Acute HIV infection is the first stage of HIV infection and immediately follows exposure to and transmission of the AIDS virus.
During acute HIV infection, the virus replicates extensively in the absence of any detectable adaptive immune response. It is during this initial cycle of viral replication that important pathogenic processes are thought to occur. These include the rapid destruction of critical CD4+ T lymphocytes, the white blood cells attacked by the virus, and the seeding of virus to a range of tissue reservoirs. By establishing viral reservoirs, latent virus resides permanently in the body, able to hide from elimination by antiviral drugs administered later in the course of disease.
It is also during this period that 70% of individuals experience clinical symptoms of acute infection or what is called acute retroviral syndrome. Usually two to six weeks following infection, influenza or mononucleosis-like symptoms develop, which may include fever, rash and swollen lymph nodes. It has been shown that the severity and duration of these symptoms are associated with speed of the subsequent disease progression. These clinical manifestations of early disease usually resolve within a few weeks, after which some individuals are symptom-free for an average of five to eight years. Importantly, the diagnosis of HIV is too commonly missed during this early period, as other illnesses are mistakenly assumed to be the cause of symptoms.
The resolution of flu-like symptoms -- and the acute phase of infection -- coincides with a significant drop in virus circulating in the body to the so-called viral setpoint. This control of viral replication is associated with an escalated number of CD8+ T cells responding to HIV. Different for each individual, it is the balance attained between the strength of this initial immune control and the pathogenicity of the virus that determines the viral setpoint. It has been shown that the lower the setpoint, the slower the speed of disease progression.
Because of the very high levels of circulating virus in the blood, there is an increased risk of forward transmission to another sexual partner during acute infection, especially at a time when the infected individual is most likely unaware of his or her status. Diagnosing as early as possible is of critical importance for this reason and for the sake of educating individuals in treatment options and risk reduction.
Moreover, much can be learned from studies of acute HIV infection. The fact that high levels of circulating virus in the blood decline early on indicates that the body is initially able to mount an effective immune response. Immunological and virological events that occur during acute HIV infection are thought to be crucial in determining the subsequent course of disease and may contain clues that are critical to our understanding of HIV-1 pathogenesis and to the development of a protective vaccine.
We believe that acute HIV infection represents an ideal scenario to investigate and identify correlates of protective immunity to HIV. The overall goal of the Acute HIV Infection Research Program at MGH is to define predictable elements of the virus-host interaction that occur during acute HIV infection and exploit these to guide effective HIV vaccine design.
New England Journal of Medicine recently publishes article addressing the recent critical advances in our understanding of HIV-1 transmission and acute HIV-1 infection.Acute HIV-1 Infection Myron S. Cohen, M.D., George M. Shaw, M.D., Ph.D., Andrew J. McMichael, M.B., B.Ch., Ph.D., and Barton F. Haynes, M.D.