Construction of a recombinant full-length membrane associated IgG library

High-throughput reformatting of phage-displayed antibody fragments to IgGs by one-step emulsion PCR

Single-chain variable fragment (scFv) is the most common format for phage display antibody library. The isolated scFvs need to be reformatted to full-length IgGs for further characterization. High throughput reformatting of scFv to IgG without disrupting VH-VL pairing is of great demanding for exhaustive screening of all antibodies in IgG format. Herein, we developed a strategy based on the overlap extension PCR in emulsion to reformat scFv to IgG while maintain the accuracy and complexity of variable region pairing. Using CD40 as an example target, we reformatted phage display derived CD40 binding scFv library to IgG mammalian display library and isolated high affinity CD40 binding IgGs. This robust and reliable antibody reformatting approach could be integrated into any phage display based antibody drug discovery.

Characterization of a monoclonal antibody that binds to both gp120 and gp41

Aim: AIDS has become a global pandemic. Characterization of broadly HIV-1-neutralizing antibodies (bnAbs) may facilitate the vaccine design. Methods & materials: Recombinant antibody library construction provides a resourceful way of monoclonal antibody screening and isolation against HIV-1. Results: In this study, we screened a novel human monoclonal antibody, named 2B8, which can bind both the gp120 and gp41 subunits of the HIV-1 envelope glycoprotein (Env). 2B8 did not bind to the CD4 binding site mutant, gp120 D368R, suggesting that the 2B8 epitope is conformational and overlaps the CD4 binding site on gp120. 2B8 neutralized 50% of the HIV-1 cell line-based pseudo virus isolates tested. Conclusion: The further study of its novel epitope may reveal the new mechanism of neutralization and assist the design of vaccine immunogens against HIV-1.

Establishment of a lethal aged mouse model of human respiratory syncytial virus infection

Human respiratory syncytial virus (HRSV) infection is a significant cause of morbidity and mortality, particularly among the children and the elderly. Despite extensive efforts, there is currently no formally approved vaccine and effective antiviral options against HRSV infection are limited. The development of vaccines and antiviral strategies for HRSV was partly hampered by the lack of an efficient lethal mouse model to evaluate the efficacy of the candidate vaccines or antivirals. In this study, we established a lethal HRSV mouse model by consecutively passaging a clinical HRSV isolate, GZ08-0. GZ08-18 was isolated from mouse bronchioalveolar lavage fluids at the 50^th passage of GZ08-0. Importantly, all GZ08-18-inoculated mice succumbed to the infection by day 7 post infection, whereas all GZ08-0-inoculated mice recovered from the infection. Subsequent investigations demonstrated that GZ08-18 replicated to a higher titer in mouse lungs, induced more prominent lung pathology, and resulted in higher expression levels of a number of key pro-inflammatory cytokines including IFN-γ, MIP-1α, and TNF-α in comparison to that of GZ08-0. The cyclophosphamide pretreatment rendered the mice more susceptible to a lethal outcome with less rounds of virus inoculation. Full genome sequencing revealed 17 mutations in GZ08-18, some of which might account for the dramatically increased pathogenicity over GZ08-0. In addition, by using ribavirin as a positive control, we demonstrated the potential application of this lethal mouse model as a tool in HRSV investigations. Overall, we have successfully established a practical lethal mouse model for HRSV with a mouse-adapted virus, which may facilitate future in vivo studies on the evaluation of candidate vaccines and drugs against HRSV.

Vaccine based on antibody-dependent cell-mediated cytotoxicity epitope on the H1N1 influenza virus increases mortality in vaccinated mice

Antibody-dependent cell-mediated cytotoxicity bridges humoral immunity and cellular immunity. Thus vaccine candidates which can elicit both broadly neutralizing antibodies and potent antibody-dependent cell-mediated cytotoxicity (ADCC) are recommended. Previously, a panel of functional epitopes that can elicit ADCC effects is isolated and characterized on the H1N1 Influenza Virus. Based on these identified epitopes, an epitope vaccine against H1N1 infection has been designed. The serum of vaccine immunized mice show potent ADCC activities in comparison with vector control group and HA ecto domain vaccinated group. However, the release of IL-6 and TNFα is higher in lung of epitope vaccine immunized mice. The viral load is also higher in epitope vaccine immunized mice. In addition, the epitope vaccine immunized mice showed lower survive rate than both empty vector immunized mice and HA ectodomain immunized mice. Passive transfer of serum from epitope vaccine immunized mice to healthy adult mice can decrease the survival rate of recipients after viral challenge. Our data suggested that ADCC epitope based vaccine has a mortality promoting effect rather than protective effect after H1N1 viral challenge. This result provides indications in future vaccine design with a consideration of balancing humoral immune response and cellular immune response.