Evaluation of Histone Demethylase Inhibitor ML324 and Acyclovir against Cyprinid herpesvirus 3 Infection

by Selleckchem | Nov 16 2023

Cyprinid herpesvirus 3 (CyHV-3) can cause severe disease in koi and common carp (Cyprinus carpio). Currently, no effective treatment is available against CyHV-3 infection in koi. Both LSD1 and JMJD2 are histone demethylases (HD) and are critical for immediate-early (IE) gene activation essential for lytic herpesvirus replication. OG-L002 and ML324 are newly discovered specific inhibitors of LSD1 and JMJD2, respectively. Here, HD inhibitors were compared with acyclovir (ACV) against CyHV-3 infection in vitro and in vivo. ML324, at 20-50 µM, can completely block ~1 × 103 PFU CyHV-3 replication in vitro, while OG-L002 at 20 µM and 50 µM can produce 96% and 98% inhibition, respectively. Only about 94% inhibition of ~1 × 103 PFU CyHV-3 replication was observed in cells treated with ACV at 50 µM. As expected, CyHV-3 IE gene transcription of ORF139 and ORF155 was blocked within 72 h post-infection (hpi) in the presence of 20 µM ML324. No detectable cytotoxicity was observed in KF-1 or CCB cells treated for 24 h with 1 to 50 µM ML324. A significant reduction of CyHV-3 replication was observed in ~6-month-old infected koi treated with 20 µM ML324 in an immersion bath for 3-4 h at 1-, 3-, and 5-days post-infection compared to the control and ACV treatments. Under heat stress, 50-70% of 3-4-month-old koi survived CyHV-3 infection when they were treated daily with 20 µM ML324 in an immersion bath for 3-4 h within the first 5 d post-infection (dpi), compared to 11-19% and 22-27% of koi in the control and ACV treatments, respectively. Our study demonstrates that ML324 has the potential to be used against CyHV-3 infection in koi.

Comments:

The passage you provided describes a study that investigated the effectiveness of two histone demethylase (HD) inhibitors, ML324 and OG-L002, against Cyprinid herpesvirus 3 (CyHV-3) infection in koi fish (Cyprinus carpio). Here's a breakdown of the key findings and implications of the study:

1. **CyHV-3 Infection in Koi and Common Carp**: Cyprinid herpesvirus 3 (CyHV-3) can cause severe disease in koi and common carp. It's a significant concern in the aquaculture industry, and there are currently no effective treatments available for this viral infection.

2. **Histone Demethylases (HD) as Targets**: The study focused on two histone demethylases, LSD1 and JMJD2, which are involved in immediate-early (IE) gene activation essential for lytic herpesvirus replication. These demethylases play a role in the regulation of viral gene expression.

3. **Inhibitors Tested**: The researchers tested two specific inhibitors of histone demethylases: ML324, which targets JMJD2, and OG-L002, which targets LSD1. These inhibitors are newly discovered and were evaluated for their potential to inhibit CyHV-3 replication.

4. **In Vitro Results**:
   - ML324 at concentrations between 20-50 µM completely blocked CyHV-3 replication in vitro.
   - OG-L002, at 20 µM and 50 µM, showed 96% and 98% inhibition of CyHV-3 replication, respectively.
   - Acyclovir (ACV), a commonly used antiviral drug, achieved only about 94% inhibition at 50 µM.

5. **Gene Transcription Inhibition**: ML324 at 20 µM effectively blocked CyHV-3 immediate-early gene transcription within 72 hours post-infection (hpi), which is crucial for viral replication.

6. **Cytotoxicity**: The study found no detectable cytotoxicity in KF-1 or CCB cells treated with 1 to 50 µM ML324 for 24 hours. This suggests that the inhibitor is relatively safe for the tested cells.

7. **In Vivo Results**:
- In ~6-month-old infected koi, treatment with 20 µM ML324 in an immersion bath at 1-, 3-, and 5-days post-infection significantly reduced CyHV-3 replication compared to control and ACV treatments.
- Under heat stress conditions, daily treatment with 20 µM ML324 in an immersion bath within the first 5 days post-infection improved survival rates in 3-4-month-old koi compared to control and ACV treatments.

8. **Implications**: The study suggests that ML324 has the potential to be used as a treatment against CyHV-3 infection in koi. It appears to be effective in both in vitro and in vivo settings, and it shows promise in improving survival rates under stressful conditions. This research may lead to the development of a novel treatment strategy for CyHV-3 in koi and common carp, addressing a significant issue in aquaculture.

It's important to note that further research and clinical trials would be needed to confirm the safety and effectiveness of ML324 in a broader range of conditions and in different fish populations before it could be used as a standard treatment.