Role of Exosomes in the Transfer of Viral Nucleic Acids to Recipients Cells: in Vitro Studies with Cell Line Supernatant and Patient-Derived Exosomes

Human PapillomaVirus (HPV) is a main cause of cervical cancer in which HPV DNA is frequently found integrated into human genome at fragile sites. Meta analytic studies reported association between HPV and Breast Cancer (Bae JM, 2016). We found 30% of HPV DNA in breast cancer tissues, confirmed by ISH assay. HPV DNA is also found in other extra-genital tissues, including oro-pharingeal, anal, colon and skin (Kim SM, 2016; Pérez LO, 2010). Owing to the lack of viremia, HPV DNA presence in other districts, is still a conundrum. We hypothesized that the presence of HPV DNA in extra-genital tissues could be in relation with exosomes. Exosomes are extracellular vesicles, involved in cellular communication, tumor progression and biological molecules carriers. We isolated exosomes from 59 serum specimens from breast cancer patients by differential ultracentrifugation and we identified 5 HPV DNA positive samples. Subsequently we isolated exosomes, from HeLa and Caski supernatants (HPV18 and HPV16 positive, respectively) and from HPV DNA positive serum, urine and liquor patient by CD9-immunobeads isolation kit. Exosomes obtained were used to perform viral transfer in different cell lines. Finally, the literature reports association between SV40 and certain types of cancer, including bone tumors (Vilchez RA, 2003). In line with literature, we found 7/70 SV40 DNA in bone tumors (unpublished). We isolated exosomes, from COS7 supernatant (SV40 positive cell line) and we tested acid nucleic viral transfer to osteosarcoma cell lines. Exposed cells were analyzed by PCR, Real-time PCR and Digital PCR, demonstrating the viral nucleic acids transfer in receiving cells. The viral nucleic acids discovery in receiving cells, confirm the role of exosomes as biological molecules carriers. The mechanism through which the viral content is released, is yet to be clarified, as well as if it is sufficient to trigger infection.