Unit 4 Part 5 Viral Infections

Terry Kotrla, MS, MT(ASCP)BB

Herpes Virus Group

 Include 8 viruses that cause disease.

 May result in sub-clinical infections  Capable of establishing latent infection.

 May be reactivated under appropriate conditions.

Herpes Virus Group

 We will discuss the following: – Epstein-Barr virus – Cytomegalovirus – Herpes simplex virus type I and II – Varicella-zoster virus

Epstein-Barr Virus (EBV)

   Spread through oral transmission Cause of

Infectious Mononucleosis.

Other Diseases include:

– African or Burkitt’s lymphoma – Nasopharyngeal carcinoma – B cell lymphoma

Infectious Mononucleosis

 Acute self-limiting infection of the RE system  Four to 7 week incubation  Enlarged lymph nodes in the neck.

 Sore throat, fever, rash  Malaise and extreme tiredness  Liver and spleen involvement and enlargement.

Infectious Mononucleosis - Lab

   Hematology: – High WBC, – Over 20% atypical reactive lymphocytes also known as Downey cells.

Positive mono (heterophile antibody) test.

Negative mono test do tests for antibodies to EBV associated antigens.

Infectious Mononucleosis

 Downey cells may be present

Heterophile Antigens/Antibodies

 

Heterophile antigens

mouse.

are a group of similar antigens found in unrelated animals, i.e., man, sheep, horse, dog cat,

Heterophile antibodies

produced against heterophile antigens of one species will cross react with others.

Heterophile Antigens/Antibodies

 

Forssman antigen

is an example of a heterophile antigen and is found on the RBCs of many species (guinea pig, dog, cat, mouse, sheep, fowl, horse)

Forssman antibodies

Forssman antigens will agglutinate sheep RBCs.

formed against

Paul Bunnell Test

 Simple titration of sheep cell agglutinins.

 Serial dilutions of patient serum.

 Add sheep RBCs.

 Positive indicates presence of heterophile antibodies.

 Not specific for IM, screening test only.

Davidsohn Differential

 Used to determine heterophile antibody present.

 Add patient serum to one tube with guinea pig kidney and another with beef red blood cells.

– Beef RBCs have IM antigen.

– Guinea pg kidney have Forssman antigen.

 Harvest serum and test with sheep cells.

Davidsohn Differential

* To be considered absorbed there must be greater than a three tube difference between the presumptive titer and the differential titer.

Heterophil Antibody ------------------------ Infectious Mono Forssman Serum Sickness Kidney Extract ------------------ Not Absorbed -Aggt Absorbed– No Aggt Absorbed– No Aggt Beef Erythrocyte --------------------- Absorbed – No Aggt Not Absorbed-Aggt Absorbed– No Aggt

Davidsohn Differential

Advantages Disadvantages   When properly performed, this test is specific for Infectious Mononucleosis False-positive results are rare.

 Davidsohn Differential test is very time consuming and burdensome.

Infectious Mono Slide Tests

    It was discovered that horse RBCs possess antigens which react with the antibody associated with IM.

Patient serum mixed with horse RBCs, agglutination is positive.

Latex agglutination, coat particles with EBV antigens.

Not diagnostic, must look at total clinical picture.

EBV Antigens

 Early antigen (EA)  Capsid antigen (VCA)  Membrane antigen (MA)  Nuclear antigen (EBNA)

EBV Specific Antibodies

     EBV specific antibodies may be measured.

Pattern of appearance of EBV antigens.

Most valuable is IgM antibody to viral capsid antigen (VCA), indicates a current infection (best marker), lasts about 12 weeks.

Can also detect anti-early antigen (EA) (recent infection) and anti EB nuclear antigen (EBNA) (older infection).

ELISA and IFA most commonly used

EBV Antibody Response

Stage of Disease Anti-VCA Acute Heterophile Antibody Pos or Neg IgM IgG Anti-EBNA Pos Pos Neg Past infection Neg Neg Pos Pos

African or Burkitt’s Lymphoma

• EBV has been strongly implicated • Malignant B-cell neoplasm – presents as rapidly growing tumor of the jaw, face or eye – grows very quickly, and without treatment most children die within a few months  Rare in US, equatorial Africa.

 Also associated with HIV infection.

African or Burkitt’s Lymphoma

  Although BL is a very rapidly growing tumour it responds well to treatment. Three pictures: before treatment, 3 days and 6 days after treatment

Nasopharyngeal Carcinoma

      Endemic in South China, Africa, Arctic Eskimos This is a malignant tumour of the squamous epithelium of the nasopharynx.

