Identifying correlates of protection
The need for vaccines against some of the world’s deadliest pathogens, including HIV, malaria, TB, and influenza, has never been greater. While measurement of antibody quantities provides a cursory impression of the overall magnitude of the antibody response, by themselves, this information provides little insight into the mechanism by which antibodies provide protection from infection, information that is likely critical for the development of an effective vaccine. Systems Serology was developed to overcome this limitation, allowing for the rapid definition of the functional and biophysical profiles of the antibody response, which is key to mechanistically understanding how antibodies provide protection following vaccination and identifying a correlate of protection.
Identifying correlates of protection following natural infection or vaccination
While over 100 vaccines against HIV have been tested in clinical trials over the last 30 years, only one vaccine has demonstrated any degree of efficacy—efficacy that could not be replicated in follow-up trials. However, while human trials have repeatedly failed to demonstrate protection, promising vaccine candidates that are protective in animal models have been developed. Understanding how these candidate vaccines are protective in animal models potentially provides a road map for the strategic development of a vaccine that is protective in humans. Focusing on one such vaccine candidate, Systems Serology was applied to identify the functional features of the vaccine-elicited antibody response that were tied to protection.
Systems Serology Application:
Protective Efficacy of a Global HIV-1 Mosaic Vaccine against Heterologous SHIV Challenges in Rhesus Monkeys
Of the antibody features and functions that were examined, several were linked with protection from infection, including antibody titer and neutralization activity. Beyond titer and neutralization, however, antibody-dependent cellular phagocytosis, that is, the ability of an antibody to drive internalization and degradation of antibody-coated targets by monocytes and macrophages, was also linked with protection. This finding suggests that antibody functions other than neutralization may be critical for driving protection. As only low levels of neutralizing antibodies were generated by the tested vaccine, the extra-neutralizing activity of antibodies may be necessary for vaccine-mediated protection, especially against difficult-to-neutralize viruses like HIV.
The results of the Systems Serology profiling of candidate HIV vaccines suggest that we may be overlooking the potential role of extra-neutralizing antibody functions in driving protection. The identification of the antibody functions—both neutralization as well as extra-neutralizing antibody functions—associated with protection from infection, will ultimately allow for the development and optimization of candidate vaccines that drive high levels of these specific functions, potentially increasing the efficacy of the vaccine. The Systems Serology platform offered by SeromYx can be used to identify antibody features and functions that are critical for vaccine-mediated protection, providing the information necessary to develop more effective vaccines.
Barouch DH, et al., Protective efficacy of adenovirus/protein vaccines against SIV challenges in rhesus monkeys. Science. 2015 Jul 17; 349(6245): 320–324.
Immune correlate–guided vaccine development
Vaccines are among the most cost-effective and efficacious public health interventions that prevent disease at a global level. While traditional vaccine design approaches, focused on weakening or inactivating the pathogen or designer antigens, have consistently failed to provide protection against some of the deadliest pathogens in both animal models and human vaccine studies, the concept of “rational vaccine design” has emerged. This concept hinges on the identification of the antibody functions that are associated with vaccine-induced immunity, which are then used to reverse engineer the immune response such that the targeted functions are elicited via vaccination. Two pieces of knowledge are critical to this vaccine design approach, termed immune correlate–guided vaccine design: the identification and validation of the immune correlates themselves and understanding how the immune response is altered by changes in the vaccine itself.
Rational vaccine design: Modifying antibody functionality with adjuvants
As vaccine design becomes more sophisticated, more attributes become available to tune the resulting immune response. Changes in the vaccination strategy and vaccine regimen, including changes to vaccine dose and timing, and the inclusion of specific adjuvants have all been shown to impact the subsequent immune response. Just as Systems Serology can be used to rapidly identify and validate the actual correlates of protection, Systems Serology can also be used to screen novel vaccine candidates to identify those with the target functional profile. Building on immune correlates identified across various candidate HIV vaccines, Systems Serology was used to characterize the functional activity of a panel of HIV vaccine candidates to determine which vaccine regimen best induced the target functional profile.
Systems Serology Application:
As part of this study, participants received one of eight different vaccine regimens that differed in the composition and dose of the vaccine boosts. While each of the regimens induced HIV-specific antibodies, the functional activity that was elicited was dramatically different across vaccine regimens. While some vaccine regimens induced low levels of antibody-dependent cellular phagocytosis (the target antibody function), other vaccine regimens induced high levels of antibody-dependent cellular phagocytosis. Intriguingly, the increased functional activity was not solely the result of increased antibody levels, suggesting that changes in vaccine regimen can not only impact antibody quantity but can also independently alter antibody quality.
Rational vaccine design: Modifying antibody functionality via changes in vaccine regimen
When evaluating new vaccines for clinical development, neutralization is often the experimental assay used to predict the potential efficacy of a vaccine candidate, regardless of whether neutralization is known to be the correlate of protection. However, the importance of extra-neutralizing antibody functions, such as antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and antibody-dependent complement deposition, in providing protection from infection following vaccination is becoming increasingly apparent. The Systems Serology suite of assays offered by SeromYx provides a platform in which numerous antibody functions can be rapidly evaluated, providing critical information for the selection of the optimal vaccine regimens that should move further into clinical development.
