Sheena M. Loosmore

Recombinant canarypoxvirus vaccine carrying the prM/E genes of West Nile virus protects horses against a West Nile virus-mosquito challenge.

An ALVAC (canarypoxvirus)-based recombinant (vCP2017) expressing the prM and E genes derived from a 1999 New York isolate of West Nile virus (WNV) was constructed and assessed for its protective efficacy in horses in two different experiments. In the first trial, a dose titration study was conducted to evaluate both serum neutralising antibody responses to WNV and duration of immunity. In the second trial the onset of protection was determined. Twenty-eight adult horses received two doses of vCP2017 administered intramuscularly at 5-week intervals and sixteen horses comprised age-matched non-vaccinated controls. Individual sera were taken periodically and tested for neutralising antibodies against WNV. Horses were challenged by allowing WNV-infected Aedes albopictus mosquitoes to feed on them two weeks (second trial) or one year (first trial) after the second vaccination. After challenge, horses were monitored for clinical signs of disease, and blood samples were collected for detection of WNV viremia and antibody. In both trials, all vaccinated horses developed neutralising antibodies against WNV. None of the vaccinated or control horses developed clinical signs of WNV disease upon challenge. None of the nine horses challenged 2 weeks after primary vaccination and only one of the ten vaccinated horses challenged 1 year after vaccination developed detectable viremia after challenge, whereas more than 80% of the controls became infected. Results from these studies demonstrated that a primary course of two doses of vCP2017 provides both antibody response and an early immunity in horses against WNV viremia.

Recombinant Nipah Virus Vaccines Protect Pigs against Challenge

ABSTRACT Nipah virus (NiV), of the family Paramyxoviridae, was isolated in 1999 in Malaysia from a human fatality in an outbreak of severe human encephalitis, when human infections were linked to transmission of the virus from pigs. Consequently, a swine vaccine able to abolish virus shedding is of veterinary and human health interest. Canarypox virus-based vaccine vectors carrying the gene for NiV glycoprotein (ALVAC-G) or the fusion protein (ALVAC-F) were used to intramuscularly immunize four pigs per group, either with 108 PFU each or in combination. Pigs were boosted 14 days postvaccination and challenged with 2.5 × 105 PFU of NiV two weeks later. The combined ALVAC-F/G vaccine induced the highest levels of neutralization antibodies (2,560); despite the low neutralizing antibody levels in the F vaccinees (160), all vaccinated animals appeared to be protected against challenge. Virus was not isolated from the tissues of any of the vaccinated pigs postchallenge, and a real-time reverse transcription (RT)-PCR assay detected only small amounts of viral RNA in several samples. In challenge control pigs, virus was isolated from a number of tissues (104.4 PFU/g) or detected by real-time RT-PCR. Vaccination of the ALVAC-F/G vaccinees appeared to stimulate both type 1 and type 2 cytokine responses. Histopathological findings indicated that there was no enhancement of lesions in the vaccinees. No virus shedding was detected in vaccinated animals, in contrast to challenge control pigs, from which virus was isolated from the throat and nose (102.9 PFU/ml). Based on the data presented, the combined ALVAC-F/G vaccine appears to be a very promising vaccine candidate for swine.

Cloning and expression of the Haemophilus influenzae transferrin receptor genes.

The genomic transferrin receptor genes (tbpA and tbpB ) from two strains of Haemophilus influenzae type b (Hib) and two strains of non‐typable H. influenzae (NTHi) have been cloned and sequenced. The deduced protein sequences of the H. influenzae tbpA genes were 95–100% conserved and those of the tbpB genes were 66–100% conserved. The tbpB gene from one strain of NTHi was found to encode a truncated Tbp2 protein. The tbpB genes from four additional NTHi strains were amplified by the polymerase chain reaction (PCR) utilizing primers derived from the conserved N‐terminal sequences of Tbp1 and Tbp2 and were found to encode full‐length proteins. Although several bacterial species express transferrin receptors, when the Tbp1 and Tbp2 sequences from different organisms were compared, there was only limited homology. Recombinant Tbp1 and Tbp2 proteins were expressed from Escherichia coli and antisera were raised to the purified proteins. There was significant antigenic conservation of both Tbp1 and Tbp2 amongst H. influenzae strains, as determined by Western blot analysis. In a passive model of bacteraemia, infant rats were protected from challenge with Hib after transfer of anti‐rTbp2 antiserum, but not after anti‐rTbp1 antiserum.

The sequencing of the 80-kDa D 15 protective surface antigen of Haemophilus influenzae

The 80-kDa D15 antigen (D-15-Ag) has previously been shown to be a target for protective immunity and conserved amongst typeable and nontypeable Haemophilus influenzae. Here, the gene encoding D-15-Ag is shown to encode a 797-aa polypeptide which, after cleavage of the predicted signal peptide, would have a molecular mass of 85,632 Da.

Sequences of the genes encoding the A, B and C subunits of the Haemophilus influenzae dimethylsulfoxide reductase complex ☆

The genes (dms) encoding the dimethylsulfoxide reductase protein complex have been cloned and sequenced from Haemophilus influenzae (Hi) type b (Hib) strain Eagan. The Hib dms genes are arranged as an operon whose genomic organization is similar to that of the Escherichia coli (Ec) dmsABC operon. The deduced Hib DmsA, and DmsB and DmsC amino-acid sequences are highly homologous to their Ec counterparts and nearly identical to the recently published sequences of the Hi type-d strain Rd Dms proteins. Hi dimethylsulfoxide reductase appears to be a new member of the superfamily of oxidoreductase enzymes.

The New Generation of Recombinant Pertussis Vaccines

Whooping cough or pertussis is a severe, highly contagious upper respiratory tract infections, mainly affecting young children. The World Health Organization estimates that there are 60 million cases of pertussis per year and 0.5-1 million associated deaths (Muller et al., 1986). In unvaccinated populations, an incidence rate as high as 80% has been observed in children under 5 years old (Fine and Clarkson, 1984). The disease has two distinct phases, the early phase or catarrhal stage, lasts up to two weeks with symptoms of low-grade fever and mild cough. The second phase is the paroxysmal stage which can last for 4–6 weeks and is accompanied by the characteristic whoop. Infants, in particular, an suffer apnoea and hypoxaemia during these prolonged coughing bouts and there is a 5% incidence of serious neurological complications. Although pertussis is considered to be a childhood disease, there is increasing evidence of clinical and asymptomatic disease in adolescents and adults (Mortimer, 1990; Addiss et al., 1991; Halperin and Marrie, 1991). Erythromycin treatment is effective in clearing bacteria but has little effect on symptoms. Passive immunotherapy, on the other hand has been shown to reduce the frequency and severity of whoops (Granstrom et al., 1991).