Genomes of endogenous and exogenous avian retroviruses

Coffin, John M.; Tsichlis, Philip N.; Conklin, Kathleen F.; Senior, Alayne; Robinson, Harriet L.

doi:10.1016/0042-6822(83)90461-0

Cited by 41 publications

(36 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Alternatively, PERV-A/C recombinants might be generated de novo. Mechanisms for production of PERV-A/C in vivo might include recombination between two endogenous PERV loci that are independently replication defective (3,4), recombination of a replication-competent endogenous virus with a defective endogenous locus, or the recombination of defective endogenous loci with replication-competent exogenous PERV. Support for the latter mechanism can be taken from analogy to the formation of mink cell focus-forming viruses in mice (7) as well as from the exogenous B subgroup of feline leukemia virus (FeLV-B) (1,30,32).…”

Section: Discussionmentioning

confidence: 99%

Identification of Exogenous Forms of Human-Tropic Porcine Endogenous Retrovirus in Miniature Swine

Wood¹,

Quinn²,

Suling³

et al. 2004

J Virol

130

149

View full text Add to dashboard Cite

show abstract

Section: Discussionmentioning

confidence: 99%

Identification of Exogenous Forms of Human-Tropic Porcine Endogenous Retrovirus in Miniature Swine

Wood¹,

Quinn²,

Suling³

et al. 2004

J Virol

130

149

View full text Add to dashboard Cite

show abstract

“…In contrast to Mov proviruses, some of the naturally occurring avian endogenous viruses (evs) are active in their inherited chromosomal location (2, 21). We were therefore interested in the relationship between provirus expression and the structure and activity of virus preintegration sites in this system.The avian endogenous viruses are highly related and stable genetic elements that were introduced into the germ line of chickens during evolution (1,7,24,25,33). Of the three viruses analyzed in this report, ev-1 and ev-2 are normally inactive in their inherited locations (producing less than 1 copy of stable RNA per cell; 2, 21), while ev-3 is active (producing 50 to 100 copies of stable mRNAs per cell; 2, 21).…”

mentioning

confidence: 99%

Varied interactions between proviruses and adjacent host chromatin.

Conklin¹,

Groudine²

1986

Mol. Cell. Biol.

View full text Add to dashboard Cite

Retroviruses integrated at unique locations in the host genome can be expressed at different levels. We have analyzed the preintegration sites of three transcriptionally competent avian endogenous proviruses (evs) to determine whether the various levels of provirus expression correlate with their location in active or inactive regions of chromatin. Our results show that in three of four cell types, the chromatin conformation (as defined by relative nuclease sensitivity) of virus preintegration sites correlates with the level of expression of the resident provirus in ev+ cells: two inactive proviruses (ev-1 and ev-2) reside in nuclease-resistant chromatin domains and one active provirus (ev-3) resides in a nuclease-sensitive domain. Nuclear runoff transcription assays reveal that the preintegration sites of the active and inactive viruses are not transcribed. However, in erythrocytes of 15-day-old chicken embryos (15d RBCs), the structure and activity of the ev-3 provirus is independent of the conformation of its preintegration site. In this cell type, the ev-3 preintegration site is organized in a nuclease-resistant conformation, while the ev-3 provirus is in a nuclease-sensitive conformation and is transcribed. In addition, the nuclease sensitivity of host sequences adjacent to ev-3 is altered in ev-3+ 15dRBCs relative to that found in 15d RBCs that lack ev-3. These data suggest that the relationship between preintegration site structure and retrovirus expression is more complex than previously described.Avian and murine retroviruses can be expressed at different levels after integration into the host cell genome (2,14,21,26,29). In some cases, this variation is not due to genetic differences between the proviruses but instead is dependent on their site of integration (26,29). Analyses of two mouse mammary tumor virus proviruses acquired by exogenous infection in cultured cells indicated that the differential activity of these proviruses is dependent on their location in nuclease-sensitive or nuclease-resistant regions of the host cell genorne (14). An analogous relationship is not evident, however, for murine viruses introduced into the mouse germ line (Mov proviruses;27,28). In the latter case, inherited proviruses are inactive, even when located in transcriptionally active regions of chromatin (4,20). In contrast to Mov proviruses, some of the naturally occurring avian endogenous viruses (evs) are active in their inherited chromosomal location (2, 21). We were therefore interested in the relationship between provirus expression and the structure and activity of virus preintegration sites in this system.The avian endogenous viruses are highly related and stable genetic elements that were introduced into the germ line of chickens during evolution (1,7,24,25,33). Of the three viruses analyzed in this report, ev-1 and ev-2 are normally inactive in their inherited locations (producing less than 1 copy of stable RNA per cell; 2, 21), while ev-3 is active (producing 50 to 100 copies of stable mRNAs per cell; 2, 21...

