The Wu Lab's research focuses on two scientific questions:
- To find and characterize HIV-1 broadly neutralizing antibodies (bnAbs) and antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC) antibody-dependent cellular phagocytosis (ADCP) function.
- To understand how these highly functional anti-viral antibodies are driven by the evolution of the HIV-1 envelope gene in infected host.
For question No. 1, we have devised a VSV-based probe for bnAb and ADCP-Ab isolation and a virus infected cell-based probe for ADCC-Ab isolation. In parallel the antibody repertoire sequencing is carried out to strengthen the analysis of these antibodies.
For question No. 2, we have been examining the envelope gene evolution in both HIV-1 infected humans and SHIV infected rhesus macaques. In the meantime, sera mapping (an analysis of the antibody target) is carried out to probe the envelope immunogenicity for bnAb, ADCC-Ab, and ADCP-Ab development. Our ultimate research goal is to understand the immunological processes of antiviral Ab maturation and production and the immunogenicity of the HIV-1 envelope glycoprotein to explore the concepts in vaccine development.
Our overall research interest is to elucidate the mechanisms by which the HIV-1 envelope glycoprotein (Env) elicits broadly neutralizing antibody (bnAb) responses in humans and rhesus macaques, with an ultimate goal to guide HIV-1 vaccine development.
1. Isolate and Characterize HIV-1 bnAbs
We have a NIH funded R01 to develop and apply HIV-1 Env probes by VSV-surface display to efficiently isolate bnAbs from a large number (n>50) of clade-B and non-B clade infected individuals. We have successfully applied the probe VSVAD17 to two clade B infected donor samples and isolated five unique bnAbs. The BCR repertoires from the two donors have identified two bnAb lineages, M4008_N1 and M1214_N1, that class-switched to both IgG and IgA. The bnAb M4008_N1 targets a novel glycan-independent epitope at gp120 V3, and the bnAb M1214_N1 targets another novel epitope with an elongated footprint extending from V2 to V5, named the V2V5 corridor. Overall, the VSVENV probe identified bnAb lineages with neutralizing IgG and IgA members targeting new sites of HIV-1 Env vulnerability. These results have been published in Jia et al, Cell Host & Microbe 2020, 27: 963-975.e5. Based on these results, we will couple the VSVENV-probed B cell sorting with donor BCR repertoire analyses to identify potential IgM, IgG, and IgA lineage members of bnAbs. We are developing a new project to investigate how IgA bnAbs differ from IgG in Fc-mediated functions and how IgA bnAbs differ from IgG bnAbs in a SHIV mucosal protection model.
2. Determine bnAb Precursors
To understand how bnAbs are developed, we face two fundamental immunological questions: 1) What are the naïve or founder B cells selected to generate HIV-1 bnAbs? 2) How do these selected founder B cells react with HIV-1 Env?
Funded by a NIH R01, we proposed to identify founder B cells by longitudinal analysis. For this study we have obtained longitudinal plasma and PBMC samples from SHIV-infected rhesus macaques and HIV-1 infected individuals. We have established the Illumina 2x300bp pair-end MiSeq sequencing platform to sequence longitudinally collected samples from time points prior to bnAb isolation. As we examine earlier samples, we expect to find less mutated antibody sequences and eventually the heavy and light chain progenitor sequences for expression and functional tests.
3. Determine How Neutralization Breadth is Developed
While only a fraction of infected individuals mount bnAb responses and such responses typically do not appear until 2-3 years after infection, almost all infected individuals develop nAbs against autologous viral strains during the first year of infection. Currently, we do not understand how the early narrow autologous nAbs develop into bnAbs in some individuals. We initially hypothesized two mechanisms: precise targeting and epitope shifting. The mechanism of “precise targeting” describes that bnAbs arise through founder B cells that precisely target a conserved neutralizing epitope. In this case, once the antibody obtains sufficient somatic hypermutation to neutralize autologous strains, it simultaneously acquires neutralization breadth against heterologous strains. The mechanism of “epitope shifting” describes that the founder B cells originally targeting suboptimal epitopes with narrow autologous neutralizing activity later shift to optimal epitopes (by additional somatic mutations) in response to autologous viral escape, thus acquiring neutralization breadth. Our longitudinal plasma analysis of SHIV-infected rhesus macaques and HIV-1-infected humans indicated that the autologous nAbs came up early at 3 – 13 months post-infection and the heterologous nAbs came up later at 10 – 36 months post-infection. The apparent lag between autologous and heterologous nAb development does not support the “precise targeting” mechanism. We are in the process of “longitudinal epitope analysis” to understand the mechanism of HIV-1 bnAb development.
4. Antiviral Neutralizing Antibodies to Emerging Infectious Diseases
We have expanded our research to isolate and characterize antiviral functional antibodies to Emerging Infectious Diseases such as Influenza (H7N9), Ebola, and Coronaviruses. Recently urged by the ongoing COVID-19 pandemic, we have taken an active role in our center-led responses to isolate neutralizing antibodies against SARS-CoV-2. We will apply our expertise and experience in antibody research to find a strategy to stay ahead of and better prepare for the next pandemic.
In summary, our research will fill in knowledge gaps in understanding the processes of effective B cell responses. It is our view that this knowledge is required to induce HIV-1 bnAbs through vaccination. Having access to precious samples from longitudinally followed SHIV-infected rhesus macaques and HIV-1 infected humans, we have the opportunity to address two critical steps during these processes: the initial activation of rare B cell precursors and the later antibody somatic hypermutation and affinity maturation. Results from these studies will lead towards our ultimate goal of developing an effective HIV-1 vaccine.