New antiviral approaches for human parainfluenza: Inhibiting the haemagglutinin-neuraminidase

Molecular Evolution of the Fusion (F) Genes in Human Parainfluenza Virus Type 2

Human parainfluenza virus type 2 (HPIV2) is a clinically significant respiratory pathogen, which highlights the necessity of studies on its molecular evolution. This study investigated the evolutionary dynamics, phylodynamics, and structural characteristics of the HPIV2 fusion (F) gene using a comprehensive dataset spanning multiple decades and geographic regions. Phylogenetic analyses revealed two distinct clusters of HPIV2 F gene sequences, which were estimated to have diverged from a common ancestor approximately a century ago. Cluster 1 demonstrated a higher evolutionary rate and genetic diversity compared to the more stable cluster 2. Bayesian Skyline Plot analyses indicated a significant increase in the effective population size of the F gene between 2005 and 2015; potentially linked to enhanced diagnostic and surveillance capabilities. Structural modeling identified conserved conformational epitopes predominantly in the apex and stalk regions of the F protein. These findings underscore the evolutionary constraints and antigenic landscape of the HPIV2 F protein.

Analysis of neuraminidase activity of human parainfluenza viruses using enzyme-linked lectin assay and BTP3-Neu5Ac assay

Human parainfluenza viruses (hPIVs) are causative agents of upper and lower respiratory tract infections and they have four serotypes. The virion surface displays hemagglutinin-neuraminidase (HN), having hemagglutinating (HA) and neuraminidase (NA) activities in a single molecule. The HA activity binds the virion to sialic acid on the viral receptor on host cells and the NA releases the progeny viruses from the cell surface. There are several methods for assaying viral NA activity, such as the thiobarbituric acid assay, 4-methylumbelliferyl-N-acetyl-α-d-neuraminic acid assay, NA-Star assay, and enzyme-linked lectin assay (ELLA). However, these are mainly used for influenza viruses and not for hPIVs. A fluorescent-based cytochemical NA assay using BTP3-Neu5Ac as the substrate was recently developed and used for orthomyxo- and paramyxoviruses, including types 1 and 3 hPIVs. In this study, we used the ELLA, and BTP-Neu5Ac assay for 14 field isolate strains of hPIVs including all four serotypes. The reaction in ELLA at pH 6.5 using peanut agglutinin (PNA) as a lectin was very low for all tested viruses except a type 3 virus strain with the maximum reaction at pH 6.5 and the acidic conditions did not enhance the reaction. ELLA with another lectin, Erythrina cristagalli agglutinin exhibited significant and stronger reactions than with PNA in some strains of types 1 and 3 viruses. The BTP3-Neu5Ac assay showed a fluorescent signal on cells infected with all the viruses except the hPIV1/Sendai/713/2018 strain in LLC-MK2 and/or MNT-1. The signal was detected in cell-free virus, as well, in all the viruses except the hPIV4a/Sendai/3935/2003 strain. The strength of the signal varied among viral strains but it was stronger in the reaction at pH 4.0 than pH 7.0 and strongest in type 2 hPIVs.

Drug repurposing to tackle parainfluenza 3 based on multi-similarities and network proximity analysis

Given that there is currently no clinically approved drug or vaccine for parainfluenza 3 (PIV3), we applied a drug repurposing method based on disease similarity and chemical similarity to screen 2,585 clinically approved chemical drugs using PIV3 potential drugs BCX-2798 and zanamivir as our controls. Twelve candidate drugs were obtained after being screened with good disease similarity and chemical similarity (S > 0.50, T > 0.56). When docking them with the PIV3 target protein, hemagglutinin-neuraminidase (HN), only oseltamivir was docked with a better score than BCX-2798, which indicates that oseltamivir has an inhibitory effect on PIV3. After the distance (Z d c ) between the drug target of 14 drugs and the PIV3 disease target was measured by the network proximity method based on the PIV3 disease module, it was found that theZ d c values of amikacin, oseltamivir, ribavirin, and streptomycin were less than those of the control. Thus, oseltamivir is the best potential drug because it met all the above screening requirements. Additionally, to explore whether oseltamivir binds to HN stably, molecular dynamics simulation of the binding of oseltamivir to HN was carried out, and the results showed that the RMSD value of the complex tended to be stable within 100 ns, and the binding free energy of the complex was low (-10.60 kcal/mol). It was proved that oseltamivir screened by our drug repurposing method had the potential feasibility of treating PIV3.

