VA-MENGOC-BC Vaccination Induces Serum and Mucosal Anti Neisseria gonorrhoeae Immune Responses and Reduces the Incidence of Gonorrhea.

BACKGROUND: Overall, there are over 30 different sexually transmitted infections with Neisseria gonorrhoeae being the third most frequent with a reported 78 million cases per year. Gonococcal infection causes genital inflammation, which can be a risk factor for others sexually transmitted infections, particularly human immunodeficiency virus. Gonorrhea is a treatable disease, but recently an increase in antibiotic resistance has been of concern. There are currently no vaccines available. However, parenteral vaccination with anti N. meningitidis serogroup B vaccine has been reported to decrease the incidence of gonococcal burden in New Zealand and in Cuba despite the fact that parenteral vaccination is not deemed to induce mucosal IgA. Here we explore possible mechanisms of protection against gonococcal infection through parenteral meningococcal B vaccination. METHODS: Ninety-two serum, saliva and oropharyngeal swabs samples of young adults (healthy and Neisseria carriers) of the internal higher school were obtained. They have been vaccinated with VA-MENGOC-BC (MBV) during their infancy and boosted with a third dose during this study. Serum and saliva samples were analyzed by ELISA and Western blot to measured IgG and IgA antibodies against N. meningitidis and N. gonorrhoeae antigens. N. meningitidis carriers were determined by standard microbiologic test. In addition, we reviewed epidemiologic data for N. meningitidis and N. gonorrhoeae infections in Cuba. RESULTS: Epidemiologic data show the influence of MBV over gonorrhea incidence suggesting to be dependent of sexual arrival age of vaccines but not over syphilis. Laboratorial data permit the detection of 70 and 22 noncarriers and carriers of N. meningitidis, respectively. Serum anti-MBV antigens (PL) responses were boosted by a third dose and were independent of carriage stages, but saliva anti-PL IgA responses were only present and were significant induced in carriers subjects. Carriers boosted with a third dose of MBV induced similar antigonococcal and -PL saliva IgA and serum IgG responses; meanwhile, serum antigonococcal IgG was significantly lower. In saliva, at least 2 gonococcal antigens were identified by Western blot. Finally, gonococcal-specific mucosal IgA antibody responses, in addition to the serum IgG antibodies, might contributed to the reduction of the incidence of N. gonorrhoeae. We hypothesize that this might have contributed to the observed reductions of the incidence of N. gonorrhoeae. CONCLUSION: These results suggest a mechanism for the influence of a Proteoliposome-based meningococcal BC vaccine on gonococcal incidence.

Evaluación de formulaciones inmunoterapéuticas experimentales en el modelo hibrido murino de Reaccion del Injerto contra el Hospedador / Evaluation of experimental immunotherapeutic formulations in the hybrid murine model of Graft-versus-Host Reaction

Introducción: La Enfermedad del Injerto Contra el Hospedador es la complicación más frecuente de los Trasplantes de Células Madre Hematopoyéticas y de todos los trasplantes que contengan células inmunocompetentes alogénicas, el 100 por ciento la padecen y cerca del 30 por ciento mueren por su causa; una proporción alta de casos son esteroide-refractarios, asimismo otras medidas inmunosupresoras modernas fracasan. En los campos de la Inmunoterapia y la Vaccinología también existe una escasez preocupante de inmunomoduladores de origen biológico potentes, efectivos, seguros y de amplio espectro. Existe un modelo híbrido murino de gran utilidad metodológica para estudios experimentales. Objetivo: Evaluar dos formulaciones novedosas de origen biotecnológico, una de ellas inmunopotenciadora y otra inmunosupresora, desarrolladas como cocleatos. Material y Métodos: Mediante Microscopia Electrónica y RT-PCR se caracterizaron las formulaciones como nanopartículas y su capacidad de regular la expresión del ARNm de linfoquinas definitorias de sus perfiles, respectivamente. Empleando el modelo de Enfermedad del Injerto Contra el Hospedador en ratón híbrido F1 (CBAxC57BL), se evaluó su carácter inmunomodulador in vivo . Resultados: Partiendo de los proteoliposomas de Neisseria meningitidis, se obtuvieron dos formulaciones en forma de cocleatos, ambas con diámetros de partícula inferior a 100nm. La Formulación 1mostró un perfil proinflamatorio con potente capacidad de aumentar el IFNγ y el TNFα y potenció el Índice de Bazo hasta 2,05 en el modelo EICH con p=0,0002. La Formulación 2 mostró un perfil supresor-regulatorio con potente capacidad de aumentar la IL-10 y el TGFβ y además de suprimir la producción de TNFα. En el modelo usado, esta formulación, suprimió el Índice de Bazo de manera dosis dependiente y con alta significación estadística. Se corroboró el conocido perfil de seguridad y ausencia de reactogenicidad de ambas formulaciones. Conclusiones: Ambas formulaciones tienen potencial aplicación en los campos de la terapia de Enfermedad del Injerto Contra el Hospedador en otras patologías y en Vaccinología. Los resultados obtenidos en el presente trabajo fundamentan la conveniencia de continuar el desarrollo farmacéutico y completar la preclínica de ambas formulaciones(AU)

