Comparison of mouse, guinea pig and rabbit models for evaluation of plague subunit vaccine F1 + rV270
Introduction
Plague is a zoonotic disease caused by Gram-negative bacterium Yersinia pestis, which is usually transmitted to humans from infected rodents via the bite of an infected flea [1]. Three human plague pandemics have been responsible for more deaths than any other infectious agents, as far as we know, in human history. Recently plague has attracted a considerable attention because of its potential use as an agent of biological warfare or bioterrorism. Plague represents three main clinical forms, bubonic, septic and pneumonic, depending on how the bacteria enter into and spread within the body [2]. Patients with bubonic plague can develop highly infectious pneumonic form that can be spread from person-to-person via respiratory droplets generated from sneezing and coughing of the patients. Due to the high infectivity and mortality of plague, there is urgent need to develop vaccines for protecting people.
The plague vaccine USP [3], a formaldehyde-killed whole-cell vaccine derived from the virulent 195/P strain of Y. pestis, was previously licensed in the U.S.A., but its production was discontinued in 1999 because it was not effective against pneumonic plague. The only currently available plague vaccine CSL, a heat-killed whole-cell vaccine derived from the 195/P strain of Y. pestis, was licensed for use in Australia, which appears to have similar properties to the USP vaccine [4]. Y. pestis live attenuated vaccine EV76, a mutant of the virulent strain that has lost the pgm locus, was developed from a virulent strain isolated from a plague patient in Madagascar by five-year's subculture, and protected against higher challenge doses than the killed vaccine USP, but this vaccine showed side effects of varying severity and was not currently used in the Western world [3], [5], [6]. The DNA vaccine based on Y. pestis F1 and LcrV antigen alone or in combination was efficacious against both bubonic and pneumonic plague [7], [8], [9]. However, immunization with plasmid DNA causes novel safety issues [10]. In contrast, subunit vaccines have obvious advantages over the live attenuated vaccine and DNA vaccine in terms of safety of use. In this regard, a subunit vaccine is likely to offer the best near-term solution to the provision of a vaccine that protects against both bubonic and pneumonic plague [11].
At present, plague subunit vaccines are being developed mainly based on the combination of F1 and LcrV or a fusion protein of these two antigens [12], which have been reported widely for their efficacy to protect mice [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], guinea pigs [24] and primates [25], [26]. It has been shown that LcrV antigen suppresses host innate immune functions by stimulating the release of interleukin 10 (IL-10) and preventing the release of proinflammatory cytokines, such as gamma interferon (IFN-γ) or tumor necrosis factor alpha (TNF-α) [27], [28], [29], [30]. Recently, an LcrV variant lacking amino acid residues 271–300 (rV10), compared with full-length LcrV, displayed a reduced immunosuppressive function [31]. In order to develop a safe and effective subunit vaccine for plague, a recombinant protein lacking amino acids 271–326 of LcrV (referred to as rV270 in this paper) was expressed in Escherichia coli BL21 [32] and the high-purity native F1 antigen was also prepared from Y. pestis EV76 [33].
In this study, the protective efficacy of the F1 + rV270 vaccines in protecting mice against subcutaneous challenge with a virulent Y. pestis 141 strain was evaluated in comparison with that of the EV76 vaccine. The antibody titres induced by different weight ratio of F1 + rV270 vaccines in BALB/c model were determined and compared with each other. An optimal formulation of F1 + rV270 was screened based on the titres elicited by candidate subunit vaccines in Balb/c model. Then, the optimal formulation of F1 + rV270 was tested in guinea pigs and New Zealand White rabbits by determining their antibody titres and protective efficacy against subcutaneous challenge with a virulent Y. pestis 141 strain.
Section snippets
Animals
Female BALB/c mice of 6–8 weeks, female guinea pigs of 6–8 weeks and New Zealand White rabbits of 1.5–2 kg raised under specific-pathogen-free conditions were used in this study. All the animals were group-housed and provided with food and fresh water ad libitum during the study. All animal experiments were conducted in accordance with the Guidelines for the Welfare and Ethics of Laboratory Animals of China.
