Human parainfluenza viruses
Human parainfluenza viruses | |
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nucleocapsid
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Scientific classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Negarnaviricota
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Class: | Monjiviricetes |
Order: | Mononegavirales |
Family: | Paramyxoviridae |
Groups included | |
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Cladistically included but traditionally excluded taxa | |
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Human parainfluenza viruses (HPIVs) are the viruses that cause human parainfluenza. HPIVs are a paraphyletic group of four distinct single-stranded RNA viruses belonging to the Paramyxoviridae family. These viruses are closely associated with both human and veterinary disease.[2] Virions are approximately 150–250 nm in size and contain negative sense RNA with a genome encompassing about 15,000 nucleotides.[3]
The viruses can be detected via
Classification
The first HPIV was discovered in the late 1950s. The taxonomic division is broadly based on
These include:Virus | GenBank acronym | NCBI taxonomy | Notes |
---|---|---|---|
Human parainfluenza virus type 1 | HPIV-1 | 12730 | Most common cause of croup |
Human parainfluenza virus type 2 | HPIV-2 | 11212 | Causes croup and other upper and lower respiratory tract illnesses |
Human parainfluenza virus type 3 | HPIV-3 | 11216 | Associated with bronchiolitis and pneumonia |
Human parainfluenza virus type 4 | HPIV-4 | 11203 | Includes subtypes 4a and 4b |
HPIVs belong to two genera:
Viral structure and organisation
HPIVs are characterised by producing enveloped virions and containing single stranded negative sense
The structural gene sequence of HPIVs is as follows: 3′-NP-P-M-F-HN-L-5′ (the protein prefixes and further details are outlined in the table below).[7]
Structural protein | Location | Function |
---|---|---|
Hemagglutinin-neuraminidase (HN) | Envelope | Attachment and cell entry |
Fusion Protein (F) | Envelope | Fusion and cell entry |
Matrix Protein (M) | Within the envelope | Assembly |
Nucleoprotein (NP) | Nucleocapsid
|
Forms a complex with the RNA genome
|
Phosphoprotein (P) | Nucleocapsid
|
Forms as part of RNA polymerase complex |
Large Protein (L) | Nucleocapsid
|
Forms as part of RNA polymerase complex |
With the advent of reverse genetics, it has been found that the most efficient human parainfluenza viruses (in terms of replication and transcription) have a genome nucleotide total that is divisible by the number 6. This has led to the "rule of six" being coined. Exceptions to the rule have been found, and its exact advantages are not fully understood.[8]
Viral entry and replication
Viral replication is initiated only after successful entry into a cell by attachment and fusion between the virus and the host cell
Initially the F protein is in an inactive form (F0) but can be cleaved by
Towards the end of the process, (after the formation of the viral proteins) the replication of the viral genome occurs. Initially, this occurs with the formation of a
The observable and morphological changes that can be seen in infected cells include the enlargement of the
The
Host range
The main host remains the human. However, infections have been induced in other animals (both under natural and experimental situations), although these were always asymptomatic.[13]
Clinical significance
It is estimated that there are 5 million children with
For infants and young children, it has been estimated that about 25% will develop "clinically significant disease".[17]
Repeated infection throughout the life of the host is not uncommon and symptoms of later breakouts include
HPIV-1 and HPIV-2 have been demonstrated to be the principal causative agent behind
HPIV-3 has been closely associated with bronchiolitis and pneumonia, and principally targets those aged <1 year.[22]
HPIV-4 remains infrequently detected. It is now believed to be more common than previously thought but less likely to cause severe disease. By the age of 10, the majority of children are seropositive for HPIV-4 infection—this may be indicative of a large proportion of asymptomatic or mild infections.[3]
Those with compromised immunity have a higher risk of infection and mortality and may fall ill with more extreme forms of LRI.
HPIVs have also been linked with rare cases of viral meningitis[24] and Guillain–Barré syndrome.[12]
HPIVs are spread from person to person (i.e., horizontal transmission) by contact with infected secretions in respiratory droplets or contaminated surfaces or objects. Infection can occur when infectious material contacts the mucous membranes of the eyes, mouth, or nose, and possibly through the inhalation of droplets generated by a sneeze or cough. HPIVs can remain infectious in airborne droplets for over an hour.[citation needed]
Airway inflammation
The inflammation of the airway is a common attribute of HPIV infection. It is believed to occur due to the large scale upregulation of
Recent evidence suggests that the virus-specific antibody
Immunology
The body's primary defense against HPIV infection is adaptive immunity involving both humoral and cellular immunity. With humoral immunity, antibodies that bind to the surface viral proteins HN and F protect against later infection.[26] Patients with defective cell-mediated immunity also experience more severe infection, suggesting that T cells are important in clearing infection.[12]
Diagnosis
Diagnosis can be made in several ways, encompassing a range of multi-faceted techniques:[4]
- Isolation and detection of the virus in cell culture.
- Detection of viral antigens directly within bodily respiratory tract secretions using immunofluorescence, enzyme immunoassays or fluoroimmunoassays.
