Transfusion-transmitted cytomegalovirus infections: significance and control

The Epidemiology of Cytomegalovirus Infection Among Patients with Burns

To determine the epidemiology of cytomegalovirus (CMV) infections among patients with burns, we prospectively studied 120 burn patients admitted to the University of Iowa Burn Center over a two-and-one-half year period. At the time of their admission, 44% of the patients had serologic evidence of prior CMV infection. Among 44 seropositive patients, 23 (52%) had four-fold or greater rises in CMV antibody titers. These patients had more severe burns (mean body surface area burn [BSAB] 26.8%) than those who did not exhibit titer rises (mean BSAB 16.2%, p=.04). Among 43 seronegative patients observed for at least 65 days after discharge from the center, eight (18.6%) seroconverted. Patients who seroconverted had longer hospital stays (p=.03), trends toward more severe burns p = .08) and a younger age (p = .15) than patients who remained seronegative. Despite frequent serologic evidence of CMV infection, CMV did not contribute, either directly or indirectly, to the morbidity or mortality of burns in these patients.

Photochemical treatment of platelet concentrates with amotosalen hydrochloride and ultraviolet A light inactivates free and latent cytomegalovirus in a murine transfusion model

BACKGROUND

A photochemical treatment (PCT) process utilizing amotosalen hydrochloride and long wavelength UVA light has been developed to inactivate pathogens in PLTs. This study investigated the effects of amotosalen/UVA treatment on free and latent murine CMV (MCMV) in PLT preparations using a murine model of transfusion-transmitted CMV (TT-CMV).

STUDY DESIGN AND METHODS

In a model of latent MCMV infection, "donor" mice received 1 x 10(6) plaque-forming units (PFUs) MCMV and were rested 14 days. Subsequently harvested, pooled, and washed WBCs were PCR positive for MCMV. Murine WBC doses of 1 x 10(4), 1 x 10(5), and 1 x 10(6) were added to human apheresis PLTs in 35 percent autologous plasma and 65 percent PLT AS (PAS). The WBC-PLT products were treated with 150 micro mol/L amotosalen and 0.6 J per cm2 UVA and transfused via tail vein injection into recipient mice. Recipients were killed on Day 14. Blood and spleens were collected and assayed for MCMV by PCR. In a parallel model of active infection with free virus, human PLT in 35 percent autologous plasma and 65 percent PAS were dosed with 1 x 10(5) and 1 x 10(6) PFUs of MCMV. All other procedures were as described above.

RESULTS

In the absence of amotosalen/UVA-pretreatment, transfusion of PLT latently or actively infected with MCMV produced TT-CMV in a dose-dependent fashion. In contrast, all transfusion recipients of identical PLT preparations pretreated with amotosalen/UVA were uniformly PCR negative for MCMV (abrogation of TT-CMV; p < 0.05).

CONCLUSIONS

PCT of PLT preparations with the specified doses of amotosalen hydrochloride and UVA light prevents transfusion transmission of free and latent MCMV in a murine model. These results suggest that PCT of human PLTs with amotosalen/UVA should also effectively abrogate TT-CMV in the clinical setting.

Lymphocyte subpopulations during cytomegalovirus disease in renal transplant recipients

We have determined the number of circulating T, B and natural killer cells in renal transplant recipients in order to detect changes during cytomegalovirus (CMV) infections. Serial blood samples were taken from 61 patients on standard triple immunosuppression therapy (cyclosporin A, azathioprine and prednisone). Using two-color flow cytometry analysis, the absolute number of CD3+, CD4+, CD8+, CD19+, CD3+HLA-DR+ and CD16+56+ cells was determined. Forty-eight patients (78.7%) developed active CMV infection, and all of them subsequently recovered. Twenty of the infected patients (32.8%) presented symptoms compatible with CMV disease during the infectious process. The number of lymphocytes and their main subpopulations were normal before the onset of CMV disease. During the disease there was a decrease followed by a significant increase (P<0.005) in the number of CD3+, CD4+, CD8+ and CD3+HLA-DR+ cells. No significant changes were observed in natural killer cells or B lymphocytes during the disease. We conclude, as observed in all viremic patients recovering from infection, that recovery is associated with an increase in the number of T cell subsets. The monitoring of different lymphocyte subsets along with antigenemia can be extremely useful in the detection of patients at high risk of developing CMV symptoms, allowing the early introduction of antiviral therapy or the reduction of immunosuppression therapy.

