Recent research suggests a 20-year-old HIV-positive adult, placed on combination antiretroviral therapy (ART), in the United States or Canada, can expect to survive into their early 70’s – a life expectancy that is close to that of the general population.
The findings were recently published in the Dec. 18 issue of the open access journal PLOS One. The research was conducted by Hasina Samji and colleagues, working for the British Columbia Centre for Excellence in HIV/AIDS (BC-CfE) and the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD).
ART Decreases HIV Transmission in General Population
Since the introduction of ART, the survival rate among HIV-infected individuals has improved drastically; this has only been enhanced by successive improvements, designed to make regimens simpler, more effective and better tolerated by patients.
The introduction and improvement of ART treatment regimens is conjectured to have had a major societal impact. A study published in the New England Journal of Medicine, entitled Prevention of HIV-1 infection with early antiretroviral therapy, concluded that ART that was capable of reducing viral replication could impede transmission of human immunodeficiency virus type 1 (HIV-1) within the general population.
In the U.S., 2009 estimates of life expectancy at age 20 years were 57.0 and 61.7 years for males and females, respectively. Meanwhile, the same estimates made for the general population of Canada found life expectancies of 59.7 and 63.9 years for males and females, respectively. According to the study’s authors, while the influence of ART has been extensively measured in HIV-positive adults, globally, the effect of ART witnessed across the U.S. and Canada is less extensively documented.
Life Expectancy of Treated HIV Patients Approaching that of Uninfected Individuals
On this basis, the researchers began collecting estimates of the life expectancy, which were obtained from mortality rates from the NA-ACCORD – a multi-site collaboration of cohorts of HIV-positive individuals in Canada and the U.S. At scheduled intervals, the afore-mentioned cohorts provided data about their participants’ ART prescriptions and laboratory testing; this includes HIV-1 RNA (viral load) and CD4 cell counts.
Ultimately, the life expectancies for almost 23,000 patients on ART were calculated using mortality rates in the early to mid-2000s. All participants from the study were aged 20 years or older.
The authors established that the life expectancy at age 20 increased markedly from 36.1 years in 2000-2002 to 51.4 years in 2006-2007 – an unprecedented change that the authors claim is a “… testament to the improvements and overall success of ART.”
The researchers also found a significant reduction in the life expectancy among a variety of groups, although the difference between men and women was negligible:
“Men and women had comparable life expectancies in all periods except the last (2006–2007). Life expectancy was lower for individuals with a history of injection drug use, non-whites…”
Similarly, life expectancy was low in individuals that had a CD4 count lower than 300 cells per cubic millimeter; whereas normal values typically lie between 500 and 1200 cells per cubic millimeter. CD4 cells play a critical role in signaling other types of immune cells, including CD8 killer cells.
In HIV pathology, untreated infection results in a progressive decline in the number of CD4 cells, since HIV targets cells that are of critical importance to the effective function of the human immune system; this includes CD4 cells, dendritic cells and macrophages. The virus interacts with surface receptors on the target host cells and releases its capsid into the cell, where upon the HIV virus can commence replication and transcription, before reassembling and moving on to infect other immune cells.
‘Boston Patients’ Relapse, Dashing Hopes of HIV Cure
The study comes in the wake of some rather disappointing news. The “Boston patients” – who were believed to have been cured of their HIV infections – have relapsed, with the HIV virus re-emerging. Two male patients received bone marrow transplants that, on the surface, seemed to completely eliminate all trace of the virus.
Aside from having been diagnosed as HIV-positive, the Boston patients also had lymphoma – a type of blood cancer that required treatment with a bone marrow transplant. In the aftermath of the procedures, the pair continued to receive ART therapy; eight months following the operation, according to routine testing, both patients appeared to be HIV-free.
Much to the disappointment of experts in the field, the treatment failed and the two patients have resorted to participating in ART regimens, once more.
However, although the results of the treatment are disheartening, researchers believe they can learn much from the Boston patients. Experts argue that our current laboratory tests remain too insensitive to detect the minute numbers of HIV virus that are capable of causing a relapse.
Timothy Henrich from Boston’s Brigham and Women’s Hospital – one of the doctors of the Boston patients – recently discussed the intricate and resourceful nature of the HIV virus:
“Through this research we have discovered the HIV reservoir is deeper and more persistent than previously known and that our current standards of probing for HIV may not be sufficient.”
By James Fenner