ABSTRACT
Background: As we progress with mass vaccination against SARs-CoV- 2, there are key questions about immunogenicity of Covid vaccines that still are not answered. One of the reasons for this is the lack of suitable cellular immune methods that are easy to perform in large amount of vaccinated individuals. Conventional methods of measuring cellular and humoral immunity are complex and expensive in a pandemic situation. Here we present data about in vivo Delayed Type Hypersensitivity (DTH) results on the long-term follow-up of vaccinated immunocompetent health care workers showing that DTH is a suitable and affordable method to understand immunigenicity elicited by Covid-vaccines. This tool could be used to modify vaccine administration to optimize responses obtained in the vaccinated individuals. Method(s): Forty healthy healthcare workers accepted to participate during the vaccination schedule with a mRNA vaccine against SARS-CoV- 2. We measure the DTH cutaneous response after intradermal test of protein S of SARS-CoV- 2 at day 35 and day 200. At the same time, we perform specific anti-RBD IgG using a classic ELISA before vaccination and on days 35 and 200. Result(s): All forty individuals had a positive DTH skin response al day 35, whereas thirty-nine participants had a positive skin test at day 200 (Figure 1). Moreover, although all 40 individuals showed a humoral response of specific IgG against spike protein at day 35 considered positive, most of them have significant lower levels at day 200. Conclusion(s): DTH responsiveness has been shown to be an ideal and easy method to predict cellular immunity response to mRNA vaccines 200 days after starting immunization schaedule with mRNA vaccine for Covid-19. (Figure Presented).
ABSTRACT
The investigation of the immune response after SARS-CoV-2 infection has been the goal of many researchers worldwide. The study of humoral immune responses and in vitro T cell production after infection requires the obtaining of individualized blood samples to test the presence of antibodies or activated T cells specific for the virus. In vitro T cell studies are especially troublesome due to the need for more specialized resources often outside the daily routine of clinical laboratories. For this reason the development of a simple and objective method to achieve these T cell studies is needed. In this manuscript we reviewed the hypersensitivity reactions, the theoretical basis and the historical background of delayed type hypersensitivity (DTH) which uses the principles of use of this test in the clinical setting for the past century. In the second part of the review, we focus on COVID adaptive immune responses, to understand the differences and challenges offered by this new application of DTH to investigate immune responses elicited after infection. In the last part of the review a vision provided for the use of this test to investigate the immunogenicity elicited by the vaccines. In our opinion, the clinical guidelines of immune assessment of SARS-CoV-2-infected or vaccinated individuals should include this simple and low-cost test to measure T-cell immunity. Rationale and improved vaccination schemes could be obtained after its implementation in the routine assessment of immunity in this pandemic situation.