Vaccine Production Research Articles

Is the African Vaccine Manufacturing Accelerator a decoupling mechanism?

This article explores how the African Vaccine Manufacturing Accelerator can support the sustainable production of vaccines in Africa. It highlights the value of the accelerator in relation to the Regional Vaccine Manufacturing Collaborative. The author proposes that this novel financing instrument should be well-designed and implemented in line with the targets of the Partnerships for African Vaccine Manufacturing. It should not be a decoupling tool to appease the institutional environment of the global vaccine market, but a sustainable demonstration of the goodwill and commitment of political and technical leaders to ensure equitable access to routine and epidemic-related vaccines in Africa.

Vaccine process technology-Adecade of progress.

In the past decade, new approaches to the discovery and development of vaccines have transformed the field. Advances during the COVID-19 pandemic allowed the production of billions of vaccine doses per year using novel platforms such as messenger RNA and viral vectors. Improvements in the analytical toolbox, equipment, and bioprocess technology have made it possible to achieve both unprecedented speed in vaccine development and scale of vaccine manufacturing. Macromolecular structure-function characterization technologies, combined with improved modeling and data analysis, enable quantitative evaluation of vaccine formulations at single-particle resolution and guided design of vaccine drug substances and drug products. These advances play a major role in precise assessment of critical quality attributes of vaccines delivered by newer platforms. Innovations in label-free and immunoassay technologies aid in the characterization of antigenic sites and the development of robust in vitro potency assays. These methods, along with molecular techniques such as next-generation sequencing, will accelerate characterization and release of vaccines delivered by all platforms. Process analytical technologies for real-time monitoring and optimization of process steps enable the implementation of quality-by-design principles and faster release of vaccine products. In the next decade, the field of vaccine discovery and development will continue to advance, bringing together new technologies, methods, and platforms to improve human health.

National Concept of Development of Vaccine Prophylaxis in Russia

The article is dedicated to outlining the conceptual directions for the development of vaccination in the Russian Federation. The provisions of the concept are formulated based on the authors' years of research on vaccination issues and analysis of data from domestic and foreign scientific literature. The main provisions of the concept aim at strengthening the state policy in the field of vaccination, reconstructing and expanding enterprises for the production of domestic vaccines, developing and improving immunobiological medicinal products against current infections, refining the National Immunization Schedule and Vaccination Schedule according to epidemiological indications; further promoting the WHO's "lifelong immunization" strategy; developing regional immunization programs; implementing a risk-oriented approach in the development of immunization programs; developing a system for monitoring post-vaccination complications; implementing epidemiological surveillance of vaccination as a methodology for assessing the strategy and tactics of immunization in accordance with the epidemiological situation; ensuring commitment to vaccination among the population, healthcare workers, and legislative and executive authorities.

Mechanistic modeling of in vitro transcription incorporating effects of magnesium pyrophosphate crystallization.

The in vitro transcription (IVT) reaction used in the production of messenger RNA vaccines and therapies remains poorly quantitatively understood. Mechanistic modeling of IVT could inform reaction design, scale-up, and control. In this work, we develop a mechanistic model of IVT to include nucleation and growth of magnesium pyrophosphate crystals and subsequent agglomeration of crystals and DNA. To help generalize this model to different constructs, a novel quantitative description is included for the rate of transcription as a function of target sequence length, DNA concentration, and T7 RNA polymerase concentration. The model explains previously unexplained trends in IVT data and quantitatively predicts the effect of adding the pyrophosphatase enzyme to the reaction system. The model is validated on additional literature data showing an ability to predict transcription rates as a function of RNA sequence length.

The health economic-industrial complex: production and innovation for universal health access, Brazil.

