A Cytotoxicity Assay as an Alternative to the Murine Model for the Potency Testing of Bothrops jararaca Venom and Antivenom: An Intralaboratory Pre-validation Study.

Antivenom therapy is the only specific treatment for snakebite envenomation, and antivenom potency determination is key in the efficacy assurance quality control process. Nowadays, this process relies on the in vivo murine model - thus, the development of alternative in vitro methods is imperative. In the current study, the principle of the proposed method is the ability of Bothrops venom to induce cytotoxic effects in Vero cells, and the capacity to evaluate the inhibition of this cytotoxicity by the respective antivenom. After exposure to the venom/antivenom, the relative proportions of adherent (viable) cells were evaluated by direct staining with Coomassie Blue. The optical density (OD) of the lysed cell eluate was directly proportional to the number of adherent cells. This cytotoxicity-based alternative method could represent a potential candidate for validation as a replacement for the current in vivo test. The in vitro-determined cytotoxicity of the Brazilian Bothrops reference venom (expressed as the 50% effective concentration; EC50) was 3.61 µg/ml; the in vitro-determined 50% inhibitory concentration (IC50) of the Brazilian Bothrops reference antivenom was 0.133 µl/ml. From these two values, it was possible to calculate the potency of the reference antivenom. The results from the assays exhibited a good linear response, indicating that the method could be a potential candidate replacement method for use in antivenom quality control prior to lot release, subject to further validation.

Métodos alternativos para determinação da potência de veneno e antiveneno botrópico: aplicações e perspectivas para o controle da qualidade / Alternative methods for potency evaluation for Bothrops venom and antivenom: applications and perspectives for quality control

Introdução: Acidentes com animais peçonhentos são classificados como doenças tropicais negligenciadas e são atualmente a mais frequente causa de intoxicação em humanos no Brasil. O único tratamento disponível é a rápida administração de antivenenos específicos e de qualidade garantida. Para assegurar a eficácia e a segurança desses produtos, são realizados ensaios de determinação da potência in vivo para veneno e antiveneno, desde as etapas de produção até sua liberação final. Apesar dos diversos estudos sobre métodos   alternativos ao ensaio murino, nenhum método foi efetivamente validado. Objetivo: Compilar os métodos alternativos desenvolvidos para os antivenenos botrópicos, avaliando sua disponibilidade, perspectivas e aplicações em laboratórios de produção e controle da qualidade. Método: Foi realizada uma busca nas bases PubMed, BVS e Scopus entre novembro de 2021 e junho de 2022. Foram identificados 89 trabalhos, dos quais 31 foram selecionados de acordo com os critérios de elegibilidade. Resultados: Nos métodos alternativos identificados, observamos a preferência de 42,80% dos estudos por metodologias que utilizem linhagens celulares como método alternativo aos ensaios murinos, sendo que a maioria destes trabalhos 58,30% optou pela linhagem celular Vero. Conclusões: Pela diversidade das toxinas encontradas em cada gênero de serpentes, entende-se que é de extrema importância que o ensaio de potência dos antivenenos tenha como base a avaliação e a quantificação precisa da inibição da atividade biológica dos venenos. Ensaios de citotoxicidade são amplamente utilizados e têm acumulado evidências de sua adequação como importante ferramenta alternativa ao ensaio murino para o controle da qualidade de veneno e antiveneno antibotrópico.

Introduction: Accidents with venomous animals are classified as neglected tropical diseases and are currently the most frequent cause of intoxication in humans in Brazil. The only available treatment is the rapid administration of specific, quality-assured antivenoms. To ensure the efficacy and safety of these products, in vivo potency determination tests for venom and antivenom are performed during the production stages, until final release. Despite several studies on alternative methods to the murine assay, no method has been effectively validated. Objective: To compile alternative methods developed for Bothrops antivenoms, assessing the availability of the methods and the prospects and applications in Bothrops venom and antivenom production and quality control laboratories. Method: A search was conducted in PubMed, BVS, and Scopus databases between November 2021 and June 2022. 89 articles were identified, of which 31 were selected according to the eligibility criteria. Results: We observed in the alternative methods identified a preference of 42.80% of the studies for methodologies that use cell lines as an alternative method to the murine assays, and most of these works (58.30%) opted for a VERO cell line. Conclusions: Due to the diversity of toxins found in each genus of snakes, it is understood that the potency assay for antivenoms should be based on the evaluation and precise quantification of the inhibition of biological activity of venoms. Cytotoxicity assays are widely used and have been accumulating evidence of their suitability as an important alternative tool to the murine assay for quality control for Bothrops venom and antivenom.

