Incidence and clinical presentation of posttransfusion TT virus infection in prospectively followed transfusion recipients: emphasis on its relevance to hepatitis

Torque teno virus in liver diseases: On the way towards unity of view

The review presents the data accumulated for more than 20 years of research of torque teno virus (TTV). Its molecular genetic structure, immunobiology, epidemiology, diagnostic methods, possible replication sites, and pathogenicity factors are described. TTV is a virus that is frequently detectable in patients with different viral hepatitides, in cases of hepatitis without an obvious viral agent, as well as in a healthy population. There is evidence suggesting that biochemical and histological changes occur in liver tissue and bile duct epithelium in TTV monoinfection. There are sufficient histological signs of liver damage, which confirm that the virus can undergo a replicative cycle in hepatocytes. Along with this, cytological hybridization in TTV-infected cells has shown no substantial cytopathic (cell-damaging) effects that are characteristic of pathogenic hepatotropic viruses. Studying TTV has led to the evolution of views on its role in the development of human pathology. The first ideas about the hepatotropism of the virus were gradually reformed as new data became available on the prevalence of the virus and its co-infection with other viruses, including the viruses of the known types of hepatitides. The high prevalence of TTV in the human population indicates its persistence in the body as a virome and a non-pathogenic virus. It has recently been proposed that the level of TTV DNA in the blood of patients undergoing organ transplantation should be used as an endogenous marker of the body’s immune status. The available data show the polytropism of the virus and deny the fact that TTV can be assigned exclusively to hepatitis viruses. Fortunately, the rare detection of the damaging effect of TTV on hepatic and bile duct epithelial cells may be indirect evidence of its conditionally pathogenic properties. The ubiquity of the virus and the variability of its existence in humans cannot put an end to its study.

Hepatitis viruses (other than hepatitis B and C viruses) as causes of hepatocellular carcinoma: an update

Chronic hepatitis B and C virus infections are universally accepted as causes of hepatocellular carcinoma in humans. Hepatitis A and E viruses cause only acute self-limiting infections of the liver. Of the remaining hepatitis viruses - Delta hepatitis, hepatitis G (GB-C), TT and SEN - all have at some time been incriminated as causes of hepatocellular carcinoma. Delta hepatitis virus requires helper functions from hepatitis B virus to become invasive. Chronic Delta/hepatitis B viral co-infection runs a more severe course than that resulting from chronic hepatitis B virus infection alone, with progression to cirrhosis being more likely and more rapid. A substantial majority of the early studies did not find an increased incidence of hepatocellular carcinoma in co-infected individuals. But more recently, an increased incidence of the tumour has been recorded more often than no increase. Further studies are needed to draw a firm conclusion with regard to the hepatocarcinogenic effect of dual Delta/hepatitis B virus co-infection. With one exception, no published study (of 13) has incriminated chronic infection with hepatitis G virus as a cause of hepatocellular carcinoma. The dissenting study, published in 1999, was the only one performed in the United States. Fewer studies of the hepatocarcinogenic effect of TT virus have been performed. Apart from one study, published in 1999, no convincing evidence is available that supports a causal role for TT virus in hepatocarcinogenesis. The exception was in Japanese patients with high hepatitis C viral loads but independent of chronic hepatitis C virus infection. No evidence has been produced to indicate that SEN virus causes hepatocellular carcinoma.

Evaluation of induction of porcine dermatitis and nephropathy syndrome in gnotobiotic pigs with negative results for porcine circovirus type 2

OBJECTIVE

To determine whether porcine dermatitis and nephropathy syndrome (PDNS) could be experimentally induced in gnotobiotic swine.

SAMPLE POPULATION

Plasma samples from 27 sows and 20 conventional weaned piglets were obtained, and 30 gnotobiotic pigs were used in experiments.

PROCEDURES

3 experiments were conducted. Groups of 3-day-old gnotobiotic pigs were inoculated with pooled plasma samples obtained from healthy feeder pigs in a herd that was in the initial phases of an outbreak of respiratory disease; gross and histologic lesions of PDNS were detected in the inoculated pigs. In a second experiment, 2- and 3-day-old gnotobiotic pigs were inoculated with porcine reproductive respiratory syndrome virus (PRRSV) and with PRRSV-negative tissue homogenate containing genogroup 1 torque teno virus (g1-TTV). Lesions of PDNS were detected.