The coronavirus disease 2019 (COVID-19) pandemic has highlighted global disparities in accessing essential health products, demonstrating the critical need for low- and middle-income countries to develop local production and innovation capabilities. The health economic-industrial complex approach changed the values that guided innovation and industrial policies in Brazil. The approach directed health production and innovation to universal access; the health ministry led a whole-of-government approach; and public procurement was strategically applied to stimulate productive public and private investments. The institutional, technological and productive capacities built up by the health economic-industrial complex allowed the country to quickly establish local COVID-19 vaccines production and guarantee access for the population. Brazil has a universal health system that guarantees access to health for its 215 million population. Public policies and actions, based on the health economic-industrial complex, guided investment projects in line with health demands, strengthened local producers, and increased autonomy in the production of health products in areas of greater technological dependence. During the COVID-19 pandemic, the country was able to rapidly scale up local vaccine production. By August 2021, Brazil had produced 74.8% (151 463 502/202 437 516) of the vaccine doses used in the country. The Brazilian example shows that low- and middle-income countries can build systemic development policies that increase their capability to produce and innovate in concert with universal health systems. This increased capacity can guarantee access to health products and supplies that are critical during global health emergencies.

MRNA COVID-19 vaccine safety among older adults from the Canadian National Vaccine Safety Network

This study examined short-to-medium term safety of COVID-19 vaccines among adults aged ≥65 years using the Canadian National Vaccine Safety Network active safety surveillance data. Both vaccinated and unvaccinated older adult participants recruited from seven provinces and territories were included in the analysis. Safety was assessed at 7 days after COVID-19 vaccination (dose 1, 2 and 3), and 7 months after dose 1. Multivariable logistic regression was used to examine the association between BNT162b2/mRNA-1273 COVID-19 vaccines and two short-term health events: 1) health event preventing daily activities or required medical consultation, 2) serious health events resulting in an emergency department visit and/or hospitalization within 7 days following each dose. We also assessed the rates of serious health events for the period between dose 1 and 2, and 7-months following dose 1. Between December 2020 and February 2022, a total of 173,038, 104,452, and 13,970 older adults completed dose 1, dose 2, and dose 3 surveys, respectively. The control survey was completed by 2,955 unvaccinated older adults. Health events occurred more frequently among recipients after dose 2 homologous mRNA-1273 (adjusted odds ratio [95 % confidence interval]: 2.91 [2.24–3.79]) and dose two heterologous (BNT162b2 followed by mRNA-1273): 1.50 [1.12–2.02] compared to unvaccinated counterparts. There was no difference in event rates after any dose of BNT162b2 and unvaccinated participants. The rates of serious health events following COVID-19 vaccination were very low (≤0.3 %) across all vaccine products and doses, and were not higher compared to unvaccinated controls, and were not associated with an emergency department visit or hospitalization within 7 days following vaccination. Reported symptoms were self-limited and rarely required medical assessment. Our findings further strengthen the current evidence that mRNA COVID-19 vaccines are safe and can be used to inform older adults about expected adverse events following COVID-19 vaccination.

Development of Vaccine Candidates Against Mycobacterium Tuberculosis in 2019-2023

ABSTRACT With extensive use of the Bacillus Calmette–Guérin (BCG) vaccine, the global prevalence of Mycobacterium tuberculosis (MTB) remains. A number of vaccines proposed to cure and prevent tuberculosis (TB) infection are undergoing various stages of clinical trials. Although vaccine production is progressing, more attention is needed. A number of TB vaccines are currently undergoing clinical trials, most of which rely on a combination of proteins and/or adjuvants or recombinant viral vectors specific for MTB antigens. We tried to cover the range of TB vaccines in this study by analyzing their composition, the immunological responses they elicit, and the stages of clinical trials. To find out the Development Of Prospective Vaccines Against Mycobacterium Tuberculosis. This research uses a literature review, between August 2023 and November 2023, the authors of this literature review checked PubMed, Science Direct, Google Scholar, and other databases containing research findings or scientific articles. Only studies that met the above search criteria were included in the systematic review. Many recently developed tuberculosis vaccines are reportedly in the final stages of clinical trials, where they have significantly strengthened the immune system and even produced protection against the host. Immunization produced by vaccines that have successfully passed the initial stages of clinical trials is safe and effective, and can even surpass BCG in terms of immunity.  Based on the description above, it can be concluded that many recently developed tuberculosis vaccines are reported to be in the final stages of clinical trials, where they have significantly strengthened the immune system and even produced protection against the host. Immunization produced by vaccines that have successfully passed the initial stages of clinical trials is safe and effective, and can even surpass BCG in terms of immunity. With the development of new TB vaccines that strengthen the body's immunity and create effective delivery mechanisms, hopes for TB treatment and prevention are increasing. The development of vaccine effects can be facilitated, in part, through the use of effective delivery mechanisms, which have also been used in TB vaccines. Keywords: Tuberculosis, Vaccine, Bacteria, Mycobacterium Tuberculosis, BCG

