequencer. The deduced amino acid sequences were analyzed.

RESULTS

There was no AA change in the NA catalytic site of the A/H3N2 and B viruses isolated in the 2014-15 influenza season. There was no significant relation between the NA amino acids and the IC_50 of the four NA inhibitors for A/H3N2 or B viruses.

CONCLUSION

The catalytic site of NA was highly conserved for these A/H3N2 and B viruses. No emergence of NA amino acid mutations related to the sensitivity of the four currently used NA inhibitors was observed.

Clinical outcome of laninamivir octanoate hydrate for influenza in the 2013-2014 Japanese season

The clinical outcome of laninamivir octanoate hydrate (laninamivir) in the Japanese 2013-2014 influenza season was investigated. A total of 235 patients were enrolled, of whom 222 were evaluated for the duration of fever and other symptoms. The types/subtypes were 101 A(H1N1)pdm09 (45.5%), 37 A(H3N2) (16.7%), and 84 B (37.8%). The median durations of fever were 32.0, 41.0, and 50.0 h, and the median durations of symptoms were 74.5, 85.0, and 95.0 h for A(H1N1)pdm09, A(H3N2), and B, respectively. The differences among the three groups were not statistically significant. There was no significant difference in the duration of fever or symptoms between patients under 10 and 10 years or over. The median durations of fever were 46.0 and 58.0 h and the median durations of symptoms were 95.0 and 77.0 h for the Yamagata and Victoria lineages, respectively. The virus positive rates at day 5 were significantly different at 31.5% (28/89), 12.1% (4/33), and 34.7% (26/75) for the three type/subtypes, respectively. The virus positive rates for A(H1N1)pdm09 and B were significantly higher for the patients under 10 years than for the patients 10 years or older. (p = 0.0379 and 0.0320, respectively). No significant increase was found between the IC(50) of days 1 and 5. No adverse drug reactions associated with laninamivir were reported. These results indicate the continuing clinical utility of laninamivir against influenza, irrespective of the virus type/subtype or lineage, and that it is unlikely that the clinical use of laninamivir will lead to selection of resistant virus.

Continued effectiveness of laninamivir octanate hydrate for influenza treatment in Japan: comparison between the 2011-2012 and 2012-2013 influenza seasons

The clinical effectiveness of Laninamivir octanoate hydrate (laninamivir) was investigated in the Japanese 2012-2013 influenza season for comparison with that of the Japanese 2011-2012 influenza season. A total of 235 patients were enrolled, of whom 210 were evaluated for the duration of fever and other symptoms. The median durations of fever for A(H3N2) were 32.0 and 38.0 h and the median durations of symptoms for the A(H3N2) were 102.0 and 84.0 h for patients aged under 10 and 10 years or older, respectively. All four influenza B patients were 10 years or older, and their median duration of fever was 43.0 h and the median duration of symptoms was 71.0 h. There was no significant difference in the duration of fever or symptoms between the two seasons. The rates of patients A(H3N2) virus positive at day 5 were 37.2% (16/43) and 12.8% (18/141) for those aged under 10 years and 10 years or older, respectively. The virus positive rate was significantly higher for the patients under 10 years than for the patients aged 10 years or older (p < 0.0001). No significant change in IC50 value was found between days 1 and 5. Adverse drug reactions were reported by 2 of the 231 patients (0.87%), but neither was serious. These results suggest that laninamivir continued to be effective against influenza A(H3N2) with no safety issues and that it is unlikely that the clinical use of laninamivir will lead to virus resistance.

[Analysis of the Neuraminidase Amino Acid Sequences of Influenza A/H1N1pdm09, A/H3N2, and B Viruses Isolated from Influenza Patients in the 2013/14 Japanese Influenza Season]

BACKGROUND

Neuraminidase (NA) is an essential surface protein for influenza virus replication. NA inhibitors are commonly used for the treatment of influenza patients in Japan. Several mutations that reduce the effect of NA inhibitors have been reported. We sequenced the whole NA segment of isolated virus from influenza patients and investigated the relation between the NA amino acid sequence and the 50% inhibitory concentration (IC50) of four NA inhibitors.

MATERIALS AND METHODS

A total of 20 viruses that showed high or low IC50 of NA inhibitors were selected from A/H1N1pdm09, A/H3N2, and B isolates from the viruses isolated from patients in the 2013-14 influenza season. Viral RNA was extracted and RT-PCR was done. The amplified genome was sequenced using a next generation sequencer", and the deduced amino acid sequences were analyzed.