Potency evaluation of rabies vaccine for human use: The impact of reducing the number of animals per dilution - Part 2.

The most critical parameter for the quality control of the rabies vaccine is potency, which is evaluated by challenge test in mice while using a large animal number. Because the 3Rs concept is applied worldwide, it becomes necessary to develop alternative methods to demonstrate the production consistency of these vaccines and reduce the number of animals used for performing assays. Hence, the present study evaluated the impacts of reducing the number of mice used in the NIH test for such vaccines. A retrospective data analysis compared vaccines tested in the standard test with the results of the reduced test using only the first cages of each dilution and considering the second cages as their replicates. The relevance of the reduced assay was evaluated using Bland- Altman plot and CCC. Reliability was assessed by CV% and confidence intervals, while the impact of the reduced mouse number was evaluated by the analysis of the confidence interval of potency results and regression, linearity and parallelism parameters. The results demonstrated the feasibility of reducing to eight mice per dilution in routine assays, with complete statistical validation of the resulting potency, allowing the number of animals used for the test vaccines to be reduced by 50%.

Verification of the rabies virus glycoprotein lower limit of immunogenicity by serological assay.

Rabies lethality is close to 100% and annually 15 million people receive post-exposure prophylaxis. Testing for vaccines against this zoonosis should ensure its quality. A standardized test by the National Institutes of Health (NIH) test, based on mice immunization and challenge, has been used to determine the potency of vaccine lots. It has several disadvantages, the main one being its significant variability. Several in vitro methods like an Enzyme-linked immunosorbent assay (ELISA) have been proposed based on the quality and quantity of glycoprotein (Glptn) of rabies virus, but may also present limitations such as low sensitivity, instability and imprecision. The estimate of immunogenicity based on neutralizing antibody titer (Nab) evaluated by a serological test (ST) such as the Modified Rapid Fluorescent Focus Inhibition Test (mRFFIT), is not yet efectively applied for human vaccine. Nevertheless, a Nab concentration can be used as a predictor of clinical efficacy of this product in vaccinated humans, so, that can be applied in estimating the vaccine potency. The aim of this study was to verify the lower limit of immunogenicity of the viral Glptn content in mice using mRFFIT. The lower Glptn content by ELISA able to induce Nab response was determined. The results were correlated and demonstrated that ST was able to determine the Glptn immunogenicity lower limit. Our findings suggest that a test based on rabies Nabs may represent an additional alternative for the evaluation of rabies vaccines.

Development and pre-validation of a quantitative multi-dose serological assay for potency testing of inactivated rabies vaccines for human use.

It is mandatory to ensure the quality of biological products used in the prevention of rabies, a zoonosis with nearly 100% lethality. Fifteen million people receive post-exposure prophylaxis yearly. The vaccine batches are assessed by the National Institutes of Health (NIH) test which has several disadvantages such as significant variability and animal welfare issues. The estimation of immunogenicity based on titration of neutralizing antibodies (NA) is not applied to the human vaccine yet. Despite this, a satisfactory concentration of NA (0.5 IU/ml) can be used as a predictor of the clinical efficacy and for estimating rabies vaccine potency. The objective of this study was to develop and pre-validate a Serological Potency Test (SPT) using the modified Rapid Fluorescent Focus Inhibition Test (mRFFIT) to determine the potency of rabies vaccines for human use, demonstrating its relevance and reliability. The results show good agreement between the potencies determined by the SPT and the NIH test. The assay was able to distinguish between potent and sub-potent lots of vaccines. The results demonstrated that SPT is a viable candidate for validation and inclusion in pharmacopeias as a reduction and refinement for the NIH test.

