Pneumocystis Workshop: 10th Anniversary Summary

The contrast between the depth and quality of presentations during the 1st workshop, in 1988, and those at the 10th workshop, in 2008, is a testament to the progress that has been made during the ensuing 20 years. The genome and transcriptome of P. carinii have been sequenced, the key players in metabolic functions and pathways are being dissected using heterologous systems, and the interplay between host responses to the MSGs and the genetic nature of antigenic variation are being exploited for diverse purposes, including diagnostic modalities and a better understanding of these organisms' survival strategies. The host responses to the organisms are being delineated more finely and appear to involve an entire cadre of cytokines, immune cells, the humoral arm, and other host-related factors. Host responses are also dependent on the physiological state of the particular host and differ across a spectrum of intact defense to frank immunosuppression. In some cases, it appears that the organism itself can downregulate certain immune responses, such as phagocytosis. The role of β-glucan continues to evolve as an injurious inflammatory factor but also as a key signature molecule for diagnosis. Entirely new populations of carriers, reservoirs, and those under colonization are being defined. Many such populations have underlying chronic diseases, such as COPD, to which it is suspected that Pneumocystis contributes in a harmful manner. Although a long-term in vitro culture system remains elusive, antioxidants and vitamins appear to increase replication, and the report of biofilm formation by P. murina and P. carinii holds promise for a more tractable system. As research continues to progress in this area, these once enigmatic fungi are becoming more approachable and understandable and now provide insights into the diversity of microbial survival strategies and biological processes. © 2009, American Society for Microbiology.