Individual gene expression and personalised medicine in sepsis

The results of many clinical trials on new sepsis therapies have been disappointing. Most of these studies have not shown any significant survival benefit in the heterogeneous patient populations included. The PROWESS study of the administration of activated protein C was the notable exception,1Bernard GR Vincent JL Laterre PF et al.Efficacy and safety of recombinant human activated protein C for severe sepsis.N Engl J Med. 2001; 344: 699-709Crossref PubMed Scopus (5053) Google Scholar and even resulted in the commercialisation of the drug. That is, until another placebo-controlled trial was conducted, and the results turned out to be entirely negative.2Ranieri VM Thompson BT Barie PS et al.Drotrecogin alfa (activated) in adults with septic shock.N Engl J Med. 2012; 366: 2055-2064Crossref PubMed Scopus (942) Google Scholar Yet many experts (including me) believe that activated protein C can have beneficial effects in some patients,3Vincent JL The rise and fall of drotrecogin alfa (activated).Lancet Infect Dis. 2012; 12: 649-651Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar although identification of which patients could benefit is difficult in the absence of a reliable biomarker of sepsis. It might be possible to identify some genetic factors that could differentiate these patients,4Man M Close SL Shaw AD et al.Beyond single-marker analyses: mining whole genome scans for insights into treatment responses in severe sepsis.Pharmacogenomics J. 2013; 13: 218-226Crossref PubMed Scopus (36) Google Scholar but this discovery arrived too late for activated protein C. Most sepsis drugs, including those targeting tumour necrosis factor α or interleukin 1, were developed to suppress the pro-inflammatory response. One of the reasons for the lack of success with these agents might be the fact that immunosuppression occurs early in patients with sepsis,5Hotchkiss RS Monneret G Payen D Immunosuppression in sepsis: a novel understanding of the disorder and a new therapeutic approach.Lancet Infect Dis. 2013; 13: 260-268Summary Full Text Full Text PDF PubMed Scopus (948) Google Scholar so anti-inflammatory drugs will only be effective if given very early. Indeed, as an example, it has been known for many years that interleukin 10, a typical anti-inflammatory cytokine, is released very early in sepsis.6Marchant A Devière J Byl B De Groote D Vincent JL Goldman M Interleukin-10 production during septicaemia.Lancet. 1994; 343: 707-708Abstract PubMed Scopus (308) Google Scholar In The Lancet Respiratory Medicine, Emma Davenport and colleagues report novel findings about the immunological profile of patients with community-acquired pneumonia-related sepsis.7Davenport EE Burnham KL Radhakrishnan J et al.Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort study.Lancet Respir Med. 2016; (published online Feb 22.)http://dx.doi.org/10.1016/S2213-2600(16)00046-1Google Scholar The investigators studied leucocyte global gene expression in patients admitted to 29 UK intensive care units (ICUs). Their prospective discovery cohort consisted of 265 patients and they validated their findings in a replication cohort of 106 patients. Using a sophisticated genomic analysis, Davenport and colleagues identified transcriptional sepsis response signatures (SRS). A type 1 SRS profile characterised patients with an immunosuppressed phenotype, which included endotoxin tolerance, T cell exhaustion, and human leucocyte antigen (HLA) class II downregulation. This phenotype, which was found in 108 (41%) patients in the discovery cohort, was associated with a 14-day mortality that was at least twice as high as that in the other patients (22% vs 10%, hazard ratio 2·4, 95% CI 1·3–4·5, p=0·005). The investigators also propose a simplified predictive set of seven genes that enabled classification of SRS. The study methodology is sound and the information provided in this Article7Davenport EE Burnham KL Radhakrishnan J et al.Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort study.Lancet Respir Med. 2016; (published online Feb 22.)http://dx.doi.org/10.1016/S2213-2600(16)00046-1Google Scholar could have important implications. First, more than 40% of the patients with community-acquired pneumonia in the discovery cohort had this immunosuppressive signature, and these patients also had a much worse outcome compared with the others. These numbers might not be very surprising to experts in this field, but could represent a blow to those who believe that anti-inflammatory strategies are needed to treat sepsis. Second, the SRS profile was not related to the timing of sampling in relation to ICU admission. This result will challenge the simplistic view that an initial pro-inflammatory response is followed later by an anti-inflammatory response; the immunosuppressed pattern can actually occur very early. Third, patients with the immunosuppressed profile could not be identified by clinical assessment. This finding clearly shows the importance of additional tests to complement the clinical examination. Nature produces more complex effects than can be detected from clinical assessment alone. Wong and colleagues8Wong HR Cvijanovich NZ Anas N et al.Developing a clinically feasible personalized medicine approach to pediatric septic shock.Am J Respir Crit Care Med. 2015; 191: 309-315Crossref PubMed Scopus (176) Google Scholar have already shown that gene expression can be quite variable in children with septic shock, and might actually help to identify those who could benefit from—or be harmed by—corticosteroid administration. Pena and colleagues9Pena OM Hancock DG Lyle NH et al.An endotoxin tolerance signature predicts sepsis and organ dysfunction at initial clinical presentation.EBioMedicine. 2014; 1: 64-71Summary Full Text Full Text PDF Scopus (88) Google Scholar reported that an endotoxin tolerance signature was associated with the presence of sepsis and organ dysfunction. Finally, several possible immunostimulating interventions are being developed, including granulocyte macrophage colony-stimulating factor, interleukin 7, interleukin 15, interferon γ, or co-inhibitory molecular blockade (eg, anti-programmed cell death receptor-1).10Vincent JL Emerging therapies for the treatment of sepsis.Curr Opin Anaesthesiol. 2015; 28: 411-416Crossref PubMed Scopus (14) Google Scholar The proposed simplified gene profile7Davenport EE Burnham KL Radhakrishnan J et al.Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort study.Lancet Respir Med. 2016; (published online Feb 22.)http://dx.doi.org/10.1016/S2213-2600(16)00046-1Google Scholar could help to identify those patients who might benefit from such novel immunostimulating strategies. Gene expression profiling could have other implications, including more rapid diagnosis of infections. Scicluna and colleagues11Scicluna BP Klein Klouwenberg PM van Vught LA et al.A molecular biomarker to diagnose community-acquired pneumonia on intensive care unit admission.Am J Respir Crit Care Med. 2015; 192: 826-835Crossref PubMed Scopus (126) Google Scholar used blood microarray analysis to identify a 78-gene signature for community-acquired pneumonia. In their abstract, Davenport and colleagues conclude: “Our findings provide new insights into the pathogenesis of sepsis and create opportunities for a precision medicine approach”.7Davenport EE Burnham KL Radhakrishnan J et al.Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort study.Lancet Respir Med. 2016; (published online Feb 22.)http://dx.doi.org/10.1016/S2213-2600(16)00046-1Google Scholar However, precision medicine might be too strong a term in this context; it is typically used to refer to the precise molecular targeting of therapeutic strategies. Perhaps personalised medicine would be more appropriate (figure), although this is clearly not a new concept and one could argue that, as clinicians, we have always applied personalised medicine. Nevertheless, this approach is sometimes forgotten in the field of critical care medicine. All too often we have studied poorly characterised populations of patients grouped together as sepsis, acute respiratory distress syndrome, or even systemic inflammatory response syndrome, as if these entities were specific disease states, but they are not. Over the years, this one-size-fits-all approach has resulted in a multitude of negative randomised, controlled trials, especially in sepsis, with vast amounts of wasted effort and resources. One size cannot fit all. The results of the current study by Davenport and colleagues, and other similar studies that provide a way to characterise patients with sepsis, will pave the way for researchers and, ultimately, clinicians to be able to target therapeutic strategies more appropriately and effectively. This is certainly very good news. I declare no competing interests. Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort studyOur integrated genomics approach advances understanding of heterogeneity in sepsis by defining subgroups of patients with different immune response states and prognoses, as well as revealing the role of underlying genetic variation. Our findings provide new insights into the pathogenesis of sepsis and create opportunities for a precision medicine approach to enable targeted therapeutic intervention to improve sepsis outcomes. Full-Text PDF Open Access