Bacterial toxins as pathogen weapons against phagocytes

Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed. This work was supported by FEDER funds through Programa Operational Factores de Competitividade - COMPETE and by national funds through FCT - Fundacao para a Ciencia e a Tecnologia (project PTDC/BIA-MIC/3463/2012 FCOMP-01-0124-FEDER-028364; to AV). Research in the groups of Molecular Microbiology and Fish Immunology and Vaccinology is supported by national funds through FCT Fundacao para Ciencia e a Tecnologia/MEC - Ministerio da Educacao e Ciencia and co-funded by FEDER within the partnership agreement: PT2020 related with the research unit number 4293. The Group of Molecular Microbiology also receives support from a Research Grant 2014 by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) (to SS) and the PT2020 research project Infect-ERA/0001/2013 PROANTILIS. AdV received the FCT fellowship SFRH/BPD/95777/2013 by national funds through FCT - Fundacao para a Ciencia e a Tecnologia/MEC - Ministerio da Educacao e Ciencia and co-funded by QREN and POPH (Programa Operational Potential Humano). SS is supported by FCT-Investigator program.