Ethylenimine-inactivated rabies vaccine of tissue culture origin

Evaluation of Different Stabilizers and Inactivating Compounds for the Enhancement of Vero Cell Rabies Vaccine Stability and Immunogenicity: In Vitro Study

Inactivation of rabies virus is essential for rabies vaccine preparation where the inactivating compound that is currently recommended for rabies vaccine preparation is β-propiolactone (β-PL). This compound is considered better than phenol and formalin but it is expensive and potentially carcinogenic. Data revealed that Ascorbic acid (AA) with cupric ions could yield complete and irreversible inactivation of rabies virus without adversely affecting its antigenicity. Additionally, the results of testing the vaccine potency with the selected inactivating compounds were comparable (P<0.05), and ED50 was higher than the recommended World Health Organization (WHO) limits. The use of HemaGel (plasma substitute) for testing vaccine stabilization was compared with the currently used vaccine stabilizers (human albumin and lactose). HemaGel yielded better stability than the other tested stabilizers. Monitoring of cellular and humoral immune responses indicated that both the total IgG level against rabies vaccine and the IFN and IL5 levels obtained with the HemaGel-stabilized vaccines were higher than those obtained with human albumin- and lactose-stabilized vaccine candidates.

Inactivated infectious haematopoietic necrosis virus (IHNV) vaccines

The inactivation dynamics of infectious haematopoietic necrosis virus (IHNV) by b-propiolactone (BPL), binary ethylenimine (BEI), formaldehyde or heat and the antigenic and immunogenic properties of the inactivated vaccines were evaluated. Chemical treatment of IHNV with 2.7 mm BPL, 1.5 mm BEI or 50 mm formaldehyde abolished virus infectivity within 48 h whereas heat treatment at 50 or 100 degrees C rendered the virus innocuous within 30 min. The inactivated IHNV vaccines were recognized by rainbow trout, Oncorhynchus mykiss, IHNV-specific antibodies and were differentially recognized by antigenic site I or antigenic site II IHNV glycoprotein-specific neutralizing monoclonal antibodies. The BPL inactivated whole virus vaccine was highly efficacious in vaccinated rainbow trout challenged by waterborne exposure to IHNV 7, 28, 42 or 56 days (15 degrees C) after immunization. The formaldehyde inactivated whole virus vaccine was efficacious 7 or 11 days after vaccination of rainbow trout but performed inconsistently when tested at later time points. The other vaccines tested were not efficacious.

Antibody-secreting cell responses and protective immunity assessed in gnotobiotic pigs inoculated orally or intramuscularly with inactivated human rotavirus

Newborn gnotobiotic pigs were inoculated twice perorally (p.o.) (group 1) or intramuscularly (i.m.) (group 2) or three times i.m. (group 3) with inactivated Wa strain human rotavirus and challenged with virulent Wa human rotavirus 20 to 24 days later. To assess correlates of protection, antibody-secreting cells (ASC) were enumerated in intestinal and systemic lymphoid tissues from pigs in each group at selected postinoculation days (PID) or postchallenge days. Few virus-specific ASC were detected in any tissues of group 1 pigs prior to challenge. By comparison, groups 2 and 3 had significantly greater numbers of virus-specific immunoglobulin M (IgM) ASC in intestinal and splenic tissues at PID 8 and significantly greater numbers of virus-specific IgG ASC and IgG memory B cells in spleen and blood at challenge. However, as for group 1, few virus-specific IgA ASC or IgA memory B cells were detected in any tissues of group 2 and 3 pigs. Neither p.o. nor i.m. inoculation conferred significant protection against virulent Wa rotavirus challenge (0 to 6% protection rate), and all groups showed significant anamnestic virus-specific IgG and IgA ASC responses. Hence, high numbers of IgG ASC or memory IgG ASC in the systemic lymphoid tissues at the time of challenge did not correlate with protection. Further, our findings suggest that inactivated Wa human rotavirus administered either p.o. or parenterally is significantly less effective in inducing intestinal IgA ASC responses and conferring protective immunity than live Wa human rotavirus inoculated orally, as reported earlier (L. Yuan, L. A. Ward, B. I. Rosen, T. L. To, and L. J. Saif, J. Virol. 70:3075-3083, 1996). Thus, more efficient mucosal delivery systems and rotavirus vaccination strategies are needed to induce intestinal IgA ASC responses, identified previously as a correlate of protective immunity to rotavirus.

