It turns out that there are different types of rabies virus. Let’s take a look

Rabies is a very common disease in daily life. It is generally believed that being bitten by a dog will cause this disease, and it has many different types. Precisely because it is so common, it is very necessary for people to know more about it. Only by knowing it well can they avoid being at a loss when something happens suddenly.

1. Biological characteristics

1. Morphological structure

The virus is bullet-shaped (60-400nm×60-85nm), with one end being perfectly round and the other end being flat and concave. It has a capsule and a capsid that is spirally symmetrical. The nucleic acid is single-stranded, unsegmented, negative-strand RNA.

The genome is about 12kb long, and from 3′ to 5′ there are five genes encoding N, M1, M2, G, and L proteins, and there are non-coding spacer sequences between each gene. All five proteins are antigenic. The M1 and M2 proteins constitute the matrix of the capsid and capsule, respectively. The L protein is a polymerase. The G protein forms the viral spike on the envelope and is related to the pathogenicity of the virus. The N protein is a nucleoprotein that has the function of protecting RNA. G protein and N protein are the main antigens of rabies virus, which can stimulate the body to induce corresponding antibodies and cellular immunity. In the past, it was believed that G protein was the only antigen that could induce neutralizing antibodies and provide protective immunity against rabies. Recent studies have shown that in addition to G protein, the virus's ribonucleoprotein (RNP) also plays an important role in inducing protective immune responses.

2. Cultivation

The rabies virus has a wide host range and can infect mice, rabbits, guinea pigs, horses, cattle, sheep, dogs, cats, etc. It invades and proliferates in central nervous cells (mainly pyramidal cells in the hippocampus of the brain), and can form eosinophilic inclusion bodies (Negri bodies) in the cytoplasm. It can be cultured and proliferated in human diploid cells, hamster kidney cells, chicken embryos, and duck embryos, and can be used to prepare tissue culture vaccines.

3. Antigenic type and variation

There is only one serotype of rabies virus, but its virulence can vary. The virus strain isolated from naturally infected animals is called wild strain or street strain. It has strong pathogenicity and can easily invade brain tissue and salivary glands when inoculated outside the brain. After the wild strain was propagated in the rabbit's brain for 50 consecutive generations, the rabbit's disease incubation period gradually shortened from 2 to 4 weeks to 4 to 6 days. If it is no longer shortened after continued propagation, it is called a fixed strain. The fixed strain has weak pathogenicity to humans and animals. It will not invade the brain and proliferate after extracerebral inoculation and will not cause rabies. Pasteur was the first to use fixed strains to make attenuated live vaccines to prevent rabies.

4. Resistance

The rabies virus has weak resistance to heat, ultraviolet rays, sunlight, and dryness. It will die if heated to 50°C for one hour or 60°C for five minutes. It is also easily inactivated by strong acids, strong alkalis, formaldehyde, iodine, acetic acid, ether, soapy water, and ionic and non-ionic detergents. It can be stored at 4°C for one week. If placed in 50% glycoside oil at room temperature, it can remain active for 1 week.

2. Classification of rabies

The rabies virus genus can be divided into four serotypes by serological methods. Type I viruses include CVS prototype strains, classical RV, street viruses and vaccine strains. Serotype II, III and IV viruses are rabies-related viruses, and their prototype strains are Lagos bat, Mokola and Duvenhage viruses, respectively.

In 1993, Bourhy et al. divided the lyssavirus genus into six genotypes based on the homology of the 500 bases at the N-terminus of the nucleoprotein gene: genotypes 1 to 4 correspond to serotypes I to IV, respectively, and the two strains of European rabies virus EBLV-1 and EBLV-2 isolated from bats in Germany and Finland are genotypes 5 and 6. In July 1996, Australia reported the first discovery of Lyssavirus in fruit bats, which was identified as genotype 7, namely ABLV. The Aravan virus was isolated from the small mouse-eared bat (Myotis blythi) in Kyrgyzstan, Central Asia. Analysis of its N gene and deduced amino acid sequence revealed that it was significantly different from the seven known genotypes of the virus. MAbs detected that its antigenic characteristics were also different from those of other types of viruses. Therefore, some people believe that this is a new genotype.