An mRNA technology transfer programme and economic sustainability in health care.

The World Health Organization (WHO) set up the messenger ribonucleic acid (mRNA) technology transfer programme in June 2021 with a development hub in South Africa and 15 partner vaccine producers in middle-income countries. The goal was to support the sustainable development of and access to life-saving vaccines for people in these countries as a means to enhance epidemic preparedness and global public health. This initiative aims to build resilience and strengthen local vaccine research, and development and manufacturing capacity in different regions of the world, especially those areas that could not access coronavirus disease 2019 (COVID-19) vaccines in a timely way. This paper outlines the current global vaccine market and summarizes the findings of a case study on the mRNA technology transfer programme conducted from November 2022 to May 2023. The study was guided by the vision of the WHO Council on the Economics of Health for All to build an economy for health using its four work streams of value, finance, innovation and capacity. Based on the findings of the study, we offer a mission-oriented policy framework to support the mRNA technology transfer programme as a pilot for transformative change towards an ecosystem for health innovation for the common good. Parts of this vision have already been incorporated into the governance of the mRNA technology transfer programme, while other aspects, especially the common good approach, still need to be applied to achieve the goals of the programme.

The Significance of the 98th Amino Acid in GP2a for Porcine Reproductive and Respiratory Syndrome Virus Adaptation in Marc-145 Cells

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in the pig industry. Marc-145 cells are widely used for PRRSV isolation, vaccine production, and investigations into virus biological characteristics. Despite their significance in PRRSV research, Marc-145 cells struggle to isolate specific strains of the North American virus genotype (PRRSV-2). The involvement of viral GP2a, GP2b, and GP3 in this phenomenon has been noted. However, the vital amino acids have not yet been identified. In this study, we increased the number of blind passages and successfully isolated two strains that were previously difficult to isolate with Marc-145 cells. Both strains carried an amino acid substitution in GP2a, specifically phenylalanine to leucine at the 98th amino acid position. Through a phylogenetic and epidemiologic analysis of 32 strains, those that were not amenable to isolation widely exhibited this mutation. Then, by using the PRRSV reverse genetics system, IFA, and Western blotting, we identified the mutation that could affect the tropism of PRRSV-2 for Marc-145 cells. Furthermore, an animal experiment was conducted. Through comparisons of clinical signs, mortality rates, and viral load in the organs and sera, we found that mutation did not affect the pathogenicity of PRRSV-2. In conclusion, our study firmly establishes the 98th amino acid in GP2a as a key determinant of PRRSV-2 tropism for Marc-145 cells.

Developments and current challenges in the process of cell culture-based seasonal influenza vaccine manufacture in Japan.