- Polymerase chain reaction (PCR).
- Analysis of specific titrefollowing infection (using paired serum specimens).
Because of the similarity in terms of the antigenic profile between the viruses,
Morbidity and mortality
Mortality caused by HPIVs in developed regions of the world remains rare. Where mortality has occurred, it is principally in the three core risk groups (very young, elderly and
In developing regions of the world, preschool children remain the highest mortality risk group. Mortality may be a consequence of primary viral infection or secondary problems, such as bacterial infection. Predispositions, such as malnutrition and other deficiencies, may further elevate the chances of mortality associated with infection.[12]
Overall, LRIs cause approximately 25–30% of total deaths in preschool children in the developing world. HPIVs are believed to be associated with 10% of all LRI cases, thus remaining a significant cause of mortality.[12]
Risk factors
Numerous factors have been suggested and linked to a higher risk of acquiring the infection, inclusive of
Prevention
Despite decades of research, no
Vaccine techniques which have been used against HPIVs are not limited to intranasal forms, but also viruses attenuated by cold passage, host range attenuation, chimeric construct vaccines and also introducing mutations with the help of reverse genetics to achieve attenuation.[31]
Maternal
Medication
Furthermore,
Interactions with the environment
Parainfluenza viruses last only a few hours in the environment and are inactivated by soap and water. Furthermore, the virus can also be easily destroyed using common hygiene techniques and detergents, disinfectants and antiseptics.[4]
Environmental factors which are important for HPIV survival are pH, humidity, temperature and the medium within which the virus is found. The optimal pH is around the physiologic pH values (7.4 to 8.0), whilst at high temperatures (above 37 °C) and low humidity, infectivity reduces.[33]
The majority of transmission has been linked to close contact, especially in
The exact infectious dose remains unknown.[13]
Economic burden
In economically disadvantaged regions of the world, HPIV infection can be measured in terms of mortality. In the developed world where mortality remains rare, the economic costs of the infection can be estimated. Estimates from the US are suggestive of a cost (based on extrapolation) in the region of $200 million per annum.[3]
References
- ^ "Virus Taxonomy: 2018 Release". International Committee on Taxonomy of Viruses (ICTV). October 2018. Retrieved 25 January 2019.
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- ^ PMID 12692097.
- ^ a b c "Human Parainfluenza Viruses". Centers for Disease Control and Prevention (2011). Archived from the original on 20 March 2012. Retrieved 21 March 2012.
- PMID 21859271.
- PMID 21413341. Retrieved 2009-03-15.
- ^ Hunt, Dr. Margaret. "PARAINFLUENZA, RESPIRATORY SYNCYTIAL AND ADENO VIRUSES". Reference.MD. Retrieved 21 March 2012.
- PMID 11312321.
- PMID 12692097.
- ^ PMID 16007245.
- ^ )
- ^ a b c d e f g h i j "Parainfluenza Virus: Epidemiology". eMedicine. Retrieved 21 March 2012.
- ^ a b c d "HUMAN PARAINFLUENZA VIRUS". Public Health Agency of Canada. 2011-04-19. Retrieved 21 March 2012.
- ^ PMID 8075269.
- PMID 3009769.
- ^ "Acute Respiratory Infections". WHO. Archived from the original on March 24, 2006. Retrieved 21 March 2012.
- ^ S2CID 41967381.
- ^ "General information: human parainfluenza viruses". Health Protection Agency. 27 August 2008. Retrieved 21 March 2012.
- PMID 8747776.
- ^ "CDC - Human Parainfluenza Viruses: Common cold and croup". Archived from the original on 2009-03-03. Retrieved 2009-03-15.
- ^ "Croup Background". Medscape Reference. Retrieved 21 March 2012.
- ^ "Parainfluenza Virus Review". Medscape. Retrieved 21 March 2012.
- ^ Stephen B Greenberg; Robert L Atmar. "Parainfluenza Viruses—New Epidemiology and Vaccine Developments". Touch Infectious Disease. Retrieved 21 March 2012.
- S2CID 25043753.
- ^ "Human Parainfluenza Viruses (HPIV) and Other Parainfluenza Viruses: Background, Pathophysiology, Etiology". 17 October 2021. Retrieved 18 March 2023.
- PMID 27486735.
- PMID 21983132.
- PMID 15845430.
- PMID 1862276.
- PMID 18820572.
- ^ "Parainfluenza Viruses". eLS. Retrieved 21 March 2012.
- ^ "Definition of Human parainfluenza virus". MedicineNet. Archived from the original on 5 January 2012. Retrieved 21 March 2012.
- PMID 14245166.
- ^ "Common Cold, Croup and Human Parainfluenza Viruses: Symptoms and Prevention". NewsFlu. Retrieved 21 March 2012.
Further reading
- Henrickson KJ (2003). "Parainfluenza viruses". Clin. Microbiol. Rev. 16 (2): 242–64. PMID 12692097.
- Human Parainfluenza Viruses (HPIVs)
External links
- Human Parainfluenza Viruses – information provided by the CDC