T-B coculture assay for functional analysis of antigen-specific memory CD4+ T cells.

The B cell "help" function of CD4+ T cells is critical in establishing the humoral arm of adaptive immunity. Here, we present a protocol to measure the "help" function of antigen-specific memory T cells using an autologous T-B coculture supplemented with monocytes. We describe steps for cell preparation, human cell sorting, coculture, and a flow cytometry-based assessment of B cell outputs. This protocol demonstrates enhanced sensitivity and proves useful in evaluating T-B collaboration in various contexts of health and disease. For complete details on the use and execution of this protocol, please refer to Ansari et al.1.

Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Including Matched Sibling and Alternate Donor Transplants - Adaptations and Outcomes From a Tertiary Care Government Institute in India.

OBJECTIVE: To report the outcomes of pediatric patients who underwent allogeneic hematopoietic stem cell transplant (HSCT) in single rooms without high-efficiency particulate air (HEPA) filters, laminar air flow or positive pressure at our centre and discuss the adaptations of a high-volume government centre. METHODS: Data of the first 20 children who underwent allogeneic HSCT between May 2019 and July 2023 in adaptive settings were reviewed retrospectively. All patients were managed in in single rooms without HEPA filters, positive pressure or laminar air flow. Supportive care in the form of antimicrobial prophylaxis, veno-occlusive disease prophylaxis, anti-epileptics (with busulfan) and irradiated blood products were provided. Trained manpower including multi-specialty consultations were readily available. All complications including infections were managed as per standard guidelines. RESULTS: The median (range) of children included was 6 (1-20) years. For eight patients we used alternate donors. The mean (SD) time to neutrophil and platelet engraftment were 17.0 (8.07) days and 18.8 (10.1) days, respectively. The mean (SD) time to discharge from the hospital was 30.9 (10.04) days. There were no deaths within 30 days. Six children each developed acute and chronic graft-versus-host disease (GVHD). The overall survival at a median follow-up of 292 days was 70% (n = 14). CONCLUSION: With certain adaptations in the existing infrastructure in resource-limited settings, allogeneic HSCT can be performed with good outcomes, provided experienced, dedicated and adequate personnel, comprehensive supportive care, multidisciplinary consultative support and isolation are provided.

Autologous hematopoietic stem cell transplant at a tertiary care centre in India: achieving comparable outcomes with adaptations.

Autologous stem cell transplantation (ASCT) is the standard treatment for many high-risk solid tumors. Patients undergoing ASCT should be managed in a dedicated hematopoietic stem cell transplantation (HSCT) unit with isolation rooms, high-efficiency particulate air (HEPA) filters, and positive pressure. We report the outcomes of the first 20 pediatric patients who underwent ASCT in isolation rooms with no HEPA filters or positive pressure. Moreover, the isolation rooms were not part of a dedicated HSCT unit. Data from 20 patients were analyzed. All patients included in the study underwent ASCT after harvest and cryopreservation of the hematopoietic stem cells (HSC). Furthermore, all patients also underwent myeloablative conditioning. The most common indications for ASCT included high-risk neuroblastoma (HR-NB) (n=9) and refractory/relapsed Hodgkin's lymphoma (HL) (n=6). The median CD-34 positive HSC administered was 4.5 (0.8-21.9) million per kg. The median time to neutrophil and platelet engraftment was 16.5 (10-35) and 19 (10-87) days, respectively. Additionally, only one transplant-related mortality was observed and the mean time to discharge from the hospital was 27.6+8.3 days. The overall survival for all our patients was 75% at a median follow-up of 33.2 months (15 out of 20 patients survived), and the disease-free survival was 60% (median follow-up, 28.4 months). The overall survival for the patients with HL was 85.7% at a median of 45.3 months and for the HR-NB was 66.7% at a median of 34.9 months. This study provides evidence that ASCT can be safely performed in isolation rooms without HEPA filters and positive pressure if expertise and supportive care are available. In settings with limited resources, such a model could help establish low-cost HSCT units.

