People taking methotrexate had low antibody responses after the first dose of the Pfizer-BioNTech mRNA COVID-19 vaccine, but did show evidence of T-cell–mediated immune responses, findings from a small study show.
The common immunosuppressant has previously been linked to poor antibody responses to mRNA COVID-19 vaccines, but this appears to be the first study to look at T-cell responses in people taking methotrexate.
The study findings were presented online July 11 at the 31st European Congress of Clinical Microbiology & Infectious Diseases and published in The Lancet Rheumatology.
“These findings indicate that seroconversion alone might not adequately reflect vaccine immunogenicity in individuals with immune-mediated inflammatory diseases receiving therapeutic immunosuppression, and caution against routine use of seroconversion data in isolation in clinical practice,” Satveer K. Mahil, MBBChir, PhD, from St. John’s Institute of Dermatology, Guy’s and St. Thomas’ NHS Foundation Trust, London, and colleagues wrote.
“When taking into account functional humoral immunity and T-cell responses, our data suggest that targeted biologics do not impair vaccine responses and provide some reassurance to this vulnerable population,” they wrote. “Notably, although methotrexate attenuated humoral immunity, cellular responses were preserved.”
Dr. Mahil and colleagues assessed 84 consecutive patients from a psoriasis specialist clinic that serves London and southeast England. Median age of the cohort was 43 years, and 85% were White. All had a confirmed psoriasis diagnosis, received the first dose of the Pfizer-BioNTech COVID-19 vaccine, and were taking either methotrexate (17 patients) or a targeted biologic (27 were taking a tumor necrosis factor inhibitor, 15 an interleukin-17 inhibitor, and 25 an IL-23 inhibitor). In addition, 17 healthy patients not receiving immunosuppression therapy who received the Pfizer-BioNTech vaccine served as the control group.
Four weeks after the study participants received their first dose of the vaccine, 78% of the immunosuppressed patients underwent seroconversion – producing measurable antibodies – as did 100% of the control group. Patients taking methotrexate had the lowest seroconversion rate at 47%, compared with 79% with TNF inhibitors, 83% with IL-23 inhibitors, and 100% with IL-17 inhibitors.
Participants taking methotrexate also had lower neutralizing activity against SARS-CoV-2 than control subjects and those taking a targeted biologic, who had similar levels of neutralizing activity.
All participants had low neutralizing titers against the alpha (B.1.1.7) variant.
The researchers also assessed cellular immunity, “defined as the presence of T cells secreting interferon-gamma, IL-2, or IL-21 in response to stimulation with two peptide pools spanning the entire length of the SARS-CoV-2 spike glycoprotein.”
A T-cell response was seen in 84% of participants taking immunosuppressants, including 93% of those in the methotrexate group and 69% of control subjects.
‘Some protection is better than none’
These findings regarding antibodies match what has been seen in other research, said Ignacio Sanz, MD, director of the Lowance Center for Human Immunology at Emory University, Atlanta.
It would be helpful to see antibody responses after the second doses, he added. Those data will be reported later, according to Dr. Mahil and colleagues.
“The authors make the valid point that T-cell immunity should also be measured. The information is meaningful and supports the idea that there could be protection still provided,” Dr. Sanz said in an interview, adding that it would have been helpful to see CD8 T-cell response as well.
“My message to patients, still, is that some protection is better than none, and that, indeed, protection may be afforded in different ways, including T-cell immunity, which, to the extent tested, seems to be induced,” he said. But discussion of B cells independent of their role in producing antibodies is missing.
“When it comes to B-cell responses, antibodies are the easier and more direct measurement. However, it is perfectly possible that the vaccine may fail to induce high antibody titers and still generate good B-cell immunity,” in the same way virus-specific memory B cells do, he explained. “They would not directly produce antibodies, yet they would be available for a good and quick response in the case of subsequent encounter with the virus and, incidentally, in the case of a booster dose. It is possible that the generation of antibody-producing plasma cells might be uncoupled from the generation of memory B cells.”