The detectable anti-interferon-γ autoantibodies in COVID-19 patients may be associated with disease severity.

BACKGROUND: Neutralizing anti-interferon (IFN)-γ autoantibodies are linked to adult-onset immunodeficiency and opportunistic infections. METHODS: To explore whether anti-IFN-γ autoantibodies are associated with disease severity of coronavirus disease 2019 (COVID-19), we examined the titers and functional neutralization of anti-IFN-γ autoantibodies in COVID-19 patients. In 127 COVID-19 patients and 22 healthy controls, serum titers of anti-IFN-γ autoantibodies were quantified using enzyme-linked immunosorbent assay, and the presence of autoantibodies was verified with immunoblotting assay. The neutralizing capacity against IFN-γ was evaluated with flow cytometry analysis and immunoblotting, and serum cytokines levels were determined using the MULTIPLEX platform. RESULTS: A higher proportion of severe/critical COVID-19 patients had positivity for anti-IFN-γ autoantibodies (18.0%) compared with non-severe patients (3.4%, p < 0.01) or healthy control (HC) (0.0%, p < 0.05). Severe/critical COVID-19 patients also had higher median titers of anti-IFN-γ autoantibodies (5.01) compared with non-severe patients (1.33) or HC (0.44). The immunoblotting assay could verify the detectable anti-IFN-γ autoantibodies and revealed more effective inhibition of signal transducer and activator of transcription (STAT1) phosphorylation on THP-1 cells treated with serum samples from anti-IFN-γ autoantibodies-positive patients compared with those from HC (2.21 ± 0.33 versus 4.47 ± 1.64, p < 0.05). In flow-cytometry analysis, sera from autoantibodies-positive patients could also significantly more effectively suppress the STAT1 phosphorylation (median,67.28%, interquartile range [IQR] 55.2-78.0%) compared with serum from HC (median,106.7%, IQR 100.0-117.8%, p < 0.05) or autoantibodies-negative patients (median,105.9%, IQR 85.5-116.3%, p < 0.05). Multivariate analysis revealed that the positivity and titers of anti-IFN-γ autoantibodies were significant predictors of severe/critical COVID-19. Compared with non-severe COVID-19 patients, we reveal that a significantly higher proportion of severe/critical COVID-19 patients are positive for anti-IFN-γ autoantibodies with neutralizing capacity. CONCLUSION: Our results would add COVID-19 to the list of diseases with the presence of neutralizing anti-IFN-γ autoAbs. Anti-IFN-γ autoantibodies positivity is a potential predictor of severe/critical COVID-19.

Third dose of SARS-CoV2 mRNA vaccination produces robust persistent cellular and humoral immune responses in liver transplant recipients.

Weaker responses have been described after two doses of anti-SARS-CoV2 vaccination in liver transplant recipients (LTRs). At the Italian National Institute for Infectious Diseases, 122 LTRs (84% males, median age 64 years) were tested for humoral and cell-mediated immune response after a third doses of anti-SARS-CoV2 mRNA vaccines. Humoral response was measured by quantifying anti-receptor binding domain and neutralizing antibodies; cell-mediated response was measured by quantifying IFN-γ after stimulation of T cells with SARS-CoV-2-specific peptides. Humoral and cellular responses improved significantly compared to the second vaccine dose; 86.4% of previous non-responders to the first 2 vaccine doses (N = 22) became responders. Mycophenolate mofetil-containing regimens were not associated with lower response rates to a third vaccine; shorter time since transplantation (<6 years) was associated with lower humoral and cellular responses to third vaccine. Protective antibodies against Omicron variant were detected in 60% of patients 12 weeks after third vaccine dose.

Human IRF1 governs macrophagic IFN-γ immunity to mycobacteria.

Inborn errors of human IFN-γ-dependent macrophagic immunity underlie mycobacterial diseases, whereas inborn errors of IFN-α/ß-dependent intrinsic immunity underlie viral diseases. Both types of IFNs induce the transcription factor IRF1. We describe unrelated children with inherited complete IRF1 deficiency and early-onset, multiple, life-threatening diseases caused by weakly virulent mycobacteria and related intramacrophagic pathogens. These children have no history of severe viral disease, despite exposure to many viruses, including SARS-CoV-2, which is life-threatening in individuals with impaired IFN-α/ß immunity. In leukocytes or fibroblasts stimulated in vitro, IRF1-dependent responses to IFN-γ are, both quantitatively and qualitatively, much stronger than those to IFN-α/ß. Moreover, IRF1-deficient mononuclear phagocytes do not control mycobacteria and related pathogens normally when stimulated with IFN-γ. By contrast, IFN-α/ß-dependent intrinsic immunity to nine viruses, including SARS-CoV-2, is almost normal in IRF1-deficient fibroblasts. Human IRF1 is essential for IFN-γ-dependent macrophagic immunity to mycobacteria, but largely redundant for IFN-α/ß-dependent antiviral immunity.

