Virology Pt. 2

Retroviridae

• Enveloped dsRNA viruses that range in size from 80 to 120 nm.
• Contain reverse transcriptase, which translates RNA into DNA.
• Integrate into the genome of the host cell.
• Consist of Oncovirinae, Lentivirinae, and Spumavirinae.

Oncovirinae

• Includes HTLV-1, -2, and -5 (Human T-cell lymphotropic virus) and has an oncogenic effect.
• Induction of leukemia and lymphomas from T-cells can occur.

Lentivirinae

• Includes HIV-1 and HIV-2.

Spumavirinae

• HFV (Human foamy virus).
• Pathogenesis is unclear.
• Was isolated from patients with neoplastic and degenerative diseases like myasthenia gravis, multiple sclerosis, and granulomatous thyroiditis

Human Immunodeficiency Virus (HIV)

• First identified case: 1960, a Scandinavian man in the 1960s who had visited west-central Africa (Kongo).
• Spread in the late 1970s and early 1980s.
• Historical name: "gay-related immunodeficiency disease" = GRID due to a number of homosexual men dying of normally benign infections.
• Two types of HIV: HIV-1 and HIV-2.

HIV-1

• Worldwide distribution.
• Original source: Chimpanzee
• 4 genotypes.
• M (11 serotypes – A-K), N, O, P
• 2 phenotypes: M-type (infecting macrophages and dendritic cells), T-type (infecting T-Cells)

HIV-2

• Mostly West Africa.
• Has a slower disease development.
• Original source: Mangabey

HIV Isolation

• HIV-1 was isolated by French virologist Luc Montagnier, along with Francoise Barré-Sinoussi and Jean-Claude Chermann, in 1983.
• The isolation was awarded the Nobel Prize in 2008.
• HIV-2 is prevalent in Africa and is evolutionarily older.
• AIDS - Acquired Immunodeficiency Syndrome is a result.

HIV Structure

• Envelope: double-layered coat with glycoproteins, gp41 (fusion virion with host cell membrane), and gp120 (attachment to CD4+ receptor and entry to host cell).
• Capsid: p24 protein.
• Core: 10 – 50 copies of reverse transcriptase, integrase enzyme (integrating viral DNA to host cell DNA), and protease (protein formation).
• Genome: dsRNA (3 structural genes + 6 regulation genes).

HIV Replication

• Targets CD4+ cells and macrophages.
• Attachment: gp120 to CD4+ receptor.
• Membrane fusion: host cell + virion using gp41.
• Release HIV RNA to host cell cytoplasm.
• Reverse transcription dsDNA
• Enters the host cell nucleus.
• Integration to host genome by integrase.
• RNA transcription cytoplasm.
• Protease cuts and assembles new HIV virus.
• Release of new virions by budding.

HIV Pathogenesis

• Primary target is Langerhans cells cervix, tonsils
• Reaction with CD4+ cells virus spreads to lymph nodes body.
• Increscent of CD8+ cells antiviral activity.
• A few years can result in exhaustion of the immune system.
• Development of opportunistic infections.

HIV Spread

• Through sexual contact, sperm, and vaginal secretion.
• Higher risk from positive man to women - semen contains high concentration of virus and has contact with bigger surface of mucous membrane.
• The transfer probability in vaginal sex from a positive man to a woman 1:100 – 1:1000.
• The transfer probability annal sex is 1:10.
• From mother to child during pregnancy, delivery, and during breast feeding.
• Probability is 15-30% without antiretroviral therapy (can be decreased to 1%).

Fluids

• Body fluids (especially blood) and tissues require mandatory screening.

No HIV Spread

• Kissing / saliva if no injury is present
• Shared bathroom / toilet
• Insect Bites.

HIV Pathogeny

• Incubation period is 2-6 weeks to months, depends on dose and immune status.
• Without treatment, death occurs in 10 years.

HIV Primoinfection

• Acute phase lasts 2-4 weeks after infection.
• Symptoms include influenza-like, mononucleosis-like symptoms, aseptic meningitis, and rash.

Asymptomatic Stage

• Virus replication in lymph nodes that can last for years.
• CD4+ T-cells >500/ul.

