Rhinoviruses (RVs)...a primer

Schematic of a human rhinovirus (RV) genome. (+)ssRNA genome.
Based on GenBank accession no. NC_001490 for HRV-C3 (f.QPM).
Use images freely but please cite www.newsmedicalnet.blogspot.com.au 
and Dr. Ian M Mackay as their source.
Click on image to enlarge

More than 100 serologically distinct types (serotypes), and another 50 or more genotypically defined and distinct types (genotypes) of human rhinovirus (RV; Greek rhin = nose) exist within the genus Enterovirus. Along with other members of the family Picornaviridae, the RVs are unenveloped viruses with a positive sense, single-stranded RNA genome that is preceded by a genome-linked protein (5' VPg) and terminated with a poly(A) tract (3').

Other genera within the family include Aphthovirus, Aquamavirus, Avihepatovirus, Cardiovirus, Cosavirus, Dicipivirus, Enterovirus, Erbovirus, Hepatovirus, Kobuvirus, Megrivirus, Parechovirus, Salivirus, Sapelovirus, Senecavirus, Teschovirus and Tremovirus.

HRV discovery...

Click on image to enlarge.

The first rhinovirus to be isolated in cell culture was at the Common Cold Unit (Salisbury, UK).[4] By 1967, 55 serologically distinct (sero)types had been recognized. In 2006 the first report[3] defining a distinct genetic grouping of RV types not previously recognized by Mackay and colleagues contributed to the addition of 50 more distinct types assigned to a new species, RV-C. In 2014, a number of additional RV genomes, as well as known ones, were sequenced and published.[7,8,9]

HRV taxonomy: a tale of types and variants...

Predictive capsid model of a rhinovirus C virion (RV-C3, f.QPM).
3D rendering of predicted RV-C3 capsid providing imagery
similar to that obtained by cryo-electron microscopy
reconstruction at 10 � resolution.
doi:10.1371/journal.pone.0001847.g005 [10]       

RV genotypes and serotypes are most simply referred to as "types". Keep in mind that individual types are still written as �HRV-blahblah� whereas the species shorthand or conversationally written form has dropped the �H� to leave �RV�. The 2 best RV schemes for genetically defining an RV type versus a variant of an RV type (the same RV type, but detected in another patient - very little genetic distance separates one RV variant from another in any region of the genome), have been described by Prof Peter Simmonds and colleagues.[5,6] For the latest naming development check the Picornavirus Study Group�s websites.[1,2]

HRVs and pneumonia...

Pneumonia is a disease that of the young and the elderly in particular. It is responsible for millions of deaths each year and is associated with viral and/or bacterial infections. Pneumonia requires an X-Ray confirmation of inflammatory infiltration of the lung tissue. Community-acquired pneumonia (CAP) in children is frequent in developing countries. CAP can also make existing chronic medical conditions worse and takes advantage of the ageing immune system.

HRVs play some role in the development of bacterial pneumonia, but the extent is likely to be underestimated. Determining the cause of pneumonia is made difficult by the low frequency of sampling the lower respiratory tract, by studies that are  conducted over short periods of time and by the complexity of the viral and bacterial mix involved. Quick and  easy sampling of the upper airways is ideal for routine sampling of patients. This convenience and reduced risk  associated with some sampling methods (needle aspirates for example) sampling of the lower respiratory tract  means that often, detection of putative viral or bacterial pathogens in the upper airways is assumed to be related  to LRT disease, especially in children under the age of 5 years. Studies of pneumonia studies are also  complicated by the infrequent inclusion of a control patient group and by the fact that sputum is not produced  from the healthy lower airway. 

Before PCR methods, respiratory syncytial virus (RSV) and then RVs were described as the major viral  contributors to CAP (between 1 and 2 thirds of cases). In the golden PCR age, RVs are increasingly the major  viral group detected from both upper and lower respiratory tract (sputum) specimens from children with CAP.  These findings are supported even when studies span more than a 12-month period, which should encompass  change in the prevalence of seasonal viruses. 

Viruses, including RVs, are thought to pave the way for bacterial super-infection in some direct or indirect way.  There are data from laboratory research studies which support this as well as clinical data finding a high proportion of  RV and bacterial co-detections. Despite considerable comment in the literature, rhinoviruses are in fact less likely to be co-detected with another virus, than are many other viruses.[11]

Other rhinovirus posts at VDU...

