John N. Simons

Prevalence of TT virus infection in US blood donors and populations at risk for acquiring parenterally transmitted viruses.

Two overlapping sets of TT virus (TTV)-specific polymerase chain reaction primers were used to test for presence of TTV, which was found in approximately 10% of US volunteer blood donors, 13% of commercial blood donors, and 17% of intravenous drug abusers. The rate of TTV infection among US non-A, non-B, non-C, non-D, non-E hepatitis patients was only 2%. Among commercial blood donors and intravenous drug abusers, only 1%-3% of the TTV-positive individuals were coinfected with GB virus C (GBV-C), a parenterally transmitted virus. This suggests that GBV-C and TTV may have different routes of transmission. Comparison of the sensitivities of 2 TTV polymerase chain reaction (PCR) primer sets showed that the majority of samples were detected with only 1 of the 2 sets. Therefore, previous studies in which only a single PCR primer pair was used may have significantly underestimated the true prevalence of TTV.

Consensus oligonucleotide primers for the detection of GB virus C in human cryptogenic hepatitis

Recently, sequences from a putative member of the Flaviviridae, GB virus C (GBV-C), were isolated from the serum of patients with cryptogenic hepatitis. These sequences were 83-99% identical at the nucleotide level. Because of the divergence between these GBV-C isolates, it is likely that the PCR-based detection assay yields false negatives, underestimating dramatically the true prevalence of GBV-C in human hepatitis. We report the design of a GBV-C consensus oligonucleotide primer pair that is superior to those originally described. These primers identify GBV-C sequences in cases of cryptogenic hepatitis, allowing a better estimation of the prevalence of this virus in human populations.

Isolation of a GB virus-related genome from a chimpanzee

Recently, two new flaviviruses, GB virus A (GBV‐A) and GB virus B (GBV‐B), were identified in the plasma of a tamarin infected with the hepatitis GB agent. A third virus, GB virus C (GBV‐C), was subsequently identified in humans. In the current study, representational difference analysis (RDA) was used to search for a new virus in the serum of a chimpanzee that developed acute resolving hepatitis following inoculation with a pool of chimpanzee plasma. The plasma pool originated from serial passages of a human sample containing virus‐like particles. Numerous cDNA clones were obtained that exhibited 62–80% identity with GBV‐C. With the exception of the extreme 5′ and 3′ ends, the complete viral genome was sequenced, revealing a single large open reading frame encoding a 2833 amino acid polyprotein that contains two envelope proteins, two proteases, a helicase, and an RNA‐dependent RNA polymerase. Phylogenetic analysis of the new virus indicates that it is closely related to GBV‐C, yet still sufficiently divergent as to be placed in a separate group, tentatively labeled GB virus Ctroglodytes (GBV‐Ctro). Numerous human samples were screened by reverse transcriptase‐polymerase chain reaction (RT‐PCR), but GBV‐Ctro sequence was not detected. However, a second chimpanzee inoculated with the same plasma pool was shown to develop a GBV‐Ctro infection. Although isolated from an Old World primate with hepatitis, the primary host of GBV‐Ctro and any association with disease remains to be determined. J. Med. Virol. 56:44–51, 1998.

Variation in efficiency of aphid transmission of southern cucumber mosaic virus and potato virus Y in pepper.

Abstract Considerable differences in the ability of several clones of the cotton aphid, Aphis gossypii Glover, to transmit southern cucumber mosaic virus (SCMV) in pepper were demonstrated. The same differences were not demonstrable when these clones were used as vectors of potato virus Y (PVY) in pepper. Each clone and species of aphid tested proved to have a definite and constant level of efficiency for each virus tested. Attempts were made to change the vector-efficiency of some of the aphid clones. Changing the species of aphid host plant only slightly affected the efficiency of transmission. Transmission was not consistently affected by changing the species of plants providing virus inoculum. Selection of subclones from aphids that had histories as vectors did not change the efficiency of a clone. Selection of inoculum plants that had histories of transmission by the same clone of aphid also failed to change the vector efficiency of a given clone of aphid.

Transmission of pseudo-curly top virus in Florida by a treehopper

Abstract A treehopper, Micrutalis sp., has been shown to be a vector of the virus causing pseudo-curly top. This is believed to be the first report of this family of insects (Membracidae) transmitting a virus disease. Pseudo-curly top of tomato has been found to occur throughout south Florida. Nightshade, Solanum gracile (Link), is a weed host of the virus and of the vector.