Introduction: Graft-versus-host disease is the most frequent complication of Hematopoietic Stem Cell Transplants and all transplants containing allogeneic immunocompetent cells; 100 percent of patients suffer from this complication and about 30 percent die for this particular cause. A high proportion of cases are steroid-refractory; likewise, other modern immunosuppressive measures fail. In the fields of Immunotherapy and Vaccinology, there is also a worrying shortage of powerful, effective, safe and broad spectrum immunomodulators of biological origin. There is a hybrid murine model of great methodological utility for experimental studies. Objective: To evaluate two novel formulations of biotechnological origin: an immunopotentiator formulation and an immunosuppressive one, which were developed as cochleates. Material and Methods: The formulations assayed by Electron Microscopy and RT-PCR were characterized as nanoparticles and for their capacity to regulate lymphokine mRNA expression profile, respectively. The immunomodulatory character was evaluated in vivo using Graft-versus-host disease in (CBAxC57BL) F1 hybrid mice. Results: Starting from the proteoliposomes derived from Neisseria meningitides, two cochleate formulations were obtained, both with particle diameters below 100 nm. Formulation 1 showed a proinflammatory profile with potent capacity to increase IFNγ and TNFα, and potentiated the Spleen Index up to 2.05 in the GVDH model with p = 0.0002. Formulation 2 showed a suppressor/regulatory profile with potent capacity to increase IL-10 and TGFβ and suppress the production of TNFα. In the model used, this formulation suppressed the Spleen Index in a dose-dependent manner with high statistical significance. The known safety profile and absence of reactogenicity of both formulations was corroborated. Conclusions: Both formulations have potential application in the fields of GVHD therapy and other pathologies as well as in Vaccinology. The results obtained in the present work suggest the usefulness to continue with the pharmaceutical development and complete the preclinical studies of both formulations(AU)

Remote induction of cellular immune response in mice by anti-meningococcal nanocochleates - nanoproteoliposomes.

New adjuvant formulations, based on proteoliposomes <40 nm and cochleates <100 nm, without Al(OH)3 adjuvant, were evaluated regarding their ability to generate Th1 immune response through a Delayed -Type Hypersensitivity Test, at the mouse model, by using a Neisseria meningitidis B protein complex as antigen. The formulations were administered by intramuscular (IM) (2 inoculations - at baseline and after 14 days) and intranasal (IN) (3 inoculations at 7 days) immunization pathways. All IM immunized groups were able to induce similar response to these formulations as well as to VA-MENGOC-BC® vaccine - containing Al(OH)3 adjuvant (used as positive control of the trial). In all groups, the induced inflammation (IP) rate was statistically higher than in the negative control group (CN) (p < 0.05). Immunogenicity, measured by HSR and CD4+ lymphocyte increase was equivalent to the control vaccine and most important, granuloma reactogenicity at the site of injection was eliminated, fact demonstrated by histological study. All groups of animals immunized by IN route showed HSR reactions and statistically significant differences with respect to the CN group. However, IP values were lower, with statistical differences (p < 0.05) for the same adjuvant formulation IM administered, except the AIF2-nCh formulation that generated statistically similar induction (p > 0.05) by both immunization pathways, suggesting it to be the best candidate for the next IN trial. Proteoliposome and cochleate formulations tested were able to mount potent Th-1 immune response, equivalent to the original vaccine formulation, with the advantage of less reactogenicity in the site of the injection, caused by the toxicity of Al(OH)3 adjuvant gel.

