Clinical and molecular features of human rhinovirus C

A newly discovered group of human rhinoviruses (HRVs) has been classified as the HRV-C species based on distinct genomic features. HRV-Cs circulate worldwide, and are important causes of upper and lower respiratory illnesses. Methods to culture and produce these viruses have recently been developed, and should enable identification of unique features of HRV-C replication and biology.

Human rhinovirus C--associated severe pneumonia in a neonate

We present a case of severe pneumonia, associated with a prolonged infection by a species C rhinovirus (HRV) in a 3-week old neonate. HRV RNA was identified in nasal and nasopharyngeal secretions, bronchoalveolar lavage and bronchial specimens, stool and urine, collected from the patient during a one-month period. No other viral or bacterial agents were detected. Sequence analysis of two regions of the viral genome, amplified directly from the clinical specimens revealed a novel HRV-C variant. These observations highlight the occurrence of severe neonatal infections caused by HRVs and the need of rapid viral diagnostics for their detection.

The human rhinovirus: human-pathological impact, mechanisms of antirhinoviral agents, and strategies for their discovery

As the major etiological agent of the common cold, human rhinoviruses (HRV) cause millions of lost working and school days annually. Moreover, clinical studies proved an association between harmless upper respiratory tract infections and more severe diseases e.g. sinusitis, asthma, and chronic obstructive pulmonary disease. Both the medicinal and socio-economic impact of HRV infections and the lack of antiviral drugs substantiate the need for intensive antiviral research. A common structural feature of the approximately 100 HRV serotypes is the icosahedrally shaped capsid formed by 60 identical copies of viral capsid proteins VP1-4. The capsid protects the single-stranded, positive sense RNA genome of about 7,400 bases in length. Both structural as well as nonstructural proteins produced during the viral life cycle have been identified as potential targets for blocking viral replication at the step of attachment, entry, uncoating, RNA and protein synthesis by synthetic or natural compounds. Moreover, interferon and phytoceuticals were shown to protect host cells. Most of the known inhibitors of HRV replication were discovered as a result of empirical or semi-empirical screening in cell culture. Structure-activity relationship studies are used for hit optimization and lead structure discovery. The increasing structural insight and molecular understanding of viral proteins on the one hand and the advent of innovative computer-assisted technologies on the other hand have facilitated a rationalized access for the discovery of small chemical entities with antirhinoviral (anti-HRV) activity. This review will (i) summarize existing structural knowledge about HRV, (ii) focus on mechanisms of anti-HRV agents from synthetic and natural origin, and (iii) demonstrate strategies for efficient lead structure discovery.

Co-ordinated role of TLR3, RIG-I and MDA5 in the innate response to rhinovirus in bronchial epithelium

The relative roles of the endosomal TLR3/7/8 versus the intracellular RNA helicases RIG-I and MDA5 in viral infection is much debated. We investigated the roles of each pattern recognition receptor in rhinovirus infection using primary bronchial epithelial cells. TLR3 was constitutively expressed; however, RIG-I and MDA5 were inducible by 8-12 h following rhinovirus infection. Bronchial epithelial tissue from normal volunteers challenged with rhinovirus in vivo exhibited low levels of RIG-I and MDA5 that were increased at day 4 post infection. Inhibition of TLR3, RIG-I and MDA5 by siRNA reduced innate cytokine mRNA, and increased rhinovirus replication. Inhibition of TLR3 and TRIF using siRNA reduced rhinovirus induced RNA helicases. Furthermore, IFNAR1 deficient mice exhibited RIG-I and MDA5 induction early during RV1B infection in an interferon independent manner. Hence anti-viral defense within bronchial epithelium requires co-ordinated recognition of rhinovirus infection, initially via TLR3/TRIF and later via inducible RNA helicases.

The ABCs of rhinoviruses, wheezing, and asthma

Human rhinoviruses (HRVs) were discovered as common cold pathogens over 50 years ago. Recent advances in molecular viral diagnostics have led to an appreciation of their role in more-significant respiratory illnesses, including bronchiolitis in infancy, childhood pneumonia, and acute exacerbations of chronic respiratory diseases such as asthma, chronic obstructive lung disease, and cystic fibrosis. Until a few years ago, only two groups of HRVs (A and B) had been recognized. However, full and partial sequencing of HRVs led to the discovery of a third species of HRV (HRV-C) that has distinct structural and biologic features. Risk factors and pathogenic mechanisms for more-severe HRV infections are being defined, and yet fundamental questions persist about mechanisms relating this common pathogen to allergic diseases and asthma. The close relationship between HRV infections and asthma suggests that antiviral treatments could have a major impact on the morbidity associated with this chronic respiratory disease.

Common cold decreases lung function in infants with recurrent wheezing

Background

Common acute viral respiratory infections (colds) are the most frequent cause of exacerbations in infants with recurrent wheezing (RW). However, there is no quantitative information about the effect of colds on the lung function of infants with RW. This study was undertaken to determine the effect of common cold on forced expiratory parameters measured from raised lung volume in infants with RW.

Methods

Spirometric lung function (expiratory flows from raised lung volume) was randomly assessed in 28 infants with RW while they had a common cold and when asymptomatic.

Results

It was found that during colds there was a significant decrease in all forced expiratory parameters and this was much more evident for flows (FEF_50%, FEF_75% and FEF_25–75%) which were definitively abnormal (less than −1.65 z-score) in the majority of infants. There was not association between family asthma, tobacco exposure, and other factors, with the extent of lung function decrease during colds. Tobacco during pregnancy but not a history of family asthma was significantly associated to lower expiratory flows; however, the association was significant only when infants were asymptomatic.

Conclusion

This study shows that common colds cause a marked reduction of lung function in infants with RW.

Do early-life viral infections cause asthma?

Epidemiologic associations between viral lower respiratory infections (LRIs) and asthma in later childhood are well known. However, the question of whether such infections cause asthma or unmask asthma in a susceptible host has still not been settled. Most early evidence centered on the role of the respiratory syncytial virus; however, recent studies highlight a potential role for human rhinovirus as a risk factor for asthma. The links between early-life viral LRI and subsequent asthma are generally via wheeze; however, the presence of wheeze does not give any information about why the child is wheezing. Wheeze in early life is, at best, a fuzzy phenotype and not specific for subsequent asthma. The risk of asthma after viral LRI is increased in the presence of allergic sensitization in early life and if the infection is more severe. Atopy-associated mechanisms also appear to be involved in viral-induced acute exacerbations of asthma, especially in prolonging symptomatology after the virus has been cleared from the lungs. Breaking the nexus between viral respiratory infections and asthma may be possible with interventions designed to inhibit atopy-related effectors mechanisms from participating in the host response to respiratory viral infections.

What role for human rhinoviruses in the lower respiratory tract?

