human papillomavirus or HPV is a double-stranded DNA pathogen that targets the epithelia at the level of the epithelial linings (anogenital and upper respiratory tracts) and the epidermis. Thus, this targeting proposes two types, the mucosal and the cutaneous types respectively.
Cancers HPV cause in women and men:
|Vagina||Oropharynx (throat back and tonsils)|
|Vulva||Non-melanoma skin cancer|
Will my HPV infection cause cancer?
In most cases and especially for men, you don’t have to worry about human papillomavirus infection. In other words, it will clear on its own without you even knowing you have it. However, what happens if the infection and symptoms persist? It is rare but here we can suggest the possibility that it's going to cause cancer. Also, depending on the HPV strain and site of infection, we would be able to conclude which type of cancer.
Can I screen or test for HPV infection?
In fact, there isn’t a test or screening method for the infection for men. Therefore, if you are at a higher risk of having anal cancer (has HIV or had anal sex) your doctor will ask of you to have an anal pap test. On the other hand, screening for cervical cancer is available for women with high-risk to HPV infection. Most importantly, early diagnosis of cancer during its early stages offers higher probability of successful treatment.
Vaccine effectiveness against HPV and side effects:
According to WHO, HPV vaccine targets the population of girls between 9 and 14 years old prior to becoming sexually active with 2 doses, and girls who age 15 or more with 3-dose program. Moreover, the vaccine can be taken by girls aging between 9 and 26 years old, and can be taken up to the age of 45 after checking with your doctor. Similarly, men can take the vaccine within the age of 27 and similarly can consult a doctor if they want to take the vaccine at a higher age up to 45 years old. Note that taking the vaccine at an old age is associated with being at a higher risk of acquiring a new HPV infection due to having a new partner. Above all, the vaccine is totally safe and the only reported side effect is local symptoms which fades within short time (injection site).
- The three licensed vaccines are bivalent, quadrivalent and nonavalent
- All three vaccines show similar efficiency against HPV-16 and HPV-18
- Nonavalent vaccine added extra protection against HPV 31/33/45/52/58
- For females, vaccination reduced having the strains 6/11/16/18
- For males, the quadrivalent vaccine offers efficacy against developing external genital lesions and the persistence of strains 6/11/16/18
- The 2-dose and 3-dose are both efficient unlike a 1-dose program
- The vaccine works against oral HPV-16 and HPV-18 infection
- High probability of developing IgG antibodies in the oral fluid after vaccination
Human papillomavirus mechanism of causing cervical cancer (mucosal):
HPV strains are classified as high-risk and low-risk relevant to causing cervical cancer. For example, the alpha genus subset harbouring HPV-16 and HPV-18 propose a high-risk of 99% to causing cervical carcinoma. As a matter of fact, the infection by these strains is found in lysogenic mode (integrated with the host DNA), driving the expression of the early genes E6 and E7. The resulting E6 protein mode of action is to disable specific tumour-suppressor gene product “P53”, while E7 protein renders inactive the rinoblastoma tumour-suppressor protein “pRB”. Consequently, suppressing these proteins results in oncogenic cells in the cervical transformation zone “invasion”.
Human papillomavirus mechanism of causing skin cancer (cutaneous):
The beta genus of 25 HPV types also called epidermodysplasia verruciformis (EV) are responsible for non-melanoma skin cancer. Similarly, to mucosal HPV types, cutaneous HPV express E6 and E7 gene products with the only difference of E5 not having a clear open reading frame (ORF). Apparently, hit and run mechanism prevail where the virus is necessary for the formation of cancer but not for maintenance. Studies showed that E6 and E7 are responsible for proliferation, and are involved with UV radiation (main factor causing skin cancer) where they facilitate the build-up of UV-induced DNA mutations.
-IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Human Papillomaviruses. Lyon (FR): International Agency for Research on Cancer; 2007. (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 90.) 4, Molecular Mechanisms of HPV-induced Carcinogenesis.
-Kamolratanakul S, Pitisuttithum P. Human Papillomavirus Vaccine Efficacy and Effectiveness against Cancer. Vaccines (Basel). 2021 Nov 30;9(12):1413. doi: 10.3390/vaccines9121413. PMID: 34960159; PMCID: PMC8706722.