Analysis of the genomic sequence of a human metapneumovirus

[Acute respiratory tract infections due to a human metapneumovirus in children: descriptive study and comparison with respiratory syncytial virus infections]

BACKGROUND

A new paramyxovirus, the human metapneumovirus was recently isolated. We report the first French cases collected between 2000 and 2002.

MATERIAL AND METHODS

Samples were obtained from nasopharyngeal aspirates from children hospitalised for acute respiratory tract infection in hospitals of Caen and Flers in Basse-Normandie. Human metapneumovirus was studied by polymerase chain reaction on negative samples for respiratory syncytial virus, influenza A and B virus, parainfluenza (1, 2 and 3) virus, adenovirus, coronavirus and rhinovirus. Comparison between metapneumovirus virus and respiratory syncytial virus infections was done after matching sex, age and infection month.

RESULTS

Twenty-six human metapneumovirus infections were identified. A comparative study of a matched group of children infected by respiratory syncytial virus found no significative difference for hospitalisation motive, clinical criteria and treatment.

CONCLUSION

The human metapneumovirus is responsible for typical acute bronchiolitis in children.

Human metapneumovirus infection in Thai children

Human metapneumovirus (hMPV) associated with clinical respiratory tract infection (RTI) in children was first isolated in The Netherlands. Of 120 Thai paediatric patients with RTI examined, 5 cases (4.2%) showed detectable hMPV based on N-gene-specific RT-PCR. All of them were negative for hRSV infection. Aligning the sequences with a reference strain revealed some nucleotide differences, which necessitates future investigation to evaluate clinical significance and genotype variation.

Clinical impact and diagnosis of human metapneumovirus infection

BACKGROUND

Acute respiratory infections are the most common illnesses experienced by people of all ages worldwide. A portion of hitherto unexplained viral respiratory tract illnesses (RTIs) can now be attributed to the human metapneumovirus (hMPV), which was discovered in 2001. Several surveys on the burden of disease of hMPV infection have been conducted in various study groups and with different diagnostic assays. To estimate the impact of hMPV infection in a hospital setting and in the community at large, we reviewed these surveys to establish the burden of disease of hMPV infection.

METHODS

Published data and our own additional unpublished data on the clinical impact of hMPV infection were reviewed.

RESULTS AND CONCLUSION

Worldwide, hMPV infections account for at least 5 to 7% of the RTI in hospitalized children, but immunocompromised and elderly individuals are also at risk. In the general community hMPV infections account for at least 3% of patients who visit a general practitioner for RTI. The seasonality of hMPV infections resembles that for respiratory syncytial virus and influenza virus infections, with recurrent epidemics during the winter months. Clinical symptoms and laboratory findings associated with hMPV infection exhibit a spectrum virtually indistinguishable from those associated with respiratory syncytial virus disease. The development of diagnostic assays must take into account the existence of two hMPV serotypes.

Human metapneumovirus infection in hospital referred South African children

Human metapneumovirus (hMPV) was first described in Dutch children with acute respiratory symptoms. A prospective analysis of the epidemiology, clinical manifestation, and seroprevalence of hMPV and other respiratory viruses in South African children referred to hospital for upper or lower respiratory tract infection were carried out during a single winter season, by using RT-PCR, viral culture, and enzyme-linked immunosorbent assays. In nasopharyngeal aspirates from 137 children, hMPV was detected by RT-PCR in 8 (5.8%) children (2-43 months of age) as a sole viral pathogen, respiratory syncytial virus (RSV) in 21 (15%), influenza A virus in 18 (13%) and influenza B virus in 20 (15%). Pneumonia was diagnosed in seven children and upper respiratory tract infection in one of the hMPV-infected children. One hMPV-infected child was admitted to the intensive care unit in need of mechanical ventilation and one child was infected with human immunodeficiency virus (HIV). No statistically significant differences were found between hMPV, RSV, and influenza virus infected groups with regard to clinical signs and symptoms and chest radiograph findings. The seropositive rate of hMPV specific IgG antibodies was 92% in children aged 24-36 months, the oldest seronegative child in our study was 7 years and 6 months of age. In conclusion, hMPV contributes to upper and lower respiratory tract morbidity in South African children.

