The threat and prospects for control of an influenza pandemic

Screening and Validation of Odorants against Influenza A Virus Using Interpretable Regression Models

Influenza is a respiratory infection caused by the influenza virus that is prevalent worldwide. One of the most contagious variants of influenza is influenza A virus (IAV), which usually spreads in closed spaces through aerosols. Preventive measures such as novel compounds are needed that can act on viral membranes and provide a safe environment against IAV infection. In this study, we screened compounds with common fragrances that are generally used to mask unpleasant odors but can also exhibit antiviral activity against a strain of IAV. Initially, a set of 188 structurally diverse odorants were collected, and their antiviral activity was measured in vapor phase against the IAV solution. Regression models were built for the prediction of antiviral activity using this set of odorants by taking into account their structural features along with vapor pressure and partition coefficient (n-octanol/water). The models were interpreted using a feature weighting approach and Shapley Additive exPlanations to rationalize the predictions as an additional validation for virtual screening. This model was used to screen odorants from an in-house odorant data set consisting of 2020 odorants, which were later evaluated using in vitro experiments. Out of 11 odorants proposed using the final model, 8 odorants were found to exhibit antiviral activity. The feature interpretation of screened odorants suggested that they contained hydrophilic substructures, such as hydroxyl group, which might contribute to denaturation of proteins on the surface of the virus. These odorants should be explored as a preventive measure in closed spaces to decrease the risk of infections of IAV.

A Therapeutically Active Minibody Exhibits an Antiviral Activity in Oseltamivir-Resistant Influenza-Infected Mice via Direct Hydrolysis of Viral RNAs

Emerging Oseltamivir-resistant influenza strains pose a critical public health threat due to antigenic shifts and drifts. We report an innovative strategy for controlling influenza A infections by use of a novel minibody of the 3D8 single chain variable fragment (scFv) showing intrinsic viral RNA hydrolyzing activity, cell penetration activity, and epidermal cell penetration ability. In this study, we examined 3D8 scFv’s antiviral activity in vitro on three different H1N1 influenza strains, one Oseltamivir-resistant (A/Korea/2785/2009pdm) strain, and two Oseltamivir-sensitive (A/PuertoRico/8/1934 and A/X-31) strains. Interestingly, the 3D8 scFv directly digested viral RNAs in the ribonucleoprotein complex. scFv’s reduction of influenza viral RNA including viral genomic RNA, complementary RNA, and messenger RNA during influenza A infection cycles indicated that this minibody targets all types of viral RNAs during the early, intermediate, and late stages of the virus’s life cycle. Moreover, we further addressed the antiviral effects of 3D8 scFv to investigate in vivo clinical outcomes of influenza-infected mice. Using both prophylactic and therapeutic treatments of intranasal administered 3D8 scFv, we found that Oseltamivir-resistant H1N1-infected mice showed 90% (prophylactic effects) and 40% (therapeutic effects) increased survival rates, respectively, compared to the control group. The pathological signs of influenza A in the lung tissues, and quantitative analyses of the virus proliferations supported the antiviral activity of the 3D8 single chain variable fragment. Taken together, these results demonstrate that 3D8 scFv has antiviral therapeutic potentials against a wide range of influenza A viruses via the direct viral RNA hydrolyzing activity.

Comparing the socio-economic implications of the 1918 Spanish flu and the COVID-19 pandemic in India: A systematic review of literature

The focus of the present study is to compare and assess the socio‐economic implications of the 1918 influenza pandemic and the COVID‐19 pandemic in India. Both pandemics are similar in the nature of their disease and spread, and have had a far‐reaching impact on society and economies worldwide. To achieve their objective, the researchers adopted the method of systematic literature review (SLR). The findings of the review have been categorised in four subsections: comparison of 1918 influenza and COVID‐19 pandemics in a global context; economic consequences of a pandemic in India; social consequences of a pandemic in India; and the pandemic mitigation measures adopted by India. The findings suggest there are similarities in the socio‐economic implications of the two pandemics and also indicate that developing countries face more severe implications of such pandemics as compared to developed countries. The research findings from the review of literature are followed by the recommendations made by the researchers.

The epidemiology of seasonal influenza after the 2009 influenza pandemic in Africa: a systematic review

Background

Influenza infection is a serious public health problem that causes an estimated 3 to 5 million cases and 250,000 deaths worldwide every year. The epidemiology of influenza is well-documented in high- and middle-income countries, however minimal effort had been made to understand the epidemiology, burden and seasonality of influenza in Africa. This study aims to assess the state of knowledge of seasonal influenza epidemiology in Africa and identify potential data gaps for policy formulation following the 2009 pandemic.

