The viral nature of Toddia França, 1912

Abstract

Toddia França, 1912 under the light microscope occurs as inclusion corpuscles in the cytoplasm of erythrocytes of cold-blooded vertebrates sometimes accompanied by crystalloid bodies. Its position among the protozoans or the viruses has been discussed by some authors, but remained unclear. To elucidate this problem we studied Toddia from a Brazilian frog (Leptodactylus ocellatus) by electron microscopy. In the cytoplasm of the infected cells we found no protozoan, but rather virus-like particles often hexagonal in outline, averaging 195 nm excluding their two involving membranes, and presenting a central area of variable electron density. Particles at different stages of development were generally found around or on area lighter density than the cytoplasm. which resembled a virus synthesis site. At high magnification, the nuclear or cytoplasmic crystals allied to Toddia resembled the crystalline lattice of the inclusion bodies associated with the polyhedrosis viruses and poxviruses from insects, of the capsules of granulosis viruses and of other protein crystals in ultrathin sections. Cytochemical tests in Toddia corpuscles displayed exclusively the presence of deoxyribonucleic acid. These findings indicate that Toddia is not a protozoan and demonstrate that it is in all probability a viral inclusion corpuscle. Taking into account the nucleic acid type found in its structure (DNA) and the hexagonal shape usually shown in ultrathin sections by its component particles, which have a cytoplasmic site of synthesis and assembly, we tentatively relate Toddia with the so-called "Icosahedral Cytoplasmic Deoxyriboviruses". We believe that the present paper gives the first report of virus-like particles in L. ocellatus.

Ultrastructure of erythrocytic virus of the South African anuran Ptychadena anchietae

“…These probably represent endoplasmic reticulum cisternae enveloping the capsid, as suggested by Sousa & Weigl (1976). The association of the membranes with the nuclear envelope was evident in lysing cells and supports this hypothesis.…”

“…The virus observed in the South African frog was morphologically similar to the erythrocytic virus found by Sousa & Weigl (1976) in a Brazilian frog, but was about two-thirds of the size of the erythrocytic viruses described by Bernard et al (1968) and Desser & Barta (1984) from North American frogs and the virus of Bufo marinus from Costa Rica described by Speare et al (1991). Size differences have been related to generic differences in iridoviruses of insects (Willis 1990).…”

“…No clinico-pathological changes except for cytological damage as direct consequence of viral activity in the infected cell were so far demonstrated in any of the reported erythrocytic viral infections of frogs (Bernard 1968, Sousa 1976, Desser 1984, Speare 1991, Paperna & Alves d e Matos 1993. This contrasts with the extreme anemia characteristic of erythrocytic viral infections in saurian reptiles (Paperna & Alves de Matos 1993).…”

“…It is characterized at the light microscopic level by the presence of a cytoplasmic purple corpuscle representing the viral factory or virosome, and a crystalloid inclusion of unknown significance (Sousa & Weigl 1976, Paperna & Alves d e Matos 1993). Electron microscopic (EM) studies have shown these infections to be caused by indovirus-like viruses (Stehbens & Johnston 1966, Sousa & Weigl 1976, Speare et al 1991, Alves de Matos & Paperna 1993.…”

Iridovirus-Like Viruses in Erythrocytes of Lacertids from Portugal

“…morphologically similar to the icosahedral nucleo-cytoplasmic large DNA vi-ruses~NCLDVs; Iyer et al, 2001!. Cytoplasmic inclusion-producing NCLDV-like viruses also occur in fish and amphibian eryth-rocytes~Johnston, 1975;Sousa & Weigl, 1976;Walker & Sherburne, 1977;Gruya-Gray et al, 1989;Alves de Matos & Paperna, 1993b, Glenn & Emmenegger, 2012!, as well as in other reptiles, such as the peninsula ribbon snake Thamnophis sauritus sackenii~Wellehan et al, 2008!. Cytoplasmic inclusion-producing NCLDV-like viruses also occur in fish and amphibian eryth-rocytes~Johnston, 1975;Sousa & Weigl, 1976;Walker & Sherburne, 1977;Gruya-Gray et al, 1989;Alves de Matos & Paperna, 1993b, Glenn & Emmenegger, 2012!, as well as in other reptiles, such as the peninsula ribbon snake Thamnophis sauritus sackenii~Wellehan et al, 2008!.…”