Fig 3. Induction of neutralizing antibodies against NiV.
(A) Experimental design and schedule of inoculations with LC16m8 and the recombinant LC16m8s. Seventeen hamsters were intramuscularly inoculated with 1×106 PFU of the LC16m8. At 4 weeks, three groups of animals consisting of 4–7 hamsters each were inoculated with 5×106 PFU of the LC16m8-G, 2.5×106 PFU each of LC16m8-G and LC16m8-F, or the growth medium (negative control) as a prime immunization. Half of each group (2–4 hamsters) were further inoculated with the same recombinant viruses as a boost immunization. Two weeks after the final dose of the recombinant LC16m8, all hamsters were euthanized, which was followed by serum collection. Neutralizing titers were analyzed using live NiV (B) or pseudo-typed VSV expressing secreted alkaline phosphatase (SEAP) bearing NiV G and F proteins (VSV-NiV-SEAP) (C). (D) Experimental design and schedule of inoculations with the recombinant LC16m8s. Single recombinant virus (LC16m8-G or LC16m8-F, 5×106 PFU/hamster) or a mixture of the viruses (2.5×105 PFU each) was intramuscularly administered to hamsters once or twice at a 2-week interval without pre-immunization of LC16m8. Two weeks after the last inoculation with the recombinant virus, sera were collected from all hamsters. Neutralization titers were determined based on the assay using live NiV (E) or the VSV-NiV-SEAP (F). Bars show the mean values.