Neotropical Sylvatic Mosquitoes and Aedes aegypti Are Not Competent to Transmit 17DD Attenuated Yellow Fever Virus from Vaccinated Viremic New World Non-Human Primates.

Beside humans, thousands of non-human primates (NHPs) died during the recent outbreak caused by the yellow fever virus (YFV) in Brazil. Vaccination of NHPs against YFV with the YF 17DD attenuated virus has emerged as a public health strategy, as it would reduce sylvatic transmission while also preserving endangered susceptible species. The hypothesis of establishing an uncontrolled transmission of this attenuated virus in nature was raised. We assessed vector competence of four sylvatic mosquito species, Haemagogus leucocelaenus, Haemagogus janthinomys/capricornii, Sabethes albiprivus, and Sabethes identicus, as well as the urban vector Aedes aegypti for YF 17DD attenuated vaccine virus when fed directly on eleven viremic lion tamarins or artificially challenged with the same virus. No infection was detected in 689 mosquitoes engorged on viremic lion tamarins whose viremia ranged from 1.05 × 103 to 6.61 × 103 FFU/mL, nor in those artificially taking ≤ 1 × 103 PFU/mL. Low viremia presented by YF 17DD-vaccinated New World NHPs combined with the low capacity and null dissemination ability in sylvatic and domestic mosquitoes of this attenuated virus suggest no risk of its transmission in nature. Thus, vaccination of captive and free-living NHPs against YFV is a safe public health strategy.

Evaluation of Two Adjuvant Formulations for an Inactivated Yellow Fever 17DD Vaccine Candidate in Mice.

The attenuated yellow fever (YF) vaccine is one of the most successful vaccines ever developed. After a single dose administration YF vaccine can induce balanced Th1/Th2 immune responses and long-lasting neutralizing antibodies. These attributes endorsed it as a model of how to properly stimulate the innate response to target protective immune responses. Despite their longstanding success, attenuated YF vaccines can cause rare fatal adverse events and are contraindicated for persons with immunosuppression, egg allergy and age < 6 months and >60 years. These drawbacks have encouraged the development of a non-live vaccine. The aim of the present study is to characterize and compare the immunological profile of two adjuvant formulations of an inactivated YF 17DD vaccine candidate. Inactivated YF vaccine formulations based on alum (Al(OH)3) or squalene (AddaVax®) were investigated by immunization of C57BL/6 mice in 3-dose or 2-dose schedules, respectively, and compared with a single dose of attenuated YF virus 17DD. Sera were analyzed by ELISA and Plaque Reduction Neutralization Test (PRNT) for detection of total IgG and neutralizing antibodies against YF virus. In addition, splenocytes were collected to evaluate cellular responses by ELISpot. Both inactivated formulations were able to induce high titers of IgG against YF, although neutralizing antibodies levels were borderline on pre-challenge samples. Analysis of IgG subtypes revealed a predominance of IgG2a associated with improved neutralizing capacity in animals immunized with the attenuated YF vaccine, and a predominance of IgG1 in groups immunized with experimental non-live formulations (alum and AddaVax®). After intracerebral (IC) challenge, attenuated and inactivated vaccine formulations showed an increase in neutralizing antibodies. The AddaVax®-based inactivated vaccine and the attenuated vaccine achieved 100% protection, and alum-based equivalent formulation achieved 70% protection.

Safety and immunogenicity of 17DD attenuated yellow fever vaccine in howler monkeys (Alouatta spp.).

BACKGROUND: Alouatta spp. are highly susceptible to yellow fever (YF) infection and develop an often fatal disease. The threat posed by an outbreak started in 2016 leads us to investigate vaccination as a potential tool in preventing YF in non-human primates (NHP). METHODS: Susceptible howler monkeys were immunized with three different concentrations of the human Brazilian commercial YF17DD vaccine. Post-vaccination viremia/RNAemia, immunogenicity, and safety were characterized. RESULTS: The vaccine did not produce YF clinical manifestations in any of the NHPs. After immunization, all animals seroconverted demonstrating the ability of the YF vaccine to induce humoral response in Alouatta species. CONCLUSIONS: The present work has demonstrated the safe and immunogenic profile of the existing YF 17DD vaccine in howler monkeys. This knowledge may support further studies with other susceptible monkey species and provide a possible solution for controlling epizootics and preventing the devastation of endangered species.

