G.F. Mann

Effect of Gamma Irradiation on the Human Immunodeficiency Virus and Human Coagulation Proteins

Abstract. The effect of gamma irradiation on HIV and plasma coagulation factors F VIII:C, F VIII:vWF and FIX was studied. Donor plasma was harvested from single donations, frozen and irradiated in the frozen state at target doses from 0 to 40 kGy (0–4 mRad). HIV was inoculated into human plasma and irradiated in a similar manner. A range of other viruses, not suspended in plasma, were also irradiated to establish viral inactivation. An inactivation rate of 0.164 TCID50 dose/ml/kGy was demonstrated for HIV compared to rates of 0.00173, 0.00526 and 0.00286 log10 units/ml/kGy for F VIII:C, F VIII:vWF and FIX respectively. The use of gamma irradiation to inactivate infectious agents present in human plasma may eliminate the need for any post‐production viral inactivation methods and provide a means of assuring the safety of as yet untreated products such as cryoprecipitate and fresh frozen plasma.

IMMUNISATION OF 4-6 MONTH OLD GAMBIAN INFANTS WITH EDMONSTON-ZAGREB MEASLES VACCINE

Five different vaccination schedules were used to immunise Gambian infants aged 4-6 months against measles with the attenuated Edmonston-Zagreb strain of virus, which has a history of passage in human diploid cells. Vaccine aerosol given either by mask in a dose of 3500 or 7000 plaque-forming units (PFU) or from a plastic bag at a dose of 7000 PFU raised haemagglutinin-inhibiting or plaque-inhibiting measles antibody 16-24 weeks after vaccination to a titre of 1 in 8 or greater in all but 3 of the 51 children so vaccinated. All 21 infants given 11 400 PFU of vaccine intradermally in two divided doses and the 21 given 39 000 PFU of the virus subcutaneously also had satisfactory levels of measles antibody 16 weeks after vaccination. None of the vaccinated children had clinical evidence of measles in the 12 to 17 months after vaccination. The Edmonston-Zagreb vaccine, given subcutaneously or by other routes at 4-6 months, may be useful in preventing measles in infants in African cities, where 15-30% of children have measles before they are 9 months old, which is the recommended age for immunisation with the chick-cell-adapted strains of measles virus.

EFFECTS OF DOSE AND STRAIN OF VACCINE ON SUCCESS OF MEASLES VACCINATION OF INFANTS AGED 4-5 MONTHS

Small-scale trials of the Edmonston-Zagreb (E-Z) measles vaccine were undertaken to determine the dose necessary to immunise 4-6-month-old infants. Antibody responses, measured 16 weeks after vaccination, were dose dependent: 40,000 plaque forming units given subcutaneously resulted in positive responses in all infants and higher antibody levels than doses of 20,000 or 10,000 units (10,000 units gave a failure rate of 25%). In further trials the E-Z vaccine was compared with the Schwarz vaccine, both being given in subcutaneous doses of 40,000 plaque forming units. In infants aged 20 weeks the E-Z vaccine produced higher levels of measles antibody and in those aged 18 weeks its superiority showed in a lower proportion failing to respond (3 of 39 versus 19 of 35).

COMPARISON OF EDMONSTON-ZAGREB AND SCHWARZ STRAINS OF MEASLES VACCINE GIVEN BY AEROSOL OR SUBCUTANEOUS INJECTION

The serological response to measles vaccine was tested in Bangladesh in groups of infants aged 4-6 months who received equal doses of Edmonston-Zagreb or Schwarz vaccine by subcutaneous injection or by aerosol. Seroconversion (as measured by the haemagglutination test) occurred in 62% of infants receiving Edmonston-Zagreb strain by injection compared with only 37% of those receiving Schwarz strain. Seroconversion occurred in 35% of those given Edmonston-Zagreb and 34% of those given Schwarz vaccine by aerosol. Edmonston-Zagreb strain appears more effective than Schwarz vaccine in this population and further studies are indicated in other populations where early measles immunisation is desirable.