Human rhinoviruses (HRV) usually cause upper airway infections. However, viral replication in the tracheobronchial tree has been disclosed, although its clinical role is poorly known. We evaluated the prevalence of HRV in 159 bronchoalveolar lavages from 88 patients and describe a lung transplant recipient with a high HRV load in association with acute rejection. HRV was detected in 22/88 patients (25.0%): 7/18 lung transplant recipients, 11/41 immunocompetent, and 4/29 immunocompromised (p = n.s.). No lung disease was significantly associated with HRV positivity. It should be recommended to include HRV in the virological diagnostic work-up of lower respiratory specimens to elucidate their role.

Cleavage of eukaryotic initiation factor eIF5B by enterovirus 3C proteases

The enteroviruses poliovirus (PV), Coxsackie B virus (CVB) and rhinovirus (HRV) are members of Picornaviridae that inhibit host cell translation early in infection. Enterovirus translation soon predominates in infected cells, but eventually also shuts off. This complex pattern of modulation of translation suggests regulation by a multifactorial mechanism. We report here that eIF5B is proteolytically cleaved during PV and CVB infection of cultured cells, beginning at 3 hours post-infection and increasing thereafter. Recombinant PV, CVB and HRV 3Cpro cleaved purified native rabbit eukaryotic initiation factor (eIF) 5B in vitro at a single site (VVEQG, equivalent to VMEQG479 in human eIF5B) that is consistent with the cleavage specificity of enterovirus 3C proteases. Cleavage separates the N-terminal domain of eIF5B from its essential conserved central GTPase and C-terminal domains. 3Cpro-mediated cleavage of eIF5B may thus play an accessory role in the shutoff of translation that occurs in enterovirus-infected cells.

Human rhinovirus 1B exposure induces phosphatidylinositol 3-kinase-dependent airway inflammation in mice

RATIONALE

Infection with rhinovirus (RV) triggers exacerbations of asthma and chronic obstructive lung disease.

OBJECTIVES

We sought to develop a mouse model of RV employing RV1B, a minor group serotype that binds to the low-density lipoprotein receptor.

METHODS

C57BL/6 mice were inoculated intranasally with RV1B, replication-deficient ultraviolet (UV)-irradiated RV1B, or RV39, a major group virus.

MEASUREMENTS AND MAIN RESULTS

Viral RNA was present in the lungs of RV1B-treated mice, but not in those exposed to UV-irradiated RV1B or RV39. Lung homogenates of RV-treated mice contained infectious RV 4 days after inoculation. RV1B exposure induced neutrophilic and lymphocytic airway inflammation, as well as increased lung expression of KC, macrophage-inflammatory protein-2, and IFN-alpha and IFN-beta. RV1B-exposed mice showed airway hyperresponsiveness 1 and 4 days after inoculation. UV-irradiated RV1B induced modest neutrophilic airway inflammation and hyperresponsiveness 1 day after exposure. Both RV1B and UV-irradiated RV1B, but not RV39, increased lung phosphorylation of Akt. Confocal immunofluorescence showed colocalization of RV1B and phospho-Akt in the airway epithelium. Finally, pretreatment with the phosphatidylinositol 3-kinase inhibitor LY294002 attenuated chemokine production and neutrophil infiltration.

CONCLUSIONS

We conclude that RV1B induces airway inflammation in vivo. Evidence is presented that viral replication occurs in vivo and is required for maximal responses. On the other hand, viral replication was not required for a subset of RV-induced responses, including neutrophilic inflammation, airway hyperresponsiveness, and Akt phosphorylation. Finally, phosphatidylinositol 3-kinase/Akt signaling is required for maximal RV1B-induced airway neutrophilic inflammation, likely via its essential role in virus internalization.

Infections with human rhinovirus induce the formation of distinct functional membrane domains

The plasma membrane contains distinct domains that are characterized by a high concentration of sphingolipids and cholesterol. These membrane microdomains also referred to as rafts, seem to be intimately involved in transmembranous signaling and often initiate interactions of pathogens and the host cell membranes. Here, we investigated the further reorganization of membrane rafts in cultured epithelial cells and ex vivo isolated nasal cells after infection with rhinoviruses. We demonstrate the formation of ceramide-enriched membrane platforms and large glycosphingolipid-enriched membrane domains and the co-localization of fluorochrome-labeled rhinoviruses with these membrane domains during attachment and uptake of human rhinovirus. Destruction of glycosphingolipid-enriched membrane domains blocked infection of human cells with rhinovirus. Furthermore, our studies indicate that the activation of the acid sphingomyelinase (ASM) is intrigued in the formation of ceramide- or GM1- enriched membrane platforms. Inhibition of the ASM reduces the number of ceramide-enriched platforms and glycosphingolipid-enriched membrane domains. These data reveal a critical role of the ASM for the formation of membrane platforms and infection of human cells with rhinoviruses.

[Study on the status of human rhinovirus infections in infants and young children with acute respiratory infections in Beijing, from 2002 to 2006]

OBJECTIVE

To understand the relationship between human rhinovirus (HRV) and acute respiratory infections in infants and young children in Beijing.

METHODS

Throat swab/nasopharyngeal aspirates were collected from 3292 infants and young children with acute respiratory tract infections in Beijing from November 2002 to November 2006. Primers derived from the highly conserved 5'-noncoding region of human rhinovirus were used to detect HRV from clinical specimens by nested RT-PCR for which the sensitivity and specificity had been determined previously.

RESULTS

Out of these 3292 specimens, 507 were (15.4%, 507/3292) HRV positive with RT-PCR method. HRV were detected from 220 out of 1315 outpatients and 287 out of 1977 inpatients with positive rates as 16.7% and 14.5% respectively. HRV was detected from 50.0% (8/16) of the patients with pharyngitis. Among 280 specimens collected from patients with acute bronchitis, 43 (15.4%) were HRV positive, including 14 from 80 patients with wheezy bronchitis (17.5%). High positive rates were also found in specimens from patients with pneumonia (12.6%, 150/1189), bronchiolitis (16.0%, 42/262) and asthma (12.8%, 10/78). In 53 patients with initial diagnosis as hematic disease or other complicate respiratory infections, 14 were HRV (26.4%, 14/53) positive. As for the seasonal distribution, HRV were detected in most of the months during thie period of research. The highest positive rate of HRV in each year fell in September (32.6%), February (24.2%) of 2004, February of 2005 (35.3%) and March (31.3%) from 2003 to 2006, respectively. Among these HRV positive patients, 44.8% were under 1 year of age (227/507), 15.4% (78/507) were 1 to 2 years old and 12.4% (63/507) were 2 to 3 years old.

CONCLUSION

HRV was associated with acute upper respiratory infections and lower respiratory infections including bronchitis, pneumonia and bronchiolitis in pediatric patients. Patients with lower immunity such as those with hematic diseases, were more susceptible to be infected by HRV. HRV could be detected in all age groups in this study, but the positive rates were decreasing with the increase of patients' age. Infants under 1 year of age seemed to be more likely to get HRV infection.

Characterisation of a newly identified human rhinovirus, HRV-QPM, discovered in infants with bronchiolitis

BACKGROUND

Human rhinoviruses (HRVs) are some of the earliest identified and most commonly detected viruses associated with acute respiratory tract infections (ARTIs) and yet the molecular epidemiology and genomic variation of individual serotypes remains undefined.

