Immunogenicity of SARS-CoV-2 vaccines BBV152 (COVAXIN®) and ChAdOx1 nCoV-19 (COVISHIELD™) in seronegative and seropositive individuals in India: a multicentre, nonrandomised observational study.

Background: There are limited global data on head-to-head comparisons of vaccine platforms assessing both humoral and cellular immune responses, stratified by pre-vaccination serostatus. The COVID-19 vaccination drive for the Indian population in the age group 18-45 years began in April 2021 when seropositivity rates in the general population were rising due to the delta wave of COVID-19 pandemic during April-May 2021. Methods: Between June 30, 2021, and Jan 28, 2022, we enrolled 691 participants in the age group 18-45 years across four clinical sites in India. In this non-randomised and laboratory blinded study, participants received either two doses of Covaxin® (4 weeks apart) or two doses of Covishield™ (12 weeks apart) as per the national vaccination policy. The primary outcome was the seroconversion rate and the geometric mean titre (GMT) of antibodies against the SARS-CoV-2 spike and nucleocapsid proteins post two doses. The secondary outcome was the frequency of cellular immune responses pre- and post-vaccination. Findings: When compared to pre-vaccination baseline, both vaccines elicited statistically significant seroconversion and binding antibody levels in both seronegative and seropositive individuals. In the per-protocol cohort, Covishield™ elicited higher antibody responses than Covaxin® as measured by seroconversion rate (98.3% vs 74.4%, p < 0.0001 in seronegative individuals; 91.7% vs 66.9%, p < 0.0001 in seropositive individuals) as well as by anti-spike antibody levels against the ancestral strain (GMT 1272.1 vs 75.4 binding antibody units/ml [BAU/ml], p < 0.0001 in seronegative individuals; 2089.07 vs 585.7 BAU/ml, p < 0.0001 in seropositive individuals). As participants at all clinical sites were not recruited at the same time, site-specific immunogenicity was impacted by the timing of vaccination relative to the delta and omicron waves. Surrogate neutralising antibody responses against variants-of-concern including delta and omicron was higher in Covishield™ recipients than in Covaxin® recipients; and in seropositive than in seronegative individuals after both vaccination and asymptomatic infection (omicron variant). T cell responses are reported from only one of the four site cohorts where the vaccination schedule preceded the omicron wave. In seronegative individuals, Covishield™ elicited both CD4+ and CD8+ spike-specific cytokine-producing T cells whereas Covaxin® elicited mainly CD4+ spike-specific T cells. Neither vaccine showed significant post-vaccination expansion of spike-specific T cells in seropositive individuals. Interpretation: Covishield™ elicited immune responses of higher magnitude and breadth than Covaxin® in both seronegative individuals and seropositive individuals, across cohorts representing the pre-vaccination immune history of most of the vaccinated Indian population. Funding: Corporate social responsibility (CSR) funding from Hindustan Unilever Limited (HUL) and Unilever India Pvt. Ltd. (UIPL).

BCG revaccination in adults enhances pro-inflammatory markers of trained immunity along with anti-inflammatory pathways.

This study characterized mechanisms of Bacille Calmette-Guérin (BCG) revaccination-induced trained immunity (TI) in India. Adults, BCG vaccinated at birth, were sampled longitudinally before and after a second BCG dose. BCG revaccination significantly elevated tumor necrosis factor alpha (TNF-α), interleukin (IL)-1ß, and IL-6 in HLA-DR+CD16-CD14hi monocytes, demonstrating induction of TI. Mycobacteria-specific CD4+ T cell interferon (IFN) γ, IL-2, and TNF-α were significantly higher in re-vaccinees and correlated positively with HLA-DR+CD16-CD14hi TI responses. This, however, did not translate into increased mycobacterial growth control, measured by mycobacterial growth inhibition assay (MGIA). Post revaccination, elevated secreted TNF-α, IL-1ß, and IL-6 to "heterologous" fungal, bacterial, and enhanced CXCL-10 and IFNα to viral stimuli were also observed concomitant with increased anti-inflammatory cytokine, IL-1RA. RNA sequencing after revaccination highlighted a BCG and LPS induced signature which included upregulated IL17 and TNF pathway genes and downregulated key inflammatory genes: CXCL11, CCL24, HLADRA, CTSS, CTSC. Our data highlight a balanced immune response comprising pro- and anti-inflammatory mediators to be a feature of BCG revaccination-induced immunity.

Preliminary studies on the immunogenicity of a prime-and-trap malaria vaccine in nonhuman primates.