Method

We reviewed articles from Africa published into four databases namely: MEDLINE (PubMed), Google Scholar, Cochrane Library and Scientific Research Publishing from 2010 to 2019.

Results

We screened titles and abstracts of 2070 studies of which 311 were selected for full content evaluation and 199 studies were considered. Selected articles varied substantially on the basis of the topics they addressed covering the field of influenza surveillance (n=80); influenza risk factors and co-morbidities (n=15); influenza burden (n=37); influenza vaccination (n=40); influenza and other respiratory pathogens (n=22) and influenza diagnosis (n=5).

Conclusion

Significant progress has been made since the last pandemic in understanding the influenza epidemiology in Africa. However, efforts still remain for most countries to have sufficient data to allow countries to prioritize strategies for influenza prevention and control.

LTA1 is a safe, intranasal enterotoxin-based adjuvant that improves vaccine protection against influenza in young, old and B-cell-depleted (μMT) mice

Enterotoxin-based adjuvants including cholera toxin and heat-labile toxin (LT) are powerful manipulators of mucosal immunity; however, past clinical trials identified unacceptable neurological toxicity when LT or mutant AB5 adjuvant proteins were added to intranasal vaccines. Here, we examined the isolated enzymatic A1 domain of LT (LTA1) for intranasal safety and efficacy in combination with influenza (flu) vaccination. LTA1-treated mice exhibited no neurotoxicity, as measured by olfactory system testing and H&E staining of nasal tissue in contrast with cholera toxin. In vaccination studies, intranasal LTA1 enhanced immune responses to inactivated virus antigen and subsequent protection against H1N1 flu challenge in mice (8-week or 24-months). In addition, lung H1N1 viral titers post-challenge correlated to serum antibody responses; however, enhanced protection was also observed in μMT mice lacking B-cells while activation and recruitment of CD4 T-cells into the lung was apparent. Thus, we report that LTA1 protein is a novel, safe and effective enterotoxin adjuvant that improves protection of an intranasal flu vaccination by a mechanism that does not appear to require B-cells.

Immunity to Respiratory Infection Is Reinforced Through Early Proliferation of Lymphoid TRM Cells and Prompt Arrival of Effector CD8 T Cells in the Lungs

Cross-protection between serologically distinct strains of influenza A virus (IAV) is mediated by memory CD8 T cells that recognize epitopes from conserved viral proteins. Early viral control begins with activation of tissue-resident memory CD8 T cells (T_RM) cells at the site of viral replication. These CD8 T cells do not act in isolation, as protection against disseminated infection is reinforced by multiple waves of effector cells (T_EFF) that enter the lungs with different kinetics. To define how a protective CTL response evolves, we compared the functional properties of antiviral CD8 T cells in the respiratory tract and local lymphoid tissues. When analyzed 30 dpi, large numbers of antiviral CD8 T cells in the lungs and mediastinal lymph nodes (MLNs) expressed canonical markers of T_RM cells (CD69 and/or CD103). The check point inhibitor PD-1 was also highly expressed on NP-specific CD8 T cells in the lungs, while the ratios of CD8 T cells expressing CD69 and CD103 varied according to antigen specificity. We next used in vitro experiments to identify conditions that induce a canonical T_RM phenotype and found that that naïve and newly activated CD8 T cells maintain CD103 expression during culture with transforming growth factor-beta (TGFβ), while central memory CD8 T cells (T_CM) do not express CD103 under similar conditions. In vivo experiments showed that the distribution of antiviral CTLs in the MLN changed when immune mice were treated with reagents that block interactions with PD-L1. Importantly, the lymphoid T_RM cells were poised for early proliferation upon reinfection with a different strain of IAV and defenses in the lungs were augmented by a transient increase in numbers of T_EFF cells at the site of infection. As the interval between infections increased, lymphoid T_RM cells were replaced with T_CM cells which proliferated with delayed kinetics and contributed to an exaggerated inflammatory response in the lungs.

Limited Efficacy of Antibacterial Vaccination Against Secondary Serotype 3 Pneumococcal Pneumonia Following Influenza Infection

BACKGROUND

Secondary bacterial infections following influenza represent a major cause of mortality in the human population, which, in turn, has led to a call for stockpiling of bacterial vaccines for pandemic preparedness.

