Improved detection of rhinoviruses by nucleic acid sequence-based amplification after nucleotide sequence determination of the 5' noncoding regions of additional rhinovirus strains

Isothermal amplification-based assays for rapid and sensitive detection of severe acute respiratory syndrome coronavirus 2: Opportunities and recent developments

The coronavirus disease 2019 (COVID‐19) is a global pandemic caused by a novel coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). To date, the virus has been detected in 219 countries of the world. Therefore, managing the disease becomes the priority, in which detecting the presence of the virus is a crucial step. Presently, real‐time RT polymerase chain reaction (RT‐qPCR) is considered a gold standard nucleic acid amplification test (NAAT). The test protocol of RT‐qPCR is complicated, places high demands on equipment, testing reagents, research personnel skills and is expensive. Therefore, simpler point‐of‐care (POC) tests are needed to accelerate clinical decision‐making and take some of the workload from centralized test laboratories. Various isothermal amplification‐based assays have been developed for the sensitive detection of different microorganisms, and recently some of them have been applied for detection of SARS‐CoV‐2. These do not require any programable thermocycler, can produce the results in a single temperature, and therefore, are considered simple. Unlike RT‐qPCR, these methods are highly sensitive, specific, less time‐consuming, simple and affordable, and can be used as POC diagnostic kit for COVID‐19. In this review, we have discussed the potential of isothermal amplification‐based assays as an alternative to RT‐qPCR for the detection of SARS‐CoV‐2.

Current and Future Perspectives on Isothermal Nucleic Acid Amplification Technologies for Diagnosing Infections

Nucleic acid amplification technology (NAAT) has assumed a critical position in disease diagnosis in recent times and contributed significantly to healthcare. Application of these methods has resulted in a more sensitive, accurate and rapid diagnosis of infectious diseases than older traditional methods like culture-based identification. NAAT such as the polymerase chain reaction (PCR) is widely applied but seldom available to resource-limited settings. Isothermal amplification (IA) methods provide a rapid, sensitive, specific, simpler and less expensive procedure for detecting nucleic acid from samples. However, not all of these IA techniques find regular applications in infectious diseases diagnosis. Disease diagnosis and treatment could be improved, and the rapidly increasing problem of antimicrobial resistance reduced, with improvement, adaptation, and application of isothermal amplification methods in clinical settings, especially in developing countries. This review centres on some isothermal techniques that have found documented applications in infectious diseases diagnosis, highlighting their principles, development, strengths, setbacks and imminent potentials for use at points of care.

An Intensive, Active Surveillance Reveals Continuous Invasion and High Diversity of Rhinovirus in Households

We report on infection patterns in 5 households (78 participants) delineating the natural history of human rhinovirus (HRV). Nasopharyngeal collections were obtained every 3-4 days irrespective of symptoms, over a 6-month period, with molecular screening for HRV and typing by sequencing VP4/VP2 junction. Overall, 311/3468 (8.9%) collections were HRV positive: 256 were classified into 3 species: 104 (40.6%) HRV-A; 14 (5.5%) HRV-B, and 138 (53.9%) HRV-C. Twenty-six known HRV types (13 HRV-A, 3 HRV-B, and 10 HRV-C) were identified (A75, C1, and C35 being most frequent). We observed continuous invasion and temporal clustering of HRV types in households (range 5-13 over 6 months). Intrahousehold transmission was independent of clinical status but influenced by age. Most (89.0%) of HRV infection episodes were limited to <14 days. Individual repeat infections were frequent (range 1-7 over 6 months), decreasing with age, and almost invariably heterotypic, indicative of lasting type-specific immunity and low cross-type protection.

Development of real-time fluorescent reverse transcription loop-mediated isothermal amplification assays for rhinovirus detection

Human rhinoviruses (RVs) belong to the genus Enterovirus of the family Picornaviridae, and are classified into RV-A, -B, and -C species. Two assays were developed to detect RVs by a real-time fluorescent reverse transcription loop-mediated isothermal amplification method: one was designed based on the 5'-untranslated regions (UTRs) of RV-A and -B, and the other was designed based on the 5'-UTR of RV-C. The competence of both assays for the diagnosis of RV infection was tested using isolated viruses and compared with real-time reverse transcription polymerase chain reaction assays on clinical specimens. Neither assay demonstrated cross-reactivity with other tested enteroviruses, and they detected 19 out of 21 tested RV-As and seven out of eight tested RV-Cs. The specificity of the assays was 100% for the detection of RVs and their sensitivity for RV-A and RV-C was 86.3% and 77.3%, respectively, on clinical specimens by the combined use of both assays. Considering that both developed assays were highly specific and detected the majority of recently circulating RVs, they are helpful for the diagnosis of RV infection. Consequently, the results generated by these assays will enhance the surveillance of respiratory illness and the study of the roles of RVs associated with clinical features and disease severity.

