Tobacco mosaic virus in cigarettes and saliva of smokers

Background: Tobacco mosaic virus (TMV) has been described as viable in cigarettes or cigar tobacco. It has been cultured about 50 years ago from sputa and thoracentesis fluids of cigarette smokers with a history of pulmonary disease and from lung cancerous matter. In addition, TMV RNA has been recovered recently from human stools while tobacco DNA was recovered from smokers' bronchoalveolar lavages. Objectives: We assessed the prevalence, titers, and infectivity of TMV in tobacco cigarettes and in the saliva of smokers and non smokers. Study design: Tobacco cigarettes from 10 packs of different brands were purchased. Saliva was collected from 12 smokers and 15 non-smokers. Cigarettes and saliva samples were tested for the presence of TMV RNA using a home-made quantitative real-time RT-PCR assay. TMV RNA quantification was enabled by using dilutions of purified TMV. TMV viability was tested by inoculating leaves of Nicotiana tabacum Xanthi (NtX). Results: All 47 smoking cigarettes of six brands were TMV RNA-positive (mean titer, 9.5 log(10) copies/cigarette); TMV was found viable in 53% of them. In addition, 20/44 (45%) saliva from 12 smokers compared to 0/16 saliva from 15 non-smokers tested positive for TMV RNA (mean titer, 3.8 log(10) copies/ml) (p = 0.001). Conclusions: Our results indicate that the TMV genome may get access to the human body by direct exposure through smoking. Although plant viruses are considered not pathogenic for animals, these data prompt to study if TMV RNA is present and induces a modification of the transcriptional program in lung cells of cigarette smokers. (C) 2012 Elsevier B.V. All rights reserved.