OBJECTIVES

To molecularly characterise a novel HRV and determine its prevalence and clinical impact on a predominantly paediatric population.

STUDY DESIGN

Nucleotide sequencing was employed to determine the complete HRV-QPM coding sequence. Two novel real-time RT-PCR diagnostic assays were designed and employed to retrospectively screen a well-defined population of 1244 specimen extracts to identify the prevalence of HRV-QPM during 2003.

RESULTS

Phylogenetic studies of complete coding sequences defined HRV-QPM as a novel member the genus Rhinovirus residing within the previously described HRV-A2 sub-lineage. Investigation of the relatively short VP1 sequence suggest that the virus is resistant to Pleconaril, setting it apart from the HRV A species. Sixteen additional HRV-QPM strains were detected (1.4% of specimens) often as the sole micro-organism present among infants with suspected bronchiolitis. HRV-QPM was also detected in Europe during 2006, and a closely related virus circulated in the United States during 2004.

CONCLUSIONS

We present the molecular characterisation and preliminary clinical impact of a newly identified HRV along with sequences representing additional new HRVs.

Attachment of VLDL receptors to an icosahedral virus along the 5-fold symmetry axis: multiple binding modes evidenced by fluorescence correlation spectroscopy

Human rhinoviruses (HRVs) are composed of 60 identical subunits, each comprising one copy of the viral capsid proteins VP1, 2, 3, and 4. Consequently, 60 symmetry-related epitopes are available for binding of antibodies or receptors. The minor receptor group of HRVs uses members of the low-density lipoprotein receptor family for cell entry. The ligand binding domains of these receptors are composed of various numbers of ligand binding repeats, and several of these modules within a single molecule are believed to attach simultaneously to the star-shaped dome at the 5-fold symmetry axis of the virus. Using fluorescence correlation spectroscopy (FCS), we have now determined the equilibrium binding constants and the mode of attachment of recombinant concatemers of ligand binding module 3 of the human very-low-density lipoprotein receptor to HRV2. We demonstrate that the avidity of the interaction drastically increases with the number of concatenated modules. For the trimer, the binding isotherm was biphasic, indicating that attachment of two and of three modules within the same molecule was resolved. The receptor consisting of seven repeats was found to bind most strongly, but a complete binding isotherm could not be established due to cross-linking of virions. The values of the dissociation constants were about 1 order of magnitude higher than those previously determined by using surface plasmon resonance techniques reflecting the different presentation of the binding partners. As compared to the concatemers, the natural receptors are composed of similar but not identical repeats; thus, cooperativity and different specificity of the ligand-binding modules allow for recognition of many ligands and viral serotypes. Due to the low concentrations and amounts of sample required, FCS is ideally suited for the determination of receptor binding parameters of viruses difficult to produce in high quantities and/or concentrations.

Inhibition of rhinovirus replication in vitro and in vivo by acid-buffered saline

Human rhinoviruses (HRVs) are quite sensitive to low pH. To determine whether this characteristic might be a therapeutic target, we evaluated the sensitivity of HRV to low-pH buffers in vitro and in vivo. Our findings confirm that low pH inhibited replication of most HRVs and reduced the replication of influenza virus. Preliminary experiments verified that the surface pH of the human nasopharynx could be transiently lowered to pH ∼4.0 by topical administration of citrate/phosphate (CP) buffers, which was well tolerated. In a pilot experimental colds study, intranasal administration of CP buffer, compared with normal saline, reduced viral shedding by 1 log unit (10³ vs. 10⁴ 50%tissue culture infective dose/mL; P < .01), although respiratory symptoms were not significantly reduced. These findings demonstrate that low-pH buffers have antiviral activity in vivo and suggest that a larger clinical trial is warranted to determine whether this approach could reduce rates of viral transmission.

Modulation of the immune system by human rhinoviruses

Human rhinoviruses (HRV) are the major cause of the common cold, one of the most frequent infectious diseases in humans. Though HRV infections of the upper respiratory tract are usually rather harmless, there is increasing evidence that HRV sets the stage for more dangerous pathogens, elicits asthmatic exacerbations, severe diseases in the lower respiratory tract and even autoimmunity. The pathogenic mechanisms of HRV infections leading to such complications are still poorly understood. It is a common strategy of pathogens to manipulate our immune system in order to evade an efficient immune response. A major characteristic of HRV is a high degree of species specificity. Thus, analyzing the potential immune evasion mechanisms used by HRV will be helpful for a better understanding of the pathogenesis of the common cold and may contribute to a better understanding of the human immune system as well. In this review we want to illuminate what is known about potential immune escape mechanisms used by HRV and discuss how such disturbances might lead to a suppressed and dysregulated immune competence in man.

Wortmannin delays transfer of human rhinovirus serotype 2 to late endocytic compartments

Human rhinovirus 2 (HRV2) is internalized by members of the low-density lipoprotein receptor family into early endosomes (pH 6.2-6.0) where it dissociates from its receptors. After transfer into late endosomes, the virus undergoes a conformational change and RNA uncoating solely induced by pH < 5.6. Finally, virus capsids are degraded in lysosomes. To investigate the role of phosphatidylinositol 3-kinases (PI3K) in the HRV2 entry route, we used the inhibitor wortmannin. Although virus internalization was not altered by wortmannin, virus accumulated in enlarged early endosomes. Furthermore, the drug delayed HRV2 degradation and viral protein synthesis. Consequently, wortmannin-sensitive PI3K are involved in HRV2 transport from early to late compartments. However, wortmannin had no effect on the titer of infectious virus produced. Our data therefore suggest that virus retained in early endosomes for prolonged time periods can undergo the conformational change that otherwise occurs at pH < or = 5.6 in late endosomes.

The double-stranded RNA binding protein 76:NF45 heterodimer inhibits translation initiation at the rhinovirus type 2 internal ribosome entry site

Poliovirus (PV) plus-strand RNA genomes initiate translation in a cap-independent manner via an internal ribosome entry site (IRES) in their 5' untranslated region. Viral translation is codetermined by cellular IRES trans-acting factors, which can influence viral propagation in a cell-type-specific manner. Engineering of a poliovirus recombinant devoid of neuropathogenic properties but highly lytic in malignant glioma cells was accomplished by exchange of the cognate poliovirus IRES with its counterpart from human rhinovirus type 2 (HRV2), generating PV-RIPO. Neuroblast:glioma heterokaryon analyses revealed that loss of neurovirulence is due to trans-dominant repression of PV-RIPO propagation in neuronal cells. The double-stranded RNA binding protein 76 (DRBP76) was previously identified to bind to the HRV2 IRES in neuronal cells and to inhibit PV-RIPO translation and propagation (M. Merrill, E. Dobrikova, and M. Gromeier, J. Virol. 80:3347-3356, 2006). The results of size exclusion chromatography indicate that DRBP76 heterodimerizes with nuclear factor of activated T cells, 45 kDa (NF45), in neuronal but not in glioma cells. The DRBP76:NF45 heterodimer binds to the HRV2 IRES in neuronal but not in glioma cells. Ribosomal profile analyses show that the heterodimer preferentially associates with the translation apparatus in neuronal cells and arrests translation at the HRV2 IRES, preventing PV-RIPO RNA assembly into polysomes. Results of this study suggest that the DRBP76:NF45 heterodimer selectively blocks HRV2 IRES-driven translation initiation in neuron-derived cells.

