Outlining recent updates on influenza therapeutics and vaccines: A comprehensive review

Influenza virus has presented a considerable healthcare challenge during the past years, particularly in vulnerable groups with compromised immune systems. Therapeutics and vaccination have always been in research annals since the spread of influenza. Efforts have been going on to develop an antiviral therapeutic approach that could assist in better disease management and reduce the overall disease complexity, resistance development, and fatality rates. On the other hand, vaccination presents a chance for effective, long-term, cost-benefit, and preventive response against the morbidity and mortality associated with the influenza. However, the issues of resistance development, strain mutation, antigenic variability, and inability to cure wide-spectrum and large-scale strains of the virus by available vaccines remain there. The article gathers the updated data for the therapeutics and available influenza vaccines, their mechanism of action, shortcomings, and trials under clinical experimentation. A methodological approach has been adopted to identify the prospective therapeutics and available vaccines approved and within the clinical trials against the influenza virus. Review contains influenza therapeutics, including traditional and novel antiviral drugs and inhibitor therapies against influenza virus as well as research trials based on newer drug combinations and latest technologies such as nanotechnology and organic and plant-based natural products. Most recent development of influenza vaccine has been discussed including some updates on traditional vaccination protocols and discussion on next-generation and upgraded novel technologies. This review will help the readers to understand the righteous approach for dealing with influenza virus infection and for deducing futuristic approaches for novel therapeutic and vaccine trials against Influenza.

Characterization of novel, severely immunodeficient PrkdcΔex57/Δex57 mice

Severely immunodeficient mice are useful for understanding the pathogenesis of certain tumors and for developing therapeutic agents for such tumors. In addition, engraftment of these mice with human hematopoietic cells can yield information that helps us understand the in vivo molecular mechanisms underlying actual human viral infections. In our present research, we discovered a novel, severely immunodeficient strain of mice having a mutation in exon 57 of the Prkdc gene (PrkdcΔex57/Δex57) in an inbred colony of B10.S/SgSlc mice. Those PrkdcΔex57/Δex57 mice showed thymic hypoplasia and lack of mature T cells and B cells in peripheral lymphoid tissues, resulting in very low levels of production of serum immunoglobulins. In addition, those mice were highly susceptible to influenza viruses due to the lack of acquired immune cells. On the other hand, since they had sufficient numbers of NK cells, they rejected tumor transplants, similarly to Prkdc+/+ mice. Next, we generated Foxn1nu/nuPrkdcΔex57/Δex57Il2rg-/- (NPG) mice on the BALB/cSlc background, which lack all lymphocytes such as T cells, B cells and innate lymphoid cells, including NK cells. As expected, these mice were able to undergo engraftment of human tumor cell lines. These findings suggest that PrkdcΔex57/Δex57 mice will be useful as a novel model of immunodeficiency, while NPG mice will be useful for xenografting of various malignancies.

Association of influenza vaccination or influenza virus infection history with subsequent infection risk among children: The Japan Environment and Children's Study (JECS)

We measured the association between history of influenza vaccination by age 2 years and influenza virus (IFV) infection at ages 3 and 4 years by relative risk reduction. We also examined the association between history of IFV infection by age 2 years and recurrent IFV infection at age 3 years. This study included 73,666 children from a large Japanese birth cohort. Among children vaccinated never, once or twice when aged under 2 years, 16.0%, 10.8% and 11.3%, respectively, had been infected with IFV by age 3 years, and 19.2%, 14.5% and 16.0%, respectively, by age 4 years. Compared with no history of influenza vaccination, vaccination at ages 1 and/or 2 years reduced the risk of IFV infection at age 3 by 30%-32% and at age 4 by 17%-24%. The relative risk of recurrent IFV infection at ages 3 and 4 years increased in proportion to the number of prior infections by age 2. One-season-prior influenza vaccination history reduced the IFV infection risk at age 3 years by 25%-42%. Influenza vaccination most effectively protected children at age 3 who lacked older sibling(s) and did not attend nursery school. One-season-prior IFV infection increased the relative risk of recurrent infection at age 3 years (1.72-3.33). In conclusion, influenza vaccination-induced protection may partly extend to the next season. Owing to the relative risk reduction by influenza vaccination and the increased relative risk of IFV infection from prior-season infection, annual influenza vaccination is recommended.