METHODS

To investigate the efficacy of bacterial vaccination for protection against secondary pneumococcal infection, mice were immunized with pneumococcal capsular polysaccharide conjugate vaccine, and then sequentially coinfected 5 weeks later with PR8 influenza virus and A66.1 Streptococcus pneumoniae.

RESULTS

In the absence of influenza virus exposure, vaccination with polysaccharide conjugate vaccine was highly effective, as indicated by 100% survival from lethal pneumococcal pneumonia and 10 000-fold greater efficiency in clearance of bacteria from the lung compared to unvaccinated mice. Enhanced clearance after vaccination was dependent upon Fc receptor (FcR) expression. However, following influenza, <40% of vaccinated mice survived bacterial coinfection and FcR-dependent clearance of antibody-opsonized bacteria reduced bacterial levels in the lungs only 5-10 fold. No differences in lung myeloid cell numbers or in FcR cell surface expression were observed following influenza.

CONCLUSIONS

The results show that induction of antibacterial humoral immunity is only partially effective in protection against secondary bacterial infections that occur following influenza, and suggest that additional therapeutic strategies to overcome defective antibacterial immunity should be explored.

Interferon-γ inhibits nonopsonized phagocytosis of macrophages via an mTORC1-c/EBPβ pathway

Bacterial infection often follows virus infection due to pulmonary interferon-γ (IFN-γ) production during virus infection, which down-regulates macrophage phagocytosis. The molecular mechanisms for this process are still poorly understood. In the present study, IFN-γ treatment significantly inhibited the ability of mouse macrophages to phagocytize nonopsonized chicken red blood cells (cRBCs), bacteria and beads in vitro, while it enhanced IgG- and complement-opsonized phagocytosis. IFN-γ treatment decreased the expression of MARCO (macrophage receptor with collagenous structure) in macrophages. Macrophages showed lower binding to and phagocytic ability of cRBCs when MARCO was blocked with antibody. In addition, IFN-γ induced high activity of mTOR (mammalian target of rapamycin) and decreased the expression of c/EBPβ (CCAAT enhancer-binding protein β) in macrophages. Rapamycin, a specific mTOR inhibitor, significantly reversed the inhibitory effect of IFN-γ on nonopsonized phagocytosis of macrophages and restored c/EBPβ and MARCO expression. Biochemical assays showed that c/EBPβ directly bound to the MARCO gene promoter. Rapamycin significantly hampered the viral-bacterial synergy and protected influenza-infected mice from subsequent bacterial infection. Thus, IFN-γ inhibited the nonopsonized phagocytosis of macrophages through the mTOR-c/EBPβ-MARCO pathway. The present study offered evidence indicating that mTOR may be one of the key target molecules for the prevention of secondary bacterial infection caused by primary virus infection.

Guarding the perimeter: protection of the mucosa by tissue-resident memory T cells

Mucosal tissues are continually bombarded with infectious agents seeking to gain entry into the body. The absence of a tough physical exterior layer surrounding these tissues creates a unique challenge for the immune system, which manages to provide broad protection against a plethora of different organisms with the aid of special adaptations that augment immunity at these vulnerable sites. For example, specialized populations of memory T lymphocytes reside at initial sites of pathogen entry into the body, where they provide an important protective barrier. Similar anatomically-confined populations of pathogen-specific CD8 T cells can be found near the outer margins of the body following recovery from a variety of local infections, where they share very similar phenotypic characteristics. How these tissue-resident T cells are retained in a single anatomic location where they can promote immunity is beginning to be defined. Here, we will review current knowledge of the mechanisms that help establish and maintain these regional lymphocytes in the mucosal tissues and discuss relevant data that enhance our understanding of the contribution of these lymphocyte populations to protective immunity against infectious diseases.

Seasonal, avian, and novel H1N1 influenza: prevention and treatment modalities

OBJECTIVE

To review the pathophysiology, pandemics/epidemics, transmissibility, clinical presentation, treatment, prevention/immunization, and resistance associated with seasonal, avian, and swine influenza.

DATA SOURCES

Literature was obtained from MEDLINE (1966-October 2009) and International Pharmaceutical Abstracts (1971-October 2009) using the search terms influenza, seasonal influenza, avian influenza, swine influenza, H1N1, novel H1N1, H3N2, and H5N1.

