Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving virus or bacteriophage
Reexamination Certificate
1999-02-05
2002-05-28
Wortman, Donna (Department: 1643)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving virus or bacteriophage
C435S006120, C435S091200, C536S024300, C536S024320, C536S024330
Reexamination Certificate
active
06395472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the TT virus and to methods of use thereof. More particularly, the present invention relates to nucleic acid primers useful for detection of the TT virus, use of the TT virus as a vector, use of the TT virus for human and veterinary diagnostics, and use of the TT virus for testing prior to transplantation or xenotransplantation. Additionally, the present invention includes use of TT virus sequence diversity as a means of monitoring viral transmission between individuals.
2. Background of the Invention
Recently, a novel human DNA virus was isolated from the serum of a Japanese patient (initials T.T.) with cryptogenic hepatitis (Nishizawa et al.,
Biochem Biophys Res Commun
241:92-97 (1997)). Utilizing PCR, TT virus (TTV) was detected in sera from three of five patients with non-A to GBV-C hepatitis. Subsequently, the nearly complete nucleotide sequence of the TTV genome, encompassing 3739 bases, and a more sensitive PCR assay for the detection of virus in serum were reported (Okamoto et al.,
Hepatol. Res
. 10:1-16 (1998)). In addition, based upon sensitivity to single-strand but not double-strand-specific endonucleases, the virus appeared to possess a single-stranded DNA genome. Data presented regarding the size of the genome, its single-strandedness, and resistance to detergents, suggested that TTV was similar to the parvoviruses (Okamoto et al.,
Hepatol. Res
. 10:1-16 (1998)). However, the buoyant density in CsCl (1.31-1.32 g/ml) was lower than that reported for the parvoviruses.
Several PCR studies have been performed to assess the prevalence of this virus in various populations. One assay described by Okamoto et al. (Okamoto et al.,
Hepatol. Res
. 10:1-16 (1998)) detected TTV DNA in hemophiliacs (68%), intravenous drug abusers (40%), patients on maintenance hemodialysis (46%) and those with cryptogenic hepatitis and/or chronic liver disease (46-48%). Further, TTV infection in Japanese normal blood donors was found to be 12%. The rates of TTV infection in the United Kingdom have recently been reported at 1.9% (19 of 1000 blood donors) (Simmonds et al.,
The Lancet
352:191-194 (1998)) using two distinct primers sets and 10% (3 of 30 healthy controls) (Naoumov et al.,
The Lancet
352:195-197 (1998)) using the PCR strategy of Okamoto (Okamoto et al.,
Hepatol. Res
. 10:1-16 (1998)). Both of these reports identified TTV DNA in patients at risk for acquiring parenterally transmitted viruses (27-39%) and/or in patients with hepatitis (19-22%). These studies suggest that TTV can be transmitted via blood or blood products and may also be associated with some cases of cryptogenic hepatitis.
The preliminary epidemiological studies of TTV described above utilized several different first generation PCR primer pairs. Desai et al. (Desai et al.,
J. Infect. Dis
. in press:(1999)) compared the sensitivities of two first generation TTV PCR primers sets and demonstrated that the majority of TTV-positive samples were detected by only one of the two primer sets. Thus, previous reports that utilized a single PCR primer pair may have significantly underestimated the true prevalence of the virus. Second generation PCR assays for TTV appear to confirm the underestimation of TTV prevalence. Specifically, a PCR assay described by Takahashi et al (Takahashi et al.,
Hepatol. Res
. 12:233-239 (1998)) that was 10 to 100 times more sensitive than the assay described by Okamoto et al (Okamoto et al.,
Hepatol. Res
. 10:1-16 (1998)) found TTV present in 92 of 100 healthy individuals who visited a Japanese hospital for routine health screening. Therefore, TTV prevalence in the normal Japanese population appears to be much higher than the 12% originally reported.
