NEW ORLEANS—Immunizing patients on B cell–depleting therapies against influenza using the inactivated virus vaccine may be beneficial, according to a report presented at the 31st Annual Meeting of the Consortium of Multiple Sclerosis Centers. “Creating virus-specific T cell immunity and boosting highly cross-reactive memory T cells from prior exposures to influenza are valuable in reducing the severity of the infection,” said Elena Grebenciucova, MD, and Eric Williamson, MD, of the Multiple Sclerosis Division of the Perelman Center for Advanced Medicine at the University of Pennsylvania in Philadelphia.
The use of B cell–depleting therapies in patients with multiple sclerosis, neuromyelitis optica, and other inflammatory disorders raises a clinical dilemma. Given that the ability to generate an adequate protective antibody response is severely impaired due to B-cell depletion, is it still beneficial to immunize patients using the inactivated influenza vaccine? The practice of vaccinating patients on B cell–depleting therapies is not universal among neurologists. Many assume that the practice has no benefit and choose not to vaccinate their patients. However, antibody-mediated immune responses are not the only part of the immune system that helps control influenza infection. T cell–mediated immunity, although affected by the absence of B cells in many complex ways, is not abolished, and may offer protection, limit severity of the disease, and reduce influenza-associated morbidity.
Drs. Grebenciucova and Williamson conducted a literature review and analysis to provide a mechanistic rationale for immunizing against influenza in patients on B cell–depleting therapies.
In 2008, Stambas et al reported that virus-specific CD8+ T effector cells are important in clearing influenza infection. They also found that CD4+ T memory cells are critical in maintaining virus-specific CD8+ memory responses. Influenza vaccine helps prime naïve T cells and generates virus-specific T cells. Vaccinating also can boost pre-existent influenza-specific memory T cells, which, unlike the specific antibodies, are effective against various strains of the virus.
Dolphi et al. showed that memory T cell CD8+ and CD4+ epitopes cross-react with internal viral protein sequences (matrix [M] and nucleoprotein [NP]) that are highly conserved among various influenza strains, and thus may offer protection even when the antibody response is either inadequate or directed against the wrong strain of the virus.
A study by Sridhar et al conducted in the setting of the 2009 H1N1 pandemic highlighted the importance of cross-reactive cellular immunity by evaluating CD8+ T cell responses prior to, during, and after the influenza infection and showed that those with pre-existent CD8+ T cells specific for highly conserved internal viral proteins experienced a less severe illness, despite the absence of neutralizing antibodies.
Wilkinson et al and McElhaney et al also showed that even in the setting of inadequate antibody responses, virus-specific T cell–mediated immunity against influenza virus offers protection and may reduce morbidity.
Suggested Reading
McElhaney JE, Kuchel GA, Zhou X, et al. T-cell immunity to influenza in older adults: a pathophysiological framework for development of more effective vaccines. Front Immunol. 2016;7:41.
Sridhar S, Begom S, Bermingham A, et al. Cellular immune correlates of protection against symptomatic pandemic influenza. Nat Med. 2013;19(10):1305-1312.
Stambas J, Guillonneau C, Kedzierska K, et al. Killer T cells in influenza. Pharmacol Ther. 2008;120(2):186-196.
Wilkinson TM, Li CK, Chui CS, et al. Preexisting influenza-specific CD4+ T cells correlate with disease protection against influenza challenge in humans. Nat Med. 2012;18(2):274-280.