Anti-HIV-1 Activity of Crocodylus mindorensis Philippine Crocodile Serum in Cell-free and Cell-associated Virus Interactions to Human Peripheral Blood Mononuclear Cells

Abstract

Highly-Active Antiretroviral Therapy (HAART) is the recommended treatment and management strategy for HIV infection. Although the existing antiretroviral drugs are indispensably significant in improving the quality and extending the lives of HIV/ AIDS individuals, the drugs still have many limitations including development of resistance, production of toxicity, and their limited availability. These limitations continue to open new opportunities in the use of ethno-medicine for the management of HIV/AIDS. With this, few researchers have made effort to test the inhibitory activity of crocodile serum as it has a unique and diverse molecular activity in preventing HIV-1 replication. In this study, a cell culture-based assay was utilized using peripheral blood mononuclear cells coupled with colorimetric enzyme immunoassay to determine the HIV-1 reverse transcriptase activity of the treated cell-culture system. One HIV-1 seropositive serum was processed for Peripheral Blood Mononuclear Cells (PBMC) co-culture from which HIV-1 isolates were obtained. The HIV-1 reverse transcriptase activity after 21 days was 0.5928 pg/well. Moreover, a baseline Philippine crocodile serum concentration of 0.5% vol/vol was used based on the previous study conducted by Hinay and Sarol in 2018, and the cell viability results showed no cell reduction of mononuclear cells after 72 hours incubation. The inhibitory activity of the Philippine crocodile serum at 0.5% and 0.25% vol/vol concentrations inhibited 65.68 ± 2.93% and 69.92 ± 0.45% respectively in post-infection interactions. In addition, the Philippine crocodile serum in pre-infection interaction at 0.5% and 0.25% vol/vol concentrations inhibited 68.61 ± 1.67% and 69.95 ± 2.24% respectively. As has been noted, the inhibitory actions of the Philippine crocodile serum effectively regulate the HIV-1 replication in both pre-and post-infection interactions. With this, the Philippine crocodile serum could be a novel source of HIV-1 replication inhibitors.