Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/2010
Publication Date: 7/20/2010
Citation: Kingsley,D.,Provost,K.,Anderson,R.,Ozbay,G.2010.Retention of enteric viruses by the hemocytes of the Eastern Oyster (Crassostrea virginica)[abstract].IFT Annual Meeting.Chicago,IL.p.1. Interpretive Summary:
Technical Abstract: Virus accumulation and persistence in bivalve mollusks has long been documented in the United States and also throughout the world. Shellfish are an important vector for transmission of enteric pathogens. Interventions, such as depuration, do not adequately clear oysters of virus, while fecal bacteria levels are significantly reduced. Why viruses are retained in the bivalve flesh is not well understood. We hypothesize that phagocytic cells of the oyster (hemocytes) play an important role for the retention of virus particles within bivalves. Multiple studies were undertaken in an effort to address the question of the hemocytes’ role in virus retention. Firstly, hemocytes were separated from the hemolymph and results indicated that hepatitis A virus (HAV) is hemocyte cell-associated, and the persistence times of hemocytes in oysters correlates with the presence of HAV within hemocytes. Second, a transfer of HAV-contaminated hemocytes to virus-free oysters indicated that the contaminated hemocytes both survived the transfer and retained HAV for up to 2 weeks. Since the process of phagocytized virus would likely result in sequestration of viruses within the phagolysome of the hemocyte, several viruses of differing acidic pH tolerance were evaluated to see if this property relates to the ability of the virus to persist within oysters. Arranged by longest to shortest persistence, we found that the order of peristence for the viruses tested to be HAV, poliovirus (PV), murine norovirus (MNV), and feline calicivirus (FCV). We found viability within increasingly acidic buffer to have the same order as acid tolerance, with HAV persisting the longest in shellfish tissues and having limited titer reduction after exposure to pH 2, while FCV does not readily persist within bivalves or tolerate low pH exposure. MNV and PV both displayed intermediate persistence times and intermediate tolerances to low pH buffer. Antiviral activity of hemocytes was evaluated. No significant antiviral activity was seen after incubation of MNV with whole hemolymph, hemocytes, or plasma from untreated oysters; however, these components all have strong antibacterial activity. Studies are under way to see if treatment with a beta-glucan immunostimulant commonly used in aquaculture will affect viral retention in oysters. Overall these studies suggest that hemocytes play an important role in the retention of human viruses in oyster tissues.