H. influenzae potentiates airway epithelial cell responses to rhinovirus by increasing ICAM-1 and TLR3 expression

Rhinovirus (RV) is an important trigger of chronic obstructive pulmonary disease (COPD) exacerbations. In addition, respiratory viruses are more likely to be isolated in patients with a history of frequent exacerbations, suggesting that these patients are more susceptible to viral infection. To examine potential mechanisms for cooperative effects between bacterial and viral infection in COPD, we studied the responses of cultured human airway epithelial cells to nontypeable Hemophilus influenzae and RV. In both 16HBE14o- and primary mucociliary-differentiated cells, preincubation with H. influenzae enhanced RV serotype 39-induced protein expression of interleukin (IL)-8, epithelial-derived neutrophil attractant-78, and growth-related oncogene-alpha. H. influenzae infection also increased the binding of RV39 to cultured cells, as well as expression of intercellular adhesion molecule (ICAM)-1 and Toll-like receptor (TLR)-3, receptors for RV and dsRNA, respectively. Neutralizing antibody against tumor necrosis factor-alpha inhibited IL-8 expression induced by H. influenzae and RV39. Finally, siRNA against TLR3 attenuated RV-induced IL-8 expression. We conclude that H. influenzae infection increases airway epithelial cell ICAM-1 and TLR3 expression, leading to enhanced binding of RV and a potentiation of RV-induced chemokine release. These data provide a cellular mechanism by which H. influenzae infection may increase the susceptibility of COPD patients to RV-induced exacerbations.

Human rhinovirus attenuates the type I interferon response by disrupting activation of interferon regulatory factor 3

The type I interferon (IFN) response requires the coordinated activation of the latent transcription factors NF-kappaB, interferon regulatory factor 3 (IRF-3), and ATF-2, which in turn activate transcription from the IFN-beta promoter. Synthesis and subsequent secretion of IFN-beta activate the Jak/STAT signaling pathway, resulting in the transcriptional induction of the full spectrum of antiviral gene products. We utilized high-density microarrays to examine the transcriptional response to rhinovirus type 14 (RV14) infection in HeLa cells, with particular emphasis on the type I interferon response and production of IFN-beta. We found that, although RV14 infection results in altered levels of a wide variety of host mRNAs, induction of IFN-beta mRNA or activation of the Jak/STAT pathway is not seen. Prior work has shown, and our results have confirmed, that NF-kappaB and ATF-2 are activated following infection. Since many viruses are known to target IRF-3 to inhibit the induction of IFN-beta mRNA, we analyzed the status of IRF-3 in infected cells. IRF-3 was translocated to the nucleus and phosphorylated in RV14-infected cells. Despite this apparent activation, very little homodimerization of IRF-3 was evident following infection. Similar results in A549 lung alveolar epithelial cells demonstrated the biological relevance of these findings to RV14 pathogenesis. In addition, prior infection of cells with RV14 prevented the induction of IFN-beta mRNA following treatment with double-stranded RNA, indicating that RV14 encodes an activity that specifically inhibits this innate host defense pathway. Collectively, these results indicate that RV14 infection inhibits the host type I interferon response by interfering with IRF-3 activation.

Increased proinflammatory responses from asthmatic human airway smooth muscle cells in response to rhinovirus infection

Background

Exacerbations of asthma are associated with viral respiratory tract infections, of which rhinoviruses (RV) are the predominant virus type. Airway smooth muscle is important in asthma pathogenesis, however little is known about the potential interaction of RV and human airway smooth muscle cells (HASM). We hypothesised that rhinovirus induction of inflammatory cytokine release from airway smooth muscle is augmented and differentially regulated in asthmatic compared to normal HASM cells.

Methods

HASM cells, isolated from either asthmatic or non-asthmatic subjects, were infected with rhinovirus. Cytokine production was assayed by ELISA, ICAM-1 cell surface expression was assessed by FACS, and the transcription regulation of IL-6 was measured by luciferase activity.

Results

RV-induced IL-6 release was significantly greater in HASM cells derived from asthmatic subjects compared to non-asthmatic subjects. This response was RV specific, as 5% serum- induced IL-6 release was not different in the two cell types. Whilst serum stimulated IL-8 production in cells from both subject groups, RV induced IL-8 production in only asthmatic derived HASM cells. The transcriptional induction of IL-6 was differentially regulated via C/EBP in the asthmatic and NF-κB + AP-1 in the non-asthmatic HASM cells.

Conclusion

This study demonstrates augmentation and differential transcriptional regulation of RV specific innate immune response in HASM cells derived from asthmatic and non-asthmatics, and may give valuable insight into the mechanisms of RV-induced asthma exacerbations.

Vascular endothelial growth factor-mediated induction of angiogenesis by human rhinoviruses

BACKGROUND

Human rhinoviruses, major precipitants of asthma exacerbations, infect the lower airway epithelium inducing inflammation. The possibility that viral infection may mediate angiogenesis, thus contributing to airway remodeling, has not been evaluated.

OBJECTIVE

To investigate whether epithelial infection with rhinovirus mediates angiogenesis in vitro, evaluate possible modulation by an atopic environment, and confirm angiogenic factor induction after in vivo rhinovirus infection.

METHODS

Bronchial epithelial cells were infected with rhinovirus and levels of vascular endothelial growth factor (VEGF), and angiopoietins were measured. The angiogenic effect of epithelial products was assessed in in vitro models of angiogenesis. PBMCs, obtained from patients with atopic asthma and normal controls, were exposed to rhinovirus; the ability of supernatants from these cultures differentially to affect rhinovirus-mediated epithelial VEGF production was evaluated. VEGF levels were measured in respiratory secretions from patients with asthma, before and during rhinovirus-induced exacerbations.

RESULTS

Epithelial infection with rhinovirus specifically stimulated mRNA expression and release of VEGF, but not angiopoietins, in a time-dependent and dose-dependent manner. Supernatants from these cultures were able to induce angiogenesis in vitro, significantly inhibited by a neutralizing anti-VEGF antibody. When bronchial cells were exposed to supernatants of rhinovirus-infected mononuclear cells from normal subjects or atopic patients with asthma, VEGF induction was significantly higher under the influence of the atopic environment. VEGF was elevated during rhinovirus-associated asthma exacerbations.

CONCLUSION

Rhinovirus infection, a frequent event, induces VEGF production in bronchial epithelial cells and human airways, an effect enhanced in an atopic environment. Rhinovirus-associated, VEGF-mediated angiogenesis may contribute to airway remodeling in asthma.

