Removal of viral contaminants by monoclonal antibody purification of plasma proteins.

The transmittance of pathogenic viruses by the widespread administration of protein fractions such as F VIII prepared on a large scale from pooled human plasma has been of growing concern. We have now demonstrated that significant amounts of pathogenic viruses including LAV/HTLVIII may be removed by a new large scale fractionation process for the preparation of human F VIII (Monoclate) which employs immunoaffinity chromatography. Model viruses representative of different virus families and the LAV strain of HIV were added to cryoprecipitate and then the mixture was processed as for Monoclate manufacturing. Virus titers were determined at each step of the fractionation procedures. An overall reduction of at least 6 logs was obtained for the model viruses and the HIV due to the purification process. An added heating step further increased the safety margin for the product resulting in at least an overall reduction of 7-9 logs for HIV. Clinical experience with Monoclate in virgin hemophiliacs has confirmed its viral safety. Our laboratories are exploiting a similar strategy of immunoaffinity chromatography to ensure the viral safety of FIX and protein C preparations derived from plasma.

Prevention of reactivated herpes simplex infection by human leukocyte interferon after operation on the trigeminal root.

Microneurosurgical procedures on the trigeminal-nerve root are often followed by reactivation of herpes simplex virus infection, manifested by herpes labialis or oropharyngeal herpesvirus shedding or both. In a double-blind study of the ability of human leukocyte interferon to prevent this reactivation, patients with a history of herpes labialis were given 7 x 10(4) U of interferon per kilogram of body weight per day or placebo for five days beginning on the day before operation. In 18 patients treated with placebo, herpes labialis developed in 10, and virus shedding in the oropharynx in 15. In 19 patients treated with interferon, lesions developed in five, and shedding in eight. The frequency of reactivation as measured by lesions or positive throat cultures or both was significantly reduced by interferon (P less than 0.05). Of 127 daily throat-wash cultures in the placebo group, 42 per cent were positive for herpesvirus, but of 134 in the interferon group, only 9 per cent were positive (P less than 0.001). We conclude that interferon at a well-tolerated dosage reduces reactivation of latent herpes simplex virus infection after a potent operative stimulus.

Production of interferon and serum hyporeactivity factor in mice infected with murine cytomegalovirus.

Mice injected intraperitoneally with murine cytomegalovirus produced as many as 1,000 U of serum interferon. The response appeared biphasic, with maximum titers in the first phase detectable from 2 through 4 days after infection. A second phase peaked 10 days after infection. By carboxyhexyl-Sepharose affinity chromatography, the serum interferon behaved like lymphocyte interferon. The infected mice also produced substantial quantities of serum hyporeactivity factor (D.A. Stringfellow, E.R. Kern, D.K. Kelsey, and L.A. Glasgow, J. Infect. Dis. 135:540-551, 1977), although always in the presence of interferon. This factor was separated from the serum interferon by concanavalin A-Sepharose affinity chromatography.

T-antigen expression in human skin fibroblasts is not regulated by an endogenous interferon response to SV40 infection.

Exogenous interferon may affect SV40 T-antigen expression, depending on the chromosomal complement, time of treatment, and biological factors in human cells. However, no evidence was found for endogenous interferon response to SV40 infection in the regulation of T-antigen expression.

Immunological sensitization following inapparent infection with dengue virus type 3 in rhesus monkeys.

Rhesus monkeys previously given dengue virus type 3, without apparent viremia or antibody response, exhibited a secondary-type response upon reinoculation. These data suggest that monkeys can be immunologically sensitized to dengue virus without detectable antibody production.

Chemically induced temperature-sensitive mutants of dengue virus type 2: comparison of temperature sensitivity in vitro with infectivity suckling mice, hamsters, and rhesus monkeys.