Vaccines for neglected and emerging diseases in Brazil by 2030: the "valley of death" and opportunities for RD&I in Vaccinology 4.0.

We examine the implications of the very low competitiveness of the Brazilian vaccine RD&I system, which precludes the development of all the important vaccines required by the National Immunization Program (NIP), severely impacting the healthcare of the population. In a country dramatically affected by COVID-19 pandemic and by an exponential increase in emerging and neglected diseases, particularly the poor, these RD&I constraints for vaccines become crucial governance issues. Such constraints are aggravated by a global scenario of limited commercial interest from multinational companies in vaccines for neglected and emerging diseases, which are falling into a "valley of death," with only two vaccines produced in a pipeline of 240 vaccines. We stress that these constraints in the global pipeline are a window of opportunity for vaccine manufacturers in Brazil and other developing countries in the current paradigm transition towards Vaccinology 4.0. We conclude with recommendations for a new governance strategy supporting Brazilian public vaccine manufacturers in international collaborations for a sustainable national vaccine development and production plan by 2030.

Regulatory evolution and challenges from the perspective of public laboratiories vaccine producers in Brazil. / A evolução regulatória e os desafios na perspectiva dos laboratórios públicos produtores de vacinas no Brasil.

The regulation of biological products has evolved rapidly in recent years due to quality issues impacting people's lives and the advent of new technologies, with constant changes in regulations that dictate how a product is registered, produced, and monitored. In the case of vaccines, the responsibility of regulators and manufacturers in guaranteeing quality, safety, and efficacy is even more critical, since vaccines are mostly used in children and healthy patients. In this scenario, manufacturers need to create strategies to keep their products and installations adequate and up-to-date with a fully operational quality system. Meanwhile, regulatory agencies have the role of guaranteeing that products meet the established criteria without compromising the supply of medicines to the population.

A regulamentação para produtos biológicos vem evoluindo rapidamente ao longo dos últimos anos, seja motivada por questões de qualidade com impacto na vida das pessoas, seja pelo advento de novas tecnologias. As mudanças nas regulamentações que ditam como um produto deve ser registrado, produzido e monitorado são constantes. A responsabilidade de reguladores e fabricantes na garantia da qualidade, segurança e eficácia das vacinas torna-se ainda mais crítica, uma vez que essas substâncias são utilizadas, em sua maioria, em crianças e em pacientes saudáveis. Diante desse cenário, fabricantes precisam criar estratégias para manter seus produtos e instalações adequadas e um sistema da qualidade atualizado e operante. Por outro lado, as agências reguladoras têm o papel de garantir que os produtos que estão em uso atendam aos critérios estabelecidos, sem comprometer o fornecimento de medicamentos para a população.

La regulación para productos biológicos ha evolucionado rápidamente a lo largo de los últimos años, sea motivada por cuestiones de calidad con impacto en la vida de las personas, o por el advenimiento de nuevas tecnologías. Los cambios en las regulaciones que dictan como un producto debe ser registrado, producido y monitoreado son constantes. La responsabilidad de reguladores y fabricantes en la garantía de la calidad, seguridad y eficacia de las vacunas se convierte en algo todavía más crítico, ya que estas sustancias se utilizan, en su mayoría, en niños y pacientes saludables. Ante este escenario, los fabricantes necesitan crear estrategias para mantener sus productos e instalaciones de forma adecuada, además de un sistema de calidad actualizado y operativo. Por otro lado, las agencias reguladoras tienen el papel de garantizar que los productos que están en uso atiendan a los criterios establecidos, sin comprometer el suministro de medicamentos para la población.

Vaccines for neglected and emerging diseases in Brazil by 2030: the valley of death and opportunities for RD& I in Vaccinology 4. 0 / Vacunas en Brasil para enfermedades emergentes y olvidadas en 2030: el valle de la muerte y oportunidades para RD& I en Vacunología 4. 0 / Vacinas para doenças negligenciadas e emergentes no Brasil até 2030: o vale da morte e oportunidades para PD& I na Vacinologia 4. 0

Abstract: We examine the implications of the very low competitiveness of the Brazilian vaccine RD&I system, which precludes the development of all the important vaccines required by the National Immunization Program (NIP), severely impacting the healthcare of the population. In a country dramatically affected by COVID-19 pandemic and by an exponential increase in emerging and neglected diseases, particularly the poor, these RD&I constraints for vaccines become crucial governance issues. Such constraints are aggravated by a global scenario of limited commercial interest from multinational companies in vaccines for neglected and emerging diseases, which are falling into a "valley of death," with only two vaccines produced in a pipeline of 240 vaccines. We stress that these constraints in the global pipeline are a window of opportunity for vaccine manufacturers in Brazil and other developing countries in the current paradigm transition towards Vaccinology 4.0. We conclude with recommendations for a new governance strategy supporting Brazilian public vaccine manufacturers in international collaborations for a sustainable national vaccine development and production plan by 2030.

