Cytomegalovirus

Slide 1 · Cytomegalovirus

Latency, tissue injury, congenital infection and immunosuppression

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Explain CMV latency and the importance of cellular immunity.

Compare congenital, perinatal and postnatal transmission.

Recognize cytomegalic cells and their characteristic inclusions.

Link tissue tropism to organ injury and clinical syndromes.

Select source-supported diagnostic approaches by clinical context.

Slide 3 · CMV is a β-herpesvirus

CMV belongs to the β subgroup of human herpesviruses.

Herpesviruses produce primary infection followed by persistence and potential reactivation.

CMV disease is unusually dependent on host age and immune status.

Cellular and nuclear enlargement gives cytomegalovirus its name.

Virus class and host context both matter

Slide 4 · Latency is persistence without infectious virion production

Primary infection

Initial exposure

Viral genome persists

No ongoing infectious virus production in latency

Latent cellular reservoir

Monocytes and marrow progenitors

Potential reactivation

Immune surveillance weakens

Persistent infection is distinct from continuously productive infection.

Slide 5 · Immune status determines the clinical phenotype

Immunocompetent

Usually asymptomatic or mononucleosis-like

Congenital infection

May produce multi-organ injury and lasting deficits

Immunosuppressed

May produce severe disseminated disease

Slide 6 · CMV establishes latency in monocyte lineages

The source identifies monocytes and their bone marrow progenitors as latent reservoirs.

Latently infected leukocytes retain the virus long after initial illness.

Symptomatic recovery therefore does not mean virologic eradication.

Depression of cellular immunity enables reactivation.

Slide 7 · Reactivation follows impaired cellular surveillance

Latent CMV

Leukocyte reservoir

Depressed cellular immunity

Reduced immune restraint

Viral reactivation

Renewed viral replication

Productive tissue infection

Localized or disseminated organ disease

The source identifies reactivation as a major pathway to disease in immunosuppressed hosts.

Slide 8 · Primary infection, latency and reactivation differ

State

Viral behavior

Clinical implication

Primary infection

New acquisition of CMV

May be asymptomatic or cause illness

Latency

Genome persists without infectious virions

Ongoing lifelong reservoir

Reactivation

Replication resumes from latent infection

Major risk in impaired cellular immunity

Slide 9 · CMV persists after clinical recovery

Most immunocompetent patients recover without lasting symptoms.

CMV may continue to be excreted in body fluids for months or years.

Seropositivity persists throughout life after infection.

Persistence provides the biological basis for later reactivation.

Slide 10 · Transmission routes change with age and exposure

Before birth

Transplacental

Birth and infancy

Birth canal or breast milk

Preschool

Saliva and close contact

Adolescence onward

Genital route; Additional secretions

Any age

Blood transfusion or organ transplantation

Slide 11 · Transplacental infection defines congenital CMV

Maternal primary infection

Especially without preexisting protective antibodies

Transplacental spread

In utero transmission

Fetal infection

May be clinically silent

Congenital syndrome

May affect brain, liver and blood

Not every congenital infection is symptomatic at birth.

Slide 12 · Perinatal acquisition is a distinct exposure window

Exposure can occur to infected cervical or vaginal secretions during delivery.

Breast milk can transmit CMV after birth.

These routes differ from infection acquired across the placenta.

Clinical outcomes are commonly milder because of maternal antibody protection.

Slide 13 · Close-contact saliva transmission is important in preschool years

CMV transmission through saliva occurs in young children, including daycare settings.

Toddlers with CMV can readily transmit infection to parents.

Asymptomatic infection does not imply absence of viral shedding.

This setting connects early childhood infection with household transmission.

Slide 14 · Genital and other routes contribute after adolescence

The genital route is described as dominant after approximately age 15.

Respiratory secretions and fecal–oral exposure are additional routes.

The relative role of each route depends on age and exposure context.

Transmission need not be associated with clinically apparent disease.

Slide 15 · Transfusion and organ transplantation are iatrogenic routes

Transfusion and transplanted organs may transmit CMV at any age.

A solid-organ recipient may acquire CMV from an infected donor organ.

Iatrogenic exposure intersects with treatment-related immune suppression.

New infection and reactivation are both relevant in transplant settings.

