While vaccination induces a strong immune response against the SARS-CoV-2 virus in the majority of individuals, the approved vaccine has shown reduced efficacy in many immunocompromised individuals.
Patients being treated for blood cancer represent such a population, as their treatment regimens often damage healthy immune cells, especially B cells, in addition to malignant cells.
“In our clinic, we see many cancer patients who do not have an adequate humoral immune response after vaccination with the available SARS-CoV-2 vaccine.“Walz said.”As a result, these patients are at high risk for a severe episode of COVID-19. “
Many chemotherapy and some immunotherapies destroy B cells, the immune cells responsible for humoral responses. Currently approved SARS-CoV-2 vaccines are based primarily on humoral responses, which may be impaired in patients with B-cell deficiencies. One way to offset this is to enhance the response. response from T cells, another type of immune cell.
“T-cell immune responses against SARS-CoV-2 are of particular importance for patients with B-cell deficiency who develop very limited antibody responses after infection infection or vaccination.“, said Claudia Tandler, MSc, a PhD student at the University of Tübingen, who presented the study.
“T-cell-mediated immunity is indispensable for the development of protective antiviral responses, and previous evidence has shown that T cells can fight COVID-19 even in the absence of neutralizing antibodies. peace.. “
Tandler explains that designing a vaccine to stimulate T cells, requires careful selection of SARS-CoV-2 antigens — tiny bits of virus protein that can stimulate immune cells. .
Whereas current mRNA-based vaccines produce a larger fraction of a single protein — the mutant protein — that our cells can break down into antigens, Tandler and colleagues selected six antigens. from different parts of the virus to make up their vaccines.
CoVac-1 is a peptide vaccine, which means that the protein fragments are injected directly, rather than encoded via mRNA.
“CoVac-1-induced T-cell immunity is stronger and broader, as it targets different viral components than mRNA or adenoviral vector-based vaccines, which are limited to the mutant protein and because that is easily inactivated due to virus mutation“Tandler said.
Researchers previously tested the safety and preliminary efficacy of CoVac-1 in non-immunocompromised individuals and found that all those vaccinated with the vaccine maintained a response. robust T cells three months after vaccination, including responses against omicrons and other SARS-CoV-2 variants. concern, with minimal systemic side effects.
These results form the basis for a phase I/II clinical trial examining the vaccine’s effectiveness in immunocompromised patients.
In phase I of this trial, the researchers recruited 14 patients with B-cell deficiencies, including 12 with leukemia or lymphoma.
Patients received a single dose of CoVac-1 and were monitored for up to six months for safety and immunogenicity. Notably, 64% of the patients in this study had previously received the approved SARS-CoV-2 vaccine but failed to induce a humoral immune response.
Fourteen days after vaccination, a T-cell immune response was observed in 71 percent of patients, increasing to 93 percent of patients 28 days after vaccination.
The researchers measured the potency of the T-cell responses induced by CoVac-1 and found that they exceeded the spike-specific T-cell responses observed in patients with cell deficiency. B after mRNA vaccination.
The T-cell responses from CoVac-1 also exceed those of non-immunocompromised individuals after SARS-CoV-2 infection.
Researchers are currently preparing a phase III clinical trial to evaluate CoVac-1 in a larger population of immunocompromised individuals, and Walz hopes that the results will enable this new vaccine. protect cancer patients with B-cell deficiency from severe cases of COVID-19.
“CoVac-1 is designed to induce widespread and long-lasting SARS-CoV-2 T-cell immunity, even in immunocompromised individuals from the currently approved vaccine, and because that protects these high-risk patients from severe illness during COVID-19“Walz said.
Limitations of this study include the relatively small sample size with low racial and ethnic diversity.
Source: Medindia