Anti-factor B antibodies in atypical hemolytic uremic syndrome.

BACKGROUND: The etiology of atypical hemolytic uremic syndrome (aHUS) is unknown in 30-40% of patients. Anti-factor B (FB) antibodies are reported in C3 glomerulopathy (C3G) and immune-complex membranoproliferative glomerulonephritis (IC-MPGN), though not in aHUS. METHODS: We screened patients < 18-year-old from cohorts of aHUS and C3G/idiopathic IC-MPGN. Anti-FB IgG antibodies were measured by ELISA and confirmed by Western blot. Normative levels were based on antibody levels in 103 healthy blood donors. RESULTS: Prevalence of anti-FB antibodies was 9.7% (95% CI 6.1-14.5%; n = 21) in 216 patients with aHUS, including 11.5% (95% CI 6.4-18.5%; n = 14) in anti-FH associated aHUS and 11.8% (95% CI 4.4-23.9%; n = 6) in patients without a definitive genetic or autoimmune etiology. Patients with significant genetic variants did not show anti-FB antibodies. In patients with concomitant anti-FB and anti-FH antibodies, median anti-FH titers were higher (11,312 AU/mL vs. 4920 AU/mL; P = 0.04). Anti-FB antibody titer correlated with disease severity (hemoglobin and platelets; P < 0.05), declined following plasma exchange and increased during relapse. While 4/64 patients with C3G (6.3%) and 1/17 with IC-MPGN showed anti-FB antibodies, titers were higher in aHUS (544.8 AU/mL vs. 1028.8 AU/mL; P = 0.003). CONCLUSION: Anti-FB antibodies are present in 6-10% of patients with aHUS and C3G/IC-MPGN, with higher titers in the former. The diagnostic and therapeutic implication of anti-FB antibodies in aHUS needs confirmation and further studies. The study shows propensity for autoantibody generation and co-existence of multiple risk factors for aHUS in Indian children.

Abbreviated protocol of plasma exchanges for patients with anti-factor H associated hemolytic uremic syndrome.

BACKGROUND: Plasma exchanges (PEX) and immunosuppression are the cornerstone of management of anti-factor H (FH) antibody-associated atypical hemolytic uremic syndrome (aHUS), particularly if access to eculizumab is limited. The duration of therapy with PEX for anti-FH aHUS is empirical. METHODS: We compared the efficacy of abbreviated PEX protocol (10-12 sessions) in a prospective cohort of patients diagnosed with anti-FH aHUS (2020-2022), to standard PEX protocol (20-22 sessions) in a historical cohort (2016-2019; n = 65). Efficacy was defined as 70% decline in anti-FH titers or fall to ≤ 1300 AU/ml at 4 weeks. Patients in both cohorts received similar immunosuppression with oral prednisolone, IV cyclophosphamide (5 doses) and mycophenolate mofetil. Outcomes included efficacy, rates of hematological remission and adverse kidney outcomes at 1, 3 and 6 months. RESULTS: Of 23 patients, 8.2 ± 2.1 years old enrolled prospectively, two were excluded for significant protocol deviation. PEX was abbreviated in 18/21 (86%) patients to 11.5 ± 3.3 sessions. Abbreviation failed for lack of hematological remission by day 14 (n = 2) and persistent neurological manifestations (n = 1). All patients in whom PEX was abbreviated achieved > 70% reduction in anti-FH titers at day 28. The percentage fall in anti-FH titers was similar for the abbreviated vs. standard PEX protocols at 1, 3 and 6 months. At last follow-up, at median 50 months and 25 months for standard and abbreviated cohorts, the estimated GFR was similar at 104.8 ± 29.1 vs. 93.7 ± 53.4, respectively (P = 0.42). CONCLUSION: Abbreviation of the duration of PEX is feasible and efficacious in reducing anti-FH titers. Short-term outcomes were comparable in patients managed by abbreviated and standard PEX protocols.

