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.

Background/Aim. Mediterranean spotted fever (MSF) belongs to Rickettsioses, the Spotted fever group (SFG). The causal agent is Rickettsia conorii conorii and the transmission to humans occurs through dog tick Rhipicephalus sanguineus bites. The aim of this study was to describe clinical and laboratory characteristics in patients with severe form of Mediterranean spotted fever admitted to Bulgarian university hospital in endemic region. Methods. A retrospective study was conducted at Stara Zagora University Hospital (Southeastern Bulgaria) between April 2015 and August 2016. During the analyzed period, 58 cases had clinical and laboratory data for MSF. Serological tests were applied for the etiological diagnosis. MSF-specific immunoglobulin (IgM) and IgG antibodies were detected in serum by indirect immunoenzyme assay (ELISA IgG/IgM, Vircell, Spain) ? R. conorii ELISA IgG sensitivity 85%, specificity 100% and R. conorii ELISA IgM sensitivity 94%, specificity 95%. Statistical analysis was made by MS Excel 2007 and SPSS Statistics, version 19.0. Results. Eighteen patients presented as severe forms. The predominant gender of them were males (78%) and 22% were females. The median age of the analyzed group was 55 years (range: 14? 78 years). Ten patients developed hepatic disorder while 4 had neurological signs. Laboratory data showed thrombocytopenia in 15 patients, mean value of platelet (PLT) count for the whole group was 108.6 ? 53.8 ? 109/L. Liver enzymes were elevated with mean value of aspartate aminotransferase (AST) 161.4 ? 90.1 IU/L and alanine aminotransferase (ALT) 163.9 ? 81.5 IU/L. Acute phase reactant as C-reactive protein (CRP) had mean value of 140.3 mg/L (range: 9?230 mg/L). Kidney function was impaired in some cases; the mean value of creatinine for the studied group was 134.7 ?mol/L (range: 78?313 ?mol/L) and mean value of urea was 9.6 mmol/L (range: 4.2?27.4 mmol/L). Conclusion. Bulgaria is an endemic area for tick-borne diseases. Cases of MSF are reported annually. Severe forms of MSF are not rare. Typical clinical and laboratory markers for severity should be actively searched for. Early diagnosis and proper treatment is the key to avoid complications and enable patient recovery.

Purpose:The extent of filovirus exposure and the primary sources of ebolavirus spillover to high-risk communities remains poorly characterized. In the Bwindi region of Uganda, a hotspot of mammalian biodiversity in Africa, human livelihoods are intimately connected with wildlife, creating potential for exposure to filoviruses. Our objectives were to investigate previous exposure to filoviruses in people in the Bwindi region and characterize risk factors for past exposure, including livelihoods and interactions with wildlife.Methods & Materials: Samples from 331 febrile patients presenting to healthcare facilities near the Bwindi Impenetrable Forest, Uganda, were tested using molecular (PCR) and serological assay detection techniques. Serum was tested by Western blot utilizing recombinant glycoprotein antigens for Ebola virus (EBOV), Sudan virus (SUDV), Bundibugyo virus (BDBV) and Marburg virus. Questionnaires were used to collect demographic information, travel and medical history, and data on interactions with domestic and wild animals.Results: All patients were negative for active filovirus replication by PCR. However, several patient serum samples were reactive to SUDV (4.7%), EBOV (5.3%) and BDBV (8.9%) indicating likely previous exposure to these ebolaviruses. Direct contact with duikers was a significant risk factor associated with EBOV seropositivity (OR = 5.6; P = 0.026), while hunting primates (OR = 37.5; P = < 0.001) and contact with/or consumption of cane rats (OR = 10.7; P = 0.006) were significant risk factors for SUDV seropositivity.Conclusion: People in Southwestern Uganda have suspected previous exposure to filoviruses, particularly those with a history of wildlife contact. Identification of antibodies to ebolaviruses in humans in Bwindi likely represents previous infection with SUDV, EBOV, or BDBV or infection with serologically cross-reactive low or non-pathogenic undiscovered filoviruses that also share wildlife hosts. Our findings indicate that spillover of ebolaviruses in humans, and circulation of ebolaviruses, could be more common than previously reported. The results of this study inform ongoing surveillance efforts needed to improve our understanding of the role of wildlife in spillover of ebolaviruses, not only adding to investigations of bats as likely reservoir hosts, but also indicating that secondary spillover host species remain important sources of human infection.Purpose: Fever of unknown origin (FUO) is a perplexing medical problem. The causes for FUO are more than 200 diseases. The aim