The Flp type IV pilus operon of Mycobacterium tuberculosis is expressed upon interaction with macrophages and alveolar epithelial cells

The genome of Mycobacterium tuberculosis (Mtb) harbors the genetic machinery for assembly of the Fimbrial low-molecular-weight protein (Flp) type IV pilus. Presumably, the Flp pilus is essential for pathogenesis. However, it remains unclear whether the pili genes are transcribed in culture or during infection of host cells. This study aimed to shed light on the expression of the Flp pili-assembly genes (tadZ, tadA, tadB, tadC, flp, tadE, and tadF) in Mtb growing under different growth conditions (exponential phase, stationary phase, and dormancy NRP1 and NRP2 phases induced by hypoxia), during biofilm formation, and in contact with macrophages and alveolar epithelial cells. We found that expression of tad/flp genes was significantly higher in the stationary phase than in exponential or NRP1 or NRP2 phases suggesting that the bacteria do not require type IV pili during dormancy. Elevated gene expression levels were recorded when the bacilli were in contact for 4 h with macrophages or epithelial cells, compared to mycobacteria propagated alone in the cultured medium. An antibody raised against a 12-mer peptide derived from the Flp pilin subunit detected the presence of Flp pili on intra- and extracellular bacteria infecting eukaryotic cells. Altogether, these are compelling data showing that the Flp pili genes are expressed during the interaction of Mtb with host cells and highlight a role for Flp pili in colonization and invasion of the host, subsequently promoting bacterial survival during dormancy. Copyright © 2022 Alteri, Rios-Sarabia, De la Cruz, González-y-Merchand, Soria-Bustos, Maldonado-Bernal, Cedillo, Yáñez-Santos, Martínez-Laguna, Torres, Friedman, Girón and Ares.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Pre-ART HIV-1 DNA in CD4+ T cells correlates with baseline VIRO-immunological status and outcome in patients under first-line ART

Objectives We evaluated the association between pre-ART HIV DNA and HIV-infected participant characteristics at baseline as well as with their response to first-line ART. Methods Four hundred and thirty-three patients from the ICONA cohort, starting first-line ART after the year 2000, were analysed. Pre-ART HIV DNA was quantified with the modified COBAS TaqMan HIV-1 Test and normalized by CD4+ T cells. Linear correlation between pre-ART HIV DNA and other continuous markers (HIV RNA, CD4 count, markers of inflammation and coagulation) at baseline was evaluated by means of Pearson correlation coefficient and a linear regression model. Survival analyses and Cox regression models were used to study the association between pre-ART HIV DNA and time to VIRO-immunoclinical events. Results Pre-ART HIV DNA [median (IQR): 10 \u20ac 702 (3397-36 \u20ac 632) copies/10 6 CD4+ T cells] was correlated with pre-ART HIV RNA [R 2 = +0.44, (P 10 \u20ac 000, 81.1% for 1000-10 \u20ac 000 and 86.4% for 10-1000 copies/10 6 CD4+ T cells; P = 0.0004). Higher pre-ART HIV DNA was also correlated with increased risk of VIROlogical rebound (defined as HIV RNA >50 copies/mL) by 24 months (17.2% for >10 \u20ac 000, 7.4% for 1000-10 \u20ac 000 and 4.3% for 10-1000 copies/10 6 CD4+ T cells; P = 0.0048). Adjusted HRs of all VIROlogical rebound definitions confirmed these findings (P 64 0.02). Conclusions Pre-ART HIV DNA, along with HIV RNA and CD4+ T cell count, should be considered as a new staging marker to better identify people at lower (or higher) risk of viral rebound following achievement of VIROlogical suppression ( 6450 copies/mL)