Ruiming Hu

Subcutaneous Vaccination with Attenuated Salmonella enterica Serovar Choleraesuis C500 Expressing Recombinant Filamentous Hemagglutinin and Pertactin Antigens Protects Mice against Fatal Infections with both S. enterica Serovar Choleraesuis and Bordetella bronchiseptica

ABSTRACT Salmonella enterica serovar Choleraesuis strain C500 is a live, attenuated vaccine that has been used in China for over 40 years to prevent piglet paratyphoid. We compared the protective efficacies of subcutaneous (s.c.) and oral vaccination of BALB/c mice with C500 expressing the recombinant filamentous hemagglutinin type I domain and pertactin region 2 domain antigen (rF1P2) of Bordetella bronchiseptica. Protective efficacy against both S. enterica serovar Choleraesuis infection in an oral fatal challenge model and B. bronchiseptica infection in a model of fatal acute pneumonia was evaluated. Both the s.c. and oral vaccines conferred complete protection against fatal infection with the virulent parent S. enterica serovar Choleraesuis strain (C78-1). All 20 mice vaccinated s.c. survived intranasal challenge with four times the 50% lethal dose of virulent B. bronchiseptica (HH0809) compared with 4 of 20 vector-treated controls and 1 of 18 phosphate-buffered saline-treated controls that survived, but no significant protection against HH0809 was observed in orally vaccinated animals. Both the s.c. and oral vaccines elicited rF1P2-specific serum immunoglobulin G (IgG) and IgA antibodies. However, lung homogenates from s.c. vaccinated animals had detectably high levels of rF1P2-specific IgG and IgA; a much lower level of rF1P2-specific IgG was detected in samples from orally vaccinated mice, and the latter showed no evidence of local IgA. Furthermore, a more abundant and longer persistence of vaccine organisms was observed in the lungs of mice immunized s.c. than in those of mice immunized orally. Our results suggest that s.c. rather than oral vaccination is more efficacious in protecting mice from fatal challenge with B. bronchiseptica.

Novel pseudorabies virus variant with defects in TK, gE and gI protects growing pigs against lethal challenge

One of the distinct features of the emerging Chinese pseudorabies virus (PRV) variant is its ability to cause severe neurological signs and high mortality in growing pigs in Bartha-K61-vaccinated pig farms. Either single- or multiple-gene-deleted live vaccine candidates have been developed; however, none was evaluated thoroughly in growing pigs. Here, we generated rSMXΔgI/gEΔTK, an attenuated PRV variant with defects in TK, gI and gE genes. The growth kinetics of the attenuated virus was similar to the wild type (wt) strain. It was safe for 1-day-old piglets. Twenty one-day-old weaned pigs were immunized intramuscularly either with 10(6.0) TCID50 of rSMXΔgI/gEΔTK or one dose of commercial Bartha-K61 vaccine, or with DMEM, and were challenged intranasally with 10(7.0) TCID50 wt virus at 28 days post vaccination. rSMXΔgI/gEΔTK elicited higher level neutralization antibody against both PRV variant SMX and Bartha-K61 strain, while Bartha-K61 vaccine elicited lower neutralization activity of antibody against SMX. After challenge, all pigs in rSMXΔgI/gEΔTK group survived without any clinical signs, while unvaccinated group showed 100% mortality, and Bartha-K61 group showed severe respiratory symptoms and 3 out of 5 pigs exhibited severe neurological signs. Pigs in rSMXΔgI/gEΔTK group gained significantly higher body weight and diminished viral excretion titer and period, compared with Bartha-K61 group. Furthermore, the safety and efficacy of rSMXΔgI/gEΔTK was also evaluated in sheep and compared with local vaccine in growing pigs. These data suggest that the attenuated strain rSMXΔgI/gEΔTK is a promising live marker vaccine candidate for PR control in the context of emerging PRV variants.

Genetic and phylogenetic analysis of feline calicivirus isolates in China

The aim of this study was to determine the genetic diversity of Chinese feline calicivirus (FCV) isolates and their phylogenetic relationship with isolates from elsewhere in the world. Phylogenetic analysis was performed based on the partial open reading frame (ORF) 2 sequences (regions B-F) of 21 Chinese FCV isolates and 30 global isolates. The Chinese isolates included 13 isolates from Wuhan, which were isolated in this study, and eight previously published isolates. Sixteen Chinese isolates and two Japanese isolates formed a distinct phylogenetic cluster. Phylogenetic analysis based on the sequences of the complete genome, ORF1, ORF2 and ORF3 of selected isolates supported the above findings. Genogroup analysis revealed that FCV genogroup II is present in China. These findings suggest that Chinese FCV isolates are closely related to Japanese FCV isolates.

aroA deleted Bordetella bronchiseptica inspiring robust mucosal immune response and provide full protection against intranasal challenge

Bordetella bronchiseptica is a Gram-negative respiratory pathogen responsible for atrophic rhinitis and bronchopneumonia in swine. Several vaccines aimed at preventing B. bronchiseptica have been used, but a safe and efficient live vaccine for use in piglets remains elusive. In this study, we constructed an aroA-deleted B. bronchiseptica strain (QH0814) and evaluated its safety and protective efficiency in piglets. Lung lesion scores in QH0814-immunized piglets post-challenge were significantly lower than those in piglets immunized with the parent strain (P<0.05). Immunization with QH0814 induced a vigorous immune response, especially at the mucosal surface of the respiratory tract. IgA titers in bronchoalveolar lavage fluid (BALF) and serum were significantly higher in the QH0814-immunized group compared to the inactivated-vaccine-immunized group. Piglets immunized with QH0814 were better protected than those in the inactivated-vaccine and negative control groups. The clinical symptoms, histopathological changes and immune responses elicited in the piglets were recorded. The results of this study suggest that QH0814 was able to confer complete protection against B. bronchiseptica infection and could thus be used as a candidate attenuated live vaccine against B. bronchiseptica in piglets.