People infected with the Human Immunodeficiency Virus (HIV) lose immunity to smallpox even after much of their immune system is restored with drug therapy, according to a study which may lead to new interventions against opportunistic infections in HIV patients.
According to the researchers, including those from Oregon Health & Science University in the US, this condition called HIV-associated immune amnesia may explain why patients with AIDS tend to have shorter lives on average than their HIV-negative counterparts despite being on drug therapy.
The study, published in the Journal of Infectious Diseases, compared the immune system’s T-cell, and antibody responses of a total of 100 HIV-positive and HIV-negative women who were vaccinated against smallpox in their youth.
Based on the findings, the researchers said the immune systems of HIV-positive women who were on antiretroviral drug therapy had a limited response when their blood was exposed to the ‘vaccina virus’ used in the smallpox vaccine.
They said those vaccinated against smallpox, normally have CD4 T cells that remember the virus and respond in large numbers when they’re exposed again. Earlier studies had revealed that the these immune cells specific to the smallpox virus are maintained for up to 75 years after vaccination.
But in the current study, despite antiretroviral therapy boosting CD4 T cell counts in HIV-positive patients, they were susceptible to smallpox infection.
According to the scientists, this indicates that while antiretroviral therapy may boost total T cell counts overall, it doesn’t recover virus-specific T cells generated from prior childhood vaccinations.
The research team plans to evaluate whether the same findings apply for HIV-infected men, and if people living with HIV also lose immune memory to other diseases.