• Happy Birthday rhinoviruses (RVs) - 60 years old today!

References... 

1. Nick Knowles, Chair of the Picornavirus Study Group's excellent Picornaviridae website 
2. The official Picornaviridae Study Group website 
3. KE Arden et al. Frequent detection of human rhinoviruses, paramyxoviruses, coronaviruses, and bocavirus during acute respiratory tract infections. J Med Virol.  2006. 78(9):1232-40 
4. IM Mackay, Human rhinoviruses: The cold wars resume. J Clin Virol. 2008. 42:297-320 
5. P Simmonds and colleagues. Proposals for the classification of human rhinovirus species C into genotypically assigned types. J Gen Virol. 2010. 91(Pt 10):2409- 19. 
6. CL McIntyre and colleagues. Proposals for the classification of human rhinovirus species A, B and C into genotypically assigned types. J Gen Virol. 2013  94(Pt8):1791-806. 
7. Liggett and colleagues. Genome sequences of rhinovirus C isolates from Wisconsin pediatric respiratory studies. Genome Announc. 2014 2(2) e00203-14. 
8. Liggett and colleagues. Genome sequences of rhinovirus B isolates from Wisconsin pediatric respiratory studies. Genome Announc. 2014 2(2) e00202-14. 
9. Liggett and colleagues. Genome sequences of rhinovirus A isolates from Wisconsin pediatric respiratory studies. Genome Announc. 2014 2(2) e00200-14. 
10. McErlean and colleagues. Distinguishing molecular features and clinical characteristics of a putative new rhinovirus species, human rhinovirus C (HRV C). PLoS  One. 2008 3(4):e1847
11. Greer and colleagues. Do rhinoviruses reduce the probability of viral co-detection during acute respiratory tract infections? J Clin Virol. 2009 45(1):10-5

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Respiratory viruses: the viruses we detect in the human respiratory tract

A list of the viruses we can and do detect in the (mostly upper) human respiratory tract.

The standard testing panel/diagnostic menu comprises the influenza A and B viruses, parainfluenza viruses 1-3, respiratory syncytial virus, human metapneumovirus and the adenoviruses.

Some caveats:

• I make no claims to there being a link between cause-and-detect here. Because these viruses are mostly detected using polymerase chain reaction-based methods (PCR, RT-PCR mostly in a real-time format), virus may be detected before, during or after a symptomatic period. Virus may also be found when there are no symptoms at all; an asymptomatic infection. 
• In some instances the virus types included in this list are taken from a larger number of viruses grouped within a genus, for example the genus Enterovirus or the genus Mastadenovirus. My selection is based on our lab's multi-year, PCR-based studies since it can be hard to find decent data for a list like this using the scientific literature. Yes, I should write & publish faster, I know. 227 may well be an underestimate. For example viruses that may cause symptoms of gastroenteritis and central nervous system disease like the Saffold cardioviruses or the parechoviruses (HPeV) may begin their journey towards those diseases as a respiratory infections or involve the respiratory tract in the transmission process in some way.
• Other viruses including the newer polyomaviruses (WUPyV and KIPyV) are also detected in the airways but I have not listed them here.

In short, take this figure as a guide, but a pretty good one, of the approximately 227 viruses that comprise the pool from which we get infected each year. 

Also keep in mind that most if not all viruses seem capable of being associated with a spectrum of clinical disease; from no symptoms at all (yes, even influenza) to mild and short-lived acute respiratory diseases (common colds), severe colds, bronchiolitis, wheeze in the absence of asthma, cough, sore throat, middle ear infection, pneumonia, exacerbating asthma and chronic obstructive pulmonary disease and preceding bacterial secondary infections. These viruses often circulate in seasons some of which overlap and some of which are exclusive. They can also co-occur in the same person at the same time, regardless of season.

We can vaccinate against influenza virus; but it's worth remembering that a vaccine does not stop the virus entering our nose/throat. An effective immunization stops the severe form of the disease which can result from that infection. We may still test positive in a laboratory test after we have been vaccinated, but we are unlikely to be experiencing the full form of the disease (unless the vaccine did not "take" or there was a vaccine mismatch with the intended virus that we got infected by etc). 

Specific antiviral drugs among the respiratory viruses are rare; most infections are self-limiting (you recover from them yourself) and short-lived [1]. Influenza virus is again an exception in that we have useful drugs to apply after we get infected. A specific monoclonal antibody treatment for respiratory syncytial virus (RSV) has also been successfully used for some years [2] and the broader acting ribavirin is licensed for use in humans [3].