Resumen: Examinamos las implicaciones de la muy baja competitividad del sistema brasileño de ID&I de vacunas, que imposibilita el desarrollo de todas las vacunas importantes, requeridas por el Progrma Nacional de Inmunización (PNI), con impactos muy graves en la salud de la población de un país con 200 millones de habitantes. En un país gravemente afectado por la pandemia de COVID-19 y por enfermedades emergentes y olvidadas que afectan particularmente a los pobres, estas restricciones del ID&I para vacunas es, de hecho, un asunto crucial de gobierno. Estas limitaciones locales se han visto agravadas por un escenario global de interés comercial limitado, por parte de las compañías multinacionales, en vacunas para enfermedades emergentes y olvidadas, que están cayendo en un "valle de la muerte", con solamente dos vacunas producidas a nivel global frente a 240 vacunas. Identificamos en estas limitaciones globales una ventana de oportunidad para los fabricantes de vacunas en Brasil y otros países en desarrollo dentro del paradigma actual de transición hacia la Vacunología 4.0. Concluimos con recomendaciones de una nueva estrategia de gobierno que apoye a los fabricantes brasileños de vacunas públicas en colaboraciones internacionales para el plan nacional de desarrollo y producción sostenible de vacunas en 2030.

Resumo: Examinamos as implicações da competitividade tão baixa do sistema brasileiro de pesquisa, desenvolvimento e inovação (PD&I) de vacinas, que impede o desenvolvimento de todas as vacinas importantes requeridas pelo Programa Nacional de Imunizações (PNI), prejudicando gravemente a saúde da população. Em um país seriamente afetado pela pandemia de COVID-19 e por um aumento exponencial de doenças emergentes e negligenciadas, principalmente entre os brasileiros pobres, essas restrições de PD&I quanto às vacinas tornam-se questões cruciais de governança. Essas restrições são agravadas por um cenário global de interesse comercial limitado por parte das empresas multinacionais de vacinas para doenças negligenciadas e emergentes, que estão caindo em um "vale da morte", com apenas duas vacinas produzidas em um pipeline de 240 vacinas. Ressaltamos que essas restrições na produção global constituem uma janela de oportunidade para os fabricantes de vacinas no Brasil e em outros países em desenvolvimento na atual transição de paradigma para a Vacinologia 4.0. Concluímos com recomendações para uma nova estratégia de governança em suporte aos fabricantes públicos de vacinas no Brasil em colaborações internacionais para um plano nacional de desenvolvimento e produção de vacinas que seja sustentável até 2030.

A evolução regulatória e os desafios na perspectiva dos laboratórios públicos produtores de vacinas no Brasil / La evolución regulatoria y los desafíos desde la perspectiva de los laboratorios públicos productores de vacunas en Brasil / Regulatory evolution and challenges from the perspective of public laboratiories vaccine producers in Brazil

A regulamentação para produtos biológicos vem evoluindo rapidamente ao longo dos últimos anos, seja motivada por questões de qualidade com impacto na vida das pessoas, seja pelo advento de novas tecnologias. As mudanças nas regulamentações que ditam como um produto deve ser registrado, produzido e monitorado são constantes. A responsabilidade de reguladores e fabricantes na garantia da qualidade, segurança e eficácia das vacinas torna-se ainda mais crítica, uma vez que essas substâncias são utilizadas, em sua maioria, em crianças e em pacientes saudáveis. Diante desse cenário, fabricantes precisam criar estratégias para manter seus produtos e instalações adequadas e um sistema da qualidade atualizado e operante. Por outro lado, as agências reguladoras têm o papel de garantir que os produtos que estão em uso atendam aos critérios estabelecidos, sem comprometer o fornecimento de medicamentos para a população.

