Model for the establishment of longer-term respiratory tract colonization by GAS.

<p>Following adhesion of bacterial cells to epithelium, and initial transient colonization, there is depletion of bacterial numbers due to host immune responses. These include innate factors, such as anti-microbial peptides and agglutinins, neutrophils and macrophages. A small number of bacterial cells successfully evade these responses, perhaps associated with up-regulation of AspA or transient internalization by epithelial cells. Expression of AspA brings into play the anti-phagocytic properties and biofilm-enhancing activities of AspA, leading to prolonged colonization of the mucosa. Asterisks denote temporal role for AspA.</p

Adherence levels of MGAS10270 or MGAS6180 and corresponding Δ<i>aspA</i> mutants to A549 lung epithelial cells (pneumocytes) or Detroit 562 pharyngeal epithelial cells.

<p>Adherence is expressed as percentage of input cells (10⁶ cfu) attached. Data are means ± SEM of 3 experiments repeated in triplicate. * = <i>P</i><0.001 using 2 tail student T-test.</p

Bacterial numbers (cfu) within nasopharynx or lungs at various times following intranasal challenge of mice (1×10⁸ cells) with <i>S. pyogenes</i> MGAS10270 (•) or MGAS10270 <i>aspA</i> (Δ) (UB2115).

<p>Data are means ± SEM of 3 experiments.</p

Numbers of bacteria (cfu) killed by macrophages (J774.2 cell line) following 1 h co-incubation with <i>S. pyogenes</i> MGAS6180 or MGAS10270 wild type and <i>aspA</i> mutants (input 5×10³ cfu, 5×10⁴ macrophages).

<p>Percentage killing was calculated from cfu remaining compared with control samples without macrophages. Data are means ± SEM of 3 experiments repeated in triplicate. * = <i>P</i><0.001 using 2 tail student T-test.</p

Percentage killing of <i>L. lactis</i> MG1363 wild type, and AspA or SspB expressing strains, by (A) J774.2 macrophages or (B) HL60 neutrophils following 1 h co-incubation compared with controls.

<p>Percentage killing was calculated from cfu remaining compared with control samples without macrophages or neutrophils. Data are means ± SEM of 3 experiments repeated in triplicate. * = P<0.05 using 2 tail student T-test.</p

Percentage killing of <i>S. pyogenes</i> MGAS6180 or MGAS10270 wild type and <i>aspA</i> mutants by HL60 neutrophils following 1 h co-incubation as compared with controls.

<p>Percentage killing was calculated from cfu remaining compared with control samples without neutrophils (input 10⁴ cfu, 10⁵ neutrophils). Data are means ± SEM of 5 experiments repeated in triplicate. * = <i>P</i><0.05 using 2 tail student T-test.</p