One question that is often posed when discussing testing for some/all of the list above is: why bother? If determining the virus won't lead to applying a treatment/cure and is of no use in prevention (if a patient is currently positive for that virus), then why expend time and money to sort it all out? Four very good reasons (from reference  #4) plus some of mine (with some overlap), are listed below. 

We test to...

• Provide information about disease occurrence [4]
• Monitor trends in disease prevalence [4]
• Guide public health efforts to prevent and control diseases [4]
• Allow timely detection of outbreaks to facilitate their management and control [4]
• Inform parents of ill children (clients in some areas of health-speak) who deserve to know what their children are infected with because from that information Doctors can provide a measure of the prognosis (how long they will be like this, how bad it might get etc)
• Inform the drug researchers about the importance of each virus
• Cohort patients with certain viral infections when they are in hospitals, to keep the same viruses together and away from other susceptible but uninfected patients
• Know when one seasonal virus is on the rise (RSV) or decline (rhinoviruses) because that may inform us about when another (influenza virus) is about to take off
• Know which virus is causing disease currently as that may affect hospital resource allocations; being able to identify a bigger influenza season may trigger increased purchasing of antivirals, masks, certain supportive care equipment or consumables or drive the updating of procedures and plans
• Look for sign that an outbreaks has occurred because of a change in the virus or its "behaviour". These changes can also trigger the State to make available new funding for targeted research

These are the viruses that we interact with all the time; some more often than others at certain times of the year. Over a few years, we're likely to have fended them all off, or succumbed to the signs and symptoms of an infection by them, at one time or another. 

Great to have an immune system huh? 

Reference..

1. Antiviral Drugs for Viruses Other Than Human Immunodeficiency Virus
   http://www.ncbi.nlm.nih.gov/pubmed/21964179
2. Monoclonal antibody for reducing the risk of respiratory syncytial virus infection in children.
   http://www.ncbi.nlm.nih.gov/pubmed/23633336
3. Respiratory syncytial virus infection in adult populations.http://www.ncbi.nlm.nih.gov/pubmed/22335500
4. Queensland Government's Queensland Health Notifiable Conditions Page
   http://www.health.qld.gov.au/ph/cdb/sru_data.asp

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Wheezing after respiratory virus infection...

Takeyama and colleagues from Japan delved into the viruses present among young children (= 3-years of age) hospitalized with a clinically defined lower respiratory tract infection.

This exemplifies what many such studies do; sample from the upper respiratory tract to find signs of replicating virus in order to study a disease of the lower respiratory tract. 

It's a stretch but if you go along with it you are implying that an upper respiratory tract infection either triggers the symptoms from afar or that the virus travels into the lower respiratory tract to directly cause inflammation and/or cell destruction.

Viruses were detected by PCR-based methods.

Some key findings...

• Respiratory syncytial virus (RSV) was the virus detected most often (51/102 samples from 153 children) in children who were admitted with wheezing followed by rhinoviruses (RV; 21 or 14%), RSV+RV (12 or 8%) and then parainfluenza virus 3 (PIV3; 8 or 5%), influenza virus (IFV; 5 or 3%) or human metapneumovirus (hMPV; 5 or 3%)
• A similar pattern was observed in 259 children who were admitted without wheezing (RSV-25%; RV 9%; IFV 7%; RSV+RV-4%; PIV3-3%; hMPV-1%)
• 67% of children with wheezing were virus positive (POS)
• Children with an allergic predisposition (IgE antibody levels >30IU/mL at admission and a parental history of asthma) POS for RSV more often had wheezing later
• Children who were wheezing & RV POS when they were admitted were more likely to wheeze again than were those who were RV POS without wheeze at admission.

So [allergic predisposition + RSV] or [wheeze/clinical severity + RV] were 2 factors related to subsequent wheeze.

The authors also raised the spectre of RV positivity occurring in asymptomatic individuals in other studies. However, that can happen to some extent with all respiratory viruses. No other virus has 160 distinct type like the RVs...but that's another story.

Article...

1. http://www.ncbi.nlm.nih.gov/pubmed/24535712

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Little rhino...

To the tune of �I�m a little teapot�

I�m a little rhino,

Strain in doubt

Bind with my canyon

Bind without

When I�ve replicated

Just the right amount

You�ll need to get a tissue to blow me out

[alternate: exacerbate your wheezing and cough me out]

Thanks to Cassandra Faux for putting this one together back in 2007.

