Research Projects

The emergence of fungal infections is a serious health concern in recent times and demands immediate attention. Fungal infections are often underestimated and attract less attention compared to bacterial or viral infections, despite their high mortality and morbidity.1 Cryptococcus neoformans is a pathogenic fungal microorganism and a frequent cause of cryptococcal meningitis in immunocompromised individuals. It mainly affects the immune system of hosts, is responsible for 180000 deaths every year.2 The prevalence of fungal diseases has significantly increased in the last decade. These are becoming more of a burden on the healthcare system due to the lack of potential treatment options. Moreover, the rise of antibiotic resistance in fungal pathogens is increasing at dangerous level, especially in C. neoformans, is very high. Therefore, in 2022, the World Health Organization (WHO) released the first-ever human fungal priority pathogens list (FPPL), causing severe risk of mortality or morbidity, in which C. neoformans was categorized under the critical priority group.3 The C. neoformans infections are a major health risk for those who are undergoing solid organ transplants, chemotherapy, and HIV/AIDS patients.4 It can also attack the lungs, skin, and other organs of the body, leading to serious problems. Polysaccharide capsule of C. neoformans is one of the major virulence factors and is unique among the pathogenic fungi.5 Capsule is composed mainly of two polysaccharide components: major (∼90%) glucuronoxylomannan (GXM) and a minor component (∼10%) glucuronoxylomannogalactan (GXMGal).6 Polysaccharide vaccine against C. neoformans is mainly focused on GXM to date, results showed that antibodies against GXM polysaccharide conjugates have been shown to be protective and non-protective in different studies.7,8 Moreover, antigenic heterogeneity across serotypes (A, D, C, D, and AD) of GXM complicates vaccine design. Although GXM gal is a minor portion of the capsule, GXMGal has more robust immunomodulatory effects on host cellular immunity.9 Hence, we thought to focus on GXMGal, which can be a strong candidate for the vaccine development against C. neoformans. For this purpose, we plan to obtain these cell surface carbohydrates of C. neoformans in pure and homogenous form through chemical synthesis. Then, conjugate these well-defined antigens with a carrier protein for further vaccine development against these infections. This strategy ensures batch-to-batch consistency, avoids pathogen culture, and allows precise immune targeting. Previato et al. proposed a latest structure after revisions of GXMGal as poly-α-(1→6)-D-galactan backbone having β-Xylp-(1→3)-α-Manp-(1→3)[β-Xylp-(1→2)-]-α-Manp-1→4)[β-GlcpA-1→3)]-β-Galp and β-D-galactofuranosyl residues (Figure 1A).11 Although GalXM is a minor component, it is known to induce a stronger immune response to activate dendritic cells, induce Th17 cytokine production, and provide protection against infection.12 Galactofuranose residue is a non-mammalian monosaccharide known to induce highly immunogenic responses; hence, we decided to study the highly abundant vicinally situated Galf units with galactan backbone with D-glucuronic acid branching, which is assumed to be the most immunomodulant glycan for immunological studies (Figure 1B). Recent studies show UDP-glucuronic acid transport is essential for the virulence of C. neoformans. Therefore, we design an oligosaccharide that contains both non-mammalian galactofuranose residue along with the acidic glucuronic acid as a side chain; hence, designed antigens 2 and 3, which are expected to give a better immune response (Figure 2). By integrating synthetic glycochemistry towards vaccine design, this project addresses a critical unmet need in global health. A successful semisynthetic glycoconjugate vaccine could significantly reduce the global burden of cryptococcal disease, especially among vulnerable populations.