Removal of cytomegalovirus DNA from donor blood by filtration

Leukodepletion filters reduce Leishmania in blood products when used at collection or at the bedside

BACKGROUND

Leishmania is an intracellular parasite of monocytes transmissible by transfusion. The feasibility of reducing Leishmania with leukodepletion filters was studied. At collection, infected blood contains the amastigote form of Leishmania within monocytes. Amastigotes cause the rupture of monocytes releasing free amastigotes that convert to promastigotes, which exist extracellularly at blood storage temperatures. Leukodepletion filters were tested at various time points in this process.

STUDY DESIGN AND METHODS

Blood products were infected with Leishmania organisms and then filtered with whole-blood filters at collection, with bedside filters after storage, and to determine whether free promastigotes could be eliminated.

RESULTS

Filtration at collection reduced Leishmania by 3 to 4 log or to the level of detection. Filtration of infected red cells after 2 weeks of storage showed a reduction of Leishmania by 4 log. Filtration resulted in a 6- to 8-log reduction in promastigotes either in the presence or in the absence of white cells within the filter.

CONCLUSION

Filtration at the time of collection and after storage of Leishmania-infected blood resulted in a substantial reduction of free and intracellular organisms. There is currently no donor screen for Leishmania. Until adequate testing is developed, the use of leukodepletion filters could add to the safety of the blood supply.

Congenital and perinatal infections with cytomegalovirus

Congenital cytomegalovirus (CMV) infections remain the leading viral cause of congenital malformations in the developed world. Despite advances in our knowledge, the epidemiology and natural history of congenital CMV infection are still poorly understood, particularly in Australia. Congenital CMV causes illness ranging from no clinical disease (asymptomatic, but infected) through to prematurity, encephalitis, deafness and haematological disorders and death. Perinatal CMV acquisition usually results in less severe illness including asymptomatic infection, acute infection with hepatitis, fever, and pneumonitis. CMV infects only humans, and in vitro and in vivo models for intrauterine infection are required in order to test new treatments, and better describe the pathogenesis of congenital CMV. Using new knowledge of the epidemiology and natural history of CMV, treatment regimens during late pregnancy are currently undergoing clinical trial although no definitive recommendations are available.

Lack of difference in cytomegalovirus transmission via the transfusion of filtered-irradiated and nonfiltered-irradiated blood to newborn infants in an endemic area

BACKGROUND

It is accepted that white cells contained in blood components are the most significant source of cytomegalovirus (CMV) infection in immunocompromised and immunodeficient recipients.

STUDY DESIGN AND METHODS

To determine whether white cell filtration of blood would be effective in preventing infection among newborn transfusion recipients in a hyperendemic area, a randomized study was performed. All donor blood units were irradiated before issue to prevent posttransfusion graft-versus-host disease. Recipients were monitored for CMV infection by seroconversion (development of IgM anti-CMV) and CMV-DNA isolation.

RESULTS

Three (9%) of 33 infants who received filtered blood and 1 (5%) of 19 infants given nonfiltered blood were infected with CMV, as determined by the presence of IgM anti-CMV and/or CMV DNA isolation.There was no significant difference in the rate of CMV infection in the two groups.

CONCLUSION

The CMV infection observed in the study may come from other routes such as breastfeeding, rather than from transfusion. Our findings suggest that the routine use of white cell-reduction filtration to reduce the risk of transmitting CMV is unwarranted for neonates in endemic regions.

Polymerase chain reaction based assessment of leukoreduction efficacy using a cytomegalovirus DNA transfected human T-cell line

BACKGROUND AND OBJECTIVES

Detection of CMV DNA by PCR in seropositive blood donors is affected by nucleic acid extraction, amplification conditions and PCR product detection sensitivity. Clinical studies have shown that leukoreduced blood products are as effective as CMV-seronegative blood products in minimizing transfusion-associated CMV infection. We developed a PCR-based test model to assess the efficacy of leukoreduction on the removal of CMV DNA from blood donations.

MATERIALS AND METHODS

Whole blood units were spiked with a human Jurkat T-lymphocyte cell line which had been stably transfected with a CMV DNA immediate early sequence. All blood units were either CMV seronegative or shown to be CMV PCR negative. The amount of CMV DNA by PCR before, during and after filtration of blood units with third-generation leukocyte reduction filters were determined using a semi-quantitative adaptation of the Digene SHARP Signal System Assay (DSSSA).