Slide 16 · Congenital, perinatal and later exposure: Key distinctions

Context

Main route

Important clinical implication

Congenital

Transplacental

Potential fetal and developmental injury

Perinatal

Delivery secretions / breast milk

Often asymptomatic with maternal antibodies

Childhood / adult

Saliva, genital, other secretions

Commonly silent or mononucleosis-like

Iatrogenic

Organ transplant / blood product

Severe disease when host is immunosuppressed

Slide 17 · Cell-mediated immunity is central to CMV control

CMV-specific T-cell responses are important effectors against infected cells.

The source emphasizes CD8⁺ T lymphocytes as a major effector response.

CD4⁺ T cells, γδ T cells and natural killer cells may also contribute.

Loss of this coordinated response permits reactivation and organ disease.

Slide 18 · Dendritic-cell infection impairs antigen presentation

CMV infects dendritic cells

Immune-system target

Antigen processing is impaired

Reduced processing and presentation

T-cell stimulation is weakened

Compromised adaptive response

CMV interferes with the initiation of the host antiviral response.

Slide 19 · CMV down-modulates MHC class I and II expression

CMV-infected cell

MHC class I ↓

Impairs CD8⁺ T-cell antigen recognition

MHC class II ↓

Impairs CD4⁺ T-cell antigen recognition

CMV undermines antigen display to both major T-cell compartments.

Slide 20 · Viral homologues mimic host immunoregulatory proteins

CMV produces homologues of tumor necrosis factor receptor superfamily members.

It also expresses an interleukin-10 homologue.

MHC class I homologues add another layer of immune deception.

These are viral immune-evasion products, not evidence that infection has been cleared.

Slide 21 · Natural killer cell detection is also evaded

CMV-infected cell

Blocks activating receptors

Reduces NK-cell activation signals

MHC I–like inhibitory ligands

Engages NK inhibitory receptors

The virus counters NK-mediated detection while also reducing MHC expression.

Slide 22 · Viral Fcγ-binding proteins interfere with IgG defense

Viral Fcγ-binding glycoproteins

CMV-encoded immune-evasion proteins

Interference with host Fcγ receptor function

Compete with normal Fcγ-dependent pathways

Inhibition of IgG-mediated immunity

Antibody response becomes less effective

This mechanism targets antibody effector function rather than antigen presentation.

Slide 23 · CMV hides from and suppresses immune responses

Targeted defense

CMV strategy

Consequence

Antigen presentation

Dendritic-cell dysfunction; MHC I/II down-modulation

Less effective T-cell recognition

NK surveillance

Blocked activation and enhanced inhibitory engagement

Reduced NK-cell elimination

Antibody effector pathways

Viral Fcγ-binding glycoproteins

Impaired IgG-mediated defense

Immunoregulatory signaling

Viral cytokine/receptor homologues

Further immune modulation

Slide 24 · Cytomegaly is the defining cytopathic change

Infected cells may become strikingly enlarged, often around 40 μm in diameter.

Both the cytoplasm and nucleus expand and may appear pleomorphic.

The distinctive appearance is cytopathic rather than a neoplastic diagnosis.

Histologic interpretation requires recognizing the characteristic viral inclusions.

Slide 25 · “Owl’s-eye” nuclear inclusion: Defining features

Schematic — not a histologic specimen

A prominent basophilic inclusion lies within an enlarged nucleus.

The inclusion may occupy roughly half the nuclear diameter.

A clear halo separates the inclusion from the nuclear membrane.

The term “owl’s eye” refers to the nuclear appearance.

Slide 26 · Cytoplasmic inclusions accompany nuclear inclusions

Schematic — not a histologic specimen

Smaller basophilic inclusions can occur in the cytoplasm.

The cytoplasmic changes may be less sharply outlined than the nuclear inclusion.

Both compartments should be examined in suspicious enlarged cells.

The described Robbins lung figure depicts nuclear and cytoplasmic inclusions.

Slide 27 · CMV infects multiple tissue compartments

Glandular tissues

Parenchymal epithelial cells

Brain

Neurons

Lung

Macrophages, epithelial and endothelial cells

Kidney

Tubular epithelium and glomerular endothelium

Slide 28 · The pulmonary cellular targets explain varied histology

In the lung, CMV may involve alveolar macrophages.

Epithelial cells and endothelial cells are also susceptible.

Pulmonary disease can combine cytomegalic inclusions, interstitial inflammation and necrosis.

The morphologic picture reflects infection across several resident cell compartments.

Slide 29 · CMV can involve renal tubules and glomerular endothelium

Tubular epithelial cells

A parenchymal epithelial target

Glomerular endothelial cells

A vascular compartment target

Interpretive principle

Look for infected cells in more than one renal compartment

Slide 30 · Focal necrosis may occur with little inflammation

Focal necrosis in virtually any organ affected by CMV.

