The therapeutic logic of the study rests on the biology of bone morphogenetic proteins, or BMPs, which belong to the transforming growth factor beta superfamily. Although their name reflects their original discovery as inducers of bone and cartilage formation, BMPs are far more versatile than that label suggests. In the developing and mature central nervous system, they act as morphogens and survival factors, shaping neural fate decisions, guiding differentiation, and maintaining the functional integrity of neuronal circuits. The BMP2/6-SMAD1 signaling axis, in particular, has been shown to play a pivotal role in the development and functional maturation of nigrostriatal dopaminergic circuits, the very circuitry that degenerates in Parkinson’s disease. Because SMAD1 is the canonical intracellular mediator downstream of BMP receptors, activation of this pathway in dopaminergic neurons can trigger transcriptional programs that support cell survival, resilience against stress, and proper neuronal differentiation.

Translating that developmental biology into a therapy for an adult neurodegenerative disease, however, requires solving two problems at once. First, the protein must reach the target cells inside the brain. Second, it must do so in a way that is compatible with repeated, long-term administration in patients. Recombinant proteins are large, hydrophilic molecules that do not cross the blood-brain barrier in meaningful quantities, and invasive delivery into the brain parenchyma is impractical for a chronic disease. The research team addressed this by choosing the intranasal route, in which proteins administered into the nasal cavity can reach the central nervous system along olfactory and trigeminal nerve-associated pathways, bypassing the blood-brain barrier entirely. Intranasal delivery is non-invasive, can be self-administered, and has emerged in recent years as a practical gateway for biologics that would otherwise be excluded from the brain.

On the laboratory side, the investigators began with a cellular model designed to reproduce a key molecular insult of Parkinson’s disease. Neural stem cells were transduced with a lentiviral vector carrying A53T-mutant alpha-synuclein, a form of the protein linked to familial Parkinson’s disease and notorious for its propensity to misfold and aggregate. Overexpression of A53T alpha-synuclein in these cells creates a toxic intracellular environment that compromises viability, proliferation, and the capacity of the cells to differentiate along neuronal lineages. When the researchers treated these stressed neural stem cells with recombinant BMP2 and BMP6, they observed a clear rescue: the treated cells showed improved viability, better proliferation, and restored differentiation capacity. This set of results suggested that BMP2/6 signaling can counteract some of the damage inflicted by alpha-synuclein pathology and may exert protective effects on the survival and differentiation of dopaminergic neurons themselves.

Encouraged by the in vitro findings, the team moved into animal models that are standard for preclinical Parkinson’s research. They used two complementary lesion paradigms in mice. The first relied on 6-hydroxydopamine, a catecholaminergic neurotoxin that is taken up selectively by dopaminergic neurons and destroys them through oxidative stress, producing a rapid and reproducible loss of nigrostriatal neurons. The second used alpha-synuclein preformed fibrils, synthetic seeds of misfolded alpha-synuclein that, when introduced into the brain, recruit endogenous alpha-synuclein into pathological aggregates and trigger a slower, more disease-like progressive neurodegeneration accompanied by phosphorylated alpha-synuclein inclusions. Using both models matters because they probe different aspects of the disease: one tests whether neurons can be protected from acute chemical insult, while the other tests whether the treatment can interfere with the protein aggregation cascade that defines Parkinson’s pathology in patients.

In both lesioned mouse groups, the treatment consisted of mouse BMP2/6 recombinant proteins delivered intranasally. The results were consistent across the paradigms. Intranasal BMP2/6 significantly delayed the degeneration of dopaminergic neurons compared with control animals that received the same lesions without the protein therapy. Histological assessment of the substantia nigra and striatum showed that more dopaminergic neurons survived in the treated animals, and the preservation of neurons translated into functional benefit. On the rotarod test, a standard measure of motor coordination and balance in which mice must remain on a rotating rod for as long as possible, the BMP2/6-treated mice performed better than their untreated counterparts. The apomorphine-induced rotation test, which measures asymmetric turning behavior caused by dopamine imbalance between the two sides of the brain after apomorphine administration, likewise showed improvement in treated animals. Together, these behavioral assays demonstrated that the neuronal protection achieved at the cellular level was sufficient to preserve motor function, the clinical dimension that matters most to patients.