STUDY SELECTION AND DATA EXTRACTION

Available English-language articles were reviewed, along with information obtained from the Centers for Disease Control and Prevention, the Food and Drug Administration, and the World Health Organization.

DATA SYNTHESIS

The influenza virus has caused disease in birds, swine, and humans for many centuries. Pandemics and epidemics have occurred throughout history and reports of new strains continue to emerge. Two major surface antigenic glycoproteins, hemagglutinin and neuraminidase, have various subtypes, resulting in numerous combinations of these proteins. For example, combinations occur when an influenza strain from a bird "mixes" with a strain from a human. This mixing occurs in a host, often in pigs, resulting in a new strain. This new strain can cause pandemics since people have no immunity to the new strain. An H1N1 subtype pandemic occurred in 1918, causing millions of deaths. Simultaneously, veterinary reports of "influenza" in pigs also emerged. It is postulated that humans infected pigs with this H1N1 virus. H1N1 reappeared in humans in 1976, and more recently in 2009. Other pandemics have occurred with H2N2 and H3N2 strains. In 1997, strain H5N1, which usually causes disease in fowl, was able to infect humans.

CONCLUSIONS

Influenza subtypes continue to change, causing disease in animals and humans. Utilization of immunization and antiviral treatment options are available to prevent, treat, and contain the spread of this infection.

Inhibition of pulmonary antibacterial defense by interferon-gamma during recovery from influenza infection

Secondary bacterial infection often occurs after pulmonary virus infection and is a common cause of severe disease in humans, yet the mechanisms responsible for this viral-bacterial synergy in the lung are only poorly understood. We now report that pulmonary interferon-gamma (IFN-gamma) produced during T cell responses to influenza infection in mice inhibits initial bacterial clearance from the lung by alveolar macrophages. This suppression of phagocytosis correlates with lung IFN-gamma abundance, but not viral burden, and leads to enhanced susceptibility to secondary pneumococcal infection, which can be prevented by IFN-gamma neutralization after influenza infection. Direct inoculation of IFN-gamma can mimic influenza infection and downregulate the expression of the class A scavenger receptor MARCO on alveolar macrophages. Thus, IFN-gamma, although probably facilitating induction of specific anti-influenza adaptive immunity, suppresses innate protection against extracellular bacterial pathogens in the lung.

Protective measures and human antibody response during an avian influenza H7N3 outbreak in poultry in British Columbia, Canada

BACKGROUND

In 2004 an outbreak of avian influenza of the H7N3 subtype occurred among poultry in British Columbia, Canada. We report compliance with recommended protective measures and associated human infections during this outbreak.

METHODS

We sought voluntary participation by anyone (cullers, farmers and their families) involved in efforts to control the poultry outbreak. Recruitment was by advertisements at the worker deployment site, in local media and through newsletters sent directly to farmers. Sera were tested for antibody to H7N3 by microneutralization assay. A subset of 16 sera (including convalescent sera from 2 unprotected workers with conjunctivitis from whom virus had been isolated) was further tested by Western blot and routine and modified hemagglutination inhibition assays.

RESULTS

A total of 167 people (20% to 25% of all workers) participated between May 7 and July 26, 2004. Of these, 19 had experienced influenza-like illness and 21 had experienced red or watery eyes. There was no significant association between illness reports and exposure to infected birds. Among 65 people who entered barns with infected birds, 55 (85%) had received influenza vaccine, 48 (74%) had received oseltamivir, and 55 (85%), 54 (83%) and 36 (55%) reported always wearing gloves, mask or goggles, respectively. Antibody to the H7 subtype was not detected in any sera.

INTERPRETATION

During the BC outbreak, compliance with recommended protective measures, especially goggles, was incomplete. Multiple back-up precautions, including oseltamivir prophylaxis, may prevent human infections and should be readily accessible and consistently used by those involved in the control of future outbreaks of avian influenza in poultry. Localized human avian influenza infections may not result in serologic response despite confirmed viral detection and culture.