Chronic allergic asthma induces T-cell exhaustion and impairs virus clearance in mice

BACKGROUND

Allergic asthma, one of the most common types of asthma, is thought to be highly susceptible to respiratory viral infections; however, its pathological mechanism needs to be elucidated. Recent studies have found impaired T-cell function in asthmatic mice. Therefore, we aimed to investigate the way by which asthma induction affects T-cell exhaustion in the lungs and assess the relationship between T-cell exhaustion and influenza viral infection.

METHODS

Chronic allergic asthma mice were induced by intranasal injection of ovalbumin for 6 weeks and asthmatic features and T cell populations in lung or airway were assessed. To determine the influenza virus susceptibility, control and asthma mice were challenged with the human influenza virus strain A/Puerto Rico/8/1934 H1N1 and evaluated the survival rate, lung damage, and virus titer.

RESULTS

Six weeks of OVA sensitization and challenge successfully induced chronic allergic asthma in a mouse model showing significant increase of sera IgE level and broncho-pathological features. A significant decrease in interferon-γ-producing T-cell populations and an increase in exhausted T-cell populations in the lungs of OVA-induced asthmatic mice were observed. Asthmatic mice were more susceptible to influenza virus infection than control mice showing lower survival rate and higher virus titer in lung, and a positive correlation existed between T-cell exhaustion in the lung and virus titer.

CONCLUSIONS

Asthma induction in mice results in the exhaustion of T-cell immunity, which may contribute to the defective capacity of viral protection. This study demonstrates a correlation between asthma conditions and viral susceptibility by investigating the functional characteristics of T-cells in asthma. Our results provide insights into the development of strategies to overcome the dangers of respiratory viral disease in patients with asthma.

Mild and asymptomatic influenza B virus infection among unvaccinated pregnant persons: Implication for effectiveness of non-pharmaceutical intervention and vaccination to prevent influenza

BACKGROUND

We estimated symptomatic and asymptomatic influenza infection frequency in community-dwelling unvaccinated pregnant persons to inform risk communication.

METHODS

We collected residue sera from multiple antenatal-care blood draws during October 2016-April 2017. We determined influenza infection as seroconversion with ≥ 4-fold rise in antibody titers between any two serum samples by improved hemagglutinin-inhibition assay including ether-treated B antigens. The serology data were linked to the results of nuclei acid testing (rRT-PCR) based on acute respiratory illness (ARI) surveillance.

RESULTS

Among all participants, 43 %(602/1384) demonstrated serology and/or rRT-PCR evidenced infection, and 44 %(265/602) of all infections were asymptomatic. ARI-associated rRT-PCR testing identified only 10 %(61/602) of total infections. Only 1 %(5/420) of the B Victoria cases reported ARI and had a rRT-PCR positive result, compared with 33 %(54/165) of the H3N2 cases. Among influenza ARI cases with multiple serum samples, 19 %(11/58) had seroconversion to a different subtype prior to the illness.

CONCLUSIONS

The incidence of influenza B infection in unvaccinated pregnant persons is under-estimated substantially. Non-pharmaceutical intervention may have suboptimal effectiveness in preventing influenza B transmission due to the less clinical manifestation compared to influenza A. The findings support maternal influenza vaccination to protect pregnant persons and reduce consequent household transmission.

Aging and respiratory viral infection: from acute morbidity to chronic sequelae

The altered immune response in aged hosts play a vital role in contributing to their increased morbidity and mortality during respiratory virus infections. The aged hosts display impaired antiviral immune response as well as increased risk for long-term pulmonary sequelae post virus clearance. However, the underlying cellular and molecular mechanisms driving these alterations of the immune compartment have not been fully elucidated. During the era of COVID-19 pandemic, a better understanding of such aspects is urgently needed to provide insight that will benefit the geriatric patient care in prevention as well as treatment. Here, we review the current knowledge about the unique immune characteristics of aged hosts during homeostasis and respiratory virus infections.