Inflammatory infiltrates may be minimal despite direct viral injury.

The degree of necrosis need not parallel a brisk inflammatory response.

This morphologic mismatch is relevant when reading immunosuppressed tissue biopsies.

Slide 31 · Recognize a cytomegalic cell systematically

1. Cellular scale

Identify an unusually enlarged cell

2. Nuclear change

Locate a large basophilic inclusion and clear halo

3. Cytoplasmic change

Look for additional smaller inclusions

4. Tissue context

Assess necrosis, inflammation and the involved organ

Schematic reasoning aid; Not a substitute for a clinical histology section.

Slide 32 · Congenital CMV has important population consequences

1 in 200

Babies born with congenital CMV

1 in 5

Affected babies with a long-term health consequence

Approximate estimates reported in the supplied Robbins text; Not newly re-estimated.

Slide 33 · Maternal primary infection may cause fetal CMV disease

Mother without prior protective antibodies

Susceptible maternal context

Primary CMV infection

Newly acquired infection

Transplacental spread

Congenital exposure

Affected fetus

Possible inclusion disease

The source particularly emphasizes primary maternal infection in classic severe congenital disease.

Slide 34 · Congenital infection spans silent to severe disease

Asymptomatic at birth

Still at risk of later sequelae in some cases

Milder symptomatic disease

Interstitial pneumonitis, hepatitis or hematologic disorder

Classic inclusion disease

Growth restriction, systemic injury and encephalitis

Slide 35 · Classic congenital disease can involve several systems

Growth

Intrauterine growth restriction

Liver and spleen

Jaundice, hepatosplenomegaly

Hematologic

Anemia, thrombocytopenic bleeding

Central nervous system

Encephalitis and neurologic injury

Slide 36 · Thrombocytopenia explains congenital bleeding

Congenital CMV syndrome

Systemic fetal infection

Thrombocytopenia

Reduced circulating platelet count

Bleeding manifestation

Recognizable clinical consequence

Anemia and jaundice may coexist with hematologic involvement.

Slide 37 · Congenital CNS involvement may be severe

Encephalitis is part of the classic symptomatic syndrome.

In fatal cases, the brain may be smaller than normal (microcephaly).

Foci of intracranial calcification can be present.

Structural brain injury relates to the risk of lasting neurologic impairment.

Slide 38 · Surviving infants may have permanent impairments

Hearing loss is a major long-term consequence.

Intellectual disability and other neurologic deficits may persist.

The severity of initial congenital disease is clinically important.

Long-term impairment can outlast the period of acute infection.

Slide 39 · Initially asymptomatic congenital CMV can declare later

In utero infection

Congenital acquisition

No symptoms at birth

Silent neonatal presentation

Months to years pass

Delayed emergence

Hearing or neurologic sequelae

May include deafness or cognitive impairment

Absence of early clinical findings does not rule out late effects.

Slide 40 · Milder congenital forms are not invariably harmless

Congenital infection may present as interstitial pneumonitis.

Hepatitis or hematologic manifestations are alternative presentations.

Most infants with these milder forms recover.

A minority may develop subsequent intellectual impairment.

Slide 41 · Neonatal CMV is diagnosed using viral DNA detection

Suspect congenital or neonatal CMV

Symptoms or relevant clinical context

Collect urine or saliva

Source-supported neonatal specimen types

PCR for CMV DNA

Demonstrate viral DNA

The excerpt does not specify diagnostic collection deadlines or test cutoffs.

Slide 42 · Clinical exercise: Newborn with multi-system findings

Clinical vignette

An infant has intrauterine growth restriction, jaundice, hepatosplenomegaly and thrombocytopenia. Neuroimaging describes a small head size with intracranial calcifications.

Which congenital viral infection best integrates these findings?

Which specimen types are identified for neonatal PCR testing?

Which long-term organ-system consequence is most important to anticipate?

Slide 43 · Case reasoning: Congenital CMV inclusion disease

Syndrome recognition

The constellation supports classic symptomatic congenital CMV.

Test selection

Urine or saliva CMV DNA PCR.

Future consequences

Sensorineural hearing and neurologic deficits are major concerns.

Slide 44 · Perinatal CMV is acquired during or after delivery

Infected maternal secretions

Cervical/vaginal secretions or milk

Exposure during birth or through breast milk

Not transplacental acquisition

Perinatal CMV infection

Most infections are clinically silent

Perinatal and congenital infection are epidemiologically distinct.

