Title of the proposal: Evaluation of Antimicrobial Activity of Novel De Novo Designed Synthetic Peptides Against Fish Pathogens

Title of the proposal: Evaluation of Antimicrobial Activity of Novel De Novo Designed Synthetic Peptides Against Fish Pathogens

1. Overview

Aquaculture is increasingly vital for meeting global protein demands, yet intensive practices have driven a rise in antibiotic use, leading to the spread of antimicrobial resistance (AMR). Aquaculture systems serve as “genetic hotspots” for horizontal gene transfer, aggravating the problem. Alternatives to antibiotics are urgently needed. Antimicrobial peptides (AMPs), short cationic peptides with broad-spectrum antimicrobial and immunomodulatory activity, provide a promising solution. Their ability to rapidly disrupt microbial membranes reduces the likelihood of resistance development. However, natural AMPs face limitations such as instability, toxicity, and high production costs. This project seeks to rationally design short, compositionally simple, less toxic synthetic AMPs with enhanced stability, aiming to provide an effective and sustainable alternative to antibiotics in aquaculture.

2. Confirmation of Funding, Facilities, and Ethics Approvals

Funding: This project is supported under institutional research funding (details can be included, e.g., through SKUAST-Kashmir or external grants if already sanctioned).
Facilities: The Division of Fish Genetics and Biotechnology, Faculty of Fisheries, SKUAST-Kashmir, is equipped with peptide synthesis platforms (SPPS), HPLC, CD spectroscopy, and microbiology and molecular biology laboratories required for peptide characterization, antimicrobial testing, and toxicity assays.
Ethics Approvals: All in vivo experiments involving fish will be conducted in compliance with institutional animal ethics guidelines and have received/will receive approval from the Institutional Animal Ethics Committee (IAEC) before commencement.

3. Estimated Timeline

The study spans approximately 24 months:

Months 1–4: Literature review, in-silico design of peptides.
Months 5–10: Solid-phase synthesis, purification (HPLC), characterization (MS, CD spectroscopy).
Months 11–16: In vitro antimicrobial assays (disk diffusion, MIC), bacterial-peptide interaction studies, microscopy.
Months 17–20: In vivo trials in fish models for survival, immune response, and efficacy evaluation.
Months 21–22: Toxicity assays (MTT, haemolysis).
Months 23–24: Data analysis, interpretation, and thesis/report preparation.

4. Data Sharing Commitment

The project commits to transparent and open dissemination of results.

Data generated will be shared through peer-reviewed publications, conference presentations, and submission to publicly accessible repositories (where applicable).
Negative or inconclusive results will also be reported to avoid redundancy in future research.
All findings will follow FAIR (Findable, Accessible, Interoperable, Reusable) data principles, ensuring reproducibility and accessibility for the wider scientific community.

2. Introduction

Theoretical Background

The rapid expansion of aquaculture to meet global food demands has increased dependence on antibiotics for disease management. Such practices have contributed to antimicrobial resistance (AMR) in aquatic environments, creating genetic hotspots for horizontal gene transfer among bacteria. This poses serious risks to public health and sustainable aquaculture. Antimicrobial peptides (AMPs)—short, cationic, amphipathic peptides—are promising alternatives due to their rapid membrane-disruptive mechanisms, broad-spectrum activity, and reduced likelihood of resistance development. However, natural AMPs often suffer from instability, toxicity, and high production costs. Synthetic design offers a strategy to overcome these drawbacks by creating shorter, compositionally simple, stable, and less toxic peptides suitable for aquaculture use.

Key Literature

Antibiotic misuse in aquaculture: Prophylactic and metaphylactic use has been widespread, particularly in shrimp and salmon farming (Holmstrom et al., 2003; Buschmann et al., 2012; Cabello et al., 2006, 2013).
Resistance hotspots: Aquaculture environments foster selective pressure and horizontal gene transfer, amplifying AMR risk (Kerry et al., 1995; Economou & Gousia, 2015).
AMP properties: AMPs are evolutionarily conserved molecules with broad-spectrum activity and immune-modulatory roles (Hancock, 2001; Rajanbabu & Chen, 2011).
Therapeutic challenges: AMPs face degradation by proteases, cytotoxicity at higher doses, and cost barriers (Goldman et al., 1997; Vlieghe et al., 2010; Kumar et al., 2017).
Synthetic AMPs in fish: Few studies exist, with rainbow trout hepcidin peptides showing promising activity against E. coli and Piscirickettsia salmonis depending on folding and oxidative state (Álvarez et al., 2014, 2016).

Research Questions

Can de novo designed synthetic AMPs be generated with improved stability, reduced toxicity, and strong antimicrobial activity?
Do these synthetic AMPs demonstrate effective in vitro and in vivo antimicrobial activity against common fish pathogens?
Are synthetic AMPs safe for host fish cells, with minimal cytotoxic or haemolytic effects?

