Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection

One of the least understood aspects of the bacteriumStreptococcus pneumoniae(pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, shedding, and transmission during bacterial monoinfection. Using this model, we demonstrated that the level of bacterial shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized “index” pups to uncolonized “contact” pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of shedding. This model can be used to examine bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.

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Increased Nasopharyngeal Bacterial Titers and Local Inflammation Facilitate Transmission of Streptococcus pneumoniae

mBio ◽

10.1128/mbio.00255-12 ◽

2012 ◽

Vol 3 (5) ◽

Cited By ~ 48

Author(s):

Kirsty R. Short ◽

Patrick C. Reading ◽

Nancy Wang ◽

Dimitri A. Diavatopoulos ◽

Odilia L. Wijburg

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Influenza A ◽

Pneumococcal Disease ◽

Present Report ◽

Bacterial Load ◽

Disease Development ◽

Proinflammatory Response ◽

Content Type ◽

Infant Mouse

ABSTRACTThe transmission of the bacteriumStreptococcus pneumoniae(the pneumococcus) marks the first step toward disease development. To date, our ability to prevent pneumococcal transmission has been limited by our lack of understanding regarding the factors which influence the spread of this pathogen. We have previously developed an infant mouse model of pneumococcal transmission which was strictly dependent on influenza A virus (IAV) coinfection of both the experimentally colonized “index mice” and the naive cohoused “contact mice.” Here, we sought to use this model to further elucidate the factors which facilitateS. pneumoniaetransmission. In the present report, we demonstrate that increasing the nasopharyngeal load ofS. pneumoniaein the colonized index mice (via the depletion of neutrophils) and inducing a proinflammatory response in the naive cohoused contact mice (as demonstrated by cytokine production) facilitatesS. pneumoniaetransmission. Thus, these data provide the first insights into the factors that help mediate the spread ofS. pneumoniaethroughout the community.IMPORTANCEStreptococcus pneumoniae(the pneumococcus) is a major cause of worldwide morbidity and mortality and is a leading cause of death among children under the age of five years. Transmission ofS. pneumoniaemarks the first step toward disease development. Therefore, understanding the factors that influence the spread of pneumococci throughout the community plays an essential role in preventing pneumococcal disease. We previously developed the first reproducible infant mouse model for pneumococcal transmission and showed that coinfection with influenza virus facilitates the spread ofS. pneumoniae. Here, we show that increasing the bacterial load in the nasal cavity of colonized individuals as well as inducing an inflammatory response in naive “contact cases” facilitates the spread of pneumococci. Therefore, this study helps to identify the factors which must be inhibited in order to successfully prevent pneumococcal disease.

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Protection against Streptococcus pneumoniae Invasive Pathogenesis by a Protein-Based Vaccine Is Achieved by Suppression of Nasopharyngeal Bacterial Density during Influenza A Virus Coinfection

Infection and Immunity ◽

10.1128/iai.00530-16 ◽

2016 ◽

Vol 85 (2) ◽

Cited By ~ 12

Author(s):

M. Nadeem Khan ◽

Qingfu Xu ◽

Michael E. Pichichero

Keyword(s):

T Cells ◽

Streptococcus Pneumoniae ◽

Influenza A Virus ◽

Influenza A ◽

Passive Transfer ◽

Bacterial Density ◽

Content Type ◽

Adult Mice ◽

Significant Difference ◽

Colonization Density

ABSTRACTAn increase inStreptococcus pneumoniaenasopharynx (NP) colonization density during a viral coinfection initiates pathogenesis. To mimic naturalS. pneumoniaepathogenesis, we commensally colonized the NPs of adult C57BL/6 mice withS. pneumoniaeserotype (ST) 6A or 8 and then coinfected them with mouse-adapted H1N1 influenza A virus (PR/8/34).S. pneumoniaeestablished effective commensal colonization, and influenza virus coinfection causedS. pneumoniaeNP density to increase, resulting in bacteremia and mortality. We then studied histidine triad protein D (PhtD), anS. pneumoniaeadhesin vaccine candidate, for its ability to prevent invasiveS. pneumoniaedisease in adult and infant mice. In adult mice, the efficacy of PhtD vaccination was compared with that of PCV13. Vaccination with PCV13 led to a greater reduction ofS. pneumoniaeNP density (>2.5 log units) than PhtD vaccination (∼1-log-unit reduction). However, no significant difference was observed with regard to the prevention ofS. pneumoniaebacteremia, and there was no difference in mortality. Depletion of CD4+T cells in PhtD-vaccinated adult mice, but not PCV13-vaccinated mice, caused a loss of vaccine-induced protection. In infant mice, passive transfer of antisera or CD4+T cells from PhtD-vaccinated adult mice led to a nonsignificant reduction in NP colonization density, whereas passive transfer of antisera and CD4+T cells was needed to cause a significant reduction in NP colonization density. For the first time, these data show an outcome with regard to prevention of invasiveS. pneumoniaepathogenesis with a protein vaccine similar to that which occurs with a glycoconjugate vaccine despite a less robust reduction in NP bacterial density.

