Biology subjects

Oliveira, L. V. N.

Publications and source records attributed to Oliveira, L. V. N..

3 recordsLinked to original sources

bioRxiv2024

Immunological correlates of protection mediated by a whole organism Cryptococcus neoformans vaccine deficient in chitosan

The global burden of infections due to the pathogenic fungus Cryptococcus is substantial in persons with low CD4+ T cell counts. Previously, we deleted three chitin deacetylase genes from C. neoformans to create a chitosan-deficient, avirulent strain, designated cda1{Delta}2{Delta}3{Delta} which, when used as a vaccine, protected mice from challenge with virulent C. neoformans strain KN99. Here, we explored the immunological basis for protection. Vaccine-mediated protection was maintained in mice lacking B cells or CD8+ T cells. In contrast, protection was lost in mice lacking /{beta} T cells or CD4+ T cells. Moreover, CD4+ T cells from vaccinated mice conferred protection upon adoptive transfer to naive mice. Importantly, while monoclonal antibody-mediated depletion of CD4+ T cells just prior to vaccination resulted in complete loss of protection, significant protection was retained in mice depleted of CD4+ T cells after vaccination, but prior to challenge. Vaccine-mediated protection was lost in mice genetically deficient in IFN{gamma}, TNF, or IL-23p19. A robust influx of leukocytes and IFN{gamma}- and TNF-expressing CD4+ T cells was seen in the lungs of vaccinated and challenged mice. Finally, a higher level of IFN{gamma} production by lung cells stimulated ex vivo correlated with lower fungal burden in the lungs. Thus, while B cells and CD8+ T cells are dispensable, IFN{gamma} and CD4+ T cells have overlapping roles in generating protective immunity prior to cda1{Delta}2{Delta}3{Delta} vaccination. However, once vaccinated, protection becomes less dependent on CD4+ T cells, suggesting a strategy for vaccinating HIV+ persons prior to loss of CD4+ T cells. ImportanceThe fungus Cryptococcus neoformans is responsible for >100,000 deaths annually, mostly in persons with impaired CD4+ T cell function such as AIDS. There are no approved human vaccines. We previously created a genetically engineered avirulent strain of C. neoformans, designated cda1{Delta}2{Delta}3{Delta}. When used as a vaccine, cda1{Delta}2{Delta}3{Delta} protects mice against a subsequent challenge with a virulent C. neoformans strain. Here, we defined components of the immune system responsible for vaccine-mediated protection. We found that while B cells and CD8+ T cells were dispensible, protection was lost in mice genetically deficient in CD4+ T cells, and the cytokines IFN{gamma}, TNF, or IL-23. A robust influx of cytokine-producing CD4+ T cells was seen in the lungs of vaccinated mice following infection. Importantly, protection was retained in mice depleted of CD4+ T cells following vaccination, suggesting a strategy to protect persons who are at risk for future CD4+ T cell dysfunction.

immunology↗

bioRxiv2024

Protection against experimental cryptococcosis elicited by Cationic Adjuvant Formulation 01-adjuvanted subunit vaccines