Vaccines
The native F1 antigen was prepared from Y. pestis EV76 by physical disruption, followed
Antibody responses to the vaccines in different animals
The titres of anti-F1 and anti-rV270 specific antibodies in all immunized and control mice were determined on weeks 6, 8, 10, 12, 14, 16 and 18 after primary immunization. The geometric mean of antibody titres from each group of 10 mice and the standard error of the mean were calculated from the data obtained by ELISA (Supplementary Table S1). The immunized mice with subunit vaccines I to VIII developed higher titres of circulating IgG to both F1 and rV270 than those immunized with EV76
Discussion
In this study, we examined one-dose and two-dose of immunization regimens of native F1 plus recombinant rV270 vaccine at the same dosage level by using mouse, guinea pig and rabbit model. Groups of mice receiving two-dose of subunit vaccines had a significant stronger IgG response than those given one-dose of them. However, there was no significant IgG titre difference between the mice given a single dose of EV76 vaccine and those receiving two-dose of it. These results showed that subunit
Acknowledgments
Financial support for this study came from the National High Technology Research and Development Program of China (863 program) (contract no. 2006AA02Z438). We are grateful to Dr. Wei Liu for her assistance in statistical analysis.
References (53)
- et al.
A comparison of Plague vaccine, USP and EV76 vaccine induced protection against Yersinia pestis in a murine model
Vaccine
(1995) - et al.
Inducing systemic and mucosal immune responses to B-T construct of F1 antigen of Yersinia pestis in microsphere delivery
Vaccine
(2006) - et al.
A Salmonella enterica serovar Typhi vaccine expressing Yersinia pestis F1 antigen on its surface provides protection against plague in mice
Vaccine
(2004) - et al.
A DNA vaccine producing LcrV antigen in oligomers is effective in protecting mice from lethal mucosal challenge of plague
Vaccine
(2004) - et al.
Protection against plague afforded by immunisation with DNA vaccines optimised for expression of the Yersinia pestis V antigen
Vaccine
(2004) - et al.
Identification of immunodominant epitope of F1 antigen of Yersinia pestis
FEMS Immunol Med Microbiol
(2000) - et al.
Effect of homologous and heterologous prime-boost on the immune response to recombinant plague antigens
Vaccine
(2005) - et al.
Protective efficacy of a recombinant plague vaccine when co-administered with another sub-unit or live attenuated vaccine
FEMS Immunol Med Microbiol
(2005) - et al.
Protection studies following bronchopulmonary and intramuscular immunisation with yersinia pestis F1 and V subunit vaccines coencapsulated in biodegradable microspheres: a comparison of efficacy
Vaccine
(2000) - et al.
Respiratory immunity is an important component of protection elicited by subunit vaccination against pneumonic plague
Vaccine
(2006)
Purification and protective efficacy of monomeric and modified Yersinia pestis capsular F1-V antigen fusion proteins for vaccination against plague
Protein Expr Purif
Protection conferred by a fully recombinant sub-unit vaccine against Yersinia pestis in male and female mice of four inbred strains
Vaccine
Intranasal Protollin/F1-V vaccine elicits respiratory and serum antibody responses and protects mice against lethal aerosolized plague infection
Vaccine
A single dose sub-unit vaccine protects against pneumonic plague
Vaccine
Kinetics of the immune response to the (F1 + V) vaccine in models of bubonic and pneumonic plague
Vaccine
Protective efficacy of a fully recombinant plague vaccine in the guinea pig
Vaccine
A new purification strategy for fraction 1 capsular antigen and its efficacy against Yersinia pestis virulent strain challenge
Protein Expr Purif
Yersinia pestis Yop secretion protein F: purification, characterization, and protective efficacy against bubonic plague
Protein Expr Purif
Immunogenicity of the rF1 + rV vaccine for plague with identification of potential immune correlates
Microb Pathog
Yersinia pestis—etiologic agent of plague
Clin Microbiol Rev
Plague: from natural disease to bioterrorism
Proc (Bayl Univ Med Cent)
A new improved sub-unit vaccine for plague: the basis of protection
FEMS Immunol Med Microbiol
Effective protective immunity to Yersinia pestis infection conferred by DNA vaccine coding for derivatives of the F1 capsular antigen
Infect Immun
Ensuring safety of DNA vaccines
Microbial Cell Factories
Yersinia pestis (plague) vaccines
Expert Opin Biol Ther
Oral vaccination against bubonic plague using a live avirulent Yersinia pseudotuberculosis strain
Infect Immun
Cited by (0)
- 1
Both contributed equally to this work.