Interlaboratory study for the establishment of Brazilian Bothrops Reference Venom and Antivenom for potency evaluation of Bothrops antivenom.

A collaborative study was performed for the establishment of the 5th lot of Brazilian Bothrops Reference Venom and the 1st lot of Brazilian Bothrops Reference Antivenom. All Brazilian manufacturers of Antibothrops Immunoglobulins and the National Control Laboratory participated of the study. The declared potency of the 5th lot of the Bothrops Reference Venom is 40.29 µg/0.5 ml, and the potency of the 1st lot of Bothrops Reference Antivenom is 6.51 mg/ml. For the potency evaluation of Bothrops Reference Venom the inter assay precision (gCV) was 3.25% in lab 01; 3.51% in INCQS; 4.71% in lab 03 and 25.11% in lab 02, and the inter laboratory precision was 13.76%. The intra assay precision of Bothrops Reference Antivenom determinations was 4.38% in INCQS; 8.47% in lab 02; 10.51% in lab 03 and 20.05% in lab 01. The inter assay precision was 3.51% in INCQS; 9.65% in lab 02; 18.03% in lab 01 and 20.23% in lab 03. The inter laboratory precision was 15.85%. Despite the high number of invalid results (55.6% for the pharmacopoeial method and 69.4% for the proposed method) the parallel line assay, have better inter laboratorial precision (gCV = 16.62%) than the pharmacopoeial potency assay (gCV = 38.28%).

International Harmonization and Cooperation in the Validation of Alternative Methods.

The development and validation of scientific alternatives to animal testing is important not only from an ethical perspective (implementation of 3Rs), but also to improve safety assessment decision making with the use of mechanistic information of higher relevance to humans. To be effective in these efforts, it is however imperative that validation centres, industry, regulatory bodies, academia and other interested parties ensure a strong international cooperation, cross-sector collaboration and intense communication in the design, execution, and peer review of validation studies. Such an approach is critical to achieve harmonized and more transparent approaches to method validation, peer-review and recommendation, which will ultimately expedite the international acceptance of valid alternative methods or strategies by regulatory authorities and their implementation and use by stakeholders. It also allows achieving greater efficiency and effectiveness by avoiding duplication of effort and leveraging limited resources. In view of achieving these goals, the International Cooperation on Alternative Test Methods (ICATM) was established in 2009 by validation centres from Europe, USA, Canada and Japan. ICATM was later joined by Korea in 2011 and currently also counts with Brazil and China as observers. This chapter describes the existing differences across world regions and major efforts carried out for achieving consistent international cooperation and harmonization in the validation and adoption of alternative approaches to animal testing.

Brazilian Center for the Validation of Alternative Methods (BraCVAM) and the process of validation in Brazil.

The need for the creation of a Brazilian centre for the validation of alternative methods was recognised in 2008, and members of academia, industry and existing international validation centres immediately engaged with the idea. In 2012, co-operation between the Oswaldo Cruz Foundation (FIOCRUZ) and the Brazilian Health Surveillance Agency (ANVISA) instigated the establishment of the Brazilian Center for the Validation of Alternative Methods (BraCVAM), which was officially launched in 2013. The Brazilian validation process follows OECD Guidance Document No. 34, where BraCVAM functions as the focal point to identify and/or receive requests from parties interested in submitting tests for validation. BraCVAM then informs the Brazilian National Network on Alternative Methods (RENaMA) of promising assays, which helps with prioritisation and contributes to the validation studies of selected assays. A Validation Management Group supervises the validation study, and the results obtained are peer-reviewed by an ad hoc Scientific Review Committee, organised under the auspices of BraCVAM. Based on the peer-review outcome, BraCVAM will prepare recommendations on the validated test method, which will be sent to the National Council for the Control of Animal Experimentation (CONCEA). CONCEA is in charge of the regulatory adoption of all validated test methods in Brazil, following an open public consultation.