Slide 45 · Maternal antibodies often protect perinatally infected infants

Maternal anti-CMV antibodies cross the placenta before delivery.

These antibodies contribute to the usually asymptomatic perinatal course.

Protection does not necessarily prevent acquisition or viral excretion.

The source contrasts this pattern with severe infection from maternal primary CMV.

Slide 46 · Perinatal infants may shed virus for a prolonged period

Even symptom-free infants can continue to excrete CMV.

Urine and saliva shedding may persist for months to years.

Clinical well-being is not equivalent to immediate cessation of excretion.

Longitudinal shedding helps explain transmission during early childhood.

Slide 47 · Symptomatic perinatal CMV is less common

Most infections acquired around birth are asymptomatic.

Uncommonly, affected infants develop interstitial pneumonitis.

Failure to thrive, rash and hepatitis are other reported manifestations.

Some studies have reported subtle later hearing or cognitive effects.

Slide 48 · Congenital versus perinatal CMV

Feature

Congenital

Perinatal

Acquisition

Across placenta before birth

Delivery secretions or breast milk

Maternal context

Primary maternal infection emphasized in severe disease

Maternal antibodies often protective

Presentation

Silent to severe multisystem syndrome

Usually silent; rare pneumonitis / hepatitis

Long-term issues

Hearing and neurologic impairment

Subtle effects reported in some studies

Slide 49 · CMV infection is often silent in healthy hosts

Most primary CMV infections in healthy children and adults cause no overt illness.

The supplied source estimates global seroprevalence at about 80%.

A highly prevalent persistent infection can therefore be clinically unrecognized.

When symptomatic, a mononucleosis-like syndrome is the typical presentation.

Slide 50 · Immunocompetent CMV may resemble mononucleosis

Systemic

Fever and lymphadenopathy

Peripheral blood

Atypical lymphocytosis

Liver

Hepatomegaly and abnormal liver tests

Typical outcome

Recovery without sequelae

Slide 51 · CMV-associated hepatitis contributes to the mono syndrome

Liver involvement may accompany the systemic febrile illness.

Hepatomegaly and abnormal liver function tests are described.

Hepatitis appears with atypical lymphocytosis and lymphadenopathy.

The syndrome does not imply the severe disseminated disease seen in immunosuppressed patients.

Slide 52 · Serology and lifelong positivity shape interpretation

Serology as the diagnostic approach for CMV mononucleosis.

Infected people remain seropositive for life.

Seropositivity alone cannot establish that current tissue symptoms are due to active CMV.

Persistent latent virus and prolonged shedding require clinical context.

Slide 53 · Clinical severity changes with immune competence

Immunocompetent

Immunosuppressed

Usually asymptomatic

New infection or reactivation may be severe

Possible mononucleosis-like illness

Pneumonitis and colitis prominent

Generally recovers

Disseminated, life-threatening infection possible

Serology for mono presentation

Tissue assessment and DNA detection used

Slide 54 · Transplant recipients are vulnerable to serious CMV

Recipients of solid organs are at risk because cellular immunity is compromised.

Donor organs may introduce CMV into an uninfected recipient.

Reactivation of previously latent CMV is another pathway.

CMV-specific cellular immunity is relevant in the stem-cell transplant setting.

Slide 55 · Antiretroviral therapy changed CMV in HIV disease

CMV was previously a leading opportunistic viral pathogen in AIDS.

Serious CMV infection has decreased markedly with antiretroviral therapy.

The source nevertheless describes CMV as a continuing contributor to HIV disease.

Interpret the historical observation in the specific context of modern immune restoration.

Slide 56 · Two pathways lead to infection in suppressed hosts

New CMV infection

For example, an infected donor organ

Latent CMV reactivation

Immune control of existing reservoir declines

Shared consequence

Productive infection with possible organ dissemination

Both routes must be considered in transplant and other suppressed populations.

Slide 57 · Severe disseminated CMV favors lung and gut

Lungs

Pneumonitis; Potential respiratory failure

Gastrointestinal tract

Colitis, ulcers and necrosis

Other associations

Vasculopathy or neurocognitive impairment reported

Slide 58 · CMV pneumonitis shows interstitial injury

Pulmonary tissue may show an interstitial mononuclear infiltrate.

Foci of necrosis accompany the inflammatory changes.

Cytomegalic enlarged cells with inclusions provide characteristic morphologic evidence.

The distribution reflects infection in epithelial, endothelial and macrophage populations.

