Scientists develop a candidate vaccine for HIV


A study, carried out by the University of Maryland in collaboration with Duke University, has demonstrated in rabbits that a synthetic glycopeptide (or called protein-sugar) could be a potential vaccine against HIV. Findings of the study appear 26 Oct. 2017 in Cell Chemical Biology. According to lead researcher Prof. Lai-Xi Wang of the University of Maryland, although the synthetic glycopeptide didn't prevent HIV from infecting cells, it successfully induced antibody responses against the virus.

Since HIV was first identified in the late 1940s or early 1950s, numerous efforts have been made to develop preventive and therapeutic strategies for HIV infection and the devastating disease AIDS caused by it. Despite great progress in understanding how the virus infects host cells and causes disease, there is still no HIV vaccine yet. Now, HIV/AIDS has become a global pandemic. The WHO estimates that 36.7 million people were living with HIV in 2016. Vaccines and novel therapies are in desperate need.

Why is HIV so hard to combat? Several reasons have been found. First, HIV is a retrovirus, meaning that it stores its genetic information in RNA rather than DNA. Typically, retroviruses are hard to treat than other viruses because of their ability to insert their genome into a host's genome, hiding themselves from the immune system. Second, HIV and other retroviruses mutate so quickly that the body's all-out effort to control infection fails. Moreover, the rapid mutation rate of HIV enables it to become resistant to treatment. Third, HIV infects certain immune cells designed to fight pathogens. Over time, HIV destroys many of these cells, weakening the body's defense. Besides, HIV can remain dormant for a long period of time and then roar back at some points.

The outer coat of the HIV virus, known as a shield or an envelope, is made of molecules from the host cell and viral envelop glycoproteins. Viral envelop glycoproteins, such as gp120, are critical for viral entry into the host cell, so they are considered potential therapeutic targets. However, it is difficult to make the body's immune system to produce antibodies against gp120 because of the protein's chemical and structural properties. As mentioned above, HIV mutates quickly. Therefore, the structure of gp120 differs among strains of HIV.

In this work, Prof. Wang's team looked at a region in the gp120 protein that is highly conserved among HIV strains. A sugar molecule, which is also common among HIV strains, was attached to the gp120 fragment to mimic the sugar shield on the HIV envelope. This synthetic protein-sugar molecule was used as an immunogen to immunize rabbits. The results showed that the synthetic protein-sugar molecule successfully elicited relatively large quantities of antibodies that could recognize gp120 in different dominant strains of HIV.

Collectively, the study demonstrates that the novel synthetic protein-sugar molecule might be a potential HIV vaccine. Although the molecule may not prevent HIV from infecting host cells, it induces a protective immune response.
 
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