Recombinant Production and Functional Characterization of Andes Virus Gn and Gc in Pichia pastoris: A Path Towards Subunit Vaccine Development

Hantavirus Pulmonary Syndrome (HPS), caused by the Andes virus (ANDV), is a significant public health concern in South America, with no available vaccines or specific treatments. Neutralizing antibodies targeting ANDV glycoproteins Gn and Gc have shown protective effects in animal models, making them promising vaccine candidates. This study reports the recombinant expression, purification, and immunogenicity evaluation of sGn and sGc glycoproteins produced in the methylotrophic yeast Pichia pastoris. Initially, sGn was expressed as a secretable protein, but it formed aggregates once accumulated in the culture medium. To address this, the same strain was transformed with a vector expressing Gc, based on the hypothesis that Gn folding depends on Gc presence. However, co-expression of Gn and Gc in Pichia resulted in both proteins becoming trapped as insoluble aggregates inside the yeast, resembling inclusion bodies seen in E. coli. The recombinant proteins were solubilized and purified using metal ion affinity chromatography, followed by a refolding step before being used for immunization. The purified sGn and sGc antigens, formulated with aluminum hydroxide (AlOH), were tested in Syrian hamsters. The immunization results showed that the sGn-sGc formulation induced a strong Th1-biased immune response, characterized by high levels of IFN-γ, IL-12, and IL-6 cytokines, along with a specific antibody response against both Gn and Gc, with titers exceeding 1:10,000. These findings suggest the potential of these antigens as promising candidates for a subunit vaccine against HPS.