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Type I Interferon Signaling Is a Common Factor Driving Streptococcus pneumoniae and Influenza A Virus Shedding and Transmission

mBio ◽

10.1128/mbio.03589-20 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Tonia Zangari ◽

Mila B. Ortigoza ◽

Kristen L. Lokken-Toyli ◽

Jeffrey N. Weiser

Keyword(s):

Streptococcus Pneumoniae ◽

Respiratory Tract ◽

Influenza A Virus ◽

Influenza A ◽

Common Factor ◽

Type I ◽

Upper Respiratory Tract ◽

Content Type ◽

Infant Mouse ◽

Upper Respiratory

ABSTRACT The dynamics underlying respiratory contagion (the transmission of infectious agents from the airways) are poorly understood. We investigated host factors involved in the transmission of the leading respiratory pathogen Streptococcus pneumoniae. Using an infant mouse model, we examined whether S. pneumoniae triggers inflammatory pathways shared by influenza A virus (IAV) to promote nasal secretions and shedding from the upper respiratory tract to facilitate transit to new hosts. Here, we show that amplification of the type I interferon (IFN-I) response is a critical host factor in this process, as shedding and transmission by both IAV and S. pneumoniae were decreased in pups lacking the common IFN-I receptor (Ifnar1−/− mice). Additionally, providing exogenous recombinant IFN-I to S. pneumoniae-infected pups was sufficient to increase bacterial shedding. The expression of IFN-stimulated genes (ISGs) was upregulated in S. pneumoniae-infected wild-type (WT) but not Ifnar1−/− mice, including genes involved in mucin type O-glycan biosynthesis; this correlated with an increase in secretions in S. pneumoniae- and IAV-infected WT compared to Ifnar1−/− pups. S. pneumoniae stimulation of ISGs was largely dependent on its pore-forming toxin, pneumolysin, and coinfection with IAV and S. pneumoniae resulted in synergistic increases in ISG expression. We conclude that the induction of IFN-I signaling appears to be a common factor driving viral and bacterial respiratory contagion. IMPORTANCE Respiratory tract infections are a leading cause of childhood mortality and, globally, Streptococcus pneumoniae is the leading cause of mortality due to pneumonia. Transmission of S. pneumoniae primarily occurs through direct contact with respiratory secretions, although the host and bacterial factors underlying transmission are poorly understood. We examined transmission dynamics of S. pneumoniae in an infant mouse model and here show that S. pneumoniae colonization of the upper respiratory tract stimulates host inflammatory pathways commonly associated with viral infections. Amplification of this response was shown to be a critical host factor driving shedding and transmission of both S. pneumoniae and influenza A virus, with infection stimulating expression of a wide variety of genes, including those involved in the biosynthesis of mucin, a major component of respiratory secretions. Our findings suggest a mechanism facilitating S. pneumoniae contagion that is shared by viral infection.

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A novel pneumococcal surface protein K of nonencapsulated Streptococcus pneumoniae promotes transmission among littermates in an infant mouse model with influenza A virus co-infection

Infection and Immunity ◽

10.1128/iai.00622-21 ◽

2022 ◽

Author(s):

