Coinfection with influenza virus and Mycoplasma pneumoniae (MP) increases mortality during influenza pandemics; however, its specific impact on Mycoplasma Pneumoniae Pneumonia (MPP) patients or animal models remains unclear. The underlying mechanisms of influenza A virus (IAV)–MP interactions are not fully understood. To investigate the causes of heightened mortality, we established a lethal sequential coinfection mouse model using H3N2 influenza and MP. Coinfection led to prolonged viral persistence, enhanced pulmonary immune cell infiltration, and significantly elevated levels of inflammatory cytokines (IL-6, CCL3, CCL4, and G-CSF; p < 0.05–0.001), culminating in severe pneumonia. Notably, coinfected mice exhibited impaired CD8+ T-cell responses (p < 0.05) and increased pulmonary IL-6 and IL-1α levels (p < 0.05) compared with the controls. Our findings demonstrate that IAV-MP coinfection induces immune-mediated lung injury, which likely contributes to the observed mortality. This study provides critical insights into the immunopathogenesis of coinfection and suggests potential therapeutic targets for managing coinfected patients.

Mycoplasma pneumoniae, a cell wall-deficient pathogen, primarily affects children and adolescents, causing Mycoplasma pneumoniae pneumonia (MPP). Following the relaxation of non-pharmaceutical interventions (NPIs) post COVID-19, there has been a global increase in MPP cases and macrolide-resistant strains. Vaccination against M. pneumoniae is being explored as a promising approach to reduce infections, limit antibiotic misuse, and prevent the emergence of drug-resistant variants. We developed an mRNA vaccine, mRNA-SP+P1, incorporating a eukaryotic signal peptide (tissue-type plasminogen activator signal peptide) fused to the C-terminal region of the P1 protein. Targeting amino acids 1288 to 1518 of the P1 protein, the vaccine was administered intramuscularly to BALB/c mice in a three-dose regimen. To evaluate immunogenicity, we quantified anti-P1 IgG antibody titers using enzyme-linked immunosorbent assays (ELISAs) and assessed cellular immune responses by analyzing effector memory T cell populations using flow cytometry. We also tested the functional activity of vaccine-induced sera for their ability to inhibit adhesion of the ATCC M129 strain to KMB17 cells. The vaccine’s protective efficacy was assessed against the ATCC M129 strain and its cross-protection against the ST3-resistant strain. Transcriptomic analysis was conducted to investigate gene expression changes in peripheral blood, aiming to uncover mechanisms of immune modulation. The mRNA-SP+P1 vaccine induces P1 protein-specific IgG antibodies and an effector memory T-cell response in BALB/c mice. Adhesion inhibition assays demonstrated that serum from vaccinated mice attenuatesthe adhesion ability of ATCC M129 to KMB17 cells. Furthermore, three doses of the vaccine confer significant and long-lasting, though partial, protection against the ATCC M129 strain and partial cross-protection against the ST3 drug-resistant strain. Transcriptome analysis revealed significant gene expression changes in peripheral blood, confirming the vaccine’s capacity to elicit an immune response from the molecular level. Our results indicate that the mRNA-SP+P1 vaccine appears to be an effective vaccine candidate against the prevalence of Mycoplasma pneumoniae.

Background: The serotype 2 oral poliovirus vaccine (OPV2) can revert to regain wild-type neurovirulence and spread, causing the emergence of vaccine-derived poliovirus (VDPV2) and immunodeficiency-related vaccine-derived polioviruses (iVDPVs). In the United States, testing carried out by the CDC of type II iVDPV (iVDPV2) with human immune serum from the vaccine has shown that the presence of the virus poses a threat to eradication efforts. Methods: We analyzed the major neutralization sites of VP1, VP2, and VP3 of the iVDPV using bioinformatics techniques and homology modeling (SWISS-MODEL). The three amino acid residues 679, 680, and 141 of the P1 region changed, which had an impact on the spatial conformation of the viral-neutralizing site. We tested polio-vaccinated human sera and rabbit anti-Sabin II polyantibodies against a panel of iVDPV pseudoviruses. Results: The results demonstrated that the serum’s capacity to neutralize mutant pseudoviruses diminished when amino acid substitutions were introduced into the P1 encapsidated protein, particularly when 141 and 679 were mutated together. This study emphasizes the significance of continually monitoring individuals who are known to be immunocompromised and maintaining high vaccination rates in OPV-using communities.