Pandey Group

Supervisors: Dr Victoria Ozberk, Prof Michael Good and Dr Manisha Pandey

Molecular Immunology and Vaccinology (MIV)

Infectious diseases account for over 17 million deaths per year. Globally, as of August 2021, there have been over 205 million confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and over 5 million deaths.  SARS-CoV-2 is the causal agent of Coronavirus Disease 2019 (COVID-19).  A protein called the Spike (S) protein is attached to the viral surface. The interaction between the S protein and a receptor present on human lung cells (angiotensin converting enzyme 2 receptor; ACE2 receptor) initiates viral entry into human cells.  There are a total of 8 SARS-CoV-2 vaccines approved for full human use.  These vaccines have high efficacy rates against current SARS-CoV-2 strains; however, their efficacy may be compromised against mutant strains.

Another significant pathogen, Streptococcus pyogenes is a Gram-positive bacterium that causes multiple diseases. S. pyogenes primarily infects the upper respiratory tract (URT) and the skin. If left untreated, invasive (necrotising fasciitis and streptococcal toxic shock syndrome) and post streptococcal sequalae of diseases (rheumatic fever and rheumatic heart disease) can follow. S. pyogenes infections and their sequelae are responsible for more than 500,000 deaths each year. Despite the burden of disease, a vaccine is not yet available. Ideally, a vaccine against SARS-CoV-2 and S. pyogenes should be immunogenic and protective at the primary sites of infection and against all strains of the infectious agent.

Our laboratory focuses on two main elements of vaccine design and development. These include (i) peptide (immunostimulatory) antigens and (ii) vaccine delivery systems. We have identified highly efficacious peptide antigens for use in vaccines against S. pyogenes. These peptide antigens, conjugated to a carrier molecule such as diphtheria toxoid (DT) have been tested with various vaccine delivery/adjuvant systems such as Aluminium hydroxide for intramuscular delivery or liposomal platforms for mucosal delivery. Two vaccine combinations for S. pyogenes are now being prepared to enter a Phase I Clinical trial. In parallel, using murine models, immunological and molecular biology investigations will continue to unravel mechanism of vaccine mediated strain transcending immunity. Using our expertise in designing peptide vaccines, we are working towards the rapid development of a vaccine against SARS-CoV-2. We have identified peptide antigens from the receptor binding domain (RBD) of the Spike protein and demonstrated their potential as a vaccine candidate. We will now combine these peptide antigens with various vaccine delivery systems to develop a vaccine that is protective at the primary site of infection (URT) and against upcoming viral mutants of concern. Success with this project will lead to the development of vaccines which will have real world impact.

Techniques: ELISA, flow cytometry, SDS-PAGE, MCS-conjugation, in vitro neutralisation assay, cell culture, liposome formulation, in-vivo techniques such as vaccination and sample collection.

Supervisors: Dr Victoria Ozberk, Prof Michael Good and Dr Manisha Pandey

Bacteriology and Immunology

Seemingly mild streptococcal infections can rapidly escalate to serious invasive infections with a high mortality rate. The overall incidence for invasive Streptococcus pyogenes disease (ISD) was reported to vary between 2-4 per 100,000 people in developed countries, although in some developed countries, a marked rise in the incidence of ISD has been reported. In developing countries, very high rates are reported amongst the young and the elderly (up to 75 per 100,000) (Steer et al, 2012). In approximately 20% of cases, ISD is accompanied by a streptococcal toxic shock syndrome (STSS) with multi-organ failure and case fatality rates approaching 50% even in the best-equipped facilities. It can occur after any streptococcal infection but most commonly occurs after infections of the skin and is usually associated with necrotising fasciitis, myositis or deep bruising.

Streptococcal ‘superantigens’ (SAgs) are thought to play the key role in the pathogenesis of STSS (Proft and Fraser, 2016). However, we have recently demonstrated that the M protein also plays a critical role in the pathogenesis of STSS (M. Pandey et al, 2019).  We have developed a model for STSS using HLA-humanized mice and showed that these mice became gravely ill when infected with a SpeC+ (a streptococcal superantigen) positive S. pyogenes organism that caused STSS in human patients.

