From Genetic Engineering to Global Immunization

Authors:
Enrique Chacon-Cruz, M.D., MSc
Felicitas Colombo, MPA

Dr. Mariagrazia Pizza is Professor of Microbiology and Co-Director of the Centre for Bacterial Resistance Biology (CBRB) at Imperial College London. A world-renowned expert in vaccine development, she played a key role in the creation of the first genetically detoxified pertussis vaccine and has since led numerous groundbreaking bacterial vaccine projects including the Meningococcal B (MenB) vaccine, based on a reverse vaccinology approach. In 2023, she was bestowed the IVI-SK Bioscience Park MahnHoon Award for her outstanding contributions to global vaccine development.

Born in Eboli, Italy, Prof. Pizza studied Chemistry and Pharmaceutical Sciences at the University of Naples Federico II. Her thesis focused on the structural analysis of opioid peptides using nuclear magnetic resonance. Motivated by a family member’s illness, she pursued further training in pharmaceutical design and molecular biology at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany.

In 1986, she joined a vaccine research center in Siena, where she contributed to the development of a novel pertussis vaccine based on a genetically detoxified pertussis toxin. This formulation proved to be both safer and more immunogenic than existing options, offering effective protection for infants. Building on this success and leveraging advancements in genome sequencing, she pioneered the use of reverse vaccinology to develop a vaccine against Neisseria meningitidis serogroup B (MenB).

Prof. Pizza’s work in reverse vaccinology led to the discovery of new bacterial antigens and the development of the first MenB vaccine, now licensed in over 50 countries and used in national immunization programs, including the UK, where it was introduced in 2015. The vaccine remains the only approved MenB vaccine for infants, demonstrating an efficacy rate of 71% to 95%.

Before joining Imperial College, Prof. Pizza served as Senior Scientific Director of Bacterial Vaccines at GSK and Head of Research at the GSK Vaccine Institute for Global Health (GVGH), where she led strategic initiatives in global vaccine innovation. Over her 30+ year career, she has collaborated with leading scientists worldwide and has been instrumental in characterizing the structural and immunological properties of several key vaccine antigens.

She is an elected member of EMBO (European Molecular Biology Organization), the European Academy of Microbiology, and the Academia Europaea. She is also a Fellow of the American Academy of Microbiology, Vice Chair of the Bacteriology Division of the International Union of Microbiological Societies (IUMS), and a member of the WHO Product Development for Vaccines Advisory Committee (PDVAC). She has received numerous international awards and honors in recognition of her scientific achievements.

With over 250 peer-reviewed publications and co-inventorship on more than 70 patents, Prof. Pizza is widely regarded as one of the world’s foremost scientists in the field of vaccine research and development.

Her current research focuses on Klebsiella pneumoniae, a multidrug-resistant Gram-negative bacterium recognized as a major global health threat. Her lab aims to identify novel virulence factors and antigens to better understand the mechanisms of Klebsiella pathogenesis and inform the design of future vaccine strategies.

Personal Journey

Prof. Mariagrazia Pizza was inspired to study pharmaceutical chemistry due to a long history of illness in her family. From a young age, she held onto the hope that one day, a medicine might exist that could miraculously make everything better.

“Now, with the age, I know that it was impossible to find something that can really transform everything. But at least you can try to do something that helps society. This was my dream,” she recalls.

After completing her university studies, Prof. Pizza became fascinated by the emerging field of genetic engineering, which was gaining momentum at the time. This led her to pursue further studies in genomics and genetics at the European Molecular Biology Laboratory (EMBL) in Heidelberg.

A few years later, back in Italy, she began her career in the private sector, working on vaccine development.

“I started working on pertussis and I’ve been lucky because that project has been really getting me in love with vaccines,” she says. 

Captivated by the impact and potential of her work, she never returned to academia full time. Instead, she has spent the past 30 years in Siena, leading and contributing to numerous vaccine research projects.

Pertussis vaccine milestones 

Prof. Pizza joined the pertussis vaccine project in the laboratory of Prof. Rino Rappuoli, where the team had successfully sequenced the operons containing the gene for pertussis toxin. Drawing on her background in genetic engineering, she led a project focused on creating a genetically detoxified version of pertussis toxin.

“The idea was that, since Pertussis toxin was inactivated by chemical detoxification as other vaccines like diphtheria and tetanus, we wanted to see whether we could make a better immunogen by changing only some of the amino acids important for the enzymatic activity,” she explains.

Since the 3D structure of pertussis toxin had not yet been resolved, long before technologies like AlphaFold, Prof. Pizza’s team relied on predictive modeling. They noted that pertussis toxin shares the same enzymatic mechanism as other well-known bacterial toxins, such as diphtheria, cholera, and Pseudomonas exotoxin. Despite targeting different host proteins, these toxins all exhibit ADP-ribosyltransferase activity, the ability to transfer an ADP-ribose group to a host protein.

“It’s an enzyme that allows the ADP ribose to be added to a target protein. So for example, the target protein of cholera and heat-labile toxin are obviously different. In fact, this difference explains why cholera or E.coli infection causes diarrhea,” she points out. 

Through site-directed mutagenesis, the team introduced various mutations into the catalytic domain of the toxin. Among these, they identified one mutant with two key amino acid changes that completely eliminated toxicity in vitro and in animal models while preserving strong immunogenicity.

“Based on this finding, we published the results in a high-impact journal and started, in the meantime, the development of the toxin that was manufactured at a larger scale,” Prof. Pizza says.

