Biology subjects

Littlefield, K.

Publications and source records attributed to Littlefield, K..

5 recordsLinked to original sources

bioRxiv2026

A bivalent Lassa virus mRNA vaccine protects guinea pigs from lethal infection with Lassa virus

Lassa virus (LASV), the causative agent of the life-threatening febrile disease, Lassa fever, remains a major public health concern in West Africa, where hundreds of thousands of infections occur annually. However, no licensed vaccine is currently available, highlighting the urgent need for effective preventive measures. We previously demonstrated that an mRNA-lipid nanoparticle (LNP) vaccine expressing LASV glycoprotein precursor (GPC; LASgpc-mRNA-LNP) conferred protection against lethal infection with a recombinant lymphocytic choriomeningitis virus expressing LASV GPC in mice. In this study, we extended our previous work with the aim of evaluating the efficacy of an mRNA-LNP vaccine expressing LASV nucleoprotein (NP; LASnp-mRNA-LNP) and a bivalent vaccine combining LASgpc-mRNA-LNP and LASnp-mRNA-LNP. Using a lethal CBA/N mouse model of infection with ML29, an LASV live-attenuated vaccine candidate encoding LASV GPC and NP, we found that LASgpc-mRNA-LNP and LASnp-mRNA-LNP each conferred protection in the absence of detectable neutralizing antibody responses. We identified LASV GPC- and NP-derived CD4 and CD8 T-cell epitope peptides in CBA/N mice and demonstrated that vaccination induced robust antigen-specific T-cell responses. Importantly, the bivalent vaccine provided complete protection against lethal challenge with doses at which monovalent vaccines failed to protect all mice, suggesting a potential dose-sparing benefit of the bivalent formulation. Furthermore, the bivalent vaccine fully protected guinea pigs against lethal challenge with authentic LASV. Together, these findings establish LASV NP, in addition to GPC, as a protective antigen in the mRNA vaccine platform and provide a rationale for developing bivalent mRNA-LNP vaccines to improve protection against Lassa fever.

microbiology↗

bioRxiv2022

SARS-CoV-2-specific T cells associate with reduced lung function and inflammation in pulmonary post-acute sequalae of SARS-CoV-2

As of January 2022, at least 60 million individuals are estimated to develop post-acute sequelae of SARS-CoV-2 (PASC) after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While elevated levels of SARS-CoV-2-specific T cells have been observed in non-specific PASC, little is known about their impact on pulmonary function which is compromised in the majority of these individuals. This study compares frequencies of SARS-CoV-2-specific T cells and inflammatory markers with lung function in participants with pulmonary PASC and resolved COVID-19 (RC). Compared to RC, participants with respiratory PASC had up to 34-fold higher frequencies of IFN-{gamma}- and TNF--producing SARS-CoV-2-specific CD4+ and CD8+ T cells in peripheral blood and elevated levels of plasma CRP and IL-6. Importantly, in PASC participants the frequency of TNF--producing SARS-CoV-2-specific CD4+ and CD8+ T cells, which exhibited the highest levels of Ki67 indicating they were activity dividing, correlated positively with plasma IL-6 and negatively with measures of lung function, including forced expiratory volume in one second (FEV1), while increased frequencies of IFN-{gamma}-producing SARS-CoV-2-specific T cells associated with prolonged dyspnea. Statistical analyses stratified by age, number of comorbidities and hospitalization status demonstrated that none of these factors affect differences in the frequency of SARS-CoV-2 T cells and plasma IL-6 levels measured between PASC and RC cohorts. Taken together, these findings demonstrate elevated frequencies of SARS-CoV-2-specific T cells in individuals with pulmonary PASC are associated with increased systemic inflammation and decreased lung function, suggesting that SARS-CoV-2-specific T cells contribute to lingering pulmonary symptoms. These findings also provide mechanistic insight on the pathophysiology of PASC that can inform development of potential treatments to reduce symptom burden. Author SummaryLong COVID-19 or post-acute sequelae of SARS-CoV-2 (PASC) impacts 20-30% of those infected with SARS-CoV-2 and is characterized by COVID-19 symptoms exceeding 4 weeks from symptom onset. While those with PASC experience a wide variety of persistent symptoms including shortness of breath, cough, chest pain, irregular heartbeat, brain fog, fatigue, and intermittent fever, lung-related conditions are the most common. Although, infection with SARS-CoV-2 is clearly the inciting factor for PASC, the mechanisms responsible for long-term lung dysfunction are unclear and current treatments are ineffective at resolving pulmonary symptoms. Generalized PASC has been associated with SARS-CoV-2-specific T cells, a component of adaptive immunity, suggesting that residual virus may persist. Here, we investigated the frequency and function of virus-specific T cells in the blood of individuals with pulmonary PASC and correlated their presence with systemic inflammation and lung function. Our findings demonstrated that T cells specific for SARS-CoV-2 are elevated in the blood of those with pulmonary PASC and are associated with increased IL-6, a cytokine strongly associated with COVID-19 severity, and decreased lung function. These findings provide mechanistic insight into the pathophysiology of pulmonary PASC needed for the development of new treatments to improve quality of life for those affected.

