Acanthamoeba polyphaga mimivirus and other giant viruses: an open field to outstanding discoveries

Abstract

In 2003, Acanthamoeba polyphaga mimivirus (APMV) was first described and began to impact researchers around the world, due to its structural and genetic complexity. This virus founded the family Mimiviridae. In recent years, several new giant viruses have been isolated from different environments and specimens. Giant virus research is in its initial phase and information that may arise in the coming years may change current conceptions of life, diversity and evolution. Thus, this review aims to condense the studies conducted so far about the features and peculiarities of APMV, from its discovery to its clinical relevance.

Figure 1

Mimivirus particle visualized by different microscopy methods. Transmission electron microscopy of APMV showing the complete particle (A) and a zoom (B), highlighting the fibrils (F), the capsid protein layers (PL), the internal membrane (IM), and the core wall (CW) that protects the viral genome and early factors. (C) and (D) show mimivirus isolates under scanning and atomic force microscopy, respectively. Scale in (D) represents the sample depth and size.

Figure 2

Mimivirus replication cycle in amoebas. (I) Phagocytosis. (II) Virus entry into a phagosome, followed by star-gate opening and viral membrane fusion (III). (VI) Viral seed is released in the amoeba cytoplasm and gives start to an early viral factory (V). After few hours, the viral factory grows and orchestrates the morphogenesis (VI) of the viral progeny, which are released by cell lysis. At the right, transmission electron microscopy of APMV at its different steps of the replication cycle.

Figure 3

Timeline highlighting some hallmarks of mimivirus and related topics. Interest on the subject “Mimivirus”, “Poxvirus”, “Phycodnavirus” and “Asfarvirus” as a research terms in Google Search, over time. The incidence of the research for these subjects in Google Search was obtained by the use of Google Trends tool (http://www.google.com/trends/). The graphics depict relative interest over time (%). The values are in comparison to the highest number of searches at a given occasion (see “help” in Google Trends website). Google trends show available data since 2004. A timeline was set in the bottom of the figure, highlighting some hallmarks of mimivirus and related topics.

Figure 4

Cumulative number of publications relating to mimivirus and “mimivirus”/”giant viruses” over time since its discovery in 2003 (http://www.ncbi.nlm.nih.gov/pubmed)”.(A) Cumulative number of publications relating to mimivirus over time. The subject was researched on Pubmed page (http://www.ncbi.nlm.nih.gov/pubmed), demonstrating the growing number of papers related to the virus since its discovery in 2003. (B) Published “mimivirus”/”giant viruses” papers per year since 2003, also according to the Pubmed website.