Genital Human Papillomavirus Transmission Infection Biology Essay

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Genital Human Papillomavirus is probably the most frequent Sexually Transmitted Infection in The Unites States of America and increased a public health concern worldwide. Genital HPV is associated with anogenital warts that could be traced back up to the Roman age. In many individuals, infection would be asymptomatic or resolve spontaneously. Nevertheless, anogenital infections are related with cervical neoplasm that in most cases are likely to be caused by genital HPV.(1-3)

Approximately 5.5 million new cases with HPV considered as the causal agent occurred each year. There are more than 100 types of HPV with 20 to 30 types are concerned as the general source of infection in female genital tract. The benign types (e.g. 6 and 11) are closely related to genital warts meanwhile the malignant types (e.g. 16 and 18) are associated with cervical dysplasia and invasive cancer.(1)

HPV is a genus in the family of papovaviridae which is a double-stranded structure DNA virus. It is classified by its major capsid gene (L1) which will be clinically important in the prophylactic vaccines development.(1-2)

Clinical Trials

At the present time, vaccines for prevent HPV infections are developed. These vaccines have a similar approach with hepatitis B vaccine. A large efficacy trial of HPV vaccine recently reported by the New England Journal of Medicine presents that there were no cases of HPV-16 whether the persistent infection nor the cervical dysplasia are showed in the women who received the experimental vaccine.(1)

Another study reported by the Lancet in early 2005 shows that after two years follow up in a double blinded trial of HPV vaccine, all the women that have been given the trial vaccine did not developed warts or any anogenital infections that could be associated with HPV. In the contrary, in the placebo group three individual had developed genital warts and three others developed CIN - the pre cancerous change.(3)

In developing the HPV vaccines, immunogenicity of virus-like particle (VLP) that consist of L1 protein is the basic principle. The virus-like particle is immunogenic but not infectious. In terms, by giving the HPV vaccination with VLP have been proven to induce a strong antibody response in the individual without infected with HPV. FDA has approved this vaccine in June 2006 as a prevention method of HPV in female aged 9 - 26 years old. Furthermore, the expert group suggested that the vaccination should be given at ages 11 - 12 years old.(2, 4)

The main difficulty in preclinical trial vaccine studies or developments is the nature of papilloma virus which is species restricted. Hence, the verification of study in HVP vaccination to prevent papilloma virus infection will has to depend on the animal papillomavirus types. In this case, the virus types are CRVP (cottontail rabbit papilloma virus) in domestic rabbits, COVP (canine oral papilloma virus) in dogs and BPV4 (bovine papilloma virus type 4) in cattle. The result was even low dose VLP with intramuscular administration could produce antibodies that give a great protection to the animal model. Furthermore, the level of cervicovaginal antibodies that needed to preclude the sexual transmission of oncogenic HPVs could not be assessed due to this limitation.(5)

In an early stage of clinical trials done by Zang et al. (2000), Evans et al. (2001), and Harro et al. (2001); HPV6, HPV11 and HPV16 VLP vaccines are proven to be safe and give a significant immunological response after two or three intramuscular injection with doses of 10 - 50 μg even without alum-based adjuvant.(5)

Three recent study that sponsored by two large vaccine manufactures, GlaxoSmithKline and Mercks, presented phase 2B evidence of efficacy trials of VLP vaccination in healthy women. In all studies, it was proven that the vaccines were safe, no avert effects showed by the women, and there are no proof of complication due to the injection.(5)

Below is a table which shows comparison of three recent studies on VLP vaccines

Table 1. Proof of Concept VLP Prophylactic Efficacy Trials(5)


Koutsky et al., 2002

Harper et al., 2004

Villa et al., 2005

VLP types



6, 11, 16, 18









Trial sites





16 - 23


16 - 23





Vaccination schedule (Mos)

0, 2, 6

0, 1, 6

0, 2, 6

Follow-up (yr)




No. Of cervical infections:




Not reported

% Efficacy



No. of persistent

Infections : Cont/Vac




% Efficacy




No. of Clinical outcomes


9/0 (CIN)

6/0 (CIN)

3/0 (CIN), 3/0 (warts)

% Efficacy




All data for according to protocol (ATP) groups. Outcomes reported only for HPV types with corresponding VLPs in the vaccine.

*3 of 4 outcomes were first HPV DNA detections at the last study visit

From the table above, it is clearly seen that in all studies VLP vaccination gave a convincing result with overall VLP vaccination efficacy of 89 - 100%.

Target Populations(6-7)

12 - 18 year-old girls in schools.

Girls and women age 13 - 26 years old who have not yet been vaccinated, not completed the vaccine series, or who missed doses at school.


There are two commercially registered HPV vaccines for use in Australia:(8)


Company: GlaxoSmithKline

Containing L1 protein of HPV types 16 and 18 (20μg each)

Dose and administration method: 0.5 ml intramuscular injection

Dose schedule: 0, 1, 6 months


Company: Mercks

Containing L1 protein of HPV types 6 (20μg), 11 (40μg), 16 (40μg) and 18 (20μg)

Dose and administration method: 0.5 ml intramuscular injection

Dose schedule: 0, 2, 6 months


Anaphylaxis reaction following the previous dose of HPV vaccine

Anaphylaxis reaction to any vaccine constituent (e.g. yeast protein, aluminium phosphate, sodium chloride, L-histidire, polysorbate and sodium borate)

Pregnant women

Severe febrile illness

Precautions for people with impaired immunity