A summary of the fourth annual Virology Education HIV Microbiome workshop.

Each year, a growing international collection of researchers meets at the NIH to share and discuss developments in the microbiome HIV story. This past year has seen continued progress toward a detailed understanding of host-microbe interactions both within and outside the field of HIV. Commensal microbes are being linked to an ever-growing list of maladies and physiologic states including major depressive disorder, chronic kidney disease and Parkinson disease1-3. Pubmed citations for "microbiome" are growing at an exponential rate with over 11,000 in 2018. Various microbial taxa have been associated with HIV infection and some of these taxa associated with HIV infection have also been associated with systemic markers of inflammation in HIV infected individuals. Causality remains unclear however as environmental and behavioral factors may drive HIV risk, inflammation and gut enterotype. Much of the work currently being done addresses potential mechanisms by which gut microbes influence immune and inflammatory pathways. No portion of the microbiome landscape has grown as rapidly as study of the interplay between gut microbes and response to cancer immunotherapy. As Dr. Wargo discussed in her keynote address, this area has opened the door to better understanding on how commensal microbes interact with the human immune system.