New perspectives on immunomodulatory therapy for bacteraemia and sepsis

Systemic immune dysregulation is generally acknowledged to be the fundamental molecular mechanism that underlies the pathophysiology of severe sepsis and septic shock. In the presence of a systemic infection, microbial pathogens and their soluble mediators induce generalised immune activation and coagulation activation, leading to severe sepsis and septic shock. For decades, immune-based therapies have been devised with the specific intent of inhibiting the pro-inflammatory events that are thought to precipitate the septic process. Despite a clear therapeutic rationale based upon the available experimental evidence, anti-inflammatory therapies targeting the innate or acquired immune response have largely been unsuccessful in clinical trials of sepsis. Compelling evidence now exists that a prolonged state of sepsis-induced immune suppression follows the initial period of stabilisation and resuscitation in many critically ill patients. Sepsis-related immune suppression is evidenced by histological findings of markedly enhanced lymphocytic and monocytic apoptosis, poor response to neoantigens and recall antigens, and increased incidence of infections by opportunistic pathogens. Candidiasis, cytomegalovirus activation and secondary infections by relatively avirulent bacterial pathogens such as Stenotrophomonas and Acinetobacter spp. are commonplace in septic patients during prolonged Intensive Care Unit stays. Immunological tools to detect sepsis-induced immunosuppression are now available, and novel immunoadjuvants are in development to re-establish immune competence in sepsis patients. The intelligent use of immunomodulatory agents in sepsis will necessitate a personalised medicine approach to treat each patient at the appropriate time and with the optimal therapy.