Prolonged exposure to high humidity and high temperature environment can aggravate influenza virus infection through intestinal flora and Nod/RIP2/NF-κB signaling pathway

Seasonal influenza is an acute viral infection caused by influenza virus, which is often prevalent in the summer and winter. The influenza virus can infect pigs and poultry. Some literature reports that the influenza virus has an outbreak in summer. The summer climate is characterized by a high humidity and high temperature environment, which is the same as many animal feeding and growing environments. We established a flu animal model under a high temperature and humidity environment during the day to observe the impact of high humidity and high temperature environment on the mice after contracting the influenza virus. Our results indicate that the intestinal flora of 16 s rDNA cultured in High humidity and high temperature environment changes, the intestinal mucosal permeability increases, the expression of pIgR, sIgA, and IgA in the intestinal mucosal immune system decreases, and the NLR immune recognition signaling pathway NOD1 is activated. The expression of related genes such as NOD2, NF-κB, and pIgR increases, which leads to the increase of related inflammatory factors in the vicinity of the intestines, aggravating local inflammation. High humidity and high temperature environment can cause the expression of inflammatory cytokines in the body to rise, causing Th17/Treg immune imbalance, inhibiting Treg maturation and differentiation, and increasing the expression of IL-2, IL-6, and other cytokines, while the expression of IFN-γ and IL-17A decreases. This condition worsens after infection with the influenza virus. Overall, our study found that High humidity and high temperature environment affect the intestinal flora and the body's immune status, thereby aggravating the status of influenza virus infection.

Efficacy of clarithromycin-naproxen-oseltamivir combination therapy versus oseltamivir alone in hospitalized pediatric influenza patients

PURPOSE

This study aimed to compare the safety and efficacy of clarithromycin-naproxen-oseltamivir combination therapy to that of oseltamivir therapy alone in hospitalized pediatric influenza patients.

METHODS

This prospective, single-blind study included children aged 1-18 years hospitalized with influenza, in MacKay Children's Hospital, Taiwan, between December 2017 and December 2019. The primary outcomes were the time to defervescence and decrease of the Pediatric Respiratory Severity Score (PRESS) during hospitalization. The secondary outcomes were serial changes in virus titers, measured using real-time polymerase chain reaction.

RESULTS

Fifty-four patients were enrolled (28 in the control group and 26 in the combination group) in total. There were no differences in the patients' baseline characteristics between the groups. The time to defervescence was significantly shorter in the combination group than the oseltamivir group (13.2 h vs. 32.1 h, p = 0.002). The decrease in the virus titer from days 1-3 (log Δ13) was more pronounced in the combination group than the oseltamivir group. (39% vs. 19%, p = 0.001). There were no differences in adverse effects such as vomiting, diarrhea, and abdominal pain during the study or within 30 days after antiviral therapy.

CONCLUSION

The clarithromycin-naproxen-oseltamivir combination group experienced a more rapid defervescence and a more rapid decline of influenza virus titer than the group treated with oseltamivir alone. Further consideration should be given to whether the overall benefits of combination therapy in hospitalized pediatric influenza patients outweigh the risks.

Pneumococcal conjugate vaccine modulates macrophage-mediated innate immunity in pneumonia caused by Streptococcus pneumoniae following influenza

Pneumococcal conjugate vaccination (PCV) may prevent influenza-related pneumonia, including Streptococcus pneumoniae pneumonia. To investigate PCV efficacy against secondary pneumococcal pneumonia following influenza, PCV was administered intramuscularly 2 and 5 weeks before S. pneumoniae serotype-3 colonization of murine nasopharynges followed by intranasal challenge with a sublethal dose of influenza A virus. Bacterial and viral loads, including innate immune responses were compared across conditions. PCV vaccination improved the survival of mice with secondary pneumococcal pneumonia and significantly reduced the pulmonary bacterial burden. Increased monocyte/macrophage influx into the lungs, alleviated loss of alveolar macrophages and decreased neutrophil influx into the lungs occurred in PCV-treated mice irrespective of pneumococcal colonization. Higher monocyte chemoattractant protein 1 levels and lower levels of CXCL1, interferon-γ, interleukin-17A, and IL-10, were detected in PCV-treated mice. Additionally, PCV treatment activated the macrophage intracellular killing of S. pneumoniae. Collectively, PCV potentially modulates the host's innate immunity and specific antibodies induction. Macrophage-related innate immunity should be further explored to elucidate the efficacy and mechanisms of PCV versus influenza-related life-threatening diseases.

