Pieces of a Mosaic
A vaccine candidate hopes to have a global candidate
by Jeannie Wraight

An HIV preventative vaccine is making its way through the clinical trial system with a new study beginning enrollment later this year. Mosaico is the latest in a string of primate and then human studies stretching over the past fifteen years, testing vaccine candidate Ad26.Mos4.HIV. The Phase III clinical trial will evaluate the Janssen Pharmaceutical vaccine in men who have sex with men (MSMs) and transgender women and men. Mosaico is a collaboration between Janssen, the NIH, the HVTN and the U.S. HIV Military Research Program (MHRP).

“We’re very excited because it’s an exciting product that has been extensively tested in earlier-stage trials. People appear to not only develop a strong immune response but a lasting immune response, which is important in a vaccine,” stated Dr. Susan Buchbinder, MD, Protocol Chair of the Mosaico Trial and Director of Bridge HIV at the San Francisco Department of Public Health.

Mosaico (HPX3002/HVTN 706) will be enrolling 3,800 transgender individuals and men who have sex with men at fifty-five sites throughout the United States, Latin America, and Europe. In the U.S., twenty-two sites throughout sixteen cities will enroll HIV negative, at risk participants. Sites in Argentina, Brazil, Italy, Mexico, Peru, Poland and Spain will also participate in the study.

Mosaico is the largest clinical trial to date evaluating the promising “Mosaic’” vaccine candidate, that, if successful, will be able to be used globally against all strains of HIV. This is due to its genetic inserts, which contain various HIV strains. Producing an effective vaccine that would maintain protection against the numerous strains of HIV found around the world has been a major challenge in vaccine research and development. The establishment of one vaccine that can be used in every population and against all clades of HIV is essential to the eventual eradication of HIV.

According to Dr. Buchbinder, the vaccine used is “designed to be a global vaccine. It takes information from multiples clades around the world. If effective, we hope people could be protected against multiple strains of HIV so we don’t need to recreate a vaccine for each region of the world.”

Mosaico is a complementary study to Imbokodo, a separate clinical trial of a near identical vaccine which has already completed enrollment [see my A&U Destination: Cure column in March 2018]. The one difference between the vaccines being studied is that, in the Mosaico trial, a mosaic insert is added to the third and fourth injections (four total injections) and for Imbokodo a Clade C insert is used. Clade B is included in this mosaic insert, and is the prominent clade of HIV seen in North America and Europe. Clade C is the most common strain in Southern Africa. As well as examining different regions, the two studies will examine the vaccine in different populations of people.

Studies have shown that men and women can elicit different immune responses to a vaccine. When asked if a vaccine might behave differently in transgender people on hormone therapy, Dr. Buchbinder stated that this is why they are testing it specifically in transgender men and women because they don’t know how the hormones some transgender people take will affect their immune response.

A 2019 systematic review and meta-analysis published in the American Journal of Public Health found that an estimated 14% of all transgender women are living with HIV and 44% of black/African American transgender women are currently living with HIV. The CDC recognizes transgender men and women as being at a high risk for HIV. Many transgender individuals experience stigma, social rejection, workplace discrimination, difficulty obtaining employment and social isolation. This can contribute to risky behaviors and prevent them from fully integrating into society, building healthy support systems and accessing HIV testing and medical care.

Imbokodo enrolled 2,600 sexually- active women ages eighteen through thirty-five from five African countries (South Africa, Malawi, Mozambique, Zambia, and Zimbabwe). These countries were chosen due to the extremely high risk of HIV in young women. In the regions being studied there are 3,500 new HIV infections per week in young girls and women. In South Africa, the hardest hit area of Southern Africa, although HIV rates are very high in men who have sex with men at 26.8% and a rate reported in transgender women to be double that of MSMs; young cisgender women are at an even higher risk. Young cisgender women between the ages of fifteen and twenty-four alone, make up 37% of new infections. The large Phase II clinical trial is expected to be completed in 2021.

Results from Mosaico are expected in 2023, with researchers hoping to achieve at least a 65% protective rate against HIV. Stay tuned….

Jeannie Wraight is the former editor-in-chief and co-founder of HIV and HCV Haven (www.hivhaven.com) and a blogger and writer for TheBody.com. She is a member of the Board of Directors of Health People, a community-based organization in the South Bronx and an advisor to TRW (Teach me to Read and Write), a community-based organization in Kampala, Uganda. She lives with her husband in New York City.