Symptomatic Stage

• Early stage: CD4+ <300/ul more milder opportunistic infections like herpes zoster, leukoplakia, soor.
• Late: CD4+ less than <200/ul means more serious opportunistic infections.

Developed Disease (AIDS)

• CD4+ can be <50/ul
• Virus >75 000 copies/ml
• The final stage of HIV infection
• Includes significant weight loss, severe opportunistic infections, malignancies, and dementia.

Opportunistic Infections during Developed AIDS

• Pneumocystis jirovecii pneumonia.
• Toxoplasma gondii encephalitis.
• Candidiasis.
• Chronic herpes simplex virus (HSV-1, HSV-2) infection.
• CMV infection.
• Cryptococcus neoformans infection.
• Mycobacterium tuberculosis.
• Mycobacterium avium, M. intracellulare.

Disorders

• HIV encephalopathy → dementia, memory and concentration disorders, personality changes, and depression.
• HIV nephropathy or cardiomyopathy.
• Malignancies Kaposi's sarcoma, malignant lymphomas Burkitt's lymphoma, primary brain lymphoma....

HIV Epidemiology

• The highest prevalence is in Africa (HIV-2).
• Generally, 60% homosexual sexual transmission + 30% heterosexual transmission + 10% i.v. drug addicts.

HIV Laboratory Diagnostics

• Detection of antibodies (ELISA)
• Detection of viral antigens P24, gp120, gp41 (Western blot)
• Detection of virus RNA (RT-PCR)
• Plasma viral load virus quantity in copies/ml
• Monitoring of CD4+ T-cells count.

Antiretroviral Therapy

• Combination of three or even more different antiretroviral drugs = cART (Combination Antiretroviral Therapy) to avoid resistance.
• Usually, two nucleoside inhibitors of reverse transcriptase (NRTI) and protease inhibitor.
• Can be two NRTI and one non-nucleoside inhibitor of reverse transcriptase.
• Still infectious and unable to kill whole virus but prevents AIDS

HIV Prevention and Prophylaxis

• Mandatory blood/tissues donors screening.
• Screening in pregnancy (CZ 1. trimester + 3. trimester).
• Sex education.
• Prohibition of breastfeeding in HIV+ women X does not apply to developing countries.

Hepatitis

• Different viruses – mainly RNA viruses except HBV (DNA virus).
• Causing similar basic hepatitis symptoms.
• Often asymptomatic manifestation.
• Flu-like symptoms.
• Icteric symptoms of jaundice and the liver enzymes increase.
• Hepatitis A: Picornavirus, RNA, Fecal-oral, 15-50 days incubation, Mild, No Chronicity, <0,5% Mortality, No Other diseases associations
• Hepatitis B: Hepadnavirus DNA, Parenteral/Sexual, 45-160 days incubation, Occasionaly Severe, Yes Chronicity, 1-2% Mortality, Primary Hepatocellular carcinoma or cirrhosis (Other Diseases)
• Hepatitis C: Flavivirus, RNA, Parenteral/Sexual, 14-180+ days incubation, Usually Subclinical, Yes Up to 70%, 4% Mortality, Cirrhosis or fulminant hepatitis with very high mortality to 80% (Other Diseases)
• Hepatitis D: Unclassified, RNA, Parenteral/Sexual, 15-64 days incubation, Co-infection w HBV, Yes Chronicity, High to Very High, None(Other Diseases)
• Hepatitis E: Calicivirus, RNA, Fecal-oral, 15-50 days incubation, Mild/Severe in pregnant women, No Chronicity, 1-2% (in women) to 20-40% Pregnant, None(Other Diseases)

Hepatitis A

• Picornavirus is non-enveloped, positive sense ssRNA.
• Spread by the fecal-oral route contaminated food, water resources.
• Incubation period of ca. 1 month.
• Does not cause chronic disease.
• Clinical symptoms will disappear within 8 weeks.
• High incidence in developing countries with poor hygiene and overpopulation Africa, India, SE Asia, Central America epidemics

Hepatitis A Diagnostics

• Serology
• detection of antibodies (indirect)
• RT-PCR (direct)

Hepatitis A Prevention and Therapy

• No antiviral therapy- only symptomatic
• Vaccination is optional, but is CZ obligatory for health-care workers in gastronomy and education etc.