Growth of human cytomegalovirus in primary macrophages

Human cytomegalovirus (HCMV) is a major human pathogen that causes considerable disease among immunocompromised individuals. A primary infection results in life-long persistence of the virus in a latent form. HCMV is known to be transferred by blood products, bone marrow, and solid organs, but the cell type that carries the latent infection has been difficult to identify. We have recently demonstrated reactivation of latent HCMV in allogeneically stimulated monocyte-derived macrophages (Allo-MDM). Reactivation occurred only in macrophages produced by allogeneic but not mitogenic stimulation. The presence of dendritic cell markers on some Allo-MDM cells suggested that these macrophages were related to dendritic cells. However, dendritic cells obtained by stimulation of monocytes with interleukin-4 (IL-4) and granulocyte-macrophage colony stimulating factor (GM-CSF) were not permissive for HCMV infection. The cellular and cytokine components which are essential for HCMV replication and reactivation of virus were also examined in Allo-MDM. The importance of both CD4- or CD8-positive T cells in the generation of HCMV permissive Allo-MDM was demonstrated by negative selection or blocking experiments using antibodies directed against both HLA class I and HLA class II molecules. Examination of the cytokines essential for the generation of HCMV permissive Allo-MDM identified gamma-interferon (IFN-gamma, but not IL-1, IL-2, tumor necrosis factor alpha, or GM-CSF as critical components in the generation of these macrophages. However, addition of IFN-gamma to unstimulated macrophage cultures was insufficient to reactivate virus. These results indicate the importance of a specific moncyte stimulus in the generation of a unique HCMV permissive macrophage phenotype as well as why virus is commonly reactivated in transplant patients.

Effect of hepatitis C antibody screening in blood donors on post-transfusion hepatitis in Taiwan

A national screening programme for antibody to hepatitis C virus (HCV) in blood donors in Taiwan began in July 1992 using a second-generation immunoassay. To study the impact of this screening on post-transfusion hepatitis in Taiwan, a prospective study on post-transfusion hepatitis, that was started in 1987, was continued. As of June 1994, 245 patients who received a blood transfusion after July 1992 had completed a follow-up period for more than 6 months post-transfusion. Of them, seven (2.8%) recipients developed acute post-transfusion hepatitis. The hepatitis in six cases could not be attributed to infection by hepatitis A, B, C, D, E viruses or cytomegalovirus (CMV) or Epstein-Barr virus (EBV). The remaining patient seroconverted to both IgG and IgM anti-CMV. All seven patients recovered in 6 months without development of chronicity, and the mean peak alanine aminotransferase level was lower compared with that of the cases before anti-HCV screening (i.e. pre-July 1992). These results indicate that the current anti-HCV screening has effectively interrupted HCV transmission through blood transfusion in Taiwan.

Removal of cytomegalovirus DNA from donor blood by filtration

Blood from five donors, previously shown to be positive for cytomegalovirus (CMV) DNA following polymerase chain reaction (PCR) amplification, was filtered through commercially available leucocyte filters. Analysis of pre- and post-filtration samples by PCR with ethidium bromide staining has shown that filtration was successful in removing CMV DNA from all samples. This is evidence that leucocyte filtration of red cell concentrates may greatly decrease the risk of CMV disease following transfusion to susceptible patients.

Cytomegalovirus studies on blood donors in north-east Scotland and a review of UK data

The epidemiology of cytomegalovirus (CMV) infection as assessed by CMV antibody testing varies significantly in different parts of the world and also in different regions of a country. A study was therefore carried out to assess the prevalence of CMV antibody in our blood donors, looking in particular at different subgroups of donors as divided by age, sex and social class, to see how we could maximise the yield of CMV-negative blood from our testing. It was shown that patterns of CMV infection in the North East of Scotland followed well-established norms. Data from other Regional Transfusion Centres within the UK were also collected for comparison.

