Human metapneumovirus (hMPV) is a significant respiratory pathogen, primarily impacting young, elderly, and immunocompromised populations. While the clinical presentations are similar to those of other respiratory viruses such as respiratory syncytial virus (RSV), influenza, and SARS-CoV-2, they can still lead to serious complications. The virus primarily transmits via respiratory droplets, with outbreaks peaking during winter and spring. In resource-limited settings, administration of multiplex PCR assays is essential for precise diagnosis, yet it presents significant challenges. Recent studies indicate a 6.24% infection rate in hospitalized patients presenting with acute respiratory infections (ARIs). Enhanced surveillance and prevention are essential given the morbidity and mortality rates of hMPV, which are comparable to those of influenza and RSV. Effective management requires enhanced diagnostic tools, improved public health strategies, and continuous research into antiviral therapies and vaccines. This study highlighted the growing importance of hMPV as a respiratory pathogen, focusing on its seasonal patterns, clinical manifestations in at-risk populations, transmission dynamics, and diagnostic challenges compared to other respiratory viruses.

Avian metapneumovirus (aMPV) infection is an important respiratory disease that causes significant economic loss in the poultry industry. Here, we aimed to develop an effective live aMPV subtype B vaccine strain suitable for mass vaccination of poultry farms to achieve herd immunity. The wild-type virus was attenuated by serial passaging in Vero-K cells, and the genetic stability of the attenuated virus was evaluated through genomic sequencing analysis. The attenuated virus was formulated into test pilot live vaccines. Preclinical tests of the test vaccine, including those measuring indices of safety, minimum immunogenicity, virulence reversion, immunogenicity and cross-protective efficacy, were conducted in SPF chickens. The master seed virus (MSV) of the SNU21004(a) vaccine strain was established by serial passaging in Vero-K cells. Some point mutations occurred throughout the viral genome, but no gene deletions or insertions were observed. The clinical scores, histopathological scores, and viral loads of SPF chickens inoculated with the MSV were significantly lower than those inoculated with the wild-type virus (P < 0.05). There was no increase in viral virulence after five backpassages in chickens. The minimal immunogenicity dose for protection against aMPV is 102.1 TCID50/dose. The test vaccine induced a strong humoral immune response and efficiently protected chickens, even in vaccinated birds with low antibody titers, regardless of the route of administration (drinking water or spraying) or challenge virus subtype (subtypes A and B). The SNU21004(a) vaccine strain was found to be safe and highly immunogenic even at small doses in chickens and showed cross-protection against other aMPV infections.

In May 2023, the United States Food and Drug Administration approved a Pfizer©-sponsored (Pfizer, New York, NY, USA) bivalent respiratory syncytial virus prefusion F protein-based vaccine (RSVpreF) RSV vaccine (AbrysvoTM [Pfizer]) for use during pregnancy to prevent neonatal/infant RSV infection. In February of 2022, trials sponsored by GSK© (Brentford, England, UK) on a similar RSVpreF vaccine were halted because of the identification of a safety signal related to preterm births. As these vaccines use identical pre-fusion F-protein technology, we sought to synthesize the existing data on their effectiveness and safety. We identified all randomized controlled trials and used RevMan 5.4.1 (The Cochrane Collaboration, England, UK) to perform the analysis with 95% confidence intervals and risk ratios (RRs). We found many maternal side effects were more prevalent in the RSVpreF group, with more local reactions, blood disorders, fatigue, joint pain, cardiac disorders, headache, fever, gastrointestinal disorders and pregnancy complications. The vaccinated group demonstrated significant reductions in RSV-lower respiratory tract cases (RR, 0.44 [0.33, 0.57]; P<0.00001), severe respiratory illness (RR, 0.29 [0.19, 0.44]; P<0.00001), and hospitalizations (RR, 0.40 [0.24, 0.67]; P=0.0005). RSVpreF vaccination was associated with a higher incidence of preterm delivery (RR, 1.24 [1.08, 1.44]; P=0.003). No significant difference in neonatal deaths was observed (RR, 1.42 [0.70, 2.89]; P=0.34). In conclusion, RSVpreF vaccination results in systemic adverse events and an increase in preterm delivery. Vaccination appears to have acceptable short-term newborn safety, but is not related to a significant decrease in neonatal death.

Respiratory viruses are increasingly detected in children with community-acquired pneumonia. Further strategies to limit antibiotic use in children with viral pneumonia are warranted.

To explore clinical efficacy of budesonide/formoterol inhalation powder for viral pneumonia in children and its impact on cellular immunity and inflammatory factor production.

A total of 60 children with viral pneumonia were recruited: 30 receiving budesonide/formoterol inhalation powder and 30 conventional symptomatic treatment. Outcome measures included peripheral blood levels of inflammatory cytokines, CD4+, CD8+, Th1, Th2, Th17 and Treg, clinical efficacy, and incidence of adverse reactions.

