Research on influenza virus in LM-S laboratory is partially funded by The New York Influenza Center of Excellence (NYICE), a member of the NIAID Centers of Excellence for Influenza Research and Surveillance (CEIRS). We thank Wendy Bates for her support in the corrections of the manuscript.

<ol>
	<li>Girard, M. P., Cherian, T., Pervikov, Y., Kieny, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+vaccine+research+and+development:+human+acute+respiratory+infections.">A review of vaccine research and development: human acute respiratory infections.</a> Vaccine. 23 (50), 5708-5724 (2005).</li><li>Arnold, S., Monto, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology+and+Virology+of+Influenza+Illness.">Epidemiology and Virology of Influenza Illness.</a> Am J Manag Care. 6, 255-264 (2000).</li><li>Palese, P., Shaw, M. L., Knipe, D. M., Howley, P. M., Griffin, D. E., Lamb, R. A., Martin, M. 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S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genesis+of+a+highly+pathogenic+and+potentially+pandemic+H5N1+influenza+virus+in+eastern+Asia.">Genesis of a highly pathogenic and potentially pandemic H5N1 influenza virus in eastern Asia.</a> Nature. 430 (6996), 209-213 (2004).</li><li>Nogales, A., Martinez-Sobrido, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reverse+Genetics+Approaches+for+the+Development+of+Influenza+Vaccines.">Reverse Genetics Approaches for the Development of Influenza Vaccines.</a> Int J Mol Sci. 18 (20), (2017).</li><li>Kunisaki, K. M., Janoff, E. 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F., Nogales, A., Martinez-Sobrido, L., Dewhurst, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+mouse-adapted+live+attenuated+influenza+virus+that+permits+in+vivo+analysis+of+enhancements+to+the+safety+of+live+attenuated+influenza+virus+vaccine.">Development of a mouse-adapted live attenuated influenza virus that permits in vivo analysis of enhancements to the safety of live attenuated influenza virus vaccine.</a> J Virol. 89 (6), 3421-3426 (2015).</li><li>Nogales, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influenza+A+Virus+Attenuation+by+Codon+Deoptimization+of+the+NS+Gene+for+Vaccine+Development.">Influenza A Virus Attenuation by Codon Deoptimization of the NS Gene for Vaccine Development.</a> J Virol. 88 (18), 10525-10540 (2014).</li><li>Nogales, A., DeDiego, M. 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The authors have nothing to disclose.

The mouse model of IAV is widely used for in vivo studies of IAV pathogenesis, immunogenicity and protection efficacy. The small size of mice makes them easy to manipulate and store as compared to other animal models such as ferrets or guinea pigs. Moreover, the ease in terms of animal cost, housing and reproduction allow their use in pre-clinical vaccination tests in which large numbers of animals are needed. Notably, since mice have been used in multiple research disciplines, several molecular and immunology m...

