Comprehensive landscape of neutralizing antibody and cell-mediated response elicited by the 1/5 fractional dose of 17DD-YF primary vaccination in adults.

The present study aimed at evaluating the YF-specific neutralizing antibody profile besides a multiparametric analysis of phenotypic/functional features of cell-mediated response elicited by the 1/5 fractional dose of 17DD-YF vaccine, administered as a single subcutaneous injection. The immunological parameters of each volunteer was monitored at two time points, referred as: before (Day 0) [Non-Vaccinated, NV(D0)] and after vaccination (Day 30-45) [Primary Vaccinees, PV(D30-45)]. Data demonstrated high levels of neutralizing antibodies for PV(D30-45) leading to a seropositivity rate of 93%. A broad increase of systemic soluble mediators with a mixed profile was also observed for PV(D30-45), with IFN-γ and TNF-α presenting the highest baseline fold changes. Integrative network mapping of soluble mediators showed increased correlation numbers in PV(D30-45) as compared to NV(D0) (532vs398). Moreover, PV(D30-45) exhibited increased levels of Terminal Effector (CD45RA+CCR7-) CD4+ and CD8+ T-cells and Non-Classical memory B-cells (IgD+CD27+). Dimensionality reduction of Mass Cytometry data further support these findings. A polyfunctional cytokine profile (TNF-α/IFN-γ/IL-10/IL-17/IL-2) of T and B-cells was observed upon in vitro antigen recall. Mapping and kinetics timeline of soluble mediator signatures for PV(D30-45) further confirmed the polyfunctional profile upon long-term in vitro culture, mediated by increased levels of IFN-γ and TNF-α along with decreased production of IL-10. These findings suggest novel insights of correlates of protection elicited by the 1/5 fractional dose of 17DD-YF vaccine.

Yellow fever - An old foe with new developments.

INTRODUCTION: Yellow fever is caused by an RNA flavivirus. Immunisation in conjunction with vector control is at the forefront of yellow fever control and elimination. OBJECTIVE: This narrative review describes the impact and importance of yellow fever vaccinations for northern Australian health practitioners. DESIGN: Selected key policies, studies and medical guidelines are reviewed and presented. FINDING: Large yellow fever outbreaks, associated with vector spread, have occurred in the last decade in Africa and South America, increasing the risk of international spread of the virus. Mobile populations, like travellers or migrant workers, continue to be at risk of yellow fever. Quality assurance, including yellow fever centre accreditation and initiatives to decrease fraudulent yellow fever vaccination documentation, has evolved in the past few years. Fractional dosing of yellow fever vaccines has been shown to provide protection for 1 year in outbreak scenarios, but further studies are needed. DISCUSSION: Although Australia is yellow fever-free, the disease could be introduced by viraemic persons as a competent Aedes mosquito vector is present in northern Australia. In addition to surveillance and vector control, health education and yellow fever vaccination remain the best lines of defence. In the event of an outbreak, a response via fractional dosing could prove to be effective in controlling the virus. CONCLUSION: Health care providers in northern Australia should be aware of the risks of yellow fever and its introduction to northern Australia and be able to discuss vaccination status with their clients when needed.

Immune response induced by standard and fractional doses of 17DD yellow fever vaccine.

The re-emergence of yellow fever (YF) urged new mass vaccination campaigns and, in 2017, the World Health Organization approved the use of the fractional dose (FD) of the YF vaccine due to stock shortage. In an observational cross-sectional investigation, we have assessed viremia, antibodies, soluble mediators and effector and memory T and B-cells induced by primary vaccination of volunteers with FD and standard dose (SD). Similar viremia and levels of antibodies and soluble markers were induced early after immunization. However, a faster decrease in the latter was observed after SD. The FD led to a sustained expansion of helper T-cells and an increased expression of activation markers on T-cells early after vaccination. Although with different kinetics, expansion of plasma cells was induced upon SD and FD immunization. Integrative analysis reveals that FD induces a more complex network involving follicular helper T cells and B-cells than SD. Our findings substantiate that FD can replace SD inducing robust correlates of protective immune response against YF.