Seasonal influenza is an acute respiratory infection primarily caused by influenza A and B viruses, which circulate annually and cause substantial morbidity and mortality worldwide. Annual influenza vaccination is currently the most effective measure for preventing influenza and greatly reduces the risk of disease severity and the incidence of complications and death. Annual seasonal influenza vaccines are traditionally produced in Japan and many other countries using viruses propagated in embryonated chicken eggs. However, at present, the effectiveness of the seasonal influenza vaccines has some significant limitations, partly because of egg-adaptive mutations in the antigenic sites of the influenza virus haemagglutinin, which are caused by the continued evolution of seasonal influenza viruses. To overcome the limitations of egg-based influenza vaccine production, a mammalian cell culture-based influenza vaccine production system has been developed in Japan in the past decade as an alternative to the current production method. In this review, I have summarised the progress in the development of cell-based seasonal influenza vaccines and discussed the technological challenges encountered in the development of influenza vaccines.

Chronic Immune Thrombocytopenia Purpura Following COVID-19 Vaccination (ChAdOx1 –nCov-19): A Case Report With OneYear Follow-Up

Background: Immune Thrombocytopenia Purpura (ITP) is a hematological disorder, where its primary cause is unknown. This can be triggered through any secondary underlying diseases or other environmental agents such as drugs, vaccination, natural viral infections etc. After the introduction of COVID-19 vaccines, a 4-fold increase in ITP cases was observed globally. Many of the COVID-19 vaccines such as m-RNA and viral-vector vaccines already demonstrated a cause-effect relationship between the event of ITP and immunization. Case presentation: A 54 year old diabetic patient presented to the hospital with complaints of gum bleeding and fatigue. He was diagnosed with severe ITP following COVID-19 vaccination with a platelet count of 5000 cumm. Initially his condition was considered as idiopathic and the COVID-19 vaccine exposure (13 days prior to the clinical presentation) was not suspected. Later the immunization timeline and onset of the reaction was traced by his hematologist. The patient underwent multiple platelet transfusions and was given corticosteroid therapy. The patient was followed for a period of 1 year and throughout the follow-up period the patient had fluctuating platelets count, especially after tapering steroids. Conclusion: ITP in this case is found to have a consistent causal association to COVID-19 vaccination as per the World Health Organization Causality assessment algorithm and is categorized under vaccine product related reactions. One year follow-up conducted showed that the thrombocytopenia following COVID-19 vaccine may be prolonged.

Quality control in SARS-CoV-2 RBD-Fc vaccine production using LC–MS to confirm strain selection and detect contaminations from other strains

Coronavirus disease of 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an ongoing outbreak, disrupting human life worldwide. Vaccine development was prioritized to obtain a biological substance for combating the viral pathogen and lessening disease severity. In vaccine production, biological origin and relevant materials must be carefully examined for potential contaminants in conformity with good manufacturing practice. Due to fast mutation, several SARS-CoV-2 variants and sublineages have been identified. Currently, most of COVID-19 vaccines are developed based on the protein sequence of the Wuhan wild type strain. New vaccines specific for emerging SARS-CoV-2 strains are continuously needed to tackle the incessant evolution of the virus. Therefore, in vaccine development and production, a reliable method to identify the nature of subunit vaccines is required to avoid cross-contamination. In this study, liquid chromatography-mass spectrometry using quadrupole-time of flight along with tryptic digestion was developed for distinguishing protein materials derived from different SARS-CoV-2 strains. After analyzing the recombinantly produced receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, nine characteristic peptides were identified with acceptable limits of detection. They can be used together to distinguish 14 SARS-CoV-2 strains, except Kappa and Epsilon. Plant-produced RBD-Fc protein derived from Omicron strains can be easily distinguished from the others with 4–5 unique peptides. Eventually, a peptide key was developed based on the nine peptides, offering a prompt and precise flowchart to facilitate SARS-CoV-2 strain identification in COVID-19 vaccine manufacturing.