The high rate of TTV carriers in the normal population may not be compatible with an exclusive parenteral transmission route. A possible fecal-oral transmission route was suggested by a study that demonstrated the presence of TTV in the feces of infected humans (Okamoto et al.,
J. of Med. Virol
. 56:128-132 (1998)). Additional non-parenteral routes of infection may explain the high prevalence of TTV infection in healthy individuals. Finally, based upon limited prevalence studies and the high rates of TTV in the normal populations (Charlton et al.,
Hepatology
28:839-842 (1998; Naoumov et al.,
The Lancet
352:195-197 (1998; Simmonds et al.,
The Lancet
352:191-194 (1998)), the association between TTV infection and human hepatitis is questionable.
The detection of TTV in test samples can be enhanced by the use of DNA amplification assays that utilize DNA oligomers as primers, since the amount of DNA target nucleotides present in a test sample may be in minute amounts. Methods for amplifying and detecting a target nucleic acid sequence that may be present in a test sample are well-known in the art. Such methods include the polymerase chain reaction (PCR) described in U.S. Pat. Nos. 4,683,195 and 4,683,202, the ligase chain reaction (LCR) described in European Patent Application EP-A-320 308, gap LCR (GLCR) described in European Patent Application EP-A-439 182 and U.S. Pat. No. 5,427,930 which is incorporated herein by reference, multiplex LCR described in International Patent Application No. WO 93/20227, and the like. These methods have found widespread application in the medical diagnostic field as well as in the fields of genetics, molecular biology and biochemistry.
It would be advantageous to provide DNA oligomer primers derived from TTV and diagnostics, and test kits which utilize these primers. Such primers could greatly enhance the ability to more accurately detect TTV infections, and track the virus' route of transmission.
In addition to the advantages of viral detection, viruses have the potential to serve as vectors for purposes such as expression of cloned genes in culture and development of treatments for disease through gene therapy. Viruses that have been developed into vectors include those with DNA genomes such as adeno-associated virus (see, e.g., Muzyczka, N.,
Current Topics in Microbiol. and Immunol
. 158:97-129 (1992) and Kotin, R. M., Human Gene Therapy 5:793-801 (1994)), adenovirus (see, e.g., Haj-Ahmad et al.,
J. Virol
. 57:264-274 (1986) and Berkner, K. L.,
BioTechniques
6:619-629 (1988)), herpes virus (see, e.g., Breakefield et al.,
New Biol
. 3:203-218 (1991) and Wolfe et al.,
Nature Genetics
1:379-384 (1992)) and papovavirus (see, e.g., Grossi et al.,
Arch. Virol
. 102:275-283 (1988) and Milanesi et al.,
Mol Cell. Biol
. 4:1551-1560 (1984)), and those with RNA genomes such as modified retroviruses (see, e.g., Gazit et al.,
Journal of Virology
60:19-28 (1986) and Palmer et al.,
Proc. Natl. Acad. Sci. USA
84:1055-1059 (1987)).
DNA viruses with small genomes, such as TTV, typically encode relatively few proteins and rely on the host cell to provide most replication and expression functions, thereby reducing the complexity of their interaction with the host cell. Furthermore, TTV infection does not appear to be associated with any disease, as is evidenced by its presence in nearly 100% of some human, normal populations. Its high prevalence also suggests that infection occurs readily, and that re-infection is common, as is implied by co-infections with multiple strains. All these traits are desirable in a gene therapy vector, which should be uncomplicated, non-pathogenic, easily delivered and have the potential for multiple treatments, or for being maintained over extended periods of time.
Comparison of numerous TTV genomes has demonstrated a high sequence diversity and an apparent lack of geographic localization. This implies either a high mutation rate, due to a low fidelity replicase, or an ancient virus family that has undergone extensive evolutionary drift. Researchers of HIV have used its sequence diversity as a basis for epidemiological studies and to demonstrate specific transmission of a viral infection from one individual to another. Likewise, the diversity of TTV may help establish the primary r
Birkenmeyer Larry
Chalmers Michelle
Desai Suresh
Erker James
Leary Thomas P.
Abbott Laboratories
Becker Cheryl L.
Wortman Donna
Zeman Robert A.
LandOfFree
Methods of utilizing the TT virus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods of utilizing the TT virus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods of utilizing the TT virus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2861994