Slide 59 · Pulmonary disease can progress to acute respiratory distress

CMV pulmonary infection

In susceptible host

Interstitial inflammatory and necrotic injury

Inclusions may be found in infected cells

Severe pneumonitis

Impaired gas exchange may ensue

Acute respiratory distress syndrome

Potential life-threatening outcome

The sequence is a clinical pathophysiologic schematic, not a guaranteed progression.

Slide 60 · CMV colitis may be ulcerative and necrotizing

Gastrointestinal infection

Often in immunosuppressed people

Mucosal necrosis and ulceration

Direct tissue destruction

Extensive intestinal injury

Lesions can be widespread

Diarrhea / pseudomembranes

Severe clinical consequence

Tissue biopsy morphology matters because GI symptoms alone are nonspecific.

Slide 61 · Pseudomembranes can develop after extensive intestinal injury

CMV-induced intestinal necrosis can be extensive.

Ulceration may be accompanied by pseudomembrane formation.

Debilitating diarrhea is a major clinical consequence.

The lesion must be interpreted in the setting of the patient’s immune state.

Slide 62 · Other reported CMV associations require caution

Associations with vasculopathy and neurocognitive impairment.

Association is not, by itself, proof that CMV caused every vascular or cognitive abnormality.

A defined organ syndrome, virologic evidence and tissue context strengthen attribution.

Avoid over-interpreting viral positivity without relevant clinicopathologic findings.

Slide 63 · Histology supports diagnosis when inclusions are found

Affected organ tissue

Biopsy or tissue section

Recognizable cytopathic changes

Large nucleus; Owl’s-eye inclusion; Other inclusions

Clinicopathologic synthesis

Correlate morphology with symptoms and immune status

Morphology demonstrates tissue involvement; This diagram is not an algorithm with validated accuracy.

Slide 64 · CMV diagnostic approaches depend on clinical setting

Clinical situation

Source-supported diagnostic method

Interpretive emphasis

Neonatal infection

Urine / saliva CMV DNA PCR

Evidence of neonatal infection

Mono-like illness

Serology

Compatible systemic syndrome

Organ disease

Characteristic tissue morphology; viral culture

Direct organ assessment

Post-transplant follow-up

Quantitative CMV DNA PCR

Serial viral DNA monitoring

Slide 65 · Quantitative PCR transformed transplant surveillance

Post-transplant host at risk

Immune suppression and donor exposure

Serial CMV DNA measurement

Quantitative PCR-based monitoring

Track virologic trend

Measure change over time

Inform clinical assessment

Integrate with organ symptoms and tests

No viral-load threshold or treatment-trigger value is specified in the source.

Slide 66 · Clinical exercise: Transplant recipient with organ dysfunction

Clinical vignette

A solid-organ transplant recipient receiving immunosuppressive therapy develops respiratory symptoms. Tissue assessment identifies strikingly enlarged cells with characteristic nuclear inclusions.

Which infection unifies host risk and cytopathic appearance?

What two routes of viral acquisition are relevant?

Which additional test modality does Robbins emphasize for transplant monitoring?

Slide 67 · Case reasoning: CMV pneumonitis after transplantation

Most coherent diagnosis

CMV tissue disease; Lung is a major target in immunosuppressed patients.

Potential origin

New transmission from donor tissue or reactivation of latent CMV.

Monitoring

Quantitative CMV DNA PCR is an important post-transplant assay.

Slide 68 · Synthesis: Host context, morphology and testing

Host context

Typical concern

Source-supported evidence

Congenital

Fetal injury; delayed deficits

Urine/saliva CMV DNA PCR

Perinatal

Usually silent acquisition and shedding

Exposure history / clinical context

Immunocompetent

Mono-like syndrome

Serology

Immunosuppressed

Pneumonitis, colitis, dissemination

Inclusions in tissue; viral DNA testing

Slide 69 · Questions for clinicopathologic review

Why can a patient harbor CMV after apparently complete recovery?

How do congenital and perinatal routes change expected outcomes?

Which nuclear and cytoplasmic alterations should prompt CMV consideration?

Why are pneumonitis and colitis especially important after immune suppression?

Why must PCR results be interpreted alongside organ pathology?

Slide 70 · Reference and source limits

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th edition (2026).

The lecture is based on the supplied Cytomegalovirus section and its herpesvirus parent context.

Original textbook micrographs were not available for reuse; teaching illustrations are editable schematics, not clinical specimens.

All patient scenarios are hypothetical and constructed from findings in the source.