show abstract

“…The identification of ev-1 RNA in all three vaccines and of an additional RNA with an intact pol sequence, likely of ev-12 origin, in one vaccine further supports these findings. While both loci are known to express virus particles, only virions derived from ev-12 are infectious, since those expressed from ev-1 have a truncated RT-␤ and integrase (7,17). The detection of ev-1 and ev-12 in the YF vaccines demonstrates that both defective and nondefective ev loci can contribute to the ALV-E present in YF vaccines.…”

Section: Discussionmentioning

confidence: 98%

“…At least 22 different ev loci, designated ev-1 to ev-22, have been identified in White Leghorn chickens (21). ev loci are grouped on the basis of the viral phenotypes they confer (7,21). These phenotypes range from structurally and enzymatically complete infectious particles (e.g., ev-2, ev -11, ev-12, ev-18, and ev-21) to the absence of detectable viral protein expression (e.g., ev-4, ev-5, and ev-8) to structurally or enzymatically defective particles (e.g., ev-1, ev-7, and ev-9).…”

mentioning

confidence: 99%

Identification and Characterization of Avian Retroviruses in Chicken Embryo-Derived Yellow Fever Vaccines: Investigation of Transmission to Vaccine Recipients

Hussain

Johnson

Freire

et al. 2003

J Virol

View full text Add to dashboard Cite

Yellow fever (YF) vaccines are highly efficacious in preventing mortality and morbidity in humans living in or traveling to regions of tropical Africa and South America where YF is endemic (3,20). To date, more than 400 million doses of YF vaccines have been administered (20). Currently licensed YF vaccines include the attenuated 17D strain, which is propagated in chicken embryos. Vaccine preparation typically includes inoculation of 7-to 9-day-old embryonated eggs with the vaccine strain. Infected embryos are harvested, pooled, and then homogenized. Homogenates are clarified by low-speed centrifugation, and the supernatant fluid containing the vaccine harvest is titrated and lyophilized under standardized conditions (33).Because of the risk of contamination with substrate-derived avian pathogens, regulations for vaccine manufacture require all avian embryos used for propagation of vaccine virus to be derived from a closed, specific pathogen-free (SPF) flock devoid of known avian pathogens including exogenous retroviruses of the avian leukosis virus (ALV) and the reticuloendotheliosis virus groups (32). Despite the use of SPF chicken flocks, low-level reverse transcriptase (RT) activity, an indication of retroviruses, was recently detected in YF vaccines and other chick cell-derived measles and mumps vaccines produced by several manufacturers in Europe and the United States (5,19,28). The origin of RT activity has thus far been examined in measles vaccines produced in chicken embryonic fibroblasts (CEF). These studies have shown that this RT activity was associated with particles containing RNA from endogenous avian virus (EAV) and endogenous ALV (ALV-E) (17,28,30). These findings were consistent with current vaccine manufacturing regulations that require the elimination of exogenous retroviral infections from source chickens. These manufacturing regulations do not address the presence of endogenous retroviruses because such particles have not previously been known to be associated with chick cell-derived vaccines.Both EAV and ALV-E are members of endogenous retroviral families present in the chicken germ line. Little is known about the EAV family, which is distinct from but related to the ALV family. EAV elements are present in at least 50 copies per chicken genome (23). The majority of EAV loci remain uncharacterized, and the nucleotide sequences of full-length EAV genomes are not available. Partial EAV sequences show numerous frameshift mutations or sizable deletions in the env region (6).

show abstract

Genomes of endogenous and exogenous avian retroviruses

Cited by 41 publications

References 52 publications

Identification of Exogenous Forms of Human-Tropic Porcine Endogenous Retrovirus in Miniature Swine

Identification of Exogenous Forms of Human-Tropic Porcine Endogenous Retrovirus in Miniature Swine

Varied interactions between proviruses and adjacent host chromatin.

Identification and Characterization of Avian Retroviruses in Chicken Embryo-Derived Yellow Fever Vaccines: Investigation of Transmission to Vaccine Recipients

Contact Info

Product

Resources

About