Humoral immunogenicity of primary yellow fever vaccination in infants and children: a systematic review, meta-analysis and meta-regression.

BACKGROUND: Vaccination plays a critical role in mitigating the burden associated with yellow fever (YF). However, there is a lack of comprehensive evidence on the humoral response to primary vaccination in the paediatric population, with several questions debated, including the response when the vaccine is administered at early ages, the effect of co-administration with other vaccines, the duration of immunity and the use of fractional doses, among others. This study summarizes the existing evidence regarding the humoral response to primary YF vaccination in infants and children. METHODS: Studies on the humoral response to primary YF vaccination in children aged 12 years or younger were reviewed. The humoral vaccine response rate (VRR), i.e. the proportion of children who tested positive for vaccine-induced YF-specific neutralizing antibodies, was pooled through random-effects meta-analysis and categorized based on the time elapsed since vaccination. Subgroup, meta-regression and sensitivity analyses were performed. RESULTS: A total of 33 articles met the inclusion criteria, with all but one conducted in countries where YF is endemic. A total of 14 028 infants and children entered this systematic review. Within three months following vaccination, the pooled VRR was 91.9% (95% CI 89.8-93.9). A lower VRR was observed with the 17DD vaccine at the meta-regression analysis. No significant differences in immunogenicity outcomes were observed based on age, administration route, co-administration with other vaccines, or fractional dosing. Results also indicate a decline in VRR over time. CONCLUSIONS: Primary YF vaccination effectively provides humoral immunity in paediatric population. However, humoral response declines over time, and this decline is observable after the first 18 months following vaccination. A differential response according to the vaccine substrain was also observed. This research has valuable implications for stimulating further research on the primary YF vaccination in infants and children, as well as for informing future policies.

Immunological response to fractional-dose yellow fever vaccine administered during an outbreak in Kinshasa, Democratic Republic of the Congo: results 5 years after vaccination from a prospective cohort study.

BACKGROUND: In 2016, outbreaks of yellow fever in Angola and the Democratic Republic of the Congo led to a global vaccine shortage. A fractional dose of 17DD yellow fever vaccine (containing one-fifth [0·1 ml] of the standard dose) was used during a pre-emptive mass campaign in August, 2016, in Kinshasa, Democratic Republic of the Congo among children aged 2 years and older and non-pregnant adults (ie, those aged 18 years and older). 1 year following vaccination, 97% of participants were seropositive; however, the long-term durability of the immune response is unknown. We aimed to conduct a prospective cohort study and invited participants enrolled in the previous evaluation to return 5 years after vaccination to assess durability of the immune response. METHODS: Participants returned to one of six health facilities in Kinshasa in 2021, where study staff collected a brief medical history and blood specimen. We assessed neutralising antibody titres against yellow fever virus using a plaque reduction neutralisation test with a 50% cutoff (PRNT50). Participants with a PRNT50 titre of 10 or higher were considered seropositive. The primary outcome was the proportion of participants seropositive at 5 years. FINDINGS: Among the 764 participants enrolled, 566 (74%) completed the 5-year visit. 5 years after vaccination, 539 (95·2%, 95% CI 93·2-96·7) participants were seropositive, including 361 (94·3%, 91·5-96·2) of 383 who were seronegative and 178 (97·3%, 93·8-98·8) of 183 who were seropositive at baseline. Geometric mean titres (GMTs) differed significantly across age groups for those who were initially seronegative with the lowest GMT among those aged 2-5 years and highest among those aged 13 years and older. INTERPRETATION: A fractional dose of the 17DD yellow fever vaccine induced an immunologic response with detectable titres at 5 years among the majority of participants in the Democratic Republic of the Congo. These findings support the use of fractional-dose vaccination for outbreak prevention with the potential for sustained immunity. FUNDING: Gavi, the Vaccine Alliance through the CDC Foundation. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.

Analysis and Bayesian estimation of a model for Chikungunya dynamics with relapse: An outbreak in Acapulco, Mexico.

