Transmission of aerosolized seasonal H1N1 influenza A to ferrets

Adenovirus type 5 SARS-CoV-2 vaccines delivered orally or intranasally reduced disease severity and transmission in a hamster model

Transmission-blocking strategies that slow the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and protect against coronavirus disease 2019 (COVID-19) are needed. We have developed an orally delivered adenovirus type 5-vectored SARS-CoV-2 vaccine candidate that expresses the spike protein. Here, we demonstrated that hamsters vaccinated by the oral or intranasal route had robust and cross-reactive antibody responses. We then induced a postvaccination infection by inoculating vaccinated hamsters with SARS-CoV-2. Orally or intranasally vaccinated hamsters had decreased viral RNA and infectious virus in the nose and lungs and experienced less lung pathology compared to mock-vaccinated hamsters after SARS-CoV-2 challenge. Naïve hamsters exposed in a unidirectional air flow chamber to mucosally vaccinated, SARS-CoV-2-infected hamsters also had lower nasal swab viral RNA and exhibited fewer clinical symptoms than control animals, suggesting that the mucosal route reduced viral transmission. The same platform encoding the SARS-CoV-2 spike and nucleocapsid proteins elicited mucosal cross-reactive SARS-CoV-2-specific IgA responses in a phase 1 clinical trial (NCT04563702). Our data demonstrate that mucosal immunization is a viable strategy to decrease SARS-CoV-2 disease and airborne transmission.

Non-respiratory particles emitted by guinea pigs in airborne disease transmission experiments

Animal models are often used to assess the airborne transmissibility of various pathogens, which are typically assumed to be carried by expiratory droplets emitted directly from the respiratory tract of the infected animal. We recently established that influenza virus is also transmissible via "aerosolized fomites," micron-scale dust particulates released from virus-contaminated surfaces (Asadi et al. in Nat Commun 11(1):4062, 2020). Here we expand on this observation, by counting and characterizing the particles emitted from guinea pig cages using an Aerodynamic Particle Sizer (APS) and an Interferometric Mie Imaging (IMI) system. Of over 9000 airborne particles emitted from guinea pig cages and directly imaged with IMI, none had an interference pattern indicative of a liquid droplet. Separate measurements of the particle count using the APS indicate that particle concentrations spike upwards immediately following animal motion, then decay exponentially with a time constant commensurate with the air exchange rate in the cage. Taken together, the results presented here raise the possibility that a non-negligible fraction of airborne influenza transmission events between guinea pigs occurs via aerosolized fomites rather than respiratory droplets, though the relative frequencies of these two routes have yet to be definitively determined.

Ferreting Out Influenza Virus Pathogenicity and Transmissibility: Past and Future Risk Assessments in the Ferret Model

As influenza A viruses continue to jump species barriers, data generated in the ferret model to assess influenza virus pathogenicity, transmissibility, and tropism of these novel strains continues to inform an increasing scope of public health-based applications. This review presents the suitability of ferrets as a small mammalian model for influenza viruses and describes the breadth of pathogenicity and transmissibility profiles possible in this species following inoculation with a diverse range of viruses. Adaptation of aerobiology-based techniques and analyses have furthered our understanding of data obtained from this model and provide insight into the capacity of novel and emerging influenza viruses to cause human infection and disease.

An association of Orf virus infection among sheep and goats with herd health programme in Terengganu state, eastern region of the peninsular Malaysia

BACKGROUND

Orf virus causes a scabby skin lesions which decreases productivity in small ruminants. The unknown status of this disease in the eastern region of Peninsular Malaysia warrants a study to determine sero-prevalence of orf with regards to farmers' compliance level towards the Herd Health Program (HHP) programme.

RESULTS

Out of 504 animals, 115 were positive for Orf-virus antibodies. An overall prevalence rate of 22.8% indicated a high prevalence of orf disease in this region. It was observed that 25.1% (92/367) of goats were positive and 16.8% (23/137) of sheep sero-converted for Orf virus antibody. Several factors were measured for their possible association with prevalence of Orf virus infection. The prevalence was higher in LY farm, JC breed, kid and female animals, and in the presence of disease lesion. Chi-square analysis showed a significant association of three risk factors which are species, age and sex of the animals (P < 0.05). Notwithstanding, all other variables showed no significant difference (P > 0.05). Farms surveyed usually practised intensive management system, keeping animals in the shade at all time, due to limited availability of suitable land as a free-range grazing area. An interview with small holder farmers revealed a lack of awareness of the main goals of herd health programme. An overall compliance level of 42.7% was observed for all HHP parameters. Among the 14 main components of HHP modules, animal identification had recorded highest compliance level (84.62%) while milking management recorded the least compliance (- 82.69%). That explained why there was a high sporadic prevalence of Orf infection in this region.