Avaliação da concordância entre as linhagens de camundongos Swiss Webster e B6D2F1 no teste de potência da Eritropoietina Humana Recombinante (rhEPO): a experiência do Laboratório Nacional de Controle / Evaluation of the agreement between Swiss Webster and B6D2F1 mice lineages in the potency test of Recombinant Human Erythropoietin (rhEPO): the Brazilian National Control Laboratory experience

A eritropoietina humana recombinante (rhEPO) é um hormônio glicoproteico. Diante da gama de produtos contendo rhEPO disponíveis no mercado, da abrangência da indicação terapêutica e das características dos usuários de rhEPO, o ensaio de atividade biológica é de grande importância para o processo de liberação de lotes deste produto. O teste de potência é uma avaliação laboratorial para averiguar a eficácia do produto final, recomendada pela Farmacopeia Europeia (Ph. Eur.). Este trabalho teve como objetivo avaliar a concordância entre os valores de potência biológica obtidos quando a linhagem de camundongos preconizada pela Ph. Eur. (B6D2F1) foi utilizada em comparação com a Swiss Webster (SW). Vinte e dois lotes foram testados usando-se estas duas linhagens, e 44 ensaios válidos foram obtidos com resultados satisfatórios. Em nenhuma das análises houve necessidade de efetuar repetição de ensaios, bem como a combinação de resultados. A variação entre linhagens e a veracidade foram avaliadas, obtendo-se os seguintes resultados: Coeficiente de Variação (CV) < 10 %; Erro Relativo % (ER %) < 10 %, respectivamente. As linhagens testadas geraram resultados homogêneos sem diferença estatisticamente significativa entre elas. A linhagem SW mostrou características adequadas para ser empregada como alternativa à linhagem B6D2F1 na avaliação da potência biológica de rhEPO...

Validação de ensaio imunoenzimático utilizando-se o Conceito do Erro Total, os Perfis de Exatidão e o Índice de Exatidão como alternativa à abordagem clássica do ICH / Validation of an enzyme-linked immunosorbent assay by using the Total Error Concept, the Accuracy Profiles and the Accuracy Index as alternatives to the traditional ICH approach

O uso do conceito do Erro Total em validação de métodos analíticos é uma abordagem que incorpora a soma da veracidade e precisão. Este método utiliza ainda Perfis de Exatidão baseados em intervalos de tolerância para decidir se um modelo de calibração dará resultados de qualidade, e realiza o controle do risco de aceitar uma metodologia imprópria. Foram aplicados o Conceito do Erro Total, os perfis de Exatidão e o Índice de Exatidão na validação de um ensaio imunoenzimático (ELISA) para determinar o teor residual de ovoalbumina em vacinas. Este estudo testou uma amostra pura e fortificada com três diferentes concentrações (baixa, média e alta). A abordagem foi usada também para avaliar o método de cálculos que renderia resultados mais exatos. Os resultados obtidos no intervalo de concentrações testado com o modelo de cálculos escolhido foram: veracidade - ER % de 1,61 % a 12,15 %; precisão intermediária - CV% de 6,91 % a 9,31 % e o Erro Total de 9,83 % a 19,07 %, obtendo-se dados em conformidade com os guias internacionais. O estudo demonstrou que o método empregado é confiável para avaliar o teor de ovoalbumina, e que a abordagem do Conceito do Erro Total apresenta aplicabilidade na validação de ensaios imunoenzimáticos...

Assessment of pyrogenic response of lipoteichoic acid by the monocyte activation test and the rabbit pyrogen test.