Geographic risk factors for viral hepatitis and cytomegalovirus infection among United States Armed Forces blood donors

In an effort to determine whether residence in a foreign country increases the risk of hepatitis B and C and cytomegalovirus (CMV) infection in United States (US) Armed Forces blood donors, 5719 volunteer donors at four US Navy blood banks were evaluated. Most participants were repeat donors (68%) and were young (mean age, 25 years), male (88%), and white (80%), black (10%), or Hispanic (7%). Birth outside of the United States was reported by 6 percent of subjects, and 34 percent had lived in a foreign country for more than 3 months. Twenty (0.3%) subjects had hepatitis B surface antigen (HBsAg), and 100 (1.7%) had antibody to hepatitis B core antigen (anti-HBc). Thirty-four (0.6%) were repeatably reactive in enzyme-linked immunosorbent assay for antibody to hepatitis C virus (anti-HCV); 11 (0.2%) had anti-HCV in immumoblot assay. Of the 3484 donors tested for anti-CMV, 1117 (32.1%) were positive. When demographic characteristics were controlled for both anti-HBc and anti-CMV seropositivies were independently associated in male blood donors with residence in the Philippines. Geographic factors were not associated with HBsAg and anti-HCV positivity. These findings indicate that the prevalence of serologic markers for viral hepatitis is low in military blood donors, but that residence in the Western Pacific is a risk factor for hepatitis B and CMV infection.

Blood-borne Infections Associated with Transfusion

The epidemic of acquired immunodeficiency syndrome (AIDS) and the realization that transmission of human immunodeficiency virus is caused by homologous blood transfusion have changed the way physicians and their patients view the safety of hemotherapy. Considering that nearly four million patients receive the lifesaving benefits of blood transfusions every year in the United States, we need to recognize and reduce the inherent biological complications of this therapy. Currently, a major concern is the transmission of blood-borne infectious agents and the establishment of persistent infection in transfusion recipients, which is apparently facilitated by suppression of the recipient's hematopoietic and immune systems. Education of blood donors, patients, and attending physicians regarding infectious complications of transfusion is essential and remains the most effective procedure for making rational decisions. Before giving blood transfusions, astute physicians should calculate a risk/benefit ratio and communicate it to the patient or family. Potential recipients of transfusions can be assured that the blood supply is safer now than at any time in the past, although there is still a very small risk for the transmission of infectious agents that cause chronic diseases, such as hepatitis, AIDS, neuropathies, and leukemias. It is essential that everyone understands that the goal of a zero-risk blood supply is not attainable. Recent developments in molecular biology and biotechnology, however, provide opportunities for further reduction of infectious complications of blood transfusions.

Transfusion-acquired cytomegalovirus infection in children in a hyperendemic area

Thirty-nine children without previous cytomegalovirus (CMV) infection received blood transfusion in the National Taiwan University Hospital. The overall transfusion-acquired CMV infection rate was 36% (14/39). Donor CMV seropositive rate was 70%. None of the nine children who had received seronegative blood became infected, in contrast to 14 of the 21 children (67%) who had received seropositive blood (P = 0.002). Another significant risk factor associated with CMV infection was the use of fresh blood: 13 of 15 (87%) with fresh seropositive blood were infected, in contrast to one of six (17%) with "old" seropositive blood (P = 0.01). Most of the fresh blood was used within 24 hours. This blood processing method was shown to account for the extremely high rate of CMV infection in those who had received fresh seropositive blood. The results indicated that the incidence of CMV infection can be reduced by avoiding the use of fresh blood, especially blood less than 24 hours old. For such a population in Taiwan with high prevalence of positive CMV antibody, this approach was more applicable than screening donor blood for CMV antibody.

Post-transfusion hepatitis

Prospective international studies have shown the incidence of post-transfusion hepatitis in the 1980s to vary between 2% and 31%. Rare cases of hepatitis B continue to occur despite donor screening for the hepatitis B surface antigen, but most are of the non-A, non-B type. Non-A, non-B hepatitis is typically mild and often subclinical in the acute phase but has a tendency to become chronic in about half the affected subjects. The recently characterised hepatitis C virus has been shown to cause most, if not all, transfusion associated non-A, non-B hepatitis. Hepatitis C seropositivity seems to be associated with viraemia and infectivity among blood donors, and donor screening for these antibodies has now been instituted in many countries. New assays now being developed are improving the sensitivity and specificity of this screening, which is estimated to prevent most cases perhaps 70 to 80% of post-transfusion hepatitis.

