The lung microbiome in patients with HIV complicated with community-acquired pneumonia: a cross-sectional pilot study.

Background: The composition of lung flora in HIV-combined community-acquired pneumonia (CAP) populations may be associated with the duration and severity of the disease. Additionally, a correlation may exist between lung flora balance and the body's autoimmune status. However, the number of studies in this area is limited. Therefore, we collected alveolar lavage fluid from 110 HIV-positive CAP patients at Beijing Ditan Hospital. We preliminarily explored the lung flora of this population using 16S amplicon analysis, and found some clues about the relationship between flora and immune status by comparing the flora of two groups of people with different immune status. Results: We found that the lung microbiome of HIV patients with CAP exhibited a "high-level aggregation-low-level dispersion" pattern across taxonomic hierarchies, this was characterised by dominant taxa at higher classification levels and dispersed, low-abundant taxa at lower levels. Microbial diversity in the AIDS group (CD4+ counts < 200 cells/μL) was marginally lower than in the HIV group, but the difference was not statistically significant. The AIDS group exhibited increased relative abundances of pathogenic taxa (Gammaproteobacteria, Fusobacteriia) and decreased relative abundances of symbiotic taxa (Bacilli, Cyanobacteriia). LEfSe revealed significant enrichment of oral- and gut-associated microbial communities in the HIV group, as opposed to pathogen-enriched communities in the AIDS group. Microbial network analysis showed enhanced modularization in the AIDS group, with reduced clustering coefficients and network density, indicating destabilized microbial communities. Immune collapse appeared to drive a shift from cooperative hub-based to competitive modular microbial structures. Conclusions: Immune status profoundly influenced the composition and function of the pulmonary microbiome in HIV infection. AIDS patients exhibited pathogen-dominated, less stable microbial communities. These findings provided foundational insights into interactions among HIV, CAP, and the pulmonary microbiome, and informed the development of microbiome-targeted interventions.