Influenza Co-infection Research Articles

Evaluation of the influenza vaccine effectiveness among children aged 6 to 72 months based on the test-negative case control study design

Objective: To assess the effectiveness of seasonal influenza vaccine among children aged 6 to 72 months. Methods: The test-negative case control study was conducted based on available surveillance data which was from China Influenza Surveillance Information system (CSIS). From October 2016 to April 2017 and from October 2017 to April 2018,1 161 cases aged 6-72 months with influenza-like illness in Yongkang and Yiwu city, were selected as the study subjects, and the cases with influenza test-positive were selected as the case group (403 cases). Test-negative subjects were selected as control group (758 cases). The etiology and immunization data of the subjects were obtained from CSIS and Immune Information and Management System (IIMS) respectively. Vaccine effectiveness was estimated using multivariate logistic regression model,and the mixed effects of non-randomized control in TNCC study were equalized by using the propensity score (PS) method in the statistical analysis. Results: The age of the subjects was (2.44±1.60) years,and there were 681 boys (58.66%). The age of case group was (2.62±1.58) years, and there were 246 boys (61.04%). The case group was including of 237 cases (58.81%) of influenza A (H3N2), 92 cases (22.83%) of influenza A (H1N1) pmd09, 62 cases (15.38%) of influenza B(Victoria) lineage, 11 cases (2.73%) of influenza B (Yamagata) lineage and one case (0.25%) co-infection of influenza [A(H(3)N(2))+B (Victoria)]. The mean age of the control group was (2.35±1.61) years,and there were 435 boys (57.39%). Overall vaccine effectiveness (VE) against all type influenza for two seasons combined was 58% (95%CI: 31%-74%). An analysis by age groups showed 68% (95%CI:41%-82%) of the VE estimate among children aged 36-72 months while it was 28%(95%CI:-80%-71%)of the VE estimate among children aged 6-35 months. The VE estimate value was 54% (95%CI:16%-75%) against all type influenza and 65% (95%CI:24%-83%) against influenza A (H(3)N(2)) during the 2016-2017 season. During the 2017-2018 season, the VE estimate value was 69% (95%CI:18%-88%) against all type influenza. Conclusion: Influenza vaccine is effective in preventing influenza virus infection during the flu season,especially the effect among children aged 36-72 months is higher compared to that among children aged 6-35 months.

Co-infections, genetic, and antigenic relatedness of avian influenza H5N8 and H5N1 viruses in domestic and wild birds in Egypt

ABSTRACTA total of 50 poultry farms of commercial broilers (N = 39) and commercial layers (N = 11) suffered from respiratory problems and mortality during the period from January 2016 to December 2017 were investigated. Also, samples were collected from quail (N = 4), Bluebird (Sialis, N = 1), and Greenfinch (Chloris chloris, N = 1) for analysis. Respiratory viral pathogens were screened by PCR and positive samples were subjected to virus isolation and genetic identification. Antigenic relatedness of isolated avian influenza (AI) H5 subtype was evaluated using cross-hemagglutination inhibition. Results revealed that the incidence of single virus infections in commercial broilers was 64.1% (25/39), with the highest incidence for ND (33.3%) and H9N2 (20.5%), followed by H5N1 (7.7%) and H5N8 (2.7). Meanwhile, H9N2/ND mixed infection was the most observed case (7.7%). Other mixed infections H5N1/ND, H5N1/H9N2/ND, H5N1/H9N2/ND/IB, H9N2/IB, and H9N2/ILT were also observed (2.6% each). In commercial layers, H5N1 and ILT were the only detected single infections (18.1% each). Mixed H9N2/ND was the most predominant infection in layers (27.3%). Other mixed infections of H9N2/IB, H5N1/H5N8/H9N2, and H9N2/ND/IB were observed in 3 separate farms (9.1% each). The H5N8 virus was detected in one quail farm and 2 out of 3 wild bird's samples. Partial HA gene sequence analysis showed the clustering of the selected AI H5N8 within the 2.3.4.4 clade, while H5N1 clustered with the clade 2.2.1.2. Interestingly, the H5N8 isolated from chickens possessed 6 amino acids substitutions at HA1 compared to those isolated from wild birds with low antigenic relatedness to AI H5N1 clades 2.2.1 or 2.2.1.2. In conclusion, mixed viral infections were observed in both broiler and layer chickens in Egypt. The detected triple H5N1, H9N2, and H5N8 influenza co-infection raises the concern of potential AI epidemic strain emergence. The low genetic and antigenic relatedness between AI H5N1 and H5N8 viruses suggest the need for modification of vaccination strategies of avian influenza in Egypt along with strict biosecurity measures.