Comprehensive evaluation of T7 promoter for enhanced yield and quality in mRNA production

The manufacturing of mRNA vaccines relies on cell-free based systems that are easily scalable and flexible compared with the traditional vaccine manufacturing processes. Typically, standard processes yield 2 to 5 g L−1 of mRNA, with recent process optimisations increasing yields to 12 g L−1. However, increasing yields can lead to an increase in the production of unwanted by-products, namely dsRNA. It is therefore imperative to reduce dsRNA to residual levels in order to avoid intensive purification steps, enabling cost-effective manufacturing processes. In this work, we exploit sequence modifications downstream of the T7 RNA polymerase promoter to increase mRNA yields whilst simultaneously minimising dsRNA. In particular, transcription performance was optimised by modifying the sequence downstream of the T7 promoter with additional AT-rich sequences. We have identified variants that were able to produce higher amounts of mRNA (up to 14 g L−1) in 45 min of reaction. These variants exhibited up to a 30% reduction in dsRNA byproduct levels compared to a wildtype T7 promoter, and have similar EGFP protein expression. The results show that optimising the non-coding regions can have an impact on mRNA production yields and quality, reducing overall manufacturing costs.

Rice yellow mottle virus is a suitable amplicon vector for an efficient production of an anti-leishmianiasis vaccine in Nicotiana benthamiana leaves

BackgroundSince the 2000’s, plants have been used as bioreactors for the transient production of molecules of interest such as vaccines. To improve protein yield, “amplicon” vectors based on plant viruses are used. These viral constructs, engineered to carry the gene of interest replicate strongly once introduced into the plant cell, allowing significant accumulation of the protein. Here, we evaluated the suitability of the monocot-infecting RNA virus Rice yellow mottle virus (RYMV) as an amplicon vector. The promastigote surface antigen (PSA) of the protozoan Leishmania was considered as a protein of interest due to its vaccine properties against canine leishmaniasis.ResultsSince P1 (ORF1) and CP (ORF3) proteins are not strictly necessary for viral replication, ORF1 was deleted and the PSA gene was substituted to ORF3 in the RYMV-based vector. We evaluated its expression in the best described plant bioreactor system, Nicotiana benthamiana which, unlike rice, allows transient transformation by Agrobacterium. Despite not being its natural host, we demonstrated a low level of RYMV-based vector replication in N. benthamiana leaves. Under optimized ratio, we showed that the P19 silencing suppressor in combination with the missing viral CP ORF significantly enhanced RYMV amplicon replication in N. benthamiana. Under these optimized CP/P19 conditions, we showed that the RYMV amplicon replicated autonomously in the infiltrated N. benthamiana cells, but was unable to move out of the infiltrated zones. Finally, we showed that when the RYMV amplicon was expressed under the optimized conditions we set up, it allowed enhanced PSA protein accumulation in N. benthamiana compared to the PSA coding sequence driven by the 35S promoter without amplicon background.ConclusionThis work demonstrates that a non-dicot-infecting virus can be used as an amplicon vector for the efficient production of proteins of interest such as PSA in N. benthamiana leaves.

Current Progress, Challenges and Prospects in the Development of COVID-19 Vaccines.

The COVID-19 pandemic has resulted in over 772 million confirmed cases, including nearly 7 million deaths, according to the World Health Organization (WHO). Leveraging rapid development, accelerated vaccine approval processes, and large-scale production of various COVID-19 vaccines using different technical platforms, the WHO declared an end to the global health emergency of COVID-19 on May 5, 2023. Current COVID-19 vaccines encompass inactivated, live attenuated, viral vector, protein subunit, nucleic acid (DNA and RNA), and virus-like particle (VLP) vaccines. However, the efficacy of these vaccines is diminishing due to the constant mutation of SARS-CoV-2 and the heightened immune evasion abilities of emerging variants. This review examines the impact of the COVID-19 pandemic, the biological characteristics of the virus, and its diverse variants. Moreover, the review underscores the effectiveness, advantages, and disadvantages of authorized COVID-19 vaccines. Additionally, it analyzes the challenges, strategies, and future prospects of developing a safe, broad-spectrum vaccine that confers sufficient and sustainable immune protection against new variants of SARS-CoV-2. These discussions not only offer insight for the development of next-generation COVID-19 vaccines but also summarize experiences for combating future emerging viruses.

