Anti-VEEV polyclonal antibody

Venezuelan equine encephalitis (VEE) is a zoonosis caused by the Venezuelan equine encephalitis virus (VEEV) that affects humans, horses and other animals. VEEV is a mosquito-borne RNA virus. Equines are the amplifying hosts of the virus, which is mainly transmitted by mosquito bites. In addition to natural routes of infection, VEEV can also be transmitted by aerosol. The globalisation of economic trade has increased the potential for the spread of VEE. There is currently no FDA-approved vaccine or effective antiviral drug for VEEV. Therefore, there is an urgent need for a rapid and effective method to detect VEEV. Since its discovery, VEE has experienced several outbreaks, causing huge economic losses to the countries and regions where the epidemic occurred and seriously threatening public safety.

Figure 1. Transmission cycles of venezuelan equine encephalitis viruses (VEEV).(Sources: Ronca SE, et al. 2016)

VEEV can infect humans and equine animals. Infected horses can serve as amplification hosts and become an important source of infection for the disease. VEEV is mainly transmitted through mosquito bites and can also be transmitted through aerosols. It is considered one of the potentially dangerous biological weapons. Horse-mosquito-horse is the main mode of transmission of VEEV epidemic strains. Humans can be infected through contact and are considered to be the final host of VEEV. The incidence of human infection with VEEV is high, and the mortality rate is low. Most infected people experience clinical symptoms such as headache, fever, muscle pain, physical weakness, and varying degrees of encephalitis. The incubation period of VEEV in the human body is 2-5 days; after infection, neurological diseases will occur, and 4% to 14% of individuals with symptoms will have permanent neurological sequelae. A small number of patients, especially children, may experience encephalitis symptoms such as tremors and diplopia. The mortality rate of sick children can be as high as 10%. After horses are infected with a strong strain of VEEV, they may develop viremia within 24-48 hours and last for about 2-3 days, and develop anorexia, fever, diarrhea and other clinical symptoms. Most infected horses will show central nervous system symptoms such as increased stress, aimless circling, refusal to eat and banging against walls or stables.

VEEV is a member of the genus Alphavirus in the family Togaviridae. The members of the genus Alphavirus also include more than 30 viruses such as Eastern Equine Encephalitis Virus (EEEV), Chikungunya Virus (CHIKV), and Western Equine Encephalitis Virus (WEEV). VEEV is not a single virus, but a complex group of viruses with obvious virulence differences, especially antigenic differences, including 6 antigen-related subtypes (I, II, III, IV, V, VI), namely VEEV, Everglades, Mucombo, Pixuna, Cabassou, and AG80663. Among them, subtype I includes 5 types (I AB, I C, I D, I E, I F), subtype III includes 3 types (III A, III B, III C), and I AB and I C are the main pathogens. The remaining local strains of VEEV include VEEV I D, VEEV I E and subtypes II-VI, which mainly cause local sporadic occurrences of VEE. VEEV is a single-stranded positive-strand RNA virus with a virus particle diameter of about 70nm, a nucleocapsid with icosahedral symmetry, and neurotropic. The VEEV genome is about 11.4kb in length and contains 2 open reading frames, encoding five structural proteins (C, E3, E2, 6K and E1) and four non-structural proteins (nsP1, nsP2, nsP3, nsP4). Among them, E1 and E2 glycoproteins contain the main antigenic epitopes of the virus, and the E2 protein can stimulate the body to produce neutralizing antibodies. E3 and 6K play an important role in the assembly of virus particles. Currently, the main detection methods for VEEV include antibody detection method, antigen detection method and nucleic acid detection method, so the appropriate detection method should be selected according to the actual situation. Virus isolation and identification are the most common and accurate detection methods for viral diseases, but VEEV isolation is time-consuming and laborious, and virus isolation must be performed in a BSL-3 (Biosafety Level 3) laboratory. Detection by haemagglutination inhibition can save time, but this method requires fresh blood for detection and its sensitivity is poor. The "gold standard" for VEEV antibody detection is the plaque reduction neutralisation test (PRNT), but this detection method requires live virus and specific antibodies, and live virus cannot be run under normal laboratory conditions. Biological diagnostic methods such as RT-PCR and loop-mediated isothermal amplification PCR are highly sensitive and specific, but require precision equipment and skilled personnel, have high environmental requirements and are prone to contamination.

Venezuelan Equine Encephalitis Virus
VEE