Enhanced inhibition of influenza virus infection by peptide-noble-metal nanoparticle conjugates.

The influenza (“flu”) type-A virus is a major medical and veterinary health concern and causes global pandemics. The peptide “FluPep” is an established inhibitor of influenza virus infectivity in model systems. We have explored the potential for noble-metal nanoparticle conjugates of FluPep to enhance its antiviral activity and to determine their potential as a delivery platform for FluPep. FluPep ligand is FluPep extended at its N-terminus with the sequence CVVVTAAA, to allow for its incorporation into a mixed-matrix ligand shell of a peptidol and an alkanethiol ethylene glycol consisting of 70% CVVVTol and 30% HS(CH2)11(OC2H4)4OH (mol/mol). Gold and silver nanoparticles (ca. 10 nm diameter) with up to 5% (mol/mol) FluPep ligand remained as stable as the control of mixed-matrix-passivated nanoparticles in a variety of tests, including ligand exchange with dithiothreitol. The free FluPep ligand peptide was found to inhibit viral plaque formation in canine MDCK cells (IC50 = 2.1 nM), but was less potent than FluPep itself (IC50 = 140 pM). Nanoparticles functionalised with FluPep ligand showed enhanced antiviral activity compared to the free peptides. The IC50 value of the FluPep-functionalised nanoparticles decreased as the grafting density of FluPep ligand increased from 0.03% to 5% (both mol/mol), with IC50 values down to about 10% of that of the corresponding free peptide. The data demonstrate that conjugation of FluPep to gold and silver nanoparticles enhances its antiviral potency; the antimicrobial activity of silver ions may enable the design of even more potent antimicrobial inhibitors, capable of targeting both influenza and bacterial co-infections.

Influenza and associated co-infections in critically ill immunosuppressed patients

BackgroundIt is unclear whether influenza infection and associated co-infection are associated with patient-important outcomes in critically ill immunocompromised patients with acute respiratory failure.MethodsPreplanned secondary analysis of EFRAIM, a prospective cohort study of 68 hospitals in 16 countries. We included 1611 patients aged 18 years or older with non-AIDS-related immunocompromise, who were admitted to the ICU with acute hypoxemic respiratory failure. The main exposure of interest was influenza infection status. The primary outcome of interest was all-cause hospital mortality, and secondary outcomes ICU length of stay (LOS) and 90-day mortality.ResultsInfluenza infection status was categorized into four groups: patients with influenza alone (n = 95, 5.8%), patients with influenza plus pulmonary co-infection (n = 58, 3.6%), patients with non-influenza pulmonary infection (n = 820, 50.9%), and patients without pulmonary infection (n = 638, 39.6%). Influenza infection status was associated with a requirement for intubation and with LOS in ICU (P < 0.001). Patients with influenza plus co-infection had the highest rates of intubation and longest ICU LOS. On crude analysis, influenza infection status was associated with ICU mortality (P < 0.001) but not hospital mortality (P = 0.09). Patients with influenza plus co-infection and patients with non-influenza infection alone had similar ICU mortality (41% and 37% respectively) that was higher than patients with influenza alone or those without infection (33% and 26% respectively). A propensity score-matched analysis did not show a difference in hospital mortality attributable to influenza infection (OR = 1.01, 95%CI 0.90–1.13, P = 0.85). Age, severity scores, ARDS, and performance status were all associated with ICU, hospital, and 90-day mortality.ConclusionsCategory of infectious etiology of respiratory failure (influenza, non-influenza, influenza plus co-infection, and non-infectious) was associated with ICU but not hospital mortality. In a propensity score-matched analysis, influenza infection was not associated with the primary outcome of hospital mortality. Overall, influenza infection alone may not be an independent risk factor for hospital mortality in immunosuppressed patients.