IAVs are enveloped viruses classified in the Orthomyxoviridae family3. They contain eight single-stranded RNA molecules with negative polarity3. In humans, IAVs cause seasonal epidemics and occasional pandemics of important consequence when novel viruses are introduced in the human population4. Moreover, seasonal IAVs are highly and rapidly transmitted between humans producing an elevated economic loss worldwide every year2,5. IAV symptoms include cough, nasal congestion, fever, malaise, headache, anorexia and myalgia, but the virus can also produce a more severe disease in immunocompromised patients6. In fact, the World Health Organization (WHO) calculates that seasonal influenza viruses cause 300,000 - 500,000 deaths worldwide every year1. There are only two classes of drugs currently approved by the Food and Drug Administration (FDA) for influenza prophylaxis and treatment in humans: neuraminidase (NA) inhibitors (e.g., oseltamivir) and blockers of the M2 ion channel (e.g., amantadine); however, the emergence of drug-resistant virus variants is an increasing concern. Vaccination, therefore, remains the best medical option to protect humans against IAVs infections. To date, three types of influenza vaccines licensed by the FDA for human use are available: recombinant viral hemagglutinin (HA) protein vaccines, inactivated influenza vaccines (IIV), and live-attenuated influenza vaccines (LAIV)5,7. The three vaccines are designed to induce adaptive immune response against the viral HA protein, the major target of neutralizing antibodies against IAVs.
A validated mouse model to study IAV infection in vivo
Animal models have been used to study, among others, IAV pathogenesis8,9,10,11, viral factors that contribute to disease12 and/or viral transmission13,14, and to test the efficacy of new vaccines or antiviral drugs9,10,15. Mice (Mus musculus) are the most extensively used animal model for IAV research for several reasons: 1) the immune system is evolutionarily similar to that present in humans; 2) low cost, including animal purchase, housing and reproduction; 3) small size to easily manipulate and store; 4) minimal host variability to obtain homogeneous responses and results; 5) a large knowledge of mice biology, including genome sequence; 6) many available molecular biology and/or immunology reagents; 7) available knock out (KO) mice to study the contribution of a given host protein on viral infection; and, 8) multiple mouse strains that can be exploited to evaluate the genetic basis of infections.
There are several mouse strains currently available to study IAV in vivo. Age, immune status, sex, genetic background and mouse strain as well as routes of infection, dose and viral strains all influence the outcome of IAV infection in mice. The most common mouse strains used in IAV research are C57BL/6, BALB/C and, more recently, DBA.2 mice since they are more susceptible to IAV disease than the two former strains16,17,18,19,20. Importantly, the immune response also can be different depending on the mouse strain18,19,20. Thus, it is very important to recover all the available information about the mouse and IAV strain to choose the best option for the experiment to be conducted.
Although mouse is a good animal model of infection for in vivo studies with IAV, they have several limitations, which need to be considered in the experimental design. For instance, a major limitation of using mice for in vivo studies is that IAVs do not transmit among mice. Thus, for transmission studies, more accepted animal models (e.g., ferrets or guinea pigs) are used16,17,21. In addition, there are several differences between the manifestations of IAV in mice and humans. Unlike humans, mice do not develop fever upon IAV infection; conversely they present with hypothermia16,17. In mice, IAV replication is concentrated in the lower respiratory tract (lungs) rather than the upper airways. Thus, virulence of IAV in mice is not always correlated to that seen in humans. Altogether, because the advantages outweigh the limited disadvantages, mouse represents the first animal model used to evaluate influenza viral pathogenesis, immunogenicity and protective efficacy in vaccine and antiviral studies. Moreover, it would not be ethically acceptable to conduct studies with IAV using large animal models without previous evidence in a small animal model of IAV infection. In this manuscript, we describe how to infect mice intranasally (i.n.) with IAV, how to monitor the severity and progress of viral infection and how to carry out the experiments required to evaluate humoral immune responses and protection efficacy.

