HIV Weakens Response to Flu Vaccine in Older Women

Older people with HIV infection have a weaker antibody response to the influenza vaccine than older people who are not HIV infected. This finding underscores the importance of influenza vaccination for everyone infected with HIV, according to a new study.

“Serologic and immunologic deficits were most frequent in old HIV-infected participants,” state the authors, led by Savita Pahwa, MD, Professor, Microbiology and Immunology, University of Miami Miller School of Medicine, in Miami, FL.

Previously, these researchers had noted similar features between the immune system of healthy, older people and of younger individuals subjected to conditions of chronic immune activation, raising the hypothesis that chronic immune activation may cause the premature aging of the immune system. Immunity to influenza is known to decrease with age, and an infection with HIV appears to make it harder for older people to develop a response to the flu vaccine, even if they are receiving therapy and their disease is well controlled with antiretroviral drugs.

Knowing that antibody responses to seasonal influenza vaccines are defective in old age and in HIV infection, Dr Pahwa and colleagues set out to study the effect of HIV on immune function in aging. They evaluated 70 HIV-infected and HIV-uninfected young and old women for B and T cellular responses before and 4 weeks after influenza vaccination.

The study included women younger than age 45 with and without HIV, and postmenopausal women older than 55 with or without HIV. The researchers also performed immunologic assessments in a subgroup of 48 women who were non-responders.

After vaccination, all of the young, uninfected women were seroprotected, but only 55% of old, infected women, 75% of old, uninfected women, and 93% of young, infected women were seroprotected.

Vaccine non-responders had reduced frequencies of memory B cells and antigen-specific antibody secreting cells post-vaccination compared with responders.

The researchers also found a correlation among frequencies of peripheral T follicular helper (pTfh) cells, memory B cell function, and influenza antibody titers. There was a negative correlation for CD4 T cell immune activation and inflammation with antibody titers and B cell function.

Supplementation with interleukin-21, which is produced by pTfh cells, boosted the immune response in all of the young patients and in the older patients without HIV, but not in the old HIV-infected vaccine non-responders.

The researchers conclude “immune activation associated with HIV infection, and impaired pTfh function heighten deficiencies in antibody responses to influenza vaccine in aging. Strategies to reduce immune activation or augment pTfh function may enhance antibody responses in the aging HIV-infected population.”

They speculate that inflammation may be the underlying mechanism in the weakened immune response among older HIV infected patients. They note that inflammation affects immune activation among older patients as well as HIV-infected patients at all ages.

Currently, the CDC recommends that people 65 and older receive a more potent version of the influenza vaccine.

The researchers published their results online January 2, 2015 in The Journal of Infectious Diseases.