Efficacy and safety of plerixafor in pediatric cancer patients undergoing peripheral blood stem cell harvest for autologous hematopoietic stem cell transplant.

Plerixafor for peripheral blood hematopoietic stem cell (PB HSC) mobilization in children undergoing autologous hematopoietic stem cell transplantation is primarily used following failure of the initial mobilization attempt. Data on plerixafor use in pediatric patients are limited. This retrospective study conducted at a single tertiary care center in India, details the efficacy and safety of plerixafor for 10 children with relapsed/refractory solid tumors or lymphomas. High risk neuroblastomas (HR NB) underwent autologous HSCT as part of consolidation. Plerixafor was administered at a dose of 240 µg/kg body weight of the recipient, subcutaneously, approximately 11-12 h prior to harvest. Ten patients (eight males, two females), with a median age of 8 years (range 2-18 years), received plerixafor prior to PB HSC harvest. All patients were administered granulocyte colony stimulating factor (GCSF) before the administration of plerixafor. The median CD 34 count for all patients pre-plerixafor was 29/µL, nine patients exhibited higher CD 34 post plerixafor (median of 148/µL). In nine patients, the values of the CD 34 count and total leukocyte count (TLC) of the harvested product were available, and in all cases, we achieved a good yield. All patients in this study were heavily chemotherapy pre-treated, and the use of plerixafor resulted in a satisfactory yield of peripheral blood stem cells. No side effects were observed.

A randomized controlled trial to explore the safety and efficacy of irradiated buffy-coat granulocytes in pediatric patients with febrile neutropenia.

BACKGROUND: Transfusion of granulocytes obtained by apheresis is beneficial in febrile neutropenia (FN) but expensive and time-consuming. Buffy-coat-derived granulocytes could be an alternative. We studied the efficacy and safety of the administration of irradiated buffy-coat-derived granulocytes along with the standard of care in pediatric high-risk (HR) FN. METHODS: Sixty children ≤18 years with malignancy and chemotherapy-induced HR FN were randomized to either the granulocyte transfusion (GT) arm which received irradiated buffy-coat derived granulocyte transfusion along with the standard treatment or the standard treatment (ST) arm. RESULTS: Baseline characteristics, day-to-defervescence, antibiotic duration, hospital stay, and mortality were comparable between the groups. A significant difference was seen in days to achieve absolute neutrophil count (ANC) >500/mm3 in the 2 groups: 4.5 days (3-6.5) in the GT arm v/s 8 days (4-11) in the ST arm (P=0.01). CONCLUSION: Buffy-coat-derived granulocyte transfusion was safe and led to early hematological recovery but was not associated with survival benefits. Future studies with earlier initiation in the intended dose could be undertaken to generate more evidence.

Therapeutic plasma-exchange improves short-term, but not long-term, outcomes in patients with acute-on-chronic liver failure: A propensity score-matched analysis.

BACKGROUND: Acute-on-chronic liver failure (ACLF) is associated with a high short-term mortality rate in the absence of liver transplantation. The role of therapeutic plasma exchange (TPE) in improving the outcomes of ACLF and acute decompensation (AD) is unclear. In this retrospective analysis, we aimed to determine the impact of TPE on mortality in patients with ACLF. METHODS: ACLF patients receiving TPE with standard medical treatment (SMT) were propensity score matched (PSM) with those receiving SMT alone (1:1) for sex, grades of ACLF, CLIF C ACLF scores, and the presence of hepatic encephalopathy. The primary outcomes assessed were mortality at 30 and 90 days. Survival analysis was performed using Kaplan Meier survival curves. RESULTS: A total of 1151 patients (ACLF n = 864 [75%], AD [without organ failure] n = 287 [25%]) were included. Of the patients with ACLF (n = 864), grade 1, 2, and 3 ACLF was present in 167 (19.3%), 325 (37.6%), and 372 (43.0%) patients, respectively. Thirty-nine patients received TPE and SMT, and 1112 patients received only SMT. On PSM analysis, there were 38 patients in each group (SMT plus TPE vs SMT alone). In the matched cohort, the 30-days mortality was lower in the TPE arm compared to SMT (21% vs 50%, P = .008), however, the 90-day mortality was not significantly different between the two groups (36.8% vs 52.6%, P = .166); HR, 0.82 (0.44-1.52), P = .549. CONCLUSION: TPE improves short-term survival in patients with ACLF, but has no significant impact on long-term outcomes. Randomized control trials are needed to obtain a robust conclusion in this regard.

