Hepatitis A Virus Vaccines
Creative Biolabs is a world leader in the field of viral vaccine development. With our extensive experience and advanced platform, we are therefore confident in offering the best vaccine development services for Hepatitis A Virus. We guarantee the finest results for our customers all over the world.
Hepatitis A is an infectious disease of the liver caused by the Hepatitis A Virus (HAV). Globally, around 1.4 million symptomatic cases occur each year and about 114 million infections (symptomatic and asymptomatic). It is more common in regions of the world with poor sanitation and not enough safe water. In the developing world, about 90% of children have been infected by age 10, thus are immune by adulthood. It often occurs in outbreaks in moderately developed countries where children are not exposed when young. The hepatitis A vaccine should be an effective way for prevention.
The Pathogenesis of Hepatitis A Virus Infection
The mechanisms underlying liver injury in hepatitis A are not understood. The initial non-cytopathic phase, during which virus replicates and is released, is followed by decreased virus multiplication and inflammatory cell infiltration, suggesting that immune mechanisms are involved in pathogenesis. Experimental evidence suggests that HLA-restricted, virus specific T cells play a significant role in HAV-related hepatocellular injury. T cell clones have been derived from patients with acute hepatitis A and analyzed for their phenotype. CD8+ clones isolated during the acute phase of the disease predominate over CD4+ clones; these CD8+ clones have cytotoxic activity and show specific cytotoxicity against autologous fibroblasts infected with HAV. These data support the hypothesis that liver cell injury in acute HAV infection is mediated by HAV-specific CD8+ T lymphocytes and is not entirely due to an intrinsic cytopathic effect of the virus itself. The molecular targets of these cells are unknown.
Fig.1 The facts of Hepatitis A Virus.
Prevention and Control of Hepatitis A Virus
Control of infection is difficult. Strict isolation of cases is not a useful control measure because faecal shedding of the virus is at its highest during the late incubation period and prodromal phase of the illness. Normal human immunoglobulin (NHIG), containing at least 100 IU/ml anti-HAV, will prevent or attenuate a clinical illness if given intramuscularly before exposure to the virus or early during the incubation period. However, immunoglobulin does not always prevent infection and excretion of HAV, and inapparent or subclinical hepatitis may develop. Although there is some sequence variation between different isolates of HAV and evidence for different strains infecting non-human primates, there is only one serotype of the virus and immunity gives effective cross-protection against all strains. Based on that, there has been considerable interest in the development of both killed and attenuated hepatitis A vaccines and inactivated vaccines are now licensed in many countries.
The Development of HAV Vaccines
Inactivated hepatitis A vaccines contain viral particles that are produced in cell culture, purified, inactivated with formalin, and adsorbed to an aluminum hydroxide adjuvant. Inactivated HAV vaccines are highly immunogenic and protect against both infection and disease. This protection is likely primarily antibody based and is broadly directed against all strains of HAV, consistent with the identification of a single serotype of HAV among human strains.
Candidate live, attenuated HAV vaccines have been developed using viruses that have been adapted to growth in cell culture. There was considerable enthusiasm for such vaccines early in the development process, but vaccine candidates were poorly immunogenic. Attenuation seems to have been achieved with these viruses at the cost of their ability to replicate within the liver, not by adaptation to a site of replication within the body that is different from that at which the virus causes disease. Nonetheless, a live, attenuated hepatitis A vaccine has received relatively wide use in China and appears capable of inducing protective levels of antibody. A study conducted in children suggested that a single dose of this vaccine was approximately 95% effective in preventing overt disease, but that it was less effective in preventing asymptomatic infection during an outbreak of hepatitis A. Whereas an attenuated vaccine might have some advantages, inactivated vaccines work well.
Creative Biolabs is pleased to share our cutting-edge technology and extensive expertise in the field of Hepatitis A Virus vaccine development and has focused on the viral vaccines for years. We can offer high-quality customized services by adjusting protocols to meet even the most specific requirements. If you are interested in our services, please contact us for more details.
References
- Donato F. (2002). “Alcohol and hepatocellular carcinoma: the effect of lifetime intake and hepatitis virus infections in men and women”. American journal of epidemiology, 155(4), 323-331.
- Martin A. (2006). “Hepatitis A virus: from discovery to vaccines.” Hepatology. 43(2 Suppl 1), S164-72.
All of our products can only be used for research purposes. These vaccine ingredients CANNOT be used directly on humans or animals.
