Inactivated Wild-Type Heartland Virus (MO4)

Severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), and Guertu virus (GTV) all belong to the severe fever with thrombocytopenia syndrome/Heartland group of genus Bandavirus in the family Phenuiviridae of order Bunyavirales. Here, five neutralizing monoclonal antibodies against GTV and HRTV were obtained by hybridoma screening technology, four of which showed cross-reactivity and neutralization against the three viruses, and one monoclonal antibody (10D6) derived from HRTV specifically neutralized HRTV. The possible mechanism of cross-neutralization of monoclonal antibodies was explored by analyzing the glycoprotein (GP) sequence and structure of the three viruses. Despite the differences in activity against the three viruses, the preparation of these neutralizing monoclonal antibodies provides important antiviral candidates against GTV, HRTV, and SFTSV, and their protective effects in virus-infected mice need to be further evaluated.

IFA test results showed that serum samples from three mice (mouse 1, mouse 2, and mouse 3) inoculated with inactivated GTV all produced antibody responses to GTV-infected cells, while only two of the three mice inoculated with inactivated HRTV (mouse 1 and mouse 2) produced antibody responses to HRTV-infected cells (Figure 1A). After the third inoculation, mouse spleen cells were collected for the preparation of hybridoma cells. After four rounds of screening, neutralizing antibodies with different efficiencies were identified from 16 GTV-derived hybridoma cell clones and 21 HRTV-derived hybridoma cell clones that were able to neutralize the corresponding viruses. Among these cell clones, the researchers selected three cell clones containing GTV-derived mAbs (14B4, 14D8, and 20D4) and two cell clones containing HRTV-derived mAbs (10D6 and 27C8) for further testing. GTV-derived mAbs and HRTV-derived mAbs showed effective responses to GTV- and HRTV-infected cells, respectively (Figure 1B). However, no bands were detected when infected cells or purified viruses were used as antigens in Western blotting experiments, suggesting that these mAbs recognize the spatial structure of viral proteins rather than linear epitopes of viral proteins.

Figure 1. Screening of monoclonal antibodies against Guertu virus (GTV) and Heartland virus (HRTV). (Fu L, et al., 2023)