Fig. 5: Neutralizing antibody responses elicited by LASV GP VLP immunization. | npj Vaccines

Fig. 5: Neutralizing antibody responses elicited by LASV GP VLP immunization.

From: Adjuvant formulated virus-like particles expressing native-like forms of the Lassa virus envelope surface glycoprotein are immunogenic and induce antibodies with broadly neutralizing activity

Fig. 5

a Serial dilutions of day 77 sera from VLP-immunized rabbits were incubated with either LASV lineage II (LASV/NGA/2018/IRR/015) or LASV lineage IV (Josiah), and Vero 76 cells were infected with the serum–virus mixture. An unrelated rabbit- or human-derived serum served as negative control, while monoclonal antibody 37.7H served as positive control. Infected cells were stained with a specific LASV NP antibody and an HRP-labeled secondary antibody. Mean values of neutralization titer [IC50 values] are plotted with error bars indicating standard deviations. b Breadth of neutralization against five lineages of LASV. Pseudoviruses generated with clones derived from five LASV lineages and VSV G were assessed for their neutralization sensitivity (50% neutralization titer [ID50]) to twofold serial dilutions of day 77 sera from Rb#347 and Rb#350, and 37.7H antibody as positive control. Mean values are plotted with error bars indicating standard deviations. c Serial dilutions of day 77 sera from immunized rabbits, and 37.7H control antibody were incubated with VSVΔG/LASVGP. Virus neutralization titers were calculated as geometric mean titers (GMT) of the reciprocal value of the last serum dilution at which inhibition of the cytopathic effect on infected Vero E6 cells was detectable. Pre-immune sera (D0 samples) from corresponding rabbits were used as controls. The initial dilution was 1:16 and was therefore denoted as a titer of eight for GMT calculation. Graphs represent the means from three independent experiments. Error bars indicate standard deviations. d Infectivity of wild-type VSV was determined in the presence of D77 serum samples. Polyclonal neutralizing antibodies against VSV were used as a positive control. e LASV GP IgG ELISA. A total of 37 human serum samples collected in an LASV-endemic area of Guinea were analyzed at 1:200 dilution for the detection of IgG antibodies against LASV GP. The mean of OD 450 nm values (duplicate measurement) are shown. The dashed line depicts the cut-off for a positive antibody response, calculated as the mean of human negative sera + twofold SD. A standard curve was prepared using the human monoclonal antibody 37.7H. Graphs represent the means from four independent experiments. Error bars indicate standard deviations. f Human sera were tested for neutralizing antibodies against LASV GP using VSVΔG/LASVGP. VSV expressing wild-type glycoprotein G was used as a control. Virus neutralization titers were calculated as GMT and the mean value of all measurements is shown.

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