<table><tbody><tr><td>Madin-Darby Canine Kidney (MDCK) epithelial cells</td><td>ATCC</td><td>CCL-34</td><td></td></tr><tr><td>Six- to eight-week-old female C57BL/6 mice</td><td>National Cancer Institute (NCI)</td><td>01XBE</td><td></td></tr><tr><td>Turckey red blod cells</td><td>Biolink Inc</td><td></td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Dulbecco&amp;rsquo;s modified Eagle&amp;rsquo;s medium (DMEM)</td><td>Corning Cellgro</td><td>15-013-CV</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Fetal Bovine Serum (FBS)</td><td>Seradigm</td><td>1500-050</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Penicillin/Streptomycin/L-Glutamine (PSG) 100x</td><td>Corning</td><td>30-009-CI</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Penicillin/Streptomycin (PS) 100x</td><td>Corning</td><td>30-00-CI</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Bovin Albumin solution (BA)</td><td>Sigma-Aldrich</td><td>A7409</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Bovin Serum Albumin (BSA)</td><td>Sigma-Aldrich</td><td>A9647</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Tosylsulfonyl phenylalanyl chloromethyl ketone (TPCK)-treated trypsin</td><td>Sigma-Aldrich</td><td>T8802</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Neutral Buffered Formalin 10%</td><td>EMD</td><td>65346-85</td><td>Store at RT</td></tr><tr><td>Triton X-100</td><td>J.T.Baker</td><td>X198-07</td><td>Store at RT</td></tr><tr><td>Monoclonal Antibody anti-NP Influenza A Virus HB-65</td><td>ATTC</td><td>H16-L10-4R5</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Polyclonal rabbit anti-mouse immunoglobulins/FITC</td><td>Dako</td><td>F0261</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>ECL Anti-mouse IgG, Horseradish Peroxidase linked whole antibody</td><td>GE Healthcare</td><td>LNA931V/AG</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>TMB substrate set</td><td>BioLegend</td><td>421101</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Vmax Kinetic plate reader</td><td>Molecular Devices</td><td></td><td></td></tr><tr><td>Dounce Tissue Grinders</td><td>Thomas Scientific</td><td>7722-7</td><td></td></tr><tr><td>Receptor destroying enzyme, RDE (II)</td><td>Denka Seiken Co.</td><td>370013</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Crystal Violet</td><td>Fisher Scienctific</td><td>C581-100</td><td>Store at RT</td></tr><tr><td>96-well Cell Culture Plate</td><td>Greiner Bio-one</td><td>655-180</td><td></td></tr><tr><td>Cell Culture dishes 100 mm</td><td>Greiner Bio-one</td><td>664-160</td><td></td></tr><tr><td>Nunc MicroWell 96-Well Microplates</td><td>Thermo Fisher Scienctific</td><td>269620</td><td></td></tr><tr><td>Nunc 96-Well Polystyrene Conical Bottom MicroWell Plates</td><td>Thermo Fisher Scienctific</td><td>249570</td><td></td></tr><tr><td>Puralub Vet Ointment</td><td>Dechra</td><td>9N-76855</td><td></td></tr><tr><td>Fluorescent microscope</td><td>Olympus</td><td>Olympus IX81</td><td></td></tr></tbody></table>

influenza a virus studies in a mouse model of infection

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone considering direct medical and hospitalization expenses and work absenteeism2. Animal models are crucial in Influenza A virus (IAV) studies to evaluate viral pathogenesis, host-pathogen interactions, immune responses, and the efficacy of current and/or novel vaccine approaches as well as antivirals. Mice are an advantageous small animal model because their immune system is evolutionarily similar to that found in humans, they are available from commercial vendors as genetically identical subjects, there are multiple strains that can be exploited to evaluate the genetic basis of infections, and they are relatively inexpensive and easy to manipulate. To recapitulate IAV infection in humans via the airways, mice are first anesthetized prior to intranasal inoculation with infectious IAVs under proper biosafety containment. After infection, the pathogenesis of IAVs is determined by monitoring daily the morbidity (body weight loss) and mortality (survival) rate. In addition, viral pathogenesis can also be evaluated by assessing virus replication in the upper (nasal mucosa) or lower (lungs) respiratory tract of infected mice. Humoral responses upon IAV infection can be rapidly evaluated by non-invasive bleeding and secondary antibody detection assays aimed at detecting the presence of total or neutralizing antibodies. Here, we describe the common methods used to infect mice intranasally (i.n) with IAV and evaluate pathogenesis, humoral immune responses and protection efficacy.

Characterization of viral pathogenesis in mice
The pathogenesis of IAV is related to the morbidity and mortality caused by its infection. These two parameters can be evaluated in mice easily: IAV morbidity is associated with body weight loss in infected mice and the percentage of survival will indicate the mortality rate (Figure 1). The body weight and survival in IAV-infected mice are usually monitore...

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Influenza A Virus Studies in a Mouse Model of Infection

Influenza A viruses (IAVs) are important human respiratory pathogens. To understand the pathogenicity of IAVs and to perform preclinical testing of novel vaccine approaches, animal models mimicking human physiology are required. Here, we describe techniques to evaluate IAV pathogenesis, humoral responses and vaccine efficacy using a mouse model of infection.

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone ...

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28.1K Views.  University of Rochester School of Medicine and Dentistry. Influenza A viruses (IAVs) are important human respiratory pathogens. To understand the pathogenicity of IAVs and to perform preclinical testing of novel vaccine approaches, animal models mimicking human physiology are required. Here, we describe techniques to evaluate IAV pathogenesis, humoral responses and vaccine efficacy using a mouse model of infection.

