Monoclonal Antibodies

Example 3

Investigation of Virus Infectivity as a Factor that Determines Plaque Size.

With the revelation that plaque formation is strongly influenced by the immunogenicity of the virus, the possibility that infectivity of the virus could be another factor that determines plaque sizes was investigated. The uptake of viruses into cells in vitro was determined by measuring the amounts of specific viral RNA sequences through real-time PCR.

To measure total viral RNA, total cellular RNA was extracted using the RNEasy Mini kit (Qiagen), and complementary DNA synthesized using the iScript cDNA Synthesis kit (Bio-Rad). To measure total viral RNA, quantitative real-time PCR was done using a primer pair targeting a highly conserved region of the 3′ UTR common to all four serotypes of dengue; inter-sample normalization was done using GAPDH as a control. Primer sequences are listed in Table 5. Pronase (Roche) was used at a concentration of 1 mg/mL and incubated with infected cells for five minutes on ice, before washing with ice cold PBS. Total cellular RNA was then extracted from the cell pellets in the manner described above.

The proportion of infected cells was assessed by flow cytometry. Cells were fixed and permeabilised with 3% paraformaldehyde and 0.1% saponin, respectively. DENV envelope (E) protein was stained with mouse monoclonal 4G2 antibody (ATCC) and AlexaFluor488 anti-mouse secondary antibody. Flow cytometry analysis was done on a BD FACS Canto II (BD Bioscience).

Unexpectedly, despite DENV-2 PDK53 inducing stronger antiviral immune responses, it had higher rates of uptake by HuH-7 cells compared to DENV-2 16681 (FIG. 5). This difference continued to be observed when DENV-2 PDK53 inoculum was reduced 10-fold. In contrast, DENV-3 PGMK30 and its parental strain DENV-3 16562 displayed the same rate of viral uptake in host cells. Furthermore, DENV-2 PDK53 showed a higher viral replication rate compared to DENV-2 16681. This was determined by measuring the percentage of cells that harbored DENV E-protein, detected using flow cytometry. DENV-2 PDK53 showed a higher percentage of infected cells compared to DENV-2 16681 at the same amount of MOI from Day 1 to 3 (FIG. 6). In contrast, DENV-3 PGMK30 showed a reverse trend and displayed lower percentage of infected cells compared to DENV-3 16562. Results here show that successfully attenuated vaccines, as exemplified by DENV-2 PDK53, have greater uptake and replication rate.

Results above demonstrate that the DENV-2 PDK53 and DENV-3 PGMK30 are polarized in their properties that influence plaque morphologies. While both attenuated strains were selected for their formation of smaller plaques compared to their parental strains, the factors leading to this outcome are different between the two.

Accordingly, this study has demonstrated that successfully attenuated vaccines, as exemplified by DENV-2 PDK53 in this study, form smaller plaques due to induction of strong innate immune responses, which is triggered by fast viral uptake and spread of infection. In contrast, DENV-3 PGMK30 form smaller plaques due to its slower uptake and growth in host cells, which inadvertently causes lower up-regulation of the innate immune response.

Based on the results presented in the foregoing Examples, the present invention provides a new strategy to prepare a LAV, which expedites the production process and ensures the generation of effectively attenuated viruses fit for vaccine use.

Example 4

An overview of the immunization strategies for lectin-binding proteins, such as galectin-3, is shown in Table 18.

BALB/c mice were immunized with 2 mg/kg mRNA, complexed with LNPs, or 20 μg recombinant protein as indicated in Table 18. Plasma anti-galectin-3 IgG titers were assayed 7 days after the final boost, which was delivered at day 55.

FIG. 3 shows that the use of galectin-3 mRNA as a final boosting agent resulted in a significantly higher target-specific IgG titer than when purified recombinant protein (a traditional immunogen) was used. This effect was observed regardless of whether the antigens were delivered subcutaneously or intravenously.

Hybridomas producing galectin-3-specific antibodies were generated, and high affinity monoclonal anti-galectin-3 antibodies were obtained from further screens.

Table 19 provides a target protein-specific summary of the total number of hybridoma wells (generally about one third (⅓) of these wells contain hybridomas) screened and the number of confirmed target-specific antibodies obtained from those hybridomas wells following the use of lipid-encapsulated mRNA as an immunogen.

Table 20 provides a comparison of mRNA-LNP immunization methods with other conventional methods of immunization by number of hybridomas producing target-specific antibodies. In general, these data suggest that mRNA-LNP immunization is an effective method for inducing an immune response to a target protein antigen and for obtaining a higher number/rate of target protein-specific antibodies. In particular, these results confirm that mRNA-LNP immunization is surprisingly more effective than conventional immunization methods for obtaining antibodies specific for transmembrane proteins, e.g., multi-pass transmembrane proteins, such as GPCRs, which are difficult to raise antibodies against, and for poorly immunogenic proteins (e.g., proteins which produce low or no detectable target-specific IgGs in plasma of animals immunized with traditional antigen).

In general, successful generation of hybridomas producing antigen-specific antibodies have been achieved for at least 15 different targets utilizing mRNA-LNP immunization methods as exemplified herein. These results show that the mRNA immunization methods described herein are capable of eliciting an immune response against a wide range of antigens (e.g., transmembrane proteins, for example multi-pass transmembrane proteins, such as GPCRs) in host animals, and are effective methods for producing high affinity monoclonal antibodies, which can serve as parentals for generation of chimeric variants, humanized variants, and affinity matured variants.