The mechanistic thread running through the study is the reactivation of SMAD1 signaling in a context where it has been weakened or overwhelmed by pathological stress. During normal development, BMP2 and BMP6 help dopaminergic neurons acquire their mature identity and maintain their circuitry, and the authors argue that this same pathway can be recruited therapeutically in the adult brain. By supplying recombinant ligands through the nose, the treatment effectively amplifies an endogenous survival signal at a time when alpha-synuclein toxicity, oxidative damage, and inflammatory stress are pushing neurons toward degeneration. The improved survival and differentiation of A53T alpha-synuclein-overexpressing neural stem cells in vitro further hints that BMP2/6 may support not only the survival of existing neurons but also the health of the neural stem cell compartment, a possibility with implications for endogenous repair mechanisms.

Several features of this work make it noteworthy in the crowded field of Parkinson’s neuroprotection. Most candidate neuroprotective agents tested in animal models have failed to translate into humans, often because of delivery problems, dosing limitations, or the fact that interventions began too late in the disease process. The intranasal approach sidesteps the blood-brain barrier without requiring surgery or implanted devices, and protein-based therapy avoids some of the off-target concerns associated with small molecules. Moreover, because BMP2/6 acts on a pathway intrinsic to dopaminergic neuron maintenance rather than on a single pathological species such as aggregated alpha-synuclein, it could in principle complement therapies aimed at aggregation, inflammation, or other disease mechanisms. The authors frame their findings as evidence for a potential role in early neuroprotection, which aligns with the growing consensus that disease-modifying treatment in Parkinson’s must begin before extensive neuronal loss has occurred.

Important caveats remain before this approach can be considered for clinical development. The study was conducted in mice, and rodent models of Parkinson’s disease, while informative, do not fully capture the complexity of the human illness, which involves multiple brain regions, non-motor symptoms, and decades of progression. The dose, frequency, and duration of intranasal protein delivery that would be required in humans are unknown, and the long-term safety of repeatedly activating BMP signaling in the adult brain will need careful evaluation, since BMP pathways participate in diverse processes beyond neuronal survival. It is also not yet established how much of the intranasally delivered protein reaches the human substantia nigra, a deep midbrain structure, although the olfactory route has been shown to deliver biologics to the central nervous system in other contexts. The published version of the study is open access and carries the DOI 10.1186/s12916-026-05269-x, allowing the scientific community to examine the full data, including the supplementary figures and original western blot images that the authors have made available.

Even with those caveats, the study adds a compelling entry to the short list of strategies aimed at protecting rather than replacing dopaminergic neurons. It demonstrates that a signaling axis borrowed from neural development can be harnessed in the adult brain through a practical, non-invasive delivery route, and that the resulting protection is measurable both in surviving neurons and in the motor behavior of living animals. If follow-up studies in larger animals confirm the effect and establish a safe dosing profile, intranasal BMP2/6 could eventually join the growing toolkit of biologics delivered nose-to-brain, shifting the therapeutic goal in Parkinson’s disease from managing symptoms to preserving the neurons that produce dopamine in the first place. For a disease in which every preserved neuron counts, that shift would represent a meaningful step forward.

Subject of Research: Intranasal BMP2/6 recombinant protein therapy for neuroprotection of dopaminergic neurons in Parkinson's disease models

Article Title: Intranasal delivery of BMP2/6 recombinant proteins attenuating Parkinsonian pathology-induced neuronal degeneration

Article References: Liu, S., Deng, Y., Si, W., & Wang, Z. (2026). Intranasal delivery of BMP2/6 recombinant proteins attenuating Parkinsonian pathology-induced neuronal degeneration. BMC Medicine. https://doi.org/10.1186/s12916-026-05269-x

Image Credits: AI Generated

DOI: 10.1186/s12916-026-05269-x

Keywords: Parkinson's disease, dopaminergic neurons, BMP2/6, intranasal delivery, neuroprotection, SMAD1 signaling, alpha-synuclein, neural stem cells, 6-hydroxydopamine, preformed fibrils, substantia nigra, recombinant protein therapy

The urgency of the problem is underscored by events beyond the farm gate. In 2015, an outbreak in Kazakhstan’s Betpak-Dala region killed nearly 200,000 Saiga antelopes within weeks, wiping out more than sixty percent of the regional population and pushing the species closer to extinction. The review notes that haemorrhagic septicemia, with its peracute course and capacity to trigger mass mortality events, bears an epidemiological resemblance to historical scourges such as plague and pneumococcal disease. Because the disease can kill susceptible animals within 24 to 72 hours, therapeutic intervention is rarely feasible, making vaccination the only realistic preventive strategy. The pathogen is also a central player in the bovine respiratory disease complex, the leading cause of morbidity and mortality in feedlot and dairy cattle, which further complicates disease management in production systems.