Video: Influenza A Virus Studies in a Mouse Model of Infection

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

High-throughput Detection Method for Influenza Virus

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, precise diagnosis of the infecting strain and rapid high-throughput screening of vast numbers of clinical samples is paramount to control the spread of pandemic infections. Current clinical diagnoses of influenza infections are based on serologic testing, polymerase chain reaction, direct specimen immunofluorescence and cell culture 1,2.
Here, we report the development of a novel diagnostic technique used to detect live influenza viruses. We used the mouse-adapted human A/PR/8/34 (PR8, H1N1) virus 3 to test the efficacy of this technique using MDCK cells 4. MDCK cells (104 or 5 x 103 per well) were cultured in 96- or 384-well plates, infected with PR8 and viral proteins were detected using anti-M2 followed by an IR dye-conjugated secondary antibody. M2 5 and hemagglutinin 1 are two major marker proteins used in many different diagnostic assays. Employing IR-dye-conjugated secondary antibodies minimized the autofluorescence associated with other fluorescent dyes. The use of anti-M2 antibody allowed us to use the antigen-specific fluorescence intensity as a direct metric of viral quantity. To enumerate the fluorescence intensity, we used the LI-COR Odyssey-based IR scanner. This system uses two channel laser-based IR detections to identify fluorophores and differentiate them from background noise. The first channel excites at 680 nm and emits at 700 nm to help quantify the background. The second channel detects fluorophores that excite at 780 nm and emit at 800 nm. Scanning of PR8-infected MDCK cells in the IR scanner indicated a viral titer-dependent bright fluorescence. A positive correlation of fluorescence intensity to virus titer starting from 102-105 PFU could be consistently observed. Minimal but detectable positivity consistently seen with 102-103 PFU PR8 viral titers demonstrated the high sensitivity of the near-IR dyes. The signal-to-noise ratio was determined by comparing the mock-infected or isotype antibody-treated MDCK cells.
Using the fluorescence intensities from 96- or 384-well plate formats, we constructed standard titration curves. In these calculations, the first variable is the viral titer while the second variable is the fluorescence intensity. Therefore, we used the exponential distribution to generate a curve-fit to determine the polynomial relationship between the viral titers and fluorescence intensities. Collectively, we conclude that IR dye-based protein detection system can help diagnose infecting viral strains and precisely enumerate the titer of the infecting pathogens.

This method describes the use of Infrared dye based imaging system for detection of H1N1 in bronchioalveolar lavage (BAL) fluid of infected mice at a high sensitivity. This methodology can be performed in a 96- or 384-well plate, requires &lt;10 &mu;l volume of test material and has the potential for concurrent screening of multiple pathogens.

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, ...

Intranasal Administration of Recombinant Influenza Vaccines in Chimeric Mouse Models to Study Mucosal Immunity

Vaccines are one of the greatest achievements of mankind, and have saved millions of lives over the last century. Paradoxically, little is known about the physiological mechanisms that mediate immune responses to vaccines perhaps due to the overall success of vaccination, which has reduced interest into the molecular and physiological mechanisms of vaccine immunity. However, several important human pathogens including influenza virus still pose a challenge for vaccination, and may benefit from immune-based strategies. 
Although influenza reverse genetics has been successfully applied to the generation of live-attenuated influenza vaccines (LAIVs), the addition of molecular tools in vaccine preparations such as tracer components to follow up the kinetics of vaccination in vivo, has not been addressed. In addition, the recent generation of mouse models that allow specific depletion of leukocytes during kinetic studies has opened a window of opportunity to understand the basic immune mechanisms underlying vaccine-elicited protection. Here, we describe how the combination of reverse genetics and chimeric mouse models may help to provide new insights into how vaccines work at physiological and molecular levels, using as example a recombinant, cold-adapted, live-attenuated influenza vaccine (LAIV). We utilized laboratory-generated LAIVs harboring cell tracers as well as competitive bone marrow chimeras (BMCs) to determine the early kinetics of vaccine immunity and the main physiological mechanisms responsible for the initiation of vaccine-specific adaptive immunity. In addition, we show how this technique may facilitate gene function studies in single animals during immune responses to vaccines. We propose that this technique can be applied to improve current prophylactic strategies against pathogens for which urgent medical countermeasures are needed, for example influenza, HIV, Plasmodium, and hemorrhagic fever viruses such as Ebola virus.