La regulación para productos biológicos ha evolucionado rápidamente a lo largo de los últimos años, sea motivada por cuestiones de calidad con impacto en la vida de las personas, o por el advenimiento de nuevas tecnologías. Los cambios en las regulaciones que dictan como un producto debe ser registrado, producido y monitoreado son constantes. La responsabilidad de reguladores y fabricantes en la garantía de la calidad, seguridad y eficacia de las vacunas se convierte en algo todavía más crítico, ya que estas sustancias se utilizan, en su mayoría, en niños y pacientes saludables. Ante este escenario, los fabricantes necesitan crear estrategias para mantener sus productos e instalaciones de forma adecuada, además de un sistema de calidad actualizado y operativo. Por otro lado, las agencias reguladoras tienen el papel de garantizar que los productos que están en uso atiendan a los criterios establecidos, sin comprometer el suministro de medicamentos para la población.

The regulation of biological products has evolved rapidly in recent years due to quality issues impacting people's lives and the advent of new technologies, with constant changes in regulations that dictate how a product is registered, produced, and monitored. In the case of vaccines, the responsibility of regulators and manufacturers in guaranteeing quality, safety, and efficacy is even more critical, since vaccines are mostly used in children and healthy patients. In this scenario, manufacturers need to create strategies to keep their products and installations adequate and up-to-date with a fully operational quality system. Meanwhile, regulatory agencies have the role of guaranteeing that products meet the established criteria without compromising the supply of medicines to the population.

A evolução regulatória e os desafios na perspectiva dos laboratórios públicos produtores de vacinas no Brasil / La evolución regulatoria y los desafíos desde la perspectiva de los laboratorios públicos productores de vacunas en Brasil / Regulatory evolution and challenges from the perspective of public laboratiories vaccine producers in Brazil

A regulamentação para produtos biológicos vem evoluindo rapidamente ao longo dos últimos anos, seja motivada por questões de qualidade com impacto na vida das pessoas, seja pelo advento de novas tecnologias. As mudanças nas regulamentações que ditam como um produto deve ser registrado, produzido e monitorado são constantes. A responsabilidade de reguladores e fabricantes na garantia da qualidade, segurança e eficácia das vacinas torna-se ainda mais crítica, uma vez que essas substâncias são utilizadas, em sua maioria, em crianças e em pacientes saudáveis. Diante desse cenário, fabricantes precisam criar estratégias para manter seus produtos e instalações adequadas e um sistema da qualidade atualizado e operante. Por outro lado, as agências reguladoras têm o papel de garantir que os produtos que estão em uso atendam aos critérios estabelecidos, sem comprometer o fornecimento de medicamentos para a população.

La regulación para productos biológicos ha evolucionado rápidamente a lo largo de los últimos años, sea motivada por cuestiones de calidad con impacto en la vida de las personas, o por el advenimiento de nuevas tecnologías. Los cambios en las regulaciones que dictan como un producto debe ser registrado, producido y monitoreado son constantes. La responsabilidad de reguladores y fabricantes en la garantía de la calidad, seguridad y eficacia de las vacunas se convierte en algo todavía más crítico, ya que estas sustancias se utilizan, en su mayoría, en niños y pacientes saludables. Ante este escenario, los fabricantes necesitan crear estrategias para mantener sus productos e instalaciones de forma adecuada, además de un sistema de calidad actualizado y operativo. Por otro lado, las agencias reguladoras tienen el papel de garantizar que los productos que están en uso atiendan a los criterios establecidos, sin comprometer el suministro de medicamentos para la población.

The regulation of biological products has evolved rapidly in recent years due to quality issues impacting people's lives and the advent of new technologies, with constant changes in regulations that dictate how a product is registered, produced, and monitored. In the case of vaccines, the responsibility of regulators and manufacturers in guaranteeing quality, safety, and efficacy is even more critical, since vaccines are mostly used in children and healthy patients. In this scenario, manufacturers need to create strategies to keep their products and installations adequate and up-to-date with a fully operational quality system. Meanwhile, regulatory agencies have the role of guaranteeing that products meet the established criteria without compromising the supply of medicines to the population.

Short-Lived Immunity After 17DD Yellow Fever Single Dose Indicates That Booster Vaccination May Be Required to Guarantee Protective Immunity in Children.