Conventional vaccines remain the backbone of control programs in endemic countries, and the review evaluates them in meticulous technical detail. Plain bacterins, the earliest whole-cell preparations, offered protection lasting only around six weeks and carried a risk of endotoxin-associated shock, and have now been largely abandoned. Alum-precipitated vaccines, produced by formalin inactivation followed by precipitation with potash alum, remain the most widely used formulations in Asia and Africa because of their simplicity and low cost; the electrostatic binding of antigens to alum promotes uptake by antigen-presenting cells and drives a strong Th2-polarized antibody response, but protective immunity typically lasts only four to six months and post-vaccination shock occurs in some animals. Aluminium hydroxide gel vaccines, which bind antigen ionically to the adjuvant, extend immunity to roughly six months, although one study found protection did not persist beyond 90 days even with immunomodulators such as levamisole and vitamin E.

Oil-adjuvanted vaccines emerge as the benchmark among conventional platforms. Formalin-inactivated organisms emulsified with mineral oil and lanolin induce higher and more sustained antibody titers than alum-based formulations, with field and experimental studies reporting protection lasting eight to twelve months and, in some cases, up to eighteen to twenty-six months. Their thermal stability is a major practical advantage in tropical settings, where cold-chain capacity is limited. Modern commercial adjuvants such as Montanide ISA-50, ISA-70 and ISA-206 reduce reactogenicity while preserving immunogenicity, and comparative field work has shown that formulation choice matters even within this class, with different emulsions performing better in calves than in adult animals. Yet even the best oil-adjuvanted products suffer from injection-site swelling, high viscosity, occasional shock reactions and a continuing dependence on booster doses. Multiple emulsion vaccines, created by re-emulsifying oil-adjuvanted preparations with Tween 80, were developed to ease these drawbacks and have protected buffalo calves for up to nine months and cross-bred calves for up to a year, but they have achieved limited commercial uptake and lack robust head-to-head field comparisons.

The review then turns to modified whole-cell approaches. Digested bacterial lysates, including potassium thiocyanate extracts and bacteriophage-lysed preparations of P. multocida B:2 grown under iron-limited conditions, broaden antigenic exposure and have elicited cross-protective responses in chickens, turkeys, mice and rabbits, with calves showing elevated antibody titers peaking at 90 days, but manufacturing heterogeneity has prevented standardization. Autogenous vaccines, formulated from isolates taken directly from infected herds, offer strain-specific outbreak control but only against homologous serovars and with a delayed onset of immunity. Live attenuated vaccines, which mimic natural infection, have been revitalized by molecular genetics: disruption of the aroA gene, which cripples aromatic amino acid biosynthesis, and of gdhA, which impairs glutamate dehydrogenase activity, produces strains that are attenuated yet immunogenic and protective in calves. Complementary defined mutants targeting lipopolysaccharide biosynthesis genes such as waaQ, capsule genes such as cexA and bcbH, and fimbrial genes including pfhaB1, pfhaB2 and pfhaC have all shown protective potential in experimental models. A recent finding by the lead author adds a novel target: field isolates of P. multocida produce hyaluronidase and can utilize host hyaluronic acid as a nutrient, implicating this metabolic pathway in virulence and opening a new avenue for rational attenuation. Chemically altered live vaccines, such as streptomycin-dependent mutants, have shown variable results across serotypes, underscoring the unpredictability of the approach.

Immunostimulatory and adjuvant-based strategies occupy a middle ground between whole-cell and defined-antigen vaccines. Bacterial DNA enriched with immunostimulatory CpG motifs, when used as an adjuvant for iron-inactivated P. multocida preparations, protected chickens against lethal challenge and raised antibody levels in mice above those achieved with conventional alum-adjuvanted vaccines. Dietary supplementation offers a surprising complementary lever: mice fed arginine-enriched diets alongside a formalin-inactivated vaccine achieved complete protection against challenge, while L-proline and L-glutamine similarly fortified vaccine-induced immunity. The authors stress that such nutritional immunomodulators should be viewed as adjuncts rather than substitutes for antigen-specific vaccination, and that their mechanisms and field efficacy in livestock remain uncharacterized.

