Mimivírus em ambiente hospitalar: avaliação da distribuição e da diversidade biológica, molecular e estrutural de isolados virais

Abstract

In 1992, during a pneumonia outbreak, a giant virus was isolated from cooling towers in England. This new virus, called canthamoeba polyphaga mimivirus (APMV), infects Acanthamoeba amoebas, and is the prototype virus of Mimivirus genus, which belongs to the group of Nucleo-Citoplasmatic Large DNA Virus (NCLDVs). Pneumonia is a leading cause of death related to infection throughout the world, however, about 20 to 50% of the cases present unknown etiology. Studies have pointed out some virus belong to the Mimivirus genus (mimivirus) as putative agents of pneumonia in humans. Considering this background, this study aimed to evaluate the distribution of mimivirus in different areas of the Hospital das Clínicas (HC) in Belo Horizonte UFMG. For this, 242 hospital dust samples were collected, processed, and subjected to real-time PCR and isolation. Some of the isolated viruses were purified and subjected to molelular characterization (sequencing and phylogenetic analysis), biological characterization (resistance assays, multiplication curve, gene expression profile) and structural characterization tests (morphometric, transmission and scan electron microscopy and analysis of structural proteins). As experimental control, samples were also collected from various facilities of the Instituto de Ciências Exatas (ICEX) of UFMG. The results demonstrated a differential distribution of mimivirus in the hospital, revealing a higher number of positive samples in respiratory isolation facility than in other analyzed environments. It was not possible to isolate any virus from ICEX/UFMG. In general, biological, molecular and structural characterization of new isolates showed some similarity between these viruses and mimiviruses group A, as the APMV prototype. However, some differences in the multiplication curve, nucleotide composition of viral RNA helicase gene and in the expression of genes involved in translation were observed, suggesting the existence of some biological differences in new viral isolates. The volume of evidence linking the mimivirus with nosocomial pneumonia is increasing and our work is the first to demonstrate a significant spatial association between the site occupied by patients with pneumonia and isolated APMV. Our results reinforce the need to control the presence of these viruses in the hospital.