There is an overall lack of knowledge about how vaccines work. Here we propose the combined use of reverse genetics and bone marrow chimeric mice to gain insight into the early host immune responses to vaccines with a special focus on dendritic cells and T cell immunity.

Vaccines are one of the greatest achievements of mankind, and have saved millions of lives over the last century. Paradoxically, little is known about the ...

Using Zebrafish Models of Human Influenza A Virus Infections to Screen Antiviral Drugs and Characterize Host Immune Cell Responses

Each year, seasonal influenza outbreaks profoundly affect societies worldwide. In spite of global efforts, influenza remains an intractable healthcare burden. The principle strategy to curtail infections is yearly vaccination. In individuals who have contracted influenza, antiviral drugs can mitigate symptoms. There is a clear and unmet need to develop alternative strategies to combat influenza. Several animal models have been created to model host-influenza interactions. Here, protocols for generating zebrafish models for systemic and localized human influenza A virus (IAV) infection are described. Using a systemic IAV infection model, small molecules with potential antiviral activity can be screened. As a proof-of-principle, a protocol that demonstrates the efficacy of the antiviral drug Zanamivir in IAV-infected zebrafish is described. It shows how disease phenotypes can be quantified to score the relative efficacy of potential antivirals in IAV-infected zebrafish. In recent years, there has been increased appreciation for the critical role neutrophils play in the human host response to influenza infection. The zebrafish has proven to be an indispensable model for the study of neutrophil biology, with direct impacts on human medicine. A protocol to generate a localized IAV infection in the Tg(mpx:mCherry) zebrafish line to study neutrophil biology in the context of a localized viral infection is described. Neutrophil recruitment to localized infection sites provides an additional quantifiable phenotype for assessing experimental manipulations that may have therapeutic applications. Both zebrafish protocols described faithfully recapitulate aspects of human IAV infection. The zebrafish model possesses numerous inherent advantages, including high fecundity, optical clarity, amenability to drug screening, and availability of transgenic lines, including those in which immune cells such as neutrophils are labeled with fluorescent proteins. The protocols detailed here exploit these advantages and have the potential to reveal critical insights into host-IAV interactions that may ultimately translate into the clinic.

Systemic and localized zebrafish infection models for human influenza A virus are demonstrated. Using a systemic infection model, zebrafish can be used to screen antiviral drugs. Using a localized infection model, zebrafish can be used to characterize host immune cell responses.

Each year, seasonal influenza outbreaks profoundly affect societies worldwide. In spite of global efforts, influenza remains an intractable healthcare ...

Imaging Cell Interaction in Tracheal Mucosa During Influenza Virus Infection Using Two-photon Intravital Microscopy

The analysis of cell-cell or cell-pathogen interaction in vivo is an important tool to understand the dynamics of the immune response to infection. Two-photon intravital microscopy (2P-IVM) allows the observation of cell interactions in deep tissue in living animals, while minimizing the photobleaching generated during image acquisition. To date, different models for 2P-IVM of lymphoid and non-lymphoid organs have been described. However, imaging of respiratory organs remains a challenge due to the movement associated with the breathing cycle of the animal.
Here, we describe a protocol to visualize in vivo immune cell interactions in the trachea of mice infected with influenza virus using 2P-IVM. To this purpose, we developed a custom imaging platform, which included the surgical exposure and intubation of the trachea, followed by the acquisition of dynamic images of neutrophils and dendritic cells (DC) in the mucosal epithelium. Additionally, we detailed the steps needed to perform influenza intranasal infection and flow cytometric analysis of immune cells in the trachea. Finally, we analyzed neutrophil and DC motility as well as their interactions during the course of a movie. This protocol allows for the generation of stable and bright 4D images necessary for the assessment of cell-cell interactions in the trachea.

