RESUMEN
Extracts from termite-associated bacteria were evaluated for in vitro antiviral activity against bovine viral diarrhea virus (BVDV). Two bacterial strains were identified as active, with percentages of inhibition (IP) equal to 98%. Both strains were subjected to functional analysis via the addition of virus and extract at different time points in cell culture; the results showed that they were effective as posttreatments. Moreover, we performed MTT colorimetric assays to identify the CC50, IC50, and SI values of these strains, and strain CDPA27 was considered the most promising. In parallel, the isolates were identified as Streptomyces through 16S rRNA gene sequencing analysis. Specifically, CDPA27 was identified as S. chartreusis. The CDPA27 extract was fractionated on a C18-E SPE cartridge, and the fractions were reevaluated. A 100% methanol fraction was identified to contain the compound(s) responsible for antiviral activity, which had an SI of 262.41. GC-MS analysis showed that this activity was likely associated with the compound(s) that had a peak retention time of 5 min. Taken together, the results of the present study provide new information for antiviral research using natural sources, demonstrate the antiviral potential of Streptomyces chartreusis compounds isolated from termite mounds against BVDV, and lay the foundation for further studies on the treatment of HCV infection.
RESUMEN
Bovine respiratory syncytial virus (BRSV) causes pneumonia in young cattle. Modified-live-virus (MLV) and inactivated vaccines are currently used for the control of clinical effects of BRSV infections in cattle. On the present research, the stimulation of specific anti-BRSV immunoglobulin isotypes was investigated, through the use of different commercially available adjuvants (Water-in-oil emulsion, Quil A, Aluminum-hydroxide) in inbred mice (Balb/C and C57BL/6). BRSV antibodies were measured using an enzyme-linked immunosorbent assay (ELISA) and the results were compared to the antibody levels induced by immunization of animals using live-BRSV-virus. Water-in-oil emulsion and alum- adjuvant preparations induced higher levels of IgG1 immunoglobulins, whereas Quil A favored the production of IgG2 antibodies, this last being a more appropriate response profile for the specific case of BRSV. Not using adjuvants resulted in poor levels of specific antibodies. The isotype profile of specific antibodies obtained varied greatly depending on the adjuvants used. This information may be useful for the formulation of more effective BRSV inactivated vaccines; however, these findings have to be confirmed in cattle.
O vírus respiratório sincicial bovino (BRSV) causa pneumonia em bovinos jovens. Vacinas de vírus vivo modificado (MLV) e vacinas inativadas são atualmente utilizadas para o controle dos efeitos clínicos de infecções pelo BRSV em bovinos. No presente trabalho, investigou-se a estimulação dos isotipos de imunoglobulinas específicas anti-BRSV, através da utilização de diferentes adjuvantes disponíveis comercialmente (água em óleo de emulsão, Quil A, hidróxido de alumínio) em camundongos isogênicos (Balb/C e C57BL/6). Anticorpos contra o BRSV foram medidos usando-se um ensaio imunoenzimático (ELISA), e os resultados foram comparados com os níveis de anticorpos induzidos pela imunização de animais utilizando-se o BRSV vivo. As preparações em que se empregou óleo mineral e alumínio como adjuvantes induziram altos níveis de imunoglobulinas IgG1, enquanto QuilA favoreceu a produção de anticorpos de classe IgG2, sendo este último um perfil de resposta mais desejável para o caso específico de BRSV. A não utilização de adjuvantes resultou em baixa produção de anticorpos específicos. O perfil de isotipos de imunoglobulinas secretados variou bastante conforme o adjuvante utilizado. Esta informação pode ser útil futuramente na formulação de vacinas inativadas mais eficazes contra o BRSV. Todavia, esses achados devem ser confirmados em bovinos.