Ackerman/Alter: Leveraging Antibody Effector Function
Neutralizing antibodies are the holy grail of HIV vaccine development but attempts to elicit them with vaccines have yielded little in the way of success. The field is gradually opening up to a broader view, with more attention paid to antibodies that protect by mechanisms other than neutralization. The successes of the RV144 trial and non-human primate (NHP) studies of passively transferred antibodies have provided new enthusiasm for the extra-neutralizing antiviral properties of antibodies.
Two obstacles are encountered in attempting to monitor and improve upon these non-traditional effector functions of antibodies elicited by new vaccine regimens. First, the methods currently used to determine the innate immune-recruiting properties of antibodies are not compatible with the scale and standardization of analysis necessary to properly evaluate the potential role of this mechanism of protection in pre-clinical and clinical vaccine trials. Second, the signals responsible for driving B cells to produce potent innate immune-recruiting antibodies are not known. New technologies coupled to a better understanding of underlying signals that induce these types of immune responses are critically needed to improve upon the current vaccine approaches.
The consortia led by Drs. Margaret Ackerman of Thayer School of Engineering at Dartmouth and Galit Alter of Massachusetts General Hospital seeks to define, induce, and evaluate protection afforded by potent innate immune-recruiting antibodies. These are antibodies that form a bridge between the adaptive and innate immune systems. This may be particularly important in the case of HIV, where a narrow window of time soon after the virus enters the body may represent the best opportunity to prevent infection. Innate effector mechanisms are designed in part to contain pathogens until the adaptive immune system can respond, and this proposal will attempt harness the capacity of antibodies to recruit innate immunity in the crucial early days following HIV transmission.
These studies will develop enabling technology for monitoring of Ab effector functions, as well as define the signals required to induce such protective Abs in vivo, providing new approaches aimed at harnessing the antiviral activity of the Ab-Fc domain to provide sterilizing protection from HIV infection.
1. To develop a high-throughput proteomic-based microarray approach to quantify the spectrum of innate immune-recruiting antibody effector functions.
2. To develop a high-throughput in vitro system to define the innate immune inflammatory signals required for the induction of innate immune-recruiting antibody effector functions.
3. To develop a robust computational prediction model and scoring system to apply to microarray output.
4. To apply the proteomic microarray and in vitro screening system to define the top innate immune signals that result in the induction of the most potent innate immune-recruiting antibody functions.
5. To define whether in vitro innate immune signals coupled to gp140 clade C trimers induce innate immune-recruiting antibodies in vivo, and to define their protective efficacy in a SHIV challenge model.
6. To determine if specific stimulatory signals can durably programmed antibody glycosylation and if antibody glycosylation can be recalled following subsequent antigenic exposure.
The goal of the Ackerman/Alter CAVD is to
define, induce, and evaluate protection afforded by potent innate immune-recruiting antibodies through the development of (a) robust, high-throughput array technology to predict Fc-effector function and (b) an in vitro–screening approach to define the signals in B cells that result in the targeted production of innate immune–recruiting antibodies.
Objectives 1 and 3 have generated a remarkable platform to define the spectrum of biophysical antibody features that reliably predict specific effector functions. This platform has obviated the need to run complex, cell-based assays and has provided unprecedented resolution and insights into the humoral immune response. During Year 2, the platform has been adapted for use for study of rhesus Ab samples, a number of non-classical FcRs have been explored, and stool and nasal samples have been investigated. Additionally, we have applied the array, cell-based functional assays, and high-throughput glycan analysis to samples acquired from other disease cohorts, exposing dramatic, disease-specific profiles, including unique IgG glycoprofiles in subjects that resolve HCV infection during acute infection compared with subjects that progress to chronic disease and unique Ab functional profiles in elderly subjects infected with flu.
In parallel, in
Objective 2, we developed a robust in vitro B cell-screening approach to specifically define the signals that modulate innate immune–recruiting antibody responses that links glycosyltransferase transcriptional changes to changes in the biophysical and functional properties interrogated in
Objective 1/3. Both innate and adaptive stimuli profoundly modulate glycosyltransferase expression and drive antibody functionality towards specific effector profiles. Most interestingly, while TLR7/8/9 signals drive the generation of highly inflammatory antibodies able to recruit complement, only BCR triggering is able to unlock the glycoform modifications associated with the potent ADCC modifications used in the monoclonal therapeutics field on drugs such as rituximab. Surprisingly, TLR5 stimulation drives glycan modifications strongly associated with the recruitment of antibody-dependent cellular phagocytosis (ADCP) and ADCC that have been associated with enhanced antibody functionality in some patient cohorts and in some vaccine trials. Most interestingly, these glycosyltransferase changes are mediated in two distinct manners with distinct time scales, suggesting diverging mechanisms underlying the regulation of antibody glycosylation and that antibody functionality may be tunable and locked into memory. Linked to in vivo mouse vaccine studies, these studies provide the first proof-of-concept that vaccines may program long-lived innate immune–recruiting antibody activity.