Investigação da infecção por chikungunya virus em primatas não humanos no estado de Minas Gerais de 2017 a 2020 e adaptação de teste de neutralização viral utilizando tecido hepático

Abstract

The chikungunya virus (CHIKV) is the causative agent of chikungunya fever (CHIKF). The virus was introduced into Brazil in 2013 and one of the states most affected by cases of CHIKF was Minas Gerais, which had a high incidence of the disease in 2017. In Brazil, CHIKV is maintained in the wild in an urban cycle involving Aedes aegypti and human hosts. In Africa, in addition to the urban cycle, there is a wild cycle of the virus involving Aedes mosquitoes and non-human primates (NHP) as hosts. The circulation of CHIKV in wild environments in Brazil has not yet been described, but there is a risk of this cycle being established, given that viral circulation persists in urban centers and that there are competent vectors in peri-urban and rural environments. The detection of neutralizing antibodies against CHIKV in PNH samples from the northeast of the country has already been described, indicating a possible circulation of this virus in the wild host. Thus, the aim of this study is to investigate the circulation of CHIKV in NHP collected in the state of Minas Gerais from 2017 to 2020 and also to optimize an adapted neutralization test using liver tissue samples. For the molecular tests, total RNA was extracted from 407 liver samples from NHPs, which were then subjected to RT-qPCR to detect the endogenous control. Once this was done, when RT-qPCR was carried out targeting the CHIKV E1 gene, the samples tested were negative. Samples of liver tissue were macerated, clarified and the homogenate used to investigate neutralizing antibodies. When comparing the results of the tests carried out on samples from mock and experimentally infected animals, a significant difference was observed between the neutralization percentages, indicating anti-CHIKV neutralizing action in samples from infected animals. After this, adapted viral neutralization tests were carried out with liver homogenate from NHP collected in Minas Gerais, in urban areas, in 2017. Of the 25 samples tested, one showed neutralization above 90% (1:20 dilution), indicating the presence of neutralizing anti-CHIKV antibodies. The lack of molecular detection of CHIKV and the detection of anti-CHIKV antibodies in NHP samples highlights the importance of epidemiological surveillance and the use of other methods, such as serology, for a more complete investigation. Given the limitations of molecular techniques, the adapted neutralization test can contribute to a better understanding of the circulation of CHIKV in wild animals in Minas Gerais.