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Randall the red-nosed toddler...

To the tune of Rudolph the red-nosed reindeer

Randall the red-nosed toddler
Had a very runny nose 
Asthma exacerbation 
Fever adding to his woes 

All of the other toddlers 
Didn't have immunity 
They all came down with symptoms 
Differing in severity 

Then one group of researchers 
Virus-hunting was their game 
Swabbed, extracted, amplified
A rhino POS of course was spied 

Randall�s rhino was sequenced 
Turned out to be rhino C
Randall the red-nosed toddler
Just a 'common' cold indeed!

Randall the red-nosed toddler

Had a very runny nose 
Asthma exacerbation 
Fever adding to his woes 


Thanks to Katherine Arden and Cassandra Faux for helping me put these together back in 2008.

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A new rhino type is coming to town...[corrected]

To the tune of Santa Claus is coming to town

You better watch out
No need to try
Taking antibiotics
I'm telling you why
New rhino types have come in to town (Don't gather 'round)

It's making a list
Not sickening you twice
Will get to you if you're naughty or nice 
New rhino types have come in to town 


Infects you when you're sleeping
Infects if you're awake
Can make you crook and wheeze a lot
Not so "common" for goodness sake!


O! You better watch out!
No need to try
Taking antibiotics
I'm telling you why
New rhino types have come in to town 

___

This one's a bit old now, but came about during our work in defining the third rhinovirus ("common cold" virus) species, RV-C.

Thanks to Katherine Arden and Cassandra Faux for helping me put these together back in 2008.

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Rhinovirus transmission by aerosol and lower respiratory tract disease after inoculation

In the next instalment to answer the question posed in last week's post, we also find that rhinovirus can a lower respiratory tract infection (LRTI), if it is delivered directly to the site; several issues around this topic are contentious in current age of PCR diagnosis of lower respiratory tract disease using specimens from the upper respiratory tract (URT).

From Thomas R. Cate et al, Am J Epidemiol.

Author: Thomas R Cate et al
Journal:  Am J Epidemiol 81(1):95-105
Year: 1965
RV type used: NIH 1734 (RV-A15¹)
RV receptor type: major group; ICAM-I

This study set out to investigate the impact of RV on the lower respiratory tract.

Key features of the study layout..

• 16 healthy adult male inmate volunteers
• Safety-tested preparation of RV-15
• 6 volunteers given 1ml nasopharyngeal serum-inactivated virus via a hand atomizer (coarse droplets expected to mainly deposit in the upper respiratory tract), and 1ml instilled intransally by pipette with subject lying on back
• 8, RV-15-antibody-free volunteers were exposed to 10l of air (16, 20 or 66 TCID₅₀ RV15), via a mask, containing 15-second-old 0.2-3.0um particles generated from a Collison atomizer (see Figure)
• A number of re-inoculations were also performed on each virus-delivery group
• Aerosols was also sampled using a Shipe impinger (this device contained cell culture medium onto which some aerosol was impacted) for virus isolation, after storage at -70�C. These data determined the dose that had been used
• Prior (2-days) to inoculation, nasal, pharyngeal and anal swab specimens and 10ml of nasopharyngeal wash (NPW) were collected, frozen at -20�C for testing to identify pre-existing viruses or bacteria (all culture based). The same specimen types were collected after inoculation (minus the anal swab). RV culture was conducted on human embryonic fibroblast cultures, with rotation at 33�C)

Key results included...