Production and partial characterization of monoclonal antibodies to four Chlamydia psittaci isolates

Monoclonal antibodies (MAbs) were produced to four Chlamydia psittaci isolates: NJ1 and TT3 from turkeys, VS1 from a parakeet, and B577 from an ovine abortion. MAbs were tested for reactivity with each isolate by the indirect immunofluorescent antibody technique and for neutralization by an inclusion reduction neutralization technique in tissue culture. Two genus-specific and 14 serovar-specific MAbs were produced. Genus-specific MAbs reacted with all avian and mammalian isolates; however, each failed to neutralize its homologous chlamydial isolate. Turkey isolates NJ1 and TT3 were antigenically similar; serovar-specific MAbs produced to each reacted equally with both isolates yet showed little or no reaction with other serovars. Serovar-specific MAbs to the parakeet and abortion isolates were distinct; no cross-reactions were seen with other serovars. None of the serovar-specific MAbs reacted with an ovine arthritis isolate. Of the 14 serovar-specific MAbs, 13 partially neutralized homologous strains with or without the addition of complement. Because of the high specificity, the serovar-specific MAbs used with the immunofluorescence technique provided a rapid and precise method to identify three serovars of C. psittaci.

Cross protection of mice against different rabies virus isolates

In an attempt to identify "atypical" strains which could account for vaccination failures, 10 street, one intermediate (DR19) and 4 fixed rabies virus isolates from men, cattle, dogs, cats, mongoose and vampire bats in five countries (Argentina, Brazil, Chile, Cuba, and France) were studied by cross-protection tests in mice. For the purpose of this study, any virus that killed more than 20% of the vaccinated mice challenged with that virus was considered "atypical". When the suckling mouse brain rabies vaccine was used, two "atypical" isolates were found: one, from a human case in Chile (91, 125 mouse passages) and the other, from a vampire bat in Brazil (DR19, 22 mouse passages). However, when mice immunized with a cell culture vaccine (PV-BHK) of a higher antigenic value than the brain vaccine, were challenged with those same isolates, mortality was below 20%. The fact that these two isolates killed enough vaccinated mice to be considered "atypical" could be related to antigenic differences between these viruses and those included in the vaccine. However, since this mortality was observed only in the mice immunized with the vaccine with a lower antigenic value, reasons are given why it could be attributed to other biological characteristics of those strains than antigenic differences. Causes for vaccines failures other than immunological differences of rabies virus strains are also analyzed and discussed.

Rabies virus inactivation by binary ethylenimine: new method for inactivated vaccine production

The inactivation dynamics of rabies virus (PV strain) by binary ethylenimine, and the immunogenic properites and the stability of the vaccines prepared using this agent, were studied. Binary ethylenimine at a final concentration of 0.01 M was prepared wtih 2-bromoethylamine hydrobromide in alkaline solutions, either separately from or in suspensions of rabies virus propagated in BHK cells. The infectivity of virus suspensions containing more than 108 plaque-forming units per 0.1 ml was inactivated in 2 h when the inactivating agent was prepared before its addition to the suspensions, and in3 h when prepared directly in the suspensions. Liquid vaccines prepared in this manner and stored at different temperatures maintained potency for 1 month at 37 degrees C and for 6 months at 4 degrees C and 22 to 25 degrees C. Lyophilized vaccine maintained its potency for 6 months at the three temperatures. The inactivated vaccine mixed with aluminum or oil adjuvant at high dilutions protected guinea pigs against challenge. This safer procedure for rabies virus inactivation offers promise for the production of effective vaccines for the immunization of dogs and cattle.