In clinical trials, the team tested two formulations: one with the genetically detoxified pertussis toxin alone, and another in combination with filamentous hemagglutinin (FHA) and pertactin (69K). Both formulations were evaluated in clinical trials, and the trivalent version was tested in efficacy trials in comparison with the trivalent formulation containing the chemically detoxified toxin and the whole-cell pertussis vaccines. 

“The real milestone has been to demonstrate that only by changing two amino acids without changing the overall structure of an antigen you can get high quality of antibodies. These antibodies recognized the native toxin [better] resulting in [superior] neutralization. Beautiful,” she smiles, humbly acknowledging what many consider a foundational moment in rational antigen design.

While genetically modified pertussis vaccines have since improved, Prof. Pizza points out that for years, whole-cell pertussis vaccines were perceived as overly reactogenic due to side effects. This led to a preference for acellular, protein-based vaccines. In her view, the problem was not toxicity itself but the inconsistency of strains and production processes used in early whole-cell vaccines.

“Now that manufacturing processes are more consistent, the reactogenicity we see is often linked to stronger immune activation, which is actually a good sign for vaccine efficacy,” she notes.

However, a significant concern remains: acellular pertussis vaccines do not prevent colonization. The bacteria continue to circulate, even among vaccinated individuals, which has become a major public health issue in recent years.

The challenge lies in inducing a Th17 response after just one dose. But if additional antigens are needed beyond those in the acellular formulation, a simple priming dose with whole cell vaccine might not be enough.This leads to a dilemma: combining different formulations for priming and boosting could improve efficacy, but the cost and complexity of manufacturing such a strategy would be significant.

“This is my only doubt. And this really needs to be tested. But it’s a very good idea,” she claims, adding that it’s very difficult to develop vaccines that use different formulations for prime and boost. “The production costs would be extremely high.”

Ultimately, the underlying mechanisms for inducing immunity that blocks colonization remain unclear. Some systemic vaccines, such as those against meningococcus (e.g., MenACWY), appear to reduce nasopharyngeal carriage, but it’s not fully understood how.

“In my view, it’s not just about conjugation. It’s more about how potent your antigen is in triggering a strong systemic response, strong enough that antibodies can transudate to the mucosa,” she shares.

Developing the Meningococcal B vaccine 

As is often the case in groundbreaking science, when Prof. Mariagrazia Pizza began working on the Meningococcal B (MenB) vaccine, she had no certainty about the project’s success. What the team did know, however, was that sequencing the bacterial genome had become possible. And that alone was a game changer.

“The idea was: if we have a genome, we have access to everything that a bacterium can express. We essentially have access to a catalogue of all the potential proteins this bacteria can express,” she recalls.

The challenges were immense. The Neisseria meningitidis genome contains around 2,000 genes, a massive dataset to analyze. Because a vaccine requires antigens that are accessible to the immune system, the team focused on identifying proteins that were likely surface-exposed. Through this genomic screening, they discovered 600 potential surface antigens.

“That was really shocking, as you can imagine. Because 600, you cannot just make your selection by looking at the computer,” she shares. “You really need to then express these proteins, to purify them, to immunize mice, and to see whether they induce a protective immune response.”

Another major hurdle was the genetic variability of N. meningitidis, particularly for MenB strains that differ widely between regions and countries. Ensuring broad, global protection required a new approach to epidemiological assessment. The team developed an entirely new assay, robust, standardized, and easy to implement across laboratories worldwide. The strength of this new epidemiology tool was unprecedented, as it provided access to the predicted coverage of this novel vaccine and became the foundation for the regulatory submissions. 

“This has been unique because it has made possible the introduction of this data into a regulatory files. This data has [supported] the registration of the vaccine in the different countries,” she notes.

The MenB vaccine, which also provides some cross-protection against the other meningococcal seroroups, was first licensed in Europe, followed by the United States. Since then, it has been approved in many other countries and incorporated into national immunization programs.

“For me it’s deeply emotional to see that this vaccine is now saving lives,” she proudly says. And even more meaningful as it offers some protection against gonorrhea, as many retrospective studies suggests.

Future of novel vaccine platforms

From mRNA and structural vaccinology to reverse vaccinology and genetically modified bacterial viruses, a growing array of innovative technologies is transforming vaccine development. While no single platform offers a universal solution, Prof. Pizza believes that the future lies in embracing a diverse set of tools, including AI, to drive vaccine innovation forward.

“We cannot say there will be one unique technology for all future vaccines,” she explains. “We need to have a combination: reverse vaccinology, structural vaccinology, adjuvants, glyconjuation, RNA, viral vectors,. We have to test all these platforms to understand which ones [lead] the way to find the ideal vaccines for the future.”

Prof. Pizza continues to explore how vaccines can serve as a key strategy in tackling the growing global crisis of antimicrobial resistance (AMR). As a Professor of Microbiology, she is also deeply committed to educating the next generation of scientists.

“I really believe there’s so much for young people to learn about vaccines,” she shares. “Especially now, when misinformation is such a big issue.”

She emphasizes the need for bright, ethical, and skilled individuals. People with “good minds, good hands, and good ideas” to carry the torch of vaccine development into the future.

“We often forget what diseases like diphtheria or polio even look like—because they’ve largely disappeared, thanks to vaccines,” she notes. “What I always tell my students, and I truly believe this, is: we are lucky, we don’t see these diseases anymore because, fortunately, everyone has been vaccinated. It is someting we should never forget”