# Loss of NcBPK1 impairs bradyzoite differentiation and enhances virulence in Neospora caninum

## TL;DR

Deleting a gene called NcBPK1 in a cattle parasite makes it more dangerous, causing worse disease outcomes in mice.

## Contribution

This study reveals that NcBPK1 regulates parasite life cycle stages and virulence in Neospora caninum.

## Key findings

- NcBPK1 deletion increases parasite virulence and reduces neonatal survival in a mouse model.
- The mutant strain shows higher replication in macrophages and reduced bradyzoite gene expression.
- Loss of NcBPK1 disrupts the balance between acute infection and chronic persistence.

## Abstract

Neospora caninum is an apicomplexan parasite responsible for bovine neosporosis, a disease that leads to substantial economic losses in cattle due to abortion and reduced productivity. The pathogenesis of N. caninum is shaped by complex host–parasite interactions, and virulence is known to vary between strains. BPK1 (Bradyzoite pseudokinase 1), a pseudokinase previously identified as a potential virulence factor in Toxoplasma gondii, has not yet been functionally characterized in N. caninum.

To investigate the role of NcBPK1 in parasite virulence, a knockout strain (NcΔBPK1) was generated using CRISPR/Cas9 genome editing. The virulence of the mutant was evaluated in a pregnant mouse model by assessing neonatal survival and parasite burden in dam tissues. In vitro assays were conducted to examine parasite replication in bovine macrophages and to analyze the expression of stage-specific genes.

Deletion of NcBpk1 resulted in enhanced parasite virulence in vivo, as shown by a decrease in neonatal survival and higher parasite loads in maternal brain tissue. The NcΔBPK1 mutant also displayed enhanced replication in bovine macrophages and reduced expression of bradyzoite-specific genes, suggesting a defect in stage conversion.

These findings indicate that NcBPK1 is crucial for regulating the balance between acute replication and chronic persistence. Its absence promotes rapid tachyzoite proliferation and worsens disease outcomes. This study sheds light on the molecular mechanisms underlying N. caninum virulence. Further research is needed to elucidate the signaling pathways and protein interactions involving NcBPK1.

The online version contains supplementary material available at 10.1186/s13071-025-07076-4.