High performance of rapid influenza diagnostic test and variable effectiveness of influenza vaccines in Mexico

OBJECTIVES

To evaluate the performance of rapid influenza diagnostic tests (RIDT) and influenza vaccines' effectiveness (VE) during an outbreak setting.

METHODS

We compared the performance of a RIDT with RT-PCR for influenza virus detection in influenza-like illness (ILI) patients enrolled during the 2016/17 season in Mexico City. Using the test-negative design, we estimated influenza VE in all participants and stratified by age, virus subtype, and vaccine type (trivalent vs quadrivalent inactivated vaccines). The protective value of some clinical variables was evaluated by regression analyses.

RESULTS

We enrolled 592 patients. RT-PCR detected 93 cases of influenza A(H1N1)pdm09, 55 of AH3N2, 141 of B, and 13 A/B virus infections. RIDT showed 90.7% sensitivity and 95.7% specificity for influenza A virus detection, and 91.5% sensitivity and 95.3% specificity for influenza B virus detection. Overall VE was 33.2% (95% CI: 3.0-54.0; p = 0.02) against any laboratory-confirmed influenza infection. VE estimates against influenza B were higher for the quadrivalent vaccine. Immunization and occupational exposure were protective factors against influenza.

CONCLUSIONS

The RIDT was useful to detect influenza cases during an outbreak setting. Effectiveness of 2016/17 influenza vaccines administered in Mexico was low but significant. Our data should be considered for future local epidemiological policies.

Diminished B-Cell Response After Repeat Influenza Vaccination

Annual vaccination with influenza vaccines is recommended for protection against influenza in the United States. Past clinical studies and meta-analysis, however, have reported conflicting results on the benefits of annual vaccination. B-cell responses elicited following repeat influenza vaccinations over multiple seasons have not been examined in detail. We analyzed the B-cell and antibody (Ab) responses in volunteers vaccinated yearly, from 2010 or 2011 through 2014, with seasonal trivalent inactivated influenza vaccines. Statistical analyses were designed to help correct for possible bias due to reduced sample size in the later years of the study. We show that, after the second annual vaccination, the frequency of vaccine-specific plasmablasts and the binding reactivity of plasmablast-derived polyclonal Abs are reduced and do not increase in subsequent years. Similar trends are observed with the serum hemagglutination inhibition Ab response after each annual vaccination, as well as the binding reactivity of plasmablast-derived polyclonal Abs to the hemagglutinin of influenza A virus vaccine components, even with changes in the seasonal vaccine components during the study. Our findings indicate a diminished B-cell response to annual vaccination with seasonal trivalent influenza vaccine. These results emphasize the need for developing improved strategies to enhance the immunogenicity and efficacy of annual influenza vaccination.

ID2 and ID3 are indispensable for Th1 cell differentiation during influenza virus infection in mice

Antigen-specific Th1 cells could be a passage to the infection sites during infection to execute effector functions, such as help CD8⁺ T cells to localize in these sites by secretion of anti-viral cytokines-IFN-γ or direct cytotoxicity of antigen-bearing cells. However, the molecular components that modulate Th1 cell differentiation and function in response to viral infection remain incompletely understood. Here, we reported that both inhibitor of DNA binding 3(Id3) protein and inhibitor of DNA binding 2(Id2) protein promoted Th1 cell differentiation. Depletion of Id3 or Id2 led to severe defect of Th1 cell differentiation during influenza virus infection. Whereas depletion of both Id3 and Id2 in CD4⁺ T cells restrained Th1 cell differentiation to a greater extent, indicating that Id3 and Id2 nonredundantly regulate Th1 cell differentiation. Moreover, deletion of E-proteins, the antagonists of Id proteins, greatly enhanced Th1 cell differentiation. Mechanistic study indicated that E-proteins suppressed Th1 cell differentiation by directly binding to the regulatory elements of Th1 cell master regulator T-bet and regulate T-bet expression. Thus, our findings identified Id-protein's importance for Th1 cells and clarified the nonredundant role of Id3 and Id2 in regulating Th1 cell differentiation, providing novel insight that Id3-Id2-E protein axis are essential for Th1 cell polarization.