Development of next-generation vaccines against Plasmodium falciparum (Pf) is a priority. Many malaria vaccines target the pre-erythrocytic sporozoite (SPZ) and liver stages. These include subunit vaccines based on the Pf circumsporozoite protein (CSP) and attenuated PfSPZ vaccines. However, these strategies require 3-4 doses and have not achieved optimal efficacy against field-transmitted malaria. Prime-and-trap is a recently developed two-step heterologous vaccine strategy that combines priming with DNA encoding CSP followed by a single dose of attenuated SPZ. This strategy aims to induce CD8+ T cells that can eliminate parasites in the liver. Prior data has demonstrated that prime-and-trap with P. yoelii CSP and PySPZ was immunogenic and protective in mice. Here we report preliminary data on the immunogenicity of PfCSP prime and PfSPZ trap vaccine in rhesus macaques. This vaccine induced PfCSP-specific antibodies and T cell responses in all animals. However, response magnitude differed between individuals, suggesting further study is required.

Differences in Immune Responses in Individuals of Indian and European Origin: Relevance for the COVID-19 Pandemic.

During the coronavirus disease 2019 (COVID-19) pandemic, large differences in susceptibility and mortality due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have been reported between populations in Europe and South Asia. While both host and environmental factors (including Mycobacterium bovis BCG vaccination) have been proposed to explain this, the potential biological substrate of these differences is unknown. We purified peripheral blood mononuclear cells from individuals living in India and the Netherlands at baseline and 10 to 12 weeks after BCG vaccination. We compared chromatin accessibility between the two populations at baseline, as well as gene transcription profiles and cytokine production capacities upon stimulation. The chromatin accessibility of genes important for adaptive immunity was higher in the Indians than in the Europeans, while the latter had more accessible chromatin regions in genes of the innate immune system. At the transcriptional level, we observed that the Indian volunteers displayed a more tolerant immune response to stimulation, in contrast to a more exaggerated response in the Europeans. BCG vaccination strengthened the tolerance program in the Indians but not in the Europeans. These differences may partly explain the different impact of COVID-19 on the two populations. IMPORTANCE In this study, we assessed the differences in immune responses in individuals from India and Europe. This aspect is of great relevance, because of the described differences in morbidity and mortality between India and Europe during the pandemic. We found a significant difference in chromatin accessibility in immune cells from the two populations, followed by a more balanced and effective response in individuals from India. These exciting findings represent a very important piece of the puzzle for understanding the COVID-19 pandemic at a global level.

Polyfunctional CD4 T-cells correlating with neutralising antibody is a hallmark of COVISHIELDTM and COVAXIN® induced immunity in COVID-19 exposed Indians.

Detailed characterisation of immune responses induced by COVID-19 vaccines rolled out in India: COVISHIELDTM (CS) and COVAXIN® (CO) in a pre-exposed population is only recently being discovered. We addressed this issue in subjects who received their primary series of vaccination between November 2021 and January 2022. Both vaccines are capable of strongly boosting Wuhan Spike-specific neutralising antibody, polyfunctional Th1 cytokine producing CD4+ T-cells and single IFN-γ + CD8+ T-cells. Consistent with inherent differences in vaccine platform, the vector-based CS vaccine-induced immunity was of greater magnitude, breadth, targeting Delta and Omicron variants compared to the whole-virion inactivated vaccine CO, with CS vaccinees showing persistent CD8+ T-cells responses until 3 months post primary vaccination. This study provides detailed evidence on the magnitude and quality of CS and CO vaccine induced responses in subjects with pre-existing SARS-CoV-2 immunity in India, thereby mitigating vaccine hesitancy arguments in such a population, which remains a global health challenge.

More time to kill: A longer liver stage increases T cell-mediated protection against pre-erythrocytic malaria.

Liver stage (LS) Plasmodia mature in 2-2.5 days in rodents compared to 5-6 days in humans. Plasmodium-specific CD8+ T cell expansion differs across these varied timespans. To mimic the kinetics of CD8+ T cells of human Plasmodium infection, a two-dose challenge mouse model that achieved 4-5 days of LS antigen exposure was developed. In this model, mice were inoculated with a non-protective, low dose of late-arresting, genetically attenuated sporozoites to initiate T cell activation and then re-inoculated 2-3 days later with wild-type sporozoites. Vaccines that partially protected against traditional challenge completely protected against two-dose challenge. During the challenge period, CD8+ T cell frequencies increased in the livers of two-dose challenged mice but not in traditionally challenged mice, further suggesting that this model better recapitulates kinetics of CD8+ T cell expansion in humans during the P. falciparum LS. Vaccine development and antigen discovery efforts may be aided by using the two-dose challenge strategy.

Needle-free, spirulina-produced Plasmodium falciparum circumsporozoite vaccination provides sterile protection against pre-erythrocytic malaria in mice.

