Innate Host Defense against Klebsiella pneumoniae and the Outlook for Development of Immunotherapies

Abstract

<i>Klebsiella pneumoniae</i> (<i>K. pneumoniae</i>) is a Gram-negative commensal bacterium and opportunistic pathogen. In healthy individuals, the innate immune system is adept at protecting against <i>K. pneumoniae</i> infection. Notably, the serum complement system and phagocytic leukocytes (e.g., neutrophils) are highly effective at eliminating <i>K. pneumoniae</i> and thereby preventing severe disease. On the other hand, the microbe is a major cause of healthcare-associated infections, especially in individuals with underlying susceptibility factors, such as pre-existing severe illness or immune suppression. The burden of <i>K. pneumoniae</i> infections in hospitals is compounded by antibiotic resistance. Treatment of these infections is often difficult largely because the microbes are usually resistant to multiple antibiotics (multidrug resistant [MDR]). There are a limited number of treatment options for these infections and new therapies, and preventative measures are needed. Here, we review host defense against <i>K. pneumoniae</i> and discuss recent therapeutic measures and vaccine approaches directed to treat and prevent severe disease caused by MDR <i>K. pneumoniae</i>.