Protective immunity of Hantaan virus nucleocapsid and envelope protein studied using baculovirus-expressed proteins

Abstract

Recombinant Hantaan virus nucleocapsid protein (rNP) and recombinant envelope (rEnv) proteins were prepared using a baculovirus expression system to examine the role of Hantaan virus structural proteins in protective immunity. Passive transfer of spleen cells from mice immunized with rNP conferred partial protection or prolongation of time to death from fatal Hantaan virus infection in suckling mice which were challenged with Hantaan virus at 40 LD50 (survival rate: 43%) or 4 LD50 (survival rate: 43%). The T cell-enriched fraction protected one mouse from lethal infection but the B cell-enriched fraction had no such effect on fatal HTN infection. The protective effects of the antibody against HTN challenge were examined by passive immunization. The monoclonal antibody ECO 2 directed to NP also conferred partial survival and significant difference in time to death. Although rEnv antigen failed to induce neutralizing antibody, both immune spleen cells and immune serum to rEnv conferred partial protection upon suckling mice. These results indicate that both nucleocapsid and envelope proteins of Hantaan virus were responsible for induction of cell mediated protective immunity. Vero E 6 cells infected with Hantaan virus expressed envelope protein on the surface, as determined by flow cytometry. However, there was only negligible expression of nucleocapsid protein.

Hantavirus Infection in SCID Mice.

“…SCID mice died 32 to 34 days p.i., while newborn mice usually died within 3 weeks p.i. [25,26,28]. In addition, nervous symptoms such as paralysis and hyperreactivity which are characteristically observed in moribund newborn mice, was uncommon among SCID mice.…”

“…In the present study, we inoculated hantaviruses to severe combined immunodeficiency (SCID) mice and compared collected for virus isolation and their homogenate was inoculated into Vero E6 cell monolayer as previously described [28]. Various organs were also examined for existence of viral antigen by immunohistochemical procedures as previously described [9,11].…”

“…Cell transfer experiment: Whole spleen cells were prepared from untreated BALB/c mice (8-weeks old) according to the procedure described before [28]. Whole spleen cells (10 7 cells/mouse) were administered i.p.…”

Human pathogenic hantaviruses and prevention of infection

“…On the other hand infection experiments with suckling mice suggest that N protein-reactive antibodies may confer at least some protection and prolong survival. 37 The humoral immune response towards hantaviruses is longlasting. Several studies have shown that in HCPS-convalescent individuals neutralizing IgG antibodies persist at high levels for years.…”

A pseudotype vesicular stomatitis virus containing Hantaan virus envelope glycoproteins G1 and G2 as an alternative to hantavirus vaccine in mice

“…Although limited efficacy has been observed, attempts have been made to develop recombinant protein-based vaccines that reduce or eliminate biohazard risks during preparation as well as achieve higher efficacy. Immunizations with recombinant G1 and G2 proteins expressed by baculovirus and vaccinea virus induce very low or negligible amounts of neutralizing antibody [12][13][14]. Although the antibody titers are high, this low efficacy for inducing neutralizing antibody may be attributable to the incorrect conformation of the recombinant G1 and G2 compared to the native proteins.…”