Lipoteichoic acid (LTA) is a non-endotoxin pyrogen of a great importance in the pathogenesis of sepsis. The Rabbit Pyrogen Test (RPT) is able to detect all types of pyrogens but involves the use of animals. The Bacterial Endotoxin Test (BET) cannot fully replace the RPT because it only detects endotoxins. The Monocyte Activation Test (MAT) is sensitive to all types of pyrogens and it is based on the same biological mechanism that is responsible for the fever reaction in humans. Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) has recommended its use for other pyrogens than endotoxin because its equivalence to RPT can be demonstrated. The aim of this study was to evaluate the pyrogenic responses of the RPT and MAT that was induced by LTA. Different LTA concentrations were assayed by the MAT in parallel to the RPT. The results showed that the MAT was more sensitive than the RPT, demonstrating that the MAT detected LTA. This result may contribute to the acceptance of this test by the Brazilian regulatory agencies as a replacement for the animals used in the RPT.

Participation of Brazil in the World Congresses on Alternatives and Animal Use in the Life Sciences: an increase in commitment to the Three Rs.

Many Brazilian researchers have long been interested in the development and use of alternative methods. Most of their research groups work in isolation, due to the lack of funding for collaborative studies. Despite these problems, since the Third World Congress on Alternatives and Animal Use in the Life Sciences, Brazilian researchers have strongly participated, not only by presenting posters and oral presentations, but also by being involved in the World Congress Committees. The Brazilian Center for the Validation of Alternative Methods (BraCVAM) must play an important role in the development and validation of alternative methods, through the active participation of the National Network of Alternative Methods (ReNaMA). In Brazil, Law 11,794/2008 regulates the use of animals in experimentation and education, and Law 9,605/1998 clearly states that use of the original animal test is not permitted, if an alternative method is available. Therefore, given the current legal framework, it is very important that all the Ministries involved with animal use, and the organisations responsible for funding researchers, strive to increase the financial support of those groups that are involved in the development and use of alternative methods in Brazil.

Reduction of cell viability induced by IFN-alpha generates impaired data on antiviral assay using Hep-2C cells.

Type I interferons (IFNs) exert an array of important biological functions on the innate immune response and has become a useful tool in the treatment of various diseases. An increasing demand in the usage of recombinant IFNs, mainly due to the treatment of chronic hepatitis C infection, augmented the need of quality control for this biopharmaceutical. A traditional bioassay for IFN potency assessment is the cytopathic effect reduction antiviral assay where a given cell line is preserved by IFN from a lytic virus activity using the cell viability as a frequent measure of end point. However, type I IFNs induce other biological effects such as cell-cycle arrest and apoptosis that can influence directly on viability of many cell lines. Here, we standardized a cytopathic effect reduction antiviral assay using Hep-2C cell/mengovirus combination and studied a possible impact of cell viability variations caused by IFN-alpha 2b on responses generated on the antiviral assay. Using the four-parameter logistic model, we observed less correlation and less linearity on antiviral assay when responses from IFN-alpha 2b 1000 IU/ml were considered in the analysis. Cell viability tests with MTT revealed a clear cell growth inhibition of Hep-2C cells under stimulation with IFN-alpha 2b. Flow cytometric cell-cycle analysis and apoptosis assessment showed an increase of S+G2 phase and higher levels of apoptotic cells after treatment with IFN-alpha 2b 1000 IU/ml under our standardized antiviral assay procedure. Considering our studied dose range, we also observed strong STAT1 activation on Hep-2C cells after stimulation with the higher doses of IFN-alpha 2b. Our findings showed that the reduction of cell viability driven by IFN-alpha can cause a negative impact on antiviral assays. We assume that the cell death induction and the cell growth inhibition effect of IFNs should also be considered while employing antiviral assay protocols in a quality control routine and emphasizes the importance of new approaches for IFN potency determination.

