Real-time RT-PCR assays for discriminating influenza B virus Yamagata and Victoria lineages

A comprehensive review of influenza B virus, its biological and clinical aspects

Influenza B virus (IBV) stands as a paradox, often overshadowed by its more notorious counterpart, influenza A virus (IAV). Yet, it remains a captivating and elusive subject of scientific inquiry. Influenza B is important because it causes seasonal flu outbreaks that can lead to severe respiratory illnesses, including bronchitis, pneumonia, and exacerbations of chronic conditions like asthma. Limitations in the influenza B virus's epidemiological, immunological, and etiological evolution must be addressed promptly. This comprehensive review covers evolutionary epidemiology and pathogenesis, host-virus interactions, viral isolation and propagation, advanced molecular detection assays, vaccine composition and no animal reservoir for influenza B virus. Complex viral etiology begins with intranasal transmission of influenza B virus with the release of a segmented RNA genome that attacks host cell machinery for transcription and translation within the nucleus and the release of viral progeny. Influenza B virus prevalence in domesticated and wild canines, sea mammals, and birds is frequent, yet there is no zoonosis. The periodic circulation of influenza B virus indicates a 1-3-year cycle for monophyletic strain replacement within the Victoria strain due to frequent antigenic drift in the HA near the receptor-binding site (RBS), while the antigenic stability of Yamagata viruses portrays a more conservative evolutionary pattern. Additionally, this article outlines contemporary antiviral strategies, including pharmacological interventions and vaccination efforts. This article serves as a resource for researchers, healthcare professionals, and anyone interested in the mysterious nature of the influenza B virus. It provides valuable insights and knowledge essential for comprehending and effectively countering this viral foe, which continues to pose a significant public health threat.

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.

No association between inactivated influenza vaccination and influenza viral load at diagnosis among young Japanese children: An observational study of the 2013/2014 through 2017/2018 influenza seasons

BACKGROUND

The association between inactivated influenza vaccination and viral load in young children remains unclear.

METHODS

During the 2013/2014 to 2017/2018 influenza seasons in Japan, children under 6 years of age with pre-defined influenza-like illness and influenza-positive status by real-time RT-PCR were recruited at pediatric clinics for this observational study. Influenza viral load was measured for the most predominant subtype/lineage in each season. Using median dichotomized viral load as an outcome, a multilevel logistic regression model was applied to estimate the multivariable adjusted odds ratio (MOR) and 95% confidence interval (CI) for higher viral load.

RESULTS

A total of 1,185 influenza-positive children were analyzed. The median log10 viral load copy number (copies per milliliter) was 5.5 (interquartile range, 4.6 to 6.1) and did not differ by vaccination status: 5.5 for unvaccinated, 5.7 for one dose, and 5.5 for two doses (p = 0.67). The MOR of vaccinated (one or two doses) versus unvaccinated children was 1.19 (95% CI: 0.86-1.64). Other factors showing significant associations with higher viral load were positive results for A(H1N1)pdm09 and A(H3N2) in comparison with B/Yamagata. The respective MORs were 3.25 (95% CI: 2.28-4.64) and 1.81 (95% CI: 1.32-2.49). Significantly elevated MORs against higher viral load were also observed for higher body temperature at influenza diagnosis and shorter duration from fever onset to specimen collection.

CONCLUSION

No association was observed between inactivated-influenza vaccination and viral load at influenza-positive diagnosis. Influenza subtype/lineage, body temperature, and time elapsed since fever onset were significantly associated with viral load.

Protein glycosylation in urine as a biomarker of diseases

Human body fluids have become an indispensable resource for clinical research, diagnosis and prognosis. Urine is widely used to discover disease-specific glycoprotein biomarkers because of its recurrently non-invasive collection and disease-indicating properties. While urine is an unstable fluid in that its composition changes with ingested nutrients and further as it is excreted through micturition, urinary proteins are more stable and their abnormal glycosylation is associated with diseases. It is known that aberrant glycosylation can define tumor malignancy and indicate disease initiation and progression. However, a thorough and translational survey of urinary glycosylation in diseases has not been performed. In this article, we evaluate the clinical applications of urine, introduce methods for urine glycosylation analysis, and discuss urine glycoprotein biomarkers. We emphasize the importance of mining urinary glycoproteins and searching for disease-specific glycosylation in various diseases (including cancer, neurodegenerative diseases, diabetes, and viral infections). With advances in mass spectrometry-based glycomics/glycoproteomics/glycopeptidomics, characterization of disease-specific glycosylation will optimistically lead to the discovery of disease-related urinary biomarkers with better sensitivity and specificity in the near future.