Reverse transcription genome exponential amplification reaction assay for rapid and universal detection of human rhinoviruses

Human rhinoviruses (HRVs) have long been recognized as the cause of more than one-half of acute viral upper respiratory illnesses, and they are associated with more-serious diseases in children, such as asthma, acute otitis media and pneumonia. A rapid and universal test for of HRV infection is in high demand. In this study, a reverse transcription genome exponential amplification reaction (RT-GEAR) assay targeting the HRV 5' untranslated region (UTR) was developed for pan-HRV detection. The reaction was performed in a single tube in one step at 65 °C for 60 min using a real-time fluorometer (Genie(®)II; Optigene). The RT-GEAR assay showed no cross-reactivity with common human enteroviruses, including HEV71, CVA16, CVA6, CVA10, CVA24, CVB5, Echo30, and PV1-3 or with other common respiratory viruses including FluA H3, FluB, PIV1-4, ADV3, RSVA, RSVB and HMPV. With in vitro-transcribed RNA containing the amplified regions of HRV-A60, HRV-B06 and HRV-C07 as templates, the sensitivity of the RT-GEAR assay was 5, 50 and 5 copies/reaction, respectively. Experiments to evaluate the clinical performance of the RT-GEAR assay were also carried out with a panel of 143 previously verified samples, and the results were compared with those obtained using a published semi-nested PCR assay followed by sequencing. The tested panel comprised 91 HRV-negative samples and 52 HRV-positive samples (18 HRV-A-positive samples, 3 HRV-B-positive samples and 31 HRV-C-positive samples). The sensitivity and specificity of the pan-HRVs RT-GEAR assay was 98.08 % and 100 %, respectively. The kappa correlation between the two methods was 0.985. The RT-GEAR assay based on a portable Genie(®)II fluorometer is a sensitive, specific and rapid assay for the universal detection of HRV infection.

George K, Walsh TJ. Human rhinoviruses

Human rhinoviruses (HRVs), first discovered in the 1950s, are responsible for more than one-half of cold-like illnesses and cost billions of dollars annually in medical visits and missed days of work. Advances in molecular methods have enhanced our understanding of the genomic structure of HRV and have led to the characterization of three genetically distinct HRV groups, designated groups A, B, and C, within the genus Enterovirus and the family Picornaviridae. HRVs are traditionally associated with upper respiratory tract infection, otitis media, and sinusitis. In recent years, the increasing implementation of PCR assays for respiratory virus detection in clinical laboratories has facilitated the recognition of HRV as a lower respiratory tract pathogen, particularly in patients with asthma, infants, elderly patients, and immunocompromised hosts. Cultured isolates of HRV remain important for studies of viral characteristics and disease pathogenesis. Indeed, whether the clinical manifestations of HRV are related directly to viral pathogenicity or secondary to the host immune response is the subject of ongoing research. There are currently no approved antiviral therapies for HRVs, and treatment remains primarily supportive. This review provides a comprehensive, up-to-date assessment of the basic virology, pathogenesis, clinical epidemiology, and laboratory features of and treatment and prevention strategies for HRVs.

Nucleic acid-based diagnostics for infectious diseases in public health affairs

Infectious diseases, mostly caused by bacteria and viruses but also a result of fungal and parasitic infection, have been one of the most important public health concerns throughout human history. The first step in combating these pathogens is to get a timely and accurate diagnosis at an affordable cost. Many kinds of diagnostics have been developed, such as pathogen culture, biochemical tests and serological tests, to help detect and fight against the causative agents of diseases. However, these diagnostic tests are generally unsatisfactory because they are not particularly sensitive and specific and are unable to deliver speedy results. Nucleic acid-based diagnostics, detecting pathogens through the identification of their genomic sequences, have shown promise to overcome the above limitations and become more widely adopted in clinical tests. Here we review some of the most popular nucleic acid-based diagnostics and focus on their adaptability and applicability to routine clinical usage. We also compare and contrast the characteristics of different types of nucleic acid-based diagnostics.

