Researchers from the Kwon Lab at the Ragon Institute have published findings which indicate that HIV acquisition is up to 3.5 times higher in South African women using injectable progestin-only contraceptives (IPCs). IPCs are the most common form of contraception used in sub-Saharan Africa and are common in some areas of high HIV incidence.

 
The paper, published in The Lancet Infectious Diseases by co-lead authors Elizabeth Byrne and Melis Anahtar, is unique in that it not only identifies an epidemiologic risk of HIV acquisition in IPC users, but also examines the immunologic mechanism for this observation.

 
“There is significant controversy in this area of research,” says Dr. Douglas Kwon. “Although some studies have shown an epidemiologic association of IPCs with increased HIV acquisition, the observation has not been consistent.”

 
One reason for this inconsistency may be that in other large studies, IPC use was associated with less behavioral risk of HIV, for instance, the women using IPCs tended to be older, married, and in stable relationships.

 
“These factors could potentially mask some of the biological effects of IPCs,” noted Ms. Byrne.  The study by Byrne and Anahtar focused on women between 18-23 years of age in which those who used IPCs were indistinguishable in terms of their behavioral risk for HIV infection from those using no long term contraception.

 
The researchers examined immunologic factors in the female genital tract, the site where HIV infection is established in most of the women. They found higher levels of activated CD4 T cells (“HIV target cells”) in the female genital tract of IPC users.

 
“This increased target cell frequency at the site of initial HIV exposure may be why these women are acquiring HIV at higher rates,” observed Dr. Anahtar.  Increased HIV target cells were also observed in the female genital tract of women during portions of their menstrual cycle with high natural levels of progesterone.

 
This study has potentially important implications regarding the reproductive choices of women in areas of high HIV incidence and prevalence.