Protective Immunity of COVID-19 Vaccination with ChAdOx1 nCoV-19 Following Previous SARS-CoV-2 Infection: A Humoral and Cellular Investigation.

Infections caused by SARS-CoV-2 induce a severe acute respiratory syndrome called COVID-19 and have led to more than six million deaths worldwide. Vaccination is the most effective preventative measure, and cellular and humoral immunity is crucial to developing individual protection. Here, we aim to investigate hybrid immunity against SARS-CoV-2 triggered by the ChAadOx1 nCoV-19 vaccine in a Brazilian cohort. We investigated the immune response from ChAadOx1 nCoV-19 vaccination in naïve (noCOVID-19) and previously infected individuals (COVID-19) by analyzing levels of D-dimers, total IgG, neutralizing antibodies (Nabs), IFN-γ (interferon-γ) secretion, and immunophenotyping of memory lymphocytes. No significant differences in D-dimer levels were observed 7 or 15 days after vaccination (DAV). All vaccinated individuals presented higher levels of total IgG or Nabs with a positive correlation (R = 0.88). Individuals in the COVID-19 group showed higher levels of antibody and memory B cells, with a faster antibody response starting at 7 DAV compared to noCOVID-19 at 15 DAV. Further, ChAadOx1 nCoV-19 vaccination led to enhanced IFN-γ production (15 DAV) and an increase in activated T CD4+ naïve cells in noCOVID-19 individuals in contrast with COVID-19 individuals. Hence, our data support that hybrid immunity triggered by ChAadOx1 nCoV-19 vaccination is associated with enhanced humoral response, together with a balanced cellular response.

Exploratory study of humoral and cellular immunity to 17DD Yellow Fever vaccination in children and adults residents of areas without circulation of Yellow Fever Virus.

The present investigation comprised two independent observational arms to evaluate the influence of pre-existing flavivirus humoral immunity and the age-impact on 17DD-YF vaccination immunity. Flavivirus (YFV; DENV; ZIKV) serology and YF-specific cellular immunity was evaluated in 288 children/9Mths-4Yrs and 288 adults/18-49Yrs residents of areas without YFV circulation. Data demonstrated that flavivirus seropositivity at baseline was higher in Adults as compared to Children (26%;87%;67% vs 6%;13%;15%, respectively). The heterologous flavivirus seropositivity (DENV; ZIKV) did not impact the YF-specific cellular immune response at baseline. However, higher levels of NCD4, EMCD8, IFN-MCD8, NCD19 and nCMCD19 were observed in subjects with pre-existing YFV seropositivity. Primary vaccination of YFV-seronegative volunteers led to higher levels of YF-neutralizing antibodies in Adults as compared to Younger Children (9Mths-2Yrs). Although similar seropositivity rates observed amongst Children and Adults at D30-45, lower rates were observed in Younger Children (9Mths-2Yrs) at D365 (94%;95%;100% vs 87%;96%;99%, respectively). A progressive decline in antibody levels were reported at D365, being more expressive in Children as compared to Adults. All age-subgroups exhibited at D30-45 increased levels of eEfCD4, EMCD4, IFN-MCD8 and nCMCD19 together with a decrease of eEfCD8 and CMCD8. While an increase of EMCD8 were observed in all subgroups at D30-45, a declined duration at D365 was reported only in Younger Children (9Mths-2Yrs). Biomarker signatures further support that only Younger Children (9Mths-2Yrs) presented a progressive decline of EMCD8 at D365. Together, these findings demonstrated that regardless the similarities observed in YF-neutralizing antibodies, the age impacts the duration of cellular immune response to primary 17DD-YF vaccination.

Immunogenicity and safety of primary fractional-dose yellow fever vaccine in autoimmune rheumatic diseases.