Compared with the control group, the observation group showed a significant reduction in interleukin-6 and high-sensitivity C-reactive protein levels after treatment. Compared with the control group, the observation group showed a significant increase in CD4+/CD8+ and Th1/Th2 levels, and a decrease in Th17/Treg levels after treatment. The total effective rates in the observation group and the control group were 93.75% and 85.00%, respectively, which was a significant difference (P = 0.003).

Budesonide/formoterol inhalation powder significantly improved therapeutic efficacy for viral pneumonia in children. The mechanism of action may be related to downregulation of the inflammatory response and improved cellular immune function.

Eosinophils are a critical type of immune cell and central players in type 2 immunity. Existing literature suggests that eosinophils also can play a role in host antiviral responses, typically type 1 immune events, against multiple respiratory viruses, both directly through release of antiviral mediators and indirectly through activation of other effector cell types. One way to prime host immune responses toward effective antiviral responses is through vaccination, where typically a type 1-skewed immunity is desirable in the context of intracellular pathogens like respiratory viruses. In the realm of breakthrough respiratory viral infection in vaccinated hosts, an event in which virus can still establish productive infection despite preexisting immunity, eosinophils are most prominently known for their link to vaccine-associated enhanced respiratory disease upon natural respiratory syncytial virus infection. This was observed in a pediatric cohort during the 1960s following vaccination with formalin-inactivated respiratory syncytial virus. More recent research has unveiled additional roles of the eosinophil in respiratory viral infection and breakthrough infection. The specific contribution of eosinophils to the quality of vaccine responses, vaccine efficacy, and antiviral responses to infection in vaccinated hosts remains largely unexplored, especially regarding their potential roles in protection. On the basis of current findings, we will speculate upon the suggested function of eosinophils and consider the many potential ways by which eosinophils may exert protective and pathological effects in breakthrough infections. We will also discuss how to balance vaccine efficacy with eosinophil-related risks, as well as the use of eosinophils and their products as potential biomarkers of vaccine efficacy or adverse events.

Efficient control of influenza A infection can potentially be achieved through the development of broad-spectrum vaccines. Recombinant proteins incorporating conserved influenza A virus peptides are one of the platforms for the development of cross-protective influenza vaccines. We constructed a recombinant protein Flg-HA2-2-4M2ehs, in which the extracellular domain of the M2 protein (M2e) and the sequence (aa76-130) of the second subunit of HA (HA2) were used as target antigens. In this study, we investigated the ability of the Flg-HA2-2-4M2ehs protein to activate innate immunity and stimulate the formation of T-cell response in mice of different genetic lines after intranasal immunization. Our studies showed that the Flg-HA2-2-4M2ehs protein was manifested in an increase in the relative content of neutrophils, monocytes, and interstitial macrophages, against the backdrop of a decrease in the level of dendritic cells and increased expression in the CD86 marker. In the lungs of BALB/c mice, immunization with the Flg-HA2-2-4M2ehs protein induced the formation of antigen-specific CD4+ and CD8+ effector memory T cells, producing TNF-α. In mice C57Bl/6, the formation of antigen-specific effector CD8+ T cells, predominantly producing IFN-γ+, was demonstrated. The data obtained showed the formation of CD8+ and CD4+ effector memory T cells expressing the CD107a.

In December 2019, an unknown viral infection emerged and quickly spread worldwide, resulting in a global pandemic. This novel virus caused severe pneumonia and acute respiratory distress syndrome caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). It has caused 6.25 millions of deaths worldwide and remains a major concern for health, society, and the economy. As vaccination is one of the most efficient ways to combat this pandemic, different vaccines were developed in a short period. This review article discusses how coronavirus affected the top nations of the world and the vaccines being used for the prevention. Amongst the vaccines, some vaccines have already been approved, and some have been involved in clinical studies. The article also provides insight into different COVID-19 vaccine platforms, their preparation, working, efficacy, and side effects.

Recent progress in genomics and bioinformatics technologies have allowed for the emergence of immunogenomics field. This intersection of immunology and genetics has broadened our understanding of how the immune system responds to infection and vaccination. While the immunogenetic basis of the huge clinical variability in response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is currently being extensively studied, the host genetic determinants of SARS-CoV-2 vaccines remain largely unknown. Previous reports evidenced that vaccines may not protect all populations or individuals equally, due to multiple host- and vaccine-specific factors. Several studies on vaccine response to measles, rubella, hepatitis B, smallpox, and influenza highlighted the contribution of genetic mutations or polymorphisms in modulating the innate and adaptive immunity following vaccination. Specifically, genetic variants in genes encoding virus receptors, antigen presentation, cytokine production, or related to immune cells activation and differentiation could influence how an individual responds to vaccination. Although such knowledge could be utilized to generate personalized vaccine strategies to optimize the vaccine response, studies in this filed are still scarce. Here, we briefly summarize the scientific literature related to the immunogenetic determinants of vaccine-induced immunity, highlighting the possible role of host genetics in response to SARS-CoV-2 vaccines as well.