Antibodies against the Plasmodium falciparum circumsporozoite protein (PfCSP) can block hepatocyte infection by sporozoites and protect against malaria. Needle-free vaccination strategies are desirable, yet most PfCSP-targeted vaccines like RTS,S require needle-based administration. Here, we evaluated the edible algae, Arthrospira platensis (commonly called 'spirulina') as a malaria vaccine platform. Spirulina were genetically engineered to express virus-like particles (VLPs) consisting of the woodchuck hepatitis B core capsid protein (WHcAg) displaying a (NANP)15 PfCSP antigen on its surface. PfCSP-spirulina administered to mice intranasally followed by oral PfCSP-spirulina boosters resulted in a strong, systemic anti-PfCSP immune response that was protective against subcutaneous challenge with PfCSP-expressing P. yoelii. Unlike male mice, female mice did not require Montanide adjuvant to reach high antibody titers or protection. The successful use of spirulina as a vaccine delivery system warrants further development of spirulina-based vaccines as a useful tool in addressing malaria and other diseases of global health importance.

A Plasmodium falciparum ATP-binding cassette transporter is essential for liver stage entry into schizogony.

Plasmodium sporozoites invade hepatocytes and transform into liver stages within a parasitophorous vacuole (PV). The parasites then grow and replicate their genome to form exoerythrocytic merozoites that infect red blood cells. We report that the human malaria parasite Plasmodium falciparum (Pf) expresses a C-type ATP-binding cassette transporter, Pf ABCC2, which marks the transition from invasive sporozoite to intrahepatocytic early liver stage. Using a humanized mouse infection model, we show that Pf ABCC2 localizes to the parasite plasma membrane in early and mid-liver stage parasites but is not detectable in late liver stages. Pf abcc2 - sporozoites invade hepatocytes, form a PV, and transform into liver stage trophozoites but cannot transition to exoerythrocytic schizogony and fail to transition to blood stage infection. Thus, Pf ABCC2 is an expression marker for early phases of parasite liver infection and plays an essential role in the successful initiation of liver stage replication.

BCG revaccination qualitatively and quantitatively enhances SARS-CoV-2 spike-specific neutralizing antibody and T cell responses induced by the COVISHIELD™ vaccine in SARS-CoV-2 seronegative young Indian adults.

This study tested if prior BCG revaccination can further boost immune responses subsequently induced by a widely distributed and otherwise efficacious Oxford/AstraZeneca ChAdOx1nCoV-19 vaccine, referred to as COVISHIELD™, in India. We compared COVISHIELD™ induced longitudinal immune responses in 21 BCG re-vaccinees (BCG-RV) and 13 BCG-non-revaccinees (BCG-NRV), all of whom were BCG vaccinated at birth and latent tuberculosis negative, after COVISHIELD™ prime and boost with baseline samples that were collected pre-pandemic and pre-BCG revaccination. Compared to BCG-NRV, BCG-RV displayed significantly higher magnitude of spike-specific Ab and T cell responses, including a greater proportion of high responders; better quality polyfunctional CD4 and CD8 T cells that persisted and a more robust Ab and T cell response to the Delta mutant of SARS-CoV-2 highlighting greater breadth. Mechanistically, BCG adjuvant effects on COVISHIELD™ induced adaptive responses was associated with more robust innate responses to pathogen-associated-molecular-patterns through TNF-α and IL-1ß secretion. This study provides first in-depth analysis of immune responses induced by COVISHIELD™ in India and highlights the potential of using a cheap and globally available vaccine, BCG, as an adjuvant to enhance heterologous adaptive immune responses induced by COVIDSHIELD™ and other emerging vaccines.

Evidence for the heterologous benefits of prior BCG vaccination on COVISHIELD™ vaccine-induced immune responses in SARS-CoV-2 seronegative young Indian adults.

This proof-of-concept study tested if prior BCG revaccination can qualitatively and quantitively enhance antibody and T-cell responses induced by Oxford/AstraZeneca ChAdOx1nCoV-19 or COVISHIELD™, an efficacious and the most widely distributed vaccine in India. We compared COVISHIELD™ induced longitudinal immune responses in 21 BCG re-vaccinees (BCG-RV) and 13 BCG-non-revaccinees (BCG-NRV), all of whom were BCG vaccinated at birth; latent tuberculosis negative and SARS-CoV-2 seronegative prior to COVISHIELD™ vaccination. Compared to BCG-NRV, BCG-RV displayed significantly higher and persistent spike-specific neutralizing (n) Ab titers and polyfunctional CD4+ and CD8+ T-cells for eight months post COVISHIELD™ booster, including distinct CD4+IFN-γ+ and CD4+IFN-γ- effector memory (EM) subsets co-expressing IL-2, TNF-α and activation induced markers (AIM) CD154/CD137 as well as CD8+IFN-γ+ EM,TEMRA (T cell EM expressing RA) subset combinations co-expressing TNF-α and AIM CD137/CD69. Additionally, elevated nAb and T-cell responses to the Delta mutant in BCG-RV highlighted greater immune response breadth. Mechanistically, these BCG adjuvant effects were associated with elevated markers of trained immunity, including higher IL-1ß and TNF-α expression in CD14+HLA-DR+monocytes and changes in chromatin accessibility highlighting BCG-induced epigenetic changes. This study provides first in-depth analysis of both antibody and memory T-cell responses induced by COVISHIELD™ in SARS-CoV-2 seronegative young adults in India with strong evidence of a BCG-induced booster effect and therefore a rational basis to validate BCG, a low-cost and globally available vaccine, as an adjuvant to enhance heterologous adaptive immune responses to current and emerging COVID-19 vaccines.