BACKGROUND: Brazil faced a yellow fever(YF) outbreak in 2016-2018 and vaccination was considered for autoimmune rheumatic disease patients(ARD) with low immunosuppression due to YF high mortality. OBJECTIVE: This study aimed to evaluate, prospectively for the first time, the short-term immunogenicity of the fractional YF vaccine(YFV) immunization in ARD patients with low immunossupression. METHODS AND RESULTS: A total of 318 participants(159 ARD and 159 age- and sex-matched healthy controls) were vaccinated with the fractional-dose(one fifth) of 17DD-YFV. All subjects were evaluated at entry(D0), D5, D10, and D30 post-vaccination for clinical/laboratory and disease activity parameters for ARD patients. Post-vaccination seroconversion rate(83.7%vs.96.6%, p = 0.0006) and geometric mean titers(GMT) of neutralizing antibodies[1143.7 (95%CI 1012.3-1292.2) vs.731 (95%CI 593.6-900.2), p<0.001] were significantly lower in ARD compared to controls. A lower positivity rate of viremia was also identified for ARD patients compared to controls at D5 (53%vs.70%, p = 0.005) and the levels persisted in D10 for patients and reduced for controls(51%vs.19%, p = 0.0001). The viremia was the only variable associated with seroconvertion. No serious adverse events were reported. ARD disease activity parameters remained stable at D30(p>0.05). CONCLUSION: Fractional-dose 17DD-YF vaccine in ARD patients resulted in a high rate of seroconversion rate(>80%) but lower than controls, with a longer but less intense viremia. This vaccine was immunogenic, safe and did not induce flares in ARD under low immunosuppression and may be indicated in YF outbreak situations and for patients who live or travel to endemic areas. TRIAL REGISTRATION: This clinical trial was registered with Clinicaltrials.gov (#NCT03430388).

Survey on Non-Human Primates and Mosquitoes Does not Provide Evidences of Spillover/Spillback between the Urban and Sylvatic Cycles of Yellow Fever and Zika Viruses Following Severe Outbreaks in Southeast Brazil.

In the last decade, Flaviviruses such as yellow fever (YFV) and Zika (ZIKV) have expanded their transmission areas. These viruses originated in Africa, where they exhibit both sylvatic and interhuman transmission cycles. In Brazil, the risk of YFV urbanization has grown, with the sylvatic transmission approaching the most densely populated metropolis, while concern about ZIKV spillback to a sylvatic cycle has risen. To investigate these health threats, we carried out extensive collections and arbovirus screening of 144 free-living, non-human primates (NHPs) and 5219 mosquitoes before, during, and after ZIKV and YFV outbreaks (2015-2018) in southeast Brazil. ZIKV infection was not detected in any NHP collected at any time. In contrast, current and previous YFV infections were detected in NHPs sampled between 2017 and 2018, but not before the onset of the YFV outbreak. Mosquito pools screened by high-throughput PCR were positive for YFV when captured in the wild and during the YFV outbreak, but were negative for 94 other arboviruses, including ZIKV, regardless of the time of collection. In conclusion, there was no evidence of YFV transmission in coastal southeast Brazil before the current outbreak, nor the spread or establishment of an independent sylvatic cycle of ZIKV or urban Aedes aegypti transmission of YFV in the region. In view of the region's receptivity and vulnerability to arbovirus transmission, surveillance of NHPs and mosquitoes should be strengthened and continuous.

Evidence for Tissue Toxicity in BALB/c Exposed to a Long-Term Treatment with Oxiranes Compared to Meglumine Antimoniate.

Leishmaniasis remains a serious public health problem in developing countries without effective control, whether by vaccination or chemotherapy. Part of the failure of leishmaniasis control is due to the lack of new less toxic and more effective drugs able to eliminate both the lesions and the parasite. Oxiranes derived from naphthoquinones now being assayed are promising drugs for the treatment of this group of diseases. The predicted pharmacokinetic properties and toxicological profiles of epoxy-α-lapachone and epoxymethoxy-lawsone have now been compared to those of meglumine antimoniate, and histological changes induced by these drugs in noninfected BALB/c mice tissues are described. Effects of these compounds on liver, kidney, lung, heart, and cerebral tissues of healthy mice were examined. The data presented show that both these oxiranes and meglumine antimoniate induce changes in all BALB/c mice tissues, with the lung, heart, and brain being the most affected. Epoxymethoxy-lawsone was the most toxic to lung tissue, while most severe damage was caused in the heart by epoxy-α-lapachone. Meglumine antimoniate caused mild-to-moderate changes in heart and lung tissues.