Future infectious disease outbreaks are inevitable; therefore, it is critical that we maximize our readiness for these events by preparing effective public health policies and healthcare innovations. Although we do not know the nature of future pathogens, antigen-agnostic platforms have the potential to be broadly useful in the rapid response to an emerging infection-particularly in the case of vaccines. During the current COVID-19 pandemic, recent advances in mRNA engineering have proven paramount in the rapid design and production of effective vaccines. Comparatively, however, the development of new adjuvants capable of enhancing vaccine efficacy has been lagging. Despite massive improvements in our understanding of immunology, fewer than ten adjuvants have been approved for human use in the century since the discovery of the first adjuvant. Modern adjuvants can improve vaccines against future pathogens by reducing cost, improving antigen immunogenicity, and increasing antigen stability. In this perspective, we survey the current state of adjuvant use, highlight potentially impactful preclinical adjuvants, and propose new measures to accelerate adjuvant safety testing and technology sharing to enable the use of "off-the-shelf" adjuvant platforms for rapid vaccine testing and deployment in the face of future pandemics.

Longitudinal studies are needed to evaluate the SARS-CoV-2 mRNA vaccine antibody response under real-world conditions. This longitudinal study investigated the quantity and quality of SARS-CoV-2 antibody response in 846 specimens from 350 patients, comparing BNT162b2-vaccinated individuals (19 previously diagnosed with COVID-19, termed RecoVax; and 49 never diagnosed, termed NaiveVax) with 122 hospitalized unvaccinated (HospNoVax) and 160 outpatient unvaccinated (OutPtNoVax) COVID-19 patients. NaiveVax experienced delay in generating SARS-CoV-2 total antibodies (TAb) and surrogate neutralizing antibodies (SNAb) after the first vaccine dose (D1) but rapid increase in antibody levels after the second dose (D2). However, these never reached RecoVax's robust levels. In fact, NaiveVax TAb and SNAb levels decreased 4 weeks after D2. For the most part, RecoVax TAb persisted, after reaching maximal levels 2 weeks after D2, but SNAb decreased significantly about 6 months after D1. Although NaiveVax avidity lagged behind that of RecoVax for most of the follow-up periods, NaiveVax did reach similar avidity by about 6 months after D1. These data suggest that 1 vaccine dose elicits maximal antibody response in RecoVax and may be sufficient. Also, despite decreasing levels in TAb and SNAb over time, long-term avidity may be a measure worth evaluating and possibly correlating to vaccine efficacy.

SARS-CoV-2 vaccination has been launched worldwide to build effective population-level immunity to curb the spread of this virus. The effectiveness and duration of protective immunity is a critical factor for public health. Here, we report the kinetics of the SARS-CoV-2 specific immune response in 204 individuals up to 1-year after recovery from COVID-19. RBD-IgG and full-length spike-IgG concentrations and serum neutralizing capacity decreases during the first 6-months, but is maintained stably up to 1-year after hospital discharge. Even individuals who had generated high IgG levels during early convalescent stages had IgG levels that had decreased to a similar level one year later. Notably, the RBD-IgG level positively correlates with serum neutralizing capacity, suggesting the representative role of RBD-IgG in predicting serum protection. Moreover, viral-specific cellular immune protection, including spike and nucleoprotein specific, persisted between 6 months and 12 months. Altogether, our study supports the persistence of viral-specific protective immunity over 1 year.

The unprecedented impact of the coronavirus disease 2019 (COVID-19) pandemic has resulted in global challenges to our health-care systems and our economic security. As such, there has been significant research into all aspects of the disease, including diagnostic biomarkers, associated risk factors, and strategies that might be used for its treatment and prevention. Toward this end, eosinopenia has been identified as one of many factors that might facilitate the diagnosis and prognosis of severe COVID-19. However, this finding is neither definitive nor pathognomonic for COVID-19. While eosinophil-associated conditions have been misdiagnosed as COVID-19 and others are among its reported complications, patients with pre-existing eosinophil-associated disorders (e.g., asthma, eosinophilic gastrointestinal disorders) do not appear to be at increased risk for severe disease; interestingly, several recent studies suggest that a diagnosis of asthma may be associated with some degree of protection. Finally, although vaccine-associated aberrant inflammatory responses, including eosinophil accumulation in the respiratory tract, were observed in preclinical immunization studies targeting the related SARS-CoV and MERS-CoV pathogens, no similar complications have been reported clinically in response to the widespread dissemination of either of the two encapsulated mRNA-based vaccines for COVID-19.