Chikungunya is a vector-borne viral disease transmitted by Aedes aegypti and Aedes albopictus mosquitoes. It does not have any specific treatment, and there is no vaccine. Recent epidemiological data have indicated that a relapse of the infection can occur within three months of the initial infection; however, until now, mathematical models for the spread of the disease have not considered this factor. We propose a mathematical model for the transmission of the Chikungunya virus that considers relapse. We calculated the basic reproductive number $ (R_0) $ of the disease by using the next-generation operator method. We proved the existence of a forward bifurcation. We determined the existence and the global stability of the equilibrium points by using the Lyapunov function method. We fitted the model to data from an outbreak in 2015 in Acapulco, Mexico to estimate the model parameters and $ R_0 $ with the Bayesian approach via a Hamiltonian Monte Carlo method. In the local sensitivity analysis, we found that the fraction of infected individuals who become asymptomatic has a strong impact on the basic reproductive number and makes some control measures insufficient. The impact of the fraction of infected individuals who become asymptomatic should be considered in Chikungunya control strategies.

Fractional Dosing of Yellow Fever Live Attenuated 17D Vaccine: A Perspective.

Yellow fever virus (YFV) is a mosquito-borne flavivirus that causes over 109,000 severe infections and over 51,000 deaths annually in endemic areas of sub-Saharan Africa and tropical South America. The virus has a transmission cycle involving mosquitoes and humans or non-human primates (NHPs) as the vertebrate hosts. Although yellow fever (YF) is prevented by a live attenuated vaccine (strain 17D), recent epidemics in Angola, the Democratic Republic of the Congo (DRC), and Brazil put great pressure on vaccine stockpiles. This resulted in the World Health Organization (WHO) and Pan American Health Organization (PAHO) implementing, on an emergency basis only, off-label dose-sparing techniques and policies during 2016-2018 to protect as many people in DRC and Brazil as possible from disease during unexpected large outbreaks of YF. Subsequently non-inferiority studies involving full doses compared to fractional doses indicated promising results, leading some policy-makers and scientists to consider utilizing YF vaccine fractional doses in non-emergency scenarios. Although the additional data on the immunogenicity and safety of fractional doses are promising, there are several questions and considerations that remain regarding the use of fractional doses, including differences in the initial antibody kinetics, differences in the immune response in certain populations, and durability of the immune response to fractional doses compared to full doses. Until the remaining knowledge gaps are addressed, full doses instead of fractional doses should continue to be used unless there are insufficient doses of the vaccine available to control outbreaks of YF.

Immunogenicity and safety of fractional doses of 17D-213 yellow fever vaccine in HIV-infected people in Kenya (YEFE): a randomised, double-blind, non-inferiority substudy of a phase 4 trial.

BACKGROUND: Evidence indicates that fractional doses of yellow fever vaccine are safe and sufficiently immunogenic for use during yellow fever outbreaks. However, there are no data on the generalisability of this observation to populations living with HIV. Therefore, we aimed to evaluate the immunogenicity of fractional and standard doses of yellow fever vaccine in HIV-positive adults. METHODS: We conducted a randomised, double-blind, non-inferiority substudy in Kilifi, coastal Kenya to compare the immunogenicity and safety of a fractional dose (one-fifth of the standard dose) versus the standard dose of 17D-213 yellow fever vaccine among HIV-positive volunteers. HIV-positive participants aged 18-59 years, with baseline CD4+ T-cell count of at least 200 cells per mL, and who were not pregnant, had no previous history of yellow fever vaccination or infection, and had no contraindication for yellow fever vaccination were recruited from the community. Participants were randomly assigned 1:1 in blocks (variable block sizes) to either a fractional dose or a standard dose of the 17D-213 yellow fever vaccine. Vaccines were administered subcutaneously by an unblinded nurse and pharmacist; all other study personnel were blinded to the vaccine allocation. The primary outcome of the study was the proportion of participants who seroconverted by the plaque reduction neutralisation test (PRNT50) 28 days after vaccination for the fractional dose versus the standard dose in the per-protocol population. Secondary outcomes were assessment of adverse events and immunogenicity during the 1-year follow-up period. Participants were considered to have seroconverted if the post-vaccination antibody titre was at least 4 times greater than the pre-vaccination titre. We set a non-inferiority margin of not less than a 17% decrease in seroconversion in the fractional dose compared with the standard dose. This study is registered with ClinicalTrials.gov, NCT02991495. FINDINGS: Between Jan 29, 2019, and May 17, 2019, 303 participants were screened, and 250 participants were included and vaccinated; 126 participants were assigned to the fractional dose and 124 to the standard dose. 28 days after vaccination, 112 (96%, 95% CI 90-99) of 117 participants in the fractional dose group and 115 (98%, 94-100) of 117 in the standard dose group seroconverted by PRNT50. The difference in seroconversion between the fractional dose and the standard dose was -3% (95% CI -7 to 2). Fractional dosing therefore met the non-inferiority criterion, and non-inferiority was maintained for 1 year. The most common adverse events were headache (n=31 [12%]), fatigue (n=23 [9%]), myalgia (n=23 [9%]), and cough (n=14 [6%]). Reported adverse events were either mild (182 [97%] of 187 adverse events) or moderate (5 [3%]) and were self-limiting. INTERPRETATION: Fractional doses of the 17D-213 yellow fever vaccine were sufficiently immunogenic and safe demonstrating non-inferiority to the standard vaccine dose in HIV-infected individuals with CD4+ T cell counts of at least 200 cells per mL. These results provide confidence that fractional dose recommendations are applicable to populations with high HIV prevalence. FUNDING: Wellcome Trust, Médecins Sans Frontières Foundation, and the UK Department for International Development.