Pathogenesis of co-infections of influenza D virus and Mannheimia haemolytica in cattle

Bovine respiratory disease (BRD) is economically significant, and influenza D virus (IDV) is commonly identified in cattle with BRD. Mannheimia haemolytica (MHA) is an opportunistic bacterial contributor to BRD; surveillance data suggest that MHA and IDV co-infection occurs in cattle. The objective of this study was to evaluate the synergistic pathogenesis in cattle co-infected with IDV and MHA. Sixteen dairy calves were randomly assigned to four groups of four calves. The IDV + MHA + group received D/bovine/C00046 N/Mississippi/2014 (D/46 N) intranasally at 0 days post-inoculation (DPI) and Mannheimia haemolytica D153 (MHA D153) intratracheally at 5 DPI. The IDV + MHA- group received only D/46 N at 0 DPI; the IDV-MHA + group received only MHA D153 at 5 DPI; and the IDV-MHA- group received neither agent. Clinical scores were calculated twice daily. At 10 DPI, IDV + MHA+, IDV-MHA+, and IDV-MHA- calves were euthanized and evaluated for pathologic lesions. The IDV + groups seroconverted to IDV by 10 DPI. Clinical scores were higher in IDV + groups than IDV- groups on 2–5 DPI (p = 0.001). After MHA challenge on 5 DPI, clinical scores (6–10 DPI) were slightly lower in IDV+MHA+ group than IDV-MHA+ group (p < 0.05) but not significantly different between MHA+ groups and MHA- groups. The average gross pathology score was higher for IDV-MHA+ group than groups IDV-MHA- and IDV+MHA+; however, no significant differences were identified among groups. Under the conditions of this study, infection with IDV before MHA enhance neither clinical disease nor lung pathology, relative to calves infected with MHA alone.

The Impact of Influenza and Tuberculosis Interaction on Mortality Among Individuals Aged ≥15 Years Hospitalized With Severe Respiratory Illness in South Africa, 2010-2016.

BackgroundData on the prevalence and impact of influenza–tuberculosis coinfection on clinical outcomes from high–HIV and –tuberculosis burden settings are limited. We explored the impact of influenza and tuberculosis coinfection on mortality among hospitalized adults with lower respiratory tract infection (LRTI).MethodsWe enrolled patients aged ≥15 years admitted with physician-diagnosed LRTI or suspected tuberculosis at 2 hospitals in South Africa from 2010 to 2016. Combined nasopharyngeal and oropharyngeal swabs were tested for influenza and 8 other respiratory viruses. Tuberculosis testing of sputum included smear microscopy, culture, and/or Xpert MTB/Rif.ResultsAmong 6228 enrolled individuals, 4253 (68%) were tested for both influenza and tuberculosis. Of these, the detection rate was 6% (239/4253) for influenza, 26% (1092/4253) for tuberculosis, and 77% (3113/4053) for HIV. One percent (42/4253) tested positive for both influenza and tuberculosis. On multivariable analysis, among tuberculosis-positive patients, factors independently associated with death were age group ≥65 years compared with 15–24 years (adjusted odds ratio [aOR], 3.6; 95% confidence interval [CI], 1.2–11.0) and influenza coinfection (aOR, 2.3; 95% CI, 1.02–5.2). Among influenza-positive patients, laboratory-confirmed tuberculosis was associated with an increased risk of death (aOR, 4.5; 95% CI, 1.5–13.3). Coinfection with other respiratory viruses was not associated with increased mortality in patients positive for tuberculosis (OR, 0.7; 95% CI, 0.4–1.1) or influenza (OR, 1.6; 95% CI, 0.4–5.6).ConclusionsTuberculosis coinfection is associated with increased mortality in individuals with influenza, and influenza coinfection is associated with increased mortality in individuals with tuberculosis. These data may inform prioritization of influenza vaccines or antivirals for tuberculosis patients and inform tuberculosis testing guidelines for patients with influenza.

Changes in Mycobacterium tuberculosis-Specific Immunity With Influenza co-infection at Time of TB Diagnosis.

