NEW ORLEANS, La. —A new vaccine for COVID-19 may also provide increased protection for cancer patients with weak immune systems. Researchers with the American Association for Cancer Research say this new jab boosts immune cells in 93 percent of patients with different forms of the disease, including leukemia and solid lymphomas.
The new shot, CoVac-1, was developed by German scientists to fuel T-cells — specialized cells in the immune system which seek out and attack infection. It’s different from traditional vaccines which directly target specific pathogens within the body. This secondary response is vital for those with compromised immune systems.
“To our knowledge, CoVac-1 is currently the only peptide-based vaccine candidate specifically developed and evaluated for immunocompromised patients,” says senior author Professor Juliane Walz of University Hospital Tübingen in a media release.
How is the new shot different?
Approved COVID vaccines induce a robust immune response against the SARS-CoV-2 virus in most individuals. However, they have been less effective in patients with weaker immune systems. This is a major problem among patients with blood cancers, as chemotherapy and other treatments often destroy B cells. These immune cells are responsible for antibody-led responses to infections.
“In the clinic, we see many cancer patients who do not mount sufficient humoral immune responses after vaccination with available SARS-CoV-2 vaccines,” Walz says. “These patients are thus at a high risk for a severe course of COVID-19.”
COVID vaccines rely heavily on B cells. One way to compensate is to enhance the response from T-cells.
“T-cell immune responses against SARS-CoV-2 are of particular importance for patients with B-cell deficiencies, who develop very limited antibody responses after infection or vaccination,” says co-author Claudia Tandler. “T cell-mediated immunity is indispensable for developing protective antiviral responses, and previous evidence has shown that T-cells can combat COVID-19 even in the absence of neutralizing antibodies.”
Designing a vaccine to stimulate T-cells requires the careful selection of SARS-CoV-2 antigens. These are small pieces of viral proteins that can stimulate immune cells. Current mRNA-based vaccines produce a larger piece of the spike protein which hooks onto cells – which the body breaks down into antigens.
The team chose six specific antigens from different parts of the virus to make up their vaccine. CoVac-1 is a peptide vaccine, meaning the protein pieces are injected directly, rather than being encoded via mRNA.
“CoVac-1-induced T-cell immunity is far more intense and broader, as it is directed to different viral components than mRNA-based or adenoviral vector-based vaccines that are limited to the spike protein and are thus prone to loss of activity due to viral mutations,” Tandler explains.
Trials are producing great results
The researchers previously tested the safety and preliminary efficacy of CoVac-1 in individuals without immune deficiencies. They found all those receiving the vaccine maintained robust T-cell responses three months afterwards – including against Omicron and other variants of concern.
The team found only minimal side-effects among patients. The results provide the foundation for a phase I/II clinical trial testing its efficacy in immunocompromised patients. The first 14 patients with a B-cell deficiency, including 12 with leukemia or lymphoma, received a single dose of CoVac-1.
Study authors monitored them for up to six months. Notably, 64 percent had previously received an approved COVID vaccine that failed to elicit an immune response. Two weeks later after taking CoVac-1, 71 percent of participants had T-cell immune responses. That number rose to 93 percent after four weeks.
The potency exceeded spike-specific T-cell responses observed in B cell-deficient patients after vaccination with mRNA vaccines. T-cell responses from CoVac-1 also exceeded those mounted by individuals who are not immunocompromised following a COVID infection.
The researchers are currently preparing a phase III clinical trial to evaluate CoVac-1 in a larger population of immunocompromised individuals. Scientists hope the results will allow the vaccine to protect cancer patients with B-cell deficiencies from severe cases of coronavirus.
“CoVac-1 is designed to induce broad and long-lasting SARS-CoV-2 T-cell immunity, even in individuals who have impaired ability to mount sufficient immunity from a currently approved vaccine, and thus protect these high-risk patients from a severe course of COVID-19,” Prof. Walz concludes.
The team presented their findings at the AACR Annual Meeting 2022.
South West News Service writer Mark Waghorn contributed to this report.