Aspects of infectious agents and cancer : effects of human Papillomavirus 16 and Escherichia coli on the innate immune defense of human keratinocytes

Abstract

Persistent human papillomavirus (HPV) is the causative agent of cervical cancer and bacterial vaginosis (BV) caused by Escherichia coli (E. coli ) has been implicated as a contributing factor. The innate immune system is our body's first defense against these invading pathogens. Using a novel 3-D organotypic tissue culture model to recreate the viral life cycle of HPV16 we examined mRNA expression of crucial innate immune molecules such as integrins, toll-like receptors (TLRs), and interferons (IFNs). Our model was comprised of normal immortalized keratinocytes (NIKS) and NIKS containing full-length HPV16 (NIKS+HPVI6). These models were also exposed to E. coli , which simulated a BV infection. Models were characterized by examining morphology via hematoxylin and eosin (H + E) staining, keratin expression, DNA synthesis, and viral gene and protein expression. Extraction methodologies were optimized prior to continuing experiments. Extracted RNA was reverse transcribed into cDNA and mRNA was detected for α and β integrins, toll-like receptors 3, 4, and 9, and their downstream molecules interferons -β, -γ, and -λ. Integrin expression was the highest in the control NIKS samples. Expression of α5 integrin was significantly increased in NIKS+E. coli compared to NIKS, which implicates its role in facilitating bacterial infections. Expression of α5 significantly decreased in HPV16 positive samples that could be associated with the increase in proliferation found in HPV infected tissues. Expression of TLRs showed similar trends to previously published data, indicating decreases in all TLRs in HPV16 positive samples. An increase in TLR3 was found in samples containing E. coli , which implicates the role of TLR3 in facilitating E. coli infections. IFN-β was found to increase in the presence of E. coli and HPV16 and this could be associated with the expression of E7, an event that has been implicated in increasing IFN-β production (previously unpublished results). Expression of this interferon was truly unique as it was upregulated in samples exposed to E. coli , while no change was seen in NIKS and NIKS+HPV16 samples. Implications of IFN-β have yet to be elucidated and further investigation into their role in established carcinoma cell lines as well as ex vivo tissues would be ideal. The use of a novel tissue culture model in assessing the status of innate immune molecules provides a new vehicle of investigation. Further investigation into both the adaptive and innate immune response could lead to better treatment options for those affected by persistent and non-persistent HPV infections.