Epidemiology of severe acute respiratory syndrome-related coronavirus 2 antibodies in healthy blood donors and their follow-up.

BACKGROUND: Asymptomatic/presymptomatic COVID-19 affected individuals who may appear healthy during blood donor screening can donate blood despite being infective. Most blood donors in India are relatives/friends/acquaintances of patients, who under peer pressure overlook the donor selection process, which can significantly impact the transfusion safety. AIMS: The prevalence of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) antibodies among blood donors was assessed, along with the possible transmissibility of SARS-CoV-2 virus in transfusion recipients of blood components prepared from sero-reactive blood donors. SETTINGS AND DESIGN: A prospective cross-sectional study was conducted among eligible blood donors from November-2020 to April 2021. METHODS: 1500 blood donors were tested for SARS-CoV-2 IgG antibodies. Sero-reactive donors were followed-up telephonically to inquire about risk factors prior to donation or appearance of COVID-19 related symptoms postdonation. Patients transfused with blood components from seroreactive donors were also followed up for posttransfusion symptoms suggestive for COVID-19. Descriptive analysis was done for the donor and patient follow-up data. RESULTS: A total of 452 (30.1%) donor were reactive, with median S/CO ratio of 2.8 (interquartile range 1.5-5.5). Risk factors such as travel, contact, or quarantine were significantly higher among reactive donors. History of diabetes and/or hypertension was associated with seroreactivity. Total 516 patients were transfused with blood components from these seroreactive donors. Three patients developed fever after transfusion, one of which was found to be PCR positive after 4 days of transfusion. CONCLUSION: Sero-reactivity rate among blood donors was lower than the general population. Optimum blood donor screening strategies can help decrease the possibility of blood collection from infected blood donors.

Inactivated whole-virion vaccine BBV152/Covaxin elicits robust cellular immune memory to SARS-CoV-2 and variants of concern.

BBV152 is a whole-virion inactivated vaccine based on the Asp614Gly variant. BBV152 is the first alum-imidazoquinolin-adjuvanted vaccine authorized for use in large populations. Here we characterized the magnitude, quality and persistence of cellular and humoral memory responses up to 6 months post vaccination. We report that the magnitude of vaccine-induced spike and nucleoprotein antibodies was comparable with that produced after infection. Receptor binding domain-specific antibodies declined against variants in the order of Alpha (B.1.1.7; 3-fold), Delta (B.1.617.2; 7-fold) and Beta (B.1.351; 10-fold). However, pseudovirus neutralizing antibodies declined up to 2-fold against the Delta followed by the Beta variant (1.7-fold). Vaccine-induced memory B cells were also affected by the Delta and Beta variants. The SARS-CoV-2-specific multicytokine-expressing CD4+ T cells were found in ~85% of vaccinated individuals. Only a ~1.3-fold reduction in efficacy was observed in CD4+ T cells against the Beta variant. We found that antigen-specific CD4+ T cells were present in the central memory compartment and persisted for at least up to 6 months post vaccination. Vaccine-induced CD8+ T cells were detected in ~50% of individuals. Importantly, the vaccine was capable of inducing follicular T helper cells that exhibited B-cell help potential. These findings show that inactivated vaccine BBV152 induces robust immune memory to SARS-CoV-2 and variants of concern that persists for at least 6 months after vaccination.

Temporal Analysis of Sequential Changes in Heart Rate Variability During Non-hypotensive Hypovolemia.