Influence of Prior Influenza Vaccination on Current Influenza Vaccine Effectiveness in Children Aged 1 to 5 Years

BACKGROUND

Although annual influenza vaccination is an important strategy used to prevent influenza-related morbidity and mortality, some studies have reported the negative influence of prior vaccination on vaccine effectiveness (VE) for current seasons. Currently, the influence of prior vaccination is not conclusive, especially in children.

METHODS

We evaluated the association between current-season VE and prior season vaccination using a test-negative design in children aged 1-5 years presenting at nine outpatient clinics in Japan during the 2016/17 and 2017/18 influenza seasons. Children with influenza-like illness were enrolled prospectively and tested for influenza using real-time RT-PCR. Their recent vaccination history was categorized into six groups according to current vaccination doses (0/1/2) and prior vaccination status (unvaccinated = 0 doses/vaccinated = 1 dose or 2 doses): (1) 0 doses in the current season and unvaccinated in prior seasons (reference group); (2) 0 doses in the current season and vaccinated in a prior season; (3) 1 dose in the current season and unvaccinated in a prior season; (4) 1 dose in the current season and vaccinated in a prior season; (5) 2 doses in the current season and unvaccinated in a prior season, and (6) 2 doses in the current season and vaccinated in a prior season.

RESULTS

A total of 799 cases and 1196 controls were analyzed. The median age of the subjects was 3 years, and the proportion of males was 54%. Overall, the vaccination rates (any vaccination in the current season) in the cases and controls were 36% and 53%, respectively. The VEs of the groups were: (2) 29% (95% confidence interval: -25% to 59%); (3) 53% (6% to 76%); (4) 70% (45% to 83%); (5) 56% (32% to 72%), and (6) 61% (42% to 73%). The one- and two-dose VEs of the current season were significant regardless of prior vaccination status. The results did not differ when stratified by influenza subtype/lineage.

CONCLUSION

Prior vaccination did not attenuate the current-season VE in children aged 1 to 5 years, supporting the annual vaccination strategy.

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.

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.

A newly developed real-time PCR assay for discriminating influenza B virus Yamagata and Victoria lineages

Currently, two distinct lineages of influenza B virus (IBV), B/Victoria and B/Yamagata lineage, have been co-circulating in human beings. Assessment of the prevalent lineage is key for the recommendation of the seasonal influenza vaccine composition and the evaluation of its efficacy. In this study, a multiplex qRT-PCR assay for the discrimination of the IBV lineages was designed based on the genetic differences of the hemagglutinin genes between B/Yamagata and B/Victoria lineages. The assay was highly specific and able to discriminate the lineages of IBV without any non-specific reaction against other influenza A viruses. The detection limit of the assay was determined to be 10 genome-equivalent copies and 2.8 × 10-2 50% tissue culture infectious doses (TCID50 ) of live IBV per reaction. Moreover, our assay was able to discriminate the lineages of IBVs in clinical samples with 100% accuracy, when compared with pyrosequencing. Our results indicate that this assay may represent an update of the existing qRT-PCR assays and will be of great use for the rapid and accurate diagnosis and surveillance of the circulating IBVs.