Polymerase chain reaction for detection of human cytomegalovirus infection in a blood donor population

We have used the polymerase chain reaction (PCR) to analyse 420 normal donor blood samples taken at a city centre donation site. Three sets of human cytomegalovirus (HCMV) primers specific to the HXLF6, immediate early and late antigen gp64 genes, of the alpha, beta and gamma antigen coding regions respectively, were used to allow for the possibility of sequence variation. There was perfect correlation between the three sets of primers. Latex agglutination and enzyme-linked immunosorbent assay (ELISA) were also employed to provide data for a comparative study. The complete data show that infection with human cytomegalovirus is not only age related but is also sex related. The female population examined using PCR reached a peak infection rate of 80% by the age of 40-50 years whereas the male population reached a 98% infection rate following an almost linear increase with age. Latex agglutination data shows a similar picture although the infection rate peaks around 20% lower than with PCR. The data shows an increase in sensitivity using the PCR rather than the serology although the clinical significance of this has yet to be determined. The work presented here also demonstrates the suitability of the polymerase chain reaction as a potential diagnostic and epidemiological tool.

Screening plasma donors for high-titre antibody to cytomegalovirus using a latex agglutination test

Cytomegalovirus (CMV) can cause severe morbidity in immunosuppressed patients. Regional transfusion centres in the UK are required to supply high-titre anti-CMV plasma to the Blood Products Laboratory (BPL), now called 'Bio-Products Laboratory', for the production of specific intravenous immunoglobulin at the Protein Fractionation Centre in Scotland. For this purpose, 703 plasmapheresis donors were screened by a modified latex agglutination test to assess their suitability as donors with high-titre anti-CMV. CMV antibodies were found in 48% of the donors. Seropositivity increased with age ranging from 33% in the 20- to 29-year age group to 57% in the 40-49 age group, although the 50-59 age group showed a slight decline to 53%. In all age ranges except the 40-49 group, seropositivity was highest in the female population. With the latex test, 14% of the total donors screened had a titre greater than or equal to 1 in 64, 7% greater than or equal to 1 in 128 and 4.2% greater than or equal to 1 in 256. Samples from 18 donors with titres greater than or equal to 1 in 128 were sent to BPL and all samples were found to have a sufficiently high titre for the production of CMV immune plasma. For BPL the 'cut-off' level for CMV immune plasma is a titre greater than or equal to 1 in 64 by complement fixation. Since the establishment of a panel of donors with high-titre anti-CMV plasma, more than 10 kg of plasma are dispatched monthly from our centre to BPL.

The epidemiology of cytomegalovirus infection among patients with burns

To determine the epidemiology of cytomegalovirus (CMV) infections among patients with burns, we prospectively studied 120 burn patients admitted to the University of Iowa Burn Center over a two-and-one-half year period. At the time of their admission, 44% of the patients had serologic evidence of prior CMV infection. Among 44 seropositive patients, 23 (52%) had four-fold or greater rises in CMV antibody titers. These patients had more severe burns (mean body surface area burn [BSAB] 26.8%) than those who did not exhibit titer rises (mean BSAB 16.2%, p = .04). Among 43 seronegative patients observed for at least 65 days after discharge from the center, eight (18.6%) seroconverted. Patients who seroconverted had longer hospital stays (p = .03), trends toward more severe burns (p = .08) and a younger age (p = .15) than patients who remained seronegative. Despite frequent serologic evidence of CMV infection, CMV did not contribute, either directly or indirectly, to the morbidity or mortality of burns in these patients.

Provision of a panel of anti-toxoplasma-negative blood donors

Toxoplasma gondii has been reported to cause complications only in immunosuppressed patients receiving leucocyte transfusion, when severe acute toxoplasmosis has been reported with associated mortality. At the North London Blood Transfusion Centre (NLBTC) we have screened 392 plasmapheresis donors (using toxoreagent latex agglutination test manufactured by Eiken) to provide a panel of blood donors negative for antibody to toxoplasma for seronegative recipients. A toxoplasma-negative panel of donors would only be required for those rare instances when granulocyte concentrates are indicated for transfusion of seronegative recipients. The toxoreagent test classified the 392 blood donors as 36% positive, 23% weakly reactive and 41% negative; these negative sera were retested with toxoreagent and 17% of them reacted weakly but none were positive. The toxoreagent 'weakly-reactive' sera (all of which were Sabin-Feldman dye test negative) can probably best be accounted for by the exacting screening conditions under which we operated to ensure seronegativity in our special donor panel. 40% of the antibody-positive donors were female and 34% male. Seropositivity increased with age.

Blood transfusion and hepatitis: still a threat?