Hideki Sakatani ◽

Masamitsu Kono ◽

Denisa Nanushaj ◽

Daichi Murakami ◽

Saori Takeda ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Influenza A ◽

Capsular Polysaccharide ◽

Surface Protein ◽

Nasal Colonization ◽

Infant Mouse ◽

Key Factor ◽

Protective Strategy ◽

New Hosts

We established an infant mouse model for colonization and transmission by nonencapsulated Streptococcus pneumoniae (NESp) strains to gain important information about its virulence among children. Invasive pneumococcal diseases have decreased dramatically since the worldwide introduction of pneumococcal capsular polysaccharide vaccines. Increasing prevalence of non-vaccine serotypes including NESp has been highlighted as a challenge in treatment strategy, but the virulence of NESp is not well understood. Protective strategy against NESp colonization and transmission between children require particularly urgent evaluation. NESp lacks capsules, a major virulent factor of pneumococci, but can cause a variety of infections in children and older people. PspK, a specific surface protein of NESp, is a key factor in establishing nasal colonization. In our infant mouse model for colonization and transmission by NESp strains, NESp could establish stable nasal colonization at the same level as encapsulated serotype 6A in infant mice, and could be transmitted between littermates. Transmission was promoted by NESp surface virulence factor PspK and influenza virus co-infection. However, PspK-deletion mutants lost the ability to colonize and transmit to new hosts. Promotion of NESp transmission by influenza was due to increased susceptibility of the new hosts. PspK was a key factor not only in establishment of nasal colonization, but also in transmission to new hosts. PspK may be targeted as a new candidate vaccine for NESp infection in children.

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Influenza-Induced Inflammation Drives Pneumococcal Otitis Media

Infection and Immunity ◽

10.1128/iai.01278-12 ◽

2013 ◽

Vol 81 (3) ◽

pp. 645-652 ◽

Cited By ~ 43

Author(s):

Kirsty R. Short ◽

Patrick C. Reading ◽

Lorena E. Brown ◽

John Pedersen ◽

Brad Gilbertson ◽

...

Keyword(s):

Otitis Media ◽

Middle Ear ◽

Influenza A ◽

Pneumococcal Disease ◽

Influenza Viruses ◽

Dependent Manner ◽

Proinflammatory Response ◽

Content Type ◽

Infant Mouse ◽

Human Middle Ear

ABSTRACTInfluenza A virus (IAV) predisposes individuals to secondary infections with the bacteriumStreptococcus pneumoniae(the pneumococcus). Infections may manifest as pneumonia, sepsis, meningitis, or otitis media (OM). It remains controversial as to whether secondary pneumococcal disease is due to the induction of an aberrant immune response or IAV-induced immunosuppression. Moreover, as the majority of studies have been performed in the context of pneumococcal pneumonia, it remains unclear how far these findings can be extrapolated to other pneumococcal disease phenotypes such as OM. Here, we used an infant mouse model, human middle ear epithelial cells, and a series of reverse-engineered influenza viruses to investigate how IAV promotes bacterial OM. Our data suggest that the influenza virus HA facilitates disease by inducing a proinflammatory response in the middle ear cavity in a replication-dependent manner. Importantly, our findings suggest that it is the inflammatory response to IAV infection that mediates pneumococcal replication. This study thus provides the first evidence that inflammation drives pneumococcal replication in the middle ear cavity, which may have important implications for the treatment of pneumococcal OM.

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Two regulatory factors of Vibrio cholerae activating the mannose-sensitive haemagglutinin pilus expression is important for biofilm formation and colonization in mice

Microbiology ◽

10.1099/mic.0.001098 ◽

2021 ◽

Vol 167 (10) ◽

Author(s):

Mengting Shi ◽

Yue Zheng ◽

Xianghong Wang ◽

Zhengjia Wang ◽

Menghua Yang

Keyword(s):

Mouse Model ◽

Vibrio Cholerae ◽

Biofilm Formation ◽

Type Species ◽

Wild Type ◽

Expression Library ◽

Content Type ◽

Genomic Expression ◽

Infant Mouse ◽

Link Type

Vibrio cholerae the causative agent of cholera, uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host intestine, which is its preferred colonization site. Transcription of the mannose-sensitive haemagglutinin pilus (MSHA), which aids the persistence of V. cholerae in aquatic environments, but causes its clearance by host immune defenses, was found to be regulated by a yet unknown mechanism during the infection cycle of V. cholerae . In this study, genomic expression library screening revealed that two regulators, VC1371 and VcRfaH, are able to positively activate the transcription of MSHA operon. VC1371 is localized and active in the cell membrane. Deletion of vc1371 or VcrfaH genes in V. cholerae resulted in less MshA protein production and less efficiency of biofilm formation compared to that in the wild-type strain. An adult mouse model showed that the mutants with vc1371 or VcrfaH deletion colonized less efficiently than the wild-type; the VcrfaH deletion mutant showed less colonization efficiency in the infant mouse model. The findings strongly suggested that the two regulators, namely VC1371 and VcRfaH, which are involved in the regulation of MSHA expression, play an important role in V. cholerae biofilm formation and colonization in mice.