The Yellow Fever (YF) vaccination is recommended for people living in endemic areas and represents the most effective strategy to reduce the risk of infection. Previous studies have warned that booster regimens should be considered to guarantee the long-term persistence of 17DD-YF-specific memory components in adults living in areas with YF-virus circulation. Considering the lower seroconversion rates observed in children (9-12 months of age) as compared to adults, this study was designed in order to access the duration of immunity in single-dose vaccinated children in a 10-years cross-sectional time-span. The levels of neutralizing antibodies (PRNT) and the phenotypic/functional memory status of T and B-cells were measured at a baseline, 30-45 days, 1, 2, 4, 7, and 10 years following primary vaccination. The results revealed that a single dose induced 85% of seropositivity at 30-45 days and a progressive time-dependent decrease was observed as early as 2 years and declines toward critical values (below 60%) at time-spans of ≥4-years. Moreover, short-lived YF-specific cellular immunity, mediated by memory T and B-cells was also observed after 4-years. Predicted probability and resultant memory analysis emphasize that correlates of protection (PRNT; effector memory CD8+ T-cells; non-classical memory B-cells) wane to critical values within ≥4-years after primary vaccination. Together, these results clearly demonstrate the decline of 17DD-YF-specific memory response along time in children primarily vaccinated at 9-12 months of age and support the need of booster regimen to guarantee the long-term persistence of memory components for children living in areas with high risk of YF transmission.

Sanger-based sequencing technology for yellow fever vaccine genetic quality control.

Yellow Fever (YF) is an acute viral hemorrhagic disease prevalent mainly in Africa and Americas, with 20-60% fatality rate in severe forms. Currently, antiviral drugs for the infection are not available, reinforcing the importance of vaccination in resident populations and travelers. Manufactured in 7 different countries, the YF vaccine was first created in 1937 and two substrains are used for production, 17DD and 17D-204. The vaccine produced in Bio-Manguinhos/Brazil uses 17DD substrain and more than 160 million doses have been exported to over 74 countries. The World Health Organization (WHO) recommends that new seed- and working-lots should have the viral genome sequenced in order to check vaccine genetic stability. The aim of this study was to develop and standardize a Sanger-based sequencing protocol for the genetic monitoring of the Brazilian 17DD vaccine. We designed 54 oligos to access the complete YF vaccine genome by RT-PCR and sequencing approach. After protocol standardization, we tested 45 vaccine lots and the corresponding secondary and working seed lots. All 45 lots presented 100% nucleotide identity to each other and to the seed lots. We also detected 2 heterogeneous positions at nucleotides 4523 (C/T) and 6673 (C/T) that may indicate a quasispecies diversity of YF 17DD strain. When compared to the Brazilian GenBank sequence YFU17066, the Brazilian 17DD vaccine presented 6 silent mutations. By applying the sequencing methodology to two YF 17D-204 strains, we showed that our method can also be used to sequence different YF vaccine virus. In summary, we have developed a robust method for the genetic monitoring of YF vaccines, which has been successfully applied in Bio-Manguinhos since 2009 and could also be used by other manufacturers for YF17D-based vaccines. There were no genetic variation in the Brazilian tested lots, highlighting the safety, production consistency and, more importantly, the genetic stability of Bio-Manguinhos' YF vaccine in the last 3 decades.

Multi-parameter approach to evaluate the timing of memory status after 17DD-YF primary vaccination.

