Similar evidence of exposure to hepatitis E virus or related agents also has been documented in primates and swine. To explore the nature of these infections in pigs, Xiang-Jin Meng, M.D., Ph.D., working with Dr. Purcell and their LID colleague Suzanne U. Emerson, Ph.D., screened swine blood samples with an assay designed to detect antibodies to strains of human hepatitis E virus. Most of the samples, taken from swine herds in the Midwestern United States, tested positive for hepatitis E virus antibodies. None of the piglets, however, showed any clinical signs of disease after seroconversion. They found that the swine virus was closely related to, but distinct from, human strains of the virus.
Amino acids are the molecules from which proteins are made.
Among most human strains of hepatitis E virus, amino acid identity is between 97 and 99 percent. The researchers say their findings strongly suggest that a previously unrecognized strain of hepatitis E virus circulates in the swine population. Still, further studies are needed to determine whether swine hepatitis E virus is species- specific or is circulating in the human population without causing disease. These subclinical infections of humans with swine hepatitis E virus might explain the relatively high prevalence of hepatitis E antibodies in healthy individuals in the United States. If that were the case, says Dr. Meng, the strong immunologic cross-reactivity of the swine and human strains suggests that swine hepatitis E virus could prove useful as a vaccine against the human virus.