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A virus given the name ground squirrel hepatitis virus (or GSHV), with many of the unique characteristics of human hepatitis B virus (HBV), has been found in Beechey ground squirrels in northern California. (2), the viral DNA (3), a DNA polymerase activity (4, 5), and probably hepatitis B e antigen (HBeAg) in a cryptic form (6). No crossreaction has been found between HBsAg and a large number of antigens of other viruses that have been tested (7). HBcAg and HBeAg were also considered unique to HBV.The viral DNA is circular and has a contour length consistent with that of double-stranded DNA of approximately 3200 base pairs (bp) (3). However, as isolated from virions, the DNA was not completely double stranded. Between 15% and 50% of the length of different molecules was single stranded (8-10). A DNA polymerase activity in the viral core catalyzed a repair reaction that converted the DNA to fully double-stranded circular molecules of approximately 3200 bp (8-10).Persistent infection with HBV is common, continues for years (11), and is accompanied by continuous circulation in the blood of high concentrations of incomplete viral forms consisting of small spherical HBsAg particles 16-25 nm in diameter and long filamentous HBsAg containing structures approximately 22 nm in width and up to 500 nm in length (1, 2, 12) as well as complete virions usually in much lower concentrations. Persistent infection in humans is associated with chronic hepatitis (13) Gerin, personal communication).Here we describe a virus found in ground squirrels in one region of northern California that is similar to HBV and WHV and may represent a third member of this class of viruses.MATERIALS AND METHODS Sera. Sera were obtained from all animals by cardiac puncture. Apparently healthy Beechey ground squirrels (Spermophilus beecheyi) were obtained from Point Lobos, CA (location A), a region adjacent to the Stanford University campus (location B), and a region near Santa Barbara, CA (location C). Sera containing high concentrations of HBV were obtained by plasmapheresis of a persistently infected patient after informed consent was obtained.Assay for Virion DNA Polymerase Activity. Particle-associated DNA polymerase levels in sera were determined by a modification of the method previously described (19). Serum samples were centrifuged in an Eppendorf centrifuge at 10,000 rpm for 10 min to remove precipitated protein and other debris; 200 Ml of each supernatant was layered over 500 ,ul of 30% sucrose (wt/vol) containing 10 mM Tris-HCI, 0.1 M NaCI, 5 mM EDTA, 0.1% 2-mercaptoethanol, and 1 mg of centrifuged bovine serum albumin per ml in 1-ml polycarbonate tubes and particles were pelleted in a Spinco type 25 rotor for 16 hr at 25,000 rpm and 4°C. Supernatants were removed by suction and discarded, and inner walls of the tubes were wiped dry. The pellets were resuspended in 50 ,l of 1.5% Nonidet P-40/0.1% 2-mercaptoethanol/10 mM Tris-HCI, pH 7.5/0.1 M NaCl. Then 25 ,ul of 0.2 M Tris-HCl (pH 7.5), 80 The publication costs of this article...

Cool vapors and aerosols produced by several common surgical power instruments and hot smoke plumes generated with electrocautery on known HIV-1 innoculated blood were gently bubbled through sterile viral culture media. Tissue culture cells were then added and cell infection was detected by the appearance of HIV-1 P-24 core antigen assayed by ELISA in the culture medium. HIV-1 was cultured from cool aerosols and vapors generated by a 30,000 RPM spinning router tip, an instrument similar to the Midas Rex and the Stryker oscillating bone saw. No infectious HIV-1 was detected in aerosols generated by a Valley Lab electrocautery or with a manual wound irrigation syringe known as a Travenol Uromatic irrigator. We have demonstrated that HIV-1 can remain viable in cool aerosols generated by certain surgical power tools and this raises the possibility of HIV transmission to medical personnel exposed to aerosols similarly generated during the care of HIV infected patients. Further work is required to determine whether such a risk exists but caution should be exercised by those exposed to aerosols generated during procedures on HIV-1 infected patients.

