BACKGROUND The Zika virus (ZIKV) epidemics that affected South America in 2016 raised several research questions and prompted an increase in studies in the field. The transient and low viraemia observed in the course of ZIKV infection is a challenge for viral isolation from patient serum, which leads to many laboratories around the world sharing viral strains for their studies. C6/36 cells derived from Aedes albopictus larvae are commonly used for arbovirus isolation from clinical samples and for the preparation of viral stocks. OBJECTIVES Here, we report the contamination of two widely used ZIKV strains by Brevidensovirus, here designated as mosquito densovirus (MDV). METHODS Molecular and immunological techniques were used to analyse the MDV contamination of ZIKV stocks. Also, virus passages in mammalian cell line and infecting susceptible mice were used to MDV clearance from ZIKV stocks. FINDINGS MDV contamination was confirmed by molecular and immunological techniques and likely originated from C6/36 cultures commonly used to grow viral stocks. We applied two protocols that successfully eliminated MDV contamination from ZIKV stocks, and these protocols can be widely applied in the field. As MDV does not infect vertebrate cells, we performed serial passages of contaminated stocks using a mammalian cell line and infecting susceptible mice prior to re-isolating ZIKV from the animals’ blood serum. MDV elimination was confirmed with immunostaining, polymerase chain reaction (PCR), and analysis of the mosquitoes that were allowed to feed on the infected mice. MAIN CONCLUSIONS Since the putative impact of viral contaminants in ZIKV strains generally used for research purposes is unknown, researchers working in the field must be aware of potential contaminants and test viral stocks to certify sample purity.

OBJETIVO: Vírus da família Adenoviridae estão associados com muitas síndromes clínicas, sendo conhecidos 50 sorotipos. Vírus desta família e da família Herpesviridae são os maiores responsáveis por conjuntivite viral, sendo um rápido diagnóstico importante devido ao caráter epidêmico das infecções por adenovírus. MÉTODOS: Reação em cadeia da polimerase (PCR) para adenovírus foi desenvolvida utilizando iniciadores que amplificam um fragmento de 300 bp do gene da proteína hexon do capsídeo de diversos sorotipos. A reação em cadeia da polimerase foi efetuada sem a etapa de extração de DNA. RESULTADOS: Amostras de "swabs" de córneas de sete pacientes com ceratoconjuntivite foram analisadas, sendo que uma amostra foi positiva para adenovírus. O seqüenciamento deste fragmento mostrou 100% de homologia com a seqüência do adenovírus tipo 8. CONCLUSÃO: O seqüenciamento do fragmento de 300 bp do gene do hexon permite a identificação de quase todos os sorotipos de adenovírus, incluindo aqueles relacionados com a ceratoconjuntivite epidêmica (8,19,37) e todas as amostras associadas com conjuntivite.

PURPOSE: Viruses of the Adenoviridae family are associated with many clinical syndromes, possessing 50 serotypes. These agents and viruses of the Herpesviridae family are the two major agents responsible for viral conjunctivitis, and a rapid diagnosis is important due to the epidemic character of adenoviral infections. METHODS: We developed a PCR without DNA extraction for adenovirus using primers that amplify a 300 bp fragment of the hexon capsid protein gene from many serotypes. RESULTS: Swab samples from cornea of seven patients with keratoconjunctivitis were analyzed, and one of them was PCR positive for adenovirus. The sequence of this fragment shows a 100% homology with the sequence of adenovirus type 8. CONCLUSION: Sequencing of 300 bp from the hexon gene allows to identify almost all Ad serotypes, including all serotypes related to epidemic keratoconjunctivitis (8,19,37) and almost all serotypes involved with Ad-associated conjunctivitis.