In this investigation, machine-enhanced techniques were applied to bring about scientific insights to identify a minimum set of phenotypic/functional memory-related biomarkers for post-vaccination follow-up upon yellow fever (YF) vaccination. For this purpose, memory status of circulating T-cells (Naïve/early-effector/Central-Memory/Effector-Memory) and B-cells (Naïve/non-Classical-Memory/Classical-Memory) along with the cytokine profile (IFN/TNF/IL-5/IL-10) were monitored before-NV(day0) and at distinct time-points after 17DD-YF primary vaccination-PV(day30-45); PV(year1-9) and PV(year10-11). A set of biomarkers (eEfCD4; EMCD4; CMCD19; EMCD8; IFNCD4; IL-5CD8; TNFCD4; IFNCD8; TNFCD8; IL-5CD19; IL-5CD4) were observed in PV(day30-45), but not in NV(day0), with most of them still observed in PV(year1-9). Deficiencies of phenotypic/functional biomarkers were observed in NV(day0), while total lack of memory-related attributes was observed in PV(year10-11), regardless of the age at primary vaccination. Venn-diagram analysis pre-selected 10 attributes (eEfCD4, EMCD4, CMCD19, EMCD8, IFNCD4, IL-5CD8, TNFCD4, IFNCD8, TNFCD8 and IL-5CD4), of which the overall mean presented moderate accuracy to discriminate PV(day30-45)&PV(year1-9) from NV(day0)&PV(year10-11). Multi-parameter approaches and decision-tree algorithms defined the EMCD8 and IL-5CD4 attributes as the top-two predictors with moderated performance. Together with the PRNT titers, the top-two biomarkers led to a resultant memory status observed in 80% and 51% of volunteers in PV(day30-45) and PV(year1-9), contrasting with 0% and 29% found in NV(day0) and PV(year10-11), respectively. The deficiency of memory-related attributes observed at PV(year10-11) underscores the conspicuous time-dependent decrease of resultant memory following17DD-YF primary vaccination that could be useful to monitor potential correlates of protection in areas under risk of YF transmission.

Prevalence and titers of yellow fever virus neutralizing antibodies in previously vaccinated adults.

INTRODUCTION:: The World Health Organization (WHO) recommends one single dose of the Yellow Fever (YF) vaccine based on studies of antibody persistency in healthy adults. We assessed the prevalence and titers of YF virus neutralizing antibodies in previously vaccinated persons aged  60 years, in comparison to younger adults. We also evaluated the correlation between antibody titers and the time since vaccination among participants who received one vaccine dose, and the seropositivity among participants vaccinated prior to or within the past 10 years. METHODS:: previously vaccinated healthy persons aged  18 years were included. YF virus neutralizing antibody titers were determined by means of the 50% Plaque Reduction Neutralization Test. RESULTS:: 46 persons aged  60 years and 48 persons aged 18 to 59 years were enrolled. There was no significant difference in the prevalence of YF virus neutralizing antibodies between the two groups (p = 0.263). However, titers were significantly lower in the elderly (p = 0.022). There was no correlation between YF virus neutralizing antibody titers and the time since vaccination. There was no significant difference in seropositivity among participants vaccinated prior to or within the past 10 years. CONCLUSIONS:: the clinical relevance of the observed difference in YF virus neutralizing antibody titers between the two groups is not clear.

Prevalence and titers of yellow fever virus neutralizing antibodies in previously vaccinated adults

ABSTRACT Introduction: The World Health Organization (WHO) recommends one single dose of the Yellow Fever (YF) vaccine based on studies of antibody persistency in healthy adults. We assessed the prevalence and titers of YF virus neutralizing antibodies in previously vaccinated persons aged ≥ 60 years, in comparison to younger adults. We also evaluated the correlation between antibody titers and the time since vaccination among participants who received one vaccine dose, and the seropositivity among participants vaccinated prior to or within the past 10 years. Methods: previously vaccinated healthy persons aged ≥ 18 years were included. YF virus neutralizing antibody titers were determined by means of the 50% Plaque Reduction Neutralization Test. Results: 46 persons aged ≥ 60 years and 48 persons aged 18 to 59 years were enrolled. There was no significant difference in the prevalence of YF virus neutralizing antibodies between the two groups (p = 0.263). However, titers were significantly lower in the elderly (p = 0.022). There was no correlation between YF virus neutralizing antibody titers and the time since vaccination. There was no significant difference in seropositivity among participants vaccinated prior to or within the past 10 years. Conclusions: the clinical relevance of the observed difference in YF virus neutralizing antibody titers between the two groups is not clear.

Persistence of Yellow Fever vaccine-induced antibodies after cord blood stem cell transplant.

We report the case of a cord blood haematopoietic stem cell transplant recipient who was vaccinated for Yellow Fever (YF) 7 days before initiating chemotherapy and had persistent YF antibodies more than 3 years after vaccination. Since the stem cell donor was never exposed to wild YF or to the YF vaccine, and our patient was not exposed to YF or revaccinated, this finding strongly suggests the persistence of recipient immunity. We briefly discuss potential consequences of incomplete elimination of recipient's leukocytes following existing haematopoietic cancer treatments.

Yellow Fever 17DD Vaccine Virus Infection Causes Detectable Changes in Chicken Embryos.

