Though effectively vaccinating HIV patients against other viruses can be difficult due to their weakened immune systems, the human papillomavirus vaccine shows promise for creating the desired immune response in HIV-positive women, according to the results of an international clinical trial led by Erna Milunka Kojic, associate professor of medicine.
The trial looked at the vaccine’s immunogenicity, or its ability to elicit an immune response in the body, Kojic said. It did not measure the vaccine’s efficacy — whether it is capable of preventing disease — but if the body produces antibodies in response to the vaccine, then researchers “have every reason to think that these antibodies would keep them from getting further (forms of) HPV,” Kojic added.
The clinical trial was the first to examine the effects of the HPV vaccine on women whose HIV had progressed to AIDS, Kojic said. Since they, too, developed antibodies, the vaccine is “very immunogenic,” she added.
“It’s likely that the vaccine fires off a type of antibody response that is long-lasting and very potent and very good at hitting the virus as it’s trying to get in,” said James Hoxie, professor of medicine in the Division of Hematology/Oncology at Penn and director of the Penn Center for AIDS Research, who was not involved in the study.
To measure the vaccine’s success, researchers studied whether vaccinated women developed antibodies and, if they did, whether the antibodies developed at a level vaccine manufacturers deemed successful, Kojic said.
The vaccine — FDA-approved Gardasil — protects against four forms of the virus, two of which can cause various types of cancer, including cervical cancer, and two of which can cause anogenital warts. There had been speculation as to whether HIV-positive women could benefit from the HPV vaccine since they may have previously been exposed to HPV and have weakened immune systems. But the results of the study indicate that the vaccine is safe and immunogenic even for individuals with HIV, Kojic said.
HIV-positive women “have a lot more problems with HPV,” Kojic said. Not only are HIV-infected women likely to have more types of HPV, “they’re also less likely to clear the infection and therefore are more likely to develop some bad outcome from this,” she added.
Between 20 and 35 percent of HIV-infected women have been exposed to any of the types of HPV that the vaccine protects against — a much higher proportion than among women without HIV. But only 4 percent of the subjects had been exposed to all four types of HPV the vaccine targets, she said.
“Human papillomavirus is a massive public health burden, and all the bad things that it does are magnified in a person who is HIV-infected as well,” Hoxie said. Women who are infected by both viruses commonly can control their HIV through medication but still develop cervical cancer that stems from their HPV at young ages, he added. The clinical trial was “a very important step” in understanding whether there is a way of preventing HPV infection in these women, he said.
The results of the clinical trial align with the World Health Organization’s recommendation that people with HIV be vaccinated against the disease, Hoxie said.
The trial had an international focus. Researchers selected women from three countries — Brazil, South Africa and the United States. The international scope of the study was important because the “burden of (HPV) in HIV-infected is even higher in the developing countries,” and different types of HPV are more prevalent in certain regions, Kojic said. Researchers selected Brazil and South Africa specifically because the HPV vaccine is available in those countries.
“I think it’s likely that men would have the same good response to this vaccine as HIV-infected women,” Hoxie said. “So it’s all good news.”
The next phase of testing will involve verifying the safety the initial study determined and examining how long the vaccine’s protection lasts.
While the vaccine’s effectiveness “has to be determined in a longer study,” the development of antibodies is an “encouraging” result, Hoxie said.
Though an increased sample size could help in future studies, this research provides strong support that people at various stages of HIV infection can still develop antibodies, Hoxie said.
The Center for Disesase Control recommends the HPV vaccine for both adolescent females and males, regardless of immune status, according to its website.
A different research group conducted a study examining the effectiveness of the vaccine in HIV-positive men, Kojic said, but it “excluded men with very low (immune cell) counts … so that makes our study a little more unique.”