Background:

The lungs were historically identified as one of the major anatomic sites for HIV replication in the pre-antiretroviral therapy (ART) era. However, their contribution to HIV persistence in individuals under suppressive ART remains understudied.

Design:

We assessed HIV persistence and comprehensively characterized pulmonary mucosal CD4+ T cells in HIV-infected (HIV+) individuals receiving long-term suppressive ART versus uninfected participants.

Methods:

Bronchoalveolar lavage (BAL), bronchial biopsies, and matched peripheral blood were obtained from n= 24 HIV-infected adults receiving long-term suppressive ART (median: 9 years) and n= 8 healthy volunteers without respiratory symptoms. HIV-DNA and cell-associated HIV-RNA were quantified by ultra-sensitive PCR, and lung mucosal CD4+ T-cell subsets were characterized by multiparameter flow cytometry.

Results:

The levels of HIV-DNA were 13-fold higher in total BAL cells compared to blood. Importantly, FACS-sorted CD4+ T cells from BAL contained greater levels of HIV-DNA compared to peripheral CD4+ T cells. BAL CD4+ T cells in HIV+ individuals were characterized mostly by an effector memory phenotype, whereas naive and terminally differentiated cells were underrepresented compared to blood. Furthermore, BAL CD4+ T cells expressed higher levels of immune activation (HLA-DR/CD38) and senescence (CD57) markers. Importantly, BAL was enriched in T-cell subsets proposed to be preferential cellular HIV reservoirs, including memory CD4+ CCR6+, Th1Th17 (CD4+ CCR6+ CCR4− CXCR3+), CD4+ CCR6+ CXCR3− CCR4−, and CD4+ CD32a+ T cells.

Conclusion:

The pulmonary mucosa represents an important immunological effector site highly enriched in activated and preferential CD4+ T-cell subsets for HIV persistence during long-term ART in individuals without respiratory symptoms. Our findings raise new challenges for the design of novel HIV eradication strategies in mucosal tissues.