Hepatitis B Virus

• The Hepadnavirus is enveloped dsDNA + ssDNA virus that's partially circular (very small – 3 200 bp).
• Virion is called "Dane" particle (42 nm in diameter).
• Includes enzymes proteinkinase polymerase.
• Consists of hepatitis B antigen (HBsAg) – envelope and is resistant to low pH, freezing, and heating.

Hepatitis B Epidemiology

• Causes acute or chronic disease with symptomatic or asymptomatic manifestation.
• Spread parenterally by blood or other body fluids needles, blood, transfusion, transplantation, sexual contact, perinatally.
• Incubation period approx. 3 months.
• Occurs in 5 – 10 % of patients → chronic hepatitis cirrhosis.
• Causally associated with primary hepatocellular carcinoma if not treated.
• HBsAg (S region), M-HBsAg (preS2 + S regions), L-HBsAg (preS1 + preS2 +S regions)

Hepatitis B Diagnostics

• Direct detection of HBsAg and HBeAg
• Detection of antibodies HBc-IgM, HBc-IgG
• PCR of viral DNA
• Causal therapy is available (antiviral drugs, INF)
• Vaccination (mandatory)

Hepatitis C Virus

• Enveloped, positive-sense ssRNA virus, Hepacivirus (Flaviviridae).
• RNA-dependent RNA polymerase.
• Has at least 6 genotypes and more than 50 subtypes.
• First isolation 1989 from chimpanzee.
• Often random mutations => immune system escape chronicity + difficult vaccine development
• Requires attachment, entry, processing, translation, replication, assembly and maturation

Hepatitis C Disease

• Incubation period 4 – 12 weeks.
• In 80% it turns into a chronic disease.
• Cirrhosis in 5-20% of cases.
• Can cause the development of hepatocellular carcinoma.

Hepatitis C Epidemiology

• Spreads parenterally blood, tissue transplants, perinatally, sexual transmission.
• 71 million of people infected all over the world.
• 1,75 million of people infected each year.
• 400 000 deaths.
• Highest prevalence Asia, Africa, Middle East, Russia, S and SE Europe.

Hepatitis C Diagnostics/Therapy/Prevention

• Detection of andibodies from laboratory diagnostics
• Detection of RNA by RT-PCR in laboratory diagnostics
• Ribavirin in combination with interferon and other antiviral drugs as therapy
• No vaccination or screening

Hepatitis D Virus

• SSA RNA from Daltavirus
• Dependent on replication of HBsAg present only in patients infected by hepatitis B virus (coinfection, superinfection).
• Endemic Latin America, Africa, Middle East, S Italy, Romania.
• 4% of patients with hepatitis B infection
• Usually spread by sexual contact, blood, and from mother to fetus.

Hepatitis E

• SsRNA enveloped virus from Hepevirus
• Spreads by fecal-oral route
• Is endemic in Asia, Africa, Central America, animal reservoirs (pigs, rats, birds)
• 3 millions of people infected each year and results in 44 000 deaths per year
• Incubation period lasts 3-8 weeks
• Characterized by hepatitis symptoms
• Presents a danger for pregnant woman with up to 20% mortality

Coronavirus

• Enveloped ssRNA virus that causes respiratory tract infections (common cold 10 – 15% of cases all over the world).
• Consists of different types of coronaviruses.

SARS-CoV

• Initially isolated in 2003 in China causing pandemic in 2002 in 30 countries 774 deaths.
• Mortality accounts for 10%, which is higher in elderly.
• Original source is bats and rodents.
• Incubation period 2- 14 days.
• Fever (>38 C.)
• Results in non-productive caught and hypoxia

MERS-CoV

• Described in Saudi Arabia in 2012.
• Identified in camels and bats (original source).
• Causes respiratory distress syndrome, kidney failure, & liver disorder.
• Mortality rate is 40%.

SARS-CoV-2 (COVID-19)

• Identified in Wu-Chan (China) in 2019.
• Caused pandemic due to high infectivity.
• Targets ACE2 receptor of host cells in humans and in animals.
• Originated in bats.
• Causes fever (>38° C), myalgia, non-productive caught, pneumonia, hypoxia and temporary loss of taste and smell.

SARS-CoV-2 Diagnostics

• Diagnosed through RT-PCR, antigen detection, and antibody detection.