Novel sialidase inhibitors suppress mumps virus replication and infection

The prevalent human pathogen, mumps virus (MuV; orthorubulavirus parotitidis) causes various complications and serious sequelae, such as meningitis, encephalitis, deafness, and impaired fertility. Direct-acting antivirals (DAAs) targeting MuV which can prevent mumps and mumps-associated complications and sequelae are yet to be developed. Paramyxoviridae family members, such as MuV, possess viral surface hemagglutinin-neuraminidase (HN) protein with sialidase activity which facilitates efficient viral replication. Therefore, to develop DAAs targeting MuV we synthesized MuV sialidase inhibitors. It is proposed that the viral HN has a single functional site for N-acetylneuraminic acid (Neu5Ac) binding and sialidase activity. Further, the known MuV sialidase inhibitor is an analog of Neu5Ac-2,3-didehydro-2-deoxy-N-acetylneuraminic acid (DANA)-which lacks potency. DANA derivatives with higher MuV sialidase inhibitory potency are lacking. The MuV-HN-Neu5Ac binding site has a hydrophobic cavity adjacent to the C4 position of Neu5Ac. Exploiting this, here, we synthesized DANA derivatives with increasing hydrophobicity at its C4 position and created 3 novel sialidase inhibitors (Compounds 1, 2, and 3) with higher specificity for MuV-HN than DANA; they inhibited MuV replication step to greater extent than DANA. Furthermore, they also inhibited hemagglutination and the MuV infection step. The insight-that these 3 novel DANA derivatives possess linear hydrocarbon groups at the C4-hydroxyl group of DANA-could help develop highly potent sialidase inhibitors with high specificity for MuV sialidase, which may function as direct-acting MuV-specific antivirals.

Changing respiratory pathogens infection patterns after COVID-19 pandemic in Shanghai, China

To assess the positive rate of 11 respiratory pathogens in 2023, providing a comprehensive summary and analysis of the respiratory infection patterns after COVID-19 pandemic. The study comprised 7544 inpatients suspected of respiratory infections who underwent respiratory pathogen multiplex polymerase chain reaction tests from July 2022 to December 31, 2023. We analyzed the positive rate of 11 pathogens over 18 months and the characterization of infection patterns among different age groups and immune states. Among 7544 patients (age range 4 months to 104 years, 44.99% female), the incidence of infected by at least one of the 11 pathogens was 26.07%. Children (55.18%, p < 0.05) experienced a significantly higher infection probability than adults (20.88%) and old (20.66%). Influenza A virus (8.63%), Mycoplasma pneumoniae (5.47%), and human rhinovirus (5.12%) were the most common pathogens. In children, M. pneumoniae (35.96%) replaced the predominant role of human respiratory syncytial virus (HRSV) (5.91%) in the pathogen spectrum. Age, immunosuppressed state, and respiratory chronic conditions were associated with a significantly higher risk of mixed infection. Immunosuppressed patients were more vulnerable to human coronavirus (4.64% vs. 1.65%, p < 0.05), human parainfluenza virus (3.46% vs. 1.69%, p < 0.05), and HRSV (2.27% vs. 0.55%, p < 0.05). Patterns in respiratory infections changed following regional epidemic control measures and the COVID-19 pandemic.