Immunogenicity and safety of fractional doses of 17D-213 yellow fever vaccine in children (YEFE): a randomised, double-blind, non-inferiority substudy of a phase 4 trial.

BACKGROUND: Current supply shortages constrain yellow fever vaccination activities, particularly outbreak response. Although fractional doses of all WHO-prequalified yellow fever vaccines have been shown to be safe and immunogenic in a randomised controlled trial in adults, they have not been evaluated in a randomised controlled trial in young children (9-59 months old). We aimed to assess the immunogenicity and safety of fractional doses compared with standard doses of the WHO-prequalified 17D-213 vaccine in young children. METHODS: This substudy of the YEFE phase 4 study was conducted at the Epicentre Mbarara Research Centre (Mbarara, Uganda). Eligible children were aged 9-59 months without contraindications for vaccination, without history of previous yellow fever vaccination or infection and not requiring yellow fever vaccination for travelling. Participants were randomly assigned, using block randomisation, 1:1 to standard or fractional (one-fifth) dose of yellow fever vaccine. Investigators, participants, and laboratory personnel were blinded to group allocation. Participants were followed for immunogenicity and safety at 10 days, 28 days, and 1 year after vaccination. The primary outcome was non-inferiority in seroconversion (-10 percentage point margin) 28 days after vaccination measured by 50% plaque reduction neutralisation test (PRNT50) in the per-protocol population. Safety and seroconversion at 10 days and 12-16 months after vaccination (given COVID-19 resctrictions) were secondary outcomes. This study is registered with ClinicalTrials.gov, NCT02991495. FINDINGS: Between Feb 20, 2019, and Sept 9, 2019, 433 children were assessed, and 420 were randomly assigned to fractional dose (n=210) and to standard dose (n=210) 17D-213 vaccination. 28 days after vaccination, 202 (97%, 95% CI 95-99) of 207 participants in the fractional dose group and 191 (100%, 98-100) of 191 in the standard dose group seroconverted. The absolute difference in seroconversion between the study groups in the per-protocol population was -2 percentage points (95% CI -5 to 1). 154 (73%) of 210 participants in the fractional dose group and 168 (80%) of 210 in the standard dose group reported at least one adverse event 28 days after vaccination. At 10 days follow-up, seroconversion was lower in the fractional dose group than in the standard dose group. The most common adverse events were upper respiratory tract infections (n=221 [53%]), diarrhoea (n=68 [16%]), rhinorrhoea (n=49 [12%]), and conjunctivitis (n=28 [7%]). No difference was observed in incidence of adverse events and serious adverse events between study groups. CONCLUSIONS: Fractional doses of the 17D-213 vaccine were non-inferior to standard doses in inducing seroconversion 28 days after vaccination in children aged 9-59 months when assessed with PRNT50, but we found fewer children seroconverted at 10 days. The results support consideration of the use of fractional dose of yellow fever vaccines in WHO recommendations for outbreak response in the event of a yellow fever vaccine shortage to include children. FUNDING: Médecins Sans Frontières Foundation.