• Only 1 other virus, apart form RV-15, was found in the subjects. Culture may have missed fastidious or unculturable respiratory viruses (like the RV-Cs) however.
• During the 1st week after inoculation, usually starting from day-2..
• NPWs contained culturable virus in at least 1 specimen from 8/8 subjects
• During the 2nd week after inoculation..
• 7/8 subjects gave virus-positive NPWs
• During the 3rd week after inoculation..
• 5/8 subjects gave intermittent virus-positive NPWs
• Maximal virus titre aligned in time with most severe illness
• Nasal and pharyngeal swabs specimens did not yield virus as often as NPWs
• All subjects had a rise in antibody titre of 4-fold or greater, indicating infection, by 3-weeks with a further bump after 4-5-weeks
• Tracheobronchitis was diagnosed in 6/8 antibody-free aerosol-inoculated volunteers. This is a lower respiratory tract disease.
• Signs and symptoms included cough (sometimes in fits), substernal chest pain,, wheezing, tender trachea.
• 3 had a primary diagnosis of tracheobronchitis , the other 3 also had a prominent coryzal illness (nasal obstruction/discharge, sneezing, sore throat, swollen neck lymph nodes). 
• Fever was determined in 5/8, within the 1st 1-2-days.
• Signs and symptoms lasted for 1-4 days, a little longer for a rhinitis-alone
• No tracheobronchitis developed among 31 antibody-free volunteers inoculated through a course spray/drop method into the nasopharynx
• No infection (no suitable rise in antibody) or illness was detected among 6 volunteers inoculated with a preparation of virus that had first been inactivated by incubation with an antibody-positive serum. This identified that there were no other viruses/bacteria in the preparation that could have caused the disease. This had been, infrequently, found in other preparations by the authors so this step was important part of their comprehensive approach.
• 4-weeks later, 2 volunteers from the aerosol infection group, 2 from the inactivated virus group, and 2 new volunteers, were (re-)inoculated
• No infection, illness or virus shedding resulted in the aerosol pair
• No illness but infection and shedding occurred in the pair previously inoculated with inactivated virus
• Infection, illness and shedding were apparent in the new volunteer pair
• Neutrophil counts were significantly raised in aerosol-inoculated volunteers at illness onset and also, but to a lesser extent, in the 6 volunteers given inactivated virus. This explains to me why in those with a predisposition to severe RV outcomes, including those with asthma, a symptomatic RV infection is not necessary to trigger an attack.

The authors concluded...

• The aerosols generated here, which carried relatively small amounts of virus, would likely travel beyond the nasopharynx and tracheobronchial tree and be carried into the lungs, probably with <50% deposited and the remainder exhaled
• No evidence of pneumonia was found
• If RV is suitably aerosolized in sufficiently small particles, inhalation can result in lower respiratory tract disease while site-specific installation into the upper respiratory tract usually results a typical URTI or "common cold"

How do these findings translate to everyday exposures to RV coughs and sneezes and in children? In the general community we are constantly exposed to virus and have a complex, person-specific panoply of antibodies resulting from different infections beginning in childhood. This is probably why we are incapacitated by bad colds and LRTIs all the time! An addendum in the discussion of Cate's paper highlights how symptoms resulting from RV infection are best considered as part of the entire spectrum of possible outcomes. 

Previous symptomatic infection, as shown above, protects from lower respiratory tract disease hence adults are less likely to have LRTIs than children who see these viruses for the first time. Also, there is literature showing that the antibody to some RVs can protect against, or moderate, disease due to infection by other RVs. If you are antibody-free, then disease can potentially be more severe.

Cate's studies are all conducted without knowledge of the 50+ RV-Cs because they could not be grown (detected) using the cells employed by the culture methods of the day. Why is that relevant? Because some consider RV-Cs to be more asthmagenic/pathogenic and because we don't know the receptor or natural tissue tropism/distribution of the RV-Cs in humans. How the RV-Cs perform in human volunteer infections is unknown.

Certainly room remains for some new research building upon excellent studies like this one by Cate et al and highlighting (a) that RV can infect the lungs and cause disease if an aerosol is encountered and (b), that one outcome from RV infection does not fit all.

Further reading and references...

1. First HRV nomenclature assignment publication
   http://www.nature.com/nature/journal/v213/n5078/pdf/213761a0.pdf

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Rhinovirus (RV) transmission by aerosol: does it happen or is transmission solely by hand-contact and self-inoculation?

I'll be writing a few posts over the coming weeks based in the papers I've found on this topic of RV transmission. How applicable these study results are to transmission of other respiratory viruses is unknown.

The focus will be on answering the question of "Do rhinoviruses transmit by an aerosol route?" The endpoint is usually the development of a clinical upper respiratory tract infection (URTI) or "common cold". 

A lot of volunteer human infection experiments have been conducted using RVs since their identification 60-years ago. This is likely because RVs were seen to cause only mild illness, reducing the health risk for human volunteers. Less common were influenza studies of this sort (correct me if I'm wrong though). It's also worth noting that adults rather than children were included, so the true spectrum of RV disease was not observed. 