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Streptococcus pneumoniae Transmission Is Blocked by Type-Specific Immunity in an Infant Mouse Model

mBio ◽

10.1128/mbio.00188-17 ◽

2017 ◽

Vol 8 (2) ◽

Cited By ~ 13

Author(s):

Tonia Zangari ◽

Yang Wang ◽

Jeffrey N. Weiser

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Pneumococcal Conjugate Vaccine ◽

Herd Immunity ◽

Mechanistic Explanation ◽

Epidemiological Studies ◽

Contributing Factors ◽

Infant Mouse ◽

Major Benefit

ABSTRACT Epidemiological studies on Streptococcus pneumoniae show that rates of carriage are highest in early childhood and that the major benefit of the pneumococcal conjugate vaccine (PCV) is a reduction in the incidence of nasopharyngeal colonization through decreased transmission within a population. In this study, we sought to understand how anti- S. pneumoniae immunity affects nasal shedding of bacteria, the limiting step in experimental pneumococcal transmission. Using an infant mouse model, we examined the role of immunity (passed from mother to pup) on shedding and within-litter transmission of S. pneumoniae by pups infected at 4 days of life. Pups from both previously colonized immune and PCV-vaccinated mothers had higher levels of anti- S. pneumoniae IgG than pups from non-immune or non-vaccinated mothers and shed significantly fewer S. pneumoniae over the first 5 days of infection. By setting up cross-foster experiments, we demonstrated that maternal passage of antibody to pups either in utero or post-natally decreases S. pneumoniae shedding. Passive immunization experiments showed that type-specific antibody to capsular polysaccharide is sufficient to decrease shedding and that the agglutinating function of immunoglobulin is required for this effect. Finally, we established that anti-pneumococcal immunity and anti-PCV vaccination block host-to-host transmission of S. pneumoniae . Moreover, immunity in either the donor or recipient pups alone was sufficient to reduce rates of transmission, indicating that decreased shedding and protection from acquisition of colonization are both contributing factors. Our findings provide a mechanistic explanation for the reduced levels of S. pneumoniae transmission between hosts immune from prior exposure and among vaccinated children. IMPORTANCE Rates of carriage of the bacterial pathogen Streptococcus pneumoniae are highest among young children, and this is the target group for the pneumococcal conjugate vaccine (PCV). Epidemiological studies have suggested that a major benefit of the PCV is a reduction in host-to-host transmission, which also protects the non-vaccinated population (“herd immunity”). In this study, we examined the role of anti-pneumococcal immunity on nasal shedding and transmission of the pathogen using an infant mouse model. We found that shedding is decreased and transmission is blocked by anti-pneumococcal immunity and PCV vaccination. Additionally, transmission rates decreased if either the infected or contact pups were immune, indicating that reduced shedding and protection from the establishment of colonization are both contributing factors. Our study provides a mechanistic explanation for the herd immunity effect seen after the introduction of PCV and identifies potential points of intervention, which may have implications for future vaccine development.

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Antibodies to Conserved Pneumococcal Antigens Correlate with, but Are Not Required for, Protection against Pneumococcal Colonization Induced by Prior Exposure in a Mouse Model

Infection and Immunity ◽

10.1128/iai.73.10.7043-7046.2005 ◽

2005 ◽

Vol 73 (10) ◽

pp. 7043-7046 ◽

Cited By ~ 50

Author(s):

Krzysztof Trzciński ◽

Claudette Thompson ◽

Richard Malley ◽

Marc Lipsitch

Keyword(s):

T Cells ◽

Streptococcus Pneumoniae ◽

Mouse Model ◽

Prior Exposure ◽

Correlates Of Protection ◽

Pneumococcal Colonization

ABSTRACT In mice following intranasal exposure to Streptococcus pneumoniae, protection against pneumococcal colonization was independent of antibody but dependent on CD4+ T cells. Nonetheless, concentrations of antibodies to three conserved pneumococcal antigens correlated with protection against colonization. Concentrations of antibodies to conserved pneumococcal antigens may be correlates of protection without being effectors of protection.

