Protection from infection with severe acute respiratory syndrome coronavirus in a Chinese hamster model by equine neutralizing F(ab')2.

To warrant potential clinical testing, the equine anti-severe acute respiratory syndrome coronavirus (SARS-CoV) F(ab')(2) requires evaluation in as many animal models as possible. In this study, we established a new animal model, the Chinese hamster, susceptible to SARS-CoV infection. SARS-CoV could propagate effectively and sustain high levels for 1 wk in animal lungs. All animals were protected from SARS-CoV infection in preventive settings. Further, when used therapeutically this antibody led to an approximately 4-log(10) decrease in viral burden in infected animal lungs. The pathological changes in lungs correlated closely with the dose of antibody administered. The excellent preventive and therapeutic roles of equine anti-SARS-CoV F(ab')(2) in several animal models, including the novel Chinese hamster model described in this study, have provided exciting data concerning its potential clinical study.

Inhibition of infection caused by severe acute respiratory syndrome-associated coronavirus by equine neutralizing antibody in aged mice.

The high susceptibility of elderly to severe acute respiratory syndrome-associated coronavirus (SARS-CoV) indicates how crucial it is to protect the elderly by various strategies. Aged BALB/c mice displayed a high susceptibility to SARS-CoV and have been a valuable platform for evaluation of strategies against SARS-CoV infection. In this study, we confirmed the validity of this model using various methods, and verified that equine anti-SARS-CoV F(ab')(2) can prevent aged animals from SARS-CoV infection. In a therapeutic setting, treatment with anti-SARS-CoV F(ab')(2) decreased viral load more than several thousand folds in the lungs. Thus, this antibody should be a potential candidate for treatment of elderly patients suffering from SARS.

Protective immunity elicited by a divalent DNA vaccine encoding both the L7/L12 and Omp16 genes of Brucella abortus in BALB/c mice.

This study was designed to evaluate the immunogenicity and the protective efficacy of a divalent fusion DNA vaccine encoding both the Brucella abortus L7/L12 protein (ribosomal protein) and Omp16 protein (outer membrane lipoprotein), designated pcDNA3.1-L7/L12-Omp16. Intramuscular injection of this divalent DNA vaccine into BALB/c mice elicited markedly both humoral and cellular immune responses. The specific antibodies exhibited a dominance of immunoglobulin G2a (IgG2a) over IgG1. In addition, the dual-gene DNA vaccine elicited a strong T-cell proliferative response and induced a large amount of gamma interferon-producing T cells upon restimulation in vitro with recombinant fusion protein L7/L12-Omp16, suggesting the induction of a typical T-helper-1-dominated immune response in vivo. This divalent DNA vaccine could also induce a significant level of protection against challenge with the virulent strain B. abortus 544 in BALB/c mice. Furthermore, the protection level induced by the divalent DNA vaccine was significantly higher than that induced by the univalent DNA vaccines pcDNA3.1-L7/L12 or pcDNA3.1-Omp16. Taken together, the results of this study verify for the first time that the Omp16 gene can be a candidate target for a DNA vaccine against brucellosis. Additionally, a divalent genetic vaccine based on the L7/L12 and Omp16 genes can elicit a stronger cellular immune response and better immunoprotection than the relevant univalent vaccines can.

Protection of mammalian cells from severe acute respiratory syndrome coronavirus infection by equine neutralizing antibody.

The aetiological agent for severe acute respiratory syndrome (SARS) has been determined to be a new type of coronavirus (SARS-CoV) that infects a wide range of mammalian hosts. Up to now, there have been no specific drugs to protect against SARS-CoV infection, thus developing effective strategies against this newly emerged viral infection warrants urgent efforts. Adoptive immune therapy with pathogen-specific heterologous immunoglobulin has been successfully used to control the dissemination of many viral infections. To investigate whether a neutralizing antibody against SARS-CoV raised in an artiodactylous host can have a protective role on primate cells, we prepared serum IgGs and their pepsin-digested F(ab')2 fragments from horses inoculated with purified SARS-CoV (BJ-01 strain). The protective effect of the F(ab')2 fragments against SARS-CoV infection was determined in cultured Vero E6 cells by cytopathic effect (CPE), MTT and plaque-forming assays and in a Balb/c mouse model by CPE and quantitative RT-PCR. The results showed the neutralization titres of F(ab')2 from three horses all reached at least 1:1600, and 50 microg of the F(ab')2 fragments could completely neutralize 1x10(4) TCID50- SARS-CoV in vivo. Additionally, we observed that F(ab')2, against BJ-01 strain could also protect cells from infection by the variant GZ-01 strain in vitro and in vivo. Our work has provided experimental support for testing the protective equine immunoglobulin in future large primate or human trials.

[Conditions for SARS-CoV cultivation and inactivation].

OBJECTIVE: To study the method for cultivation and inactivation of SARS-CoV. METHODS: In order to choose the sensitive cell strain and the best infection dose of the virus, Vero, Vero-E6 and 2BS cell lines were infected with SARS-CoV. The cultivation temperature was selected among 25 degrees C, 33 degrees C and 37 degrees C. The best inactivating time and effect were observed with beta-propiolactone whose concentration ranged from 1:2000 to 1:20,000 at room temperature. RESULTS: Vero and Vero-E6 cell lines were sensitive to SARS-CoV. The cytopathic changes of the cells were 75% at 37 degrees C in 5 percent CO2 incubator after infection. SARS-CoV was inactivated completely in beta-propiolactone (1:4000). The toxicity of beta-propiolactone was hydrolyzed completely when the inactivated virus was cultured for 16 hours at 2 degrees C, 8 degrees C and in water bath for 2 hours at 37 degrees C. CONCLUSION: The titer of SARS-CoV was the highest when it was cultured in Vero or Vero-E6 cells for 72 hours at 37 degrees C in 5 percent CO2 incubator. SARS-CoV was inactivated completely in beta-propiolactone when its concentration was 1:4000 and the interaction time was 1 hour.