Human metapneumovirus-associated lower respiratory tract infections among hospitalized human immunodeficiency virus type 1 (HIV-1)-infected and HIV-1-uninfected African infants

Respiratory tract infections due to human metapneumovirus (hMPV) have been reported worldwide, with the exception of Africa. The prevalence of hMPV infection was studied among human immunodeficiency virus type 1 (HIV-1)-infected and HIV-1-uninfected African infants who were hospitalized for lower respiratory tract infections (LRTIs). Nasopharyngeal aspirate samples obtained from 81 HIV-1-infected and 110 HIV-1-uninfected infants who had tested negative for other respiratory viruses were selected for investigation. hMPV was detected in 10 HIV-1-uninfected infants (9.1%) and 3 HIV-1-infected infants (3.7%). Compared with the entire cohort of HIV-1-uninfected infants, hMPV was 4.6-fold less common than respiratory syncytial virus, but it was 3.2-fold more common than influenza virus and 2.1-fold more common than parainfluenza virus types 1-3. Genotyping of 7 of 14 isolates revealed the circulation of 2 major phylogenetic groups of the virus, which were similar to those described in North America and Europe.

Comparison of the inhibition of human metapneumovirus and respiratory syncytial virus by ribavirin and immune serum globulin in vitro

Human metapneumovirus (hMPV) is a newly recognized pathogen that like its better-known relative, human respiratory syncytial virus (hRSV), appears to be ubiquitous and an important cause of respiratory disease in diverse subpopulations. No antivirals or vaccines are currently approved for the treatment or prevention of hMPV infections. However, ribavirin is licensed to treat serious hRSV-induced infections in children and immune globulin designed for intravenous administration (i.v.IG) and palivizumab (Synagis), a humanized monoclonal antibody preparation, have been utilized as alternatives to vaccines for preventing or reducing the severity of infections caused by this virus. Because both ribavirin and i.v.IG have broad viral specificities, studies were performed to compare the ability of these two agents to inhibit the replication of hRSV and hMPV in tissue culture-based assays. Two experimental chemotherapeutic agents (i.e. VP14637 and JNJ2408068) and different antibody preparations were included in this testing for comparison. Ribavirin and the i.v.IG utilized were found to have equivalent antiviral activity against hMPV and hRSV. In contrast, except for antisera specifically raised against hMPV, all of the other materials tested had marked activity only against hRSV.

Genetic diversity between human metapneumovirus subgroups

Complete consensus nucleotide sequences were determined for human metapneumovirus (HMPV) isolates CAN97-83 and CAN98-75, representing the two proposed genotypes or genetic subgroups of HMPV. The overall level of genome nucleotide sequence identity and aggregate proteome amino acid sequence identity between the two HMPV subgroups were 80 and 90%, respectively, similar to the respective values of 81 and 88% between the two antigenic subgroups of human respiratory syncytial virus (HRSV). The diversity between HMPV subgroups was greatest for the SH and G proteins (59 and 37% identity, respectively), which were even more divergent than their HRSV counterparts (72 and 55% cross-subgroup identity, respectively). It is reasonable to anticipate that the two genetic subgroups of HMPV represent antigenic subgroups approximately comparable to those of HRSV.

Emerging viral infections in a rapidly changing world

Emerging viral infections in both humans and animals have been reported with increased frequency in recent years. Recent advances have been made in our knowledge of some of these, including severe acute respiratory syndrome-associated coronavirus, influenza A virus, human metapneumovirus, West Nile virus and Ebola virus. Research efforts to mitigate their effects have concentrated on improved surveillance and diagnostic capabilities, as well as on the development of vaccines and antiviral agents. More attention needs to be given to the identification of the underlying causes for the emergence of infectious diseases, which are often related to anthropogenic social and environmental changes. Addressing these factors might help to decrease the rate of emergence of infectious diseases and allow the transition to a more sustainable society.