Francica JR, et al., Innate transcriptional effects by adjuvants on the magnitude, quality, and durability of HIV envelope responses in NHPs. Blood Adv. 2017 Nov 28; 1(25): 2329–2342.
Barouch DH, et al., Evaluation of a mosaic HIV 1 vaccine in a multicentre randomised double blind placebo controlled phase 1 2a clinical trial APPROACH and in rhesus monkeys. Lancet. 2018 Jul 21; 392(10143): 232–243.
Guiding monoclonal antibody selection and development
Just as the development and use of monoclonal antibodies has revolutionized treatment of cancer, monoclonal antibodies are increasingly recognized as potential therapeutics for the treatment of infectious disease. However, as with vaccines, the lack of detailed knowledge of the correlates of protection has hindered the development of effective monoclonal therapeutics for the treatment of infectious disease: of the almost 80 approved monoclonal antibody therapeutics, only 4 have been approved for infectious disease. Importantly, however, just as the correlates of protection identified using Systems Serology can be used to guide vaccine design, Systems Serology can be used to identify the mechanism of action of monoclonal therapeutics, which can then be used to develop more effective therapeutics.
Neutralization is neither necessary nor sufficient for protection
For many infectious disease targets, neutralization is often the primary means by which antibody candidates are selected for clinical development. However, as with the mounting importance of extra-neutralizing antibody functions in vaccine-mediated protection from infection, extra-neutralizing antibody functions are increasingly recognized as critical in monoclonal antibody–mediated protection from infection. In numerous studies with both individual antibodies and cocktails of antibodies, non-neutralizing antibodies have demonstrated protection in animal models of Ebola virus infection. Coupled with the observation that not all neutralizing antibodies are protective, this suggests that neutralization activity is neither necessary nor sufficient for protection in vivo. However, defining the functions of EBOV-specific monoclonal antibodies that are linked to protection had proven difficult. As part of the Viral Hemorrhagic Fever Immunotherapeutics Consortium, Systems Serology was used to profile almost 170 Ebola-specific monoclonal antibodies to define the antibody features and functions critical to protection.
Systems Serology Application:
Both neutralization and Fc-mediated functions are linked with protection
While neutralizing activity was clearly linked with protection, analysis of antibody effector functions suggested a role for additional Ab functions in protection. Critically, for monoclonal antibodies with limited neutralizing activity, increased extra-neutralizing antibody functions were associated with protection in vivo. In particular, the ability of antibodies to induce phagocytosis and activate NK cells were particularly important for protection by non-neutralizing antibodies. Furthermore, neutralizing antibodies that lacked the ability to induce phagocytosis were less protective in vivo, suggesting that neutralization may not be the critical functional activity underlying protection in vivo. Similar observations have been observed in HIV and influenza infection, further highlighting the importance of extra-neutralizing antibody functions in monoclonal antibody–mediated protection. Ultimately, the data generated from this study provides a critical framework to both define and exploit immune correlates of protection to rationally guide the development of effective therapeutics against Ebola virus and other human pathogens.
The comprehensive profiling of Ebola virus–specific monoclonal antibodies using Systems Serology ultimately identified functions key to protection. Critically, the identification of these functions provides the roadmap to increasing the efficacy of existing therapeutics through enhancement of functional activity. Furthermore, the incorporation of assays probing these functional correlates into the screening process used to downselect therapeutic candidates, could accelerate the development of rationally designed and functionally enhanced monoclonal antibody–based therapies. Given the important role monoclonal therapeutics will play in slowing emerging infectious epidemics, the Systems Serology suite of assays offered by SeromYx provides a platform in which antibody functionality can be broadly and rapidly determined, ultimately providing critical information for the selection of highly functional monoclonal antibodies that should move further into clinical development.
Bronwyn M. Gunn, et al., A Role for Fc Function in Therapeutic Monoclonal Antibody-Mediated Protection against Ebola Virus. Cell Host Microbe. 2018 Aug 8; 24(2): 221–233.e5.
Developing antibody based diagnostic tests
The biophysical features of antibodies are exquisitely sensitive to the environment of the body at the time of production, and changes in these features have been observed across health and disease, with dramatic changes noted with age, during pregnancy, across geographic areas, and with autoimmune disease, infection, and malignancy. Importantly, these changes in antibody features can be harnessed to develop antibody-based diagnostic tests that can be used to guide clinical care of patients. As such, Systems Serology can be used to identify the antibody features and functions that discriminate particular patient populations, which can then be used to develop more effective diagnostic tests.