Rhinovirus induces airway epithelial gene expression through double-stranded RNA and IFN-dependent pathways

Rhinovirus (RV) infection is the major cause of common colds and of asthma exacerbations. Because the epithelial cell layer is the primary target of RV infection, we hypothesize that RV-induced airway disease is associated with the perturbation of airway epithelial gene expression. In this study, well differentiated primary human airway epithelial cells were infected with either RV16 (major group) or RV1B (minor group). Transcriptional gene profiles from RV-infected and mock-infected control cells were analyzed by Affymetrix Genechip, and changes of the gene expression were confirmed by real-time RT-PCR analysis. At 24 h after infection, 48 genes induced by both viruses were identified. Most of these genes are related to the IFN pathway, and have been documented to have antiviral functions. Indeed, a significant stimulation of IFN-beta secretion was detected after RV16 infection. Neutralizing antibody specific to IFN-beta and a specific inhibitor of the Janus kinase pathway both significantly blocked the induction of RV-inducible genes. Further studies demonstrated that 2-aminopurine, a specific inhibitor double-stranded RNA-dependent protein kinase, could block both IFN-beta production and RV-induced gene expression. Thus, IFN-beta-dependent pathway is a part of the double-stranded RNA-initiated pathway that is responsible for RV-induced gene expression. Consistent with its indispensable role in the induction of antiviral genes, deactivation of this signaling pathway significantly enhanced viral production. Because increase of viral yield is associated with the severity of RV-induced airway illness, the discovery of an epithelial antiviral signaling pathway in this study will contribute to our understanding of the pathogenesis of RV-induced colds and asthma exacerbations.

The role of rhinovirus in asthma exacerbations

Rhinoviruses are a major cause of asthma exacerbations in children and adults. With the use of sensitive RT-PCR methods, respiratory viruses are found in approximately 80% of wheezing episodes in children and in approximately one half of such episodes in adults. Rhinovirus is a member of the family Picornaviridae, and acute rhinovirus infections occur predominantly in the upper airway. This virus has also been identified in the lower airway, and it might cause acute wheezing through the production of proinflammatory mediators with a resulting neutrophilic inflammatory response. Precisely how this process leads to increases in airway hyperresponsiveness and airway obstruction is not fully established. However, risk factors for wheezing with colds include asthma and atopy, extremes in age, and perhaps having a deficient TH1 response to rhinovirus. With the use of in vitro models and experimental inoculation studies, significant advances have led to a better understanding of the mechanisms by which rhinovirus infections cause asthma exacerbations. Advances in our understanding of this interaction might provide knowledge that could ultimately lead to specific treatment modalities to prevent and/or treat this significant burden of asthma exacerbations.

The minor receptor group of human rhinovirus (HRV) includes HRV23 and HRV25, but the presence of a lysine in the VP1 HI loop is not sufficient for receptor binding

Like all 10 minor receptor group human rhinoviruses (HRVs), HRV23 and HRV25, previously classified as major group viruses, are neutralized by maltose binding protein (MBP)-V33333 (a soluble recombinant concatemer of five copies of repeat 3 of the very-low-density lipoprotein receptor fused to MBP), bind to low-density lipoprotein receptor in virus overlay blots, and replicate in intercellular adhesion molecule 1 (ICAM-1)-negative COS-7 cells. From phylogenetic analysis of capsid protein VP1-coding sequences, they are also known to cluster together with other minor group strains. Therefore, they belong to the minor group; there are now 12 minor group and 87 major group HRV serotypes. Sequence comparison of the VP1 capsid proteins of all HRVs revealed that the lysine in the HI loop, strictly conserved in the 12 minor group HRVs, is also present in 9 major group serotypes that are neutralized by soluble ICAM-1. Despite the presence of this lysine, they are not neutralized by MBP-V33333 and fail to replicate in COS-7 cells and in HeLa cells in the presence of an ICAM-1-blocking antibody. These nine serotypes are therefore "true" major group viruses.

Rhinovirus infects primary human airway fibroblasts and induces a neutrophil chemokine and a permeability factor

The events linking rhinovirus (RV) infection to airway symptoms are poorly understood. The virus initially infects airway epithelium followed by a vigorous inflammatory response that may entail spread of RV from epithelium to other cells in the airway wall. However, RV has fastidious growth characteristics and to date reproductive infection of primary cells other than human airway epithelium has not been confirmed. Airway fibroblasts are adjacent to and in contact with epithelial cells, play a key role in innate immune responses, and may participate in the evolution of inflammation. To investigate fibroblast actions, we first determined whether RV could infect and replicate in primary culture human lung fibroblasts. RV serotype 16 (RV16) was used to infect fibroblasts grown from lung tissue, and virus infection with replication was demonstrated by a combination of techniques. RT-PCR was used to show an increase in RV transcription; confocal microscopy demonstrated colocalization of the replicative form of RV genome (double-stranded RNA) and RV16 proteins; infectious virus was also recovered from the culture supernatant of infected fibroblasts. Functional consequences of RV infection were next examined. RV infection of fibroblasts was followed by an increase in epithelial neutrophil-activating peptide-78 (ENA-78) mRNA and protein. The permeability factor vascular endothelial growth factor (VEGF) was also induced over a similar time course. These data suggest that interactions between RV and human fibroblasts are feasible, may coordinate neutrophil chemoattraction with enhanced vascular permeability and that fibroblasts may contribute to inflammatory responses following RV infections.

Efficacy of zinc against common cold viruses: an overview

Objective

To review the laboratory and clinical evidence of the medicinal value of zinc for the treatment of the common cold.

Data Sources

Published articles identified through Medline (1980–2003) using the search terms zinc, rhinovirus, and other pertinent subject headings. Additional sources were identified from the bibliographies of the retrieved articles.

Study Selection

By the author.

Data Extraction

By the author.

Data Synthesis

Human rhinoviruses, by attaching to the nasal epithelium via the intracellular adhesion molecule-1 (ICAM-1) receptor, cause most colds. Ionic zinc, based on its electrical charge, also has an affinity for ICAM-1 receptor sites and may exert an antiviral effect by attaching to the ICAM-1 receptors in the rhinovirus structure and nasal epithelial cells. Clinical tests of zinc for treatment of common colds have been inconsistent, primarily because of study design, blinding, and lozenge contents. Early formulations of lozenges also were unpalatable. In three trials with similar study designs, methodologies, and efficacy assessments, zinc effectively and significantly shortened the duration of the common cold when it was administered within 24 hours of the onset of symptoms. Recent reports of trials with zinc gluconate administered as a nasal gel have supported these findings; in addition, they have shown that treatment with zinc nasal gel is effective in reducing the duration and severity of common cold symptoms in patients with established illness.

Conclusion

Clinical trial data support the value of zinc in reducing the duration and severity of symptoms of the common cold when administered within 24 hours of the onset of common cold symptoms. Additional clinical and laboratory evaluations are warranted to further define the role of ionic zinc for the prevention and treatment of the common cold and to elucidate the biochemical mechanisms through which zinc exerts its symptom-relieving effects.

