<italic>Momordica charantia</italic> phytoconstituents can inhibit human T-lymphotropic virus type-1 (HTLV-1) infectivity in vitro and in vivo.

There is an urgent need to find an effective therapy for life-threatening HTLV-1-associated diseases. Bitter melon (<italic>Momordica charantia</italic>) is considered a traditional herb with antiviral and anticancer properties and was tested in this study on HTLV-1 infectivity. GC–MS analyzed the alcoholic extract. In vitro assay was carried out using transfection of HUVEC cells by HTLV-1-MT2 cell line. The cells were exposed to alcoholic and aqueous extracts at 5,10, and 20 µg/mL concentrations. In vivo, mice were divided into four groups. Three groups were treated with HTLV-1-MT-2 cells as test groups and positive control, and PBS as the negative control group in the presence and absence of <italic>M. charantia</italic> extracts. Peripheral blood mononuclear cells (PBMCs), mesenteric lymph nodes (MLNs), and splenocytes were collected for HTLV-1-proviral load (PVL) assessment, TaqMan-qPCR. The GC–MS analysis revealed 36 components in <italic>M. charantia</italic>. The studies showed significant reductions in HTLV-1-PVL in the presence of extract in the HUVEC-treated groups (<italic>P</italic> = 0.001). Furthermore, the inhibitory effects of extracts on HTLV-1 infected mice showed significant differences in HTLV-1-PVL among <italic>M. charantia</italic> treated groups with untreated (<italic>P</italic> = 0.001). The T-cells in MLNs were significantly more susceptible to HTLV-1 than others (<italic>P</italic> = 0.001). There were significant differences among HTLV-1-infected cells in MLNs and splenocytes (<italic>P</italic> = 0.001 and 0.046, respectively). Also, aqueous and alcoholic extract-treated groups significantly affected HTLV-1-infected PBMCs (<italic>P</italic> = 0.002 and 0.009, respectively). <italic>M</italic>. <italic>charantia</italic> may have effective antiviral properties. The substantial compound of <italic>M. charantia</italic> could have inhibitory effects on the proliferation and transmission of HTLV-1 oncovirus. [ABSTRACT FROM AUTHOR]