RESULTS

Two A/H1N1pdm09 viruses that showed very high IC50 for oseltamivir (150 nM and 130 nM) contained the H275Y mutation. Otherwise, no significant relation was found between the NA amino acids and the IC50 of the four NA inhibitors. There was no significant relation between the NA amino acids and the IC50 of the four NA inhibitors for A/H3N2 viruses. The B viruses that showed a high IC50 for oseltamivir and laninamivir shared some amino acids. The B viruses that showed a high IC50 of zanamivir and peramivir also shared some amino acids. They were different from the shared amino acids found for oseltamivir and laninamivir.

CONCLUSION

The previously reported H275Y mutation that causes oseltamivir resistance was found in the two A/H1N1pdm09 viruses that showed a very high IC50 for oseltamivir. No additional NA amino acid sequences related to the IC50 of the four NA inhibitors was found. The meaning of the shared amino acids among B viruses that showed a high IC50 would be an interesting target for further investigation.

In vitro neuraminidase inhibitory activity of four neuraminidase inhibitors against clinical isolates of the influenza virus circulating in the Japanese 2013-2014 season

To assess the extent of viral resistance, we measured the 50% inhibitory concentration (IC50) of neuraminidase inhibitors (NAIs) for the influenza virus isolates in the 2013-2014 influenza season and compared the results to those of the 2010-2011 to 2012-2013 influenza seasons. Viral isolation was done with specimens obtained prior to treatment, and the type and subtype of influenza was determined by RT-PCR using type- and subtype-specific primers. The IC50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. A total of 327 influenza viruses were isolated: 172 influenza A(H1N1)pdm09 (52.6%), 49 A(H3N2) (15.0%), and 106 B (32.4%). Numbers of Victoria and Yamagata lineage isolates were 36 and 70, respectively. Two A(H1N1)pdm09 isolates showed a high IC50 for oseltamivir (130 and 150 nM) exceeding by 100 times the geometric mean of the IC50 of oseltamivir for A(H1N1)pdm09 isolates (0.76 nM). No isolate showed a very high IC50 for A(H3N2) or B. The IC50 of the NAIs except for oseltamivir for A(H1N1) pdm09 were significantly higher than those of the 2010-2011 season (P < 0.05). The IC50 of all four NAIs for A(H3N2) were significantly lower than those of the 2012-2013 season (P < 0.001). The IC50 of the NAIs for B except for oseltamivir were significantly lower than those of the 2012-2013 season (P < 0.001). Although there are some isolates that show highly reduced sensitivity to oseltamivir among A(H1N1)pdm09 isolates, the currently epidemic influenza A(H1N1)pdm09, A(H3N2) and B viruses are susceptible to all four NAIs with no trend toward decreased sensitivity.

[Analysis of influenza A/H3N2 neuraminidase genes obtained from influenza patients in the 2011/12 and 2012/13 seasons in Japan]

BACKGROUND

Influenza virus has neuraminidase (NA), a surface protein with enzymatic activity that is essential for virus replication. Mutation may affect the effectiveness of NA inhibitors that are used for the treatment of influenza patients. In this study, we determined the NA gene sequences from the clinical isolates of influenza patients to examine the chronological genetic changes and the relation to drug susceptibility.

METHODS

For 96 A/H3N2 virus isolates the 50% inhibitory concentration (IC50) (48 each from the 2011-12 and 12-13 influenza seasons) was measured. RT-PCR was done with extracted viral RNA, followed by nucleotide sequencing.

RESULTS

One putative amino acid mutation, D151N, was found in an NA activity-related cite in five of ninety-six tested isolate. The mutation did not affect the IC50 value. The mutations identified at amino acid positions 387 and 400 were statistically correlated with an increased IC50 value, although the change was less than ten times, suggesting no significant difference in the clinical effectiveness. A small number .of isolates showed mutation in the T and/or B cell epitope region of NA.

CONCLUSION

No mutation that affected the IC50 value or effectiveness of NAIs was detected. Antigenic mutations of NA, which influence the selection of epidemic strains, were not determined. Continuous observation will be necessary to further clarify the genetic features of NA.

