Chest imaging in AIDS

Risk Factors Associated With Quantitative Evidence of Lung Emphysema and Fibrosis in an HIV-Infected Cohort

INTRODUCTION

The disease spectrum for HIV-infected individuals has shifted toward comorbid non-AIDS conditions including chronic lung disease, but quantitative image analysis of lung disease has not been performed.

OBJECTIVES

To quantify the prevalence of structural changes of the lung indicating emphysema or fibrosis on radiographic examination.

METHODS

A cross-sectional analysis of 510 HIV-infected participants in the multicenter Lung-HIV study was performed. Data collected included demographics, biological markers of HIV, pulmonary function testing, and chest computed tomographic examinations. Emphysema and fibrosis-like changes were quantified on computed tomographic images based on threshold approaches.

RESULTS

In our cohort, 69% was on antiretroviral therapy, 13% had a current CD4 cell count less than 200 cells per microliter, 39% had an HIV viral load greater than 500 copies per milliliter, and 25% had at least a trace level of emphysema (defined as >2.5% of voxels <-950HU). Trace emphysema was significantly correlated with age, smoking, and pulmonary function. Neither current CD4 cell count nor HIV viral load was significantly correlated with emphysema. Fibrosis-like changes were detected in 29% of the participants and were significantly correlated with HIV viral load (Pearson correlation coefficient = 0.210; P < 0.05); current CD4 cell count was not associated with fibrosis. In multivariable analyses including age, race, and smoking status, HIV viral load remained significantly correlated with fibrosis-like changes (coefficient = 0.107; P = 0.03).

CONCLUSIONS

A higher HIV viral load was significantly associated with fibrosis-like changes, possibly indicating early interstitial lung disease, but emphysematous changes were not related to current CD4 cell count or HIV viral load.

The HIV-1 transactivator protein Tat is a potent inducer of the human DNA repair enzyme beta-polymerase

OBJECTIVE

This study examines the effects of the HIV-1 regulatory proteins, Tat and Rev, on the expression of the DNA polymerase beta (beta-pol) gene, which encodes a key protein in the DNA base-excision repair pathway. The rationale for these experiments is to examine the potential involvement of base-excision repair protein deregulation in HIV-1-related lymphomas.

DESIGN

Expression of beta-pol mRNA was examined in AIDS-related lymphomas and non-AIDS-related lymphomas and as a function of HIV-1 infection of B cells in culture. The effect of Tat or Rev over-expression on beta-pol promoter expression was tested by transient co-transfection assays with a beta-pol promoter reporter plasmid and a Tat or Rev over-expression plasmid.

METHODS

Northern blot analysis was used to quantitate beta-pol expression in lymphoma and cells. Raji cells were co-transfected with a chloramphenicol acetyltransferase (CAT) reporter plasmid and a plasmid over-expressing Tat or Rev. CAT activity was measured in transfected cells.

RESULTS

beta-Pol mRNA was > 10-fold higher in AIDS-related than in non-AIDS B-lineage lymphomas. beta-Pol expression was up-regulated in a B-cell line upon infection with HIV-1, and increased in Raji cells upon recombinant expression of the Tat gene. The beta-pol promoter was transactivated (fourfold induction) by Tat, but not by Rev. Tat-dependent transactivation required a binding site for the transcription factor Sp1 in the beta-pol promoter.

CONCLUSION

These results suggest that HIV-1 Tat can interact with cellular transcription factors to increase the steady-state level of beta-pol in B cells. Tat-mediated induction of beta-pol may alter DNA stability in AIDS-related lymphomas.