The fungal infection, cryptococcosis, is responsible for >100,000 deaths annually. No licensed vaccines are available. We explored the efficacy and immune responses of subunit cryptococcal vaccines adjuvanted with Cationic Adjuvant Formulation 01 (CAF01). CAF01 promotes humoral and T helper (Th) 1 and Th17 immune responses and has been safely used in human vaccine trials. Four subcutaneous vaccines, each containing single recombinant Cryptococcus neoformans protein antigens, partially protected mice from experimental cryptococcosis. Protection increased, up to 100%, in mice that received bivalent and quadrivalent vaccine formulations. Vaccinated mice that received a pulmonary challenge with C. neoformans had an influx of leukocytes into the lung including robust numbers of polyfunctional CD4+ T cells which produced Interferon gamma (IFN{gamma}), tumor necrosis factor alpha (TNF), and interleukin (IL)-17 upon ex vivo antigenic stimulation. Cytokine-producing lung CD8+ T cells were also found, albeit in lesser numbers. A significant, durable IFN{gamma} response was observed in the lungs, spleen, and blood. Moreover, IFN{gamma} secretion following ex vivo stimulation directly correlated with fungal clearance in the lungs. Thus, we have developed multivalent cryptococcal vaccines which protect mice from experimental cryptococcosis using an adjuvant which has been safely tested in humans. These preclinical studies suggest a path towards human cryptococcal vaccine trials. Author summaryCryptococcosis is a fungal infection that poses great challenges to public health, especially in resource-limited regions with high HIV prevalence. Despite the urgent need, no licensed vaccines are currently available. In this study, we used a lethal mouse model of cryptococcosis to explore protection and immune responses elicited by vaccines consisting of recombinant cryptococcal proteins formulated with CAF01, an adjuvant that has an established safety and immunogenicity profile in human clinical vaccine trials. We discovered that while vaccines containing a single protein partially protected mouse strains, the protection was greatly augmented when the mice received vaccines formulated with multiple antigens. The lungs of vaccinated and infected mice had a robust influx of CD4+ T cells, many of which made the cytokines IFN{gamma} and IL-17 when stimulated ex vivo. Moreover, we found the production of IFN{gamma} directly correlated with clearance of fungi from the lungs. Cytotoxic CD8+ T cell responses were also observed, albeit in lesser numbers. Our promising findings from this preclinical research paves the way for future human cryptococcal vaccine trials.

immunology↗

bioRxiv2023

Dysregulated Pulmonary Inflammatory Responses Exacerbate the Outcome of Secondary Aspergillosis Following Influenza

Inhalation of airborne conidia of the ubiquitous fungus Aspergillus fumigatus commonly occurs but invasive aspergillosis is rare except in profoundly immunocompromised persons. Severe influenza predisposes patients to invasive pulmonary aspergillosis by mechanisms that are poorly defined. Using a post-influenza aspergillosis model, we found that superinfected mice had 100% mortality when challenged with A. fumigatus conidia on days 2 and 5 (early stages) of influenza A virus infection but 100% survival when challenged on days 8 and 14 (late stages). Influenza-infected mice superinfected with A. fumigatus had increased levels of the pro-inflammatory cytokines and chemokines IL-6, TNF, IFN{beta}, IL-12p70, IL-1, IL-1{beta}, CXCL1, G-CSF, MIP-1, MIP-1{beta}, RANTES and MCP-1. Surprisingly, on histopathological analysis, superinfected mice did not have greater lung inflammation compared with mice infected with influenza alone. Mice infected with influenza had dampened neutrophil recruitment to the lungs following subsequent challenge with A. fumigatus, but only if the fungal challenge was executed during the early stages of influenza infection. However, influenza infection did not have a major effect on neutrophil phagocytosis and killing of A. fumigatus conidia. Moreover, minimal germination of conidia was seen on histopathology even in the superinfected mice. Taken together, our data suggest that the high mortality rate seen in mice during the early stages of influenza-associated pulmonary aspergillosis is multifactorial, with a greater contribution from dysregulated inflammation than microbial growth. ImportanceSevere influenza is a risk factor for fatal invasive pulmonary aspergillosis; however, the mechanistic basis for the lethality is unclear. Utilizing an influenza-associated pulmonary aspergillosis (IAPA) model, we found that mice infected with influenza A virus followed by A. fumigatus had 100% mortality when superinfected during the early stages of influenza but survived at later stages. While superinfected mice had dysregulated pulmonary inflammatory responses compared to controls, they had neither increased inflammation nor extensive fungal growth. Although influenza-infected mice had dampened neutrophil recruitment to the lungs following subsequent challenge with A. fumigatus, influenza did not affect the ability of neutrophils to clear the fungi. Our data suggest that the lethality seen in our model IAPA is multifactorial with dysregulated inflammation being a greater contributor than uncontrollable microbial growth. If confirmed in humans, our findings provide a rationale for clinical studies of adjuvant anti-inflammatory agents in the treatment of IAPA.

immunology↗