The yellow fever (YF) 17D vaccine is one of the most effective human vaccines ever created. The YF vaccine has been produced since 1937 in embryonated chicken eggs inoculated with the YF 17D virus. Yet, little information is available about the infection mechanism of YF 17DD virus in this biological model. To better understand this mechanism, we infected embryos of Gallus gallus domesticus and analyzed their histopathology after 72 hours of YF infection. Some embryos showed few apoptotic bodies in infected tissues, suggesting mild focal infection processes. Confocal and super-resolution microscopic analysis allowed us to identify as targets of viral infection: skeletal muscle cells, cardiomyocytes, nervous system cells, renal tubular epithelium, lung parenchyma, and fibroblasts associated with connective tissue in the perichondrium and dermis. The virus replication was heaviest in muscle tissues. In all of these specimens, RT-PCR methods confirmed the presence of replicative intermediate and genomic YF RNA. This clearer characterization of cell targets in chicken embryos paves the way for future development of a new YF vaccine based on a new cell culture system.

A DNA vaccine against yellow fever virus: development and evaluation.

Attenuated yellow fever (YF) virus 17D/17DD vaccines are the only available protection from YF infection, which remains a significant source of morbidity and mortality in the tropical areas of the world. The attenuated YF virus vaccine, which is used worldwide, generates both long-lasting neutralizing antibodies and strong T-cell responses. However, on rare occasions, this vaccine has toxic side effects that can be fatal. This study presents the design of two non-viral DNA-based antigen formulations and the characterization of their expression and immunological properties. The two antigen formulations consist of DNA encoding the full-length envelope protein (p/YFE) or the full-length envelope protein fused to the lysosomal-associated membrane protein signal, LAMP-1 (pL/YFE), aimed at diverting antigen processing/presentation through the major histocompatibility complex II precursor compartments. The immune responses triggered by these formulations were evaluated in H2b and H2d backgrounds, corresponding to the C57Bl/6 and BALB/c mice strains, respectively. Both DNA constructs were able to induce very strong T-cell responses of similar magnitude against almost all epitopes that are also generated by the YF 17DD vaccine. The pL/YFE formulation performed best overall. In addition to the T-cell response, it was also able to stimulate high titers of anti-YF neutralizing antibodies comparable to the levels elicited by the 17DD vaccine. More importantly, the pL/YFE vaccine conferred 100% protection against the YF virus in intracerebrally challenged mice. These results indicate that pL/YFE DNA is an excellent vaccine candidate and should be considered for further developmental studies.

Subdoses of 17DD yellow fever vaccine elicit equivalent virological/immunological kinetics timeline.

BACKGROUND: The live attenuated 17DD Yellow Fever vaccine is one of the most successful prophylactic interventions for controlling disease expansion ever designed and utilized in larger scale. However, increase on worldwide vaccine demands and manufacturing restrictions urge for more detailed dose sparing studies. The establishment of complementary biomarkers in addition to PRNT and Viremia could support a secure decision-making regarding the use of 17DD YF vaccine subdoses. The present work aimed at comparing the serum chemokine and cytokine kinetics triggered by five subdoses of 17DD YF Vaccine. METHODS: Neutralizing antibody titers, viremia, cytokines and chemokines were tested on blood samples obtained from eligible primary vaccinees. RESULTS AND DISCUSSION: The results demonstrated that a fifty-fold lower dose of 17DD-YF vaccine (587 IU) is able to trigger similar immunogenicity, as evidenced by significant titers of anti-YF PRNT. However, only subdoses as low as 3,013 IU elicit viremia kinetics with an early peak at five days after primary vaccination equivalent to the current dose (27,476 IU), while other subdoses show a distinct, lower in magnitude and later peak at day 6 post-vaccination. Although the subdose of 587 IU is able to trigger equivalent kinetics of IL-8/CXCL-8 and MCP-1/CCL-2, only the subdose of 3,013 IU is able to trigger similar kinetics of MIG/CXCL-9, pro-inflammatory (TNF, IFN-γ and IL-2) and modulatory cytokines (IL-5 and IL-10). CONCLUSIONS: The analysis of serum biomarkers IFN-γ and IL-10, in association to PRNT and viremia, support the recommendation of use of a ten-fold lower subdose (3,013 IU) of 17DD-YF vaccine.

The Human Hookworm Vaccine.