Human metapneumovirus detection in patients with severe acute respiratory syndrome

We used a combination approach of conventional virus isolation and molecular techniques to detect human metapneumovirus (HMPV) in patients with severe acute respiratory syndrome (SARS). Of the 48 study patients, 25 (52.1%) were infected with HMPV; 6 of these 25 patients were also infected with coronavirus, and another 5 patients (10.4%) were infected with coronavirus alone. Using this combination approach, we found that human laryngeal carcinoma (HEp-2) cells were superior to rhesus monkey kidney (LLC-MK2) cells commonly used in previous studies for isolation of HMPV. These widely available HEp-2 cells should be included in conjunction with a molecular method for cell culture followup to detect HMPV, particularly in patients with SARS.

Effects of human metapneumovirus and respiratory syncytial virus antigen insertion in two 3' proximal genome positions of bovine/human parainfluenza virus type 3 on virus replication and immunogenicity

A live attenuated bovine parainfluenza virus type 3 (PIV3), harboring the fusion (F) and hemagglutinin-neuraminidase (HN) genes of human PIV3, was used as a virus vector to express surface glycoproteins derived from two human pathogens, human metapneumovirus (hMPV) and respiratory syncytial virus (RSV). RSV and hMPV are both paramyxoviruses that cause respiratory disease in young children, the elderly, and immunocompromised individuals. RSV has been known for decades to cause acute lower respiratory tract infections in young children, which often result in hospitalization, while hMPV has only been recently identified as a novel human respiratory pathogen. In this study, the ability of bovine/human PIV3 to express three different foreign transmembrane surface glycoproteins and to induce a protective immune response was evaluated. The RNA-dependent RNA polymerase of paramyxoviruses binds to a single site at the 3' end of the viral RNA genome to initiate transcription of viral genes. The genome position of the viral gene determines its level of gene expression. The promoter-proximal gene is transcribed with the highest frequency, and each downstream gene is transcribed less often due to attenuation of transcription at each gene junction. This feature of paramyxoviruses was exploited using the PIV3 vector by inserting the foreign viral genes at the 3' terminus, at position 1 or 2, of the viral RNA genome. These locations were expected to yield high levels of foreign viral protein expression stimulating a protective immune response. The immunogenicity and protection results obtained with a hamster model showed that bovine/human PIV3 can be employed to generate bivalent PIV3/RSV or PIV3/hMPV vaccine candidates that will be further evaluated for safety and efficacy in primates.

Subgroup C avian metapneumovirus (MPV) and the recently isolated human MPV exhibit a common organization but have extensive sequence divergence in their putative SH and G genes

The genes encoding the putative small hydrophobic (SH), attachment (G) and polymerase (L) proteins of the Colorado isolate of subgroup C avian pneumovirus (APV) were entirely or partially sequenced. They all included metapneumovirus (MPV)-like gene start and gene end sequences. The deduced Colorado SH protein shared 26.9 and 21.7 % aa identity with its counterpart in human MPV (hMPV) and APV subgroup A, respectively, but its only significant aa similarities were to hMPV. Conserved features included a common hydrophobicity profile with an unique transmembrane domain and the conservation of most extracellular cysteine residues. The Colorado putative G gene encoded several ORFs, the longer of which encoded a 252 aa long type II glycoprotein with aa similarities to hMPV G only (20.6 % overall aa identity with seven conserved N-terminal residues). The putative Colorado G protein shared, at best, 21.0 % aa identity with its counterparts in the other APV subgroups and did not contain the extracellular cysteine residues and short aa stretch highly conserved in other APVs. The N-terminal end of the Colorado L protein exhibited 73.6 and 54.9 % aa identity with hMPV and APV subgroup A, respectively, with four aa blocks highly conserved among Pneumovirus: Phylogenetic analysis performed on the nt sequences confirmed that the L sequences from MPVs were genetically related, whereas analysis of the G sequences revealed that among MPVs, only APV subgroups A, B and D clustered together, independently of both the Colorado isolate and hMPV, which shared weak genetic relatedness at the G gene level.