A replication-competent late liver stage-attenuated human malaria parasite.

Whole-sporozoite vaccines engender sterilizing immunity against malaria in animal models and importantly, in humans. Gene editing allows for the removal of specific parasite genes, enabling generation of genetically attenuated parasite (GAP) strains for vaccination. Using rodent malaria parasites, we have previously shown that late liver stage-arresting replication-competent (LARC) GAPs confer superior protection when compared with early liver stage-arresting replication-deficient GAPs and radiation-attenuated sporozoites. However, generating a LARC GAP in the human malaria parasite Plasmodium falciparum (P. falciparum) has been challenging. Here, we report the generation and characterization of a likely unprecedented P. falciparum LARC GAP generated by targeted gene deletion of the Mei2 gene: P. falciparum mei2-. Robust exoerythrocytic schizogony with extensive cell growth and DNA replication was observed for P. falciparum mei2- liver stages in human liver-chimeric mice. However, P. falciparum mei2- liver stages failed to complete development and did not form infectious exoerythrocytic merozoites, thereby preventing their transition to asexual blood stage infection. Therefore, P. falciparum mei2- is a replication-competent, attenuated human malaria parasite strain with potentially increased potency, useful for vaccination to protect against P. falciparum malaria infection.

A Humanized Mouse Model for Plasmodium vivax to Test Interventions that Block Liver Stage to Blood Stage Transition and Blood Stage Infection.

The human malaria parasite Plasmodium vivax remains vastly understudied, mainly due to the lack of suitable laboratory models. Here, we report a humanized mouse model to test interventions that block P. vivax parasite transition from liver stage infection to blood stage infection. Human liver-chimeric FRGN huHep mice infected with P. vivax sporozoites were infused with human reticulocytes, allowing transition of exo-erythrocytic merozoites to reticulocyte infection and development into all erythrocytic forms, including gametocytes, in vivo. In order to test the utility of this model for preclinical assessment of interventions, the invasion blocking potential of a monoclonal antibody targeting the essential interaction of the P. vivax Duffy Binding Protein with the Duffy antigen receptor was tested by passive immunization. This antibody inhibited invasion by over 95%, providing unprecedented in vivo evidence that PvDBP constitutes a promising blood stage vaccine candidate and proving our model highly suitable to test blood stage interventions.

Dispersion Risk Associated With Surgical Debridement Devices.

INTRODUCTION: Surgical instrumentation is now available to facilitate wound debridement. The 2 primary options involve different energy applications, but both have the potential to spray. The Versajet II (Smith & Nephew, London, UK) utilizes a high-powered water jet to disrupt tissue and remove debris by means of the Venturi effect. The SonicVac (Misonix, Farmingdale, NY) is a direct-contact, low-frequency ultrasound debriding device. It delivers a high-energy ultrasound to a wound surface via a fluid medium, causing bubble cavitation, a physical effect of rapid pressure waves causing bubbles to form and implode that releases mechanical energy. OBJECTIVE: This study is designed to assess spray dispersion under ideal and challenging conditions. MATERIALS AND METHODS: The 2 aforementioned instruments were tested in a laboratory situation. Bacteria (Escherichia coli [ATCC#54288] or Staphylococcus epidermidis [RP62A]) were seeded onto separate pieces of beef steak. Culture plates were set up in a predesignated position around the specimen; the specimen was then treated for 60 seconds at a power setting of 7 and 70% irrigation (ultrasound device) or 10 (waterjet device). After 60 seconds of debridement, about 4 mm to 5 mm of muscle tissue had been removed by the ultrasound device and 2 mm to 3 mm by the waterjet. In the bony specimen, the bone was more exposed after the treatment. The ultrasound device polished but did not remove the bone. RESULTS: Both instruments performed well with minimal dispersion in the ideal setting. In beef steak with bone and grizzle, the waterjet created a lawn of bacterial spray in the plate in front of the surgeon. The ultrasound had a small number of contaminants in the same conditions. CONCLUSIONS: Both instruments can be used safely in the proper conditions, but the surgeon needs to be aware of the limitations and risks of spray dispersion.