Intracellular bacteria such as Anaplasma spp. and Mycobacterium spp. pose a risk to human and animal populations worldwide. The main function of immune response cells is to eliminate invading pathogens. However, pathogens can deregulate host cell function and turn defense cells into suitable hosts. Intracellular bacterial have a smaller genome, compared to the host cell, thus requiring efficient mechanisms for survival and persistence within the host by inducing sustained changes in cell function and immune response. Bacterial epigenetic regulation of host cell gene transcription appears to be a general mechanism that enhances pathogen survival while altering host cell function and facilitating infection. Anaplasma phagocytophilum leads to modified host cell gene transcription and phenotype by epigenetically altering host chromatin. Mycobacterial infection of human cells also results in host gene silencing using a mechanism that involves HDAC complex formation and histone deacetylation. Membrane proteins are essential for cell invasion in both pathogens, and can regulate and protect the pathogen against the host response. Understanding the mechanisms employed by these bacteria to infect the host could contribute to develop effective interventions for the control of tuberculosis and anaplasmosis. This review focuses on the common strategies employed by two zoonotic pathogens, Anaplasma and Mycobacterium spp., highlighting also the different mechanisms used to infect host cells.
Part of the book: Tuberculosis