Background: Prior Influenza A viral (IAV) infection has been shown to increase susceptibility to tuberculosis (TB) and TB has also been shown to be a primary cause of death during pandemics, including the Spanish Influenza outbreak of 1918–1919. The majority of data has been obtained from mouse models, thus the aim of this study was to determine the impact of Flu co-infection on host immunity and disease severity in TB patients at diagnosis.Methods: Sputum from 282 patients with active TB were analyzed for presence of FluA/FluB RNA at presentation using multiplex PCR. Sputum RNA was also analyzed for Mycobacterium tuberculosis (Mtb) load using 16S RNA amplification. Supernatants from digested sputum and Mtb antigen-stimulated whole blood were analyzed using multiplex cytokine arrays and PBMC were analyzed for cytokine production from CD4+ T, CD8+ T and Mucosal Associated Invariant T cells (MAITs).Results: 12 (4.3%) of TB patients were found to have FluA or FluB viral RNA present in their sputum at the time of TB diagnosis. The TB/Flu co-infected patients had a significantly higher bacterial load compared to those with TB mono-infection (p = 0.0026). They had lower levels of IL17A in ex vivo sputum (p = 0.0275) and higher MCP-1 (CCL2) levels in the blood following PPD stimulation (p = 0.0267). TB/Flu co-infected subjects had significantly higher IFN-γ+IL-17+CD4+ and IFN-γ+IL-17-CD8+ cells compared to TB mono-infected subjects.Conclusions: These data show that Flu co-infection at time of TB diagnosis is associated with a higher bacterial load and differential cellular and soluble profiles. These findings show for the first time the impact of TB/Flu co-infection in a human cohort and support the potential benefit of Flu vaccination in TB-endemic settings.

Comparison of clinical severity between single- and coinfections of respiratory syncytial virus and influenza virus with common respiratory viruses

Purpose: Multiple virus infections may affect clinical severity. We investigated the effect of coinfection of respiratory syncytial virus (RSV) and influenza virus with other respiratory viruses on clinical severity. Methods: Data from 634 samples of a single tertiary hospital between September 2014 and April 2015 were analyzed for clinical characteristics (fever duration and O2 need, steroid use, and ICU care) between single infection and coinfection of RSV (n=290) and influenza virus (n=74) with 16 common respiratory viruses from hospitalized children. Results: The RSV coinfection group (n=109) (3.1±2.7 days) showed significantly longer fever duration than the RSV single infection group (n=181) (2.6±2.6 days) (P=0.04), while there was no difference in O2 need, steroid use or ICU care in the 2 groups. The influ enza coinfection group (n=38) showed significantly higher O2 need than the influenza single infection group (n=36) (21.1% vs. 5.6%, P=0.05), while there was no difference in fever duration between the 2 groups. Conclusion: The results indicate that RSV and Influenza coinfections can increase clinical severity and that the severity may be influ enced by the nature of coinfecting viruses. (Allergy Asthma Respir Dis 2019;7:86-91)

Studies on pathogenicity of local Newcastle disease genotype VII and Avian influenza H9N2 isolates to commercial vaccinated male layer chickens.

This study was carried out to compare pathogenicity of single and co-infection of Newcastle disease virus (NDV) genotype VIIj and Avian Influenza (AI) H9N2 virus in commercial male layer chicken vaccinated with live ND (Hitchner B1, La Sota) vaccines from different commercial producers in two vaccination schemes. NDV haemaglutination inhibition (HI (log2) mean titers in group received vaccines 1 (4.8 ± 0.8, 2.4 ± 1.2 and 3.9 ± 0.5) were lower than group given vaccine 2 (4.5 ± 1.2, 3.6 ± 1.1 and 4.0 ± 0.4) at 14, 21 and 29 days of age, respectively. Chicken group received ND vaccine 2 and inactivated H9 showed relatively higher HI titres (5.0 ± 1.5, 3.5 ± 1.4 and 4.5 ± 1.3). HI titres against H9N2 in group given H9N2 inactivated vaccine are 3.7 ± 1.6, 2.5 ± 1.1 and 5.1 ± 1.3 at 14, 21 and 29 days, respectively. Challenge with Newcastle disease virus (NDV) genotype VIIj at 33 days of age resulted in 100% mortality with severe signs as well as in non-vaccinated control sub-group challenged and 100% mortalities. Sub-groups (2a, 3a and 4a) vaccinated with ND vaccine 1, ND vaccine 2 and ND vaccine 2+ H9N2 showed signs of depression, off food and moderate respiratory signs with protection rates is 70, 70 and 75%, respectively. Control group challenged with H9N2 showed general signs with mild respiratory signs and 10% mortalities while, sub-groups given ND vaccine 2+ H9N2 and challenged with H9N2 showed 100% survival. Chicken sub-groups vaccinated with ND vaccine 1, ND vaccine 2 or ND vaccine 2+ H9N2 and challenged with NDV+ H9N2 (co-infection) showed signs form the 3rd s post infection (dpi) with moderate respiratory signs and protection rate of 50, 70 and 70%, respectively. Post-mortem lesions in Velogenic NDV (vNDV) challenged birds were septicemia, intestinal and respiratory lesion, while those challenged with both NDV and H9N2 showed more prominent lesions. The vaccinated groups showed unsatisfactory protection rates (50- 75%). Vaccine 2 showed higher protection and HI titers than vaccine 1. Simultaneous chicken challenge with H9N2 and vNDV pointed out that co-infection increased severity of clinical signs, mortality and gross lesions. Histological changes were reported in lung, intestine, and spleen of challenged non-vaccinated and vaccinated groups. The severity of tissue alteration was remarkably high in the non-vaccinated group and slightly mild tissue alteration in the vaccinated group. The histological changes ranged from severe congestion in blood vessels in tested organ with lymphoid depletion in spleen and hyperplasia of mucosal-associated lymphoid tissue in the intestine, with partial limited tissue change in the challenged vaccinated group. The local NDV strain genotype VIIj is highly pathogenic to male layer commercial chickens and the inoculation of NDV with H9N2 at the same time didn›t increase its severity. Also, it was notable that commercial Hitchner B1 and La Sota vaccines conferred partial protection for experimentally used chickens against challenge this ND field isolate.