Hookworm infection is one of the world's most common neglected tropical diseases and a leading cause of iron deficiency anemia in low- and middle-income countries. A Human Hookworm Vaccine is currently being developed by the Sabin Vaccine Institute and is in phase 1 clinical testing. The candidate vaccine is comprised of two recombinant antigens known as Na-GST-1 and Na-APR-1, each of which is an important parasite enzyme required for hookworms to successfully utilize host blood as a source of energy. The recombinant proteins are formulated on Alhydrogel(®) and are being tested in combination with a synthetic Toll-like receptor 4 agonist. The aim of the vaccine is to induce anti-enzyme antibodies that will reduce both host blood loss and the number of hookworms attached to the gut. Transfer of the manufacturing technology to the Oswaldo Cruz Foundation (FIOCRUZ)/Bio-Manguinhos (a Brazilian public sector developing country vaccine manufacturer) is planned, with a clinical development plan that could lead to registration of the vaccine in Brazil. The vaccine would also need to be introduced in the poorest regions of Africa and Asia, where hookworm infection is highly endemic. Ultimately, the vaccine could become an essential tool for achieving hookworm control and elimination, a key target in the 2012 London Declaration on Neglected Tropical Diseases.

Dengue-2 and yellow fever 17DD viruses infect human dendritic cells, resulting in an induction of activation markers, cytokines and chemokines and secretion of different TNF-α and IFN-α profiles.

Flaviviruses cause severe acute febrile and haemorrhagic infections, including dengue and yellow fever and the pathogenesis of these infections is caused by an exacerbated immune response. Dendritic cells (DCs) are targets for dengue virus (DENV) and yellow fever virus (YF) replication and are the first cell population to interact with these viruses during a natural infection, which leads to an induction of protective immunity in humans. We studied the infectivity of DENV2 (strain 16681), a YF vaccine (YF17DD) and a chimeric YF17D/DENV2 vaccine in monocyte-derived DCs in vitro with regard to cell maturation, activation and cytokine production. Higher viral antigen positive cell frequencies were observed for DENV2 when compared with both vaccine viruses. Flavivirus-infected cultures exhibited dendritic cell activation and maturation molecules. CD38 expression on DCs was enhanced for both DENV2 and YF17DD, whereas OX40L expression was decreased as compared to mock-stimulated cells, suggesting that a T helper 1 profile is favoured. Tumor necrosis factor (TNF)-α production in cell cultures was significantly higher in DENV2-infected cultures than in cultures infected with YF17DD or YF17D/DENV. In contrast, the vaccines induced higher IFN-α levels than DENV2. The differential cytokine production indicates that DENV2 results in TNF induction, which discriminates it from vaccine viruses that preferentially stimulate interferon expression. These differential response profiles may influence the pathogenic infection outcome.

Dengue-2 and yellow fever 17DD viruses infect human dendritic cells, resulting in an induction of activation markers, cytokines and chemokines and secretion of different TNF-α and IFN-α profiles

Flaviviruses cause severe acute febrile and haemorrhagic infections, including dengue and yellow fever and the pathogenesis of these infections is caused by an exacerbated immune response. Dendritic cells (DCs) are targets for dengue virus (DENV) and yellow fever virus (YF) replication and are the first cell population to interact with these viruses during a natural infection, which leads to an induction of protective immunity in humans. We studied the infectivity of DENV2 (strain 16681), a YF vaccine (YF17DD) and a chimeric YF17D/DENV2 vaccine in monocyte-derived DCs in vitro with regard to cell maturation, activation and cytokine production. Higher viral antigen positive cell frequencies were observed for DENV2 when compared with both vaccine viruses. Flavivirus-infected cultures exhibited dendritic cell activation and maturation molecules. CD38 expression on DCs was enhanced for both DENV2 and YF17DD, whereas OX40L expression was decreased as compared to mock-stimulated cells, suggesting that a T helper 1 profile is favoured. Tumor necrosis factor (TNF)-α production in cell cultures was significantly higher in DENV2-infected cultures than in cultures infected with YF17DD or YF17D/DENV. In contrast, the vaccines induced higher IFN-α levels than DENV2. The differential cytokine production indicates that DENV2 results in TNF induction, which discriminates it from vaccine viruses that preferentially stimulate interferon expression. These differential response profiles may influence the pathogenic infection outcome.