# Presentation: 806976

## Epidemiology of Adenovirus Infections

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

## Clinical Manifestations

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

## Adenovirus Transmission

- Easily transmissable to individuals w/o serotype-specific Ab
- 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
- Minimal infectious dose?

## Adenovirus Pneumonia

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

## Adenovirus Infections in Immunocompromised Hosts

- Range from asymptomatic shedding to fatal disseminated disease
- Disease may result from
- Primary infection
- Reactivation of infection in patient
- Reactivation of infection in donor organ

## Adenoviruses in Bone Marrow Transplant Recipients

- Wide range of clinical syndromes
- Pneumonia
- Gastroenteritis, hepatitis
- Hemorrhagic cystitis, nephritis
- Encephalitis, myocarditis
- Incidence of infection higher in children vs. adults

## Adenovirus disease in BMT recipients

- Mortality of invasive disease 50 -60%
- Risks factors for invasive disease
- Allogeneic transplants
- especially T-cell depleted transplants
- GVHD
- 2 or more culture-positive sites

## 1985 Seattle Study

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

## 1994 Milwaukee Study

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

## 1994 Milwaukee Study

- Higher incidence of adenovirus infections in children
- 31% vs. 14% in adults
- Earlier time of onset in children
-  mean <30 days vs. >90 days in adults
- Ad35 and endemic types were most common isolates

## 1999 Kentucky Study

- 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

- 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

- 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

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

## Adenoviruses in AIDS Patients

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

## Adenoviruses in Cancer Patients

- More common in children than adults
- Case reports of fatal infections including
- Pneumonia, hepatitis, encephalitis, nephritis

## Treatment

- Discontinue immunosuppressive therapy
- No antiviral documented to be of benefit
- Cidofovir has best *in vitro* activity

## Cidofovir

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

## Therapy 

- 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

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

## Immune Responses Against Adenoviruses

- Cell-mediated immunity
- Severe infections occur primarily in hosts with cellular immune defects
- 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

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

## Pathogenesis

- Direct lysis of susceptible cells
- Immunopathology?
- Persistence

## Adenovirus Persistence

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

## Transmission of adenovirus from solid organ transplants

- 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

- 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 

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

## Adenovirus Early Region 3 

- 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
- Reduces immunogenicity?
- Facilitates persistence?

## Adenovirus Persistence

- Reservoirs?
- Lymphoid tissue
-  tonsils
-  Peyer’s patches in gut
- Kidney
- Liver
- Lung, brain – PCR data

## Are Lymphocytes a Reservoir?

- Old data that PBMC from most donors positive for Ad2 by Southern blot
- 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

- 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
- Brain
- Detected E1A in brain microglial cells by ISH and immunohistochemical staining in 7/7 senile pts
- No negative controls

## Live Adenovirus Vaccine

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

## RCA in Adenovirus Gene Therapy Vectors

- Minimal infectious dose unknown
- Likely dependent on multiple factors inc.
- Route of administration
- Presence or absence of serotype-specific Ab
- Severity of disease dependent on:
- Route of administration
- Status of cellular immunity
- Serotype

## RCA in Adenovirus Gene Therapy Vectors

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

## Issue of Recombination

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