In this study, we present a protocol to perform two-photon intravital imaging and cell interaction analysis in the murine tracheal mucosa after infection with influenza virus. This protocol will be relevant for researchers studying immune cell dynamics during respiratory infections.

The analysis of cell-cell or cell-pathogen interaction in vivo is an important tool to understand the dynamics of the immune response to infection. ...

A Murine Model of Dengue Virus-induced Acute Viral Encephalitis-like Disease

Dengue virus (DENV), an arthropod-borne virus transmitted by mosquitoes, may cause the severe disease known as dengue hemorrhagic fever, which is characterized by lethal complications due to plasma leakage, ascites, pleural effusion, respiratory distress, severe bleeding, and organ impairment. A few cases of DENV infection present neurological manifestations; however, studies have not explored DENV-induced neuropathogenesis further. In this study, we present a protocol to use an immunocompetent outbred ICR (Institute of Cancer Research) mouse for investigating the induction of central nervous system (CNS) infection with DENV, followed by the progression of acute viral encephalitis-like disease.

Here, we present a protocol for creating an immunocompetent ICR (Institute of Cancer Research) murine model of central nervous system infection to display the development of neuropathy. Monitoring acute viral encephalitic disorders by identical disease scores could be performed for showing dengue virus-induced neuropathy in vivo.

Dengue virus (DENV), an arthropod-borne virus transmitted by mosquitoes, may cause the severe disease known as dengue hemorrhagic fever, which is ...

A Luciferase-fluorescent Reporter Influenza Virus for Live Imaging and Quantification of Viral Infection

Influenza A viruses (IAVs) cause human respiratory disease that is associated with significant health and economic consequences. As with other viruses, studying IAV requires the use of laborious secondary approaches to detect the presence of the virus in infected cells and/or in animal models of infection. This limitation has been recently circumvented with the generation of recombinant IAVs expressing easily traceable fluorescent or bioluminescent (luciferase) reporter proteins. However, researchers have been forced to select fluorescent or luciferase reporter genes due to the restricted capacity of the IAV genome for including foreign sequences. To overcome this limitation, we have generated a recombinant replication-competent bi-reporter IAV (BIRFLU) stably expressing both a fluorescent and a luciferase reporter gene to easily track IAV infections in vitro and in vivo. To this end, the viral non-structural (NS) and hemagglutinin (HA) viral segments of influenza A/Puerto Rico/8/34 H1N1 (PR8) were modified to encode the fluorescent Venus and the bioluminescent Nanoluc luciferase proteins, respectively. Here, we describe the use of BIRFLU in a mouse model of IAV infection and the detection of both reporter genes using an in vivo imaging system. Notably, we have observed a good correlation between the expressions of both reporters and viral replication. The combination of cutting-edge techniques in molecular biology, animal research and imaging technologies, provides researchers the unique opportunity to use this tool for influenza research, including the study of virus-host interactions and dynamics of viral infections. Importantly, the feasibility to genetically alter the viral genome to express two foreign genes from different viral segments opens up opportunities to use this approach for: (i) the development of novel IAV vaccines, (ii) the generation of recombinant IAVs that can be used as vaccine vectors for the treatment of other human pathogen infections.

Influenza A viruses (IAVs) are contagious respiratory pathogens that cause annual epidemics and occasional pandemics. Here, we describe a protocol to track viral infections in vivo using a novel recombinant luciferase and fluorescence-expressing bi-reporter IAV (BIRFLU). This approach provides researchers with an excellent tool to study IAV in vivo.

Influenza A viruses (IAVs) cause human respiratory disease that is associated with significant health and economic consequences. As with other viruses, ...