Clinical evaluation of fully automated molecular diagnostic system "Simprova" for influenza virus, respiratory syncytial virus, and human metapneumovirus

Influenza virus, respiratory syncytial virus, and human metapneumovirus commonly cause acute upper and lower respiratory tract infections, especially in children and the elderly. Although rapid antigen detection tests for detecting these infections have been introduced recently, these are less sensitive than nucleic acid amplification tests. More recently, highly sensitive point-of-care testings (POCTs) have been developed based on nucleic acid amplification tests, which are easy to use in clinical settings. In this study, loop-mediated isothermal amplification (LAMP)-based POCT “Simprova” to detect influenza A and B viruses, respiratory syncytial virus, and human metapneumovirus was developed. Simprova system is fully automated and does not require skilled personnel. In addition, positive results can be achieved faster than with PCR. In this study, the accuracy of the POCT was retrospectively analyzed using 241 frozen stocked specimens. Additionally, the usability of the Simprova at clinical sites was assessed in a prospective clinical study using 380 clinical specimens and compared to those of real-time PCR and rapid antigen detection test. The novel LAMP-based POCT demonstrated high sensitivity and specificity in characterizing clinical specimens from patients with influenza-like illnesses. The Simprova is a powerful tool for early diagnosis of respiratory viral infections in point-of-care settings.

Neurogenic pulmonary edema following febrile status epilepticus in a 22-month-old infant with multiple respiratory virus co-detection: a case report

BACKGROUND

Neurogenic pulmonary edema is a rare but serious complication of febrile status epilepticus in children. Comprehensive screening for viral pathogens is seldomly performed in the work-up of febrile children.

CASE PRESENTATION

A 22-month-old girl presented with her first episode of febrile status epilepticus, after which she developed acute pulmonary edema and respiratory failure. After the termination of seizure activity, the patient was intubated and managed on mechanical ventilation in the emergency room. The resolution of respiratory failure, as well as the neurological recovery, was achieved 9 h after admission, and the patient was discharged 6 days after admission without any complications. Molecular biological diagnostic methods identified the presence of human coronavirus HKU1, influenza C virus, and human parainfluenza virus 2 from the patient's nasopharyngeal specimens.

CONCLUSIONS

Neurogenic pulmonary edema following febrile status epilepticus was suspected to be the etiology of our patient's acute pulmonary edema and respiratory failure. Timely seizure termination and rapid airway and respiratory intervention resulted in favorable outcomes of the patient. Molecular biological diagnostic methods identified three respiratory viruses; however, their relevance and association with clinical symptoms remain speculative.

In vitro neuraminidase inhibitory concentration (IC50) of four neuraminidase inhibitors in the Japanese 2018-19 season: Comparison with the 2010-11 to 2017-18 seasons

To assess the extent of susceptibility to the four most commonly used neuraminidase inhibitors (NAIs) of the epidemic viruses in the 2018-19 Japanese influenza season, we measured the 50% inhibitory concentration (IC₅₀) of four NAIs, oseltamivir, zanamivir, peramivir, and laninamivir, for influenza virus isolates from patients and compared them with the results from the 2010-11 to 2017-18 seasons. 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, 51 A(H1N1)pdm09, 125 A(H3N2), and one B, were measured in the 2018-19 season and the geometric mean IC₅₀s of the four NAIs were quite comparable to the previous eight studied seasons. No A(H1N1)pdm09 with highly reduced sensitivity for oseltamivir was found in the 2018-19 season prior to drug administration, although such A(H1N1)pdm09 were found in two, two, and two samples in the 2010-11, 2013-14, and 2015-16 seasons, respectively. No isolates with highly reduced sensitivity to the four NAIs were found for A(H3N2) or B through the 2010-11 to 2018-19 seasons. Among 18 samples with A(H1N1)pdm09 virus isolated after NAI administration, highly reduced sensitivity to oseltamivir and peramivir was detected from one of the five patients treated with oseltamivir. These results suggest that the sensitivity to the four commonly used NAIs has been maintained, although viruses with highly reduced sensitivity to oseltamivir and peramivir have emerged in some adult patients treated with oseltamivir.

Rapid detection of an I38T amino acid substitution in influenza polymerase acidic subunit associated with reduced susceptibility to baloxavir marboxil

Background

The novel cap‐dependent endonuclease inhibitor baloxavir marboxil was approved in February 2018 for the treatment of influenza virus infection in Japan. In vitro studies have revealed that an I38T substitution in the polymerase acidic subunit (PA) is associated with reduced susceptibility of influenza viruses to baloxavir.