Isolation and Identification of H9N2 influenza and Newcastle disease viruses co-infections in chicken

Co-infections with Newcastle disease (ND) and avian influenza (AI) highly pathogenic viruses causes high mortality and high economic losses. In this study, 322 samples were collected from 50 chicken flocks suffering from respiratory symptoms, severe drop in egg production and mortalities from December, 2013 to December, 2014. Real time polymerase chain reaction (RT-PCR) was performed to detect the M protein of H9 gene of AI and F gene of velogenic ND virus (vNDV) co-infection. H9 PCR was 20 and 34 in cloacal and pharyngeal swabs with total percentage of 6.2 % and 10.5%, respectively. The H9 sequences showed low pathogenic RSSR/GLF motif. The phylogenetic tree showed that H9 sequences belong to the G1 lineage which clustered with 2015 -2016 Egyptian H9N2. Partial sequences of the Fusion gene revealed that the isolated NDV isolates belong to class II genotype VIIj. The cleavage site of the F protein showed the presence of a polybasic amino acid motif (112RRQKRF117) suggesting that our two isolates were vNDV strain. The molecularly identified H9 (1 isolate) and NDV Genotype VII (2 isolates) were named AI/CHICKEN/EGYPT/48Ob/NRC-CU/2014(H9), NDV/CHICKEN/EGYPT/48Ob/NRC-CU/2014, and NDV/CHICKEN/EGYPT/ 66Oc/NRC-CU/2014, and nucleotide sequences were submitted to GenBank and given accession numbers MG966504, MG966505, and MG966506, respectively. Conclusion: Natural mixed infections with AIV H9N2 and virulent NDV genotype VIIj viruses were detected in chicken flocks suffering from respiratory symptoms and mortalities in Egypt.

Modeling the within-host co-infection of influenza A virus and pneumococcus

In this paper a nonlinear mathematical model for a within-host co-infection of influenza A virus and pneumococcus is investigated. Conditions that explain the relations amid RIP and its relationship to the global asymptotic stability of the infection-free steady state are discussed. A graph-theoretic method shows that, the unique endemic steady state is globally asymptotically stable. The sensitivity analysis show that, the pathogen fitness for pneumococcus and influenza A virus are most sensitive to maximum number of bacteria an alveolar macrophage can catch, phagocytosis rate, number of infectious IAV and pneumococcus particles liberated from lysis of infected cells and infection rates of influenza A virus and pneumococcal. Numerical results of the model show that, there exists a biologically important steady state where the two infectious pathogens of unequal strength co-exist and replace each other in the epithelial cell population (with pneumococcus leading) when the pathogen fitness for each infection exceeds unity, and we find that this endemic steady state is globally asymptotically stable. Further, the impact of influenza A virus on pneumococcus and vice-visa leads to a bifurcation state.