Comparative evaluation of real-time PCR assays for detection of the human metapneumovirus

The human metapneumovirus (hMPV) is a new member of the Paramyxoviridae family associated with acute respiratory tract infections in humans. The objective of this study was to compare the sensitivity of real-time RT-PCR assays performed in a LightCycler instrument and designed to amplify the viral nucleoprotein (N), matrix (M), fusion (F), phosphoprotein (P), and polymerase (L) genes. In a first evaluation of 20 viral cultures with characteristics compatible with hMPV cytopathic effect, the PCR positivity rates were 100, 90, 75, 60, and 55% using primers for the N, L, M, P, and F genes. In a second evaluation of 10 nasopharyngeal aspirates from children with bronchiolitis and found to be positive for the hMPV N gene, the PCR positivity rates for the L, M, P, and F genes were 90, 60, 30, and 80%, respectively. The analytic sensitivity of the real-time RT-PCR assay for the hMPV N gene was 100 copies using a transcribed viral plasmid. In conclusion, real-time PCR assays aimed at amplifying the N and L genes which are coding for two internal viral proteins appear particularly suitable for hMPV diagnostic.

Human metapneumovirus associated with respiratory tract infections in a 3-year study of nasal swabs from infants in Italy

The newly described human metapneumovirus (hMPV) is reported here to be more commonly associated with lower respiratory tract disease. The present study examined nasal swab specimens from 90 infants with acute respiratory tract infections in Pisa, Italy, over a period of three respiratory virus seasons. The incidence of infection varied in each of the 3 years, with the rates of positivity for hMPV being 7% in 2001 but 37 and 43% in 2000 and 2002, respectively. hMPV was noted to occur seasonally in a pattern typical of the frequency of occurrence of respiratory syncytial virus. More than one-half (14 of 23) of the infants infected with hMPV had bronchopneumonia. One-third (9 of 23) of the hMPV-infected patients were also infected with another respiratory virus, a relationship that has not previously been reported. Mixed infections did not account for a higher percentage of cases of bronchopneumonia than hMPV infection alone did. Furthermore, 7 of 17 infants whose plasma was also tested for hMPV RNA were demonstrated to have virus in both nasal swab and blood specimens. The study indicates that hMPV is seen as commonly as other respiratory viruses, may be associated with severe respiratory disease in infants, can establish mixed infections with other respiratory viruses, and has a seasonal occurrence.

Respiratory syncytial virus nucleoprotein-specific cytotoxic T-cell epitopes in a South African population of diverse HLA types are conserved in circulating field strains

This study identifies memory cytotoxic T lymphocyte (CTL) epitopes to respiratory syncytial virus (RSV) in healthy South African adults and demonstrates the conservation of those epitopes in circulating field strains of RSV in South Africa. Thirty-seven healthy adults from a population with diverse HLA backgrounds were screened by gamma interferon (IFN-gamma) enzyme-linked immunospot for memory CTL activity in response to overlapping peptides representing the complete nucleoprotein (N) of RSV. Responses of more than 40 spot-forming cells/million cells were detectable in 21 individuals. The significant responses were further characterized, and 14-mer peptides were identified that induced cytolytic activity. Fine mapping of peptides with the highest cytolytic activity identified an HLA-B(*)08-restricted RSV-specific CTL epitope. The extended 14-mer peptide containing this epitope also induced lysis in the context of A(*)02-restricted target cells in some individuals. These HLA types are common in the target population; thus, the epitope is useful for studies of CTL responses to RSV in humans. The epitope was detected in healthy adults, reflecting the response generated in the course of previous natural RSV infection. We obtained a large panel of naturally occurring isolates of RSV to determine whether there was evidence of escape from CTL activity in circulating strains. We found that this epitope and a previously identified B(*)07-restricted N protein epitope were conserved in RSV field strains representing the diversity of circulating genotypes. This work suggests that escape from CTL activity is not common for this acute respiratory infection.

High prevalence of human metapneumovirus infection in young children and genetic heterogeneity of the viral isolates

RNA of the newly identified human metapneumovirus (HMPV) was detected in nasopharyngeal aspirates of 11 of 63 (17.5%) young children with respiratory tract disease. Markers of infection caused by another member of the Pneumovirinae subfamily of the family Paramyxoviridae, respiratory syncytial virus (RSV), were identified in 15 of these patients (23.8%). Three patients were simultaneously infected with HMPV and RSV. Studies of the clinical characteristics of HMPV-infected children did not reveal any difference between HMPV-infected patients and a control population of RSV-infected patients with regard to disease severity, but the duration of symptoms was significantly shorter for HMPV-infected patients. Phylogenetic analysis of the amplified viral genome fragments confirmed the existence and simultaneous circulation within one epidemic season of HMPV isolates belonging to two genetic lineages.