Cuban Meningococcal Vaccine VA-MENGOC-BC:30 Years of Use and Future Potential.

Every year, meningococcal infection by Neisseria meningitidis causes over 500,000 cases and 85,000 deaths in the world, with 20% of survivors suffering sequelae. In Cuba its incidence in 1980 reached 5.9 cases per 100,000 population; about 80% of cases were serogroup B, prompting health authorities to declare meningococcal disease the country's main public health problem. Several provinces reported over 120 cases per 100,000 children aged < 1 year, overwhelmingly serogroup B. At that time, no vaccines existed with proven efficacy against N. meningitidis serogroup B, nor was there a vaccine candidate that could be successful in the short term. By 1989, researchers in Havana had developed a Cuban meningococcal B and C vaccine, VA-MENGOC-BC, the world's first against serogroup B meningococcal disease. Its efficacy of 83% was demonstrated in a prospective, randomized, double-blind, placebo-controlled field study. Vaccine production used vesicle or proteoliposome technology for the first time. The same year, the World Intellectual Property Organization awarded its gold medal to the main authors of the VA-MENGOC-BC patent. The vaccine was used in a mass vaccination campaign and later included in Cuba's National Immunization Program, with a cumulative impact on incidence of serogroup B meningococcal disease greater than 95% (93%-98%). Mass, systematic vaccination shifted the spectrum of meningococcal strains in healthy asymptomatic carriers and strains circulating among population groups toward nonvirulent phenotypes. The disease ceased to be a public health problem in the country. VA-MENGOC-BC is the most widely applied vaccine against serogroup B meningococcal disease in the world. Over 60 million doses have been administered in Latin America. In several countries where it has been applied, in which strains other than the vaccine-targeted strains circulate, VA-MENGOC-BC has demonstrated effectiveness against all (55%-98% in children aged < = 4 years and 73%-100% in children aged > 4 years). The vaccine and its proteoliposome technology have had an impact and continue to have potential, not only for meningococcal disease, but also for development of other vaccines and adjuvants.KEYWORDS Neisseria meningitidis, meningococcal disease, meningo-coccal vaccine, biotechnology, pharmaceutical industry, bacterial menin-gitis, meningococcal meningitis, immunization, vaccination, Cuba.

Influencia del medio de cultivo sobre la cinética de crecimiento y expresión de la proteína recombinante Rv2626c de Mycobacterium tuberculosis H37Rv expresada en Streptomyces lividans TK24 / Influence of the culture medium on the kinetics of growth and expression of the recombinant protein Rv2626c of Mycobacterium tuberculosis H37Rv expressed in Streptomyces lividans TK24

Streptomyces lividans, ha ganado gran atención en los últimos tiempos, como vector de expresión y producción de proteínas de Mycobacterium tuberculosis de interés biomédico, como alternativa a su obtención tradicional en E. coli. La proteína Rv2626c, Proteína de Respuesta Hipóxica 1, es codificada por el gen Rv2626c (hrp1) de M. tuberculosis, perteneciente al regulón de la fase de latencia DosR. Esta proteína se sobre-expresa en la fase de latencia de la tuberculosis bajo condiciones de estrés como hipoxia y bajos niveles, de óxido nítrico. Se ha demostrado la inmunogenicidad y capacidad de esta proteína, de inducir citocinas características del patrón Th-1, tales como el interferón gamma. Por ello, nuestro grupo logró la obtención de Rv2626c por la tecnología del ADN recombinante usando como cepa hospedera Streptomyces lividans TK24. Con el objetivo de aumentar el nivel de expresión de la proteína recombinante, rRv2626c en este trabajo se ensayaron diferentes medios de cultivo, evaluando el crecimiento de la cepa transformada en condiciones de zaranda. Se determinó la cinética de crecimiento en el medio definido, formulado industrialmente en el Centro Nacional de Biopreparados: caldo Triptona Soya (TSB-BioCen) y en medio de cultivo equivalente preparado en el laboratorio. Para establecer la cinética de crecimiento, se utilizó el cálculo del peso seco y la determinación de la concentración de proteínas totales por la técnica de ácido bicinconinico (BCA) a diferentes tiempos del cultivo. Posteriormente, se identificó la proteína clonada mediante SDS-PAGE y Western Blotting, así como los niveles de expresión mediante análisis densitométrico. Los resultados indican que se alcanzaron los máximos niveles de densidad celular a las 36 h de cultivo y los más altos niveles de expresión proteica total y específica entre las 42 y 54 h. Con el medio químicamente definido TSB-Biocen preformulado en lugar del preparado en el laboratorio partiendo de los componentes, se logró reducir el tiempo óptimo para la expresión-secreción de la proteína rv2626c de 96 a 54 h. Los mejores resultados en la promoción de la expresión de la proteína recombinante se lograron con el medio definido TSB-BioCen, a las 48 h con 8,5% de rendimiento específico, superando en más de 10 veces los niveles de crecimiento celular obtenidos con el medio elaborado en el laboratorio y más de dos veces los niveles de secreción de la proteína recombinante(AU)