Desenvolvimento de vacinas de DNA contra o vírus da dengue baseadas na proteína do envelope viral / Development of DNA vaccines against dengue virus based on viral envelope protein

A dengue é uma doença causada pelo vírus da dengue (DENV1- 4). Apesar dos vários estudos, ainda não existe uma vacina comercialmente disponível. A proteína do envelope (E) de DENV apresenta-se como o maior componente protéico da superfície viral. Conseqüentemente, esta proteína é o principal alvo para a indução de uma resposta imune protetora, provavelmente baseada em anticorpos neutralizantes. No presente trabalho, nós avaliamos o potencial protetor de vacinas de DNA baseadas na proteína E de DENV2. para isto, foram construídos dois pasmídeos, pE1D2 e pE2D2, que contêm as seqüências que codificam o eCtodomínio da proteína E (domínios I, II e III) ou somente o seu domínio III, respectivamente, clonadas da montante à seqüência que codifica o peptídeo sinal do ativador de plasminogênio de tecido humano (t-PA). Os dois plasmídeos mediaram à expressão e secreção das proteínas recombinantes in vitro em células eucarióticas, detectadas com anticorpos anti-DENV2 e avaliadas por ensaios de imunofluorescência ou marcação metabólica seguida de imunoprecipitação. Ambas as vacinas de DNA foram capazes de induzir respostas imunes com produção de anticorpos neutralizantes em camundongos Balb/c, com títulos mais elevados nos animais imunizados com o pE1D2. A vacina Pe1D2 também se mostrou mais protetora nos testes de desafio com uma dose letal de DENV2, induzindo 100 porcento de sobrevivência nos camundongos imunizados, enquanto que 45 porcento dos animais vacinados com o plasmídeo Pe2D2 morreram após a infecção. Além disso, 10 porcento e 65 porcentodos camundongos imunizados com pE1D2 e pE2D2, respectivamente, apresentaram morbidade frente ao desafio letal. As vacinas pE1D2 e pE2D2 também foram testadas combinadas com o vírus quimérico YF17D-D2, em um sistema de dose e reforço ou em imunizações simultâneas. O vírus quimérico YF17D menos D2 foi construído com a substituição dos genes prM e E do vírus vacinal da febre amarela 17DD pelos genes prM e E de DENV2. a vacina de DNA pE1D2 combinada com a quimera YF17D menos D2 induziu altos níveis de anticorpos neutralizantes nos animais vacinados com os diferentes esquemas de imunização. Além disso, esses animais apresentaram 100 porcento de sobrevivência frente ao desafio letal com DENV2, com ausência de qualquer sinal clinico da infecção. O efeito sinérgico da imunização combinada também foi evidenciado quando combinamos a vacina pE2D2 e YF17D menos D2, que gerou 100 porcento de sobrevivência nos animais desafiados. A resposta imune celular foi avaliada pela produção de IFN- por células TCD8 mais em ensaios de ELISPOT, evidenciando a ativação destas células nos animais imunizados com as pE1D2 independente da sua combinação com a quimera YF17D menos D2. Além disso, a análise do perfil fenotípico das células TCD4 a mais e TCD8 mais mostrou um percentual menor de linfócitos CD62L mais nos animais vacinados com o pE1D2 isolado ou combinado com o vírus quimérico, indicando que a vacina de DNA pode influenciar nos processos de ativação das células T. Posteriormente, foram construídas novas vacinas de DNA que codificam os ectodomínios da proteína E de DENV1, 3 e 4 (pE1D1, pE1D3 e pE1D4), cuja expressão foi confirmada in vitro, e que serão testadas futuramente em modelos animais.