From Elliot Dick et al, the Journal of
Infectious Diseases 

Author: Elliot Dick et al
Journal:  J Infect Dis 156(3):442-448
Year: 1987
RV type used: RV-A16
RV receptor type: major group; ICAM-I

This study set out to see whether RV was transmitted by aerosol, indirect contact, or both.

Key features of the study layout..

• 27-34 males >18-years of age were inoculated intranasally with 56-2,500 TCID₅₀ of safety tested¹ RV-A16 on 2 successive days.
• 8-days after inoculation, the 8 cases with the most severe URTIs played cards with 12 RV-B16 neutralizing antibody-free males for ~12-hours in a room containing 4 tables spaced 1.4m apart.
• Each table seated 2 "donors" and 3 "recipients" and the recipients moved locations each hour. Donors were replaced with fresh donors if their URTIs waned
• Coughs, sneezes, nose blows and hand-to-face movements were monitored
• Acquisition of a separate infection during meal times was eliminated by staggering their egress and entry into the card-playing room and by seating recipients 50ft (15m) apart in a well-ventilated room
• 4 experiments, A-D, were performed.
• Experiment A-C tested aerosol transmission.
• 6/12 males used cloth handkerchiefs; the remaining 6 were restrained from any hand-to-head movements
• In experiment A, a 3ft (1m) plastic collar was worn around the neck
• In experiment B and C, arm restraints were used
• Experiment D utilised Experiment C's contaminated furniture and card playing equipment, moving it all into a 2nd card playing room. 
• 12 new recipients were immediately introduced to the room for 12-hours of poker with exaggerated hand-to-face movements
• Card-playing equipment was exchanged between rooms each hour to keep the contaminant levels high
• All meals were eaten in the experiment room to avoid contact with any donors
• After the 12-hour game, recipients returned to the laboratory each day for 2-weeks to provide nasal washings and record symptoms. If they were symptomatic they were taken to a separate laboratory for sampling.
• Exaggerated exposures of "sentinel" recipients consisted of recipients present during the donor's nasal wash collections or undertaking nasal washing alongside symptomatic recipients
• Nasal washing were collected into Hanks balanced sslt solution (HBSS) medium with 0.5% gelatin and inoculated onto WI-38, Hep-2 and primary rhesus monkey kidney cells within 4-hours after collection

Key results included...

• Experiment A: 11/2 recipients were infected, 5 by aerosol alone
• Experiment B: 6/12 infected, 1 by aerosol alone
• Experiment C: 5/12 infected, 4/5 in the restrained recipients
• 12/18 (67%) control recipients (could be infected by any route) were infected versus 10/18 (56%) restrained recipients
• infected recipients were symptomatic and shed virus for =1-day 
• Experiment D: no infections but 5/8 donor hands yielded culturable RV-A16 virus while none of the recipient's hands did
• No sentinel recipients became symptomatic

The authors concluded...

• Aerosol transmission was the most important  mechanism of natural spread of RV in adults in this study
• Aerosol transmission was nearly as efficient as transmission by combined aerosol/direct contact/indirect contact
• RV-A16 load declined rapidly to near zero on the journey between donor and the nose of the recipient.
• Virus shedding in a recipient was usually first detected 3-days after proximity to the donor

The authors raised some interesting points...

• Some previous studies to defining that RV transmission was primarily due to fomite and droplet contact may have failed to detect a small and large aerosol modality because recipient exposure was too short or to too small a viral inoculum
• In a previous study by these authors, the donor had to have a mild to moderate URTI, in which they shed =10³ TCID₅₀/ml, before transmission reached the desired endpoint
• Brief, casual exposures to an infected RV case infrequently results in adequate transmission as measured by occurrence of a symptomatic episode
•  Exposure by direct inoculation with fresh nasal secretions is practically unlikely

Further reading and references...

1. Safety testing of RV preparations.
   D'Alessio et al. J Infect Dis. 1976;133:28-36.

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RSV retreated, flu fading, parainfluenza picking up: Queensland respiratory virus numbers up to Week 45, 2013

If you like to keep track of influenza cases in Queensland, Australia, then the Queensland Government's Queensland Health (QH) influenza data website is for you.

It's a great place to drop by and check out the comings and goings of influenza viruses and many of the other traditional respiratory viruses including adenoviruses (AdVs), parainfluenzaviruses (PIVs) 1, 2 and 3, human metapneumovirus (MPV) and respiratory syncytial virus (RSV) - the "Big8". Testing is not routinely conducted for the rhinoviruses (RVs).