Discrimination among rhinovirus serotypes for a variant ICAM-1 receptor molecule

Intercellular adhesion molecule 1 (ICAM-1) is the cellular receptor for the major group of human rhinovirus serotypes, including human rhinovirus 14 (HRV14) and HRV16. A naturally occurring variant of ICAM-1, ICAM-1Kilifi, has altered binding characteristics with respect to different HRV serotypes. HRV14 binds to ICAM-1 only transiently at physiological temperatures but forms a stable complex with ICAM-1Kilifi. Conversely, HRV16 forms a stable complex with ICAM-1 but does not bind to ICAM-1Kilifi. The three-dimensional structures of HRV14 and HRV16, complexed with ICAM-1, and the structure of HRV14, complexed with ICAM-1Kilifi, have been determined by cryoelectron microscopy (cryoEM) image reconstruction to a resolution of approximately 10 angstroms. Structures determined by X-ray crystallography of both viruses and of ICAM-1 were fitted into the cryoEM density maps. The interfaces between the viruses and receptors contain extensive ionic networks. However, the interactions between the viruses and ICAM-1Kilifi contain one less salt bridge than between the viruses and ICAM-1. As HRV16 has fewer overall interactions with ICAM-1 than HRV14, the absence of this charge interaction has a greater impact on the binding of ICAM-1Kilifi to HRV16 than to HRV14.

Mechanisms of rhinovirus-induced asthma

Several epidemiological studies using sensitive detection methodologies have confirmed that the majority of acute asthma exacerbations follow upper respiratory tract infections--common colds. Most of these colds are due to human rhinoviruses (RVs). RVs are able to reach and replicate in epithelial cells of the lower airways and can activate these cells to produce pro-inflammatory mediators. Under some circumstances, RVs can also become cytotoxic to the epithelium. Atopic asthmatic individuals produce less interferon-gamma and more interleukin-10 than normal subjects in response to RV infection. Symptom severity as well as viral shedding after experimental RV infection, is inversely correlated with 'atopic' status, expressed as the interferon-gamma to interleukin-5 ratio. Expression of co-stimulatory molecules on immune cells is also affected in atopic asthmatics, suggesting an aberrant immune response to RV that may lead to suboptimal viral clearance and viral persistence. Some of the above effects can be reversed in vitro by corticosteroids, second-generation antihistamines or anti-oxidants; however, the optimal strategy for treating acute asthma exacerbations requires further research at both mechanistic and clinical levels.

Absence of the Kilifi mutation in the rhinovirus-binding domain of ICAM-1 in a Caucasian population

Human rhinoviruses (HRV), responsible for approximately 60% of the common colds, are divided into two groups, according to their receptor specificity. The major group of HRVs gains access to human cells by binding to the intercellular adhesion molecule-1 (ICAM-1), whereas HRVs of the minor group use members of the low-density lipoprotein receptor (LDLR) family for cell entry. Previous studies confirmed that the HRV-binding region of ICAM-1 is located in the amino-terminal immunoglobulin-like (Ig) domain 1, which is encoded by exon 2 of the ICAM-1 gene. An A --> T transversion in codon 29 of ICAM-1 exon 2 causes a lysine to methionine substitution (K29M), and was found at a high frequency (33.2%) in Kilifi (Kenya), as well as in other African populations. In this study we examined whether polymorphisms in exon 2 of ICAM-1 could be detected in a Caucasian population, assuming that these could be of importance in HRV binding. DNA from 100 healthy, unrelated, Belgian volunteers was obtained through a noninvasive swish-and-spit method. Using a primer set in the adjacent intron sequences, the full-length ICAM-1 exon 2 was amplified by polymerase chain reaction (PCR), followed by direct sequencing of the PCR product. No polymorphisms could be demonstrated in exon 2 of the ICAM-1 gene among all 100 tested individuals. The rhinovirus-binding Ig domain 1 of ICAM-1 seems to be a highly conserved region in the Caucasian population.

Human rhinovirus type 2-antibody complexes enter and infect cells via Fc-gamma receptor IIB1

HeLa cells were stably transfected with a cDNA clone encoding the B1 isoform of the mouse FcgammaRII receptor (hereafter referred to as HeLa-FcRII cells). The receptor was expressed at high level at the plasma membrane in about 90% of the cells. These cells bound and internalized mouse monoclonal virus-neutralizing antibodies 8F5 and 3B10 of the subtype immunoglobulin G2a (IgG2a) and IgG1, respectively. Binding of the minor-group human rhinovirus type 2 (HRV2) to its natural receptors, members of the low-density lipoprotein receptor family, is dependent on the presence of Ca(2+) ions. Thus, chelating Ca(2+) ions with EDTA prevented HRV2 binding, entry, and infection. However, upon complex formation of (35)S-labeled HRV2 with 8F5 or 3B10, virus was bound, internalized, and degraded in HeLa-FcRII cells. Furthermore, challenge of these cells with HRV2-8F5 or HRV2-3B10 complexes resulted in de novo synthesis of viral proteins, as shown by indirect immunofluorescence microscopy. These data demonstrate that minor-group receptors can be replaced by surrogate receptors to mediate HRV2 cell entry, delivery into endosomal compartments, and productive uncoating. Consequently, the conformational change and uncoating of HRV2 appears to be solely triggered by the low-pH (pH </= 5.6) environment in these compartments.

Effects of Rhinovirus Infection on the Adherence ofStreptococcus pneumoniaeto Cultured Human Airway Epithelial Cells

To examine the effects of rhinovirus (RV) infection on the adherence of Streptococcus pneumoniae to human tracheal epithelial cells, cells were infected with RV-14, and S. pneumoniae were added to the culture medium. The number of S. pneumoniae adhering to epithelial cells increased after RV infection. Y-24180, a specific inhibitor of the platelet-activating factor receptor (PAF-R); PAF; and the pyrrolidine derivative of dithiocarbamate, an inhibitor of transcription factor nuclear factor-kappaB (NF-kappaB), decreased the number of S. pneumoniae adhering to cells after RV-14 infection. RV-14 infection increased PAF-R expression and the activation of NF-kappaB and promoter-specific transcription factor 1. These findings suggest that RV-14 infection stimulates S. pneumoniae adhesion to airway epithelial cells via increases in PAF-Rs that are partly mediated through activation of transcription factors. Increased adherence of S. pneumoniae may be one of the reasons that pneumonia develops after RV infection.

Mouse respiratory epithelial cells support efficient replication of human rhinovirus

Human rhinoviruses (HRV) are responsible for the majority of virus infections of the upper respiratory tract. Furthermore, HRV infection is associated with acute exacerbation of asthma and other chronic respiratory diseases of the lower respiratory tract. A small animal model of HRV-induced disease is required for the development of new therapies. However, existing mouse models of HRV infection are difficult to work with and until recently mouse cell lines were thought to be generally non-permissive for HRV replication in vitro. In this report we demonstrate that a virus of the minor receptor group, HRV1B, can infect and replicate in a mouse respiratory epithelial cell line (LA-4) more efficiently than in a mouse fibroblast cell line (L). The major receptor group virus HRV16 requires human intercellular adhesion molecule-1 (ICAM-1) for cell entry and therefore cannot infect LA-4 cells. However, transfection of in vitro-transcribed HRV16 RNA resulted in the replication of viral RNA and production of infectious virus. Expression of a chimeric ICAM-1 molecule, comprising mouse ICAM-1 with extracellular domains 1 and 2 replaced by the equivalent human domains, rendered the otherwise non-permissive mouse respiratory epithelial cell line susceptible to entry and efficient replication of HRV16. These observations suggest that the development of mouse models of respiratory tract infection by major as well as minor group HRV should be pursued.