INTRODUCTION: Haemorrhage is associated with changes in the cardiac autonomic drive which begins during early stages of mild haemorrhage. The knowledge of chronology of the autonomic changes at smaller timescale during the period of haemorrhage can help identify the primary autonomic parameter which signals the institution of cardiovascular reflex mechanisms. AIM: To evaluate the heart rate variability in 2-min sequential segments with one minute overlap during and after the period of mild haemorrhage (450 ml) using blood donation as a model of acute blood loss. METHODS: 47 male blood donors who had volunteered for blood donation were recruited for the study. Continuous lead II ECG was recorded before the start of the blood donation (5 min), during the period of the blood donation (~ 5-7 min) and after blood donation (5 min). The parasympathetic and sympathetic drive to heart was estimated by measures of heart rate variability in time and frequency domain. RESULTS: A significant decrease in the parameters assessing parasympathetic drive i.e., normalised High frequency (HFn) and NN50 (Number of pairs of adjacent NN intervals differing by more than 50 ms) and pNN50 (NN50 divided by the total number of all NN Intervals) was observed during blood donation at 3-5 min, as compared to baseline. An increase in parameters associated with sympathetic drive i.e., normalised low frequency (LFn) was observed only in the post donation period at 2-3 min. A significant rise in LF/HF ratio which is a marker of sympatho vagal balance was observed at 4-5 min during blood donation when compared to baseline. CONCLUSION: The initial cardiac autonomic change during mild haemorrhage is withdrawal of parasympathetic drive, followed by an increase in sympathetic tone which occurs much later.

An efficient immunoassay for the B cell help function of SARS-CoV-2-specific memory CD4+ T cells.

The B cell "help" function of CD4+ T cells is an important mechanism of adaptive immunity. Here, we describe improved antigen-specific T-B cocultures for quantitative measurement of T cell-dependent B cell responses, with as few as ∼90 T cells. Utilizing M. tuberculosis (Mtb), we show that early priming and activation of CD4+ T cells is important for productive interaction between T and B cells and that similar effects are achieved by supplementing cocultures with monocytes. We find that monocytes promote survivability of B cells via BAFF and stem cell growth factor (SCGF)/C-type lectin domain family 11 member A (CLEC11A), but this alone does not fully recapitulate the effects of monocyte supplementation. Importantly, we demonstrate improved activation and immunological output of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific memory CD4+ T-B cell cocultures with the inclusion of monocytes. This method may therefore provide a more sensitive assay to evaluate the B cell help quality of memory CD4+ T cells, for example, after vaccination or natural infection.

Reinduction of the Temporarily Deferred Donors for Laying the Foundation of Safe and Sustainable Blood Supplies: A Review in the Indian Context.

Temporarily deferred donors are a forgotten pool of potential blood source. When dealt appropriately, they can easily be inducted back to the main stream pool of voluntary donors. Although there are multiple studies from India on the deferral rates and patterns; not much has been done with respect to the follow up of these donors and active efforts to bring them back to donate blood. In this narrative review, we discuss the impact of temporary deferral, factors affecting the return and appropriate strategies to improve the return rate of these donors.

Effects of submucosally administered platelet-rich plasma on the rate of tooth movement.

OBJECTIVES: To evaluate the effects of submucosally administered platelet-rich plasma (PRP) on the rate of maxillary canine retraction. Levels of soluble receptor activator of nuclear factor-κb ligand (sRANKL) and osteoprotegerin (OPG) in the gingival crevicular fluid (GCF) were also measured over 2 months. MATERIALS AND METHODS: This split-mouth trial involved 20 sites in 10 subjects randomly assigned to PRP (experimental) side and control side. After alignment, the freshly prepared PRP was injected submucosally distal to the experimental side maxillary canine, and retraction was performed using NiTi closed-coil springs (150 g) on 0.019 × 0.025-inch stainless steel wire. The rate of canine movement was assessed using digital model superimposition at 0, 30, and 60 days. The OPG and sRANKL were assayed using enzyme-linked immunosorbent assay from GCF collected at 0, 1, 7, 21, 30, and 60 days. RESULTS: Twenty sites were analyzed using paired t test. The rate of tooth movement increased significantly by 35% on the PRP side compared with the control side in the first month (P = .0001) and by 14% at the end of the second month (P = .015). Using the Mann-Whitney U test, OPG levels were found to be significantly decreased on the 7th (P = .003) and 30th day on the PRP side (P = .01), while sRANKL became detectable by the third week postinjection on the PRP side (P = .069). CONCLUSIONS: Submucosal injection of platelet-rich plasma significantly increased tooth movement during the 60-day observation period. Local injection of PRP significantly altered the levels of OPG and sRANKL in GCF.