Children with respiratory disease associated with metapneumovirus in Hong Kong

Human metapneumovirus (HMPV) is a newly discovered pathogen thought to be associated with respiratory disease. We report the results of a study of 587 children hospitalized with respiratory infection over a 13-month period. HMPV was detected in the nasopharyngeal aspirates from 32 (5.5%) children by reverse transcription-polymerase chain reaction. HMPV infection was associated with clinical diagnoses of pneumonia (36%), asthma exacerbation (23%), or acute bronchiolitis (10%). When compared to those with respiratory syncytial virus infection, children with HMPV infection were older, and wheezing was more likely to represent asthma exacerbation rather than acute bronchiolitis. HMPV viral activity peaked during the spring-summer period in Hong Kong. Phylogenetically, all HMPV virus strains from Hong Kong belonged to one of the two genetic lineages previously described. HMPV contributed to 441.6 hospital admissions per 100,000 population <6 years of age.

Sequence analysis of the matrix (M2) protein gene of avian pneumovirus recovered from turkey flocks in the United States

We here report the comparative sequence and phylogenetic analysis of the avian pneumovirus subgroup C (APV C) matrix (M2) gene of cell culture-adapted isolates and clinical samples. Limited heterogeneity was observed among the M2 sequences, suggesting that diagnostic tests and vaccines against APV C are likely to exhibit broad cross-reactivity.

The classification of viruses infecting the respiratory tract

Following the boom in respiratory virology in the 1960s, species of rhinoviruses, coronaviruses, enteroviruses, adenoviruses, parainfluenza viruses and respiratory syncytial virus were added to influenza and measles viruses as causes of respiratory tract infection. In restricted patient groups, such as the immunocompromised, members of the family of herpesviruses including herpes simplex, cytomegalovirus, varicella-zoster virus, Epstein-Barr virus and human herpes virus 6 have also been associated with respiratory disease. This list of pathogens was extended last year with the discovery of a novel virus, the human metapneumovirus. More than 200 antigenically distinct viruses have been documented as causes of sporadic or epidemic respiratory infections in infants, children and adults. However, this varied and diverse group can be divided among six distinct families. Understanding some of the basic biology of these families gives an insight into possible strategies for diagnosis, control and therapy.

Immunology of viral respiratory tract infection in infancy

Respiratory viruses such as respiratory syncytial virus (RSV), parainfluenza viruses (PIV) and the influenza viruses cause severe lower respiratory tract disease in infants and children throughout the world. We discuss the recent discovery of the epidemiologic importance of the human metapneumoviruses, first reported in 2001. Experimental live-attenuated vaccines for each of these viruses are being developed for intranasal administration in the first weeks or months of life. The immunology of these infections in humans is poorly defined but many studies are ongoing. A significant obstacle to successful immunisation of infants against respiratory-virus-associated disease early in life may be the relatively poor immune response of very young infants to primary virus infection. This paper reviews the immune correlates of protection against disease caused by these viruses, immune responses of infants to naturally acquired infection or experimental infection with candidate vaccine viruses and the genetics of susceptibility to severe disease.

Human metapneumovirus: a newly emerging respiratory pathogen

PURPOSE OF REVIEW

The present review focuses on the recent discovery, and clinical and epidemiological features of a virus associated with respiratory tract infections.

RECENT FINDINGS

In June 2001, researchers in The Netherlands reported the discovery of a virus associated with respiratory tract disease in infants and children. Genetic studies of this newly discovered viral pathogen revealed that it was a paramyxovirus. This virus is the first human pathogen in the Genus Metapneumovirus and was called human metapneumovirus (hMPV). hMPV may be a common respiratory virus. Seroepidemiologic studies in The Netherlands suggested that, by age 5 years, nearly all individuals have been exposed to hMPV. The results of several studies suggest that hMPV may account for about 10% of respiratory tract infections in which a common respiratory virus, such as respiratory syncytial virus, or influenza or parainfluenza viruses, could not be detected. hMPV has been detected in patients with either upper or lower respiratory tract disease, or both. Symptoms associated with hMPV include cough, dyspnea, wheeze, and hypoxia. This newly recognized pathogen has been detected in children and adults. Epidemiological findings suggest that it may circulate worldwide and may have a seasonal distribution.

