Study Finds Key To Increased Salmonella Danger In HIV-Positive Individuals
Because of a defective immune response, HIV-positive individuals are at an increased risk of Salmonella infection. Although scientists have known for years that Salmonella poses greater risks in HIV-positive individuals, a recent study published in Science is the first to provide a scientific explanation.
The researchers studied the type of Salmonella bacteria commonly passed through food, such as uncooked meat and eggs. In most healthy individuals, Salmonella food poisoning causes vomiting and diarrhea; however, in HIV-positive individuals, it can be fatal.
In particular, HIV-infected individuals living in underdeveloped countries are not able to receive antiretroviral treatment, and thus are at high risk for severe Salmonella infection.
Based on prior research, researchers expected to find that HIV-positive individuals had an immune deficiency, or lack of antibodies, against Salmonella, which would prevent their immune systems from detecting and hence fighting the bacteria.
Instead, researchers found that HIV-infected individuals have excess levels of antibodies against Salmonella. However, these antibodies were bound to the wrong area on the surface of Salmonella, thereby preventing the immune system from killing the bacteria and also inhibiting effective antibodies from targeting the bacteria.
The researchers concluded that Salmonella causes serious infections in HIV-positive individuals because they have overactive, but ineffective, antibodies that enable the bacteria to thrive, not because they have a weakened or lessened immune response.
These findings are significant in the development of vaccines for Salmonella because researchers now better understand how to direct their investigations. Currently, there are early clinical trials targeting what this study found to be the wrong site on Salmonella, an approach that may actually be harmful.
The researchers stress the importance of developing a vaccine that induces effective antibodies that protect against Salmonella.
It is not yet known whether this finding might apply to other infections that tend to afflict HIV-positive individuals more often.
For more information, please see the Science article (abstract) and editorial about the study.
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