Comparative evaluation of ADVIA Centaur® XP chemiluminescence system for screening of HBV, HCV, HIV and syphilis in Indian blood donors.

BACKGROUND: The introduction of chemiluminescent immunoassay (CLIA) in blood donor screening has led to a gradual replacement of enzyme-linked-immunosorbent assay (ELISA) as the former offers automation, higher sensitivity and lower turn-around-time. However, only a few CLIA platforms are used for blood donor screening in India. The present study evaluated one such newer platform viz., Adiva Centaur XP CLIA for screening of HBV, HCV, HIV and syphilis. MATERIAL AND METHODS: Prospective comparative study wherein 4843 whole blood donors were screened for HBsAg, Anti-HCV, HIV Ag-Ab and Anti-treponemal antibodies in both Advia Centaur XP and Architect i2000SR platforms. Additional tests were performed in samples which were reactive in only one of the platforms. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, false positive rate and false negative rate of both the platforms were compared. Kappa coefficient was calculated to determine the agreement between the testing platforms. RESULTS: The sensitivity of Advia Centaur platform for HBV, HCV, HIV and syphilis detection were 94.9 %, 100 %, 100 % and 100 % respectively as compared to 96.6 %, 100 %, 100 % and 100 % in Architect i2000SR platform. The specificity of both the platforms were 99.8-99.9 % for all the four tests. The agreement between the two platforms was almost perfect for HBV, HCV and syphilis testing; and fair for HIV testing. CONCLUSION: The Advia Centaur CLIA platform was found to be comparable with the Architect CLIA platform for blood donor screening. Unexpected finding was the occurrence of HBV false negatives in both the platforms, possibly due to HBsAg mutations.

Immune Memory in Mild COVID-19 Patients and Unexposed Donors Reveals Persistent T Cell Responses After SARS-CoV-2 Infection.

Understanding the causes of the diverse outcome of COVID-19 pandemic in different geographical locations is important for the worldwide vaccine implementation and pandemic control responses. We analyzed 42 unexposed healthy donors and 28 mild COVID-19 subjects up to 5 months from the recovery for SARS-CoV-2 specific immunological memory. Using HLA class II predicted peptide megapools, we identified SARS-CoV-2 cross-reactive CD4+ T cells in around 66% of the unexposed individuals. Moreover, we found detectable immune memory in mild COVID-19 patients several months after recovery in the crucial arms of protective adaptive immunity; CD4+ T cells and B cells, with a minimal contribution from CD8+ T cells. Interestingly, the persistent immune memory in COVID-19 patients is predominantly targeted towards the Spike glycoprotein of the SARS-CoV-2. This study provides the evidence of both high magnitude pre-existing and persistent immune memory in Indian population. By providing the knowledge on cellular immune responses to SARS-CoV-2, our work has implication for the development and implementation of vaccines against COVID-19.

Deterrents in recruitment of COVID-19 convalescent plasma donors: Experience from a hospital-based blood centre in India.

