Epidemiology of Adenovirus Infections l Ubiquitous DNA viruses l Cause 5 -10% of febrile illnesses in early childhood l Nearly all adults have Abs to endemic serotypes 1, 2, 5, or 6

Clinical Manifestations l Vary according to the age and immune status of host l Different serotypes are associated with distinct syndromes

Adenovirus Transmission l Easily transmissable to individuals w/o serotype-specific Ab l Specific epidemic serotypes »Pharyngoconjunctival fever in summer camps, public swimming pools – Ad3, Ad7 »Hemorrhagic keratoconjunctivitis in medical facilities – Ad8, Ad37 »Acute respiratory disease in military recruits – Ad4, Ad7 l Minimal infectious dose?

Adenovirus Pneumonia l Adenoviruses cause about 10% of pneumonias in healthy children – Ad3, 7 »Disease more severe in infants l Extrapulmonary symptoms may occur w/o viral-specific histopathology »Meningoencephalitis, hepatitis, myocarditis, nephritis, neutropenia, DIC »Toxin?, Immune-mediated?

Adenovirus Infections in Immunocompromised Hosts l Range from asymptomatic shedding to fatal disseminated disease l Disease may result from »Primary infection »Reactivation of infection in patient »Reactivation of infection in donor organ

Adenoviruses in Bone Marrow Transplant Recipients l Wide range of clinical syndromes »Pneumonia »Gastroenteritis, hepatitis »Hemorrhagic cystitis, nephritis »Encephalitis, myocarditis l Incidence of infection higher in children vs. adults

Adenovirus disease in BMT recipients l Mortality of invasive disease % l Risks factors for invasive disease »Allogeneic transplants –especially T-cell depleted transplants »GVHD »2 or more culture-positive sites

1985 Seattle Study l Reviewed 1051 BMT recipients »Patient characteristics –Most had unmodified grafts from related matched donors –Proportion of children not stated l Incidence of adenovirus infection 5% l 1% incidence of disease (10) »mortality 50%

1994 Milwaukee Study l Reviewed 201 BMT recipients »Patient characteristics –85% T-cell depleted grafts –50% unrelated or partially-matched donors –40% children l Incidence of adenovirus infection 21% l 6.5% incidence of disease (13) »mortality of disease 54%

1994 Milwaukee Study l Higher incidence of adenovirus infections in children –31% vs. 14% in adults l Earlier time of onset in children – mean 90 days in adults l Ad35 and endemic types were most common isolates

1999 Kentucky Study l Reviewed 532 BMT recipients »Patient characteristics –72% allogeneic –40% T-cell depleted –24% children »Incidence of adenovirus infection 12% –Higher in children 23% vs. adults 9% »Incidence of disease 7.7% (41) –Overall mortality 73%

2000 Bristol Study l Reviewed 572 BMT recipients »Patient characteristics –45% had T-cell depleted grafts –45% unrelated donors –2/3 children »Incidence of adenovirus disease 17% (100) –Incidence of infection not documented –Definition of disease not vigorous –Mortality much lower than other studies - 6%

Solid Organ Transplantation l Adenovirus infection usually involves donor organ »Hepatitis in 3% pediatric liver transplants –Mortality 50% »Pneumonia in 1% lung transplants »Hemorrhagic cystitis in 1% renal transplants –Mortality <20%

Congenital Immunodeficiency Syndromes l SCID patients may develop severe infections »Mortality 50% »Pneumonia and hepatitis are most frequent syndromes l Patients with Ig deficiencies have less severe but more protracted illnesses

Adenoviruses in AIDS Patients l Adenoviruses frequently isolated in stool and/or urine w/o symptoms l Case reports of fatal infections including »Hepatitis, pneumonia, encephalitis, nephritis

Adenoviruses in Cancer Patients l More common in children than adults l Case reports of fatal infections including »Pneumonia, hepatitis, encephalitis, nephritis

Treatment l Discontinue immunosuppressive therapy l No antiviral documented to be of benefit »Cidofovir has best in vitro activity

Cidofovir l Broad spectrum nucleoside mono- phosphate analog »Inc. HSV, VZV, CMV, EBV, HHV-6, HPV l Has in vitro activity against adenovirus »However resistance may develop l Active in rabbit eye model

