A recent paper by Liu et al. [1] reports that:

"Tobacco mosaic virus (TMV), a widespread plant pathogen, is found in tobacco... as well as in many other plants. Plant viruses do not replicate or cause infection in humans or other mammals... we detected serum anti-TMV antibodies (IgG, IgG1, IgG3, IgG4, IgA, and IgM) in all subjects enrolled in the study... we also found that the human protein TOMM40L... contains a strong homology of six contiguous amino acids to the TMV coat protein, and TOMM40L peptide exhibited cross-reactivity with anti-TMV antibodies. People who smoke cigarettes or other tobacco products experience a lower risk of developing Parkinson’s disease, but the mechanism by which this occurs is unclear. Our results showing molecular mimicry between TMV and human TOMM40L raise the question as to whether TMV has a potential role in smokers against Parkinson’s disease development."

It seems to me that this is interesting because it raises questions both specific, e.g. whether TMV plays a role in the pathogenesis of PD, and general, e.g. whether any one of a myriad of plant viruses plays a part, not through infection of humans, but by elliciting an immune response?

Colson et al. [2] write:
"we confirmed that humans may carry a high PMMoV [Pepper Mild Mottle Virus] load, likely acquired from food products, and we documented that PMMoV might not only be a common inhabitant of the human gut but may also interact with the human immune system and cause clinical symptoms."

Given what we know about the incidence of PD (genetics, age of onset, geographical variations, the role of the immune system, the role of the microbiota in the gut, no obvious common denominator etc.), I think this is worth looking at.

References

[1] Liu R, Vaishnav RA, Roberts AM, Friedland RP (2013) Humans Have Antibodies against a Plant Virus: Evidence from Tobacco Mosaic Virus. PLoS ONE 8(4): e60621. doi:10.1371/journal.pone.0060621

[2] Colson P, Richet H, Desnues C, Balique F, Moal V, et al. (2010) Pepper Mild Mottle Virus, a Plant Virus Associated with Specific Immune Responses, Fever, Abdominal Pains, and Pruritus in Humans. PLoS ONE 5(4): e10041. doi:10.1371/journal.pone.0010041

John

Don't know if this has any bearing on your thread. I tried to help with cutting tobacco for about 3 hours one day in exchange for sawmill scrap lumber to build my outhouse (this was back about 15 yrs ago) I got very sick for days and didn't seem to have any strength at all while in the tobacco field. The neighbors laughed about how funny I was to watch for a long time. I probably accomplished in 3 hrs what the others did in 45 minutes. I have always been good for a laugh....but always had a previous commitment when they jokingly asked me to come help with tobacco after that.

plant viruses are ubiquitous.
we inhale plant viruses, animal viruses, plant pollen and fungal spores everytime we take a breath.
tobacco is related to potatoes, tomatoes, they are infected by the same viruses
http://www.extension.umn.edu/distrib...re/dg1168.html

tobacco resins penetrate the skin and you get a picking "buzz", the plant viruses are harmless to humans
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1497768/