Question

b. Tobacco Mosaic Virus (TMV) has been isolated from virtually all commercial tobacco products. Why then, is TMV infection not a hazard for humans? That is, why does its host range only include some plants, but not humans? Think about the steps of the Viral Reproductive Cycle above, especially how an infection would have to be initiated.

Answer 1

Recent studies has found that Humans have antibodies against a plant virus that TMV. Tobacco mosaic virus (TMV), a widespread plant pathogen, is found in tobacco (including cigarettes and smokeless tobacco) as well as in many other plants. Plant viruses do not replicate or cause infection in humans or other mammals. Experiments were done to determine whether exposure to tobacco products induces an immune response to TMV in humans. Using a sandwich ELISA assay, it has been detected that serum anti-TMV antibodies (IgG, IgG1, IgG3, IgG4, IgA, and IgM) in all subjects enrolled in the study (20 healthy smokers, 20 smokeless-tobacco users, and 20 non-smokers). Smokers had a higher level of serum anti-TMV IgG antibodies than non-smokers, while the serum level of anti-TMV IgA from smokeless tobacco users was lower than smokers and non-smokers. Using bioinformatics, it has been also found that the human protein TOMM40L (an outer mitochondrial membrane 40 homolog--like translocase) contains a strong homology of six contiguous amino acids to the TMV coat protein, and TOMM40L peptide exhibited cross-reactivity with anti-TMV antibodies. That's why the range of TMV is within plants.