Genomic characteristics of two most widely used BCG vaccine strains: Danish 1331 and Pasteur 1173P2

Immune correlates of early clearance of Mycobacterium tuberculosis among tuberculosis household contacts in Indonesia

Some individuals, even when heavily exposed to an infectious tuberculosis patient, do not develop a specific T-cell response as measured by interferon-gamma release assay (IGRA). This could be explained by an IFN-γ-independent adaptive immune response, or an effective innate host response clearing Mycobacterium tuberculosis (Mtb) without adaptive immunity. In heavily exposed Indonesian tuberculosis household contacts (n = 1347), a persistently IGRA negative status was associated with presence of a BCG scar, and - especially among those with a BCG scar - with altered innate immune cells dynamics, higher heterologous (Escherichia coli-induced) proinflammatory cytokine production, and higher inflammatory proteins in the IGRA mitogen tube. Neither circulating concentrations of Mtb-specific antibodies nor functional antibody activity associated with IGRA status at baseline or follow-up. In a cohort of adults in a low tuberculosis incidence setting, BCG vaccination induced heterologous innate cytokine production, but only marginally affected Mtb-specific antibody profiles. Our findings suggest that a more efficient host innate immune response, rather than a humoral response, mediates early clearance of Mtb. The protective effect of BCG vaccination against Mtb infection may be linked to innate immune priming, also termed 'trained immunity'.

Partial long-term clinical improvement after a BCG challenge in systemic lupus erythematosus-prone mice

Systemic Lupus Erythematosus (SLE) is an autoimmune disorder that causes a breakdown of immune tolerance. Current treatments mainly involve general immunosuppression, increasing the risk of infections. On the other hand, Bacillus Calmette-Guérin (BCG) has been investigated as a potential therapy for autoimmune diseases in recent years, prompting an ongoing investigation. This study aimed to evaluate the effect of BCG vaccination on early and late clinical presentation of SLE in a murine disease model. MRL/MPJ-Faslpr mice were immunized with BCG or treated with PBS as a control. The progress of the disease was evaluated at 27 days post-immunization (dpi) (early) and 56 dpi (late). Clinical parameters and proteinuria were monitored. Blood samples were collected for measurement of antinuclear antibodies (ANAs), anti-double-stranded DNA (anti-dsDNA), and cytokine determination was performed using ELISA. Samples collected from mice were analyzed by flow cytometry and histopathology. We observed a clinical improvement in BCG-treated mice, reduced proteinuria in the latter stages of the disease, and decreased TNF-α. However, BCG did not elicit significant changes in ANAs, anti-dsDNA, histopathological scores, or immune cell infiltration. BCG was only partially beneficial in an SLE mouse model, and further research is needed to determine whether the immunity induced by this vaccine can counteract lupus's autoimmune response.

The BCG vaccine and SARS-CoV-2: Could there be a beneficial relationship?

The COVID-19 disease continues to cause complications and deaths worldwide. Identifying effective immune protection strategies remains crucial to address this ongoing challenge. The Bacillus Calmette-Guérin (BCG) vaccine, developed initially to prevent pulmonary tuberculosis, has gained relevance due to its ability to induce cross-protection against other pathogens of the airways. This review summarizes research on the immunological protection provided by BCG, along with its primary clinical and therapeutic uses. It also explores the immunological features of COVID-19, the mechanisms implicated in host cell death, and its association with chronic pulmonary illnesses such as tuberculosis, which has led to complications in diagnosis and management. While vaccines against COVID-19 have been administered globally, uncertainty still exists about its effectiveness. Additionally, it is uncertain whether the utilization of BCG can regulate the immune response to pathogens such as SARS-CoV-2.

The whole genome sequence of Polish vaccine strain Mycobacterium bovis BCG Moreau

Currently, tuberculosis immunoprophylaxis is based solely on Bacillus Calmette-Guérin (BCG) vaccination, and some of the new potential tuberculosis vaccines are based on the BCG genome. Therefore, it is reasonable to analyze the genomes of individual BCG substrains. The aim of this study was the genetic characterization of the BCG-Moreau Polish (PL) strain used for the production of the BCG vaccine in Poland since 1955. Sequencing of different BCG lots showed that the strain was stable over a period of 59 years. As a result of comparison, BCG-Moreau PL with BCG-Moreau Rio de Janeiro (RDJ) 143 single nucleotide polymorphisms (SNPs) and 32 insertion/deletion mutations (INDELs) were identified. However, the verification of these mutations showed that the most significant were accumulated in the BCG-Moreau RDJ genome. The mutations unique to the Polish strain genome are 1 SNP and 2 INDEL. The strategy of combining short-read sequencing with long-read sequencing is currently the most optimal approach for sequencing bacterial genomes. With this approach, the only available genomic sequence of BCG-Moreau PL was obtained. This sequence will primarily be a reference point in the genetic control of the stability of the vaccine strain in the future. The results enrich knowledge about the microevolution and attenuation of the BCG vaccine substrains.

IMPORTANCE

The whole genome sequence obtained is the only genomic sequence of the strain that has been used for vaccine production in Poland since 1955. Sequencing of different BCG lots showed that the strain was stable over a period of 59 years. The comprehensive genomic analysis performed not only enriches knowledge about the microevolution and attenuation of the BCG vaccine substrains but also enables the utilization of identified markers as a reference point in the genetic control and identity tests of the stability of the vaccine strain in the future.

Immunogenicity of PE18, PE31, and PPE26 proteins from Mycobacterium tuberculosis in humans and mice

Introduction

The large family of PE and PPE proteins accounts for as much as 10% of the genome of Mycobacterium tuberculosis. In this study, we explored the immunogenicity of three proteins from this family, PE18, PE31, and PPE26, in humans and mice.

Methods

The investigation involved analyzing the immunoreactivity of the selected proteins using sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy donors from the TB endemic country Mozambique. Antigen-recall responses were examined in PBMC from these groups, including the evaluation of cellular responses in healthy unexposed individuals. Moreover, systemic priming and intranasal boosting with each protein, combined with the Quil-A adjuvant, were conducted in mice.

Results

We found that all three proteins are immunoreactive with sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy controls. Likewise, antigen-recall responses were induced in PBMC from all groups, and the proteins stimulated proliferation of peripheral blood mononuclear cells from healthy unexposed individuals. In mice, all three antigens induced IgG antibody responses in sera and predominantly IgG, rather than IgA, responses in bronchoalveolar lavage. Additionally, CD4+ and CD8+ effector memory T cell responses were observed in the spleen, with PE18 demonstrating the ability to induce tissue-resident memory T cells in the lungs.

Discussion

Having demonstrated immunogenicity in both humans and mice, the protective capacity of these antigens was evaluated by challenging immunized mice with low-dose aerosol of Mycobacterium tuberculosis H37Rv. The in vitro Mycobacterial Growth Inhibition Assay (MGIA) and assessment of viable bacteria in the lung did not demonstrate any ability of the vaccination protocol to reduce bacterial growth. We therefore concluded that these three specific PE/PPE proteins, while immunogenic in both humans and mice, were unable to confer protective immunity under these conditions.