Low Interferon-γ Levels in Cord and Peripheral Blood of Pregnant Women Infected with SARS-CoV-2.

COVID-19 is characterized by the immune system's overreaction resulting in a 'cytokine storm', consisting in a massive release of cytokine into the bloodstream, leading to local and systemic inflammatory response. This clinical picture is further complicated in case of infection of patients with a peculiar immunological status, such as pregnancy. In this paper, we focused on Interferon-γ, which plays a pivotal immunomodulatory role in normal pregnancy and fetal development, as well as in defense against pathogens. In this study, we compared the levels of Interferon-γ and the Interferon autoantibodies of the peripheral and cord blood of pregnant women with confirmed mild COVID-19 and healthy pregnant women. The Interferon-γ was significantly lower both in the peripheral and cord blood of SARS-CoV-2-positive mothers, suggesting that infection can affect the fetal microenvironment even without severe maternal symptoms. In conclusion, further studies are needed to clarify whether lower levels of Interferon-γ due to SARS-CoV-2 infection affect the development or infection susceptibility of infants born to SARS-CoV-2-infected mothers.

Assessment of the post-SARS-CoV-2 vaccination response depending on the epidemiological status, demographic parameters and levels of selected cytokines in medical personnel.

Introduction: SARS-CoV-2 is responsible for causing the COVID-19 disease, which affected 174 million people worldwide. After vaccines were launched, the focus was on their effectiveness and the degree of their safety. Aim: The authors try to find factors that may affect the response to vaccination. Material and methods: The study was conducted in 47 adults (39 women and 8 men; age: 47.3 ±11.2). Participants were vaccinated with two doses of the Comirnaty mRNA vaccine. Each patient had a medical history taken and the concentration of specific sIgG antibodies against S1 protein and SARS-CoV-2 N protein, as well as of selected cytokines (IL-8, TGF-ß, IFN-γ) was determined before and 3 weeks after the first and second dose of the vaccine. Results: There were 18 convalescents among the respondents. A statistically significant increase in the concentration of specific sIgG S1 in subsequent determinations was observed. Higher levels of sIgG S1 were found after the first dose of the vaccine in COVID-19 convalescents. There was no statistically significant influence of age, body mass index and sex on the increase in the concentration of antibodies and the concentration of the determined cytokines. It was shown that the higher the initial TGF-ß concentration, the greater the increase in sIgG S1 after administration of the vaccine. Conclusions: Vaccination did not increase the levels of IL-8, IFN-ß and TGF-γ. A higher concentration of serum TGF-ß before vaccination correlated with the higher concentration of sIgG S1 antibodies after the first dose of the vaccine.

Glycyrrhizin as a promising kryptonite against SARS-CoV-2: Clinical, experimental, and theoretical evidences.

COVID-19 is the most devastating disease in recent times affecting most people globally. The higher rate of transmissibility and mutations of SARS-CoV-2 along with the lack of potential therapeutics has made it a global crisis. Potential molecules from natural sources could be a fruitful remedy to combat COVID-19. This systematic review highlights the detailed therapeutic implication of naturally occurring glycyrrhizin and its related derivatives against COVID-19. Glycyrrhizin has already been established for blocking different biomolecular targets related to the SARS-CoV-2 replication cycle. In this article, several experimental and theoretical evidences of glycyrrhizin and related derivatives have been discussed in detail to evaluate their potential as a promising therapeutic strategy against COVID-19. Moreover, the implication of glycyrrhizin in traditional Chinese medicines for alleviating the symptoms of COVID-19 has been reviewed. The potential role of glycyrrhizin and related compounds in affecting various stages of the SARS-CoV-2 life cycle has also been discussed in detail. Derivatization of glycyrrhizin for designing potential lead compounds along with combination therapy with other anti-SARS-CoV-2 agents followed by extensive evaluation may assist in the formulation of novel anti-coronaviral therapy for better treatment to combat COVID-19.

