Novel Vaccines to Human Rabies

Rabies, the most fatal of all infectious diseases, remains a major public health problem in developing countries, claiming the lives of an estimated 55,000 people each year. Most fatal rabies cases, with more than half of them in children, result from dog bites and occur among low-income families in Southeast Asia and Africa. Safe and efficacious vaccines are available to prevent rabies. However, they have to be given repeatedly, three times for pre-exposure vaccination and four to five times for post-exposure prophylaxis (PEP). In cases of severe exposure, a regimen of vaccine combined with a rabies immunoglobulin (RIG) preparation is required. The high incidence of fatal rabies is linked to a lack of knowledge on the appropriate treatment of bite wounds, lack of access to costly PEP, and failure to follow up with repeat immunizations. New, more immunogenic but less costly rabies virus vaccines are needed to reduce the toll of rabies on human lives. A preventative vaccine used for the immunization of children, especially those in high incidence countries, would be expected to lower fatality rates. Such a vaccine would have to be inexpensive, safe, and provide sustained protection, preferably after a single dose. Novel regimens are also needed for PEP to reduce the need for the already scarce and costly RIG and to reduce the number of vaccine doses to one or two. In this review, the pipeline of new rabies vaccines that are in pre-clinical testing is provided and an opinion on those that might be best suited as potential replacements for the currently used vaccines is offered

Transcription units of E1a, E1b and pIX regions of bovine adenovirus type 3

The major mRNA species in the E1 region of the genome of bovine adenovirus type 3 (BAV3) have been defined by using a combination of PCR, 5' RACE, Northern analysis and DNA sequencing. Independent transcription initiation sites were identified for each of the E1a, E1b and protein IX (pIX) transcription units, but all mRNA species terminated at the same poly(A) addition site immediately downstream of the pIX open reading frame. Thus, the BAV3 E1 region, which consists of the E1a and E1b genes together with that for pIX, functions as a nested overlapping transcription unit. One major mRNA species encoding the E1a protein was found and two mRNAs encoding E1b species, the smaller of which encodes the E1b 17K protein alone and the larger encodes both 17K and 47K E1b proteins, were identified. One mRNA species encodes pIX. The E1a transcript, encoding the predicted 214 residue E1a protein, has four exons. The smaller E1b mRNA has two exons, the second of which corresponds to the last exon of E1a. No introns were detected in the larger E1b mRNA that encodes both the E1b 17K and 47K proteins nor in the mRNA encoding pIX. The relative times of appearance of the mRNAs from the E1-pIX gene region following infection of bovine cells with BAV3 was determined.link_to_subscribed_fulltex

The E1 sequence of bovine adenovirus type 3 and complementation of human adenovirus type 5 E1A function in bovine cells

The bovine adenovirus type 3 (BAV3) genome was sequenced from the left end to the HindIII site at 11%. This region comprises the entire E1 transcription unit including the open reading frames (ORF) for proteins homologous to the E1A, E1B proteins and protein IX of human adenovirus type 5 (Ad5). A portion of the BAV3 E1A protein showed significant homology with conserved region 3 (CR3), the principal transactivation region of Ad5 E1A. The BAV3 E1A protein also contains a consensus sequence known to be important for interaction with the cellular Rb protein but lacks most of the sequence corresponding to the second exon of Ad5 E1A. Promoter sequences for BAV3 E1B were not defined though the relevant region contains a 35-base pair repeat sequence. Two ORFs define the BAV3 E1B coding unit; one with regions homologous to sequences within the Ad5 E1B 19k protein, and an overlapping ORF with significant homology to the Ad5 E1B 55k protein. The encoded BAV3 E1B proteins of 157 and 420 amino acid residues (R) have predicted unmodified molecular weights of 17,393 and 46,734 respectively. Immediately following the E1B coding region there is a transcription unit containing an SP1 binding site and TATA box followed by an ORF which encodes a protein of 125R and predicted molecular weight of 13,706 with homology to protein IX of Ad5. Five concensus poly A addition sites are located in the 350 base pairs immediately following the protein IX coding region. The homology of sequences in the Ad5 E1A CR3 region and the corresponding BAV3 protein suggested that the BAV3 protein could transactivate certain Ad5 genes normally transactivated by the Ad5 E1A product. Evidence for this hypothesis was obtained in studies in which bovine cells in culture were coinfected with BAV3 and a human adenovirus type 5 (Ad5) recombinant viral vector lacking the E1A region and having a lacZ reporter gene within the E3 region dependent on E1A for its expression. Coinfection resulted in the induction of β-galactosidase activity and the increased expression of other Ad5 early (E2A 72k) and late (hexon) proteins.link_to_subscribed_fulltex