Rapid antigen detection test for respiratory syncytial virus diagnosis as a diagnostic tool

Generation of nanobodies against the F protein of respiratory syncytial virus and establishment of an indirect immunofluorescence assay

Respiratory syncytial virus (RSV) infection is a leading cause of acute respiratory infections and death in children and older adults. Currently, there is a lack of effective vaccines and antibody treatments on the market, and the clinical manifestations of RSV are indistinguishable from those of acute respiratory infections caused by other etiologies. Therefore, the prevention and treatment of RSV require not only effective vaccines but also simple, fast, cost-effective, and accurate detection and diagnostic methods. Given the small molecular weight, excellent antigen-binding specificity, and affinity of nanobodies, we successfully obtained a panel of nanobodies by expressing the RSV F protein, immunizing camel, and establishing a phage display library. Among them, F-E2 has been shown to bind specifically to the RSV F protein and can be used for Western blot, enzyme-linked immunosorbent assay, flow cytometry, immunohistochemistry, and immunofluorescence assays. Moreover, an RSV immunofluorescence detection method based on F-E2 has been established and proved to be highly specific, sensitive, cost-effective, and fast, with great application potential.

IMPORTANCE

A respiratory syncytial virus (RSV) detection nanobody, F-E2, was successfully screened by constructing a dromedary camel immune library. F-E2 binds to RSV F with ng affinities and can be used for Western blot, enzyme-linked immunosorbent assay, flow cytometry, immunohistochemistry, and immunofluorescence assays. Importantly, a high-throughput RSV immunofluorescence detection method based on F-E2 has been established and proved to be highly specific, sensitive, cost-effective, and fast, with great application potential.

Summarizing Study Characteristics and Diagnostic Performance of Commercially Available Tests for Respiratory Syncytial Virus: A Scoping Literature Review in the COVID-19 Era

BACKGROUND

Nonpharmaceutical interventions to prevent the spread of coronavirus disease 2019 also decreased the spread of respiratory syncytial virus (RSV) and influenza. Viral diagnostic testing in patients with respiratory tract infections (RTI) is a necessary tool for patient management; therefore, sensitive and specific tests are required. This scoping literature review aimed to summarize the study characteristics of commercially available sample-to-answer RSV tests.

CONTENT

PubMed and Embase were queried for studies reporting on the diagnostic performance of tests for RSV in patients with RTI (published January 2005-January 2021). Information on study design, patient and setting characteristics, and published diagnostic performance of RSV tests were extracted from 77 studies that met predefined inclusion criteria. A literature gap was identified for studies of RSV tests conducted in adult-only populations (5.3% of total subrecords) and in outpatient (7.5%) or household (0.8%) settings. Overall, RSV tests with analytical time >30 min had higher published sensitivity (62.5%-100%) vs RSV tests with analytical time ≤30 min (25.7%-100%); this sensitivity range could be partially attributed to the different modalities (antigen vs molecular) used. Molecular-based rapid RSV tests had higher published sensitivity (66.7%-100%) and specificity (94.3%-100%) than antigen-based RSV tests (sensitivity: 25.7%-100%; specificity:80.3%-100%).

SUMMARY

This scoping review reveals a paucity of literature on studies of RSV tests in specific populations and settings, highlighting the need for further assessments. Considering the implications of these results in the current pandemic landscape, the authors preliminarily suggest adopting molecular-based RSV tests for first-line use in these settings.

Epidemiology of Respiratory Syncytial Virus-Associated Acute Lower Respiratory Tract Infection among Hospitalized Under-5s in Northwestern Nigeria

Objective Globally, 33 million cases of respiratory syncytial virus (RSV) infections occur annually among under-fives (5s). Ninety-nine percent of deaths from RSV occur in low- and middle-income countries. Under-five pneumonia mortality in Nigeria was estimated at 140,520 in 2017, but RSV epidemiological data are scant due to poor awareness and limited testing. Vaccines for RSV are currently under development and RSV mortality data from this high mortality, low resource setting are essential to maximizing the potential benefit of vaccination as well as promoting vaccine uptake. This study aimed to describe the epidemiology of RSV-associated acute lower respiratory tract infection (ALRTI) in children younger than 5 years in Zaria, Northwestern Nigeria.

Methods A prospective cohort study was conducted among children aged 1 month to 5 years who were hospitalized with ALRTI in the Emergency Pediatric Unit of a tertiary hospital in Zaria from November 2018 to October 2019. Naso-pharyngeal swabs were obtained for RSV testing using a point-of-care immunoassay technique.

Results Thirty-three percent (35/106) of the children had RSV-related ALRTI. The median age of RSV-positive cases was 8 months (IQR 3–14). Two-thirds of children (68.6%, 24/35) were below 12 months. The RSV mortality rate was 5.7% (2/35). RSV occurred in 10 months of the year with peaks in March and July.

