Virus-Specific Stem Cell Memory CD8+ T Cells May Indicate a Long-Term Protection against Evolving SARS-CoV-2.

Immune memory to SARS-CoV-2 is key for establishing herd immunity and limiting the spread of the virus. The duration and qualities of T-cell-mediated protection in the settings of constantly evolving pathogens remain an open question. We conducted a cross-sectional study of SARS-CoV-2-specific CD4+ and CD8+ T-cell responses at several time points over 18 months (30-750 days) post mild/moderate infection with the aim to identify suitable methods and biomarkers for evaluation of long-term T-cell memory in peripheral blood. Included were 107 samples from 95 donors infected during the periods 03/2020-07/2021 and 09/2021-03/2022, coinciding with the prevalence of B.1.1.7 (alpha) and B.1.617.2 (delta) variants in Bulgaria. SARS-CoV-2-specific IFNγ+ T cells were measured in ELISpot in parallel with flow cytometry detection of AIM+ total and stem cell-like memory (TSCM) CD4+ and CD8+ T cells after in vitro stimulation with peptide pools corresponding to the original and delta variants. We show that, unlike IFNγ+ T cells, AIM+ virus-specific CD4+ and CD8+ TSCM are more adequate markers of T cell memory, even beyond 18 months post-infection. In the settings of circulating and evolving viruses, CD8+ TSCM is remarkably stable, back-differentiated into effectors, and delivers immediate protection, regardless of the initial priming strain.

Students' Attitudes toward COVID-19 Vaccination: An Inter-University Study from Bulgaria.

In Bulgaria, vaccination coverage against the SARS-CoV-2 virus is low. The reasons for this fact are many and varied. The aim of the present study was to establish what the attitudes towards the COVID-19 vaccination process are among students from various specialties from several Bulgarian universities. In this research, 600 students participated, divided into two groups: Doctor of Medicine (MD) students (n = 300) and non-MD students, i.e., students of specialties, such as mathematics, engineering, finance and economics, law, human sciences, etc. (n = 300). Each respondent completed a questionnaire which was divided into three parts with closed questions. The mean age of all students was 21.19 ± 1.87 years (95% CI: 20.48-21.90). The female sex dominated among the analyzed participants (sex ratio: female/male = 1/0.85). Nearly 62% (371/600) of individuals declared that they have been COVID-19 vaccinated with at least one dose (p < 0.001). Overall, 33% of the participants sought information on vaccines from video sharing platforms and 36.0% (216/600) from social media platforms. From the conducted multivariable logistic regression the odds of vaccination against COVID-19 were 6.225 times higher in individuals with a positive attitude towards these vaccines than in people with a negative attitude towards them (p < 0.001). We have found that those students who trust the international health organizations had an OR of 2.365 (p = 0.004) to be SARS-CoV-2 vaccinated. We estimated that the odds of vaccination against SARS-CoV-2 among children were 4.794 times higher in parents (students) who had been vaccinated than in non-vaccinated parents (students) (p < 0.001). Our results could support the national public health organizations, the national educational/scientific systems, and the management of Bulgarian universities in making future decisions about the field of COVID-19 control and prevention.

Clinical Characteristics of Hospitalized Patients with COVID-19 in Sofia, Bulgaria.

Introduction: SARS-CoV-2 infection is spreading around the world, including countries from Southeastern Europe. The purpose of the study was to present the clinical manifestations of COVID-19 patients admitted to the Military Medical Academy, Sofia, Bulgaria. Materials and Methods: A retrospective study was conducted for a period of 3 months from March 2020 to June 2020 on this infection in our hospital. All participants were laboratory confirmed cases of COVID-19. RT-PCR was performed for etiological diagnosis. The hospitalized patients were divided into two groups on admission, that is, nonsevere and severe. Results: One hundred thirty-eight COVID-19 patients were hospitalized and analyzed during the study period. The mean age was 52.9 years. Male was the dominant sex (sex ratio: male/female = 1/0.6). The leading clinical signs were fever, fatigue, cough, and headache. On comparative analysis of both groups (nonsevere and severe) was measured significant elevation of white blood cells (odds ratio [OR] = 1.238; p value = 0.006), C-reactive protein (OR = 1.021; p < 0.001), creatinine (OR = 1.037; p < 0.001), aspartate aminotransferase (OR = 1.014; p = 0.040), lactate dehydrogenase (OR = 1.004; p < 0.001), ferritin (OR = 1.002; p < 0.001), fibrinogen (OR = 2.028; p < 0.001), and d-dimer (OR = 2.162; p = 0.002) in severe group than in nonsevere group. Interleukin 6 was tested in 17.4% of patients and high value was found-38.6 pg/mL (95% confidence interval: 16.5-60.7). Conclusion: The first Bulgarian retrospective study of COVID-19 hospitalized patients was presented. Older age, male sex, comorbidity, and signs of dyspnea and nausea were estimated as higher risk factors for severe form. Abnormality in inflammatory markers was associated with poor progression of the illness.