Trivia: HPV Biology – See If You Know It!

Human papillomavirus (HPV) is not well understood by many people. Its many different types, replicative strategy, and mechanism of spread often lead to confusion, questions, and sometimes concerns of infidelity.

Via our dedicated page, www.prevent-HPV.org, the Vaccine Education Center team often learns about these questions and concerns when people email us; however, in talking with science educators, we have found that many of you also receive HPV-related questions.

So, let’s take a closer look at some facts about HPV.

FACT: More than 100 different types of HPV exist.

HPV is a double-stranded DNA virus that replicates in epithelial cells of the skin or mucosal surfaces. More than 100 types of HPV have been identified. Those that infect mucosal epithelial cells are classified according to the risk they present to people, specifically in terms of their ability to transform cells and lead to cancers.

FACT: Some types cause annoying, but generally harmless, skin warts while others lead to cancers, and sometimes, death.

Types 1, 2, 27 and 57 are most often associated with cutaneous warts.

Of 15 “high-risk” types, 16, 18, and 31 are most often associated with cancers. Cervical, vulvar, vaginal, anal, and oropharyngeal cancers are the most common cancers caused by HPV.

Of 12 “low-risk” types, 6 and 11 are most often associated with genital warts.

The 9-valent HPV vaccine protects against the most common types that cause cancers and genital warts:

• Types 16, 18, 31, 33, 45, 52 and 58 protect against cancers.
• Types 6 and 11 protect against genital warts.

FACT: HPV can replicate silently, without symptoms, for years.

HPV gains access to basal epithelial cells that are damaged; the virus reproduces itself at the same time that the cell reproduces itself. HPV infections can be prolonged because the virus is efficient at circumventing typical innate immune responses in several important ways. First, HPV does not cause cells to break apart in order to release new viruses; instead, virus particles are released as the epithelial layers flake off. Second, the virus does not circulate in the bloodstream. Third, inflammation of surrounding tissues does not occur. Fourth, the virus down regulates innate signaling pathways. This, coupled with the fact that virus particles are not released into the bloodstream, leads to a lower-than-normal presence of antigen-presenting cells in the infected area. The result is that HPV infections may not resolve in all individuals. Outcomes following infection can include:

• Clearance — In this case, active infection occurs until the immune system overcomes the viral trickery. The process can take as long as 1 to 2 years. This is the most common outcome.
• Regression — In this situation, the infection is controlled, but the viral genome is still present in cells. The virus remains in a latent state with periodic bursts of activity.
• Persistent infection — When persistence occurs, ongoing viral gene expression increases the chance for the viral genome to integrate into the host cell genome. This is the type of infection that can eventually progress to cancer.

Regression and persistent infection can lead to positive HPV-related tests, such as Pap tests, at a time distant from the initial infection. For this reason, the infected person’s partner may think the individual was unfaithful when the reality is that the person may have been infected long before the relationship started.

FACT: Although commonly spread by sexual contact, HPV can also rarely be spread in other ways.

While the majority of HPV transmission occurs through sexual intercourse (vaginal or anal), the virus can spread by other means as well. Since virus particles are released from the top epithelial layer, particularly of mucosal surfaces, intimate contact without intercourse can spread the virus, such as genital-to-genital or genital-to-oral contact. Infected women can also spread the virus to their babies during delivery. A small number of infants develop recurrent respiratory papillomatosis (RRP), a condition in which warts develop in the throat and lungs, as a result of infection at birth.

FACT: Almost everyone is infected at some point.

It is estimated that about 80 percent of the population will be infected with HPV at some time in their life. The risk is greater when a person first becomes sexually active and with increasing numbers of sexual partners.

A study by Sara Oliver and colleagues published in 2017 in the Journal of Infectious Diseases indicated that the vaccine has helped not only to decrease transmission in vaccinated people, but also in the general population.

The Vaccine Education Center at Children’s Hospital of Philadelphia (VEC) has been educating about the science of vaccines for almost two decades. During this time, we have developed a variety of materials that may be of interest for your classroom, to share with the community, or for your own family’s vaccination needs. We hope you will take a few minutes to see what we have to offer:

For the classroom

The Vaccine Makers Project (VMP) is the classroom program of the VEC. The dedicated website, www.VaccineMakers.org, offers a variety of free lessons about the immune system, infectious diseases and vaccines.

HPV-related classroom materials include:

• A lesson focused on the innate immune system — This lesson is part of a larger unit about the immune system.
• A lesson focused on how pathogens circumvent the immune system
• An animation that shows how genetic engineering is used to make vaccines

About HPV and the vaccine

The VEC offers a variety of materials for the public and healthcare providers to address common questions and concerns related to HPV disease and vaccines, including:

• A dedicated Q&A webpage, www.prevent-HPV.org — In addition to numerous questions related to HPV biology and vaccination submitted by the public, people can also submit their own HPV-related questions directly to the VEC. If students have questions you can’t answer or if they have questions they are uncomfortable asking, they can use this function to reach us.

• Human Papillomavirus: What You Should Know — One in a series of Q&A sheets that address common vaccine and vaccine safety questions.

• A Look at Each Vaccine: Human Papillomavirus — Web-based information
• Talking about Vaccines with Dr. Paul Offit: HPV — This series of 11 short videos include answers to common questions about HPV and the vaccine.

Stay up to date

Vaccine Makers Project updates offer periodic updates for educators. Sign up.

The Parents PACK program offers monthly updates for parents and the public. Sign up.