Uso do conceito do erro total, dos perfis de exatidão e do índice de exatidão no pré-estudo de validação de ensaio imunoenzimático / Use of the total error concept, the accuracy profiles and the accuracy index in the pre-study validation of an enzyme-linked immunosorbent assay

O uso do conceito do Erro Total em validação de métodos analíticos é abordagem que incorpora a expressão da soma da veracidade e da precisão. Esse método utiliza ainda os Perfis de Exatidão baseados em intervalos de tolerância (ou intervalos de predição) para decidir se um modelo de calibração dará resultados de qualidade e prevê o controle do risco de aceitar uma metodologia imprópria. Com a finalidade de avaliar o uso dessas ferramentas para efetuar a validação de bioensaios, foram aplicados o Conceito do Erro Total,os perfis de Exatidão e os Índices de Exatidão no pré-estudo de validação de ELISA para determinar o teor de ovoalbumina em vacinas, abrangendo-se o intervalo de 33-167 por cento da concentração alvo (5,0μg/mL) e um intervalo controle abaixo dessa faixa (0,33-2,5 por cento). O pré-estudo de validação demonstrou que o ensaio apresenta exatidão, precisão, linearidade e veracidade em conformidade no intervalo de concentrações 1,25-10μg/mL, e mostrou ser ensaio confiável para avaliar o teor de ovalbumina. A abordagem do conceito do Erro Total é ferramenta para efetuar validações que apresentam desempenho superior à abordagem clássica, que avalia os componentes de veracidade e precisão isoladamente, e é capaz de identificar deficiências na Exatidão de um bioensaio.

Avaliação comparativa da atividade biológica de heparinas não fracionadas pelas metodologias de inibição da coagulação do plasma ovino (ICPO) e de tempo de tromboplastina parcial ativada (TTPA) / Comparative study on the biological activity of non-fractionated heparin by using sheep plasma coagulation inhibition assay (SPCIA) and activated partial thromboplastin time (APTT) methodologies

O objetivo deste trabalho foi realizar o estudo comparativo entre os métodos ICPO e TTPA, para avaliar a eficácia da implantação do TTPA como método para a avaliação da segurança e eficácia de heparinas não fracionadas em produtos farmacêuticos. Foram avaliados, comparativamente, cinco lotes de diferentes fabricantes de heparinas não fracionadas (polissacarídeo sulfatado usado como droga anticoagulante), de origem suína ou bovina, testadas com base no 5º Padrão Internacional de Heparina. Esses produtos foram provenientes de coletas efetuadas pelas autoridades sanitárias para análise no Instituto Nacional de Controle de Qualidade em Saúde (INCQS). As amostras foram analisadas quanto à pureza e potência anticoagulante, por meio de duas metodologias: inibição da coagulação do plasma ovino (ICPO) e tempo de trombo plastina parcial ativada (TTPA). Houve boa concordância entre as duas metodologias, sendo que a técnica TTPA apresentou ser mais simples, rápida e objetiva, quando da utilização do coagulômetro para a medição do tempo de formação de coágulos, em detrimento da leitura subjetiva dos graus de coagulação no ensaio de ICPO. A implantação e a execução do TTPA em paralelo à utilização do ICPO garantirão o aumento de sensibilidade técnica na avaliação da segurança e eficácia de heparinas não fracionadas.

Potency determination of recombinant IFN-alpha based on phosphorylated STAT1 using flow cytometry.

The interferon (IFN) family of cytokines is recognized as a key component of the innate immune response and the first line of defense against viral infection. The usage of the IFN-alpha as a biopharmaceutical has been mainly applied in the treatment of chronic hepatitis C. In the literature it is possible to find a great variety of methods to determine the potency of these cytokines, and many efforts have been made in order to develop practical bioassays to study the biological activity of IFNs. In this technical note, we present a different approach to determine the potency of a recombinant IFN-alpha preparation based on the activation of the signal transducers and activators of transcription 1 (STAT1) using flow cytometry technique. Under the conditions of this study, this new approach proved to be useful and promising to assess the potency of these biopharmaceuticals and may also be used as an important tool in the quality control of such biological products.