Interplay of Modified Sialic Acid Inhibitors and the Human Parainfluenza Virus 1 Hemagglutinin-Neuraminidase Active Site

In the search for effective antivirals against Paramyxoviridae, the dynamics of human parainfluenza virus type 1 hemagglutinin-neuraminidase (hPIV1-HN) inhibition offers a promising perspective. This study focuses on the potential of C5- and C4-modified 2,3-unsaturated sialic acid (DANA) inhibitors and highlights their interaction with the hPIV1-HN enzyme. We show that a strategic substitution, replacing the C5 isopropyl group in BCX 2798 with a trifluoroacetyl function, increases inhibitory potency 3- to 4-fold. At the same time, we explore the special properties of the catalytic site of hPIV1-HN, which harbors only small substituents and favors a C4 sulfonylamido function over a carbonyl function, in contrast to the C4 pocket of Newcastle disease virus hemagglutinin-neuraminidase (NDV-HN). Based on these findings, we present a newly identified potent inhibitor that has the preferred C5 trifluoroacetamido and C4 trifluorosulfonylamide groups. The results of this study pave the way for a deeper understanding of the C4 and C5 binding pockets of hPIV1-HN and promote the development of new, more selective inhibitors.

Arbidol: The current demand, strategies, and antiviral mechanisms

BACKGROUND

High morbidity and mortality of influenza virus infection have made it become one of the most lethal diseases threatening public health; the lack of drugs with strong antiviral activity against virus strains exacerbates the problem.

METHODS

Two independent researchers searched relevant studies using Embase, PubMed, Web of Science, Google Scholar, and MEDLINE databases from its inception to December 2022.

RESULTS

Based on the different antiviral mechanisms, current antiviral strategies can be mainly classified into virus-targeting approaches such as neuraminidase inhibitors, matrix protein 2 ion channel inhibitors, polymerase acidic protein inhibitors and other host-targeting antivirals. However, highly viral gene mutation has underscored the necessity of novel antiviral drug development. Arbidol (ARB) is a Russian-made indole-derivative small molecule licensed in Russia and China for the prevention and treatment of influenza and other respiratory viral infections. ARB also has inhibitory effects on many other viruses such as severe acute respiratory syndrome coronavirus 2, Coxsackie virus, respiratory syncytial virus, Hantaan virus, herpes simplex virus, and hepatitis B and C viruses. ARB is a promising drug which can not only exert activity against virus at different steps of virus replication cycle, but also directly target on hosts before infection to prevent virus invasion.

CONCLUSION

ARB is a broad-spectrum antiviral drug that inhibits several viruses in vivo and in vitro, with high safety profile and low resistance; the antiviral mechanisms of ARB deserve to be further explored and more high-quality clinical studies are required to establish the efficacy and safety of ARB.

Molecular Evolution of Human Parainfluenza Virus Type 2 Based on Hemagglutinin-Neuraminidase Gene

To understand the molecular evolution of human parainfluenza virus type 2 (HPIV2), 21 Hemagglutinin-Neuraminidase (HN) gene sequences covering seven Chinese provinces in 2011 and 2017 to 2021 were combined with 90 published HN sequences worldwide for phylogenetic analysis. The result showed that global HPIV2 could be classified into two distinct clusters (I and II), five lineages (IA to IIE), and four sublineages (IB1 and 2, and IIE1 and 2). The minimum genetic distances between different clusters and lineages were 0.049 and 0.014, respectively. In the last decade, one lineage (IID) and three sublineages (IB1, IB2, and IIE1) have been cocirculating in China, with the sublineages IB2 and IIE1 dominating, while sublineages IB1 and IIE1 are dominant globally. In addition, the spread of HPIV2 had relative spatial clustering, and sublineage IB2 has only been detected in China thus far. The overall evolution rate of HPIV2 was relatively low, on the order of 10-4 substitutions/site/year, except for sublineage IB2 at 10-3 substitutions/site/year. Furthermore, human-animal transmission was observed, suggesting that the HPIV2 might have jumped out of animal reservoirs in approximately 1922, the predicted time of a common ancestor. The entire HN protein was under purifying/negative selection, and the specific amino acid changes and two novel N-glycosylation sites (N316 and N517) in sublineages IB1, IB2, and IIE1 were mostly located in the globular head region of the HN protein. In this study, preliminary evolutionary characteristics of HPIV2 based on the HN gene were obtained, increasing the recognition of the evolution and adaptation of HPIV2. IMPORTANCE The phylogenetic analysis showed that global HPIV2 could be classified into two distinct clusters (I and II) and five lineages (IA to IIE) with at least 0.049 and 0.014 genetic distances between clusters and lineages, respectively. Furthermore, lineages IB and IIE could be further divided into two sublineages (IB1-2 and IIE1-2). All China sequences belong to one lineage and three sublineages (IB1, IB2, IID, and IIE1), among which sublineages IB2 and IIE1 are predominant and cocirculating in China, while sublineages IB1 and IIE1 are dominant globally. The overall evolution rate of HPIV2 is on the order of 10-4 substitutions/site/year, with the highest rate of 2.18 × 10-3 for sublineage IB2. The entire HN protein is under purifying/negative selection, and the specific amino acid substitutions and two novel N-glycosylation sites (N316 and N517) in sublineages IB1, IB2, and IIE1 are mostly located in the globular head region of the HN protein.