Tuberculosis is the leading cause of infectious disease deaths worldwide. Complicating the effective treatment of tuberculosis patients is that an accurate and cost-effective diagnostic test is lacking. The currently used clinical tests largely rely on the use of nonspecific clinical symptoms, expensive microbial tests, and T cell–based tests that cannot discriminate between individuals with latent infection who are clinically well and the subset of individuals in this population who progress to active tuberculosis disease. As a simple point-of-care diagnostic with an enhanced ability to distinguish latent from active tuberculosis could dramatically limit the spread of this disease, Systems Serology was used to identify the antibody features and functions that could distinguish patients with active infection from those with latent infection.
Systems Serology Application:
Individuals with either latent or active tuberculosis generated antibody responses against the bacteria. However, these responses were functionally distinct, with latently infected individuals demonstrating increased antibody-dependent NK cell functions, whereas actively infected individuals demonstrated increased antibody-dependent phagocytic responses. In addition to these differences in functionality, significant differences in the biophysical features of the bacteria-specific bacteria were observed including increased binding to FCGR3 and unique antibody glycosylation patterns. Combined, these data suggest that individuals with active infection have an antibody profile that is functionally and biophysically distinct from individuals with latent infection.
Biomarkers are important for the diagnosis and management of disease, providing a means to predict development of and diagnose a disease, predict response to particular therapies, and monitor disease progression and treatment efficacy. Antibodies are increasingly being recognized as potential biomarkers, demonstrating diagnostic and prognostic potential across a range of diseases, including autoimmune disease, infection, malignancies, and Alzheimer’s disease. Beyond the mere presence of particular antibodies, changes in the functional or biophysical features of antibodies has the potential to more precisely distinguish patient groups or predict outcome, potentially allowing for more individualized care. The Systems Serology suite of assays offered by SeromYx provides an opportunity to identify potential biomarkers that can distinguish patient populations or predict disease progression, providing the information critical for the development of cost-effective, point-of-care diagnostic tests and personalized medicine.
Lu LL, et al., Functional Role for Antibodies in Tuberculosis. Cell. 2016 Oct 6; 167(2): 433–443.e14.
Application in immuno oncology
Context and Problem:
Monoclonal antibody–based treatments have revolutionized the treatment of a large number of cancers. For example, through the use of monoclonal therapeutics, the 5-year survival rate for patients with metastatic melanoma has increased significantly, from less than 5% with chemotherapy alone to 20% with ipilimumab (Yervoy) monotherapy to 52% for patients receiving the combination of nivolumab (Opdivo) and ipilimumab. While these dramatic results have provided hope to millions, these treatments are not universally effective. Some patients fail to respond, and there is currently no method to determine who would respond to a given treatment regimen. As being able to determine whether a given treatment regimen will be successful for patient before the treatment is given is critical, Systems Serology was used to determine if there were antibody features that could predict successful treatment with ipilimumab.
Systems Serology Application:
Pre-treatment features of tumor-specific antibodies can separate responders from non-responders
In a pilot proof-of-concept study, a small cohort of ipilimumab-treated melanoma patients, half of whom responded to ipilimumab, were retrospectively profiled using Systems Serology. To identify potential antibody features that could predict treatment success, serum samples collected prior to starting ipilimumab treatment were profiled against a panel of known melanoma tumor antigens or melanoma cell line isolates. Interestingly, prior to beginning ipilimumab treatment, the patients who responded to ipilimumab had a distinct antibody profile compared to the patients where ipilimumab failed to control tumor progression. While preliminary, these results suggest that it may be possible to predict if a treatment will be successful based on antibody profiles. Ongoing studies aim to validate this signature and determine if similar signatures exist across other tumor types and treatments.
Conclusions and future directions:
Long thought to be limited to the control of infections, the role of antibodies in the diagnosis, treatment, and control of cancer is increasingly being recognized. Tumor-infiltrating B cells have been shown to produce tumor-reactive antibodies, which are detectable in the blood of cancer patients. Importantly, these tumor-infiltrating B cells have been linked to favorable prognoses across a number of tumors, and antibodies from these cells can drive tumor regression. Likely critical to the activity of these naturally occurring or vaccine-induced antibodies are the myriad of Fc-mediated functions that antibodies can induce.
The Systems Serology suite of assays offered by SeromYx has broad potential applications in this space, from aiding in the development of novel cancer vaccines and therapeutics as well as guiding personalizing patient care with existing therapeutics. Systems Serology can also be used to identify the antibody features and functions that are associated with the clearance of virus-induced tumors, such as human papillomavirus–associated cervical carcinoma or Epstein-Barr virus–associated lymphoma, as well as evaluating the antibody response to neoantigen-based vaccines to identify antibody functions that may be associated with tumor remission. This information can then be used to guide the design of more effective vaccines and monoclonal therapeutics. Similarly, Systems Serology can be used to identify antibody features that can predict successful treatment or identify features linked to ongoing successful treatment. These antibody biomarkers could then be used to identify patients who would best respond to particular therapies or be used to easily monitor treatment progression. SeromYx is actively seeking collaborators to work with on pilot studies: please contact the CEO to discuss.