Characterization of the humoral and cellular immunity induced by a recombinant BCG vaccine for the respiratory syncytial virus in healthy adults

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.

Co-administration of recombinant BCG and SARS-CoV-2 proteins leads to robust antiviral immunity

SARS-CoV-2 is the causative virus of COVID-19, which has been responsible for millions of deaths worldwide since its discovery. After its emergence, several variants have been identified that challenge the efficacy of the available vaccines. Previously, we generated and evaluated a vaccine based on a recombinant Bacillus Calmette-Guérin (rBCG) expressing the nucleoprotein (N) of SARS-CoV-2 (rBCG-N-SARS-CoV-2). This protein is a highly immunogenic antigen and well conserved among variants. Here, we tested the administration of this vaccine with recombinant N and viral Spike proteins (S), or Receptor Binding Domain (RBD-Omicron variant), plus a booster with the recombinant proteins only, as a novel and effective strategy to protect against SARS-CoV-2 variants.

METHODS

BALB/c mice were immunized with rBCG-N-SARS-CoV-2 and recombinant SARS-CoV-2 proteins in Alum adjuvant, followed by a booster with recombinant proteins to assess the safety and virus-specific cellular and humoral immune responses against SARS-CoV-2 antigens.

RESULTS

Immunization with rBCG-N-SARS-CoV-2 + recombinant proteins as a vaccine was safe and promoted the activation of CD4+ and CD8+ T cells that recognize SARS-CoV-2 N, S, and RBD antigens. These cells were able to secrete cytokines with an antiviral profile. This immunization strategy also induced robust titers of specific antibodies against N, S, and RBD and neutralizing antibodies of SARS-CoV-2.

CONCLUSIONS

Co-administration of the rBCG-N-SARS-CoV-2 vaccine with recombinant SARS-CoV-2 proteins could be an effective alternative to control particular SARS-CoV-2 variants. Due to its safety and capacity to induce virus-specific immune responses, we believe the rBCG-N-SARS-CoV-2 + Proteins vaccine could be an attractive candidate to protect against this virus, especially in newborns.

Respiratory Syncytial Virus Vaccines: Analysis of Pre-Marketing Clinical Trials for Immunogenicity in the Population over 50 Years of Age

Immunosenescence refers to age-related alterations in immune system function affecting both the humoral and cellular arm of immunity. Understanding immunosenescence and its impact on the vaccination of older adults is essential since primary vaccine responses in older individuals can fail to generate complete protection, especially vaccines targeting infections with increased incidence among the elderly, such as the respiratory syncytial virus. Here, we review clinical trials of both candidate and approved vaccines against respiratory syncytial virus (RSV) that include adults aged ≥50 years, with an emphasis on the evaluation of immunogenicity parameters. Currently, there are 10 vaccine candidates and 2 vaccines approved for the prevention of RSV in the older adult population. The number of registered clinical trials for this age group amounts to 42. Our preliminary evaluation of published results and interim analyses of RSV vaccine clinical trials indicates efficacy in older adult participants, demonstrating immunity levels that closely resemble those of younger adult participants.

A molecular perspective for the development of antibodies against the human respiratory syncytial virus

The human respiratory syncytial virus (hRSV) is the leading etiologic agent causing respiratory infections in infants, children, older adults, and patients with comorbidities. Sixty-seven years have passed since the discovery of hRSV, and only a few successful mitigation or treatment tools have been developed against this virus. One of these is immunotherapy with monoclonal antibodies against structural proteins of the virus, such as Palivizumab, the first prophylactic approach approved by the Food and Drug Administration (FDA) of the USA. In this article, we discuss different strategies for the prevention and treatment of hRSV infection, focusing on the molecular mechanisms against each target that underly the rational design of antibodies against hRSV. At the same time, we describe the latest results regarding currently approved therapies against hRSV and the challenges associated with developing new candidates.