RESULTS

Pigs inoculated with pooled plasma or the combination of tissue-culture-origin PRRSV and g1-TTV tissue homogenate developed systemic hemostatic defects, bilaterally symmetric cutaneous hemorrhages, generalized edema, icterus, bilaterally symmetric renal cortical hemorrhage, dermal vasculitis with hemorrhage, and interstitial pneumonia consistent with a clinical and pathologic diagnosis of PDNS. The PRRSV RNAs and g1-TTV DNAs were detected in plasma; all pigs seroconverted to PRRSV, and all had negative results for porcine circovirus type 2 when tested by use of PCR assays.

CONCLUSIONS AND CLINICAL RELEVANCE

These data suggested that PDNS is a manifestation of disseminated intravascular coagulation in swine. For the experimental conditions reported here, combined infection with g1-TTV and PRRSV was implicated in the genesis of these lesions.

Anemia, allogenic blood transfusion, and immunomodulation in the critically ill

Anemia and allogenic RBC transfusions are exceedingly common among critically ill patients. Multiple pathologic mechanisms contribute to the genesis of anemia in these patients. Emerging risks associated with allogenic RBC transfusions including the transmission of newer infectious agents and immune modulation predisposing the patient to infections requires reevaluation of current transfusion strategies. Recent data have suggested that a restrictive transfusion practice is associated with reduced morbidity and mortality during critical illness, with the possible exception of acute coronary syndromes. In this article, we review the immune-modulatory role of allogenic RBC transfusions in critically ill patients.

Transfusion-transmitted HBV infection in an endemic area: the necessity of more sensitive screening for HBV carriers

BACKGROUND

By NAT, HBV DNA is occasionally detectable in blood donors with past HBV infection but negative for HBsAg. Whether or not these donors can cause transfusion-transmitted HBV infections is uncertain.

STUDY DESIGN AND METHODS

To determine whether or not donors with past HBV infection but negative for HbsAg can cause HBV transfusion-transmitted infections, recipients followed for blood transfusion in a university medical center in Taiwan were studied. HBV DNA and serologic markers were tested in donors and recipients.

RESULTS

Of 1,038 enrolled recipients, 910 completed the 6-month post-transfusion follow-up visit. Of these, only 39 patients (4.3%) tested negative on the pretransfusion sample for HBsAg, anti-HBs, anti-HBc, and HBV DNA by PCR. These 39 HBV-naive recipients had been transfused with blood from 147 donations for which stored samples were available for HBV DNA testing by PCR; 11 of these HBsAg-negative samples tested positive for HBV DNA and anti-HBc. Two of the 11 patients who received the HBV-DNA-positive donations (18%) became positive for HBV DNA, and one seroconverted to anti-HBc and finally to anti-HBs, with a mild transient elevation of serum ALT activities. Based on the one confirmed case of HBV transmission, a projection was made that approximately 200 post-transfusion HBV infections could occur in one million units of transfused blood in Taiwan.

CONCLUSIONS

In HBV-endemic areas like Taiwan, where blood donors are screened for HBsAg only, the risk of transfusion-transmitted HBV appears to be substantial. Implementation of NAT for blood screening in these settings warrants consideration.

Nucleic acid testing for emerging viral infections

The development of new technologies leads to the discovery of new viruses. For each of these new infectious agents, relevance to transfusion, including transmissibility by transfusion, pathogenicity, prevalence in blood donors, persistence and the availability of screening assays needs to be assessed. Since 1995, one virus and a new family of viruses have been identified. GB virus-C/hepatitis G virus (GBV-C/HGV), a flavi virus with some homology with and epidemiological features of HCV, is not related to post-transfusion hepatitis but seems to positively interfere with human immunodeficiency virus replication. Human circoviruses include TT virus (TTV) and SEN-V. Both are highly variable, constituting a large family of distantly related viruses. They appear ubiquitous, infecting humans very early in life and are largely persistent. No clinical symptoms or pathogenicity is associated with TTV, but SEN-V might be associated with some non-A-E post-transfusion hepatitis. Parvovirus B19 has been known for many years, but its transmission to recipients of plasma derivatives despite viral inactivation raised the issue of screening plasma pools by nucleic acid testing. Most fractionators quantify B19 DNA in plasma pools to ensure a viral load of <10(4) IU mL-1.