The project will utilise humanised mice to model STSS caused by SpeA+ organisms and will examine critical roles for both the M protein and SpeA in pathogenesis. It will further assess whether vaccination with our lead vaccine candidate (J8/p*17) can prevent disease and whether passive immunotherapy can rapidly ablate the mitogenic and inflammatory activity of SpeA+ S. pyogenes organisms, and clear infection. The project will further advance to test combination therapy utilising monoclonal antibody to J8/p*17 and antibiotics with a view to reduce repeated antibiotic administration and thus antibiotic resistance. Success with this project could quickly lead to novel therapies to treat STSS.

Techniques: Culturing of bacteria, mouse infection model, PCR, Enzyme Linked Immunosorbent Assays (ELISA), in-vitro cell culture assays, in-vivo techniques such as bacteria challenge, vaccination and sample collection.

Supervisors: Dr Manisha Pandey, Prof Michael Good

Bacteriology, Immunology and Vaccinology

Streptococcus pyogenes is a Gram-positive bacterial pathogen of humans. It causes a broad spectrum of diseases ranging from self-limiting throat and skin infections to life-threatening streptococcal toxic shock syndrome and rheumatic heart disease. Altogether, these infections result in over 500,000 deaths annually. Naturally acquired immunity to S. pyogenes takes several years to develop and its slow acquisition has been attributed specific virulence factors impeding innate immunity and significant antigenic diversity of the type-specific M protein, hindering acquired immunity. There are known to be in excess of 250 different M types and limited evidence suggest that M-type-specific immunity can protect in a type-specific manner. This also poses a significant hinderance to vaccine development, as an effective vaccine will need to protect against most, if not all, existing S. pyogenes serotypes. In addition, it is yet to be defined if a single vaccine will protect against both skin and mucosal infections which are the primary infection sites.

To understand protective immune mechanisms against S. pyogenes infection, this project will investigate immune responses following natural infection and/or vaccination in mice and humans. S. pyogenes can infect via skin or mucosa and it is not clear whether infection at one site would induce immunity to protect at another site. Therefore, understanding the mechanisms of cross-compartment immunity i.e. skin infection protecting against mucosal infection and vice-versa, is critical.

These investigations will tease apart the role of specific immune cell populations contributing towards protective immunity against multiple serotypes as well as at various infection sites. Deciphering immune mechanisms involved in site-specific and cross-compartment immunity will have significant implications for vaccine designs and vaccination strategies.Techniques: Culturing of bacteria, mouse infection models, PCR, Enzyme Linked Immunosorbent Assays (ELISA), in-vitro bacterial and cell culture assays, flow cytometry, in-vivo techniques such as bacteria challenge, vaccination and sample collection.

Supervisors: Dr Ailin Lepletier, Dr Manisha Pandey, Prof Michael Good

Immunology, Immunotherapy, Autoimmunity

Rheumatic heart disease (RHD) is an incurable chronic disease associated with an autoimmune mechanism unleashed by group A streptococcus (GAS) infection and not yet fully understood. Global burden of disease estimates performed in 2010 calculated the number of individuals living with RHD was at least 34.2 million, with 10.1 million disability-adjusted life years lost. Together with others, we have identified autoreactive T cells and antibodies sharing common epitopes with GAS strains that are known to irreversibly damage the heart in RHD. Though the protective mechanisms of immune suppressive CD4⁺T-lymphocytes, known as regulatory T cell (Treg) in the context of autoimmunity is well defined, a role for Treg in modulating autoreactive immune response in RHD has been largely overlooked.