The incidence of post-transfusion hepatitis (PTH) in recipients of blood products is reviewed. PTH was observed in 10%-12% of recipients of blood products in the United States, 2%-4% in northern Europe and 15%-20% in southern Europe. All studies indicate that 80%-90% of all PTH cases are attributed to non-A/non-B. At least 40% of the patients with PTH non-A/non-B will develop chronic hepatitis or cirrhosis. No specific tests for the detection of the non-A/non-B agent(s) exist. However, several independent studies indicate that part of the donors carrying the infectious non-A/non-B agent have increased levels of alanine amino transferase (ALT). When donors are excluded with elevated ALT values, it is estimated that about 30% of the PTH non-A/non-B cases would be prevented. Some studies indicate that anti-hepatitis B core (anti-HBc) positive donors may carry an increased risk to transmit the non-A/non-B agent, but more recent studies do not confirm this. There is hope that a specific non-A/non-B test will be developed soon.

Detection of cytomegalovirus-specific IGM in renal transplant recipients

We have compared two IgM-specific cytomegalovirus (CMV) antibody assays, an immunofluorescence assay (IFA-M) and an enzyme-linked antigen immunoassay (ELA-M), with an assay for CMV total antibody (ELISA) and viral culture for the detection of active CMV infection in renal transplant recipients. Of 75 patients (49 ELISA negative pretransplant, 26 ELISA positive), CMV-specific IgM was detected in 35 (27 ELISA negative pretransplant, 8 ELISA positive) using the IFA-M assay and in 25 (16 ELISA negative pretransplant, 9 ELISA positive) using the ELA-M test. Of the 25 patients identified as positive by ELA-M, 21 had positive viral cultures post-transplant, two seronegative patients had evidence of infection indicated by post-transplant seroconversion, and two patients were seropositive pretransplant but remained viral culture negative throughout the follow-up period. ELA-M and CMV total antibody ELISA detected primary infection in renal transplant recipients equally well, but ELA-M was found to be superior to ELISA and IFA-M for detecting reinfection and reactivation infections.

Prevalence of cytomegalovirus antibody in hemophiliacs and homosexuals infected with human immunodeficiency virus type 1

We determined the prevalence of antibody to cytomegalovirus (CMV) in the sera of non-homosexual hemophilia patients and homosexual men infected with the human immunodeficiency virus type 1 (HIV-1). CMV antibody testing by latex agglutination revealed 33 of 58 HIV-1 infected hemophiliacs (57%) were antibody-positive compared with 54 of 54 HIV-1 infected asymptomatic non-hemophiliac homosexuals (100%) (p less than .001). Nine of 15 hemophiliacs (60%) with symptomatic HIV-1 infection were CMV antibody-positive. We also tested 22 HIV-1 antibody-negative hemophiliacs who had received non-heat treated factor concentrates. 14 of these 22 (64%) were CMV antibody-positive compared with 57% of HIV-1 antibody-positive hemophiliacs. We conclude 1) there is little correlation between transmission of HIV-1 and CMV by factor concentrates, 2) the presence of CMV antibody does not appear to be associated with clinical stage of HIV-1 infection in hemophiliacs, and 3) there may be a significant number of CMV antibody-negative hemophiliacs with HIV-1 infection at risk for primary infection and subsequent disease if CMV seronegative blood products are not provided for future transfusions.

Cytomegalovirus and blood transfusion

The problem of transfusion-transmitted cytomegalovirus (CMV) infection differs from that for other transfusion-transmitted infections in that only patients who are immunocompromised require CMV-free blood or components. The virus is cell-associated and transmission appears to be due to reactivation of latent virus in white blood cells. As a herpes virus, CMV can be responsible for primary infections, reactivations or reinfections in humans. The use of restriction endonuclease techniques is sometimes necessary to pinpoint the origin of infections. Serological studies have shown that CMV infection is worldwide, but seropositivity rates vary widely being highest in underdeveloped countries, rising both with age and lower socio-economic status. Provision of CMV seronegative blood therefore involves considerable administrative as well as laboratory effort and planning, especially if panels of previously tested, seronegative donors are organized. Serious complications of transfusion-transmitted CMV infection (which can occasionally prove fatal) are only seen with immuno-suppressed patients (commonly low birth weight infants or transplant recipients). Prevention or amelioration of CMV infection with appropriate patients can be attempted by reducing the number of white blood cells present in blood or components by filtration or washing, administration of CMV immune globulin or provision of blood found by serological screening to be CMV-seronegative.