immunology↗

bioRxiv2021

A bacterial extracellular vesicle-based intranasal vaccine against SARS-CoV-2

Several vaccines have been introduced to combat the coronavirus infectious disease-2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current SARS-CoV-2 vaccines include mRNA-containing lipid nanoparticles or adenoviral vectors that encode the SARS-CoV-2 Spike (S) protein of SARS-CoV-2, inactivated virus, or protein subunits. Despite growing success in worldwide vaccination efforts, additional capabilities may be needed in the future to address issues such as stability and storage requirements, need for vaccine boosters, desirability of different routes of administration, and emergence of SARS-CoV-2 variants such as the Delta variant. Here, we present a novel, well-characterized SARS-CoV-2 vaccine candidate based on extracellular vesicles (EVs) of Salmonella typhimurium that are decorated with the mammalian cell culture-derived Spike receptor-binding domain (RBD). RBD-conjugated outer membrane vesicles (RBD-OMVs) were used to immunize the golden Syrian hamster (Mesocricetus auratus) model of COVID-19. Intranasal immunization resulted in high titers of blood anti-RBD IgG as well as detectable mucosal responses. Neutralizing antibody activity against wild-type and Delta variants was evident in all vaccinated subjects. Upon challenge with live virus, hamsters immunized with RBD-OMV, but not animals immunized with unconjugated OMVs or a vehicle control, avoided body mass loss, had lower virus titers in bronchoalveolar lavage fluid, and experienced less severe lung pathology. Our results emphasize the value and versatility of OMV-based vaccine approaches.

immunology↗

bioRxiv2021

Sex differences in lung imaging and SARS-CoV-2 antibody responses in a COVID-19 golden Syrian hamster model

In the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more severe outcomes are reported in males compared with females, including hospitalizations and deaths. Animal models can provide an opportunity to mechanistically interrogate causes of sex differences in the pathogenesis of SARS-CoV-2. Adult male and female golden Syrian hamsters (8-10 weeks of age) were inoculated intranasally with 105 TCID50 of SARS-CoV-2/USA-WA1/2020 and euthanized at several time points during the acute (i.e., virus actively replicating) and recovery (i.e., after the infectious virus has been cleared) phases of infection. There was no mortality, but infected male hamsters experienced greater morbidity, losing a greater percentage of body mass, developing more extensive pneumonia as noted on chest computed tomography, and recovering more slowly than females. Treatment of male hamsters with estradiol did not alter pulmonary damage. Virus titers in respiratory tissues, including nasal turbinates, trachea, and lungs, and pulmonary cytokine concentrations, including IFN{beta} and TNF, were comparable between the sexes. However, during the recovery phase of infection, females mounted two-fold greater IgM, IgG, and IgA responses against the receptor-binding domain of the spike protein (S-RBD) in both plasma and respiratory tissues. Female hamsters also had significantly greater IgG antibodies against whole inactivated SARS-CoV-2 and mutant S-RBDs, as well as virus neutralizing antibodies in plasma. The development of an animal model to study COVID-19 sex differences will allow for a greater mechanistic understanding of the SARS-CoV-2 associated sex differences seen in the human population. ImportanceMen experience more severe outcomes from COVID-19 than women. Golden Syrian hamsters were used to explore sex differences in the pathogenesis of a human clinical isolate of SARS-CoV-2. After inoculation, male hamsters experienced greater sickness, developed more severe lung pathology, and recovered more slowly than females. Sex differences in disease could not be reversed by estradiol treatment in males and were not explained by either virus replication kinetics or the concentrations of inflammatory cytokines in the lungs. During the recovery period, antiviral antibody responses in the respiratory tract and plasma, including to newly emerging SARS-CoV-2 variants, were greater in females than male hamsters. Greater lung pathology during the acute phase combined with reduced antiviral antibody responses during the recovery phase of infection in males than females illustrate the utility of golden Syrian hamsters as a model to explore sex differences in the pathogenesis of SARS-CoV-2 and vaccine-induced immunity and protection. One Sentence SummaryFollowing SARS-CoV-2 infection, male hamsters experience worse clinical disease and have lower antiviral antibody responses than females.

microbiology↗

bioRxiv2020

CD8+ T cell responses in convalescent COVID-19 individuals target epitopes from the entireSARS-CoV-2 proteome and show kinetics of early differentiation

Characterization of the T cell response in individuals who recover from SARS-CoV-2 infection is critical to understanding its contribution to protective immunity. A multiplexed peptide-MHC tetramer approach was used to screen 408 SARS-CoV-2 candidate epitopes for CD8+ T cell recognition in a cross-sectional sample of 30 COVID-19 convalescent individuals. T cells were evaluated using a 28-marker phenotypic panel, and findings were modelled against time from diagnosis, humoral and inflammatory responses. 132 distinct SARS-CoV-2-specific CD8+ T cell epitope responses across six different HLAs were detected, corresponding to 52 unique reactivities. T cell responses were directed against several structural and non-structural virus proteins. Modelling demonstrated a coordinated and dynamic immune response characterized by a decrease in inflammation, increase in neutralizing antibody titer, and differentiation of a specific CD8+ T cell response. Overall, T cells exhibited distinct differentiation into stem-cell and transitional memory states, subsets, which may be key to developing durable protection.

immunology↗