Design, Synthesis, and Antiviral Evaluation of Sialic Acid Derivatives as Inhibitors of Newcastle Disease Virus Hemagglutinin-Neuraminidase: A Translational Study on Human Parainfluenza Viruses

Global infections with viruses belonging to the Paramyxoviridae, such as Newcastle disease virus (NDV) or human parainfluenza viruses (hPIVs), pose a serious threat to animal and human health. NDV-HN and hPIVs-HN (HN hemagglutinin-neuraminidase) share a high degree of similarity in catalytic site structures; therefore, the development of an efficient experimental NDV host model (chicken) may be informative for evaluating the efficacy of hPIVs-HN inhibitors. As part of the broad research in pursuit of this goal and as an extension of our published work on antiviral drug development, we report here the biological results obtained with some newly synthesized C4- and C5-substituted 2,3-unsaturated sialic acid derivatives against NDV. All developed compounds showed high neuraminidase inhibitory activity (IC₅₀ 0.03-13 μM). Four molecules (9, 10, 23, 24) confirmed their high in vitro inhibitory activity, which caused a significant reduction of NDV infection in Vero cells, accompanied by very low toxicity.

Quinones as Promising Compounds against Respiratory Viruses: A Review

Respiratory viruses represent a world public health problem, giving rise to annual seasonal epidemics and several pandemics caused by some of these viruses, including the COVID-19 pandemic caused by the novel SARS-CoV-2, which continues to date. Some antiviral drugs have been licensed for the treatment of influenza, but they cause side effects and lead to resistant viral strains. Likewise, aerosolized ribavirin is the only drug approved for the therapy of infections by the respiratory syncytial virus, but it possesses various limitations. On the other hand, no specific drugs are licensed to treat other viral respiratory diseases. In this sense, natural products and their derivatives have appeared as promising alternatives in searching for new compounds with antiviral activity. Besides their chemical properties, quinones have demonstrated interesting biological activities, including activity against respiratory viruses. This review summarizes the activity against respiratory viruses and their molecular targets by the different types of quinones (both natural and synthetic). Thus, the present work offers a general overview of the importance of quinones as an option for the future pharmacological treatment of viral respiratory infections, subject to additional studies that support their effectiveness and safety.

Co-infection of the respiratory epithelium, scene of complex functional interactions between viral, bacterial, and human neuraminidases

The activity of sialic acids, known to play critical roles in biology and many pathological processes, is finely regulated by a class of enzymes called sialidases, also known as neuraminidases. These are present in mammals and many other biological systems, such as viruses and bacteria. This review focuses on the very particular situation of co-infections of the respiratory epithelium, the scene of complex functional interactions between viral, bacterial, and human neuraminidases. This intrinsically multidisciplinary topic combining structural biology, biochemistry, physiology, and the study of host-pathogen interactions, opens up exciting research perspectives that could lead to a better understanding of the mechanisms underlying virus-bacteria co-infections and their contribution to the aggravation of respiratory pathology, notably in the context of pre-existing pathological contexts. Strategies that mimic or inhibit the activity of the neuraminidases could constitute interesting treatment options for viral and bacterial infections.

