MRSA virulence-factor peptide combination shows strongest immune-response profile in single-donor burn-patient cell study

In an exploratory ex vivo study using peripheral blood mononuclear cells from one burn patient with confirmed methicillin-resistant Staphylococcus aureus bacteremia, the peptide combination A2-B-H produced the strongest overall immune-response profile across 13 measured endpoints. The study-specific integrated immunological score ranked A2-B-H first at 16.3 out of 20, ahead of A1-H at 10.8 and A1-B-H at 10.1. The experiment did not test infection prevention, clinical protection or vaccine efficacy.

The two-phase study combined computational peptide screening with 72-hour stimulation of the donor’s cells. The donor was a 38-year-old man with a mid-deep dermal burn covering 35% of total body surface area. He was enrolled on day 14 after injury, and MRSA was documented through blood culture and antimicrobial-susceptibility testing. His PBMC preparation had 96.8% viability and a recorded yield of 2.1 × 10^7 cells per millilitre.

For the computational phase, investigators screened S. aureus and MRSA reference sequences and a nonredundant pangenome dataset containing 1,038 GenBank genomes. BLASTP criteria of at least 85% identity, a bit score of at least 150 and an E-value no greater than 1 × 10−5 were used to prioritize conserved targets. Linear B-cell epitope predictions, antigenicity, allergenicity, toxicity and three-dimensional surface-accessibility analyses then supported selection of four peptides: A1 and A2 from adhesin-related sequences, B from a biofilm-associated protein, and H from hyaluronidase. All four were predicted to be non-toxic and non-allergenic, and their selected regions were modelled as surface accessible.

The four peptides were synthesised at greater than 95% purity and applied individually and in eight combinations to PBMCs. Each condition used 1 × 10^6 cells per well and five technical replicate wells from the same donor preparation, with unstimulated cells serving as the negative control. Because every peptide component was supplied at 5 µg/mL, formulations containing more peptides also had a higher total peptide concentration, an important constraint when comparing combinations.

Flow cytometry was used to assess marker-defined immune populations after 72 hours, while ELISA measured IL-4, IFN-γ, total IgG, IL-2, IL-12 and TNF-α in culture supernatants. The reported immune-population measures included CD33+CD38+ myeloid cells, CD56+CD38+ cells, total CD3+ T cells, the CD3+CD16+ T-cell-associated subset, total CD20+ B cells and the CD19+CD20+CD38− B-cell phenotype. Total IgG was treated as a general humoral readout rather than evidence of peptide-specific antibodies.

A2-B-H generated several of the study’s strongest measured responses. The CD33+CD38+ myeloid phenotype reached 12.32%, a 73% increase from the 7.11% control value, and CD20+ B-cell frequency reached 42.36%, 42% above control. A2-B-H also produced the highest IL-4 concentration among the tested conditions at 1.38 pg/mL, compared with 1.01 pg/mL in the control, a 37% increase. Total CD3+ T-cell frequency remained comparable with control under A2-B-H, while A1-B-H produced the highest CD56+CD38+ phenotype at 13.20%, 21.4% above control.

Other combinations led specific endpoints rather than the overall ranking. A1-H produced the highest CD3+CD16+ subset, increasing it by 43%, and the highest TNF-α concentration at 4.11 pg/mL, 65% above the 2.49 pg/mL control. A2-B generated the highest IL-2 concentration at 1.01 pg/mL, twice the 0.50 pg/mL control. A2-H produced the highest total IgG concentration at 8.71 ng/mL, 31% above control, followed by A1 at 7.97 ng/mL, 20% above control. By contrast, IL-12 remained between 11.20 and 11.79 pg/mL across treatment groups, and IFN-γ ranged from 1.01 to 1.32 pg/mL; neither showed a statistically significant difference from control.

Adding all four peptides did not consistently improve the response profile. The A1-A2-B-H formulation scored 4.5 out of 20, below A2-B-H, and was associated with lower CD33+CD38+ and total IgG responses as well as an approximately 47% reduction in total CD3+ frequency relative to control. These observations show that the larger formulation did not dominate the three-peptide combination under the tested conditions, although the fixed 5 µg/mL dose for each component prevented a clean separation of peptide number from total dose.

The findings remain limited by the use of one biological donor and technical replication rather than independent participants. Statistical comparisons were conducted across 13 exploratory endpoints without an additional multiplicity adjustment across endpoints, and the integrated score used study-defined domain weights and significance multipliers for candidate ranking rather than as an efficacy measure. The results therefore identify A2-B-H as the leading candidate within this particular experiment for subsequent functional and translational validation, but they do not establish protection against MRSA, demonstrate vaccine performance, measure peptide-specific antibody function or show direct antimicrobial activity.

Subject of Research: Single-donor ex vivo evaluation of MRSA virulence-factor peptide combinations in burn-associated bacteraemia

Article Title: Exploratory immunoinformatic and single-donor ex vivo evaluation of methicillin-resistant Staphylococcus aureus virulence-factor peptide combinations in burn-associated bacteraemia: Implications for MRSA vaccine development

Article References: Arviansyah, Sumarno, Mustamsir, E., Ratridewi, I., Barlianto, W., & Santosaningsih, D. (2026). Exploratory immunoinformatic and single-donor ex vivo evaluation of methicillin-resistant Staphylococcus aureus virulence-factor peptide combinations in burn-associated bacteraemia: Implications for MRSA vaccine development. Pharmacia, 73, Article e196054. https://doi.org/10.3897/pharmacia.73.e196054

Image Credits: AI Generated

DOI: 10.3897/pharmacia.73.e196054

Keywords: MRSA, burn-associated bacteraemia, peptide combinations, ex vivo PBMC study, immunoinformatics, immune-response profiling, virulence factors, single-donor research, A2-B-H, Exploratory, immunoinformatic, single-donor