Hypotheses

H1: Rationally designed short synthetic AMPs will exhibit significant antimicrobial activity against Gram-positive and Gram-negative fish pathogens.
H2: Synthetic AMPs will demonstrate greater stability under physiological conditions compared to natural AMPs.
H3: Synthetic AMPs will show reduced cytotoxicity and haemolytic activity relative to some naturally occurring AMPs.
H4: In vivo trials will confirm improved fish survival and enhanced immune responses following AMP treatment.

Importance and Impact Statement

This study addresses the urgent global challenge of antimicrobial resistance by exploring synthetic antimicrobial peptides as sustainable alternatives to antibiotics in aquaculture. Regardless of outcomes, the project will:

Provide critical insights into the design, stability, and efficacy of synthetic AMPs.
Generate foundational data for developing environmentally friendly disease-control strategies in fish farming.
Contribute to reducing reliance on antibiotics, thereby lowering the risk of AMR spread from aquaculture to human populations.
Advance the broader field of peptide therapeutics by testing practical applications in real-world aquaculture systems.

The findings will therefore have significant implications for public health, aquaculture sustainability, and innovation in peptide-based drug design.

3. Methods

Participants/Sample

Participants / Sample

Target sample: Commonly farmed freshwater fish species that are highly susceptible to bacterial infections (e.g., Danio rario (zebrafish) will be selected as model organism.
Inclusion criteria: Healthy juvenile fish (10–15 g body weight; 8–10 cm length) sourced from certified hatcheries, free from prior antibiotic exposure or visible disease symptoms.
Exclusion criteria: Fish with external lesions, abnormal swimming behavior, or prior mortality in the stock will be excluded.
Recruitment strategy: Fish will be procured in batches from local government hatcheries and acclimatized under controlled laboratory conditions for 14 days prior to experimentation.
Sample size justification: Based on previous AMP challenge trials (e.g., Kumar et al., 2017; Álvarez et al., 2016), a minimum of 30 fish per experimental group provides adequate statistical power (β = 0.8, α = 0.05) to detect medium effect sizes in survival, bacterial load, and immune response. Power analysis (G*Power 3.1, two-tailed ANOVA, effect size f = 0.25, α = 0.05, power = 0.8) suggests n = 25 per group; thus, n = 30 per group will be adopted to account for potential dropouts.

Materials and Procedures

Peptide Design and Synthesis

Short cationic AMPs will be rationally designed in silico using the APD3 and CAMPR3 databases, ensuring amphipathic structure with essential Lys/Arg and Leu/Ile/Trp/Phe residues.
Peptides will be synthesized by solid-phase peptide synthesis (SPPS, Fmoc chemistry).
Characterization will include mass spectrometry, HPLC, and Circular Dichroism (CD) spectroscopy.

Nanoparticle Conjugation

Chitosan nanoparticles will be synthesized using the ionic gelation method.
Conjugation efficiency and peptide loading will be quantified by UV–Vis spectrophotometry and FTIR spectroscopy.
Particle morphology will be assessed using dynamic light scattering (DLS) and scanning electron microscopy (SEM).

In vitro Antimicrobial Activity

Pathogens: Fish bacterial isolates (Aeromonas hydrophila, Vibrio anguillarum, Edwardsiella tarda).
Tests: Disk diffusion assay, MIC/MBC determination (broth microdilution), bacterial viability (live/dead staining), and DNA-binding capacity assays.
Molecular docking: Peptide binding to bacterial virulence proteins will be simulated to predict interaction affinity.

In vivo Challenge Experiment

Groups: Fish will be randomly assigned to (i) untreated control, (ii) nanoparticle control, (iii) free AMP treatment, (iv) nano-conjugated AMP treatment.
Infection model: Fish will be intraperitoneally injected with standardized doses of A. hydrophila (10^6 CFU/mL).
Treatments: AMP/nano-AMP formulations will be delivered via medicated feed at pre-determined doses.
Monitoring: Mortality, behavioral signs, bacterial load in tissues (kidney, liver, gills), and immune markers (lysozyme, respiratory burst, cytokine expression) will be recorded.

Toxicity Assessment

In vitro: Fish cell lines will be tested using MTT and haemolysis assays.
In vivo: Hematology (RBC, WBC counts, Hb, hematocrit), histopathology of liver/kidney will be performed to evaluate host tolerance.

Planned Analyses

Data Preprocessing

Mortality data will be corrected using Abbott’s formula.
Outliers (>3 SD from mean) will be identified and examined; if due to technical error, excluded.
Microbiological counts (CFU/mL) will be log10-transformed before statistical testing.

Statistical Tests

Objective 1 (Peptide design): Descriptive statistics for physicochemical properties; docking scores compared using one-way ANOVA.
Objective 2 (Antimicrobial efficacy):
- MIC/MBC values compared using Kruskal–Wallis test with Dunn’s post-hoc test.
- Survival curves analyzed with Kaplan–Meier estimator and log-rank test.
- Immune response parameters analyzed by two-way ANOVA (treatment × time).
Objective 3 (Toxicity):
- MTT/haemolysis data analyzed using one-way ANOVA with Tukey’s post-hoc test.
- Hematological and histological indices compared across treatment groups using MANOVA.