Immunogenicity and protective efficacy of monovalent PCVs containing 22F and 33F polysaccharides in mouse models of colonization and co-infection

BackgroundIn the current transmission, we studied the immunogenicity and protective efficacy of serotypes 22F and 33F in the prevention of colonization and of invasive Streptococcus pneumoniae (Spn) pathogenesis during an influenza co-infection. Serotypes 22F and 33F are emerging Spn serotypes, which are not part of currently administered pneumococcal conjugate vaccine formulations (PCVs). Spn serotype 6A is an ingredient in the currently administered PCV13 vaccine and was therefore included in the study as a control. MethodsAdult (six weeks) and infant (two weeks) C57BL/6 mice were intranasally infected in the nasopharynx (NP) with Spn serotypes 22F, 33F, or 6A. Influenza A H1N1 A/Puerto Rico/8/193 virus (PR8) was introduced one day after the NP Spn colonization. In an immunization challenge study, mice were vaccinated with monovalent 22F, 33F, or 6A polysaccharide conjugated to the CRM197 antigen. The immunized mice were colonized or co-infected to study the vaccines efficacy. ResultsAll three Spn serotypes established colonization in adult and infant mice. The co-infected mice showed an increase in Spn NP density. Invasive Spn infection (bacteremia) was observed following the co-infection with serotypes 22F and 6A but not 33F in adult mice, whereas infant mice developed bacteremia following co-infection with all three Spn serotypes. The vaccinations led to robust serum antibody responses to capsular polysaccharides 22F, 6A, and less for 33F. The vaccinations resulted in reductions of Spn NP colonization density for all three serotypes, prevention of bacteremia, and increased survival with Spn serotypes 22F and 6A. Passive transfer of antisera was associated with a reduction of Spn colonization densities in infant mice. ConclusionVaccinations with monovalent 22F, 33F, or 6A formulations protect against Spn colonization, and the efficacy of the 22F vaccination was comparable to the 6A vaccination in preventing an invasive Spn bacterial infection during an influenza co-infection.

Host-pathogen kinetics during influenza infection and coinfection: insights from predictive modeling.

SummaryInfluenza virus infections are a leading cause of morbidity and mortality worldwide. This is due in part to the continual emergence of new viral variants and to synergistic interactions with other viruses and bacteria. There is a lack of understanding about how host responses work to control the infection and how other pathogens capitalize on the altered immune state. The complexity of multi‐pathogen infections makes dissecting contributing mechanisms, which may be non‐linear and occur on different time scales, challenging. Fortunately, mathematical models have been able to uncover infection control mechanisms, establish regulatory feedbacks, connect mechanisms across time scales, and determine the processes that dictate different disease outcomes. These models have tested existing hypotheses and generated new hypotheses, some of which have been subsequently tested and validated in the laboratory. They have been particularly a key in studying influenza‐bacteria coinfections and will be undoubtedly be useful in examining the interplay between influenza virus and other viruses. Here, I review recent advances in modeling influenza‐related infections, the novel biological insight that has been gained through modeling, the importance of model‐driven experimental design, and future directions of the field.

Prolonged cell survival may contribute to the cytokine storm observed during the coinfection of influenza A virus (IAV) and Streptococcus pneumoniae.

Abstract Coinfection with influenza A virus (IAV) and Streptococcus pneumoniae is known to cause severe pneumonia. Numerous reports suggests an inappropriate immune response plays an important role in this disease. Many reports have examined signaling pathways responsible for the excessive immune response to coinfection, but the role for cell death in mediating inflammation during coinfection is not well understood. The inflammasome is a caspase-1 containing protein complex that activates interleukin-1β (IL-1β) and induces a pro-inflammatory form of cell death termed pyroptosis. We have discovered enhanced IL-1β levels during coinfection of macrophages with IAV and S. pneumoniae. Furthermore, inflammatory macrophages/monocytes, but not alveolar macrophages, are the major cell type producing IL-1β in the lung. However, this is not due to increased inflammasome activation. Intriguingly, coinfected macrophages are less prone to cell death than those singly infected with S. pneumoniae. Thus, we have elucidated a mechanism whereby prolonged cell survival may contribute to the cytokine storm observed during coinfection.