Modulation of the Response to Mycobacterium leprae and Pathogenesis of Leprosy.

The initial infection by the obligate intracellular bacillus Mycobacterium leprae evolves to leprosy in a small subset of the infected individuals. Transmission is believed to occur mainly by exposure to bacilli present in aerosols expelled by infected individuals with high bacillary load. Mycobacterium leprae-specific DNA has been detected in the blood of asymptomatic household contacts of leprosy patients years before active disease onset, suggesting that, following infection, the bacterium reaches the lymphatic drainage and the blood of at least some individuals. The lower temperature and availability of protected microenvironments may provide the initial conditions for the survival of the bacillus in the airways and skin. A subset of skin-resident macrophages and the Schwann cells of peripheral nerves, two M. leprae permissive cells, may protect M. leprae from effector cells in the initial phase of the infection. The interaction of M. leprae with these cells induces metabolic changes, including the formation of lipid droplets, that are associated with macrophage M2 phenotype and the production of mediators that facilitate the differentiation of specific T cells for M. leprae-expressed antigens to a memory regulatory phenotype. Here, we discuss the possible initials steps of M. leprae infection that may lead to active disease onset, mainly focusing on events prior to the manifestation of the established clinical forms of leprosy. We hypothesize that the progressive differentiation of T cells to the Tregs phenotype inhibits effector function against the bacillus, allowing an increase in the bacillary load and evolution of the infection to active disease. Epigenetic and metabolic mechanisms described in other chronic inflammatory diseases are evaluated for potential application to the understanding of leprosy pathogenesis. A potential role for post-exposure prophylaxis of leprosy in reducing M. leprae-induced anti-inflammatory mediators and, in consequence, Treg/T effector ratios is proposed.

Changes in interferon-γ release assay readout after COVID-19 vaccination: A prospective cohort study.

OBJECTIVES: Interferon-γ release assays (IGRAs) are widely used in public health practice to diagnose latent tuberculosis. During the COVID-19 pandemic and rollout of COVID-19 vaccination, it has remained unclear whether COVID-19 vaccines interfere with IGRA readouts. METHODS: We prospectively recruited healthcare workers during their annual occupational health examinations in 2021. Baseline IGRA readouts were compared with follow-up data after the participants had received two doses of COVID-19 vaccination. RESULTS: A total of 134 baseline IGRA-negative cases (92 with ChAdOx1 vaccine, 27 with mRNA-1273 vaccine, and 15 with heterologous vaccination) and seven baseline IGRA-positive cases were analyzed. Among the baseline IGRA-negative cases, there were decreased interferon-γ concentrations over the Nil (P = 0.005) and increased Mitogen-Nil (P < 0.001) values after vaccination. For TB2-Nil value, a similar trend (P = 0.057) of increase was observed. Compared with the 0.35 IU/ml threshold, the baseline and follow-up readout differences were less than |± 0.10| IU/ml over the TB1-Nil and TB2-Nil values in >90% baseline IGRA-negative cases. No significant readout difference was observed among baseline IGRA-positive cases. CONCLUSION: COVID-19 vaccination did not change IGRA interpretation in most cases. Cases showing conversion/borderline IGRA readouts should be given special consideration.

Impaired SARS-CoV-2-specific T-cell reactivity in patients with cirrhosis following mRNA COVID-19 vaccination.