Testing S. sonnei GMMA with and without Aluminium Salt-Based Adjuvants in Animal Models.

Shigellosis is one of the leading causes of diarrheal disease in low- and middle-income countries, particularly in young children, and is more often associated with antimicrobial resistance. Therefore, a preventive vaccine against shigellosis is an urgent medical need. We have proposed Generalised Modules for Membrane Antigens (GMMA) as an innovative delivery system for Shigella sonnei O-antigen, and an Alhydrogel formulation (1790GAHB) has been extensively tested in preclinical and clinical studies. Alhydrogel has been used as an adsorbent agent with the main purpose of reducing potential GMMA systemic reactogenicity. However, the immunogenicity and systemic reactogenicity of this GMMA-based vaccine formulated with or without Alhydrogel have never been compared. In this work, we investigated the potential adjuvant effect of aluminium salt-based adjuvants (Alhydrogel and AS37) on S. sonnei GMMA immunogenicity in mice and rabbits, and we found that S. sonnei GMMA alone resulted to be strongly immunogenic. The addition of neither Alhydrogel nor AS37 improved the magnitude or the functionality of vaccine-elicited antibodies. Interestingly, rabbits injected with either S. sonnei GMMA adsorbed on Alhydrogel or S. sonnei GMMA alone showed a limited and transient body temperature increase, returning to baseline values within 24 h after each vaccination. Overall, immunisation with unadsorbed GMMA did not raise any concern for animal health. We believe that these data support the clinical testing of GMMA formulated without Alhydrogel, which would allow for further simplification of GMMA-based vaccine manufacturing.

Analysis of the State Archives Republican Archives Documents on Tuberculosis and Fight Against Tuberculosis in the Early Republican Period in Turkiye

Purpose: To share information obtained as a result of examination of archival documents related to tuberculosis and the fight against tuberculosis between 1923-1938. Method: Study, which is a qualitative research, was designed as a document analysis. Previous publications on subject were examined. State Archives Republican Archives Catalogue was scanned. Documents found were analysed. Selected documents were included in study. Study covers the period of Atatürk (1923-1938). Results: In early Republican period, Turkiye gave importance to fight against tuberculosis together with infectious diseases such as malaria, trachoma and syphilis. successful works initiated in Ottoman period were continued and additional works were initiated according to new practices and principles. Tuberculosis and fight against tuberculosis were discussed in "National Turkish Medical Congresses". In following period, main theme of the 11th Congress would be tuberculosis. The Ministry of Health has defined a concept for the fight against infectious diseases and implemented it. Guideline on fight against tuberculosis has started to be published. New dispensaries and sanatoriums were built. Efforts were made to increase existing bed capacity. use of BCG vaccine was introduced. New facilities were built at "Central Institute of Hygine" to start vaccine production. Participation in international exhibitions and congresses was ensured. Arrangements were made regarding the staff and salaries of doctors and nurses, and new civil servant positions were created for the fight against tuberculosis. Conclusion: It would not be wrong to say that works carried out in early Republican period were a stepping stone for the great successes to be achieved in the fight against tuberculosis in future.

Energy, exergy, environmental and exergoeconomic (4E) analysis of an ultra-low temperature cascade refrigeration system with environmental-friendly refrigerants