Acellular and subunit vaccines represent the shift toward precision design. Candidates focus on the capsule, fimbriae, lipopolysaccharides and outer membrane proteins, whose surface-exposed loops drive antigenic diversity yet also carry conserved epitopes. Immunization with outer membrane proteins, particularly from bacteria cultured under iron-restricted conditions, has elicited cross-protective antibodies across serotypes, and buffalo calves vaccinated intramuscularly with B:2 outer membrane proteins reached peak ELISA antibody titers 21 days after vaccination. Recombinant subunit candidates under investigation include the type 4 fimbrial protein PtfA, the porin OmpH, outer membrane protein OMP87, the lipoprotein PlpE, which induced 80 to 100 percent protection in mice, and iron-regulated heme-binding proteins such as HasR, HemR and HgbA. Synthetic peptides derived from OmpH loop structures have also protected against homologous challenge. Bacterial ghosts, empty envelopes generated through controlled expression of the PhiX174 lysis gene E that preserve native surface architecture without cytoplasmic content, achieved complete protection in laboratory models, while anti-idiotype vaccines mimicking lipopolysaccharide or outer membrane protein epitopes have produced strong protective responses in mice and rabbits. None of these platforms has yet reached commercial application, however, because no universally cross-protective antigen has been identified and most efficacy data come from laboratory animals rather than cattle and buffalo.

Delivery technology emerges as a decisive frontier. Because P. multocida enters through the respiratory tract, intranasal vaccination targeting nasopharyngeal and bronchus-associated lymphoid tissue can stimulate mucosal IgA alongside systemic IgG, placing immunity at the site of pathogen entry. Evidence is compelling: intranasal potassium thiocyanate extract outperformed intramuscular administration, and intranasal delivery of a live attenuated B:2 derivative in buffalo raised antibody levels even in non-vaccinated in-contact animals through secondary transmission, suggesting herd-level protection. A live intranasal aerosol vaccine based on P. multocida B:3,4 was deployed at scale in Myanmar between 1992 and 1995, reaching nearly one million cattle and buffalo. Intradermal vaccination, exploiting the dense antigen-presenting cell network of the skin, offers dose-sparing potential demonstrated for influenza, rabies, poliovirus, yellow fever and hepatitis A vaccines, though some adjuvants provoke unacceptable local reactogenicity by this route. Formulation matters too: particulate carriers and mucosal adjuvants such as MF59, chitosan, Toll-like receptor agonists and mutant enterotoxins can amplify nasal responses, but toxin-based adjuvants have been linked to Bell’s palsy in human intranasal use, demanding caution.

The review’s final assessment is that the deepest unresolved gap is immunological: no validated correlate of protection exists for haemorrhagic septicemia in cattle or buffalo. Serum IgG titers are widely used as surrogate markers, yet no protective threshold has ever been established, and the roles of mucosal IgA, T cells, memory B cells and innate activation remain unmapped in target species. The authors call for standardized endpoints, including serum bactericidal and opsonophagocytic killing assays and IFN-γ ELISpot, harmonized challenge protocols and longitudinal field validation. They further argue that wildlife must enter the equation: no current vaccine has been evaluated in wild ruminants, and the remoteness of outbreak sites, cold-chain limits and the impossibility of repeated handling demand thermostable, oral-bait or aerosol formulations for free-ranging populations. Bridging these translational gaps, the authors conclude, will require coordinated work among immunologists, molecular biologists, veterinarians, wildlife specialists and regulators to convert a century and a half of vaccine innovation into durable, broad-spectrum and economically sustainable control of one of livestock’s most devastating diseases.

Subject of Research: Vaccine development against haemorrhagic septicemia caused by Pasteurella multocida in livestock and wildlife

Article Title: Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia

Article References: Raj, R., & Sharma, A. K. (2026). Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia. Discover Animals, 3(1), Article 86. https://doi.org/10.1007/s44338-026-00244-5

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00244-5

Keywords: haemorrhagic septicemia, Pasteurella multocida, vaccine development, livestock, mucosal vaccination, outer membrane proteins, oil-adjuvanted vaccines, recombinant subunit vaccines, intranasal delivery, wildlife, correlates of protection, cattle and buffalo