Development of a quantitative real-time nucleic acid sequence-based amplification assay with an internal control using molecular beacon probes for selective and sensitive detection of human rhinovirus serotypes

Evidence demonstrating that human rhinovirus (HRV) disease is not exclusively limited to the upper airways and may cause lower respiratory complications, together with the frequency of HRV infections and the increasing number of immunocompromised patients underline the need for rapid and accurate diagnosis of HRV infections. In this study, we developed the first quantitative real-time nucleic acid sequence-based amplification assay with an internal control using molecular beacon probes for selective and sensitive detection of human rhinovirus serotypes. We described a simple method to accurately quantify RNA target by computing the time to positivity (TTP) values for HRV RNA. Quantification capacity was assessed by plotting these TTP values against the starting number of target molecules. By using this simple method, we have significantly increased the diagnostic accuracy, precision, and trueness of real-time NASBA assay. Specificity of the method was verified in both in silico and experimental studies. Moreover, for assessment of clinical reactivity of the assay, NASBA has been validated on bronchoalveolar lavage (BAL) specimens. Our quantitative NASBA assay was found to be very specific, accurate, and precise with high repeatability and reproducibility.

Newly identified human rhinoviruses: molecular methods heat up the cold viruses

Human rhinovirus (HRV) infections cause at least 70% of virus‐related wheezing exacerbations and cold and flu‐like illnesses. They are associated with otitis media, sinusitis and pneumonia. Annually, the economic impact of HRV infections costs billions in healthcare and lost productivity. Since 1987, 100 officially recognised HRV serotypes reside in two genetically distinct species; HRV A and HRV B, within the genus Enterovirus, family Picornaviridae. Sequencing of their ∼7kb genomes was finalised in 2009. Since 1999, many globally circulating, molecularly‐defined ‘strains’, perhaps equivalent to novel serotypes, have been discovered but remain uncharacterised. Many of these currently unculturable strains have been assigned to a proposed new species, HRV C although confusion exists over the membership of the species. There has not been sufficient sampling to ensure the identification of all strains and no consensus criteria exist to define whether clinical HRV detections are best described as a distinct strain or a closely related variant of a previously identified strain (or serotype). We cannot yet robustly identify patterns in the circulation of newly identified HRVs (niHRVs) or the full range of associated illnesses and more data are required. Many questions arise from this new found diversity: what drives the development of so many distinct viruses compared to other species of RNA viruses? What role does recombination play in generating this diversity? Are there species‐ or strain‐specific circulation patterns and clinical outcomes? Are divergent strains sensitive to existing capsid‐binding antivirals? This update reviews the findings that trigger these and other questions arising during the current cycle of intense rhinovirus discovery. Copyright © 2010 John Wiley & Sons, Ltd.

Resequencing microarray probe design for typing genetically diverse viruses: human rhinoviruses and enteroviruses

BACKGROUND

Febrile respiratory illness (FRI) has a high impact on public health and global economics and poses a difficult challenge for differential diagnosis. A particular issue is the detection of genetically diverse pathogens, i.e. human rhinoviruses (HRV) and enteroviruses (HEV) which are frequent causes of FRI. Resequencing Pathogen Microarray technology has demonstrated potential for differential diagnosis of several respiratory pathogens simultaneously, but a high confidence design method to select probes for genetically diverse viruses is lacking.

RESULTS

Using HRV and HEV as test cases, we assess a general design strategy for detecting and serotyping genetically diverse viruses. A minimal number of probe sequences (26 for HRV and 13 for HEV), which were potentially capable of detecting all serotypes of HRV and HEV, were determined and implemented on the Resequencing Pathogen Microarray RPM-Flu v.30/31 (Tessarae RPM-Flu). The specificities of designed probes were validated using 34 HRV and 28 HEV strains. All strains were successfully detected and identified at least to species level. 33 HRV strains and 16 HEV strains could be further differentiated to serotype level.

CONCLUSION

This study provides a fundamental evaluation of simultaneous detection and differential identification of genetically diverse RNA viruses with a minimal number of prototype sequences. The results demonstrated that the newly designed RPM-Flu v.30/31 can provide comprehensive and specific analysis of HRV and HEV samples which implicates that this design strategy will be applicable for other genetically diverse viruses.