To ensure the efficacy of some special vaccines, the ultra-low temperature storage below −80 °C is strictly required and the classical cascade refrigeration system has a good application prospect in the production, storage, transportation and distribution of COVID-19 vaccines. Previous investigations are mainly focused on the thermodynamic performance of cascade refrigeration cycles (CRSs) to generate low temperature, and the impact of cascade refrigeration cycles on environmental and exergoeconomic aspects is few involved. In this paper, an energy-exergy-environmental-exergoeconomic (4E) analysis model was built to investigate the comprehensive performance of an ultra-low temperature cascade refrigeration system. Eight environmental-friendly refrigerant pairs, including R290-R170, R290-R1150, R717-R170, R717-R1150, R1270-R170, R1234yf-R170 and R1234yf-R1150, were chosen and the associated refrigeration performance was compared. The results show that the optimal refrigerant pair is propane-ethane (R290-R170). Compared with HFC refrigerant pair R404A-R508B CRS, R290-R170 CRS could improve the COP by 5.94%, save 5.68% power consumption, reduce 29.67% carbon dioxide emission and decrease 5% exergy economic cost. This work is significant to select environmental-friendly nature refrigerants, enrich understanding of comprehensive performance of cascade refrigeration system and enhance depth research on ultra-low temperature refrigeration.

Advances in Therapeutic Cancer Vaccines, Their Obstacles, and Prospects Toward Tumor Immunotherapy.

Over the past few decades, cancer immunotherapy has experienced a significant revolution due to the advancements in immune checkpoint inhibitors (ICIs) and adoptive cell therapies (ACTs), along with their regulatory approvals. In recent times, there has been hope in the effectiveness of cancer vaccines for therapy as they have been able to stimulate de novo T-cell reactions against tumor antigens. These tumor antigens include both tumor-associated antigen (TAA) and tumor-specific antigen (TSA). Nevertheless, the constant quest to fully achieve these abilities persists. Therefore, this review offers a broad perspective on the existing status of cancer immunizations. Cancer vaccine design has been revolutionized due to the advancements made in antigen selection, the development of antigen delivery systems, and a deeper understanding of the strategic intricacies involved in effective antigen presentation. In addition, this review addresses the present condition of clinical tests and deliberates on their approaches, with a particular emphasis on the immunogenicity specific to tumors and the evaluation of effectiveness against tumors. Nevertheless, the ongoing clinical endeavors to create cancer vaccines have failed to produce remarkable clinical results as a result of substantial obstacles, such as the suppression of the tumor immune microenvironment, the identification of suitable candidates, the assessment of immune responses, and the acceleration of vaccine production. Hence, there are possibilities for the industry to overcome challenges and enhance patient results in the coming years. This can be achieved by recognizing the intricate nature of clinical issues and continuously working toward surpassing existing limitations.

Thermostability study of virulent Newcastle disease viruses isolated in Southern Angola.

Newcastle disease (ND) is endemic in Angola. Several outbreaks of ND occurred in small backyard flocks and village chickens with high mortality in the southern provinces of the country, Cunene, Namibe and Huíla, in 2016 and 2018. In those years, 15 virulent ND virus (NDV) strains were isolated and grouped within subgenotype 2 of genotype VII (subgenotype VII.2). We now present a study on the thermostability of the isolates, aiming at the selection of the most thermostable strains that, after being genetically modified to reduce their virulence, can be adapted to the production of vaccines less dependent on cold chain and more adequate to protect native chickens against ND. Heat-inactivation kinetics of haemagglutinin (Ha) activity and infectivity (I) of the isolates were determined by incubating aliquots of virus at 56 °C for different time intervals. The two isolates from Namibe province showed a decrease in infectivity of 2 log10in ≤ 10 min, therefore belonging to the I-phenotype, but while the NB1 isolate from 2016 maintained the Ha activity up to 30 min and was classified as thermostable virus (I-Ha+), the Ha activity of the 2018 NB2 isolate decreased by 2 log2in 30 min, being classified as a thermolabile virus (I-Ha-). Of the 13 NDV isolates from Huíla province, 10 isolates were classified as thermostable, eight with phenotype I+Ha+and 2 with phenotype I-Ha+. The other three isolates from this province were classified as thermolabile viruses (I-Ha-).Contribution:This study will contribute to the control and/or eradication of Newcastle disease virus in Angola. The thermostable viral strains isolated from chickens in the country can be genetically manipulated by reverse genetic technology in order to reduce their virulence and use them as a vaccine in the remote areas of Angola.