CONCLUSION

Good herd health supervision is a rehearsal target to prevent an outbreak and the spread of diseases thus reduces economic losses among farmers. Therefore, a good herd health programme should be in place, in order to prevent and control disease transmission as well as to improve herd immunity.

Pulmonary and Regional Deposition of Nebulized and Dry Powder Aerosols in Ferrets

The utilization of ferrets as a non-clinical model for disease is rapidly increasing within drug development. Many of these models include respiratory diseases that involve targeted drug delivery via nose-only inhalation. While the deposition patterns within other non-clinical models (mice, rats, canines, and non-human primates) have been well studied, the local and regional deposition of aerosols in ferrets has not been well characterized. Therefore, inhalation aerosols were developed, radiolabeled and the radiolabeling methods validated to support SPECT-CT imaging and quantification of regional deposition within ferrets. The studies were conducted with one liquid formulation and one dry powder formulation (two concentrations of dry powder). Additionally, both aerosols were polydisperse and therefore reflect the majority of pharmaceutical aerosols. Overall, the studies showed lung deposition fractions between 5 and 10% with median aerodynamic particle sizes of 2.5 and 2.8 μm. The lung deposition fraction of the liquid aerosol was ~ 9%, nearly double observed in rats with a similarly sized aerosol. Analysis of respiratory tract (oropharynx, laryngopharynx, trachea, bifurcation area, and lung) deposition indicates increased deposition of the liquid aerosol compared to the dry powder aerosol, however, when this analysis was refined to the pulmonary region (trachea, bifurcation, and lung) the deposition was similar between formulations. These data provide the first description of the regional deposition of inhalation aerosols in ferrets with standard nose-only inhalation procedures. These data can be used for calculations of both total and regional doses within ferret inhalation drug delivery.

CD4/CD8/Dendritic cell complexes in the spleen: CD8+ T cells can directly bind CD4+ T cells and modulate their response

CD4⁺ T cell help to CD8⁺ T cell responses requires that CD4⁺ and CD8⁺ T cells interact with the same antigen presenting dendritic cell (Ag⁺DC), but it remains controversial whether helper signals are delivered indirectly through a licensed DC and/or involve direct CD4⁺/CD8⁺ T cell contacts and/or the formation of ternary complexes. We here describe the first in vivo imaging of the intact spleen, aiming to evaluate the first interactions between antigen-specific CD4⁺, CD8⁺ T cells and Ag⁺DCs. We show that in contrast to CD4⁺ T cells which form transient contacts with Ag⁺DC, CD8⁺ T cells form immediate stable contacts and activate the Ag⁺DC, acquire fragments of the DC membranes by trogocytosis, leading to their acquisition of some of the DC properties. They express MHC class II, and become able to present the specific Marilyn peptide to naïve Marilyn CD4⁺ T cells, inducing their extensive division. In vivo, these CD8⁺ T cells form direct stable contacts with motile naïve CD4⁺ T cells, recruiting them to Ag⁺DC binding and to the formation of ternary complexes, where CD4⁺ and CD8⁺ T cells interact with the DC and with one another. The presence of CD8⁺ T cells during in vivo immune responses leads to the early activation and up-regulation of multiple functions by CD4⁺ T lymphocytes. Thus, while CD4⁺ T cell help is important to CD8⁺ T cell responses, CD8⁺ T cells can interact directly with naïve CD4⁺ T cells impacting their recruitment and differentiation.

Contact transmission of influenza virus between ferrets imposes a looser bottleneck than respiratory droplet transmission allowing propagation of antiviral resistance

Influenza viruses cause annual seasonal epidemics and occasional pandemics. It is important to elucidate the stringency of bottlenecks during transmission to shed light on mechanisms that underlie the evolution and propagation of antigenic drift, host range switching or drug resistance. The virus spreads between people by different routes, including through the air in droplets and aerosols, and by direct contact. By housing ferrets under different conditions, it is possible to mimic various routes of transmission. Here, we inoculated donor animals with a mixture of two viruses whose genomes differed by one or two reverse engineered synonymous mutations, and measured the transmission of the mixture to exposed sentinel animals. Transmission through the air imposed a tight bottleneck since most recipient animals became infected by only one virus. In contrast, a direct contact transmission chain propagated a mixture of viruses suggesting the dose transferred by this route was higher. From animals with a mixed infection of viruses that were resistant and sensitive to the antiviral drug oseltamivir, resistance was propagated through contact transmission but not by air. These data imply that transmission events with a looser bottleneck can propagate minority variants and may be an important route for influenza evolution.