A series of temperature-sensitive (ts) mutants of dengue virus type 2 (DEN-2, TH-36 isolate) were induced by treatment with 5-azacytidine. These mutants and parental viruses were compared for the ts trait and/or attenuation in four systems: primary hamster kidney cells, suckling mice, golden Syrian hamsters, and rhesus monkeys. Seven clones judged to possess the ts trait in virto demonstrated a variety of patterns in vivo. On initial isolation, five of seven ts mutants exhibited reduced mouse lethality. The remaining two mutants possessed parental levels of mouse lethality. In hamsters, neither ts mutant nor parental viruses replicated very well, and then only when inoculated intracerebrally. Studies in rhesus monkeys indicated that all seven ts clones and parental viruses were capable of inducing abtibody responses; however, ts-1 and ts-2 failed to produce detectable viremia. After challenge with parental virus, all vaccinated monkeys demonstrated rapid secondary-type antibody response. Reversion from ts to ts(+) was confirmed to ts-1 in mice and ts-3 in monkeys, and was strongly suspected in several other instances.

Cytomegalovirus infection in children undergoing open-heart surgery.

A group of 124 children undergoing open-heart surgery was followed prospectively in order to estimate the risk of cytomegalovirus (CMV) infection due to transfused blood.Ninety-three patients (75%) had complement fixation (CF) titers of < 1:4 against CMV on admission. Of this seronegative subgroup, nine patients (9.7%) subsequently became infected with CMV. All nine showed seroconversion, and six were viruric 12-14 weeks after surgery. Comparative seroepidemiological studies of the hospital population showed that in the age ranges studied (3-16 yr), the infections seen in the study group represented a significant excess over expectation. This infection rate was consistent with a model of transmission by blood transfusion with a risk of 2.7% per unit but not proven.Thirty-one patients had CF antibody to CMV on admission. CMV was isolated from 14% of urines of seropositive children both before and after surgery, but only two patients showed CF antibody rises to CMV. Thus the frequency of CMV infection associated with open-heart surgery and transfusion could not be calculated in the seropositive subgroup.CMV infection was not related to the primary diagnosis or to Down's syndrome.

Chemically-induced temperature sensitive mutants of dengue virus type 2. I. Isolation and partial characterization.

Temperature sensitive (ts) mutants of dengue virus type 2 (DEN-2, TH-36 isolate) were induced by replication in primary hamster kidney cells treated with 5-azacytidine. Seven ts mutants were obtained from 138 clones isolated by an immunofluorescent cloning technique. Of these 7 ts mutants, 5 were sufficiently stable to permit partial characterization. Complementation was detected at very low but statistically significant levels between some ts mutants at 40 degrees C. Viral double-stranded RNA production was evaluated in LLC-MK2 cells at 30 degrees and 40 degrees C by micro-quantitative complement fixation. The results of complementation tests and RNA production tests indicated that the 4 of 5 stable ts mutants constitute 3 separate complementation groups (2 RNA+ and 1 RNA-groups), while a fifth ts mutant was RNA- but non-complementable. The data presented here indicate that a genetic system can be developed without employing traditional plaque or cytopathology methods. Further, the 5 DEN-2 ts mutants are believed to represent the only set of complementation-positive flavivirus mutants so far isolated.

Cross-protection between group B arboviruses: resistance in mice to Japanese B encephalitis and St. Louis encephalitis viruses induced by Dengue virus immunization.

Albino Swiss mice, immunized with any of several types and strains of dengue viruses, were afforded substantial protection against peripheral Japanese B encephalitis or St. Louis encephalitis virus challenge. Dengue-2 (New Guinea "C")-immunized mice showed, 10 and 20 weeks after immunization, undiminished resistance with concomitant cyclophosphamide treatment and virus challenge. Examination of the effects of immunization on Japanese B encephalitis virus pathogenesis, after virus challenge with concomitant cyclophosphamide treatment, indicated that protection was associated with decreased viremia and virtually no virus replication in the brain as compared with controls. These effects could be demonstrated before detection of any neutralizing antibody to the challenge virus. From the applied aspect, the data support the hypothesis, based on epidemiological evidence and experiments in hamsters, that prior exposure of man to dengue viruses can confer some degree of protection against Japanese B encephalitis or St. Louis encephalitis disease.