Objectives

Development of a rapid and simple method for monitoring influenza A(H1N1)pdm09, A(H3N2), and B viruses possessing the I38T substitution in PA.

Methods

Three assays were developed based on RNase H2‐dependent PCR (rhPCR) and named A/H1pdm PA_I38T rhPCR, A/H3 PA_I38T rhPCR, and B PA_I38T rhPCR. The assays were evaluated using cDNAs synthesized from in vitro‐transcribed PA gene RNA controls, RNAs purified from viruses isolated in the 2017/2018 and 2018/2019 influenza seasons, and RNAs purified from clinical specimens collected in the 2018/2019 influenza season.

Results

The assays developed in this study accurately discriminated PA I38 and PA T38 with high sensitivity.

Conclusions

Our assays should be considered a powerful tool for monitoring the emergence of baloxavir‐resistant influenza viruses.

Comparison of the detection performance of two different one-step-combined test strips with fluorescent microspheres or colored microspheres as tracers for influenza A and B viruses

Background

Influenza A and B viruses mainly cause respiratory infectious disease. Till now, few tests are able to simultaneously detect both, especially in primary medical establishments.

Methods

This study was designed to compare the performance of two different one-step-combined test strips for the detection of influenza A and B: one strip with fluorescent microspheres for tracers (FMT); and the other strip with colored microspheres for tracers (CMT). To test the strips, cultures of influenza A, B, and other pathogenic viruses were used, in addition to 1085 clinical specimens from symptomatic patients with respiratory infections. Real-time RT-PCR was also considered as a reference method used to detect the different results of FMT and CTM.

Results

Detection thresholds for influenza A and B cultures using serial dilutions revealed that the sensitivity of FMT was higher than that of CMT (both P < 0.05). With the culture mixtures of Coxsackie virus (A16), enteric cytopathic human orphan virus (ECHO type30), enterovirus (EV71), rotavirus (LLR strain), and enteric adenovirus (AdV 41), specificity assessment demonstrated that there was no cross reaction during the usage of the two test strips as shown by the results which were negative. In the detection of influenza A in 1085 clinical specimens, the total coincidence rate was 96.7%, the positive coincidence rate was 97.1%, and the negative coincidence rate was 96.7%. In the case of influenza B detection, the total coincidence rate was 99.1%, the positive coincidence rate was 92.6%, and the negative coincidence rate was 98.5%. In addition, with influenza A or B real-time RT-PCR detection method, the results showed that, for influenza A, 26 of the 33 specimens that negative with CMT but positive with FMT, showed positive results, and none of the 3 specimens that positive with CMT but negative with FMT showed a positive result; For influenza B, 12 of the 15 specimens that negative with CMT but positive with FMT, showed positive results, and none of the 5 specimens that positive with CMT but negative with FMT showed a positive result.

Conclusions

FMT performed better than CMT in the combined detection of influenza A and B viruses.

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.

Development of real-time fluorescent reverse transcription loop-mediated isothermal amplification assay with quenching primer for influenza virus and respiratory syncytial virus

Influenza virus and respiratory syncytial virus cause acute upper and lower respiratory tract infections, especially in children and the elderly. Early treatment for these infections is thought to be important, so simple and sensitive detection methods are needed for use at clinical sites. Therefore, in this study, real-time reverse transcription loop-mediated isothermal amplification assays with quenching primer for influenza virus and respiratory syncytial virus were developed. Evaluation of a total of 113 clinical specimens compared to real-time RT-PCR assays showed that the novel assays could distinguish between the types and subtypes of influenza virus and respiratory syncytial virus and had 100% diagnostic specificity. The diagnostic sensitivity of each assay exceeded 85.0% and the assays showed sufficient clinical accuracy. Furthermore, positive results could be obtained in around 15 min using the novel assays in cases with high concentrations of virus. The developed assays should be useful for identifying influenza virus and respiratory syncytial virus cases not only in experimental laboratories but also in hospital and quarantine laboratories.