We propose to provide a novel approach and pre-clinical evidence for the efficacy of Treg immunotherapy in controlling rheumatic heart disease (RHD) by enhancing the function of Treg. Towards this, we will conduct several studies to take the first deep dive into Treg contributions to RHD using a rat autoimmune valvulitis (RAV) model. We will further assess samples from patients with RHD to demonstrate proof of concept. It is essential to gain a clear understanding of Treg impact on autoimmunity associated with complicated GAS infections and developing a highly effective and specific therapy to RHD.

Techniques: Immune cell isolation, ex vivo expansion of Treg, cell-based in vitro assays, flow cytometry analysis, cytometric bead array (CBA), Enzyme Linked Immunosorbent Assays (ELISA), immunohistochemistry, multiplex immunofluorescence.

Supervisors: Prof Michael Good & Dr Manisha Pandey

Molecular Immunology and Vaccinology (MIV)

Streptococcus pyogenes infections and their sequelae are responsible for an estimated 18 million cases of serious disease with >700 million new primary cases and 500,000 deaths per year. S. pyogenes infection always commences at the skin or throat and infection at either site can lead to very high rates of serious streptococcal-associated pathology including rheumatic heart disease (RHD), glomerulonephritis and invasive GAS (iGAS) disease. Mortality rates from rheumatic heart disease alone exceed 350,000 per annum with Indigenous Australians reported to suffer the highest rates in the world. Also, in these communities, skin infection (pyoderma) is far more prevalent than pharyngeal disease (≥70% vs <5%) leading to the hypotheses that RHD can follow skin infection in these populations [5, 6] and that skin infections can lead to immunity in the URT.

Broad-spectrum immunity to S. pyogenes in humans takes years to develop and this is attributed to serotypic diversity of S. pyogenes strains (>250 emm-types). This has severely hindered vaccine development. We have designed a vaccine that is based on a peptide from the conserved region of the M protein. Following intramuscular immunisation this vaccine induces both skin/systemic and mucosal immunity and protects against a panel of streptococci of multiple serotypes. The vaccine does not induce mucosal IgA and we hypothesize that protection is induced by transudative IgG. The project will investigate mechanism of immunity of this vaccine and it’s ability to induce enduring memory responses at both the mucosal surface and in the skin.

Techniques: Culturing of bacteria, mouse infection models, PCR, Enzyme Linked Immunosorbent Assays (ELISA), in vitro bacterial and cell culture assays, flow cytometry.

Supervisors: Dr Simone Reynolds, Prof Michael Good & Dr Manisha Pandey

Molecular Immunology and Vaccinology (MIV)

Streptococcus pyogenes is responsible for infections such as pharyngitis, sepsis, necrotizing fasciitis and streptococcal toxic shock syndrome. Our lab has been developing a vaccine to combat this disease and are preparing to take the lead vaccine candidates into clinical trials. As part of the pre-clinical research we are interested in defining the global utility or coverage of our vaccine. A recent paper in Nature Genetics (Davies et al, 2019) utilised large-scale comparative genomics to determine the coverage and variation of Strep A antigens that could be potential vaccine candidates/targets. The technological platform described in this paper offers a method to assess the theoretical coverage of a vaccine candidate.

The lead vaccine candidates currently under investigation in our lab are comprised of two group A Streptococcus antigen, one derived from the M-protein and the other from the subtilisin-like protease SpyCEP. Using the information from the Nature Genetics paper as a guide, the project will assess the actual global coverage of a lead Strep A vaccine to determine its global utility. To assess the global coverage, the project will determine whether our vaccine recognizes all variants of SpyCEP and if anti-SpyCEP antibodies neutralize variants of SpyCEP (using an IL-8 protection assay) in bacteria isolates. The project will also determine the allelic variants of the conserved C3 epitope that is present in our lead vaccine candidates (J8/p*17). The efficacy of our vaccine against Strep A harbouring these allelic variants will also be assessed.

Techniques: Bacteria culturing, DNA extraction, PCR, Enzyme Linked Immunosorbent Assays (ELISA), basic Bioinformatics.