In vitro neuraminidase inhibitory activity of four neuraminidase inhibitors against clinical isolates of influenza virus in the Japanese 2012-2013 season

The neuraminidase inhibitors (NAIs) oseltamivir phosphate (Tamiflu(®)), zanamivir (Relenza(®)), laninamivir octanoate (Inavir(®)), and peramivir (Rapiacta(®)) have been available for the treatment of influenza in Japan since 2010. The emergence of resistant virus to any of the NAIs is a great concern for influenza treatment. To assess the extent of viral resistance, we measured the 50% inhibitory concentration (IC50) of each NAI for influenza virus isolates in the 2012-2013 influenza season and compared the results to those of the 2010-2011 and 2011-2012 influenza seasons. Viral isolation of specimens obtained prior to treatment was done using Madine-Darby canine kidney cells, and the type and subtype of influenza, A(H1N1)pdm09, A(H3N2), or influenza B, was determined by RT-PCR using type- and subtype-specific primers. The IC50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. A total of 329 influenza viruses were isolated:5 influenza A(H1N1)pdm09 (1.5%), 316 influenza A(H3N2) (96.1%), and 8 influenza B (2.4%). No isolate showed an IC50 value exceeding 50 nM for any of the neuraminidase inhibitors. The IC50 values for A(H3N2) and B were similar to those of the 2010-2011 and 2011-2012 seasons. No isolate showed an increased IC50 value for A(H1N1)pdm09. These results indicate that the currently epidemic influenza viruses are susceptible to all four neuraminidase inhibitors, with no trend for IC50 values to increase at present.

[Comparison of the kinetics of granulocytes and lymphocytes between influenza A/H1N1/pdm09 and seasonal influenza A]

Peripheral blood tests are performed for the differentiation of febrile diseases, and are useful for diagnosing and determining the effectiveness of treatment in bacterial infections. However, their use for viral infections has not been well-investigated, nor do any clear views exist regarding their use with viral infections. We retrospectively investigated the results of routine peripheral blood tests for febrile diseases (differential leukocyte count and C-reactive protein (CRP)) performed in 1162 patients between the 2004/05 and 2009/10 influenza seasons, and identified the characteristic findings of influenza, along with the differences between cases of seasonal influenza A (including H3N2 and H1N1; hereafter, seasonal A; n = 614) and pandemic influenza (H1N1) 2009 seen during the 2009/10 influenza season (hereafter, A/H1N1/pdm09; n=548). The differential leukocyte count varies with age; therefore, analysis was performed by adjusting for the age of all patients using a generalized additive model (GAM). Increased granulocytes and decreased lymphocytes were confirmed during the initial stage of influenza infection, followed by inversion to decreased granulocytes and increased lymphocytes. The granulocyte count was significantly lower in A/H1N1/pdm09 compared to seasonal A, with levels 0.93- and 0.82-fold relative to seasonal A before and after treatment, respectively. The lymphocyte count was 1.12- to 1.30-fold greater in A/H1N1/pdm09 compared to seasonal A both before and after treatment, indicating significantly higher levels in A/H1N1/pdm09. CRP levels peaked 24-36 h after onset, with peaks of 0.88mg/dL for A/H1N1/pdm09 and 1.53 mg/dL for seasonal A. Peripheral blood counts change due to factors such as the time course of the disease, onset of complications, modification resulting from treatment, and side effects of pharmacotherapies. We report the present findings because we consider an understanding of the changes and kinetics of differential leukocyte counts in peripheral blood inherent to influenza to be important for diagnosis (particularly for the decision of doing rapid diagnosis test) and to promote recognition of the onset of complications and side effects during the course.

Licorice flavonoid oil reduces total body fat and visceral fat in overweight subjects: A randomized, double-blind, placebo-controlled study

SUMMARY

OBJECTIVES

To evaluate effects of licorice flavonoid oil (LFO) on total body fat and visceral fat together with body weight, body mass index (BMI) and safety parameters in overweight subjects.

METHODS

In this randomized, double-blind, placebo-controlled study, moderately overweight participants (56 males, 28 females, BMI 24-30 kg/m(2)) were assigned to four groups receiving a daily dose of either 0 (placebo), 300, 600, or 900 mg of LFO. Total body fat mass was measured by dual-energy X-ray absorptiometry (DXA) and visceral fat area by abdominal computed tomography (CT) scan at baseline and after 8 weeks of LFO ingestion. Body weight, BMI, and blood samples were examined at baseline and after 4 and 8 weeks of LFO ingestion.

RESULTS

Although caloric intake was similar in all four groups, total body fat mass decreased significantly in the three LFO groups after 8 weeks of ingestion. LFO (900 mg/day) resulted in significant decreases from baseline levels in visceral fat area, body weight, BMI, and LDL-cholesterol. No significant adverse effects were observed.