Aplicação do conceito do erro total na validação do ensaio de potência da vacina oral contra a poliomielite / Use of the total error approach for validating the potency assay for oral poliomyelitis vaccine

Esta pesquisa foi realizada utilizando-se uma abordagem alternativa na validação do ensaio de potênciada vacina oral contra a poliomielite para traçar o perfil deste ensaio, levando-se em conta a grande variabilidade de ensaios biológicos. Foram adotadas duas abordagens para a validação do ensaio: a abordagem Clássica da “International Conference on Harmonization” aplicada aos ensaios biológicos e a abordagem do Conceito do Erro Total. As principais características avaliadas no estudo de validação, por se tratar de um ensaio quantitativo, foram a veracidade, a precisão e a exatidão. Foram ainda avaliadas: a adequação do ensaio aos critérios de aceitação preconizados pelo Food and Drug Administration (EUA) para validação, adotando-se a variação máxima aceita de 20 por cento, a reprodutibilidade do ensaio em uma abordagem prática, com o uso das variâncias entre os resultados de potência de 39 lotes da vacina (do mesmo produtor) obtidos no INCQS e no laboratório produtor, por amostra, para calcular o Coeficiente de Variação geométrico geral. Foi também determinada a Incerteza de Medição do Teste. O ensaio apresentou veracidade e precisão satisfatórias, o que demonstrou sua Exatidão satisfatória para a intenção de uso nas duas abordagens de validação.

Comparação entre conjugados in house e comerciais pela técnica de rápida inibição de focos fluorescentes (RFFIT) na avaliação de anticorpos antirrábicos / Comparison of in house and commercial conjugates by rapid fluorescent focus inhibition test (RFFIT) in rabies antibodies evaluation

A raiva é uma zoonose letal transmitida ao homem pela inoculação do vírus rábico, principalmente pela mordedura de animais infectados. Em 2005, o Ministério da Saúde brasileiro gastou cerca de R$66 milhões com ações de vigilância epidemiológica, empregados em campanha de vacinação e na aquisição de imunobiológicos. O controle sorológico é exigência básica para a correta avaliação da pessoa vacinada. Neste trabalho, 91 soros de 34 indivíduos foram submetidos à titulação de anticorpos pela técnica de rápida inibição de focos fluorescentes, adaptada a microplacas de 96 poços, para comparar um conjugado produzido in house com outro comercial. Do total, 74 soros (82,2por cento) apresentaram título maior ou igual a 0,5UI/mL e 12 soros (13,33por cento), título menor que 0,5UI/mL. Estes resultados mostram que a rápida inibição de focos fluorescentes utilizando o conjugado produzido in house foi tão sensível quanto com o conjugado comercial. As diferenças entre os conjugados não foram significativas e os títulos de anticorpos apresentaram elevada correlação (r = 0,94).

Potency evaluation of rabies vaccine for human use: the impact of the reduction in the number of animals per dilution.

In order to evaluate the effects of reducing the number of animals used in the NIH mouse protection test for potency determination of inactivated rabies vaccines for human use, a retrospective study of the results obtained in the Brazilian National Control Laboratory, Instituto Nacional de Controle de Qualidade em Saúde (INCQS), was performed, comprising 214 vaccine lots. The INCQS Standard Operating Procedure establishes the use of three vaccine dilutions and 18 animals per dilution, separated into two cages with 9 mice each. The results of the two cages of each dilution were considered as two different groups (C1 and C2), and therefore, for each vaccine lot, three results were obtained: one for the standard test (ST) with 18 mice, one using the C1 cages with 9 mice and another using the C2 cages with 9 mice. The results were evaluated as repeated measures of the same method on the same samples. In this study, the effects of the reduction in: (a) the measurement error and its association with the size of measurement, (b) the agreement between the results using the concordance coefficient of correlation, (c) the agreement of categorized results as "Pass" or "Fail" using the Kappa index, (d) the precision of potency determinations using the 95% confidence interval and (e) the incidence of statistically invalid assays due to non-linearity and non-parallelism were evaluated. It was concluded that the results from the NIH mouse protection test using 9 mice per dilution are in good agreement with the results obtained using 18 mice per dilution. Therefore, nine animals per dilution is a suitable number to meet the statistical requirement for valid assays.