Emerging antiviral therapies and drugs for the treatment of influenza

INTRODUCTION

Both vaccines and antiviral drugs represent the mainstay for preventing and treating influenza. However, approved M2 ion channel inhibitors, neuraminidase inhibitors, polymerase inhibitors, and various vaccines cannot meet therapeutic needs because of viral resistance. Thus, the discovery of new targets for the virus or host and the development of more effective inhibitors are essential to protect humans from the influenza virus.

AREAS COVERED

This review summarizes the latest progress in vaccines and antiviral drug research to prevent and treat influenza, providing the foothold for developing novel antiviral inhibitors.

EXPERT OPINION

Vaccines embody the most effective approach to preventing influenza virus infection, and recombinant protein vaccines show promising prospects in developing next-generation vaccines. Compounds targeting the viral components of RNA polymerase, hemagglutinin and nucleoprotein, and the modification of trusted neuraminidase inhibitors are future research directions for anti-influenza virus drugs. In addition, some host factors affect the replication of virus in vivo, which can be used to develop antiviral drugs.

Antiviral strategies against human metapneumovirus: Targeting the fusion protein

Human metapneumoviruses have emerged in the past decades as an important global pathogen that causes severe upper and lower respiratory tract infections. Children under the age of 2, the elderly and immunocompromised individuals are more susceptible to HMPV infection than the general population due to their suboptimal immune system. Despite the recent discovery of HMPV as a novel important respiratory virus, reports have rapidly described its epidemiology, biology, and pathogenesis. However, progress is still to be made in the development of vaccines and drugs against HMPV infection as none are currently available. Herein, we discuss the importance of HMPV and review the reported strategies for anti-HMPV drug candidates. We also present the fusion protein as a promising antiviral drug target due to its multiple roles in the HMPV lifecycle. This key viral protein has previously been targeted by a range of inhibitors, which will be discussed as they represent opportunities for future drug design.

Favipiravir in the Battle with Respiratory Viruses

Abstract:

Among antiviral drugs, the vast majority targets only one or two related viruses. The conventional model, one virus - one drug, significantly limits therapeutic options. Therefore, in the strategy of controlling viral infections, there is a necessity to develop compounds with pleiotropic effects. Favipiravir (FPV) emerged as a strong candidate to become such a drug. The aim of the study is to present up-to-date information on the role of favipiravir in the treatment of viral respiratory infections. The anti-influenza activity of favipiravir has been confirmed in cell culture experiments, animal models and clinical trials. Thoroughly different - from the previously registered drugs - mechanism of action suggests that FVP can be used as a countermeasure for the novel or re-emerging influenza virus infections. In recent months, favipiravir has been broadly investigated due to its potential efficacy in the treatment of Covid-19. Based on preclinical and clinical studies and a recently published meta-analysis it seems that favipiravir may be a promising antiviral drug in the treatment of patients with Covid-19. FPV is also effective against other RNA respiratory viruses and may be a candidate for the treatment of serious infections caused by human rhinovirus, respiratory syncytial virus, metapneumovirus, parainfluenza viruses and hantavirus pulmonary syndrome.

Parainfluenza virus entry at the onset of infection

Parainfluenza viruses, members of the enveloped, negative-sense, single stranded RNA Paramyxoviridae family, impact global child health as the cause of significant lower respiratory tract infections. Parainfluenza viruses enter cells by fusing directly at the cell surface membrane. How this fusion occurs via the coordinated efforts of the two molecules that comprise the viral surface fusion complex, and how these efforts may be blocked, are the subjects of this chapter. The receptor binding protein of parainfluenza forms a complex with the fusion protein of the virus, remaining stably associated until a receptor is reached. At that point, the receptor binding protein actively triggers the fusion protein to undergo a series of transitions that ultimately lead to membrane fusion and viral entry. In recent years it has become possible to examine this remarkable process on the surface of viral particles and to begin to understand the steps in the transition of this molecular machine, using a structural biology approach. Understanding the steps in entry leads to several possible strategies to prevent fusion and inhibit infection.