100% contain EBV DNA Rates are less than 1 per 100,000 in most populations Nasopharyngeal carcinomas are found in association with reactivation of latent Epstein Barr Virus.

The exact mechanisms of association are unknown

B-Cell Lymphoma

   In most individuals infected with EBV, the virus is present in the B-cells, which are normally controlled by T-lymphocytes When T-cell deficiency exists, one clone of EBV infected B-lymphocytes escapes immune surveillance to become autonomously proliferating. EBV induced B cell lymphomas are most prevalent in immunocompromised patients.

Oral Hairy Cell Leukoplakia

   HIV infection stimulates reactivation of pre-existing, latent EBV infection.

Causes viral infection of the oral cavity. Indicator of HIV infection as well as of a person's lessening or weakening immunity

Cytomegalovirus

   Human Herpesvirus 5 (HHV-5) Transmission occurs from person to person.

Close intimate contact – Sexual contact – Perinatally – Breast milk – Organ transplant – Blood transfusion

CMV Clinical course

 Symptoms resemble IM  In babies may cause life threatening illness  Patients with deficient immune systems  AIDS patients  Transplant patients

Cytomegalovirus

    Perinatal transmission occurs in 10%.

If infected may cause multitude of symptoms – Petechiae – Jaundice – Hepatosplenomegaly – Neurological abnormalities Moratlity rate 5 percent Survivors may exhibit hearing loss, visual impairment and mental retardation.

CMV Immunologic response

 Test for CMV antibody using paired serum samples  IgM antibodies produced against early and intermediate-early (IE) CMV antigens, last for 3 to 4 months.

 IgG appear shortly after and peak at 2 to 3 months.

CMV Laboratory Diagnosis

 Range from culture and cytologic techniques to DNA probes, PCR and serologic techniques.

 Detection of antibodies indicator of recent or active infection.

 Viral cultures

Microscopic examination of biopsy specimens

CMV Lab Diagnosis

    Detection of CMV antigen in cells using IFA ELISA to detect antibody to CMV Other – fluorescence assays, – indirect hemagglutination, and – latex agglutination False positives can occur due to RA and Epstein-Barr antibodies

Herpes Simplex Virus (HSV)

 Most exposed in childhood  Possesses viral latency – hibernation  Two types: HSV-1 and HSV-2

HSV-1

 Transmitted from person to person by saliva or direct contact.

 Cold sores around the mouth most common.

 Reactivation - may have several episodes of cold sores during a lifetime

HSV-1

 Symptoms – tingling – Numbness – Itching  Blister forms, breaks, crusts over  Reactivation usually caused by stress.

 Conjunctivitis, keratitis and herpetic whitlow may occur.

HSV-2

   Results in Herpes genitalis - lesions BELOW the waist.

Transmitted intimate sexual contact or perinatally.

Symptoms – Pain – Tenderness – Itch – Fever – Headache – Lymphadenopathy – Malaise

HSV-2

 Blisters appear – Males – penis – Females – vagina and cervix – Both – thighs buttocks  Painful, lasts 1-3 weeks  Virus lies dormant in nearby nerves and reactivated.

HSV – 2

 Can be fatal in infants  Woman with active infection needs C section.

 Infants with localized infections have 70% mortality rate  Disseminated neonatal herpes most lethal form.

Neonatal Herpes

Laboratory Testing for HSV

        Recovery of virus from culture Direct examination of cells from lesion using IF or immunoperoxidase stain DNA probes ELISA Latex agglutination RIA Indirect IF Serology NOT very useful

Varicella-Zoster Virus

 Two different manifestations of the same virus.

– Varicella is the primary infection,

causes chicken pox

– Herpes Zoster causes shingles and is due to reactivation of the latent virus

Varicella

 Fever and vesicular exanthema  Small, itchy blisters surrounded by inflamed skin.

 Begins as one or two lesions and spreads.

 Number of lesions vary greatly.

 Blister dries out and forms a scab.

Chicken Pox

Chicken Pox

 Secondary complications due to infection most common.

– May also result in pneumonia, encephalitis and hepatitis.

– Very serious for immunocompromised children  Vaccine now available

Shingles

 Chicken pox – virus goes latent  Reactivated later in life – Weakened immune system – Aging – Other factors

Shingles

 The typical rash of shingles begins as redness(erythema) followed by the appearance of blisters.

 Eruptions follow the path of an infected nerve.

 The trunk is the area affected in 50% to 60% of cases.

 Skin may be extremely sensitive to touch

Shingles

Shingles

Shingles

VZV Laboratory Testing

 Important to distinguish VZV from other infections – PCR – Direct Fluorescent Antibody staining – Viral culture – IgG and IgM antibody test by ELISA

Rubella Virus

 RNA virus with 3 major structural proteins, E1, E2, and C.