The use of Streptomyces as a bacterial cell factory for the secretory production of bio-active Mycobacterium tuberculosis proteins have gained a lot of attention in recent years, as a convenient alternative to the traditionally used Escherichia coli. The protein Rv2626c protein, also known as Hypoxic Response Protein 1 (HRP1), is encoded by the gene rv2626c (hrp1) of M. tuberculosis which belongs to the Dormancy Safety Regulator (DosR) regulon. This protein is over-expressed during the latency phase of tuberculosis under stress related conditions such as hypoxia and low, non-toxic, levels of nitric oxide and, the immunogenicity and ability to induce cytokines characteristic of the Th-1 pattern of this protein, such as gamma interferon, have been demonstrated. On this basis, our working group, succeeded in obtaining rRv2626c via recombinant DNA technology using Streptomyces lividans TK24 as the host cell. To improve the expression level of the protein, different culture media were used to evaluate the growth of the transformed strain in shaken flask conditions. Growth kinetic for the recombinant strain was evaluated in defined media of preformulated tryptic soya broth (TSB-Biocen), through the determination of dry weight as well as total protein concentration by Bicinconinic acid assay (BCA). Protein identification was done by SDS-PAGE, Western Blot and its expression level by densitometric analysis. Our results indicated a maximal cell density at 36 h of culture, with higher concentration of total and specific protein at 42-54 h in comparison with previous media used. With the chemically defined media a preformulated TSB-Biocen rather than individual components, culture time for expression/secretion of rRv2626c was reduced from 96 h to 54 h. The best results in expression-secretion levels of rv2626c protein were obtained with the TSB-Biocen defined media at 48 h of culture with 8.5% of specific yield. More than 10 fold increase in cellular growth and more than 2 fold increase in specific yield(AU)

Ciencia e innovación tecnológica en la salud en Cuba: resultados en problemas seleccionados

[RESUMEN]. En Cuba, la investigación para la salud se basa en las prioridades de la política científica nacional, derivadas del estado de salud de la población. El objetivo de este artículo es describir las características del Sistema de Ciencia e Innovación Tecnológica en el sector y cómo los resultados de sus investigaciones benefician la salud de los grupos poblacionales. Para ello se seleccionaron investigaciones relacionadas con la generación de productos y tecnologías, la diabetes, el dengue y la discapacidad. Este sistema sigue los preceptos metodológicos del Ministerio de Ciencia, Tecnología y Medio Ambiente y cuenta con 37 entidades de investigación. Se organiza en programas y proyectos que favorecen la investigación básica y aplicada, con un enfoque multidisciplinario e intersectorial; estos son financiados mayormente por el Estado y organizados en ciclos cerrados o completos, es decir, una misma entidad se encarga de todo el proceso, desde la investigación hasta la comercialización, incluidos los estudios de mercados y la vigilancia poscomercialización. Las investigaciones seleccionadas evidencian la armonía entre la investigación, la generalización de los resultados y su efecto en mejorar la salud y el acceso universal de la población. Se lograron resultados en métodos de diagnóstico, vacunas preventivas y terapéuticas, signos de alarma para el pronóstico y tratamiento del dengue, prevención de malformaciones congénitas, y políticas y programas que han beneficiado a las personas con discapacidad y sus familiares. La voluntad del Estado para desarrollar y financiar la investigación científica, la acción intersectorial, la definición de las prioridades de investigación, y la preparación y atención sistemática del capital humano han sido factores determinantes para el cumplimiento de los objetivos del sistema.

