Development of horse neutralizing immunoglobulin and immunoglobulin fragments against Junín virus

Argentine haemorrhagic fever (AHF) is a rodent-borne disease with a lethality as high as ~30%, which is caused by the New World arenavirus, Junín virus (JUNV). It was once a major epidemic in South America and puts millions of people in Argentina at risk. Here, we aimed to develop horse antibodies or antibody fragments against JUNV. Before preparing the horse antibodies, a strategy to efficiently generate horse antisera was established based on comparisons among immunogens and immunization methods in both mice and horses. Antisera against JUNV were finally obtained by vaccinating horses with vesicular stomatitis virus pseudotypes bearing JUNV GP. The horse antibodies IgG and F(ab')₂ were subsequently demonstrated to effectively neutralize vesicular stomatitis virus pseudotypes bearing JUNV GP and to show some cross-neutralization against pathogenic New World arenaviruses. Further research revealed that Asp123 on GP1 is an important site for the binding of antibodies targeting mainly JUNV GP1 for neutralization. Collectively, this study presents an efficient strategy to develop horse antisera against JUNV and provides GP1-specific horse antibodies as potential therapeutics for AHF.