Background & Aims: Cirrhosis entails elevated risk of COVID-19-associated mortality. This study determined T cell-mediated and antibody reactivity against the spike 1 (S1) protein of SARS-CoV-2 among 48 patients with cirrhosis and 39 healthy controls after mRNA COVID-19 vaccination. Methods: SARS-CoV-2-specific T-cell reactivity was measured by induced level of T cell-derived interferon-γ (IFN-γ) in blood cells stimulated ex vivo with multimeric peptides spanning the N-terminal portion of S1. S1-induced IFN-γ was quantified before and after the 1st and 2nd vaccination (BNT162b2, Pfizer-BioNTech or mRNA-1273, Moderna) alongside serum IgG against the receptor-binding domain (RBD) within S1 (anti-RBD-S1 IgG). Results: T-cell reactivity against S1 was reduced in patients with cirrhosis after the 1st (p <0.001 vs. controls) and 2nd (p <0.001) vaccination. Sixty-eight percent of patients lacked detectable S1-specific T-cell reactivity after the 1st vaccination vs. 19% in controls (odds ratio 0.11, 95% CI 0.03-0.48, p = 0.003) and 36% remained devoid of reactivity after the 2nd vaccination vs. 6% in controls (odds ratio 0.12, 95% CI 0.03-0.59, p = 0.009). T-cell reactivity in cirrhosis remained significantly impaired after correction for potential confounders in multivariable analysis. Advanced cirrhosis (Child-Pugh class B) was associated with absent or lower T-cell responses (p <0.05 vs. Child-Pugh class A). The deficiency of T-cell reactivity was paralleled by lower levels of anti-RBD-S1 IgG after the 1st (p <0.001 vs. controls) and 2nd (p <0.05) vaccination. Conclusions: Patients with cirrhosis show deficient T-cell reactivity against SARS-CoV-2 antigens along with diminished levels of anti-RBD-S1 IgG after dual COVID-19 vaccination, highlighting the need for vigilance and additional preventative measures. Clinical trial registration: EudraCT 2021-000349-42. Lay summary: T cells are a pivotal component in the defence against viruses. We show that patients with cirrhosis have impaired SARS-CoV-2-specific T-cell responses and lower antibody levels after mRNA vaccination against COVID-19 compared with healthy controls. Patients with more advanced liver disease exhibited particularly inferior vaccine responses. These results call for additional preventative measures in these patients.

Vaccine-induced humoral response against SARS-CoV-2 dramatically declined but cellular immunity possibly remained at 6 months post BNT162b2 vaccination.

To evaluate vaccine-induced humoral and cell-mediated immunity at 6 months after completion of two doses of BNT162b2 vaccination, immunoglobulin G against SARS-CoV-2 spike protein (SP IgG), 50% neutralizing antibody (NT50), and spot-forming cell (SFC) counts were evaluated by interferon-γ releasing ELISpot assay of 98 healthy subjects (median age, 43 years). The geometric mean titers of SP IgG and NT50 decreased from 95.2 (95% confidence interval (CI) 79.8-113.4) to 5.7 (95% CI 4.9-6.7) and from 680.4 (588.0-787.2) to 130.4 (95% CI 104.2-163.1), respectively, at 3 weeks and 6 months after the vaccination. SP IgG titer was negatively correlated with age and alcohol consumption. Spot-forming cell counts at 6 months did not correlate with age, gender, and other parameters of the patients. SP IgG, NT50, and SFC titers were elevated in the breakthrough infected subjects. Although the levels of vaccine-induced antibodies dramatically declined at 6 months after vaccination, a certain degree of cellular immunity was observed irrespective of the age.

Ruxolitinib attenuates secondary injury after traumatic spinal cord injury.

Excessive inflammation post-traumatic spinal cord injury (SCI) induces microglial activation, which leads to prolonged neurological dysfunction. However, the mechanism underlying microglial activation-induced neuroinflammation remains poorly understood. Ruxolitinib (RUX), a selective inhibitor of JAK1/2, was recently reported to inhibit inflammatory storms caused by SARS-CoV-2 in the lung. However, its role in disrupting inflammation post-SCI has not been confirmed. In this study, microglia were treated with RUX for 24 hours and then activated with interferon-γ for 6 hours. The results showed that interferon-γ-induced phosphorylation of JAK and STAT in microglia was inhibited, and the mRNA expression levels of pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1ß, interleukin-6, and cell proliferation marker Ki67 were reduced. In further in vivo experiments, a mouse model of spinal cord injury was treated intragastrically with RUX for 3 successive days, and the findings suggest that RUX can inhibit microglial proliferation by inhibiting the interferon-γ/JAK/STAT pathway. Moreover, microglia treated with RUX centripetally migrated toward injured foci, remaining limited and compacted within the glial scar, which resulted in axon preservation and less demyelination. Moreover, the protein expression levels of tumor necrosis factor-α, interleukin-1ß, and interleukin-6 were reduced. The neuromotor function of SCI mice also recovered. These findings suggest that RUX can inhibit neuroinflammation through inhibiting the interferon-γ/JAK/STAT pathway, thereby reducing secondary injury after SCI and producing neuroprotective effects.

Interferon-γ Release Assay for Accurate Detection of Severe Acute Respiratory Syndrome Coronavirus 2 T-Cell Response.