[ABSTRACT]. In Cuba, health research is based on the priorities of national scientific policy, derived from the health status of the population. The objective of this article is to describe the characteristics of the System of Science and Technological Innovation and how the results of its research benefit the health of the population groups. To this end, research related to the generation of products and technologies, diabetes, dengue and disability was selected. This system follows a methodology outlined by the Ministry of Science, Technology and Environment and has 37 research entities. It is organized into programs and projects that favor basic and applied research, with a multidisciplinary and intersectoral approach; these programs and projects are funded mostly by the State and are organized in self-contained cycles, i.e., the same entity is responsible for the entire process, from research to marketing, including market studies and post-marketing surveillance. The selected research shows an alignment between the research, the generalization of the results and its effect in improving health and universal access to health in the population. Positive results were obtained in diagnostic methods, preventive and therapeutic vaccines, warning signs for the prognosis and treatment of dengue, prevention of congenital malformations, and policies and programs that have benefited people with disabilities and their families. The will of the State to develop and fund scientific research, intersectoral action, the definition of research priorities, and the systematic training and attention to human resources have been key factors for the fulfillment of the objectives of the system.

[RESUMO]. Em Cuba, a pesquisa em saúde baseia-se nas prioridades da política científica nacional, derivadas do estado de saúde da população. O objetivo deste artigo é descrever as características do Sistema de Ciência e Inovação Tecnológica e como os resultados de suas pesquisas beneficiam a saúde dos grupos populacionais. Para este fim, foram selecionadas pesquisas relacionadas à geração de produtos e tecnologias, diabetes, dengue e deficiência. Este sistema segue a metodologia do Ministério da Ciência, Tecnologia e Meio Ambiente e possui 37 entidades de pesquisa. Está organizado em programas e projetos que favorecem pesquisas básicas e aplicadas, com abordagem multidisciplinar e intersetorial; estes são financiados principalmente pelo Estado e organizados em ciclos fechados ou completos, ou seja, a mesma entidade é responsável por todo o processo, desde pesquisa até marketing, incluindo estudos de mercado e vigilância pós-comercialização. As pesquisas selecionadas mostram a harmonia entre a pesquisa, a generalização dos resultados e seus efeitos na melhoria da saúde e no acesso universal à saúde na população. Resultados positivos foram obtidos em métodos de diagnóstico, vacinas preventivas e terapêuticas, sinais de alerta para o prognóstico e tratamento da dengue, prevenção de malformações congênitas e políticas e programas que beneficiaram pessoas com deficiência e suas famílias. A vontade do Estado de desenvolver e financiar pesquisas científicas, ações intersetoriais, a definição de prioridades de pesquisa e o treinamento e atenção sistemática do capital humano têm sido fatores determinantes para o cumprimento dos objetivos do sistema.

Influencia del medio de cultivo sobre la cinética de crecimiento y expresión de la proteína recombinante Rv2626c de Mycobacterium tuberculosis H37Rv expresada en Streptomyces lividans TK24 / Influence of the culture medium on the kinetics of growth and expression of the recombinant protein Rv2626c of Mycobacterium tuberculosis H37Rv expressed in Streptomyces lividans TK24

Streptomyces lividans, ha ganado gran atención en los últimos tiempos, como vector de expresión y producción de proteínas de Mycobacterium tuberculosis de interés biomédico, como alternativa a su obtención tradicional en E. coli. La proteína Rv2626c, Proteína de Respuesta Hipóxica 1, es codificada por el gen Rv2626c (hrp1) de M. tuberculosis, perteneciente al regulón de la fase de latencia DosR. Esta proteína se sobre-expresa en la fase de latencia de la tuberculosis bajo condiciones de estrés como hipoxia y bajos niveles, de óxido nítrico. Se ha demostrado la inmunogenicidad y capacidad de esta proteína, de inducir citocinas características del patrón Th-1, tales como el interferón gamma. Por ello, nuestro grupo logró la obtención de Rv2626c por la tecnología del ADN recombinante usando como cepa hospedera Streptomyces lividans TK24. Con el objetivo de aumentar el nivel de expresión de la proteína recombinante, rRv2626c en este trabajo se ensayaron diferentes medios de cultivo, evaluando el crecimiento de la cepa transformada en condiciones de zaranda. Se determinó la cinética de crecimiento en el medio definido, formulado industrialmente en el Centro Nacional de Biopreparados: caldo Triptona Soya (TSB-BioCen) y en medio de cultivo equivalente preparado en el laboratorio. Para establecer la cinética de crecimiento, se utilizó el cálculo del peso seco y la determinación de la concentración de proteínas totales por la técnica de ácido bicinconinico (BCA) a diferentes tiempos del cultivo. Posteriormente, se identificó la proteína clonada mediante SDS-PAGE y Western Blotting, así como los niveles de expresión mediante análisis densitométrico. Los resultados indican que se alcanzaron los máximos niveles de densidad celular a las 36 h de cultivo y los más altos niveles de expresión proteica total y específica...(AU)