Currently used nucleic acid amplification tests for the detection of viruses and atypicals in acute respiratory infections

For the detection of respiratory viruses conventional culture techniques are still considered as the gold standard. However, results are mostly available too late to have an impact on patient management. The latest developments include appropriate DNA- and RNA-based amplification techniques (both NASBA and PCR) for the detection of an extended number of agents responsible for LRTI. Real time amplification, the latest technical progress, produces, within a considerable shorter time, results with a lower risk of false positives. As results can be obtained within the same day, patient management with appropriate therapy or reduction of unnecessary antibiotic therapy in LRTI will be possible. A number of technical aspects of these amplification assays, and their advantages are discussed.

The availability and use of these new diagnostic tools in virology has contributed to a better understanding of the role of respiratory viruses in LRTI. The increasing importance of the viral agents, Mycoplasma pneumoniae and Chlamydophila pneumoniae in ARI is illustrated. A great proportion of ARI are caused by viruses, but their relative importance depends on the spectrum of agents covered by the diagnostic techniques and on the populations studied, the geographical location and the season. The discovery of new viruses is ongoing; examples are the hMPV and the increasing number of coronaviruses. Indications for the use of these rapid techniques in different clinical situations are discussed. Depending on the possibilities, the laboratory could optimize its diagnostic strategy by applying a combination of immunofluorescence for the detection of RSV an IFL, and a combination of real-time amplification tests for other respiratory viruses and the atypical agents. When implementing a strategy, a compromise between sensitivity, clinical utility, turn around time and cost will have to be found.

A diverse group of previously unrecognized human rhinoviruses are common causes of respiratory illnesses in infants

Background

Human rhinoviruses (HRVs) are the most prevalent human pathogens, and consist of 101 serotypes that are classified into groups A and B according to sequence variations. HRV infections cause a wide spectrum of clinical outcomes ranging from asymptomatic infection to severe lower respiratory symptoms. Defining the role of specific strains in various HRV illnesses has been difficult because traditional serology, which requires viral culture and neutralization tests using 101 serotype-specific antisera, is insensitive and laborious.

Methods and Findings

To directly type HRVs in nasal secretions of infants with frequent respiratory illnesses, we developed a sensitive molecular typing assay based on phylogenetic comparisons of a 260-bp variable sequence in the 5' noncoding region with homologous sequences of the 101 known serotypes. Nasal samples from 26 infants were first tested with a multiplex PCR assay for respiratory viruses, and HRV was the most common virus found (108 of 181 samples). Typing was completed for 101 samples and 103 HRVs were identified. Surprisingly, 54 (52.4%) HRVs did not match any of the known serotypes and had 12–35% nucleotide divergence from the nearest reference HRVs. Of these novel viruses, 9 strains (17 HRVs) segregated from HRVA, HRVB and human enterovirus into a distinct genetic group (“C”). None of these new strains could be cultured in traditional cell lines.

Conclusions

By molecular analysis, over 50% of HRV detected in sick infants were previously unrecognized strains, including 9 strains that may represent a new HRV group. These findings indicate that the number of HRV strains is considerably larger than the 101 serotypes identified with traditional diagnostic techniques, and provide evidence of a new HRV group.

Genome-wide diversity and selective pressure in the human rhinovirus

Background

The human rhinoviruses (HRV) are one of the most common and diverse respiratory pathogens of humans. Over 100 distinct HRV serotypes are known, yet only 6 genomes are available. Due to the paucity of HRV genome sequence, little is known about the genetic diversity within HRV or the forces driving this diversity. Previous comparative genome sequence analyses indicate that recombination drives diversification in multiple genera of the picornavirus family, yet it remains unclear if this holds for HRV.

Results

To resolve this and gain insight into the forces driving diversification in HRV, we generated a representative set of 34 fully sequenced HRVs. Analysis of these genomes shows consistent phylogenies across the genome, conserved non-coding elements, and only limited recombination. However, spikes of genetic diversity at both the nucleotide and amino acid level are detectable within every locus of the genome. Despite this, the HRV genome as a whole is under purifying selective pressure, with islands of diversifying pressure in the VP1, VP2, and VP3 structural genes and two non-structural genes, the 3C protease and 3D polymerase. Mapping diversifying residues in these factors onto available 3-dimensional structures revealed the diversifying capsid residues partition to the external surface of the viral particle in statistically significant proximity to antigenic sites. Diversifying pressure in the pleconaril binding site is confined to a single residue known to confer drug resistance (VP1 191). In contrast, diversifying pressure in the non-structural genes is less clear, mapping both nearby and beyond characterized functional domains of these factors.