Characterization of "off-target" immune modulation induced by live attenuated yellow fever vaccine.

BACKGROUND: Live attenuated (LA) vaccines alter immune functions and are associated with beneficial outcomes. We previously demonstrated that yellow fever virus vaccine (LA-YF-Vax) dampens T cell receptor (TCR) signaling in vitro via an RNA-based mechanism. We examined subjects before and after LA-YF-Vax to assess TCR-mediated functions in vivo. METHODS: Sera and peripheral blood mononuclear cells (PBMCs) were obtained before and after LA-YF-Vax (+/-additional vaccines) or quadrivalent influenza vaccine (QIV). TCR-mediated activation was determined by IL-2 release or phosphorylation of the lymphocyte-specific-Src-kinase. TCR-regulating phosphatase (PTPRE) expression was also measured. RESULTS: Compared to pre-vaccination, LA-YF-Vax recipient PBMCs demonstrated transient reduction in IL-2 release following TCR-stimulation and PTPRE levels, unlike QIV control subjects. YFV was detected in (8/14) following LA-YF-Vax. Following incubation of healthy donor PBMCs in serum-derived extracellular vesicles (EVs) prepared from LA-YF-Vax recipients, TCR signaling and PTPRE levels were reduced post-vaccination, even in subjects without detectable YFV RNA. CONCLUSIONS: LA-YF-Vax reduces TCR functions and PTPRE levels following vaccination. EVs from serum recapitulated this effect in healthy cells. This likely contributes to the reduced immunogenicity for heterologous vaccines following LA-YF-Vax administration. Identification of specific immune mechanisms related to vaccines should contribute to understanding of the "off target", beneficial effects of live vaccines.

Characterization of Live-Attenuated Powassan Virus Vaccine Candidates Identifies an Efficacious Prime-Boost Strategy for Mitigating Powassan Virus Disease in a Murine Model.

Powassan virus (POWV) is an emerging tick-borne virus and cause of lethal encephalitis in humans. The lack of treatment or prevention strategies for POWV disease underscores the need for an effective POWV vaccine. Here, we took two independent approaches to develop vaccine candidates. First, we recoded the POWV genome to increase the dinucleotide frequencies of CpG and UpA to potentially attenuate the virus by raising its susceptibility to host innate immune factors, such as the zinc-finger antiviral protein (ZAP). Secondly, we took advantage of the live-attenuated yellow fever virus vaccine 17D strain (YFV-17D) as a vector to express the structural genes pre-membrane (prM) and envelope (E) of POWV. The chimeric YFV-17D-POWV vaccine candidate was further attenuated for in vivo application by removing an N-linked glycosylation site within the nonstructural protein (NS)1 of YFV-17D. This live-attenuated chimeric vaccine candidate significantly protected mice from POWV disease, conferring a 70% survival rate after lethal challenge when administered in a homologous two-dose regimen. Importantly, when given in a heterologous prime-boost vaccination scheme, in which vaccination with the initial chimeric virus was followed by a protein boost with the envelope protein domain III (EDIII), 100% of the mice were protected without showing any signs of morbidity. Combinations of this live-attenuated chimeric YFV-17D-POWV vaccine candidate with an EDIII protein boost warrant further studies for the development of an effective vaccine strategy for the prevention of POWV disease.

Yellow Fever Vaccine-Associated Viscerotropic Disease among Siblings, São Paulo State, Brazil.