DNA polymerase activity was detected in each of eight preparations of concentrated human hepatitis B antigen (HBAg) rich in Dane particles prepared by high-speed centrifugation of antigen-positive human plasma and in none of seven control preparations prepared in the same way from HBAg-negative plasma. The incorporation of 3 H-thymidine-methyl-5′-triphosphate into DNA was dependent on four deoxyribonucleoside triphosphates and MgCl 2 . Treatment of the concentrated HBAg preparations with the nonionic detergent Nonidet P-40 (NP40) more than doubled the enzyme activity. Fractionation of the concentrated HBAg preparation in sucrose density gradients after treatment with NP40 revealed that the enzyme activity appeared within the density range of Dane core antigen but at a slightly higher density than the average for core antigen. The only particles observed by electron microscopy in this region of the gradient were typical 28-nm cores, suggesting that the DNA polymerase activity was associated with a subpopulation of cores. No DNA polymerase activity was found in purified 20-nm HBAg particles. The DNA product of the reaction remained associated with the 110 S core and was not susceptible to DNase digestion when associated with the core. Inhibition of the reaction by actinomycin D and daunomycin suggested that the reaction was dependent on a DNA template associated with the core.

Four patients with chronic hepatitis B infection and chronic active hepatitis were treated with human leukocyte interferon. Three of them had consistently elevated levels of circulating Dane-particle markers, including Dane-particle-associated DNA polymerase activity, hepatitis B core antigen and Dane-particle-associated DNA. Parenteral interferon administration at a dosage between 6.0 X 10(3) and 17 X 10(4) U per kilogram per day was associated with a rapid and reproducible fall in all Dane-particle markers in the three patients. The suppressive effect was transient when the interferon was given for 10 days or less but appeared to be more permanent when administration was prolonged for a month or more. In addition, long-term interferon therapy was associated with a marked fall in hepatitis B surface antigen in two of three patients and a disappearance of e antigen in two of two patients. Interferon may be useful in limiting carrier infectivity or eradicating chronic infection.

Hepatitis B virus (HBV), although classified as a double-stranded DNA virus, has been shown recently to replicate by reverse transcription of an RNA intermediate. Also, the putative viral polymerase has been found to share amino acid homology with reverse transcriptase of retroviruses. Using computer-assisted DNA and protein sequence analyses, we examined the genomes of 13 hepadnavirus isolates (nine human, two duck, one woodchuck, and one ground squirrel) and found that other conserved regions of the hepadnavirus genome share homology to corresponding regions of the genomes of type C retroviruses and retrovirus-like endogenous human DNA elements. Specifically, the most highly conserved sequence of the HBV genome, positioned at or near the initiation site for rirst-strand HBV DNA synthesis, is homologous over 67 nucleotides to the U5 region, a comparable region in retrovirus long terminal repeats. However, experiments using virus-infected liver revealed a novel mode of DNA replication through an RNA intermediate by reverse transcription, a process similar to retrovirus replication (1). This work was soon followed by the discovery of amino acid sequence homology between the putative polymerase protein of HBV and a conserved region of the reverse transcriptase of retroviruses (2, 3) and raised the question of the genetic relatedness of the hepadnavirus and retrovirus families.The small size of the HBV genome [-3200 base pairs (bp)] makes it especially amenable for nucleotide sequence and biological analysis. At the time of this writing, the nucleotide sequence of 13 viral genomes has been published: nine HBV isolates of surface antigen subtypes adr (4-7), adw (5, 8), ayw (9, 10), and adyw (11), two isolates ofDHBV (12, 13), and one isolate each of GSHV (14) and WHV (15). Analysis of the protein-coding capacity of the virus shows that only one viral DNA strand, the minus or long strand, possesses significant protein-coding capability. Four long open reading frames (ORFs) have been assigned to genes specifying the viral core (sometimes including a short precore region), surface (always including a long presurface region), and putative polymerase protein as well as an unknown protein X. All genomes are structurally colinear, with the four ORFs approximately the same length in all isolates examined with the exception of the deletion of the carboxyl-terminal region of the X ORF in DHBV. Of the hepadnavirus proteins encoded by the four viral ORFs, the core, which is the nucleocapsid protein, is the most highly conserved. We used computer-assisted DNA and protein sequence analyses to compare the genomes of hepadnaviruses and retroviruses and report here that these virus families share previously unreported homology between several well-conserved regions of their genomes, suggesting their common evolutionary origin. Retroviral U5-like sequence in terminal repeats of the linear HBV RNA genome In our DNA sequence analysis of hepadnavirus genomes, we found that the region located between the carboxyl-terminal end of...

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