# Bafilomycin A1 is a promising therapeutic agent against T. spiralis infection by inhibiting the heme-transporting ATP6V0C/HRG-1 complex

## TL;DR

Bafilomycin A1 shows promise as a treatment for T. spiralis infections by blocking a key heme-transporting protein complex.

## Contribution

Identifies Bafilomycin A1 as a drug candidate targeting the Ts-HRG-1/Ts-ATP6V0C complex in T. spiralis.

## Key findings

- T. spiralis scavenges heme from host proteins using an aspartic protease.
- The Ts-HRG-1 and Ts-ATP6V0C proteins form a functional heme-transport complex.
- Bafilomycin A1 inhibits this complex, reducing heme uptake and larval burden in mice.

## Abstract

Trichinella spiralis (T. spiralis), a zoonotic nematode that causes severe myositis and systemic morbidity, sustains chronic muscle parasitism through evolutionary adaptations; however, this globally prevalent disease lacks targeted therapies to disrupt chronic infection. Although the heme transport protein HRG-1 has been characterized as an intervention target in free-living species (e.g., Caenorhabditis elegans) and hematophagous parasites (e.g., Haemonchus contortus), the molecular machinery governing heme acquisition in the nonhematophagous parasite T. spiralis remains uncharacterized, and no drugs targeting HRG-1 have been reported until now. Herein, we demonstrate that T. spiralis, a parasite that lacks the ability to synthesize heme autonomously, has evolved a sophisticated mechanism to scavenge and utilize heme from its host. By employing an aspartic protease to degrade host hemoglobin and myoglobin in the parasitic niche, T. spiralis is able to liberate heme for its own growth and survival. The structurally and functionally conserved Ts-HRG-1 protein plays a key role in transporting heme to the entire worm, particularly to functional organs, such as the cuticle and stichosome. More importantly, we discovered that the interaction between Ts-HRG-1 and Ts-ATP6V0C results in the formation of a functional complex that is essential for the parasite’s heme acquisition. The intervention effect achieved by Ts-ATP6V0C RNAi or inhibiting the activity of Ts-ATP6V0C with bafilomycin A1 (BafA1) was consistent with Ts-HRG-1 RNAi, resulting in impaired heme uptake, developmental arrest and a reduced larval burden in mouse hosts. These findings enhance our understanding of the parasite’s heme acquisition mechanism and identify the development of drugs that target proteins that interact with HRG-1 as a new direction in anthelminthic drug research.

Chronic Trichinella spiralis (T. spiralis) infections currently lack effective anthelmintic drugs, particularly for the persistent muscle-dwelling phase. Exploring the physiological activities of T. spiralis during muscle parasitism as a breakthrough for drug development, we discovered that the T. spiralis aspartic protease degrades myoglobin to release heme, just as it degrades hemoglobin. As an organism incapable of synthesizing heme de novo, protein molecules that regulate heme uptake are undoubtedly potential intervention targets. Based on previous studies, we functionally confirmed that structurally conserved HRG-1 is a key protein involved in heme uptake in T. spiralis. Although reducing HRG-1 expression via RNAi affects larval growth and development, notably, no drugs blocking HRG-1 have been developed to date. In this work, Ts-ATP6V0C was identified as an HRG-1-interacting protein through coimmunoprecipitation, and most importantly, the intervention effect achieved by pharmacological inhibition of Ts-ATP6V0c was identical to that of RNAi. These findings suggest that the development of inhibitors targeting HRG-1-interacting proteins represents a new therapeutic direction for T. spiralis infections and even helminth infections.