INTRODUCTION: Recruitment of Covid-19 convalescent plasma (CCP) donors may present as a challenge due to inexperience and differences in donor profile as compared to whole blood donation. Present study highlights the deterrents to recruiting CCP donors at a hospital based blood centre. MATERIALS AND METHODS: Potential CCP donors were contacted individually by telephone and a group approach through camp organisers from May to July 2020. Recruitment challenges were noted and deferrals of these recruited donors during screening and medical examination was obtained and analysed. RESULTS: Total 1165 potential CCP donors were contacted. Around 47% donors were lost due to challenges related to information storage and retrieval. Fear of health, family pressure, and fear of a new procedure were major reason (27.2%) for unwillingness to donate. The main reasons for deferral among potential donors were multiparity (38%) and being overage/underage (31.6%). Finally, 468 donors were recruited including 408 by individual approach and 60 by a group approach. From these absence of detectable COVID-19 antibodies were found in 15.4%. Few donors (9.0%) were deferred as they had not completed 28 days post recovery. CONCLUSION: The process of CCP donor recruitment differs from that of whole blood donation and requires an individualised approach with involvement of clinicians in the initial phases of the pandemic. A group approach targeting specific organisations could be adopted for a successful CCP collection program. There is a need to relook into some aspects of donor selection such as consideration of multiparous female donors and overage/underage donors after reviewing scientific evidence.

Seroprevalence of SARS-Coronavirus 2 among asymptomatic healthy blood donors from healthcare and non-healthcare settings: Implications for safety of blood donors and blood collection staff during blood donation.

INTRODUCTION: SARS-Coronavirus-2 pandemic has adversely affected blood supply as potential blood donors were afraid of acquiring infection in hospital settings. We aimed to compare COVID-19 seroprevalence among asymptomatic blood donors from healthcare and non-healthcare setting to analyse the difference in exposure level of each group as well as the risk of acquiring infection during the process of blood donation. MATERIAL AND METHODS: Analysis of whole blood donors tested for SARS-CoV-2 IgG antibodies was carried out after categorizing them into healthcare workers (HCW) and non-healthcare workers (NHCW). NHCW were further categorized into residents of containment and non-containment zones and seroprevalence analyzed. Seroprevalence among different ABO blood groups was also analyzed. RESULTS: 1191 blood donors were tested for SARS-CoV-2 antibodies with 9.5 % seropositivity. Significantly lower seropositivity of 3.2 % (p < 0.001) was observed among HCW as compared to 10.9 % seropositivity in NHCW. Among NHCW no difference in seropositivity was observed based on residence in containment or non-containment zone. Significantly higher (p = 0.012) seroprevalence was observed among A blood group donors (12.5 %) as compared to O blood group donors (6.8 %). CONCLUSION: Results suggests that a blood donor, in a hospital setting is less likely to be exposed to COVID-19 disease than when participating in activities of daily living. It is postulated that the lower seroprevalence among HCW as compared to NHCW reflects differences in knowledge and practice of preventive measures among these groups. The findings should instil confidence among blood donors and motivate them to donate blood without fear.

Immune memory in mild COVID-19 patients and unexposed donors from India reveals persistent T cell responses after SARS-CoV-2 infection.

Understanding the causes of the diverse outcome of COVID-19 pandemic in different geographical locations is important for the worldwide vaccine implementation and pandemic control responses. We analyzed 42 unexposed healthy donors and 28 mild COVID-19 subjects up to 5 months from the recovery for SARS-CoV-2 specific immunological memory. Using HLA class II predicted peptide megapools, we identified SARS-CoV-2 cross-reactive CD4+ T cells in around 66% of the unexposed individuals. Moreover, we found detectable immune memory in mild COVID-19 patients several months after recovery in the crucial arms of protective adaptive immunity; CD4+ T cells and B cells, with a minimal contribution from CD8+ T cells. Interestingly, the persistent immune memory in COVID-19 patients is predominantly targeted towards the Spike glycoprotein of the SARS-CoV-2. This study provides the evidence of both high magnitude pre-existing and persistent immune memory in Indian population. By providing the knowledge on cellular immune responses to SARS-CoV-2, our work has implication for the development and implementation of vaccines against COVID-19.