SUMMARY

hMPV is a newly emerging respiratory pathogen and may be the cause of a significant proportion of both upper and lower respiratory tract infection in infants, children, and adults.

Human metapneumovirus infections in hospitalized children

We evaluated the percentage of hospitalizations for acute respiratory tract infections in children < or =3 years of age attributable to human metapneumovirus (HMPV) and other respiratory viruses in a prospective study during winter and spring 2002. We used real-time polymerase chain assays and other conventional diagnostic methods to detect HMPV, human respiratory syncytial virus (HRSV), and influenza viruses in nasopharyngeal aspirates of children. HMPV was detected in 12 (6%) of the 208 children hospitalized for acute respiratory tract infections, HRSV in 118 (57%), and influenza A in 49 (24%). Bronchiolitis was diagnosed in 8 (68%) and pneumonitis in 2 (17%) of HMPV-infected children; of those with HRSV infection, bronchiolitiss was diagnosed in 99 (84%) and pneumonitis in 30 (25%). None of the HMPV-infected children was admitted to an intensive-care unit, whereas 15% of those with HRSV or influenza A infections were admitted. HMPV is an important cause of illness in young children with a similar, although less severe, clinical presentation to that of HRSV.

Sequence analysis of the N, P, M and F genes of Canadian human metapneumovirus strains

The complete nucleotide sequences of the nucleoprotein (N), phosphoprotein (P), matrix protein (M), and fusion protein (F) genes of 15 Canadian human metapneumovirus (hMPV) isolates were determined. Phylogenetic analysis revealed two distinct genetic clusters, or groups for each gene with additional sequence variability within the individual groups. Comparison of the deduced amino acid sequences for the N, M and F genes of the different isolates revealed that all three genes were well conserved with 94.1-97.6% identity between the two distinct clusters The P gene showed more diversity with 81.6-85.7% amino acid identity for isolates between the two clusters, and 94.6-100% for isolates within the same cluster.

Deduced amino acid sequence of the small hydrophobic protein of US avian pneumovirus has greater identity with that of human metapneumovirus than those of non-US avian pneumoviruses

We report here the nucleotide and deduced amino acid (aa) sequences of the small hydrophobic (SH) gene of the avian pneumovirus strain Colorado (APV/CO). The SH gene of APV/CO is 628 nucleotides in length from gene-start to gene-end. The longest ORF of the SH gene encoded a protein of 177 aas in length. Comparison of the deduced aa sequence of the SH protein of APV/CO with the corresponding published sequences of other members of genera metapneumovirus showed 28% identity with the newly discovered human metapneumovirus (hMPV), but no discernable identity with the APV subgroup A or B. Collectively, this data supports the hypothesis that: (i) APV/CO is distinct from European APV subgroups and belongs to the novel subgroup APV/C (APV/US); (ii) APV/CO is more closely related to hMPV, a mammalian metapneumovirus, than to either APV subgroup A or B. The SH gene of APV/CO was cloned using a genomic walk strategy which initiated cDNA synthesis from genomic RNA that traversed the genes in the order 3'-M-F-M2-SH-G-5', thus confirming that gene-order of APV/CO conforms in the genus Metapneumovirus. We also provide the sequences of transcription-signals and the M-F, F-M2, M2-SH and SH-G intergenic regions of APV/CO.