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Dynamic Changes in the Streptococcus pneumoniae Transcriptome during Transition from Biofilm Formation to Invasive Disease upon Influenza A Virus Infection

Infection and Immunity ◽

10.1128/iai.02225-14 ◽

2014 ◽

Vol 82 (11) ◽

pp. 4607-4619 ◽

Cited By ~ 55

Author(s):

Melinda M. Pettigrew ◽

Laura R. Marks ◽

Yong Kong ◽

Janneane F. Gent ◽

Hazeline Roche-Hakansson ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Influenza A Virus ◽

Influenza A ◽

Lactate Production ◽

Invasive Disease ◽

Content Type ◽

Induced Changes ◽

Upregulated Genes

ABSTRACTStreptococcus pneumoniaeis a leading cause of infectious disease globally. Nasopharyngeal colonization occurs in biofilms and precedes infection. Prior studies have indicated that biofilm-derived pneumococci are avirulent. However, influenza A virus (IAV) infection releases virulent pneumococci from biofilmsin vitroandin vivo. Triggers of dispersal include IAV-induced changes in the nasopharynx, such as increased temperature (fever) and extracellular ATP (tissue damage). We used whole-transcriptome shotgun sequencing (RNA-seq) to compare theS. pneumoniaetranscriptome in biofilms, bacteria dispersed from biofilms after exposure to IAV, febrile-range temperature, or ATP, and planktonic cells grown at 37°C. Compared with biofilm bacteria, actively dispersedS. pneumoniae, which were more virulent in invasive disease, upregulated genes involved in carbohydrate metabolism. Enzymatic assays for ATP and lactate production confirmed that dispersed pneumococci exhibited increased metabolism compared to those in biofilms. Dispersed pneumococci also upregulated genes associated with production of bacteriocins and downregulated colonization-associated genes related to competence, fratricide, and the transparent colony phenotype. IAV had the largest impact on the pneumococcal transcriptome. Similar transcriptional differences were also observed when actively dispersed bacteria were compared with avirulent planktonic bacteria. Our data demonstrate complex changes in the pneumococcal transcriptome in response to IAV-induced changes in the environment. Our data suggest that disease is caused by pneumococci that are primed to move to tissue sites with altered nutrient availability and to protect themselves from the nasopharyngeal microflora and host immune response. These data help explain pneumococcal virulence after IAV infection and have important implications for studies ofS. pneumoniaepathogenesis.

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Influenza A Virus Infection Predisposes Hosts to Secondary Infection with Different Streptococcus pneumoniae Serotypes with Similar Outcome but Serotype-Specific Manifestation

Infection and Immunity ◽

10.1128/iai.00422-16 ◽

2016 ◽

Vol 84 (12) ◽

pp. 3445-3457 ◽

Cited By ~ 29

Author(s):

Niharika Sharma-Chawla ◽

Vicky Sender ◽

Olivia Kershaw ◽

Achim D. Gruber ◽

Julia Volckmar ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Influenza A Virus ◽

Bacterial Strain ◽

Influenza A ◽

Host Susceptibility ◽

Dependent Manner ◽

Content Type ◽

Systemic Dissemination ◽

Tract Infections ◽

Strain Dependent

Influenza A virus (IAV) and Streptococcus pneumoniae are major causes of respiratory tract infections, particularly during coinfection. The synergism between these two pathogens is characterized by a complex network of dysregulated immune responses, some of which last until recovery following IAV infection. Despite the high serotype diversity of S. pneumoniae and the serotype replacement observed since the introduction of conjugate vaccines, little is known about pneumococcal strain dependency in the enhanced susceptibility to severe secondary S. pneumoniae infection following IAV infection. Thus, we studied how preinfection with IAV alters host susceptibility to different S. pneumoniae strains with various degrees of invasiveness using a highly invasive serotype 4 strain, an invasive serotype 7F strain, and a carrier serotype 19F strain. A murine model of pneumococcal coinfection during the acute phase of IAV infection showed a significantly increased degree of pneumonia and mortality for all tested pneumococcal strains at otherwise sublethal doses. The incidence and kinetics of systemic dissemination, however, remained bacterial strain dependent. Furthermore, we observed strain-specific alterations in the pulmonary levels of alveolar macrophages, neutrophils, and inflammatory mediators ultimately affecting immunopathology. During the recovery phase following IAV infection, bacterial growth in the lungs and systemic dissemination were enhanced in a strain-dependent manner. Altogether, this study shows that acute IAV infection predisposes the host to lethal S. pneumoniae infection irrespective of the pneumococcal serotype, while the long-lasting synergism between IAV and S. pneumoniae is bacterial strain dependent. These results hold implications for developing tailored therapeutic treatment regimens for dual infections during future IAV outbreaks.

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