Freeze-dried erythrocytes for an indirect hemagglutination test for detection of cytomegalovirus antibodies

Comparison of frozen versus desiccated reference human red blood cells for hemagglutination assays

BACKGROUND

Red blood cells (RBCs) are commonly used fresh or stored in frozen format for identification of patients' antibodies and serologic specificity of such antibodies at reference laboratories. However, maintaining a large pool of fresh RBCs is impossible in a blood-banking environment and blood in frozen format poses a logistic disadvantage in terms of accessibility, maintenance cost, safety, and sample recovery. This study explores an alternative, desiccation storage method for RBCs to provide a reagent that supports greater utilization and flexibility for reference laboratories.

STUDY DESIGN AND METHODS

RBCs from five donors were used in the study. RBCs were processed and kept in either frozen or desiccated format. Study variables for either the frozen or the desiccated cells included cell recovery as quantified by cell counts, gross microscopic examination, and hemagglutination assays.

RESULTS

The mean percentage of cell recovery for thawed and washed frozen RBCs was 20% versus 50% for rehydrated and washed desiccated RBCs. Microscopic examination of thawed cells from the frozen preparation showed cells with irregular shapes, a sharp contrast when compared with rehydrated cells from the desiccated preparation, where cells are mostly intact, smooth surface, and biconcave in structure. Cells in both preparations performed well in manual agglutination tests.

CONCLUSION

Desiccation preservation of RBCs provides a somewhat better RBC recovery and cell structure stability, while maintaining the necessary antigen-antibody reactions for cell surface markers, which will allow desiccated RBCs to be archived in blood collecting and processing reference laboratories.

Passive hemagglutination assays for the detection of antibodies to herpes viruses

A simple and effective method for the detection of antibodies to herpes simplex virus (HSV), human cytomegalovirus (HCMV) and varicella-zoster virus (VZV), has been established using the passive hemagglutination assay (PHA) in combination with viral specific glycoproteins. The results obtained with the PHA were compared with those from neutralization (NT) and complement fixation (CF) tests. The PHA test for each of the herpes viruses appears to compare favorably with the other assays tested. The specificity and sensitivity of HSV PHA to NT were 100%, whereas the specificity and sensitivity of HSV CF test to NT were 98% and 100%, respectively. For HCMV, the specificity and sensitivity of PHA to NT and PHA to CF were 100%. Similarly, the specificity and sensitivity of VZV PHA to NT were 100%. Because of the low sensitivity of the VZV CF, the sensitivity of CF to NT was 83%. Furthermore, the range of antibody titers and their absolute levels obtained in the PHAs were significantly greater than those in the NT and CF tests.

Passive hemagglutination for cytomegalovirus antibody: specificity and stability of reagents

Glutaraldehyde fixed red cells coated with CMV antigen were lyophilized in the presence of stabilizers such as glycerol, lactose, sorbitol and sucrose. These cells maintained their sensitivity for anti-CMV detection for at least 6 mth when held at 4 degrees C. Some rheumatoid factors containing sera react non-specifically with crude CMV antigen coated cells. The agglutinins in these sera could be effectively removed by adsorption with red cells coated with polymerized IgG.

Immunity to human cytomegalovirus measured and compared by complement fixation, indirect fluorescent-antibody, indirect hemagglutination, and enzyme-linked immunosorbent assays

The complement fixation test is currently the test employed most frequently to determine the presence of antibody to human cytomegalovirus. Several other techniques have been adapted for this purpose. A comparison of cytomegalovirus antibody titers was made between the complement fixation test, a commercially available enzyme-linked immunosorbent assay, an indirect immunofluorescent technique, and a modified indirect hemagglutination test. Forty-three serum samples were tested for antibodies by each of the above procedures. The enzyme-linked immunosorbent, immunofluorescent, and indirect hemagglutination assays were in close agreement on all samples tested; the titers obtained with these methods were all equal to or greater than the complement fixation titer for 38 of the 41 samples (92.6%). Two samples were anticomplementary in the complement fixation test but gave readable results in the other tests. The complement fixation test was the least sensitive of the procedures examined. The commercial enzyme-linked immunosorbent assay system was the most practical method and offered the highest degree of sensitivity in detecting antibodies to cytomegalovirus.

Rapid viral diagnosis

There has been much interest and activity in the development of techniques for rapid viral diagnosis which would allow successful intervention in the treatment of patients or their contacts or in the control of viral diseases in the community. The greatest emphasis has been on techniques that permit viral detection directly in the clinical specimen, since these avoid the need to cultivate the agent, are feasible for detection of viruses that cannot be cultivated, and can detect virus in specimens in which the agent is no longer infectious. Direct methods used for viral detection include electron microscopy and various immunoassays which are based on demonstrating reactivity of viral antigen in the specimen with known viral antisera. The use of immunoassays for more rapid identification of viruses isolated in laboratory host systems and for selective detection of viral antigen in inoculated cell cultures even before the agents produce an observable effect has been an important advance in viral diagnosis by the approach of isolation and identification. The reliability of all specific viral identification procedures depends on the use of high quality viral antisera. Some of the problems previously encountered in preparing satisfactory viral immune reagents are being overcome through the availability of highly specific monoclonal antibodies produced by cell hybridization techniques. Virus-specific IgM antibody assays for rapid diagnosis have been improved greatly through the use of a "capture" technique in which antibody to the human mu chain is used in the solid phase to separate IgM from other serum components which might compete with IgM antibody or give nonspecific reactivity, and also through the availability of highly specific monoclonal antibodies to the human mu chain. A variety of simple assays for determination of viral antibody status have been developed, and many are commercially available. The reliability of some of these antibody assays has been improved through the incorporation of more suitable controls and through better definition of interpretations which should be made from test results.

A method for coupling cytomegalovirus antigens to aldehyde-fixed erythrocytes for use in passive hemagglutination

A method for coupling cytomegalovirus (CMV) antigens to aldehyde-fixed erythrocytes for use in a passive hemagglutination assay for antibody to CMV is described. This method uses acid buffer instead of tannic acid for coupling CMV-complement fixation (CF) antigen to the stabilized cells. The coated cells are stable for at least 6 mth at -70 degrees C and for 5 days at 4 degrees C. This provides an inexpensive reagent having a sensitivity for anti-CMV detection which compares favorably with that of the CF test and enzyme immunoassay.

An indirect haemadsorption procedure (MRSPAH) for detecting antibodies to respiratory syncytial virus

A simple haemadsorption procedure for the detection of isotype specific antibodies to R.S. virus has been developed. Correlation between detection of R.S. virus IgG antibodies by mixed reverse (solid phase) passive antiglobulin haemadsorption (MRSPAH) and other serological procedures has been obtained. IgA antibody was detected in 62% of milk samples studied. The method is rapid, simple and uses commonly available serological reagents.