Airway Microbes and Immune Networks Reshape Inflammation in HIV-Linked COPD

Chronic obstructive pulmonary disease, or COPD, has quietly become one of the most significant yet under-studied chronic conditions affecting people living with HIV in sub-Saharan Africa. As antiretroviral therapy extends life expectancy across the region, the long-term consequences of chronic airway disease are emerging as a major clinical burden. A new study published in Nature Communications by an international team led by researchers at Makerere University in Kampala and the Berlin Institute of Health at Charité has now taken one of the most detailed looks yet at how the airway microbiome, the immune system and inflammatory signalling interact in this population, revealing a picture far more nuanced than a simple catalogue of bacterial species.

The research, coordinated by first authors Alex Kayongo, Theda Ulrike Patricia Bartolomaeus and Till Birkner, with Sofia K. Forslund-Startceva as senior author, enrolled 200 adults stratified by both HIV and COPD status. Crucially, 160 of these participants were followed for two years, allowing the team to move beyond a single snapshot and examine how airway microbial communities change over time. This longitudinal design matters because cross-sectional studies, which sample individuals at only one point, cannot distinguish stable disease-associated features from ordinary temporal fluctuation, a limitation that has hampered much of the previous microbiome literature in respiratory medicine.

Methodologically, the study stands out for the breadth of its integrated multi-omics framework. The researchers combined 16S rRNA gene profiling of sputum to characterise bacterial communities, quantification of bacterial outer membrane vesicles, which are small membrane-bound particles shed by bacteria that can carry inflammatory cargo, and detailed profiling of airway cytokines, the signalling molecules that orchestrate inflammation. On the host side, they deployed cytometry by time of flight, or CyTOF, to phenotype immune cells at high resolution, bulk transcriptomics of induced sputum, bronchoalveolar lavage and peripheral blood, and single-cell RNA sequencing of bronchoalveolar lavage cells, which was then used to guide computational deconvolution of cell-type proportions in bulk samples.

Perhaps the most striking finding is what the team did not find. Contrary to expectations, sputum microbial communities were shaped predominantly by temporal ecological turnover, meaning that the composition of the airway microbiome changed substantially over time within individuals, rather than being primarily determined by HIV status, COPD status, or the combination of the two. Microbial diversity, microbiome instability, outer membrane vesicle burden and inferred airway cellular composition were largely preserved across the clinical groups. This suggests that the airway microbial ecosystem in this cohort is more resilient, or at least more variable in ways unrelated to disease, than many researchers had assumed.

Yet the study did not come up empty-handed. When the authors looked more closely, they identified disease-specific microbial signatures associated with HIV-associated COPD, indicating that particular bacterial taxa or community patterns do track with the combined condition even though the overall architecture of the microbiome does not. Alongside these microbial signatures, the team detected inflammatory transcriptional remodeling that was concentrated in induced sputum, the sample type most directly reflecting the airway environment. In other words, the host’s gene expression programs in the airways, rather than gross microbial composition, appear to be where the immunological fingerprint of HIV-associated COPD is most clearly written.

The emphasis on non-linear host-microbe interactions is central to the study’s conceptual contribution. Traditional analyses often test for simple linear associations between the abundance of a microbial taxon and a host measurement. Such approaches can miss relationships that only emerge above certain abundance thresholds, that depend on the presence of other microbes, or that vary across immune contexts. By applying integrated analyses designed to capture these selective and non-linear interaction networks, the researchers were able to link discrete microbial taxa with specific inflammatory, immune and transcriptional programmes, mapping a web of relationships that would have been invisible to simpler statistical models.

These findings carry substantial implications for how microbiome research in respiratory disease should be interpreted and designed. If temporal turnover dominates microbial variation, then single-time-point studies risk misattributing random ecological drift to disease. Conversely, if the most robust disease signals reside in host transcriptional responses and in selective, context-dependent interactions with particular taxa, then therapeutic strategies aimed at broadly reshaping the microbiome, such as indiscriminate antibiotics, may be poorly matched to the underlying biology. More targeted interventions, informed by the specific host-microbe networks identified here, become a more plausible long-term goal.

The study is also notable for its setting and its collaborative structure. Conducted in Uganda with clinical sites including Makerere University Lung Institute, Nakaseke General Hospital and the African Community Center for Social Sustainability, and with analytical partners in Berlin, Vienna, Graz, Heidelberg, London, Miami and Baltimore, the work addresses a genuine gap in global health research. Most large-scale airway microbiome studies have been conducted in high-income countries, and the ecology of the airway in African populations, where HIV prevalence, environmental exposures and prior infectious disease histories differ substantially, has been poorly characterised. The funding came from the US National Institutes of Health Fogarty International Center, the European and Developing Countries Clinical Trials Partnership supported by the European Union, Novartis Global Health, the German Research Foundation, the German Federal Ministry of Education and Research and the European Union’s Horizon 2020 programme.

For clinicians managing the growing population of people living with HIV who develop chronic lung disease, the study offers both reassurance and a caution. The relative preservation of microbial diversity and immune composition suggests that HIV-associated COPD in this cohort is not simply a state of catastrophic ecological collapse in the airways. At the same time, the identification of disease-specific microbial signatures and concentrated inflammatory remodeling in induced sputum points to measurable molecular changes that could, with further validation, serve as biomarkers for disease activity or treatment response. Because the inflammatory signal was strongest in the airway compartment itself, sputum-based monitoring may prove more informative than peripheral blood markers.

The authors note that the article was shared early to provide faster access to peer-reviewed, accepted research, with a final version of record to follow, and the work is published open access under a Creative Commons Attribution licence. As follow-up studies extend this framework to larger cohorts, longer follow-up periods and interventional settings, the central lesson of this research is likely to endure: understanding chronic lung disease in people living with HIV requires looking not just at which microbes are present, but at when they change, how they interact with host immunity in non-linear ways, and where in the airway the resulting inflammatory programs are actually expressed.

Subject of Research: Airway microbiome ecology and host immune interactions in HIV-associated COPD

Article Title: Microbial ecological instability and non-linear host interactions shape airway inflammation in HIV-associated COPD

Article References: Kayongo, A., Bartolomaeus, T. U. P., Hecker, J., Birkner, T., Vila, E., Ntayi, M. L., Markó, L., Löber, U., Olweny, G., Kyalo, E., Kyamulabi, D., Ndawula, J., Ssengooba, W., Nabatanzi, R., Kyobe, S., Nassali, F., Kigozi, E., Kalyesubula, R., Munana, R., … Forslund-Startceva, S. K. (2026). Microbial ecological instability and non-linear host interactions shape airway inflammation in HIV-associated COPD. Nature Communications. https://doi.org/10.1038/s41467-026-78400-4

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78400-4

Keywords: HIV, COPD, airway microbiome, 16S rRNA profiling, outer membrane vesicles, CyTOF, single-cell RNA sequencing, cytokines, inflammation, multi-omics, Uganda, host-microbe interactions