Time to respiratory viral infection stratified by a) T-reg%, adjusted for age, sex, frailty and CMV-reactive CD4+ T-cell%) and b) CMV-reactive CD4+ T-cell%, adjusted for age, sex, frailty and T-reg%.

<p>Time to respiratory viral infection stratified by a) T-reg%, adjusted for age, sex, frailty and CMV-reactive CD4+ T-cell%) and b) CMV-reactive CD4+ T-cell%, adjusted for age, sex, frailty and T-reg%.</p

Gating strategy for CMV-reactive T cells.

<p>PBMC were stimulated with pp65 peptides to identify CMV-reactive T-cells. As a negative control, PBMC were stimulated with DMSO. Subsequently, the T-cells were stained for surface markers and intracellular cytokines. To define the CMV-reactive T-cells, the flow data was gated on singlet lymphocytes (as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108481#pone-0108481-g001" target="_blank">Figures 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108481#pone-0108481-g002" target="_blank">2</a>) and subsequently gated on CD3+CD8+ cells and CD3+CD4+. The plots show intracellular cytokine staining results for a single patient. CMV-reactive T-cells were defined as IFN-γ+ TNF-α+.</p

Gating strategy for T-cell phenotypes.

<p>T cell phenotypes were defined using the flowDensity software package. Lymphocytes were first gated from non-margin events, and then singlets were gated. CD45RA thresholds were calculated based on singlet lymphocytes FMO. CD3+ cells were gated and then separated into CD4+CD8- and CD4-CD8+. Expression of CD57, CD28, CD45RA and CCR7 was analyzed on either CD4+CD8- or CD8-CD4+.</p

Immune Biomarkers Predictive of Respiratory Viral Infection in Elderly Nursing Home Residents

<div><p>Objective</p><p>To determine if immune phenotypes associated with immunosenescence predict risk of respiratory viral infection in elderly nursing home residents.</p><p>Methods</p><p>Residents ≥65 years from 32 nursing homes in 4 Canadian cities were enrolled in Fall 2009, 2010 and 2011, and followed for one influenza season. Following influenza vaccination, peripheral blood mononuclear cells (PBMCs) were obtained and analysed by flow cytometry for T-regs, CD4+ and CD8+ T-cell subsets (CCR7+CD45RA+, CCR7-CD45RA+ and CD28-CD57+) and CMV-reactive CD4+ and CD8+ T-cells. Nasopharyngeal swabs were obtained and tested for viruses in symptomatic residents. A Cox proportional hazards model adjusted for age, sex and frailty, determined the relationship between immune phenotypes and time to viral infection.</p><p>Results</p><p>1072 residents were enrolled; median age 86 years and 72% female. 269 swabs were obtained, 87 were positive for virus: influenza (24%), RSV (14%), coronavirus (32%), rhinovirus (17%), human metapneumovirus (9%) and parainfluenza (5%). In multivariable analysis, high T-reg% (HR 0.41, 95% CI 0.20–0.81) and high CMV-reactive CD4+ T-cell% (HR 1.69, 95% CI 1.03–2.78) were predictive of respiratory viral infection.</p><p>Conclusions</p><p>In elderly nursing home residents, high CMV-reactive CD4+ T-cells were associated with an increased risk and high T-regs were associated with a reduced risk of respiratory viral infection.</p></div

Respiratory viruses present in symptomatic elderly nursing home residents.

<p>*One patient had mixed influenza A and rhinovirus.</p><p>Respiratory viruses present in symptomatic elderly nursing home residents.</p

Baseline characteristics of the nursing home elderly.

<p>Baseline characteristics of the nursing home elderly.</p

Combined effect of age and allele phenotype on disease outcome using logistic regression analysis comparing asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND) outcome groups.

<p>Combined effect of age and allele phenotype on disease outcome using logistic regression analysis comparing asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND) outcome groups.</p

Pair-wise analysis of HLA Class I phenotype frequencies^* in asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND) groups of WNV⁺ subjects.

<p>*Phenotype frequencies >5% are listed.</p>!<p>n represents the number of subjects with a specific allele phenotype. Alleles in bold showed an uncorrected <i>P</i><0.05 followed by a corrected <i>Pc</i> (<i>P/Pc</i>).</p

Demographics of the BSRI and McMaster cohorts.

<p>Demographics of the BSRI and McMaster cohorts.</p

Pair-wise analysis of HLA Class II phenotype frequencies^* in asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND) groups of WNV⁺ subjects.

<p>*Phenotype frequencies >5% are listed.</p>!<p>n represents the number of subjects with a specific allele phenotype. Alleles in bold showed an uncorrected <i>P</i><0.05 followed by a corrected <i>Pc</i> (<i>P/Pc</i>).</p