Therapy l Case reports »Hemorrhagic cystitis in BMT pts –response to IV ribavirin or vidarabine »Ad7 colitis in unrelated donor recipient d37 –No response to IV ribavirin. –Sx resolved on cidofovir w/i 2 wks. »Ad colitis and cholecystitis in AIDS pt –Prompt improvement with cidofovir

Immunotherapy l IV IgG may be helpful for lower serotypes »Most preps have good titers of neutralizing antibodies l Case report using donor lymphocytes in BMT recipient

Immune Responses Against Adenoviruses l Cell-mediated immunity »Severe infections occur primarily in hosts with cellular immune defects l Humoral immunity »Neutralizing antibodies protect against re- infection with same serotype »By age 10, most have Ab to endemic types

Adenovirus-specific T cell Responses l Most healthy adults have detectable proliferative and cytotoxic memory T cell responses l Adenovirus-specific T cells recognize epitopes conserved across different serotypes »In contrast to serotype-specific neut. Abs

Pathogenesis l Direct lysis of susceptible cells l Immunopathology? l Persistence

Adenovirus Persistence l Isolated from tonsils in asymptomatic children l Shed in stool for months post-infection l Cases of transmission from donor organs l Cases of reactivation in BMT patients

Transmission of adenovirus from solid organ transplants l Cases reports »Renal transplant pts with Ad34/35 hemorrhagic cystitis –documented seroconversion to Ad34/35 c/w with transmission from donor kidney (or primary infection) »Pediatric liver transplant pts with Ad5 hepatitis –6/9 seronegative pre-transplant; donors Ab pos –Median time of onset 25 days

Reactivation of adenovirus in BMT recipients l Cases reports »Ad5 hepatitis –Ad5-specific neutralizing Ab present in pre- transplant sera –c/w reactivation of endogenous virus »Ad35 cystitis, nephritis, colitis –6/6 adult pts had neutralizing Ab to own isolate pre-transplant (PF data)

Mechanism of Persistence l Remains episomal in long-lived lymphocytes? »Ad types 11,34,35 may establish persistence more readily –Infect hematopoietic cells more efficiently than other serotypes l Low level replication in tissue? l Integration?

Adenovirus Early Region 3 l E3 region codes for proteins that inhibit host responses »Down-regulate MHC class I antigens »Inhibit lysis by tumor necrosis factor »Inhibit apoptosis by Fas l Reduces immunogenicity? l Facilitates persistence?

Adenovirus Persistence l Reservoirs? »Lymphoid tissue – tonsils – Peyer’s patches in gut »Kidney »Liver »Lung, brain – PCR data

Are Lymphocytes a Reservoir? l Old data that PBMC from most donors positive for Ad2 by Southern blot l Not confirmed when assayed PBMC by PCR for Ad2 DNA »Used nested primers to E1A and hexon –72 of 73 asymptomatic children and adults were negative

Adenovirus Reservoirs l Lung »Detected E1A by PCR in 20/20 biopsies from lung cancer pts –Detected E1A by ISH in 2 pts –Detected E3 DNA by PCR in 10 pts –Authors suggest E1A may integrate into host DNA l Brain »Detected E1A in brain microglial cells by ISH and immunohistochemical staining in 7/7 senile pts l No negative controls

Live Adenovirus Vaccine l Live type 4 and type 7 vaccines used for years in military »Enteric-coated for oral administration »Safe and effective l Example of safety of RCA »via oral route »in healthy military population

RCA in Adenovirus Gene Therapy Vectors l Minimal infectious dose unknown »Likely dependent on multiple factors inc. –Route of administration –Presence or absence of serotype-specific Ab l Severity of disease dependent on: »Route of administration »Status of cellular immunity »Serotype

RCA in Adenovirus Gene Therapy Vectors l Elimination of RCA from E1-deleted vectors may be feasible »Altered 293 cell lines have been developed that prevent E1 recombination events l “Gutted” or helper-dependent vectors »Must purify away from E1-deleted helper adenovirus and RCA

Issue of Recombination l Recombination of E1-deleted vectors may occur in vivo with »persistent adenoviruses »newly acquired adenoviruses l Clinical significance?