Conclusion A third of admitted children with ALRTI were positive for RSV. Therefore RSV significantly contributes to childhood pneumonia and the dual seasonal peak observed in our study may have implications for vaccine implementation.

Disease Burden Due to Respiratory Syncytial Virus in Indian Pediatric Population: A Literature Review

Respiratory syncytial virus (RSV) is one of the leading causes of lower respiratory tract infections in young children. Globally, there is huge disease burden, high treatment cost, and health impact beyond acute episodes due to RSV which necessitate development and implementation of preventive strategies for the control of RSV infection. The disease burden due to RSV in pediatric population across India is still not clearly understood so this literature review was therefore conducted to gather data on disease burden due to RSV in Indian pediatric population. Systematic literature search was performed using PubMed and Google search with different medical subject headings from 2007 to 2020. Studies performed in Indian pediatric population were selected for review. Literature review revealed that in India, epidemiology of RSV infection is well documented in young children (0-5 years) as compared to children from other age groups. The rates of RSV detection in various studies conducted in younger children (0-5 years) vary from 2.1% to 62.4% in India which is higher as compared to children from other age groups. In India, RSV mainly peaks around rainy to early winter season, that is, during months of June through October while smaller peak was noted during December, January, and February. In 2020, higher RSV-associated disease burden was reported among children (<5 years) in low-income and lower-middle-income countries. Considering significant disease burden due to RSV in young Indian children, availability of RSV vaccine would be crucial to prevent RSV infections in children and its spread in the community.

Utility of RSV rapid diagnostic assays in hospitalized children in Amman, Jordan

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of acute respiratory infections in children worldwide and a frequent cause of hospitalization. Rapid diagnostic assays (RDAs) are available for RSV and they help guide management; however, they are underutilized in developing countries. We compared molecular diagnostics to RSV RDA in hospitalized children in Amman, Jordan.

MATERIALS AND METHODS

Children under 2 years of age, admitted with fever and/or respiratory symptoms were enrolled prospectively from March 2010 to 2012. Demographic and clinical data were collected through parent/guardian interviews and medical chart abstraction. RSV RDAs were performed, and nasal/throat swabs were tested for RSV using quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

RSV RDA and PCR were performed on specimens from 1271 subjects. RSV RDA had a sensitivity of 26% and a specificity of 99%, with positive and negative predictive values of 98.6% and 43%, respectively. RDA-positive patients had fewer days of symptoms at presentation and were more likely to have a history of prematurity, lower birth weight, require supplemental oxygen, and a longer hospitalization as compared with subjects with negative RDA. Multivariate analysis showed only lower birth weight, lack of cyanosis on examination, and lower cycle threshold to be independently associated with positive RDA (p ≤ .001).

CONCLUSION

RSV RDAs had high specificity, but low sensitivity as compared with qRT-PCR. Positive RDA was associated with patients with a more severe disease, as indicated by oxygen use, longer length of stay, and higher viral load. Implementation of RDAs in developing countries could be an inexpensive and expedient method for predicting RSV disease severity and guiding management.

Seasonality of Respiratory Syncytial Virus Hospitalization

Seasonality of respiratory syncytial virus (RSV) infection is an area of limited knowledge. In this study, we set out to get insight into the epidemic characteristics of RSV. We retrospectively evaluated medical files of 512 hospitalizations in children due to RSV infection from January 2010 to July 2017. In this cohort of patients, there were 96.3% of children below 1 year of age; the median age was 2.8 months. The influence of weather condition during the week of hospitalization (WH) and also the preceding week (WP) on the rate of hospitalizations was also assessed. An overview of morbidity data demonstrates that the epidemic RSV season started from Week 50 of a year and lasts until Week 15 of the following year, with a peak between Week 4 and Week 10. The average monthly percentage rate of morbidity per year was as follows: December, 12.3%; January, 24.5%; February, 29%; and March, 21.7%. Hospitalizations were positively associated with the minimum and maximum outside air temperature during the WH (62.5% and 59.7%, respectively) and the WP (64.3% and 63.4%, respectively) and with relative humidity (WH 23% and WP 29.8%). A weak association with the wind speed was also noticed (WH 22% and WP 21%), while there was no influence of the level of atmospheric pressure on RSV morbidity. We conclude that seasonality of RSV is present between December and April each year, and morbidity is mostly influenced by minimum-maximum outside air temperature changes. Further epidemiological exploration is required to get a better knowledge on both active and passive immunization against RSV.

Results from the WHO external quality assessment for the respiratory syncytial virus pilot, 2016-17

Background

External quality assessments (EQAs) for the molecular detection of respiratory syncytial virus (RSV) are necessary to ensure the provision of reliable and accurate results. One of the objectives of the pilot of the World Health Organization (WHO) Global RSV Surveillance, 2016‐2017, was to evaluate and standardize RSV molecular tests used by participating countries. This paper describes the first WHO RSV EQA for the molecular detection of RSV.

