Outwit HIV Where it Hits the Most
Since it was identified three decades ago, HIV has infected more than 78 million people worldwide and has killed half of those it has infected. Antiretroviral drugs have made AIDS treatable for those who have access and adhere to it, and — by reducing viral load in blood — can reduce the risk of transmission to others. However, only 45% of those living with HIV in low- and middle-income countries who are eligible for treatment under the current guidelines by the World Health Organization actually access treatment. In 2013, 1.5 million people worldwide died from AIDS-related causes, and 2.1 million people newly contracted HIV.
Vaccine researchers worldwide are working relentlessly toward training the immune system to prevent new infection with HIV or to control or even clear existing infection. A vaccine that controlled infection would reduce viral load and thereby avoid or delay progression to AIDS, and also reduce the risk of transmission to others.
- Sub-Saharan Africa is the epicenter of the global AIDS epidemic. About 68 percent of the almost 6,000 people worldwide infected each day with HIV are living in Sub-Saharan Africa. About 19 percent of people in South Africa and 27 percent in Swaziland are living with HIV. In Eastern Africa, prevalence in the general population can still reach 5 to 7 percent, and can be several times higher among commercial sex workers, men who have sex with men, transgender people and highly mobile communities such as fisher folk around Lake Victoria. Of the 3.2 million children worldwide under the age of 15 living with HIV, 91 percent live in Sub-Saharan Africa. Incidence in young women and girls in sub-Saharan Africa is up to five times that of men and boys their age.
- HIV mutates more rapidly than most other viruses, escapes the immune system’s responses and exists in different strains globally. Only a few people live with untreated HIV without progressing to AIDS (long-term non-progressors); their immune systems are able to fully contain HIV for decades. In most cases however, HIV establishes persistent infection very quickly after transmission and hides in reservoirs from which it can strike again at any time – so the opportunity for a vaccine to prevent or control initial infection is short-lived. An effective HIV vaccine likely will need to induce both arms of the adaptive immune system, antibodies and killer T cells, to prevent infection with HIV and progression to AIDS.
- Broadly neutralizing antibodies found in about 5% of the people living with untreated HIV (elite neutralizers) can neutralize many if not all of the many HIV variants in laboratory experiments and in monkeys, and may be able to prevent new infection with HIV. Broadly neutralizing antibodies have cleared existing infection in some monkeys. Research has also shown that killer T cells (CD8+) can control HIV replication in both acutely infected people and long-term non-progressors, and as part of an effective vaccine may play an important role in preventing new or clearing initial infection. However, HIV’s huge variability and capacity to play hide and seek with the immune system continue to pose significant challenges to the design of an effective vaccine. The VISTA partnership proposes to address some of these challenges.