 Incubation 2- 3 weeks  Highly contagious, spread through respiratory tract.

  Causes German measles Rubella vaccine has resulted in 99% decline in infections.

Rubella Symptoms

 Mild and difficult to notice – Mild fever – Headache – Stuffy or runny nose – Red eyes – Enlarged and tender lymph nodes – Pink rash begins on face, spreads to trunk then arms and legs, disappears in same order.

– Aching joints

Rubella

Congenital Rubella

       Congenital Rubella Syndrome most serious.

Fetus infected during first trimester.

Result in miscarriage or stillbirth, Live-born serious birth defects or dying.

20% of the children born after such an infection suffer the severe congenital abnormalities 10-20% of these children die within the first year of life.

Rubella vaccine contraindicated during pregnancy.

Rubella Syndrome

Rubella Lab testing

    IgG and IgM antibodies may form at same time IgM antibodies persist for 4 to 5 weeks, IgG for life.

Performed primarily for diagnosis of acquired infections and to determine immune status of pregnant patients.

Some tests detect IgG antibodies, other IgM.

Rubella Laboratory Testing

 Methods include: – hemagglutination inhibition – passive hemagglutination – neutralization – hemolysis in gel – complement fixation – fluorescence immunoassay – RIA – ELISA – latex agglutination.

Rubeola

 Single stranded RNA virus best known for its typical skin rash  Primarily respiratory infection  Incubation approximately 10 days, ranges from 8-13.

 Rash appears at about day 14.

 Airborne precautions

Rubeola

 Symptoms include – Irritability – Runny nose – Eyes that are red and sensitive to light, – Hacking cough, and – High fever – Swollen lymph nodes

Rubeola

     Fever peaks with the appearance of the rash.

Red spots with tiny grayish white heads appear on inside of cheeks at back of mouth.

After 18 hours spots disappear and rash develops, typically begins on forehead, then spreads downward over face, neck, and body.

Rash appears on face first and consists of large flat red to brown blotches that often flow into one another.

Rash fades in the same order that it appeared

Rubeola

Rubeola Complications

        Croup Bronchitis Bronchiolitis Pneumonia Conjunctivitis Myocarditis Hepatitis Encephalitis

Rubeola

 More susceptible to ear infections or pneumonias.

 Disease can be severe, with bronchopneumonia or brain inflammation  May lead to death in approximately 2 of every 1,000 cases.

 Most severe in adults.

Measles vaccine

  Live attenuated-reduce virulence of organism but it is till alive.

DO NOT give to: – pregnant women, – persons with active tuberculosis, – leukemia, – lymphoma, – depressed immune systems. – People with egg allergies

Measles vaccine

 Occasionally causes side effects in persons with no underlying health problems,  In about 10% of cases there is a fever between 5 and 12 days after vaccination,  In about 5% of cases there is a rash.

Rubeola Laboratory Testing

  Serology testing provides best means of confirming a measles diagnosis Methods to detect rubeola antibodies include: – hemagglutination inhibition – endpoint neutralization – complement fixation – IFA – ELISA

Laboratory Testing

   Diagnosis confirmed by presence of Rubeola specific IgM antibodies antibodies or four-fold rise in IgG antibody titer in paired samples taken after rash to 10 to 30 days later.

IgM test highly depended on time of sample collection with 3-11 days after rash being optimal.

IgM false positive due to RA.

Mumps

 Single stranded RNA virus.

 Mumps is transmitted by direct contact with saliva and discharges from the nose and throat  iIncubation 16-18 days.

 Virus can infect many parts of the body, especially the parotid salivary glands.

Mumps

 Glands usually become increasingly swollen and painful over a period of 1 to 3 days  Pain gets worse  Both the left and right parotid glands may be affected

Mumps

Mumps

Mumps - Complications

 Inflammation and swelling of the brain  Mumps in adolescent and adult males may also result in the development of orchitis  May affect the pancreas or, in females, the ovaries  Infection in pregnant women may result in increased risk for fetal death

Laboratory Testing

 complement fixation  hemagglutination inhibition  hemolysis-in-gel  neutralization assys  IFA and  ELISA

Laboratory Testing

    Current or recent infections indicated by presence of specific IgM antibody in single sample which can be detected within 5 days of illness.

Fourfold rise in specific IgG antibody in 2 samples collected during acute and convalescent phases Fluorescent antibody staining for mumps antigens Cross-reactivity between antibodies to mumps and parainfluenza viruses has been reported in tests for IgG, not a problem since symptoms differ.

The End