Human metapneumovirus G protein is highly conserved within but not between genetic lineages

Characterization of prefusion-F-specific antibodies elicited by natural infection with human metapneumovirus

Human metapneumovirus (hMPV) is a major cause of acute respiratory infections in infants and older adults, for which no vaccines or therapeutics are available. The viral fusion (F) glycoprotein is required for entry and is the primary target of neutralizing antibodies; however, little is known about the humoral immune response generated from natural infection. Here, using prefusion-stabilized F proteins to interrogate memory B cells from two older adults, we obtain over 700 paired non-IgM antibody sequences representing 563 clonotypes, indicative of a highly polyclonal response. Characterization of 136 monoclonal antibodies reveals broad recognition of the protein surface, with potently neutralizing antibodies targeting each antigenic site. Cryo-EM studies further reveal two non-canonical sites and the molecular basis for recognition of the apex of hMPV F by two prefusion-specific neutralizing antibodies. Collectively, these results provide insight into the humoral response to hMPV infection in older adults and will help guide vaccine development.

The A2c 111nt-dup Variants of Human Metapneumovirus Predominantly Circulating in Qingdao, China, during 2018 and 2019

BACKGROUND

Human metapneumovirus (HMPV) plays an important role in acute respiratory tract infections, especially in children. We investigated the epidemiology of HMPV associated with acute respiratory tract infections (ARTIs) among pediatric inpatients and identified HMPV genetic variations in Qingdao, China, from January 2018 to June 2019.

METHODS

HMPV-positive samples were identified from throat swabs by multiplex real-time RT-PCR. The G gene sequences of HMPV were obtained, followed by phylogenetic analysis.

RESULTS

As a result, 71 out of 1051 (6.76%) patients were HMPV positive, and the HMPV-positive rate in children under 5 years of age was three times higher than that in those aged 5-17 years. The epidemic season of HMPV was in spring, with a peak mainly in March. Thirty-two nucleotide sequences of the HMPV G gene successfully obtained were clustered into 3 genotypes, A2c (25/32, 78.13%), B1 (3/32, 9.38%) and B2 (4/32, 12.50%). In addition, 76% (19/25) of A2c viruses were identified as the emerging A2c_111nt-dup variants, which were predominantly circulating among pediatric inpatients with ARTIs between January 2018 and June 2019 in Qingdao.

CONCLUSIONS

The emerging A2c_111nt-dup variants have spread between countries and cities and might spread more widely in the future. Further prevalence monitoring of this duplication variant is needed to clarify the potentially expanding transmission and to provide a scientific basis for disease control and vaccine development. This article is protected by copyright. All rights reserved.

Zoonotic Origins of Human Metapneumovirus: A Journey from Birds to Humans

Metapneumoviruses, members of the family Pneumoviridae, have been identified in birds (avian metapneumoviruses; AMPV’s) and humans (human metapneumoviruses; HMPV’s). AMPV and HMPV are closely related viruses with a similar genomic organization and cause respiratory tract illnesses in birds and humans, respectively. AMPV can be classified into four subgroups, A–D, and is the etiological agent of turkey rhinotracheitis and swollen head syndrome in chickens. Epidemiological studies have indicated that AMPV also circulates in wild bird species which may act as reservoir hosts for novel subtypes. HMPV was first discovered in 2001, but retrospective studies have shown that HMPV has been circulating in humans for at least 50 years. AMPV subgroup C is more closely related to HMPV than to any other AMPV subgroup, suggesting that HMPV has evolved from AMPV-C following zoonotic transfer. In this review, we present a historical perspective on the discovery of metapneumoviruses and discuss the host tropism, pathogenicity, and molecular characteristics of the different AMPV and HMPV subgroups to provide increased focus on the necessity to better understand the evolutionary pathways through which HMPV emerged as a seasonal endemic human respiratory virus.

Phylogenetic variability of Human Metapneumovirus in patients with acute respiratory infections in Cameroon, 2011-2014

BACKGROUND

Identified in 2001, Human Metapneumovirus (HMPV) is a Pneumovirus associated with acute lower and upper respiratory infections in all age groups and especially in newborns, elderly and immunocompromised subjects. Data are still limited in sub-Saharan African countries genetic characterization of this respiratory virus. This study reports the genetic variability of HMPV strains in Cameroonian children for 3 consecutive epidemic seasons (September 2011-October 2014).