We investigated feasibility and accuracy of an interferon-γ release assay (IGRA) for detection of T-cell responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Whole blood IGRA accurately distinguished between convalescent and uninfected healthy blood donors with a predominantly CD4+ T-cell response. SARS-CoV-2 IGRA may serve as a useful diagnostic tool in managing the coronavirus disease 2019 pandemic.

SARS-CoV-2-specific T-cell responses after COVID-19 recovery in patients with rheumatic diseases on immunosuppressive therapy.

BACKGROUND: In patients with immune-mediated rheumatic diseases (RMD), the development of T-cell responses against SARS-CoV-2 may be impaired by either the immune disturbances associated with the disease, or by the effects of immunosuppressive therapies. We aimed at determining the magnitude of SARS-CoV-2-specific interferon (IFN)-γ-producing T-cell response after COVID-19 recovery in a cohort of patients with RMD on different immunosuppressive therapies. PATIENTS AND METHODS: 53 adult patients with inflammatory or autoimmune RMD and 61 sex and age-matched non-RMD patients with confirmed COVID-19 were included. Peripheral blood mononuclear cells were obtained and T-cell-IFN-γ antigen-specific responses against the S1 domain of the spike glycoprotein, the nucleoprotein (N) and the membrane (M) protein from SARS-CoV-2 were assessed by FluoroSpot assay. RESULTS: Patients with RMD and COVID-19 showed positive T-cells-IFN-γ responses to SARS-COV-2 antigens, in a similar proportion and magnitude as non-RMD patients at a median of 298 [151-316] and 165 [162-167] days after COVID-19 respectively. Among RMD patients 83%, 87% and 90%, and among non-RMD patients, 95%, 87% and 93% responded to S1, N and M protein respectively. Similar responses were observed in the different diagnostic and therapeutic groups, including conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs), TNF-α inhibitors, IL-17 inhibitors, rituximab, JAK inhibitors or other immunosuppressants. CONCLUSION: T-cell responses to the main SARS-CoV-2 antigens are present after COVID-19 recovery in most patients with RMD and are not impaired by immunosuppressive therapies.

Modulation of Extracellular ISG15 Signaling by Pathogens and Viral Effector Proteins.

ISG15 is a ubiquitin-like modifier that also functions extracellularly, signaling through the LFA-1 integrin to promote interferon (IFN)-γ release from natural killer (NK) and T cells. The signals that lead to the production of extracellular ISG15 and the relationship between its two core functions remain unclear. We show that both epithelial cells and lymphocytes can secrete ISG15, which then signals in either an autocrine or paracrine manner to LFA-1-expressing cells. Microbial pathogens and Toll-like receptor (TLR) agonists result in both IFN-ß-dependent and -independent secretion of ISG15, and residues required for ISG15 secretion are mapped. Intracellular ISGylation inhibits secretion, and viral effector proteins, influenza B NS1, and viral de-ISGylases, including SARS-CoV-2 PLpro, have opposing effects on secretion of ISG15. These results establish extracellular ISG15 as a cytokine-like protein that bridges early innate and IFN-γ-dependent immune responses, and indicate that pathogens have evolved to differentially inhibit the intracellular and extracellular functions of ISG15.

The potential clinical utility of measuring severe acute respiratory syndrome coronavirus 2-specific T-cell responses.

BACKGROUND: Both humoral and cell-mediated responses are associated with immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although our understanding of the potential role of T-cell responses in the context of coronavirus disease 2019 (COVID-19) is rapidly increasing, more information is still needed. OBJECTIVES: To provide an overview of the role of T-cell immunity in COVID-19, in the context of natural infection and post-vaccination, and discuss the potential utility of measuring SARS-CoV-2-specific T-cell responses, drawing on experience of the use of interferon-γ release assays (IGRAs) in tuberculosis (TB). SOURCES: PubMed articles up to 16 April 2021. CONTENT: T-cell responses can be detected very early in the course of COVID-19, earlier than the detection of antibody responses, and are correlated with COVID-19 outcome. Lower CD4+ and CD8+ T-cell counts are markers of more severe disease, longer duration of viral RNA positivity and increased mortality. In line with natural infection, SARS-CoV-2 vaccination stimulates robust T-cell responses, which probably play an important role in protection; data on long-term T-cell responses are currently limited. The utility of measuring T-cell responses is already well established in both aiding the diagnosis of TB infection using IGRAs, and evaluation of T-cell responses to TB vaccine candidates. A variety of assays have already been developed to measure SARS-CoV-2-specific T-cell responses, including IGRAs, intracellular cytokine staining and activation-induced markers. IGRAs based on SARS-CoV-2 antigens can distinguish between convalescent and uninfected healthy blood donors. IMPLICATIONS: Simple assays for measuring the quantity and function of T-cell responses may have utility in the prognostication of COVID-19, and for monitoring immune responses to SARS-CoV-2 vaccination and population-based immunity to SARS-CoV-2 variants of interest.