Diagnostic accuracy of the real-time PCR cobas® Liat® Influenza A/B assay and the Alere i Influenza A&B NEAR isothermal nucleic acid amplification assay for the detection of influenza using adult nasopharyngeal specimens

BACKGROUND

Accurate detection of influenza requires diagnostic testing; however, methods such as RADTs and central laboratory-based tests are limited by low sensitivity and time constraints, respectively.

OBJECTIVE

To compare the performances of the cobas^® Liat^® Influenza A/B and Alere™ i Influenza A&B point-of-care (POC) assays for detecting influenza A and B viruses using fresh nasopharyngeal specimens with the GenMark Dx^® Respiratory Viral Panel as the reference method, a FDA cleared IVD PCR test.

STUDY DESIGN

A total of 87 samples collected in viral transport medium from adults ≥18 years of age were re-tested on both POC assays (based on the reference PCR method, 29 were influenza A and 18 were influenza B virus positive).

RESULTS

The overall sensitivity and specificity of the cobas Influenza A/B for the detection of influenza A and B relative to reference PCR was 97.9% (95% confidence interval [CI] 88.9%, 99.6%) and 97.5% (95% CI: 87.1%, 99.6%), respectively, while the sensitivity of the Alere i Influenza A&B assay relative to the reference PCR method was 63.8% (95% CI: 49.5%, 76.0%) and the specificity was 97.5% (95% CI: 87.1%, 99.6%). The individual sensitivities and specificities of the cobas Influenza A/B assay for influenza A alone and influenza B alone were comparable to those of the reference PCR method (influenza A: sensitivity of 100% [95% CI: 88.3%, 100.0%] and specificity of 98.3% [95% CI: 90.9%, 99.7%]; influenza B: sensitivity of 94.4% [95% CI: 74.2%, 99.0%] and specificity of 100% [95% CI: 94.7%, 100.0%]). For the Alere i Influenza A&B assay, the individual specificities for influenza A and B were comparable to those of the reference PCR method (98.3% [95% CI: 90.9%, 99.7%] and 97.1% [95% CI: 90.0%, 99.2%], respectively), while the individual sensitivities were low relative to reference PCR (55.2% [95% CI: 37.5%, 71.6%] and 72.2% [95% CI: 49.1%, 87.5%], respectively).

CONCLUSION

The cobas Influenza A/B assay demonstrated performance equivalent to laboratory-based PCR, and could replace rapid antigen tests.

Role of omega-3 PUFA-derived mediators, the protectins, in influenza virus infection

Influenza A viruses are the causative agents of seasonal and pandemic infections. Influenza strains have recently emerged that show resistance to anti-viral drugs. Moreover, therapies in critically ill patients with severe influenza are limited, with the current anti-viral drugs showing disappointing results even in the absence of obvious viral resistance. Given the high mortality associated with avian H5N1 or H7N9 infections and the risk of pandemic potentials, effective drugs are needed for the treatment of severe influenza. A virus-host interaction is a multidimensional host response, in which not only genes and protein but also metabolites are up- or down-regulated, and cellular pathways and networks implicated in the viral pathogenesis are perturbed. Thus, it seems an attractive strategy to overcome influenza by targeting host metabolites and/or metabolic pathways involved in viral pathogenesis. Using lipidomics and lipid libraries screening, potectin D1 isomer (PDX) derived from the 15-lipoxygenase product 17S-H(p)DHA and/or 17HDHA precursor, has recently been identified, which suppresses influenza virus replication by inhibiting the nuclear export of viral mRNA rather than regulating resolution of inflammation. Contribution of the protectins to control influenza virus replication and their therapeutic potentials are reviewed here. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".