The snippet below is from data that are publicly reported on the QH website. These images cover to the week beginning 3rd of November (up to Sunday, Nov 10th, 2013).

The charts highlight that the 2013 flu season is winding down in Australia, also reflected by the WHO global updates. This year flu followed on from what seemed to have been a large RSV season. Unfortunately I couldn't find data for this same time period last year to compare RSV prevalence.

In the wake of influenzavirus season, the parainfluenzaviruses are now on the rise in the lead up to summer. I expect the RVs (and enteroviruses) are also climbing, but in greater numbers.

Click to enlarge. 
A snippet from the Queensland Health Statewide Weekly Influenza Surveillance Report for 01.01.2013-10.11.2013

My thanks to the team at the Communicable Diseases Unit, Queensland Health.

The source of these data  can be read in full..

• http://www.health.qld.gov.au/ph/cdb/sru_influenza.asp
• WHO global influenza update http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/en/

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Happy Birthday rhinoviruses (RVs) - 60 years old today!

Predicted capsid model of HRV-QPM (Q=Queensland;
PM-initials of the then PhD student who did all the work).
This distinct virus is now known as HRV-C3.
It was the first HRV-C type to be sequenced,
clinically, epidemiologically and virologically
characterised and modelled. It was the third HRV-C
polyprotein sequence to be placed on  GenBank.

On September 12th 1953, the Common Cold Unit (CCU, Salisbury, United Kingdom) reported isolating the agent of the common cold in laboratory cultures. The article was authored by Dr (later Sir)Christopher Andrewes and colleagues in The Lancet.

The isolate, called D.C. after Dr Donna M. Chaproniere's donated cold sample, was only able to be grown while the lung tissue from a particular embryo remained. Once stock was exhausted, the viral culture failed. The D.C. type was not able to be characterized until 1968, by which time another variant of that type had already be given a name; RV-9.

More reliable, repeatable RV culture were achieved in 1956 Price et al (the JH type) and 1957 by Pelon et al (the 2060 type). Back at the CCU, it was found that increasing the acidity, lowering temperatures and rotating the cultures increased the success of virus isolation. The use of increased acidity was discovered by accident when CCU's Dr David Tyrrell had to replace some medium that was killing his cultures. He borrowed (as we do) others' stocks to tide him over. During this process he noted a sign of viral replication  his cultures were being killed  He eventually deduced it was because of the acidity of the new medium compared to his previous work.

 21,915 days later there have been a number of interesting developments to come from the study of RVs:

• A type is the name for a distinct RV; that type found in another patient anywhere around the world is called a variant of the type. Specific criteria now exist to define types and variants, and to identify a new HRV type.
• Recently, HRVs became RVs - the host bit was dropped but their individual names remain "HRV" and they now have the species name included e.g. HRV-A1
• There are >150 distinct RV types
• As many as 70 RV types can circulate at a single site at one study period
• The early RVs were initially classified as echoviruses (ECHO-28; later RV-1) and have also been called ERC viruses, muriviruses, Salisbury strains, coryzaviruses and enterovirus-like viruses
• RV-Cs do not grow using any routinely used cell culture lines, but can be grown in primary tissues and differentiated multilayer cell cultures at the air-liquid interface
• RVs are the most frequent virus to be detected in children and adults with acute upper respiratory tract infections including the "common cold"
• RV infection of adult chronic obstructive pulmonary disease ( COPD) patients may precipate outgrowth of Haemophilus influenzae, not seen among healthy RV infectees
• RVs are also associated with fever and influenza-like illness (ILI), where and they can be near impossible to discriminate from some ILIs without laboratory testing
• RVs are the viruses most frequently detected in wheezing exacerbations ("attacks") in those with asthma where they, more than any other virus, seem to take advantage of antiviral immune deficiencies. While RV-Cs appear to be more exacerbatory, I personally believe this is just an artefact of small, short studies
• RVs are found more often than other viruses in people without overt signs of respiratory disease; but as a proportion of all viruses, RVs are less often found in well people compared to most other respiratory viruses. 
• RVs do not persist (a given RV type is not detected beyond 2-4 weeks) except in those with serious immune deficiency such as those undergoing lung transplant
• There used to be a genus Rhinovirus, but that was abolished and now the three RV species (A, B, C) sit under the genus Enterovirus
• There is no vaccine or broadly available antiviral for HRVs although both are being actively researched now.
• Prior to the use of PCR to detect RVs in 1988/1989, epidemiology studies looking at the impact of a specific respiratory could not account for 50+ HRV-Cs (and perhaps some fastidious HRV-As and Bs)
• RV-Bs are considered "wimps" by those in the know and they are always under-represented when found i.e they appear to circulate in smaller numbers than chance would dictate they should

So, many happy returns little guys. Long may you educate our immune systems with your constant challenges, long may you interfere with the seasons of other viruses and long may you make me write silly titles for reviews when under your mind-altering influence (that's my excuse anyway). 