METHODS

A prospective surveillance was conducted to identify inpatient and outpatient children less than 15 years with respiratory symptoms ≤5 days. The nasopharyngeal samples were tested for HMPV using a multiplex polymerase chain reaction. Viral distribution and demographic data were analyzed statistically. Positive samples for HMPV were amplified by semi-nested polymerize chain reaction and then partially sequenced at the G gene. Phylogenetic analyzes were performed on the partial nucleotide and protein sequences of the G gene.

RESULTS

From September 2011 to October 2014, 822 children under 15 years were enrolled in the study. HMPV was identified in each of 3.9% (32/822) of children. HMPV were detected throughout the year. HMPV-A (73.3%; 11/15) was predominant compared to HMPV-B (26.7; 4/15). Cameroonian HMPV strains are grouped among the members of genotype A2b (for HMPV-A), B1 and B2 (for HMPV-B).

CONCLUSION

This study suggests that about 4% of ARI recorded in children in Cameroon are caused by HMPV. The present study is also the first report on the genetic variability of the G gene of HMPV strains in the region. Although this work partially fills gaps for some information, additional studies are required to clarify the molecular epidemiology and evolutionary pattern of HMPV in sub-Saharan Africa in general and more particularly in Cameroon.

Protection against influenza infection requires early recognition by inflammatory dendritic cells through C-type lectin receptor SIGN-R1

The early phase of influenza infection occurs in the upper respiratory tract and the trachea, but little is known about the initial events of virus recognition and control of viral dissemination by the immune system. Here, we report that inflammatory dendritic cells (IDCs) are recruited to the trachea shortly after influenza infection through type I interferon-mediated production of the chemokine CCL2. We further show that recruited IDCs express the C-type lectin receptor SIGN-R1, which mediates direct recognition of the virus by interacting with N-linked glycans present in glycoproteins of the virion envelope. Activation of IDCs via SIGN-R1 triggers the production of the chemokines CCL5, CXCL9 and CXCL10, which initiate the recruitment of protective natural killer (NK) cells in the infected trachea. In the absence of SIGN-R1, the recruitment and activation of NK cells is impaired, leading to uncontrolled viral proliferation. In sum, our results provide insight into the orchestration of the early cellular and molecular events involved in immune protection against influenza.

Human metapneumovirus - what we know now

Human metapneumovirus (HMPV) is a leading cause of acute respiratory infection, particularly in children, immunocompromised patients, and the elderly. HMPV, which is closely related to avian metapneumovirus subtype C, has circulated for at least 65 years, and nearly every child will be infected with HMPV by the age of 5. However, immunity is incomplete, and re-infections occur throughout adult life. Symptoms are similar to those of other respiratory viral infections, ranging from mild (cough, rhinorrhea, and fever) to more severe (bronchiolitis and pneumonia). The preferred method for diagnosis is reverse transcription-polymerase chain reaction as HMPV is difficult to culture. Although there have been many advances made in the past 16 years since its discovery, there are still no US Food and Drug Administration-approved antivirals or vaccines available to treat HMPV. Both small animal and non-human primate models have been established for the study of HMPV. This review will focus on the epidemiology, transmission, and clinical manifestations in humans as well as the animal models of HMPV pathogenesis and host immune response.

Human metapneumovirus in the preterm neonate: current perspectives

Premature birth (<37 weeks gestation) occurs in ~11% of all births in the US. These infants are at risk of chronic lung disease and respiratory conditions, including bronchopulmonary dysplasia. Respiratory viruses are important causes of acute respiratory illness (ARI) in preterm infants, leading to rehospitalization, increased health care burden, and long-term morbidity. Human metapneumovirus (HMPV) is a paramyxovirus discovered in 2001 that is related to respiratory syncytial virus. Epidemiologic studies show that HMPV is a leading cause of ARI in children and adults worldwide. Prematurity is a major risk factor for severe HMPV disease, requiring hospitalization. Moreover, limited data suggest that HMPV infection during infancy is associated with asthma and recurrent wheezing, which are common long-term pulmonary complication of prematurity. HMPV causes nosocomial outbreaks of ARI in hospitals and long-term care facilities, although there are few studies of the prevalence of HMPV in neonatal intensive care unit populations. HMPV is a common and important virus in premature infants, and caregivers for preterm infants should consider this virus in patients with acute respiratory symptoms.