RESULTS

Whole blood units spiked with 1-2 x 10(6) CMV transfected Jurkat cells contained no detectable CMV DNA after leukoreduction. With a higher inoculum of 2.9 x 10(8) transfected Jurkat cells per unit, CMV DNA was detected after leukoreduction; however, there was an approximate 3 log decrease in the amount of CMV DNA detected.

CONCLUSION

This CMV DNA transfected human Jurkat cell line in conjunction with semi-quantitative CMV PCR may be used to model leukoreduction efficacy and provides evidence that leukoreduction of blood products can decrease the amount of cellular CMV DNA by approximately 3 logs.

Cell types involved in replication and distribution of human cytomegalovirus

As the number of patients suffering from severe HCMV infections has steadily increased, there is a growing need to understand the molecular mechanisms by which the virus causes disease. The factors that control infection at one time and the events leading to virus multiplication at another time are only beginning to be understood. The interaction of HCMV with different host cells is one key for elucidating these processes. Through modern techniques, much has been learned about the biology of HCMV infections in culture systems. In addition to endothelial cells, epithelial cells, and smooth muscle cells, fibroblasts are one cell population preferentially infected in solid tissues in vivo. From these sites of multiplication, the virus may be carried by peripheral monocytes and circulating endothelial cells to reach distant sites of the body. This would explain the multiorgan involvement in acute HCMV infection and the modes of viral transmission. From what has been learned mainly from human fibroblast culture systems, future studies will focus on how HCMV regulates the expression of its putative 200 genes in different host cells at different stages of cell differentiation and activation to result in viral latency and pathogenesis.

Membrane related effects in endothelial cells induced by human cytomegalovirus

Previously, we have reported on the increase in procoagulant activity of human umbilical vein endothelial cells (HUVEC) after infection with human cytomegalovirus (HCMV). When using microvascular endothelial cells from foreskin (MVEC), we also observe a significant increase in membrane perturbation and a concomittant increase in procoagulant activity. This effect is both observed with a laboratory HCMV strain (AD169) with low pathogenicity for endothelium and a HUVEC adapted strain (VHL-E) that readily infects endothelial cells. We compared the membrane perturbation of two types of endothelial cells, HUVEC and MVEC with human embryonal fibroblasts (HEF), being fully permissive for both strains. A membrane effect was only found in endothelial cells. Our results suggest that HCMV induces in MVEC more merocyanine-540 incorporation in the membrane as in HUVEC. The increase in the procoagulant activity induced by HCMV was more pronounced in MVEC than in HUVEC. Inactivated virus, as well as virus pre-incubated with heparin was unable to evoke membrane perturbation. It therefore appears that HCMV induces a rapid membrane response in vascular endothelium and that physical interaction of the virion and the endothelial cell is required to elicit this response.

Transfusion-transmitted cytomegalovirus: the part-time pathogen

Viral infection is a well-known risk of blood product transfusion and much work has been devoted to the detection of such well-known pathogens as human immunodeficiency virus and hepatitis viruses in blood donors. Cytomegalovirus (CMV) is found in a much larger percentage of donor units than these other viruses but will cause disease in only a minority of recipients. Many pediatric patients (especially premature infants) are at risk for transfusion-transmitted CMV. This review describes work delineating the populations of patients most at risk for transfusion-transmitted CMV, describes methods for detecting CMV in blood donors, evaluates current methods for leuko-depletion of blood products, and provides recommendations for patients most likely to benefit from blood products with low risk of CMV transmission.

Viral contamination of blood components and approaches for reduction of infectivity

Currently, the United States blood supply offers a relatively low risk of viral infection. This is a result of careful selection of donors and extensive laboratory testing using sensitive procedures. Epidemiologic data show that there is some room for improvement in donor selection, but such improvements cannot be expected to entirely eliminate the collection of blood from infectious donors. Similarly, increased numbers of tests, along with improvements in the analytic sensitivity of these tests, may further reduce risk, but again, complete safety cannot be assured. Consequently, there is continuing interest in the development of safe and effective procedures for viral inactivation of single donor blood components. In order to establish appropriate expectations for such inactivation procedures, it is necessary to understand the titers and distributions of viral contaminants in blood components. Viruses may variously occur free in the plasma, as replicative forms in actively infected leukocytes, as integrated proviral DNA and perhaps, nonspecifically associated with cellular surfaces.