Immunity and Resistance to Astrovirus Infection

Abstract

Astroviruses are one of the leading causes of acute viral enteritis in infants, and are recognized as a clinically important pathogen in the elderly and the immunocompromised. In spite of this, we still know very little about the immune response to astrovirus infection. Clinical observations and human volunteer studies have indicated a role for the humoral response and suggest neutralizing antibodies are important in limiting infection. Studies of human intestinal biopsies have suggested that cellular immunity; specifically CD4(+) T-cells may also be involved in the anti-astrovirus response. Additionally, various animal models have indicated potential roles for the innate immune system in controlling infections. How these various effector arms of the immune system collaborate to result in immunity and resistance to astrovirus infection is still unknown. This review summarizes our current understanding of the immune response to this pathogen and highlights the key concepts that still need to be addressed. Until we understand the role of the immune system in astrovirus infection or other enteric viruses, we will continue to be limited in our ability to treat and control gastrointestinal diseases.

Celiac Disease—Sandwiched between Innate and Adaptive Immunity

“…Other enteroviruses including astroviruses, noroviruses, and adenoviruses are also frequent causes of diarrhea episodes in children [38]. Th1 responses and inflammation play important roles in anti-enteroviral immunity [39,40] and are associated with local production of IFN-␣ [41,42]. It is therefore conceivable that IFN-␣ production as a result of a viral infection would lead to a shift toward Th1 responses and reinstruct previously tolerogenic DCs to prime gluten-specific T cells and support inflammation instead of sustaining oral tolerance.…”

The Role of Prolonged Viral Gastrointestinal Infections in the Development of Immunodeficiency-Related Enteropathy

“…Astrovirus causes acute viral enteritis [66,90]; in healthy children, shedding usually lasted several days, but could persist for up to 35 days, often asymptomatically [91]. Results from a birth cohort of rural Mayan infants were very different from Western study cohorts; 61% was astrovirus positive during the 18-week study period.…”

“…Several studies have investigated the duration of enterovirus excretion, most notably poliovirus. Vaccination program strategies have eradicated polio in several continents [66]; although due to the use of live oral poliovirus vaccine, and the fact that sporadic immunocompromised patients fail to clear the infection and thus become chronic excretors, vaccine-derived poliovirus (VDPV) still circulates in the population [67][68][69]. VDPV may be excreted up to 4-8 weeks by a large proportion of susceptible healthy individuals [65,70]; one healthy infant excreted VDPV for 10 months [71].…”

“…Astrovirus infections are frequent in immunocompromised patients [66,90,93]. During an outbreak in a pediatric PID unit, two patients excreted astrovirus for 156 days [90,94].…”

Acute Gastroenteritis Viruses

“…Prevalence of antibody to other serotypes is lower (Kriston et al, 1996;Midthun et al, 1993), even in adults. Antibodies may play a role in protecting from infection based upon the human experimental infection studies, but T cell immunity may be important in helping to clear infection (Koci, 2005). A patient with a congenital T cell immunodeficiency (cartilage hair hypoplasia) had prolonged astrovirus excretion for at least 225 days associated with diarrhea and coinfection with rotavirus (Wood et al, 1988).…”