Hypothesis-specific Predictions

H1: Rationally designed AMPs will show significantly lower MIC values than controls (IF MIC < 25 µg/mL, THEN considered effective).
H2: Nano-conjugated AMPs will demonstrate enhanced stability and in vivo protection compared to free peptides (IF survival >70% vs. <40% in controls, THEN hypothesis supported).
H3: Designed peptides will show minimal host toxicity (IF haemolysis <10% at therapeutic concentrations, THEN considered safe).

Ethics and Data Management

Ethical Approval: Experiments will follow institutional and national guidelines for fish welfare. Approval will be obtained from the Institutional Animal Ethics Committee (IAEC). Humane handling, use of anesthetics, and defined endpoints will minimize stress and suffering.

Confidentiality: No human subjects are involved. Experimental data will be anonymized, stored on secure, password-protected servers, and accessed only by the research team.

Data Sharing: Cleaned datasets and metadata will be archived in open-access repositories. Results will be published in open-access journals. Sensitive data (e.g., peptide sequences under patent) will be embargoed until IP protection is secured.4. Pilot Data (Optional)

5. Budget

S.No.	Category	Details	Estimated Cost (USD)
1	Consumables	Peptide synthesis reagents (Fmoc kits, resins, solvents)	1,200
		Plastic ware, Nanoparticle formulation reagents (chitosan, buffers, cross-linkers)	800
		Bacterial culture media & diagnostic kits	600
		Fish procurement, feed & maintenance	600
Subtotal			3,200
2	Publication Charges	Open-access journal fees	800
3	Patent Filing	Preliminary filing and documentation	500
4	Operations & Miscellaneous	Lab disposables, PPE, unforeseen expenses	500
Total			5,000

6. References

Álvarez, C. A., Acosta, F., Montero, D., Guzmán, F., Torres, E., & Vega, B. (2014). Synthetic hepcidin from fish: uptake and protection against Vibrio anguillarum in sea bass (Dicentrarchus labrax). Fish & Shellfish Immunology, 45(2), 662–667.
Álvarez, C. A., et al. (2016). (Specific title not fully provided in the original synopsis. Likely a follow-up study on synthetic hepcidin variants).
Buschmann, A. H., Tomova, A., López, A., Maldonado, M. A., Henríquez, L. A., Ivanova, L., ... & Cabello, F. C. (2012). Salmon aquaculture and antimicrobial resistance in the marine environment. PLoS One, 7(8), e42724.
Cabello, F. C. (2006). Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment. Environmental Microbiology, 8(7), 1137–1144.
Cabello, F. C., Godfrey, H. P., Tomova, A., Ivanova, L., Dölz, H., Millanao, A., & Buschmann, A. H. (2013). Antimicrobial use in aquaculture re-examined: its relevance to antimicrobial resistance and to animal and human health. Environmental Microbiology, 15(7), 1917–1942.
Economou, V., & Gousia, P. (2015). Agriculture and food animals as a source of antimicrobial-resistant bacteria. Infection and Drug Resistance, 8, 49–61.
Goldman, M. J., Anderson, G. M., Stolzenberg, E. D., Kari, U. P., Zasloff, M., & Wilson, J. M. (1997). Human β-defensin-1 is a salt-sensitive antibiotic in lung that is inactivated in cystic fibrosis. Cell, 88(4), 553–560.
Hancock, R. E. W. (2001). Cationic peptides: effectors in innate immunity and novel antimicrobials. The Lancet Infectious Diseases, 1(3), 156–164.
Holmstrom, K., Gräslund, S., Wahlström, A., Poungshompoo, S., Bengtsson, B. E., & Kautsky, N. (2003). Antibiotic use in shrimp farming and implications for environmental impacts and human health. International Journal of Food Science & Technology, 38(3), 255–266.
Kerry, J., Hiney, M., Coyne, R., NicGabhainn, S., Gilroy, D., & Smith, P. (1995). Fish feed as a source of oxytetracycline-resistant bacteria in the sediments under fish farms. Aquaculture, 131(1-2), 101–113.
Kumar, P., Nagarajan, A., & Uchil, P. D. (2017). Analysis of cell viability by the MTT assay. Cold Spring Harbor Protocols, 2017(6), pdb-prot095505.
Rajanbabu, V., & Chen, J. Y. (2011). Applications of antimicrobial peptides from fish and perspectives for the future. Peptides, 32(2), 415–420.
Vlieghe, P., Lisowski, V., Martinez, J., & Khrestchatisky, M. (2010). Synthetic therapeutic peptides: science and market. Drug Discovery Today, 15(1-2), 40–56.

Funding

Funding

Title of the proposal: Evaluation of Antimicrobial Activity of Novel De Novo Designed Synthetic Peptides Against Fish Pathogens

Funding Progress

Nonprofit Recipient

Topics

DOI

Funding Progress

Nonprofit Recipient

Topics

DOI

Title of the proposal: Evaluation of Antimicrobial Activity of Novel De Novo Designed Synthetic Peptides Against Fish Pathogens

Funding Progress

Nonprofit Recipient

Topics

DOI