Anti-influenza prodrug oseltamivir is activated by carboxylesterase human carboxylesterase 1, and the activation is inhibited by antiplatelet agent clopidogrel

Oseltamivir is the main medicine recommended by the World Health Organization in anticipation of next influenza pandemic. This anti-influenza viral agent is an ester prodrug, and the antiviral activity is achieved by its hydrolytic metabolite: oseltamivir carboxylate. In this study, we report that the hydrolytic activation is catalyzed by carboxylesterase human carboxylesterase (HCE) 1. Liver microsomes rapidly hydrolyzed oseltamivir, but no hydrolysis was detected with intestinal microsomes or plasma. The overall rate of the hydrolysis varied among individual liver samples and was correlated well with the level of HCE1. Recombinant HCE1 but not HCE2 hydrolyzed this prodrug and produced similar kinetic parameters as the liver microsomes. Several HCE1 natural variants differed from the wild-type enzyme on the hydrolysis of oseltamivir. In the presence of antiplatelet agent clopidogrel, the hydrolysis of oseltamivir was inhibited by as much as 90% when the equal concentration was assayed. Given the fact that hydrolysis of oseltamivir is required for its therapeutic activity, concurrent use of both drugs would inhibit the activation of oseltamivir, thus making this antiviral agent therapeutically inactive. This is epidemiologically of significance because people who receive oseltamivir and clopidogrel simultaneously may maintain susceptibility to influenza infection or a source of spreading influenza virus if already infected.

Pandemics, avian influenza A (H5N1), and a strategy for pharmacists

Epidemics of influenza occur annually and account for more morbidity in the developed world than all other respiratory diseases combined. On average, 36,000 Americans die from influenza or its complications each year. Pandemics occur when influenza viruses undergo either antigenic drift or antigenic shift that results in a new viral strain that infects humans, when they are capable of sustained transmission from person-to-person, and when they are introduced in populations with little or no preexisting immunity. The influenza pandemic of 1918 caused an estimated 20-40 million deaths worldwide. An avian influenza A (H5N1) virus, currently circulating in Asia, has pandemic potential. However, no evidence currently exists that a pandemic is occurring. Pharmacists are uniquely positioned to initiate nearterm practice changes that may positively impact both seasonal and potential pandemic morbidity and mortality. Pharmacists must be immunization advocates and provide pharmaceutical care that includes evaluation of immunization status. Increasing immunization to prevent invasive pneumococcal disease, as well as seasonal influenza immunization, is encouraged. A pandemic vaccine represents the most effective strategy to mitigate the effects of a pandemic. Antiviral agents represent a treatment bridge until a pandemic-specific vaccine is available. The neuraminidase inhibitors oseltamivir and zanamivir are active against H5N1, although oseltamivir resistance has been reported. Advances in vaccine research, development, and production through the use of reverse-genetics systems represent the most effective technology to rapidly produce a pandemic influenza vaccine.

Avian Flu to Human Influenza

Influenza A viral infection causes substantial annual morbidity and mortality worldwide, particularly for infants, the elderly, and the immunocompromised. The virus mainly replicates in the respiratory tract and is spread by respiratory secretions. A growing concern is the recent identification of H5N1 strains of avian influenza A in Asia that were previously thought to infect only wild birds and poultry, but have now infected humans, cats, pigs, and other mammals, often with fatal results, in an ongoing outbreak. A human pandemic with H5N1 virus could potentially be catastrophic because most human populations have negligible antibody-mediated immunity to the H5 surface protein and this viral subtype is highly virulent. Whether an H5N1 influenza pandemic will occur is likely to hinge on whether the viral strains involved in the current outbreak acquire additional mutations that facilitate efficient human-to-human transfer of infection. Although there is no historical precedent for an H5N1 avian strain causing widespread human-to-human transmission, some type of influenza A pandemic is very likely in the near future. The possibility of an H5N1 influenza pandemic has highlighted the many current limitations of treatment with antiviral agents and of vaccine production and immunogenicity. Future vaccine strategies that may include more robust induction of T-cell responses, such as cytotoxic T lymphocytes, may provide better protection than is offered by current vaccines, which rely solely or mainly on antibody neutralization of infection.

Reactogenicity and immunogenicity of an inactivated influenza vaccine administered by intramuscular or subcutaneous injection in elderly adults

In many countries there is no clear recommendation regarding the preferred route of administration of inactivated influenza vaccines. In a randomised, observer blind study of 720 elderly subjects, a split, trivalent influenza vaccine was significantly more immunogenic for both A strains (H3N2 and H1N1, p = 0.0016 and 0.003, respectively) when given intramuscularly compared to subcutaneously. This difference was due entirely to a gender effect, with females in the intramuscular (IM) group having a significantly greater serological response than females in the subcutaneous (SC) group for both of these strains. Similar results were seen with local adverse effects. These data suggest that vaccination practices that ensure intramuscular injection are required for optimal administration of influenza vaccines in the elderly.