Identification of amino acids that are critical to the processivity function of respiratory syncytial virus M2-1 protein

The M2-1 protein of respiratory syncytial virus (RSV) is a transcription processivity factor that is essential for virus replication. The function of RSV M2-1 protein can be examined by using an RSVlacZ minigenome assay in vitro since the expression of the lacZ gene is dependent on M2-1. The M2-1 protein of pneumonia virus of mice (PVM), also a member of the Pneumovirus genus, functions poorly in the RSVlacZ minigenome assay despite conservation of the Cys(3)-His(1) motif at its N terminus and an overall 40% amino acid identity with RSV M2-1. To identify the amino acids responsible for the differences between these two proteins, two chimeric proteins were constructed. The RSV/PVM (RP) M2-1 chimera that contains the N-terminal 30 amino acids from RSV and the remaining C-terminal 148 amino acids from PVM maintained a level of activity at an ca. 36% of RSV M2-1. However, the PVM/RSV (PR) M2-1 chimera with the N-terminal 29 amino acids from PVM and 164 amino acids from RSV had an activity of <5% of RSV M2-1, indicating that the functional determinants are mainly located in the N terminus of M2-1. Mutagenesis of the N terminus of PR M2-1 and RSV M2-1 identified that Leu-16 and Asn-17 of RSV M2-1 are critical to the M2-1 function. In addition, several charged residues in the N terminus of RSV M2-1 also contributed to the functional integrity of M2-1.

Nucleotide and predicted amino acid sequence-based analysis of the avian metapneumovirus type C cell attachment glycoprotein gene: phylogenetic analysis and molecular epidemiology of U.S. pneumoviruses

A serologically distinct avian metapneumovirus (aMPV) was isolated in the United States after an outbreak of turkey rhinotracheitis (TRT) in February 1997. The newly recognized U.S. virus was subsequently demonstrated to be genetically distinct from European subtypes and was designated aMPV serotype C (aMPV/C). We have determined the nucleotide sequence of the gene encoding the cell attachment glycoprotein (G) of aMPV/C (Colorado strain and three Minnesota isolates) and predicted amino acid sequence by sequencing cloned cDNAs synthesized from intracellular RNA of aMPV/C-infected cells. The nucleotide sequence comprised 1,321 nucleotides with only one predicted open reading frame encoding a protein of 435 amino acids, with a predicted M(r) of 48,840. The structural characteristics of the predicted G protein of aMPV/C were similar to those of the human respiratory syncytial virus (hRSV) attachment G protein, including two mucin-like regions (heparin-binding domains) flanking both sides of a CX3C chemokine motif present in a conserved hydrophobic pocket. Comparison of the deduced G-protein amino acid sequence of aMPV/C with those of aMPV serotypes A, B, and D, as well as hRSV revealed overall predicted amino acid sequence identities ranging from 4 to 16.5%, suggesting a distant relationship. However, G-protein sequence identities ranged from 72 to 97% when aMPV/C was compared to other members within the aMPV/C subtype or 21% for the recently identified human MPV (hMPV) G protein. Ratios of nonsynonymous to synonymous nucleotide changes were greater than one in the G gene when comparing the more recent Minnesota isolates to the original Colorado isolate. Epidemiologically, this indicates positive selection among U.S. isolates since the first outbreak of TRT in the United States.

Subtype B avian metapneumovirus resembles subtype A more closely than subtype C or human metapneumovirus with respect to the phosphoprotein, and second matrix and small hydrophobic proteins

Avian metapneumovirus (aMPV) subtype B (aMPV/B) nucleotide sequences were obtained for the phosphoprotein (P), second matrix protein (M2), and small hydrophobic protein (SH) genes. By comparison with sequences from other metapneumoviruses, aMPV/B was most similar to subtype A aMPV (aMPV/A) relative to the US subtype C isolates (aMPV/C) and human metapneumovirus (hMPV). Strictly conserved residues common to all members of the Pneumovirinae were identified in the predicted amino acid sequences of the P and M2 protein-predicted amino acid sequences. The Cys(3)-His(1) motif, thought to be important for binding zinc, was also present in the aMPV M2 predicted protein sequences. For both the P and M2-1 protein-predicted amino acid sequences, aMPV/B was most similar to aMPV/A (72 and 89% identity, respectively), having only approximately 52 and 70% identity, respectively, relative to aMPV/C and hMPV. Differences were more marked in the M2-2 proteins, subtype B having 64% identity with subtype A but < or = 25% identity with subtype C and hMPV. The A and B subtypes of aMPV had predicted amino acid sequence identities for the SH protein of 47%, and less than 20% with that of hMPV. An SH gene was not detected in the aMPV/C. Phylogenetically, aMPV/B clustered with aMPV/A, while aMPV/C grouped with hMPV.