Roles of conserved residues in the receptor binding sites of human parainfluenza virus type 3 HN protein

Human parainfluenza virus type 3 (hPIV-3) entry and intrahost spread through membrane fusion are initiated by two envelope glycoproteins, hemagglutinin-neuraminidase (HN) and fusion (F) protein. Binding of HN protein to the cellular receptor via its receptor-binding sites triggers conformational changes in the F protein leading to virus-cell fusion. However, little is known about the roles of individual amino acids that comprise the receptor-binding sites in the fusion process. Here, residues R192, D216, E409, R424, R502, Y530 and E549 located within the receptor-binding site Ⅰ, and residues N551 and H552 at the putative site Ⅱ were replaced by alanine with site-directed mutagenesis. All mutants except N551A displayed statistically lower hemadsorption activities ranging from 16.4% to 80.2% of the wild-type (wt) level. With standardization of the number of bound erythrocytes, similarly, other than N551A, all mutants showed reduced fusogenic activity at three successive stages: lipid mixing (hemifusion), content mixing (full fusion) and syncytium development. Kinetic measurements of the hemifusion process showed that the initial hemifusion extent for R192A, D216A, E409A, R424A, R502A, Y530A, E549A and H552A was decreased to 69.9%, 80.6%, 71.3%, 67.3%, 50.6%, 87.4%, 84.9% and 25.1%, respectively, relative to the wt, while the initial rate of hemifusion for the E409A, R424A, R502A and H552A mutants was reduced to 69.0%, 35.4%, 62.3%, 37.0%, respectively. In addition, four mutants with reduced initial hemifusion rates also showed decreased percentages of F protein cleavage from 43.4% to 56.3% of the wt. Taken together, Mutants R192A, D216A, E409A, R424A, R502A, Y530A, E549A and H552A may lead to damage on the fusion activity at initial stage of hemifusion, of which decreased extent and rate may be associated with impaired receptor binding activity resulting in the increased activation barrier of F protein and the cleavage of it, respectively.

Viruses Like Sugars: How to Assess Glycan Involvement in Viral Attachment

The first step of viral infection requires interaction with the host cell. Before finding the specific receptor that triggers entry, the majority of viruses interact with the glycocalyx. Identifying the carbohydrates that are specifically recognized by different viruses is important both for assessing the cellular tropism and for identifying new antiviral targets. Advances in the tools available for studying glycan-protein interactions have made it possible to identify them more rapidly; however, it is important to recognize the limitations of these methods in order to draw relevant conclusions. Here, we review different techniques: genetic screening, glycan arrays, enzymatic and pharmacological approaches, and surface plasmon resonance. We then detail the glycan interactions of enterovirus D68 and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlighting the aspects that need further clarification.

Seaweed Sulfated Polysaccharides against Respiratory Viral Infections

Respiratory viral infections have been a leading cause of morbidity and mortality worldwide. Despite massive advancements in the virology field, no specific treatment exists for most respiratory viral infections. Approved therapies against respiratory viruses rely almost exclusively on synthetic drugs that have potential side effects, restricting their use. This review aims to present natural marine sulfated polysaccharides possessing promising antiviral activity against respiratory viruses that could be a safe alternative to synthetic broad-spectrum antiviral drugs. The antiviral properties of marine sulfated polysaccharides are presented according to their mechanism of action on different types and strains of respiratory viruses, and the potential limits of their use are discussed.

Clinical features of parainfluenza infections among young children hospitalized for acute respiratory illness in Amman, Jordan

Background

Parainfluenza virus (PIV) is a leading cause of acute respiratory illness (ARI) in children. However, few studies have characterized the clinical features and outcomes associated with PIV infections among young children in the Middle East.

Methods

We conducted hospital-based surveillance for ARI among children < 2 years of age in a large referral hospital in Amman, Jordan. We systematically collected clinical data and respiratory specimens for pathogen detection using reverse transcription polymerase chain reaction. We compared clinical features of PIV-associated ARI among individual serotypes 1, 2, 3, and 4 and among PIV infections compared with other viral ARI and ARI with no virus detected. We also compared the odds of supplemental oxygen use using logistic regression.