Correlation between Virus Replication and Antibody Responses in Macaques following Infection with Pandemic Influenza A Virus

Influenza virus infection of nonhuman primates is a well-established animal model for studying pathogenesis and for evaluating prophylactic and therapeutic intervention strategies. However, usually a standard dose is used for the infection, and there is no information on the relation between challenge dose and virus replication or the induction of immune responses. Such information is also very scarce for humans and largely confined to evaluation of attenuated virus strains. Here, we have compared the effect of a commonly used dose (4 × 10(6) 50% tissue culture infective doses) versus a 100-fold-higher dose, administered by intrabronchial installation, to two groups of 6 cynomolgus macaques. Animals infected with the high virus dose showed more fever and had higher peak levels of gamma interferon in the blood. However, virus replication in the trachea was not significantly different between the groups, although in 2 out of 6 animals from the high-dose group it was present at higher levels and for a longer duration. The virus-specific antibody response was not significantly different between the groups. However, antibody enzyme-linked immunosorbent assay, virus neutralization, and hemagglutination inhibition antibody titers correlated with cumulative virus production in the trachea. In conclusion, using influenza virus infection in cynomolgus macaques as a model, we demonstrated a relationship between the level of virus production upon infection and induction of functional antibody responses against the virus.

IMPORTANCE

There is only very limited information on the effect of virus inoculation dose on the level of virus production and the induction of adaptive immune responses in humans or nonhuman primates. We found only a marginal and variable effect of virus dose on virus production in the trachea but a significant effect on body temperature. The induction of functional antibody responses, including virus neutralization titer, hemagglutination inhibition titer, and antibody-dependent cell-mediated cytotoxicity, correlated with the level of virus replication measured in the trachea. The study reveals a relationship between virus production and functional antibody formation, which could be relevant in defining appropriate criteria for new influenza virus vaccine candidates.

Animal models for influenza viruses: implications for universal vaccine development

Influenza virus infections are a significant cause of morbidity and mortality in the human population. Depending on the virulence of the influenza virus strain, as well as the immunological status of the infected individual, the severity of the respiratory disease may range from sub-clinical or mild symptoms to severe pneumonia that can sometimes lead to death. Vaccines remain the primary public health measure in reducing the influenza burden. Though the first influenza vaccine preparation was licensed more than 60 years ago, current research efforts seek to develop novel vaccination strategies with improved immunogenicity, effectiveness, and breadth of protection. Animal models of influenza have been essential in facilitating studies aimed at understanding viral factors that affect pathogenesis and contribute to disease or transmission. Among others, mice, ferrets, pigs, and nonhuman primates have been used to study influenza virus infection in vivo, as well as to do pre-clinical testing of novel vaccine approaches. Here we discuss and compare the unique advantages and limitations of each model.

Determination of infective dose of H9N2 Avian Influenza virus in different routes: aerosol, intranasal, and gastrointestinal

BACKGROUND

Low pathogenic H9N2 avian influenza virus (AIV) has been spreading worldwide, leading to huge economic losses to poultry husbandry, but few studies were concerned about its aerosol infection.

METHODS

This study compared the infective doses of H9N2 AIV to chickens by three different routes, aerosol infection, intranasal and gastrointestinal infection, and determination of the results was conducted by detecting virus shedding and seroconversion of chickens.

RESULTS

The results indicated that chickens were susceptible to H9N2 AIV with a different infection rate which depended on the route of inoculation. H9N2 AIV media aerosol-infective dose (aID₅₀) to chickens was about 491 TCID₅₀, intranasal infection was 398 TCID₅₀, and gastrointestinal infection was 19,952 TCID₅₀.

CONCLUSION

The infection ability of H9N2 AIV to chickens was related to its way of invading. The respiratory infection ability was about 40 times more effective than gastrointestinal infection, which suggested that urgent attention should be paid to environmental disinfection to block airborne transmission of influenza virus.

Animal models for influenza virus pathogenesis, transmission, and immunology

In humans, infection with an influenza A or B virus manifests typically as an acute and self-limited upper respiratory tract illness characterized by fever, cough, sore throat, and malaise. However, influenza can present along a broad spectrum of disease, ranging from sub-clinical or even asymptomatic infection to a severe primary viral pneumonia requiring advanced medical supportive care. Disease severity depends upon the virulence of the influenza virus strain and the immune competence and previous influenza exposures of the patient. Animal models are used in influenza research not only to elucidate the viral and host factors that affect influenza disease outcomes in and spread among susceptible hosts, but also to evaluate interventions designed to prevent or reduce influenza morbidity and mortality in man. This review will focus on the three animal models currently used most frequently in influenza virus research - mice, ferrets, and guinea pigs - and discuss the advantages and disadvantages of each.