Evaluation of T Follicular Helper Cells and Germinal Center Response During Influenza A Virus Infection in Mice

T Follicular Helper (Tfh) cells are an independent CD4+&#160;T cell subset specialized in providing help for germinal center (GC) development and generation of high-affinity antibodies. In influenza virus infection, robust Tfh and GC B cell responses are induced to facilitate effective virus eradication, which confers a qualified mouse model for Tfh-associated study. In this paper, we described protocols in detection of basic Tfh-associated immune response during influenza virus infection in mice. These protocols include: intranasal inoculation of influenza virus; flow cytometry staining and analysis of polyclonal and antigen-specific Tfh cells, GC B cells and plasma cells; immunofluorescence detection of GCs; enzyme-linked immunosorbent assay (ELISA) of influenza virus-specific antibody in serum. These assays basically quantify the differentiation and function of Tfh cells in influenza virus infection, thus providing help for studies in elucidating differentiation mechanism and manipulation strategy.

This paper describes protocols of evaluating Tfh and GC B response in mouse model of influenza virus infection.

T Follicular Helper (Tfh) cells are an independent CD4+&#160;T cell subset specialized in providing help for germinal center (GC) development and ...

A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

Streptococcus pneumoniae (pneumococcus) is an asymptomatic colonizer of the nasopharynx in most individuals but can progress to a pulmonary and systemic pathogen upon influenza A virus (IAV) infection. Advanced age enhances host susceptibility to secondary pneumococcal pneumonia and is associated with worsened disease outcomes. The host factors driving those processes are not well defined, in part due to a lack of animal models that reproduce the transition from asymptomatic colonization to severe clinical disease. 
This paper describes a novel mouse model that recreates the transition of pneumococci from asymptomatic carriage to disease upon viral infection. In this model, mice are first intranasally inoculated with biofilm-grown pneumococci to establish asymptomatic carriage, followed by IAV infection of both the nasopharynx and lungs. This results in bacterial dissemination to the lungs, pulmonary inflammation, and obvious signs of illness that can progress to lethality. The degree of disease is dependent on the bacterial strain and host factors. 
Importantly, this model reproduces the susceptibility of aging, because compared to young mice, old mice display more severe clinical illness and succumb to disease more frequently. By separating carriage and disease into distinct steps and providing the opportunity to analyze the genetic variants of both the pathogen and the host, this S. pneumoniae/IAV co-infection model permits the detailed examination of the interactions of an important pathobiont with the host at different phases of disease progression. This model can also serve as an important tool for identifying potential therapeutic targets against secondary pneumococcal pneumonia in susceptible hosts.

A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

This paper describes a novel mouse model for the transition of pneumococcus from an asymptomatic colonizer to a disease-causing pathogen during viral infection. This model can be readily adapted to study polymicrobial and host-pathogen interactions during the different phases of disease progression and across various hosts.

Streptococcus pneumoniae (pneumococcus) is an asymptomatic colonizer of the nasopharynx in most individuals but can progress to a pulmonary and systemic ...

A Luciferase-Fluorescent Reporter Influenza Virus to Track Viral Infections

Source: Chiem, K., et al. <a href="https://app.jove.com/v/59890">A Luciferase-fluorescent Reporter Influenza Virus for Live Imaging and Quantification of Viral Infection.</a> J. Vis. Exp. (150), (2019).
This video demonstrates a method to track viral infections in mouse models using a recombinant luciferase and fluorescence protein-expressing bi-reporter Influenza A virus. This method enables both in vivo and ex vivo studies, enabling researchers to gain insights into viral dynamics and the effects of interventions.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. In ...

Influenza A Virus Studies in a Mouse Model of Infection

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Chapters in this video

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

High-throughput Detection Method for Influenza Virus

Intranasal Administration of Recombinant Influenza Vaccines in Chimeric Mouse Models to Study Mucosal Immunity

Using Zebrafish Models of Human Influenza A Virus Infections to Screen Antiviral Drugs and Characterize Host Immune Cell Responses

Imaging Cell Interaction in Tracheal Mucosa During Influenza Virus Infection Using Two-photon Intravital Microscopy

A Murine Model of Dengue Virus-induced Acute Viral Encephalitis-like Disease

A Luciferase-fluorescent Reporter Influenza Virus for Live Imaging and Quantification of Viral Infection

Evaluation of T Follicular Helper Cells and Germinal Center Response During Influenza A Virus Infection in Mice

A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness

A Luciferase-Fluorescent Reporter Influenza Virus to Track Viral Infections