A disc-based quantitative carrier test method to assess the virucidal activity of chemical germicides

Suspension tests for virucidal activity of chemical germicides are easier to perform, but they normally do not present the test product with a strong enough challenge. In contrast, carrier tests, where the test virus is dried on an animate or inanimate surface, offer the test formulation a higher level of challenge because it first has to penetrate successfully the inoculum to gain access to and inactivate the target organism on the carrier. Since pathogens in nature are normally found adsorbed to surfaces and/or embedded in organic or cellular debris, the results of carrier tests are more relevant to predicting the activity of chemical germicides under field situations. The method described below uses discs (1 cm in diameter) of brushed stainless steel discs as carriers. Ten micro l of the test virus in a soil load is placed on each disc and the inoculum dried under ambient conditions. The dried inoculum is then exposed to 50 micro l of the test formulation or a control solution for a defined contact time at the specified temperature. EBSS (0.95 ml) is added to each carrier holder to dilute/neutralize the germicide, the inoculum eluted and the eluates titrated in cell cultures to determine the degree of loss in virus viability. At least five test and three control carriers are used in each test. Controls are also included to test for toxicity of the test formulation to the host cells and any interference sub-cytotoxic levels of the formulation may have on the ability of the virus to infect the cells. The method has been used with several types of human and animal pathogenic viruses to test the activity of all major classes of chemical germicides against them.

Role of respiratory viruses in children with acute otitis media

OBJECTIVE

The role of viral infection in acute otitis media (AOM) has not been fully elucidated. We determined the presence of various respiratory viruses in middle ear fluid (MEF) specimens from children with AOM in order to determine whether viral infection or combined effects of viral and bacterial infection enhance or prolong the inflammation in the middle ear, thus worsening clinical outcome.

METHODS

Multiplex nested reverse transcription-polymerase chain reactions was carried out to detect influenza A and B viruses, respiratory syncytial virus (RSV) types A and B, parainfluenza virus types 1, 2, and 3; rhinovirus; and adenovirus in 93 MEF specimens from 79 children with AOM. And we examined whether viral infection with or without an identifiable bacterial infection affect clinical outcomes in AOM. We considered persistent MEF (fluid accumulation in the middle ear persisting up to 1 month after treatment), early recurrence of AOM (within 1 month after initial improvement), and recurrent AOM (more than three recurrences during 6 months of follow up) as indicators for evaluating clinical outcomes.

RESULTS

One or more respiratory viruses were detected in 39 specimens (42%); a total of 42 viral infections identified (three specimens were infected by two viruses). Of the 42 infections, RSV type A was detected in 29, adenovirus in eight, rhinovirus in three, and influenza virus in two. RSV accounted for 73% of viral detections. In children younger than 2 years, RSV infection combined with Streptococcus pneumoniae or Hemophilus influenzae infection carried a higher risk for persistent middle ear effusion than infection with RSV infection alone or those bacterial infection alone.

CONCLUSIONS

Accordingly, vaccination of young children against RSV as well as S. pneumoniae and H. influenzae is important in improving the prognosis in AOM.

Emotional style and susceptibility to the common cold

OBJECTIVE

It has been hypothesized that people who typically report experiencing negative emotions are at greater risk for disease and those who typically report positive emotions are at less risk. We tested these hypotheses for host resistance to the common cold.

METHODS

Three hundred thirty-four healthy volunteers aged 18 to 54 years were assessed for their tendency to experience positive emotions such as happy, pleased, and relaxed; and for negative emotions such as anxious, hostile, and depressed. Subsequently, they were given nasal drops containing one of two rhinoviruses and monitored in quarantine for the development of a common cold (illness in the presence of verified infection).

RESULTS

For both viruses, increased positive emotional style (PES) was associated (in a dose-response manner) with lower risk of developing a cold. This relationship was maintained after controlling for prechallenge virus-specific antibody, virus-type, age, sex, education, race, body mass, and season (adjusted relative risk comparing lowest-to-highest tertile = 2.9). Negative emotional style (NES) was not associated with colds and the association of positive style and colds was independent of negative style. Although PES was associated with lower levels of endocrine hormones and better health practices, these differences could not account for different risks for illness. In separate analyses, NES was associated with reporting more unfounded (independent of objective markers of disease) symptoms, and PES with reporting fewer.

CONCLUSIONS

The tendency to experience positive emotions was associated with greater resistance to objectively verifiable colds. PES was also associated with reporting fewer unfounded symptoms and NES with reporting more.

Human rhinovirus type 16: mutant V1210A requires capsid-binding drug for assembly of pentamers to form virions during morphogenesis

Our laboratory has previously reported isolation of human rhinovirus type 16 (HRV16) mutants which depend on WIN 52035 to grow. A rapid rise of progeny virus infectivity occurred when drug was added late in growth cycles, suggesting that the drug-dependence lesion was at the step of virus assembly (W. Wang et al., J. Virol. 72:1210-1218, 1998). Here, we report that capsid subunits, 5S protomers and 14S pentamers, of a drug-dependent mutant were produced normally in the absence of drug, but mutant 80S empty capsids and 150S provirions were not formed, maturation cleavage of provirions (VP0 --> VP2 + VP4) did not occur, and the unassembled mutant capsid subunits were degraded with a half-life of 15 min. Drug was not required by mutant virus for attachment, uncoating, RNA synthesis and protein synthesis, and polyprotein processing except maturation cleavage. The requirement of drug for assembly of mutant pentamers to form provirions and the rapid assembly of preformed subunits (synthesized in the absence of drug) after drug addition suggested that after native pentamers (P5) have been formed they must be converted to an assembly active state (P5(*)), possibly by a conformational change induced by the binding of drug. We propose that pocket factor plays the same role in wild-type virus. In addition, we also report the construction and the properties of a full-length cDNA clone of HRV16, pR16.11, which produces in vitro transcripts with infectivity similar to that of virion RNA. This cDNA clone is available at the American Type Culture Collection.

Human rhinovirus type 2 is internalized by clathrin-mediated endocytosis

Using several approaches, we investigated the importance of clathrin-mediated endocytosis in the uptake of human rhinovirus serotype 2 (HRV2). By means of confocal immunofluorescence microscopy, we show that K(+) depletion strongly reduces HRV2 internalization. Viral uptake was also substantially reduced by extraction of cholesterol from the plasma membrane with methyl-beta-cyclodextrin, which can inhibit clathrin-mediated endocytosis. In accordance with these data, overexpression of dynamin K44A in HeLa cells prevented HRV2 internalization, as judged by confocal immunofluorescence microscopy, and strongly reduced infection. We also demonstrate that HRV2 bound to the surface of HeLa cells is localized in coated pits but not in caveolae. Finally, transient overexpression of the specific dominant-negative inhibitors of clathrin-mediated endocytosis, the SH3 domain of amphiphysin and the C-terminal domain of AP180, potently inhibited internalization of HRV2. Taken together, these results indicate that HRV2 uses clathrin-mediated endocytosis to infect cells.