Acute normovolaemic haemodilution in colorectal surgery

AIMS

Blood transfusions are often given to surgical patients. This study was designed to assess whether acute normovolaemic haemodilution (ANH) reduces exposure to allogeneic blood, affects clinical outcome and hospital stay, and is feasible in colorectal surgery.

METHODS

All ASA 1 and 11 patients undergoing colectomies performed between 1997 and 1999 were identified retrospectively from our colorectal cancer database to ascertain our current peri and postoperative transfusion practice. Twenty-six selected patients subsequently underwent ANH during colectomy surgery. The number of patients and units transfused were identified.

RESULTS

One hundred and twenty-three of 317 (39%) patients identified from our colorectal cancer database were transfused a total of 328 units (median 2, range 1-7). Of the 26 patients undergoing ANH, 4 (15%) were transfused a total of 13 units (median 3, range 2-5). The reduction in number of patients transfused was statistically significant (P=0.017). ANH increased anaesthetic time by a median of 19 min. There were no complications associated with ANH and the median hospital stay was 9 days (range 6-13).

CONCLUSIONS

In this pilot study of selected patients, ANH is a feasible and effective method of reducing allogeneic blood exposure in major colorectal surgery. A prospective randomised controlled trial is now urgently required.

Transfusion-transmitted virus prevalence in subjects at high risk of sexually transmitted infection in Turkey

OBJECTIVE

To assess the possible sexual transmission of virus and to identify the prevalence of TTV viremia in Turkey and its association with other hepatotropic viruses.

METHODS

Serum samples were collected from 81 subjects (74 prostitutes and seven homosexual men) at high risk of sexually transmitted infection and from 81 healthy controls (74 females and seven males). Sera of patients and controls were tested for TTV, hepatitis A virus, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus. Also, serum alanine and aspartate aminotransferases were measured.

RESULTS

The prevalence rates of TTV viremia in the risk group and control group were 86.4% and 82.7%, respectively. There was a statistical difference in mean age between TTV-infected and uninfected subjects (38.6 +/- 9.9 versus 32.2 +/- 6.1 years, respectively, P < 0.001). Prevalence rates of TTV infection in subjects with positive anti-HAV and positive anti-HBc were high when compared with subjects who were negative for these.

CONCLUSION

We suggest that TTV infection has a diverse route of transmission, and its prevalence increases with age; also, the prevalence rate of TTV is high in certain risk groups. The prevalence rates of TTV in the group at risk for sexual transmission (86.4%) and in the control group (82.7%) were among the highest ever reported in the world. Also, we suggest that TTV generally does not cause clinical disease, in spite of this high prevalence.

Clinicopathological study on TTV infection in hepatitis of unknown etiology

AIM: To investigate the state of infection, replication site, pathogenicity and clinical significance of transfusion transmitted virus (TTV) in patients with hepatitis, especially in patients of unknown etiology.

METHODS: Liver tissues taken from 136 cases of non-A non-G hepatitis were tested for TT virus antigen and nucleic acid by in situ hybridization (ISH) and nested-polymerase chain reaction (PCR). Among them, TT virus genome and its complemental strand were also detected in 24 cases of autopsy liver and extrahepatic tissues with ISH. Meanwhile, TTV DNA was detected in the sera of 187 hepatitis patients by nested-PCR. The pathological and clinical data of the cases infected with TTV only were analyzed.