We describe 5 cases of yellow fever vaccine-associated viscerotropic disease (YEL-AVD) in 2 familial clusters during the 2017-2018 yellow fever (YF) vaccination campaign in São Paulo state, Brazil. The first case was that of a 40-year-old white man who died of icterohemorrhagic syndrome, which was confirmed to be YEL-AVD by using real-time reverse transcription PCR to detect 17DD YF vaccine in the liver. Ten years previously, his brother died of a clinically similar disease without a confirmed diagnosis 9 days after YF vaccination. The second cluster included 3 of 9 siblings in whom hepatitis developed in the first week after receiving fractionated doses of YF vaccine. Two of them died of hemorrhagic diathesis and renal and respiratory failure, and 17DD-YF vaccine was detected in serum samples from all patients and in the liver in 1 case. Genetic factors might play a substantial role in the incidence of YEL-AVD.

Factors associated with yellow fever vaccine failure: A systematic literature review.

INTRODUCTION: Considering that vaccination with yellow fever vaccine (YFV) is the most important method to prevent and control yellow fever (YF), this study synthesized evidence on factors associated with YFV failure. METHODS: A systematic review (SR) was performed in the PubMed, Cochrane CENTRAL, Embase, and LILACS databases up to November 2019. Observational and experimental analytical epidemiological studies that analyzed the failure of YFV were included. This review followed the guidelines of the Preferred Reporting Items for Systematic Reviews and meta-Analyses. RESULTS: A total of 1,466 articles were identified after searching the databases of which 46 were included in the qualitative analysis after applying the elegibility criteria. Our findings indicated that YFV confers protective immunity in different age groups; when produced by different producers; when administered simultaneously with a range of other vaccines; when used as fractional doses and when used with prophylactic and immunosuppressive therapies. It failed to produce a protective response in some pregnant women, children under two years of age, children with Kwashiorkor and when long periods of time have passed after vaccination. For individuals with human immunodeficiency virus (HIV), the results were divergent. CONCLUSIONS: The results of this SR revealed the factors associated with the failure of the YFV, and the results can support recommendations on vaccination policies, support the safety of health professionals who work directly with immunization in the implementation of the vaccination schedule, in addition to guiding future research and enhance the credibility of YFV in the prevention of a serious disease such as YF.

Evaluation of safety and immuno-efficacy of a next generation live-attenuated yellow fever vaccine in cynomolgus macaques.

The increased demand for yellow fever (YF) vaccines over the last decade, along with insufficient availability of specific pathogen-free embryonated eggs required for timely vaccine production, has led to global YF vaccine shortages. A new live-attenuated YF vaccine candidate (generically referred to as vYF) cloned from a YF-VAX® vaccine (YF-17D vaccine) substrain adapted for growth in Vero cells cultured in serum-free media is currently in development. Here, we assessed the safety and immunogenicity of vYF, and its protective activity upon virulent challenge with wild-type yellow fever virus (YFV) Asibi, compared to licensed YF-17D vaccines in the translational cynomolgus macaque model. vYF was well tolerated with no major safety concerns. Vaccine-related safety observations were limited to minimal/minor microscopic findings at the injection sites and in the draining lymph nodes, consistent with expected stimulation of the immune system. vYF induced early differential expression of genes involved in antiviral innate immunity previously described in humans vaccinated with YF-17D vaccines, as well as YFV-specific IgM and IgG antibodies, high and sustained YFV neutralizing antibody titers from Day 14 up to at least Day 258 post-immunization, IgM+ and IgG+ memory B cells from Day 14 up to at least Day 221 post-vaccination, and Th1 interferon (IFN)-γ and interleukin (IL)-2 secreting effector and memory T cells. Additionally, vYF provided effective resistance to virulent challenge with wild-type YFV Asibi including complete protection against YFV-induced mortality, pathology, dysregulation of blood and liver soluble biomarkers, and a significant reduction in viremia and viral load to the limit of detection. These NHP data suggest that vYF would provide protection against YFV infection in practice, at least similar to that achieved with currently marketed YF-17D vaccines.

Neurovirulence, viscerotropism and immunogenicity of live attenuated yellow fever 17D vaccine virus in non-human primates.