Conclusion

This work provides a foundation for understanding HRV genetic diversity and insight into the underlying biology driving evolution in HRV. It expands our knowledge of the genome sequence space that HRV reference serotypes occupy and how the pattern of genetic diversity across HRV genomes differs from other picornaviruses. It also reveals evidence of diversifying selective pressure in both structural genes known to interact with the host immune system and in domains of unassigned function in the non-structural 3C and 3D genes, raising the possibility that diversification of undiscovered functions in these essential factors may influence HRV fitness and evolution.

Sensitivity of detection of rhinoviruses in spiked clinical samples by nucleic acid sequence-based amplification in the presence of an internal control

The objectives of the study were to determine the sensitivity of Nucleic Acid Sequence-Based Amplification (NASBA) for the detection of rhinovirus (RV) serotype 15 in water and in spiked respiratory specimens in the presence of a newly developed internal control (IC). The sensitivity of NASBA on RNA was 10 molecules per reaction. The sensitivity of RV NASBA on RV-15 in water and in respiratory specimens was equal to that in tissue culture. Addition of 10(4) molecules of rhinovirus internal control (RV IC) did not affect the sensitivity. Viral RNA should be extracted from clinical specimens as rapidly as possible after collection, since loss of detectable RNA occurs after 2 h. NASBA allows a sensitive detection of RV RNA in spiked respiratory specimens in the presence of an internal control.

Detection of rhinoviruses by tissue culture and two independent amplification techniques, nucleic acid sequence-based amplification and reverse transcription-PCR, in children with acute respiratory infections during a winter season

Five hundred seventeen consecutive nasopharyngeal aspirates were collected between October 1998 and May 1999 for episodes of acute respiratory tract infections in children presenting at the University Hospital of Antwerp. Culture and nucleic acid amplification techniques--nucleic acid sequence-based amplification (NASBA) and reverse transcription-PCR (RT-PCR)--were applied to detect rhinoviruses (RVs). Other respiratory viruses were detected by immunofluorescence (IF) analysis of the specimens and IF analysis of shell vial cultures. Among the 517 specimens, 219 viral agents were identified. They were, in decreasing order, rhinoviruses (93 [18.0%]), respiratory syncytial virus (76 [14.7%]), adenoviruses (16 [3.1%]), influenza viruses (15 [2.9%]), enteroviruses (15 [2.9%]), and herpes simplex virus (4 [0.8%]). For the evaluation of rhinovirus detection, culture positivity and/or a positive reaction in the two independent amplification methods was used as an expanded "gold standard." Based on this standard, the sensitivity, specificity, positive predictive value, and negative predictive value of culture were 44.7, 100, 100, and 99.8%, and those of NASBA and RT-PCR were 85.1, 98.3, 83.3, and 98.5% and 82.9, 93.4, 55.7, and 98.2%, respectively. NASBA and RT-PCR produced comparable results and were significantly more sensitive than virus culture. RVs showed the highest incidence in acute respiratory tract infections in children.

Amplicon sequencing and improved detection of human rhinovirus in respiratory samples

Improved knowledge of the genotypic characteristics of human rhinovirus (HRV) is required, as are nucleic detection assays with the capacity to overcome both the similarities between members of the family Picornaviridae and the wide diversity of different HRV serotypes. The goal of the present study was to investigate the variability and the genotypic diversity of clinical strains circulating in the community. Since most reverse transcription (RT)-PCR assays available cannot differentiate HRV from other members of the family Picornaviridae, we also validated an assay specific for HRV detection. The 5' noncoding regions of 87 different HRV serotypes and clinical isolates were sequenced. On the basis of sequence analysis and phylogenetic determination, we first confirmed that all clinical isolates were HRV. We then validated a real-time RT-PCR assay that was able not only to detect all HRV serotypes and all clinical isolates tested but also to accurately discriminate between rhinovirus and other viruses from the family Picornaviridae. This assay was negative with isolates of coxsackievirus (types A and B), echovirus, enterovirus, parechovirus, and poliovirus, as well as nonpicornaviruses. Among a series of bronchoalveolar lavage specimens, 4% (7 of 161) were positive by culture, whereas 13% (21 of 161) were positive by RT-PCR. In the present study we showed that to specifically identify HRV in clinical specimens, diagnostic assays need to overcome both the diversities and the similarities of picornaviruses. By sequencing the 5' noncoding regions of rhinoviruses recovered from clinical specimens, we designed probes that could specifically detect rhinovirus.