Mechanisms Regulating IL-1β Mediated Inflammation during Secondary Bacterial Pneumonia

Abstract Viral bacterial coinfections are known to cause severe pneumonia due to enhanced pathogen growth and excessive or altered immune responses. Despite knowing the overall causes for disease severity, current treatments fail to improve disease in many patients. Thus, an improved understanding of the specific immune pathways involved is needed to improve therapeutic treatment design. Interlukine-1β (IL-1β) is an important immune signaling cytokine responsible for inflammation. It exists as an inactive precursor that can be activated by caspase-1 containing inflammasomes. We found that coinfection of Influenza A virus and Streptococcus pneumoniae results in inflammasome activation mainly through the NOD-like receptor protein NLRP3. IL-1β levels are synergistically enhanced during coinfection, but not overall inflammasome activation. Instead, enhanced activation of the transcription factor NF-κB results in increased production of pro-IL-1β, which is subsequently processed into its active form by the inflammasome. In vivo, we discovered that IL-1β regulates lung pathology, and mice treated with a combination of antibiotics and IL-1β neutralizing antibodies have improved weight loss and mortality compared to either treatment individually.

IL-1 Signaling Prevents Alveolar Macrophage Depletion during Influenza and Streptococcus pneumoniae Coinfection.

Influenza and bacterial coinfection is a significant cause of hospitalization and death in humans during influenza epidemics and pandemics. However, the fundamental protective and pathogenic mechanisms involved in this complex virus-host-bacterium interaction remain incompletely understood. In this study, we have developed mild to lethal influenza and Streptococcus pneumoniae coinfection models for comparative analyses of disease pathogenesis. Specifically, wild-type and IL-1R type 1-deficient (Il1r1-/- ) mice were infected with influenza virus and then superchallenged with noninvasive S. pneumoniae serotype 14 (Spn14) or S. pneumoniae serotype 19A (Spn19A). The coinfections were followed by comparative analyses of inflammatory responses and animal protection. We found that resident alveolar macrophages are efficient in the clearance of both pneumococcal serotypes in the absence of influenza infection; in contrast, they are essential for airway control of Spn14 infection but not Spn19A infection. In agreement, TNF-α and neutrophils play a compensatory protective role in secondary bacterial infection associated with Spn19A; however, the essential requirement for alveolar macrophage-mediated clearance significantly enhances the virulence of Spn14 during postinfluenza pneumococcal infection. Furthermore, we show that, although IL-1 signaling is not required for host defense against pneumococcal infection alone, it is essential for sustaining antibacterial immunity during postinfluenza pneumococcal infection, as evidenced by significantly aggravated bacterial burden and animal mortality in Il1r1-/- mice. Mechanistically, we show that through preventing alveolar macrophage depletion, inflammatory cytokine IL-1 signaling is critically involved in host resistance to influenza and pneumococcal coinfection.

Invasive pulmonary aspergillosis and influenza co-infection in immunocompetent hosts: case reports and review of the literature

Invasive pulmonary aspergillosis (IPA) is classically considered an illness of severely immunocompromised patients with limited host defenses. However, IPA has been reported in immunocompetent but critically ill patients. This report describes two fatal cases of pathologically confirmed IPA in patients with influenza in the intensive care unit. One patient had influenza B infection, whereas the other had influenza A H1N1. Both patients died despite broad-spectrum antimicrobials, mechanical ventilation, and vasopressor support. Microscopic and histologic postmortem examination confirmed IPA. Review of the English language and foreign literature indicates that galactomannan antigen testing and classic radiologic findings for IPA may not be reliable in immunocompetent patients. Respiratory cultures which grow Aspergillus species in critically ill patients, particularly those with underlying influenza infection, should not necessarily be disregarded as contaminants or colonizers. Further research is needed to better understand the immunological relationship between influenza and IPA for improved prevention and treatment of influenza and Aspergillus co-infections.

Digital gene expression analysis in mice lung with coinfection of influenza and streptococcus pneumoniae.