The use of Streptomyces as a bacterial cell factory for the secretory production of bio-active Mycobacterium tuberculosis proteins have gained a lot of attention in recent years, as a convenient alternative to the traditionally used Escherichia coli. The protein Rv2626c protein, also known as Hypoxic Response Protein 1 (HRP1), is encoded by the gene rv2626c (hrp1) of M. tuberculosis which belongs to the Dormancy Safety Regulator (DosR) regulon. This protein is over-expressed during the latency phase of tuberculosis under stress related conditions such as hypoxia and low, non-toxic, levels of nitric oxide and, the immunogenicity and ability to induce cytokines characteristic of the Th-1 pattern of this protein, such as gamma interferon, have been demonstrated. On this basis, our working group, succeeded in obtaining rRv2626c via recombinant DNA technology using Streptomyces lividans TK24 as the host cell. To improve the expression level of the protein, different culture media were used to evaluate the growth of the transformed strain in shaken flask conditions. Growth kinetic for the recombinant strain was evaluated in defined media of preformulated tryptic soya broth (TSB-Biocen), through the determination of dry weight as well as total protein concentration by Bicinconinic acid assay (BCA). Protein identification was done by SDS-PAGE, Western Blot and its expression level by densitometric analysis. Our results indicated a maximal cell density at 36 h of culture, with higher concentration of total and specific protein at 42-54 h in comparison with previous media used. With the chemically defined media a preformulated TSB-Biocen rather than individual components, culture time...(AU)

Determinación de IL-l usando un sistema de proliferación de timocitos / Determination of IL-l with a timocite proliferative system

La interleukina-1 (IL-1) es un factor soluble producido por células accesorias que constituye la segunda señal necesaria para la activación de células T, dependientes de macrófagos. La determinación de la IL-1 constituye un importante aspecto al medir y estudiar la inmunorreactividad in vitro y la presencia de este factor en fluidos corporales. En el presente trabajo se describe el método de proliferación de timocitos como sistema de medición de la IL-1 adaptado a nuestras condiciones de laboratorio, siendo demostrado que es posible usar otras especies de ratones además de la C3H/Hed (no respondedores al LPS) si se trabaja en el rango propuesto de concentración de LPS; (100 ug ml-1 hasta 10-3 ug ml-1). Se presentan así mismo resultados de la valoración de otros aspectos que afectan la medición tales como: tipo y concentración de los mitógenos usados (Con A, PHA), edad de los animales, tipo y por ciento de suero añadido al cultivo, número de células y tiempo de los cultivos. Se discute la importancia de los inhibidores y las posibles fluctuaciones del test como sistema biológico

Determinación de IL-l usando un sistema de proliferación de timocitos / Determination of IL-l with a timocite proliferative system

La interleukina-1 (IL-1) es un factor soluble producido por células accesorias que constituye la segunda señal necesaria para la activación de células T, dependientes de macrófagos. La determinación de la IL-1 constituye un importante aspecto al medir y estudiar la inmunorreactividad in vitro y la presencia de este factor en fluidos corporales. En el presente trabajo se describe el método de proliferación de timocitos como sistema de medición de la IL-1 adaptado a nuestras condiciones de laboratorio, siendo demostrado que es posible usar otras especies de ratones además de la C3H/Hed (no respondedores al LPS) si se trabaja en el rango propuesto de concentración de LPS; (100 ug ml-1 hasta 10-3 ug ml-1). Se presentan así mismo resultados de la valoración de otros aspectos que afectan la medición tales como: tipo y concentración de los mitógenos usados (Con A, PHA), edad de los animales, tipo y por ciento de suero añadido al cultivo, número de células y tiempo de los cultivos. Se discute la importancia de los inhibidores y las posibles fluctuaciones del test como sistema biológico