Conformational changes, plasma membrane penetration, and infection by human rhinovirus type 2: role of receptors and low pH

Human rhinovirus type 2 (HRV2) is internalized by members of the low-density lipoprotein (LDL) receptor (LDLR) family. It then progresses into late endosomes, where it undergoes conversion from D- to C-antigenicity at pH < 5.6. Upon uncoating, the viral RNA is transferred into the cytoplasm across the endsosomal membrane. However, C-antigenic particles fail to attach to LDLR; this raised the question of whether the virus remains attached to the receptors and is carried to late compartments or rather falls off at the higher pH in early endosomes. We therefore determined the pH dependence of virus-receptor dissociation and virus conversion to C-antigen under conditions preventing endocytosis. (35)S-HRV2 was attached to HeLa cells at 4 degrees C and incubated in buffers of pH 7.4 to 5.0; levels of native virus and C-antigenic particles remaining cell associated or having been released into the medium were determined by immunoprecipitation. At pH 6.0, HRV2 was readily released from plasma membrane receptors in its native form, whereas at pH < or = 5.4, it was entirely converted to C-antigen, which, however, only dissociated from the surface upon prolonged incubation. The antigenic conversion occurred at the same pH regardless of whether HRV2 was free in solution or bound to its receptors. These data suggest that, in vivo, the virus is no longer bound to its receptors when the antigenic conversion and uncoating occur in more acidic late endosomes. When virus was bound to HeLa cells at 4 degrees C, converted into C-antigen by exposure to pH 5.3, and subsequently warmed to 34 degrees C in the presence of bafilomycin (to prevent endosomal uncoating), viral de novo synthesis was detected. This study demonstrates for the first time that a nonenveloped virus such as HRV2 can infect from the plasma membrane when artificially exposed to low pH. This implies that the viral RNA can gain access to the cytoplasm from the plasma membrane.

Asthma exacerbations in children associated with rhinovirus but not human metapneumovirus infection

Children with asthma were studied during the Southern hemisphere winter and summer of 2001-2002. Human rhinovirus (hRV) was significantly associated (P=.0001) with asthma exacerbations in winter and spring/summer, but not in intervening asymptomatic periods. Although hRV was also found in children with upper respiratory tract infection (URTI) who underwent sampling at the same time, it was present in significantly higher numbers of children with symptomatic asthma (P<.0001). Human metapneumovirus was also found in small numbers of children with URTI, but significantly less frequently in children with asthma.

Human rhinovirus selectively modulates membranous and soluble forms of its intercellular adhesion molecule-1 (ICAM-1) receptor to promote epithelial cell infectivity

Human rhinoviruses are responsible for many upper respiratory tract infections. 90% of rhinoviruses utilize intercellular adhesion molecule-1 (ICAM-1) as their cellular receptor, which also plays a critical role in recruitment of immune effector cells. Two forms of this receptor exist; membrane-bound (mICAM-1) and soluble ICAM-1 (sICAM-1). The soluble receptor may be produced independently from the membrane-bound form or it may be the product of proteolytic cleavage of mICAM-1. The ratio of airway epithelial cell expression of mICAM-1 to the sICAM-1 form may influence cell infectivity and outcome of rhinovirus infection. We therefore investigated the effect of rhinovirus on expression of both ICAM-1 receptors in normal human bronchial epithelial cells. We observed separate distinct messenger RNA transcripts coding for mICAM-1 and sICAM-1 in these cells, which were modulated by virus. Rhinovirus induced mICAM-1 expression on epithelial cells while simultaneously down-regulating sICAM-1 release, with consequent increase in target cell infectivity. The role of protein tyrosine kinases was investigated as a potential mechanistic pathway. Rhinovirus infection induced rapid phosphorylation of intracellular tyrosine kinase, which may be critical in up-regulation of mICAM-1. Elucidation of the underlying molecular mechanisms involved in differential modulation of both ICAM-1 receptors may lead to novel therapeutic strategies.

The processing of eIF4GI by human rhinovirus type 2 2A(pro): relationship to self-cleavage and role of zinc

The 2A proteinase (2A(pro)) of human rhinoviruses (HRVs) is a cysteine protease containing a structurally important zinc ion. In the viral polyprotein, the enzyme cleaves between the C terminus of VP1 and its own N terminus. 2A(pro) also processes the two isoforms of the cellular protein, eukaryotic initiation factor 4G (eIF4G). We have shown that mature HRV2 2A(pro), when translated in vitro in rabbit reticulocyte lysates, efficiently cleaves eIF4GI, although the enzyme was not immediately active upon synthesis. Here, we examine the relationship between self-processing and eIF4GI cleavage. The onset of both reactions first occurred at least 10 min after initiation of protein synthesis. Furthermore, when self-processing was prevented by a specific mutation between VP1 and 2A(pro), the VP1-2A(pro) precursor was essentially unable to cleave eIF4GI, implying that self-processing is a prerequisite for eIF4GI cleavage. 2A(pro) synthesized in the presence of a potent zinc chelator is inactive; however, upon addition of excess zinc, HRV2 2A(pro) rapidly gained activity. Finally, the presence of the zinc chelator in the culture medium can protect HeLa cells from HRV infection.

Changes in rhinovirus protein 2C allow efficient replication in mouse cells

Rhinovirus type 16 was found to replicate in mouse L cells that express the viral receptor, human intercellular adhesion molecule 1 (ICAM-1). However, infection of these cells at a low multiplicity of infection leads to no discernible cytopathic effect, and low virus titers are produced. A variant virus, 16/L, was isolated after alternate passage of rhinovirus 16 between HeLa and ICAM-1 L cells. Infection of mouse cells with 16/L leads to higher virus titers, increased production of RNA, and total cytopathic effect. Three amino acid changes were identified in the P2 region of virus 16/L, and the adaptation phenotype mapped to two changes in protein 2C. The characterization of a rhinovirus host range mutant will facilitate the investigation of cellular proteins required for efficient viral growth and the development of a murine model for rhinovirus infection.

Detection of rhinovirus and enterovirus in upper respiratory tract samples using a multiplex nested PCR

Human enteroviruses and rhinoviruses are respiratory pathogens whose role in acute respiratory infection is underestimated due to the use of diagnostic procedures with poor sensitivity. To determine the prevalence of these two pathogens in the upper respiratory tract infections, a multiplex procedure was developed that both detect and differentiate rhinoviruses and enteroviruses. This sensitive procedure allowed the detection of both pathogens from archival material (nasal swabs) collected during the previous winters and differentiated rhinoviruses from enteroviruses. This procedure can be used to determine the role of these pathogens in mild or severe upper respiratory tract infections.