Results

PIV was detected in 221/3168 (7.0%) children hospitalized with ARI. PIV-3 was the most commonly detected serotype (125/221; 57%). Individual clinical features of PIV infections varied little by individual serotype, although admission diagnosis of ‘croup’ was only associated with PIV-1 and PIV-2. Children with PIV-associated ARI had lower frequency of cough (71% vs 83%; p < 0.001) and wheezing (53% vs 60% p < 0.001) than children with ARI associated with other viruses. We did not find a significant difference in supplemental oxygen use between children with PIV-associated infections (adjusted odds ratio [aOR] 1.12, 95% CI 0.66–1.89, p = 0.68) and infections in which no virus was detected.

Conclusions

PIV is frequently associated with ARI requiring hospitalization in young Jordanian children. Substantial overlap in clinical features may preclude distinguishing PIV infections from other viral infections at presentation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06001-1.

Recent progress in chemical approaches for the development of novel neuraminidase inhibitors

Influenza virus is the main cause of an infectious disease called influenza affecting the respiratory system including the throat, nose and lungs. Neuraminidase inhibitors are reagents used to block the enzyme called neuraminidase to prevent the influenza infection from spreading. Neuraminidase inhibitors are widely used in the treatment of influenza infection, but still there is a need to develop more potent agents for the more effective treatment of influenza. Complications of the influenza disease lead to death, and one of these complications is drug resistance; hence, there is an urgent need to develop more effective agents. This review focuses on the recent advances in chemical synthesis pathways used for the development of new neuraminidase agents along with the medicinal aspects of chemically modified molecules, including the structure-activity relationship, which provides further rational designs of more active small molecules.

Parainfluenza Virus Infection in an Australian Community-based Birth Cohort

In a community-based birth cohort of 158 Australian infants followed to age 2 years, the incidence rate of human parainfluenza virus (HPIV) was 0.42 (95% CI = 0.33, 0.54) episodes per child-year with episodes occurring year-round, peaking in the spring season. HPIV-3 was the dominant subtype. Overall, 41% of detections were asymptomatic; only 32% of HPIV episodes led to healthcare contact with 1 hospitalization.

Human parainfluenza virus circulation, United States, 2011-2019

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Human parainfluenza virus type 3 is the most commonly reported parainfluenza virus followed by types 1, 2, and 4, respectively.

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Each parainfluenza virus type exhibited a unique circulation pattern.

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Parainfluenza type 4 circulated annually and peaked during the winter months.

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There was no remarkable distinction in regional versus national seasonal circulation patterns.

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The majority of parainfluenza virus detections with available age data occurred among children aged ≤2 years.

Background

Human parainfluenza viruses (HPIVs) cause upper and lower respiratory tract illnesses, most frequently among infants and young children, but also in the elderly. While seasonal patterns of HPIV types 1–3 have been described, less is known about national patterns of HPIV-4 circulation.

Objectives

To describe patterns of HPIVs circulation in the United States (US).

Study design

We used data from the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary passive laboratory-based surveillance system, to characterize the epidemiology and circulation patterns of HPIVs in the US during 2011–2019. We summarized the number of weekly aggregated HPIV detections nationally and by US census region, and used a subset of data submitted to NREVSS from public health laboratories and several clinical laboratories during 2015–2019 to analyze differences in patient demographics.

Results

During July 2011 - June 2019, 2,700,135 HPIV tests were reported; 122,852 (5 %) were positive for any HPIV including 22,446 for HPIV-1 (18 %), 17,474 for HPIV-2 (14 %), 67,649 for HPIV-3 (55 %), and 15,283 for HPIV-4 (13 %). HPIV testing increased substantially each year. The majority of detections occurred in children aged ≤ 2 years (36 %) with fluctuations in the distribution of age by type.

Conclusions

HPIVs were detected year-round during 2011–2019, with type-specific year-to-year variations in circulation patterns. Among HPIV detections where age was known, the majority were aged ≤ 2 years. HPIV-4 exhibited an annual fall-winter seasonality, both nationally and regionally. Continued surveillance is needed to better understand national patterns of HPIV circulation.