Role of cytotoxic T lymphocytes and interferon-γ in coronavirus infection: Lessons from murine coronavirus infections in mice.

Murine coronavirus (CoV) is a beta-CoV that infects mice by binding to carcinoembryonic antigen-related cell adhesion molecule 1. Intraperitoneal infection with the murine CoV strain JHM (JHMV) induces acute mild hepatitis in mice. While both innate and acquired immune responses play a significant role in the protection against murine CoV infection in mice, CD8+ cytotoxic T lymphocytes (CTLs) and interferon-γ are essential for viral clearance in JHMV-induced hepatitis. In addition, CoVs are characterized by high diversity, caused by mutations, recombination, and gene gain/loss. 25V16G is an immune-escape JHMV variant, which lacks a dominant CTL epitope. By evading immune responses, 25V16G establishes persistent infections, leading to granulomatous serositis in interferon-γ-deficient mice. These examples of CoV-associated pathogenesis in mice might provide useful information on other CoV infections, including coronavirus disease 2019 (COVID-19).

Interferon-γ-induced protein 10 (IP-10) and serum amyloid A (SAA) are excellent biomarkers for the prediction of COVID-19 progression and severity.

AIMS: Early diagnosis and appropriate treatment are essential in reducing the morbidity and mortality of COVID-19-infected patients. The current study aimed to measure the levels of serum IP-10 and SAA in positive COVID-19 Egyptian patients to explore their clinical values and significance in discrimination between moderate and severe COVID-19 infection and predicting the severity and prognosis of COVID-19 disease. MAIN METHODS: A total of 150 COVID-19 patients and 50 controls were enrolled into our study. Beside the routine lab work of positive COVID-19 patients; IP-10 and SAA were measured using ELISA kit. KEY FINDINGS: Our results revealed that the levels of D-dimer (2.64 ± 3.34), ferritin (494.11 ± 260.96), SAA (171.89 ± 51.96), IP-10 (405.0 ± 85.27), WBCs count (14.38 ± 6.06) and neutrophils count (79.26 ± 5.57) were highly significantly increased in severe to critically severe patients when compared with mild to moderate patients; while lymphocytes count (14.21 ± 5.13) was highly significantly decreased when compared to moderate patients. ROC curve analysis results showed that AUC from high to low was IP-10 Ëƒ SAA Ëƒ Ferritin Ëƒ D-dimer Ëƒ CRP. SIGNIFICANCE: From these results we can conclude that both IP-10 and SAA could be excellent biomarkers in discrimination between moderate and severe COVID-19 infection and predicting the severity and prognosis of COVID-19 disease.

In Ovo Delivered Toll-Like Receptor 7 Ligand, Resiquimod Enhances Host Responses against Infectious Bronchitis Corona Virus (IBV) Infection.

Toll-like receptor (TLR) 7 ligand, resiquimod, has been studied as an adjuvant and antiviral agent against several pathogens in chicken. Yet, the effectiveness of resiquimod against infectious bronchitis virus (IBV) infection has not been evaluated. In this study, we investigated the effectiveness of resiquimod delivered pre-hatch (in ovo) against IBV infection post-hatch identifying key mechanisms involved in resiquimod driven immune activation. First, we found an upregulation of interleukin (IL)-1ß and interferon (IFN)-γ mRNA levels and considerable expansions of macrophage and cluster of differentiation (CD) 8α+ T cell populations in lungs of chicken as early as day one post-hatch, following pre-hatch delivery of resiquimod. Second, we observed that resiquimod was able to act as an adjuvant when resiquimod was delivered pre-hatch along with an inactivated IBV vaccine. Finally, when the resiquimod pretreated one-day-old chickens were infected with IBV, reduction in viral shedding via oral and fecal routes was observed at 3 days post- infection. Overall, this study shows that the pre-hatch delivered resiquimod increases cell-mediated immune responses in lungs with an advantage of reduction in IBV shedding.