Influenza A virus (IAV) and Streptococcus pneumoniae (SP) are two major upper respiratory tract pathogens that can also cause infection in polarized bronchial epithelial cells to exacerbate disease in coinfected individuals which may result in significant morbidity. However, the underlying molecular mechanism is poorly understood. Here, we employed BALB/c ByJ mice inflected with SP, IAV, IAV followed by SP (IAV+SP) and PBS (Control) as models to survey the global gene expression using digital gene expression (DGE) profiling. We attempt to gain insights into the underlying genetic basis of this synergy at the expression level. Gene expression profiles were obtain using the Illimina/Hisseq sequencing technique, and further analyzed by enrichment analysis of Gene Ontology (GO) and Pathway function. The hematoxylin-eosin (HE) staining revealed different tissue changes in groups during which IAV+SP group showed the most severe cell apoptosis. Compared with Control, a total of 2731, 3221 and 3946 differentially expressed genes (DEGs) were detected in SP, IAV and IAV+SP respectively. Besides, sixty-two GO terms were identified by Gene Ontology functional enrichment analysis, such as cell killing, biological regulation, response to stimulus, signaling, biological adhesion, enzyme regulator activity, receptor regulator activity and translation regulator activity. Pathway significant enrichment analysis indicated the dysregulation of multiple pathways, including apoptosis pathway. Among these, five selected genes were further verified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). This study shows that infection with SP, IAV or IAV+SP induces apoptosis with different degrees which might provide insights into the molecular mechanisms to facilitate further research.

The persistence of multiple strains of avian influenza in live bird markets.

Multiple subtypes of avian influenza (AI) and novel reassortants are frequently isolated from live bird markets (LBMs). However, our understanding of the drivers of persistence of multiple AI subtypes is limited. We propose a stochastic model of AI transmission within an LBM that incorporates market size, turnover rate and the balance of direct versus environmental transmissibility. We investigate the relationship between these factors and the critical community size (CCS) for the persistence of single and multiple AI strains within an LBM. We fit different models of seeding from farms to two-strain surveillance data collected from Shantou, China. For a single strain and plausible estimates for continuous turnover rates and transmissibility, the CCS was approximately 11 800 birds, only a 4.2% increase in this estimate was needed to ensure persistence of the co-infecting strains (two strains in a single host). Precise values of CCS estimates were sensitive to changes in market turnover rate and duration of the latent period. Assuming a gradual daily sell rate of birds the estimated CCS was higher than when an instantaneous selling rate was assumed. We were able to reproduce prevalence dynamics similar to observations from a single market in China with infection seeded every 5–15 days, and a maximum non-seeding duration of 80 days. Our findings suggest that persistence of co-infections is more likely to be owing to sequential infection of single strains rather than ongoing transmission of both strains concurrently. In any given system for a fixed set of ecological and epidemiological conditions, there is an LBM size below which the risk of sustained co-circulation is low and which may suggest a clear policy opportunity to reduce the frequency of influenza co-infection in poultry.

Epidemiological Surveillance of Influenza Virus Matrix Gene in Pigs, in Lagos, Nigeria, 2015-2016

Abstract The co-infection of different influenza A virus enable viral gene re-assortments especially in pigs that serve as mixing vessel with the possibility of emergence of novel subtypes. Such re-assortants pose serious public health threat, as epitomised by the emergence of pandemic influenza in 2009. In Nigeria, there is mixture of animal species and highly populated densities that can increase the risk of influenza virus endemicity, genetic reshuffling and emergence of future pandemic influenza viruses. Thus, this study was aimed at determining influenza virus disease burden in pigs. This study was a cross sectional molecular surveillance of influenza virus. A total of 194 pig nasal samples from reported cases and randomly sampled were collected from pig farms in Ojo and Ikorodu in Lagos State between October, 2015 and April, 2016. The samples were investigated for the presence of influenza virus matrix gene by Reverse Transcriptase Polymerase Chain Reaction and detected by gel electrophoresis. P-values were calculated using Chi-square and Fisher’s exact tests. The result showed that 25 (12.9%) samples were positive for influenza A virus, out of which, 20 (80%) were samples from Ojo while 5 (20%) were samples from Ikorodu. Epidemiological parameters for the sampled locations, methods either as reported case or randomised, and sex compared were significant at 95% confidence interval. This study determined influenza viral burden in pigs with a molecular prevalence of 12.9% to influenza A. It further confirmed the sub-clinical and clinical circulation of Influenza A virus in pigs in Ojo and Ikorodu in Lagos. Therefore, the detection of influenza A virus in commercial pigs in Nigeria accentuates the importance of continuous surveillance and monitoring of the virus in order to prevent the advent of virulent strains that may spread to Pig-handlers and the community at large.