Clinical and Research Application of an Enterovirus Group-Reactive Monoclonal Antibody

Diagnostic methods employed in enterovirus laboratories are generally laborious, slow and expensive. This is largely because type-specific neutralization tests still play the major role in identification and diagnostic serology. In the companion paper we describe the derivation of monoclonal antibodies against epitopes of the VPI peptide which are shared by all of the enteroviruses tested to date, with the exception of hepatitis A virus. This study describes the application of one of these monoclonal antibodies in several research and diagnostic procedures, illustrating a special utility in a wide variety of assay systems. This monoclonal antibody has proved particularly useful in the detection of enterovirus antigens in circulating immune complexes, and in identifying field isolates of this group of viruses. Immunohistochemistry, previously almost impossible in enterovirus diagnosis and research due to the large number of serotypes, is now shown to be practical and informative when this monoclonal antibody is used.

A simplified plaque assay system for measles virus.

A plaque assay for measles virus in Vero cells under a carboxymethylcellulose overlay is described. Due to the small plaque size, 24 well plates can be used giving an assay applicable to large numbers of samples while retaining the precision of traditional plaque assay systems. In addition to precise quantitative values for infectivity, the method allows for monitoring of qualitative plaque type and provides a permanent record of the test. Plaque and TCD 50 assay systems were found to give comparable results in tests where conditions of virus adsorption were similar. The method has been successfully applied to the stability testing of measles vaccines and is applicable to other aspects of vaccine standardization.

An accelerated stability test procedure for lyophilized measles vaccines.

The design and evaluation of a practical procedure for the accelerated stability testing of lyophilized measles vaccines is presented. Two components were apparent in the regression lines following the determination of residual virus when using a plaque assay method. The test gave consistent results and unequivocal differentiation of first and second generation vaccines. Values for the second and major component could be used to distinguish between products on the basis of slope and position in the Arrhenius plot. An inverted form of this plot, with corrections for vial content, diluent volume and degradation components, is proposed as a means of predicting the time taken to reach the minimum titre at various storage temperatures.

Nondetection of Infectious Hepatitis B Virus in a Human Hepatoma Cell Line Producing Hepatitis B Surface Antigen

The PLC/PRF/5 human hepatoma cell line producing hepatitis B surface antigen (HBsAg) was studied to determine whether infectious hepatitis B virus (HBV) was also being produced. 2 chimpanzees with no previous exposure to HBV and no serologic markers of past or active HBV infection were inoculated intravenously with 50 ml of either tissue culture supernatant fluid (357 ng/ml HBsAg) or a suspension of cells disrupted by repeated freeze-thaw cycles (57 ng/ml HBsAg). No evidence of HBV infection was detected in either chimpanzee during 6 months of evaluation. This study suggests that the expression of a portion of the HBV genome, when a portion or all of that genome has been incorporated into a host cell, can result in the production of HBsAg without infectious HBV. If it becomes possible to produce a similar expression of this portion of the genome by itself in nonmalignant cells, HBsAg without HBV may be produced in vitro for use in hepatitis B vaccines.

Detection of HBsAg in a clone derived from the PLC/PRF/5 human hepatoma cell line

SummaryA total of 28 clones were established from the PLC/PRF/5 hepatoma cell line by a plating procedure. All clones were found to secrete HBsAg into the supernatant culture fluids. Of these, one clone (No. 23) free of detectable mycolasma contamination and showing smooth epithelial morphology was selected for further study. Maximum accumulation of HBsAg occurred 9 days after sub-culture and intracellular antigen was detected by indirect immunofluorescence both in the cytoplasm and at the plasma membrane. Granules and perinuclear staining reactions were also observed in clone 23 cells and these findings are compared to the previously published properties of the parental PLC/PRF/5 cell line.

Thermal inactivation of pichinde virus

Detailed information regarding the kinetics of thermal inactivation of Pichinde, an arenavirus, is presented. Inactivation of virus infectivity proceeded as a first order reaction over the temperature range 22-53 degrees C. The determined inactivation rates analysed as a function of absolute temperature revealed that two different reactions were involved. Below 37 degrees C, the energy of activation was determined to be compatible with RNA degradation, whereas at higher temperatures a correspondingly greater value suggests that protein inactivation contributes significantly to loss of infectivity. Both inactivation reactions were retarded in the presence of foetal calf serum to a final concentration of 1%. The relatively short half-life of 12-24 h at 22 degrees C suggests transmission in nature via contaminated foodstuffs and soil may be inefficient.