Development and evaluation of a new real-time RT-PCR assay for detecting the latest H9N2 influenza viruses capable of causing human infection

The H9N2 subtype of avian influenza A viruses (AIV) has spread among domestic poultry and wild birds worldwide. H9N2 AIV is sporadically transmitted to humans from avian species. A total of 42 laboratory‐confirmed cases of non‐fatal human infection with the Eurasian Y280 and G1 lineages have been reported in China, Hong Kong, Bangladesh and Egypt since 1997. H9N2 AIV infections in poultry have become endemic in Asia and the Middle East and are a major source of viral internal genes for other AIV subtypes, such that continuous monitoring of H9N2 AIV is recommended. In this study, a new, one‐step, real‐time RT‐PCR assay was developed to detect two major Eurasian H9 lineages of AIV capable of causing human infection. The sensitivity of this assay was determined using in vitro‐transcribed RNA, and the detection limit was approximately 3 copies/reaction. In this assay, no cross‐reactivity was observed against RNA from H1–15 subtypes of influenza A viruses, influenza B viruses and other viral respiratory pathogens. In addition, this assay could detect the H9 hemagglutinin (HA) gene from artificially reconstituted clinical samples spiked with H9N2 virus without any non‐specific reactions. Therefore, this assay is highly sensitive and specific for H9 HA detection. The assay is useful both for diagnostic purposes in cases of suspected human infection with influenza H9N2 viruses and for the surveillance of both avian and human influenza viruses.

Development and Evaluation of New Real-Time RT-PCR Assays for Identifying the Influenza A Virus Cluster IV H3N2 Variant

From 2005 to July 6, 2018, a total of 435 swine-origin influenza A H3N2 variant virus (H3N2v) infections in humans were reported in the USA. The largest H3N2v outbreak in the USA occurred in 2011-2012. This virus obtained the HA gene from the human seasonal H3N2 influenza A viruses (seasonal H3N2) via human-to-swine transmission in the mid-1990s and was classified as Cluster IV H3N2v. For early detection of public health threats associated with Cluster IV H3N2v distinct from seasonal H3N2, we developed highly specific and sensitive one-step real-time RT-PCR assays directly targeting the HA genes of Cluster IV H3N2v and seasonal H3N2. These assays are useful for the systematic surveillance and identification of Cluster IV H3N2v.

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.

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.

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.

Detection of respiratory viruses in gargle specimens of healthy children

•

Gargle samples were collected from children and tested respiratory viruses.

•

In 45(45/200; 22.5%) episodes, some respiratory viruses detected without symptoms.

•

Under asymptomatic conditions, detected viruses were mainly RVs and EV/RV untyped.

•

PIVs, RSV and hCoV OC43 were detected only when clinical symptom was seen.

•

Asymptomatic infections may play an important role in the viral circulation.

Background

Respiratory tract viral infection is one of the most common and important diseases in children. Polymerase chain reaction (PCR) tests are often used to detect viruses in samples, it is difficult to interpret the clinical significance of PCR positivity, which may reflect a past, imminent or active asymptomatic infection due to their high sensitivity. Although single respiratory viruses have been detected in samples from children with symptoms, other respiratory viruses can also be detected simultaneously. However, the clinical importance of these findings for the symptoms is not known.

Objectives

To investigate the prevalence of respiratory viruses among children without any symptoms such as acute respiratory illness and/or fever.

Study design

From week twenty-five 2013 to week twenty-six 2014, gargle samples were collected from children once a week and these samples were subjected to real-time PCR to detect respiratory viruses. On each sampling day, we asked the parents about their children’s health condition.

Results

Among the 286 samples collected, 200 were from asymptomatic children. In the asymptomatic condition, human parechovirus, adenovirus, enterovirus, rhinovirus, coronavirus 229E and HKU1 were observed in 45 episodes. In samples from symptomatic children, parainfluenza viruses, respiratory syncytial virus and coronavirus OC43 were detected in addition to those mentioned above.

Conclusions

Various viruses of different species were detected in the specimens from the children regardless of their health status. It might be speculated that host factors such as the function of the immune system influence the clinical outcome of the infection. However, this needs to be studied further.