Methods

The WHO implemented the pilot of Global RSV Surveillance based on the WHO Global Influenza Surveillance and Response System (GISRS) from 2016 to 2018 in 14 countries. To ensure standardization of tests, 13 participating laboratories were required to complete a 12 panel RSV EQA prepared and distributed by the Centers for Disease Control and Prevention (CDC), USA. The 14th laboratory joined the pilot late and participated in a separate EQA. Laboratories evaluated a RSV rRT‐PCR assay developed by CDC and compared where applicable, other Laboratory Developed Tests (LDTs) or commercial assays already in use at their laboratories.

Results

Laboratories performed well using the CDC RSV rRT‐PCR in comparison with LDTs and commercial assays. Using the CDC assay, 11 of 13 laboratories reported correct results. Two laboratories each reported one false‐positive finding. Of the laboratories using LDTs or commercial assays, results as assessed by Ct values were 100% correct for 1/5 (20%). With corrective actions, all laboratories achieved satisfactory outputs.

Conclusions

These findings indicate that reliable results can be expected from this pilot. Continued participation in EQAs for the molecular detection of RSV is recommended.

Nosocomial Infections in Patients Hospitalized with Respiratory Syncytial Virus: A Practice Review

Viral testing is not always recommended in children with bronchiolitis due to doubts concerning its prognostic use. In this retrospective study, we investigated how the RSV testing would influence the frequency of nosocomial infections (NI). The files of 305 children, hospitalized due to the respiratory syncytial virus (RSV) infection in the period 2010-2014, were reviewed in the study. We found ten cases of NI. The RSV preventive measures did not vary in the consecutive years investigated, but the number of viral tests substantially varied. In 2010, 2012, and 2014, when ca. 2 tests per RSV(+) patient were performed, the risk of NI per patient was 1.3%, while in 2011 and 2013, when the RSV testing was less frequent, the accumulated risk per patient was 5.2%. There was a strong adverse relationship between the number of tests performed and the number of NI (rho = -0.975). The children with NI, when compared to those without NI, required a longer hospital stay, generating higher hospital costs regarding treatment, productivity loss, and indirect costs. The expenditure for RSV testing in the years of a low NI risk was higher than that in the high-risk years. Conversely, the expenditure related to NI management was lower in the years of a low NI risk. Each euro spent on RSV testing saved over 26 € from the NI management expenditure. We conclude that RSV testing is needed in the hospital setting to isolate the infected children and to prevent nosocomial RSV spread. This strategy is health advantageous and requires less resources than NI treatment.

Development of a Rapid Fluorescent Immunochromatographic Test to Detect Respiratory Syncytial Virus

Human respiratory syncytial virus (RSV) is one of the most common viruses infecting the respiratory tracts of infants. The rapid and sensitive detection of RSV is important to minimize the incidence of infection. In this study, novel monoclonal antibodies (mAbs; B11A5 and E8A11) against RSV nucleoprotein (NP) were developed and applied to develop a rapid fluorescent immunochromatographic strip test (FICT), employing europium nanoparticles as the fluorescent material. For the FICT, the limits of detection of the antigen and virus were 1.25 µg/mL and 4.23 × 10⁶ TCID₅₀/mL, respectively, corresponding to 4.75 × 10⁶ ± 5.8 ×10⁵ (mean ± SD) RNA copy numbers per reaction mixture for RSV NP. A clinical study revealed a sensitivity of 90% (18/20) and specificity of 98.18% (108/110) for RSV detection when comparing the performance to that of reverse transcription polymerase chain reaction (RT-PCR), representing a 15% improvement in sensitivity over the SD Bioline rapid kit. This newly developed FICT could be a useful tool for the rapid diagnosis of RSV infection.

Bronchiolitis in children: The Saudi initiative of bronchiolitis diagnosis, management, and prevention (SIBRO)

Bronchiolitis is the leading cause of admissions in children less than two years of age. It has been recognized as highly debated for many decades. Despite the abundance of literature and the well-recognized importance of palivizumab in the high risk groups, and despite the existence of numerous, high-quality, recent guidelines on bronchiolitis, the number of admissions continues to increase. Only supportive therapy and few therapeutic interventions are evidence based and proved to be effective. Since Respiratory Syncytial Virus (RSV) is the major cause of bronchiolitis, we will focus on this virus mostly in high risk groups like the premature babies and children with chronic lung disease and cardiac abnormalities. Further, the prevention of RSV with palivizumab in the high risk groups is effective and well known since 1998; we will discuss the updated criteria for allocating infants to this treatment, as this medication is expensive and should be utilized in the best condition. Usually, diagnosis of bronchiolitis is not challenging, however there has been historically no universally accepted and validated scoring system to assess the severity of the condition. Severe RSV, especially in high risk children, is unique because it can cause serious respiratory sequelae. Currently there is no effective curative treatment for bronchiolitis. The utility of different therapeutic interventions is worth a discussion.