Several highly pathogenic mammarenaviruses cause severe hemorrhagic and neurologic disease in humans for which
vaccines and
antivirals are limited or unavailable. New World (NW) mammarenavirus Machupo virus (MACV)
infection causes
Bolivian hemorrhagic fever in humans. We previously reported that the disruption of specific N-linked
glycan sites on the
glycoprotein (GPC) partially attenuates MACV in an
interferon alpha/beta and gamma (IFN-α/β and -γ) receptor knockout (R-/-) mouse model. However, some capability to induce neurological pathology still remained. The highly pathogenic Junin virus (JUNV) is another NW arenavirus closely related to MACV. An F427I substitution in the GPC transmembrane domain (TMD) rendered JUNV attenuated in a lethal mouse model after intracranial inoculation. In this study, we rationally designed and rescued a MACV containing mutations at two glycosylation sites and the corresponding F438I substitution in the GPC TMD. The MACV mutant is fully attenuated in IFN-α/β and -γ R-/- mice and outbred guinea pigs. Furthermore, inoculation with this mutant MACV completely protected guinea pigs from wild-type MACV lethal challenge. Last, we found the GPC TMD F438I substitution greatly impaired MACV growth in neuronal cell lines of mouse and human origins. Our results highlight the critical roles of the
glycans and the TMD on the GPC in arenavirus virulence, which provide insight into the rational design of potential
vaccine candidates for highly pathogenic arenaviruses. IMPORTANCE For arenaviruses, the only
vaccine available is the live attenuated Candid#1
vaccine, a JUNV
vaccine approved in Argentina. We and others have found that the
glycans on GPC and the F427 residue in the GPC TMD are important for virulence of JUNV. Nevertheless, mutating either of them is not sufficient for full and stable attenuation of JUNV. Using reverse genetics, we disrupted specific glycosylation sites on MACV GPC and also introduced the corresponding F438I substitution in the GPC TMD. This MACV mutant is fully attenuated in two animal models and protects animals from lethal
infection. Thus, our studies highlight the feasibility of rational attenuation of highly pathogenic arenaviruses for
vaccine development. Another important finding from this study is that the F438I substitution in GPC TMD could substantially affect MACV replication in neurons. Future studies are warranted to elucidate the underlying mechanism and the implication of this mutation in arenavirus neural tropism.