RESULTS: In liver, the total positive rate of TTV DNA was 32.4% and the positive signals were located in the nuclei of hepatocytes. In serus, TTV DNA was detected in 21.4% cases of hepatitis A-G, 34.4% of non-A non-G hepatitis and 15% of healthy donors. The correspondence rate of TTV DNA detection between liver tissue with ISH and sera with PCR was 63.2% and 89.3% in the same liver tissues by ISH and by PCR, respectively. Using double-strand probes and single-strand probes designed to detect TTV genome, the correspondence rate of TTV DNA detected in liver and extrahepatic tissues was 85.7%. Using single-strand probes, TTV genome could be detected in liver and extrahepatic tissues by PCR, but its complemental strands (replication strands) could be observed only in livers. The liver function of most cases infected with TTV alone was abnormal and the liver tissues had different pathological damage such as ballooning, acidophilia degeneration, formation of apoptosis bodies and focus of necrosis, but the inflammation in the lobule and portal area was mild.

CONCLUSION: The positive rate of TTV DNA among cases of hepatitis was higher than that of donors, especially in patients with non-A non-G hepatitis, but most of them were coinfected with other hepatitis viruses. TTV can infect not only hepatocytes, but also extrahepatic tissues. However, the chief replication place may be liver. The infection of TTV may have some pathogenicity. Although the pathogenicity is comparatively weak, it can still damage the liver tissues. The lesions in acute hepatitis (AH) and chronic hepatitis (CH) are mild, but in severe hepatitis (SH), it can be very serious and cause liver function failure, therefore, we should pay more attention to TTV when studying the possible pathogens of so-called “Liver hepatitis of unknown etiology”.

Process for the preparation of pathogen-inactivated RBC concentrates by using PEN110 chemistry: preclinical studies

BACKGROUND

A pathogen-inactivation process for RBC concentrates is being developed by using PEN110 chemistry (INACTINE, V.I. Technologies). The objective of this study was to characterize the quality of RBCs prepared by using the PEN110 process and to measure the virucidal effect achieved against two viruses.

STUDY DESIGN AND METHODS

Virology and RBC studies were conducted with standard RBC units treated with 0.1-percent (vol/vol) PEN110 at 22 degrees C for 6 hours. The quality of PEN110-treated human RBCs was assessed with biochemical and phenotypic variables. The in vivo viability of PEN110-treated RBCs in baboons was studied with the double-label (51)Cr/(125)I method.

RESULTS

Decreases in infectious titer by inactivation of greater than a 5 log 50-percent tissue culture infectious doses per mL of bovine viral diarrhea virus (an enveloped RNA virus) and porcine parvovirus (a nonenveloped DNA virus) was observed. RBC hemolysis was less than 1 percent after 42 days of storage, and no changes in RBC antigens were observed. The in vivo viability of PEN110-treated baboon RBCs was unchanged from control.

CONCLUSION

The preparation of RBCs by using the PEN110 process achieved a significant viral reduction of two diverse viruses without causing adverse effects to the RBCs. The process appears to be a promising approach, thus justifying further study.

Lack of transmission of TT virus through immunoglobulins

BACKGROUND

A high prevalence of TT virus (TTV) infection has been found in patients who received blood or blood components. Viral DNA was demonstrated in commercial preparations of FVIII and F IX, but very few data have been reported on immunoglobulins. The risk of TTV infection associated with intramuscular or IV immunoglobulin administration is unclear.

STUDY DESIGN AND METHODS

The prevalence of TTV infection in a group of patients undergoing lifelong therapy because of congenital immunodeficiency has been evaluated in a long term follow-up (median, 6 years). Seventeen patients with congenital immunodeficiency receiving monthly administration of IVIG were included in the study. TTV DNA was repeatedly evaluated by PCR in serum samples from each patient during the follow-up. Research of antibodies against TTV was not applicable, as the patients studied were unable to produce antibodies. The presence of TTV was also evaluated in 15 IVIG lots.

RESULTS

The total amount of immunoglobulin administered was 18,773 g. TTV infection was not found in any patients included in the study. None of the 15 immunoglobulin preparations analyzed was found positive for TTV DNA.

CONCLUSION

Despite the high prevalence of TTV in blood donors, commercial immunoglobulins are safe and unable to transmit TTV.