Yellow fever vaccine associated neurovirulence and viscerotropism have been reported by various countries. In this study, the neurovirulence, viscerotropism and immunogenicity of yellow fever vaccine seed lots (master and working) and final product manufactured at Serum Institute of India (SII) were evaluated in cynomolgus monkeys. WHO reference virus 168-73 and Stamaril™ as a control vaccine was used for comparison. Neurovirulence and viscerotropism scores of the seed lots and final product were lower than Stamaril™. The SII seed virus and vaccine complies to the WHO requirement for neurovirulence, viscerotropism and immunogenicity, when tested in comparison to WHO reference seed virus 168/73. All challenged animals showed 100 % seroconversion as early as day 14 and neutralizing antibody titers were sustainable at day 30 in all animals.

Application of new generation high-throughput RNA sequencing in quality control of live attenuated yellow fever vaccine(chicken embryo cell) virus seed bank / 中国生物制品学杂志

@#Objective To perform quality control in live attenuated yellow fever vaccine(chicken embryo cell)virus seed bank at the genomic level using the new generation Illumina/Solexa sequencing platform.Methods The live attenuated yellow fever vaccine strain YF17D-204 was inoculated into primary chicken embryo cells,and the chicken embryo cell adapted strains of live attenuated yellow fever vaccine were screened to establish YFV17D-CEC tertiary virus seed bank. The genome RNA of virus seeds was extracted,and the RNA library was prepared. The new generation Illumina/Solexa sequencing platform was used for high-throughput RNA sequencing. The whole genome nucleic acid sequence of yellow fever virus was systematically analyzed by using biological softwares such as FastQC,Trimmomatic,SPAdes,GapFiller,PrInSeS-G,Prokka,RepeatMasker,CRT,NCBI Blast~+,KAAS,HMMER3,TMHMM,SignalP,LipoP,ProtCamp and MegAlign.Results The whole genome of YFV17D-CEC tertiary virus seed bank contained 10 862 nucleotides,including an open reading frame(ORF)from 119 to 10 354(10 236 bp),encoding 3 412 amino acids. Sequence alignment analysis showed that the sequence of YF17D-CEC tertiary virus seed bank was 100% identical with YFV17D RKI(JN628279.1),YF/Vaccine/USA/Sanofi-Pasteur-17D-204/UF795AA/YFVax(JX503529.1)and YFV17D-204(KF769015.1),and no mutation occurred in the whole genome of the tertiary virus seed bank. Comparison of the sequences of different live attenuated yellow fever vaccine strains showed that yellow fever virus had multiple polymorphic sites.Conclusion YFV17DCEC has good genetic stability in primary chicken embryo cells. High-throughput RNA sequencing technology can quickly detect the whole genome information of YF17D-CEC virus seed bank,and the sequence analysis data can be used in the gene level quality control of yellow fever vaccine virus seed banks.

Replication Kinetics of a Candidate Live-Attenuated Vaccine for Cache Valley Virus in Aedes albopictus.

Background: The emergence or re-emergence of several orthobunyaviruses (order: Bunyavirales; family: Peribunyaviridae), including Cache Valley virus (CVV) and Oropouche virus, warrants the development and evaluation of candidate live-attenuated vaccines (LAVs). Ideally, these vaccines would elicit long-lasting immunity with one single immunization. Materials and Methods: Since the deletion of two virulence factors, NSs and NSm, has been shown to attenuate the virulence phenotype of orthobunyaviruses, phleboviruses, and nairoviruses, genetic manipulation of the viral genome is considered an effective strategy for the rational design of candidate LAVs for bunyaviruses across multiple families. In addition, the deletion of Rift Valley fever virus NSs and NSm genes has been shown to reduce transmission by mosquitoes. Results: In this study, the ability of a CVV mutant lacking the NSs and NSm genes (2delCVV) to replicate in intrathoracically injected Aedes albopictus was compared with the parental wild-type CVV (wtCVV) 6V633 strain. In contrast to the robust replication of wtCVV in injected mosquitoes, the multiplication kinetics of the 2delCVV mutant was reduced by more than a 100-fold. Conclusion: These results suggest that the deletion of NSm and NSs genes is a feasible approach to rationally design candidate orthobunyavirus LAVs that are highly attenuated in mosquitoes and, therefore, pose little risk of reversion to virulence and transmission.

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.