Human Metapneumovirus

Human metapneumovirus (HMPV), a paramyxovirus identified in 2001, is a leading cause of respiratory tract infections in both children and adults. Seroprevalence studies demonstrate that the primary infection occurs before the age of 5 years, and humans are reinfected throughout life. The four subgroups of HMPV occur with year-to-year variability, and infection with one subgroup confers some serologic cross-protection. Experimental vaccines elicit a humoral response in both animal and human models and have been used to identify antigenic determinants. The main target of protective antibodies is the fusion (F) protein, although many of the remaining eight proteins are immunogenic. Monoclonal antibodies (mAbs) targeting the F protein are both protective and therapeutic in animal models. Most recently, the identification of broadly neutralizing antibodies against HMPV and respiratory syncytial virus demonstrates that common epitopes are present between the two viruses. Broadly neutralizing mAbs have significant clinical implications for prophylaxis and treatment of high-risk hosts as well as vaccine development.

Phylogenetic analysis of human metapneumovirus detected in hospitalized patients in Kuwait during the years 2009-2011

BACKGROUND

Human metapneumovirus (hMPV) is an important cause of both upper and lower respiratory tract infections (RTIs) in all age groups. Children, elderly, and immunocompromised individuals are the most affected groups. HMPV infection accounts for 5% of hospitalized patients with respiratory tract infections in Kuwait. It is mostly detected among infants and elderly age groups, and both hMPV genotypes A and B circulate in Kuwait.

METHODS

In this study, the genetic diversity of detected hMPV was evaluated, and a phylogenetic analysis based on partial nucleotide and amino acid sequences of the G gene was performed for hMPV detected among hospitalized patients with RTIs.

RESULTS

Our results showed that 62% of hMPV sequences belonged to the A genotype and 38% to the B genotype. A2b and B2 subtypes were detected and circulated during the study period, whereas A1 and B1 subtypes were not detected. Based on nucleotide sequences of the G gene, most of hMPV strains (57%) were clustered with Indian strains, followed by Greek strains (24%) and Canadian strains (14%). One strain (5%) clustered within the B genotype but had different branches than B1 and B2 branches.

CONCLUSION

Our data showed the co-circulation of hMPV genotypes A2b and B2 in Kuwait with genetic diversity suggestive of evolution through negative selection.

Programmed death-1 impairs secondary effector lung CD8⁺ T cells during respiratory virus reinfection

Reinfections with respiratory viruses are common and cause significant clinical illness, yet precise mechanisms governing this susceptibility are ill defined. Lung Ag-specific CD8(+) T cells (T(CD8)) are impaired during acute viral lower respiratory infection by the inhibitory receptor programmed death-1 (PD-1). To determine whether PD-1 contributes to recurrent infection, we first established a model of reinfection by challenging B cell-deficient mice with human metapneumovirus (HMPV) several weeks after primary infection, and found that HMPV replicated to high titers in the lungs. A robust secondary effector lung TCD8 response was generated during reinfection, but these cells were more impaired and more highly expressed the inhibitory receptors PD-1, LAG-3, and 2B4 than primary T(CD8). In vitro blockade demonstrated that PD-1 was the dominant inhibitory receptor early after reinfection. In vivo therapeutic PD-1 blockade during HMPV reinfection restored lung T(CD8) effector functions (i.e., degranulation and cytokine production) and enhanced viral clearance. PD-1 also limited the protective efficacy of HMPV epitope-specific peptide vaccination and impaired lung T(CD8) during heterotypic influenza virus challenge infection. Our results indicate that PD-1 signaling may contribute to respiratory virus reinfection and evasion of vaccine-elicited immune responses. These results have important implications for the design of effective vaccines against respiratory viruses.