Cognate antigen stimulation generates potent CD8(+) inflammatory effector T cells

Inflammatory reactions are believed to be triggered by innate signals and have a major protective role by recruiting innate immunity cells, favoring lymphocyte activation and differentiation, and thus contributing to the sequestration and elimination of the injurious stimuli. Although certain lymphocyte types such as TH17 cells co-participate in inflammatory reactions, their generation from the naïve pool requires the pre-existence of an inflammatory milieu. In this context, inflammation is always regarded as beginning with an innate response that may be eventually perpetuated and amplified by certain lymphocyte types. In contrast, we here show that even in sterile immunizations or in MyD88-deficient mice, CD8 T cells produce a burst of pro-inflammatory cytokines and chemokines. These functions follow opposite rules to the classic CD8 effector functions since they are generated prior to cell expansion and decline before antigen elimination. As few as 56 CD8(+) inflammatory effector cells in a lymph node can mobilize 10(7) cells in 24 h, including lymphocytes, natural killer cells, and several accessory cell types involved in inflammatory reactions. Thus, although inflammation modulates cognate responses, CD8 cognate responses also initiate local inflammatory reactions.

The experimental aerosol transmission of influenza virus

The threat of a virulent, highly transmissible pandemic virus has motivated an escalating research effort to identify the transmissible genotypes of animal viruses that cross over into the human population (animal–human transmission) and sustain human–human transmission. In addition to the pursuit of the viral genotype, a greater understanding of the host-virus phenotype of infectiousness, transmissibility and susceptibility will be required. This review examines experimental animal transmission of influenza for insights into human influenza transmission. Transmission is viewed as sequential steps that the virus must pass critical thresholds to achieve transmission and ultimately survival in the human host. In particular, a quantitative understanding in animal models of viral replication efficiency, airway viral load, exhaled viral aerosol load, environmental virus survival and host susceptibility will likely yield important insights. Computational modeling will enhance animal model data, as well as guide the use of pandemic mitigation strategies.

Mass spectrometric approaches to study enveloped viruses: new possibilities for structural biology and prophylactic medicine

This review considers principles of the use of mass spectrometry for the study of biological macromolecules. Some examples of protein identification, virion proteomics, testing vaccine preparations, and strain surveillance are represented. Possibilities of structural characterization of viral proteins and their posttranslational modifications are shown. The authors’ studies by MALDI-MS on S-acylation of glycoproteins from various families of enveloped viruses and on oligomerization of the influenza virus hemagglutinin transmembrane domains are summarized.

Innovations in modeling influenza virus infections in the laboratory

Respiratory viruses represent one of the most substantial infectious disease burdens to the human population today, and in particular, seasonal and pandemic influenza viruses pose a persistent threat to public health worldwide. In recent years, advances in techniques used in experimental research have provided the means to better understand the mechanisms of pathogenesis and transmission of respiratory viruses, and thus more accurately model these infections in the laboratory. Here, we briefly review the model systems used to study influenza virus infections, and focus particularly on recent advances that have increased our knowledge of these formidable respiratory pathogens.

Exhaled aerosol transmission of pandemic and seasonal H1N1 influenza viruses in the ferret

Person-to-person transmission of influenza viruses occurs by contact (direct and fomites) and non-contact (droplet and small particle aerosol) routes, but the quantitative dynamics and relative contributions of these routes are incompletely understood. The transmissibility of influenza strains estimated from secondary attack rates in closed human populations is confounded by large variations in population susceptibilities. An experimental method to phenotype strains for transmissibility in an animal model could provide relative efficiencies of transmission. We developed an experimental method to detect exhaled viral aerosol transmission between unanesthetized infected and susceptible ferrets, measured aerosol particle size and number, and quantified the viral genomic RNA in the exhaled aerosol. During brief 3-hour exposures to exhaled viral aerosols in airflow-controlled chambers, three strains of pandemic 2009 H1N1 strains were frequently transmitted to susceptible ferrets. In contrast one seasonal H1N1 strain was not transmitted in spite of higher levels of viral RNA in the exhaled aerosol. Among three pandemic strains, the two strains causing weight loss and illness in the intranasally infected 'donor' ferrets were transmitted less efficiently from the donor than the strain causing no detectable illness, suggesting that the mucosal inflammatory response may attenuate viable exhaled virus. Although exhaled viral RNA remained constant, transmission efficiency diminished from day 1 to day 5 after donor infection. Thus, aerosol transmission between ferrets may be dependent on at least four characteristics of virus-host relationships including the level of exhaled virus, infectious particle size, mucosal inflammation, and viral replication efficiency in susceptible mucosa.