Human metapneumovirus in a haematopoietic stem cell transplant recipient with fatal lower respiratory tract disease

Respiratory viruses are increasingly recognized as a cause of pneumonitis following haematopoietic stem cell transplantation (HSCT). However, frequently, no pathogen is identified in cases of suspected viral pneumonia. Recently, a previously undescribed paramyxovirus, designated 'human metapneumovirus' (hMPV), was isolated from children with respiratory illness. We have detected hMPV as the sole pathogen in the nasopharyngeal aspirate of an HSCT recipient who succumbed to progressive respiratory failure following an upper respiratory prodrome. This report highlights the importance of further studies to elucidate the role of hMPV in causing respiratory illnesses in the HSCT population.

Metapneumoviruses in birds and humans

Avian pneumovirus (APV, Turkey rhinotracheitis virus) and Human metapneumovirus (hMPV) are pathogens of birds and humans, respectively, that are associated with upper respiratory tract infections. Based on their different genomic organization and low level of nucleotide (nt) and amino acid (aa) identity with paramyxoviruses in the genus Pneumovirus, APV and hMPV have been classified into a new genus referred to as Metapneumovirus. First isolated in 1970s, APV strains have since been isolated in Europe, Africa, middle east, and United States (US) and classified in four subgroups, APV/A, APV/B, APV/C, and APV/D based on nt and predicted aa sequence identity. Although it was first isolated in 2001, serological evidence indicates that hMPV may have been present in human population from as early as the 1950s. There is only one subgroup of hMPV so far, whose nt and aa sequence identity indicates that it is more closely related to APV/C than to APV/A, APV/B, or APV/D.

Characterization of avian metapneumoviruses isolated in the USA

Avian pneumovirus (APV; officially known as turkey rhinotracheitis virus) is an emergent pathogen of birds in the USA that results in upper respiratory tract disease in turkeys. Six years after the first outbreak in the USA, the disease continues to ravage turkey flocks, primarily in the state of Minnesota. From 1997 to 2000, the industry recorded losses estimated at 15 million US dollars per annum. Researchers have developed sensitive diagnostic techniques, including the enzyme-linked immunosorbent assay and the reverse transcriptase-polymerase chain reaction. which, when used together, are highly sensitive in detecting APV outbreaks in commercial turkey flocks. Phylogenetic analysis of the nucleotide and predicted amino acid sequence of 15 US viruses isolated between 1996 and 2000 demonstrated that the US viruses are relatively homogenous but different from the European APV subgroups A and B, resulting in the classification of US isolates into subgroup C. Infectious APV was isolated from sentinel waterfowls placed close to an infected commercial turkey farm and from wild Canada geese captured in Minnesota, suggesting that free-ranging birds may be involved in the spread of APV. Current efforts to prevent and control the infection include improving management and biosecurity practices and developing attenuated live and deletion mutant vaccines capable of conferring protection.

Human metapneumovirus as a cause of community-acquired respiratory illness

Human metapneumovirus (HMPV) is a recently identified Paramyxovirus first isolated from hospitalized children with acute respiratory tract infections (ARTI). We sought evidence of HMPV infection in patients who had visited general practitioners, had influenzalike illnesses (ILI), and had negative tests for influenza and Human respiratory syncytial virus (HRSV). As part of national virologic surveillance, sentinel general practices in England and Wales collected samples from patients of all ages with ILI during winter 2000-01. Reverse transcriptase-polymerase chain reaction (PCR) for HMPV, influenza A (H1 and H3), influenza B, and HRSV (A and B) was used to screen combined nose and throat swabs. PCR products from the HMPV-positive samples were sequenced to confirm identity and construct phylogenetic trees. Of 711 swabs submitted, 408 (57.3%) were negative for influenza and HRSV; HMPV was identified in 9 (2.2%) patients. HMPV appears to be associated with community-acquired ARTI. The extent of illness and possible complications related to this new human virus need to be clarified.