Longitudinal analysis of the group A Streptococcus transcriptome in experimental pharyngitis in cynomolgus macaques

Abstract

Identification of the genetic events that contribute to host-pathogen interactions is important for understanding the natural history of infectious diseases and developing therapeutics. Transcriptome studies conducted on pathogens have been central to this goal in recent years. However, most of these investigations have focused on specific end points or disease phases, rather than analysis of the entire time course of infection. To gain a more complete understanding of how bacterial gene expression changes over time in a primate host, the transcriptome of group A Streptococcus (GAS) was analyzed during an 86-day infection protocol in 20 cynomolgus macaques with experimental pharyngitis. The study used 260 custom Affymetrix (Santa Clara, CA) chips, and data were confirmed by TaqMan analysis. Colonization, acute, and asymptomatic phases of disease were identified. Successful colonization and severe inflammation were significantly correlated with an early onset of superantigen gene expression. The differential expression of two-component regulators covR and spy0680 (M1 spy0874) was significantly associated with GAS colony-forming units, inflammation, and phases of disease. Prophage virulence gene expression and prophage induction occurred predominantly during high pathogen cell densities and acute inflammation. We discovered that temporal changes in the GAS transcriptome were integrally linked to the phase of clinical disease and host-defense response. Knowledge of the gene expression patterns characterizing each phase of pathogen-host interaction provides avenues for targeted investigation of proven and putative virulence factors and genes of unknown function and will assist vaccine research.

Susceptibility to severe streptococcal sepsis: use of a large set of isogenic mouse lines to study genetic and environmental factors

“…While nonhuman primates represent an alternative to study human GAS infections, 40,41 their use in immunogenetic population studies is expensive and impractical due to their slow breeding pattern and small progeny, high cost and ethical issues. Meanwhile, regular laboratory mice, which share B85% gene content with humans, 42 are not sensitive to invasive GAS infections 43,44 just as certain human populations are not good models for certain human diseases because of their genetic resistance.…”

Group A Streptococcus Activates Type I Interferon Production and MyD88-dependent Signaling without Involvement of TLR2, TLR4, and TLR9

“…The heterogeneity of GAS diseases arises in part from the high diversity of GAS-mediated host-pathogen interactions in which virulence factors, GAS genome composition, prophage DNA, and plasticity of the GAS transcriptome play key roles (2,(61)(62)(63)(64). A major factor influencing the severity of GAS infections is also the genetic inventory of the host.…”

Toward a Genome-Wide Systems Biology Analysis of Host-Pathogen Interactions in Group A Streptococcus

“…Initial studies used conventional spotted microarrays and focused on in vitro analysis, but more recently a custom Affymetrix high-density oligonucleotide array has been used for ex vivo and in vivo studies. 55,56 The result has been substantial new understanding about how GAS reacts to its environment and the mammalian host. Here we summarize key findings from several of these investigations.…”

“…Several expression microarray studies have examined GAS, and extensive new information has been obtained about the nature and extent of changes in the pathogen's transcriptome in response to various perturbations. 28,[51][52][53][54][55][56] This global approach to understanding pathogenesis was facilitated by the information obtained from GAS genome sequencing projects, as described above. Initial studies used conventional spotted microarrays and focused on in vitro analysis, but more recently a custom Affymetrix high-density oligonucleotide array has been used for ex vivo and in vivo studies.…”

“…To gain a more complete understanding of how bacterial gene expression in vivo changes throughout time, the transcriptome of our contemporary serotype M1 GAS strain was analyzed during an 86-day infection protocol in 20 cynomolgus macaques with experimental pharyngitis. 56 A key discovery was that the temporal pattern of GAS gene expression in pharyngitis is intimately linked to three distinct phases of infection. For example, successful colonization and severe inflammation were significantly correlated with superantigen gene expression.…”