Much may have been written about other respiratory viruses over the years, but the HRVs are always with us, always challenging us and always causing problems for us. To study RVs is to study all respiratory viruses and diseases of the upper and lower respiratory tract. To exclude them from study or test is to fail to understand these diseases.

Some literature...

1. Hilding,A. The Common Cold. Arch Otolaryngol. Head Neck Surg. 12, 133-150 (1930). 
2. Tyrrell,D.A.J. & Fielder,M. Cold wars: The fight against the common cold (Oxford University Press, New York, 2002).
3. Propagation of common-cold virus in tissue cultures.
4. Outgrowth of the Bacterial Airway Microbiome following Rhinovirus Exacerbation of Chronic Obstructive Pulmonary Disease
5. Newly identified respiratory viruses in children with asthma exacerbation not requiring admission to hospital.
6. Newly identified human rhinoviruses: molecular methods heat up the cold viruses.
7. Human rhinoviruses: coming in from the cold.
8. Do rhinoviruses reduce the probability of viral co-detection during acute respiratory tract infections?
9. Molecular characterization and distinguishing features of a novel human rhinovirus (HRV) C, HRVC-QCE, detected in children with fever, cough and wheeze during 2003.
10. Prior evidence of putative novel rhinovirus species, Australia.
11. Human rhinoviruses: the cold wars resume.
12. Distinguishing molecular features and clinical characteristics of a putative new rhinovirus species, human rhinovirus C (HRV C).
13. Frequent detection of human rhinoviruses, paramyxoviruses, coronaviruses, and bocavirus during acute respiratory tract infections.

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A drug to stop rhinovirus (HRV) infections in patients with chronic obstructive pulmonary disease (COPD)?

For those who don't know, the HRVs are the most frequent infecting agents (that we know of) of the human upper (and perhaps lower but that work is not done) respiratory tract (URT).The first HRV was isolated in 1953 in the UK and the viruses were soon burdened by the label "common cold viruses". This was largely because early studies were conducted in adults who generally have milder outcomes.
There are about 77 genetically distinct HRV-As, 60 HRV-Cs and 30 HRV-Bs - that's nearly 170 distinct viruses (includes serotypes and genotypes)! Imagine 170 distinct coronaviruses.

In the past they were classified by the type of cell they infected/receptor they used into major (most of them used ICAM-I as the receptor) and minor (the rest; use VLDL-R as the receptor) groups. Sequencing is the preferred method to classify them today.

The receptor for the HRV-Cs remains unknown and they do not grow in routine cell lines instead needing more advanced culture methods. Because of this, studies predating 1988 (the first published PCR primers) generally don't account for the HRV-Cs, even though they were there and causing infections.

A.Prof Eva Kathryn Miller and I recently reviewed the HRV-Cs in some detail. Around 70 distinct HRV genotypes can circulate at a single place over a year...depending on the population being studied. I and others have found that to be the case in both the community and in hospital-based populations.

A recent article from Yamaya and colleagues suggests that a mucolytic drug (stimulates surfactant production and release to help the airways clear themselves of gunk) might be of use in treating HRV infections in COPD patients at least.

Exacerbations, which are mostly due to viruses, are the main contributor to disease burden in patients suffering from COPD, as they are in those with asthma.

The drug, ambroxol hydrochloride is already thought to reduce the frequency of URT disease and may reduce ICAM-I expression. The authors tested this using a major group HRV, HRV-B14 and found reduced release of virus, ICAM-I levels and reduced viral RNA levels.

Prophylactic use may inhibit HRV-B14 infection and modulate the inflammatory response to infection. Many of the differences were moderate (mostly arithmetic rather than logarithmic), albeit statistically significant.

It would be interesting to see what effect the drug has on other major group HRVs, minor group HRVs and on the hard to culture HRV-Cs.

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