T-follicular helper cells generate antibodies that prevent people from getting pneumococcal pneumonia, according to a Australian study whose findings offer important insights on why some people are more vulnerable to the disease than others.
The study, “Production of IgG antibodies to pneumococcal polysaccharides is associated with expansion of ICOS+circulating memory T follicular-helper cells which is impaired by HIV infection,” appeared in the journal PLOS ONE.
Pneumococcal pneumonia is caused by a bacterium known as Streptococcus pneumoniae, or pneumococcus. Children younger than 2 years old, people older than 65 and those with compromised immune systems are among those most at risk for the disease.
Each year in the United States, pneumococcal disease kills 18,000 elderly people, according to the Centers for Disease Control and Prevention — despite available vaccines that prevent the illness in both children and adults.
Researchers at the University of Western Australia (UWA) in Perth analyzed the pneumococcal vaccine’s effects in two groups: HIV-positive people (including those successfully treated with anti-retroviral therapy) whose immune systems have been compromised, and people not infected with HIV.
Researchers took blood samples from participants before and after they were vaccinated. They discovered that in those not infected with HIV, production of antibodies was linked to T-follicular helper cells. But HIV+ participants produced far fewer of these cells, which led to lower antibody responses. Importantly, these anomalies persisted even in people successfully treated for HIV infection.
According to UWA, this is the first research showing how critical T-follicular helper cells are in producing antibodies to pneumococcal vaccines.
“Our findings may lead to the development of new ways to assess the effectiveness of such vaccines,” Laila Abudulai said in a news release. Abudulai led the study under the supervision of Sonia Fernandez and Martyn French, a professor at UWA’s Faculty of Health and Medical Sciences.
The findings offer important insights on why people with HIV infection are more vulnerable to pneumococcal pneumonia than those without HIV infection.
“Pneumococcal vaccines are very effective in preventing pneumonia but are less effective in people with compromised immune systems, particularly HIV-infected people,” French said. “The findings presented in this paper shed important light on the mechanisms of antibody production after pneumococcal vaccination and how this is adversely affected by HIV infection.”
Knowing which immune cells may be used as biomarkers to test the effectiveness of pneumococcal vaccines will benefit not only those infected with HIV, but also to anyone at increased risk of developing pneumococcal pneumonia.