Retroviridae

1) Virus infects monocytes but doesnt replicate until the monocyte moves into the tissues and becomes a macrophage 2) Virus replicates in macrophage and then spreads to lymphocytes 3) Viruses no inside cells attatch to the surface of red blood cells 4) Ab mediate phagocytosis of these attatched viruses + RBC and complement mediated lysis of RBCs happens due to altered membranes 5) Leads to anemia and thrombocytopenia

Equine Infectious Anemia Virus (Swamp Fever) + Pathogenesis: Explain the pathogenesis in a chronic infection

Petechial hemorrhages and edema

Equine Infectious Anemia Virus (Swamp Fever) + Pathogenesis: What are the secondary effects/CS of thrombocytopenia?

* Anemia, fever and swollen belly and legs (edema) Lethargy Weight loss Enlarged spleen Depression Decreased athletic performance Death (in rare cases when there are underlying disease)

Equine Infectious Anemia Virus (Swamp Fever): CS

- Via biting insects and contaminated instruments (blood) - Virus is shed in all secretions - Venereal - virus passed in semen - In utero - foals can be infected before birth - Milk, colostrum

Equine Infectious Anemia Virus (Swamp Fever): Transmission

STress or steroids (immunosupression)

Equine Infectious Anemia Virus (Swamp Fever): What can cause an asymptomatic carrier to have a reappearance of the clinical symptoms

* Best => ELISA and PCR - Agar gel immunodiffusion (AGID or Coggins test - not used anymore, used to be the gold standard) - ELISA kit (Ab detection - Replaced AGID) - Immuno blot (more for research) - Complement enzyme linked immunosorbent assay (cELISA)

Equine Infectious Anemia Virus (Swamp Fever): What diagnostic tests can we run?

They can not be shipped in or out of the US and canada - Must test negative with a health cert to do so

Equine Infectious Anemia Virus (Swamp Fever): What happens to animals when they test positive for this virus in terms of movement?

Lentivirus - Causes per-acute (rare) or acute/chronic disease - Most infected horses are inapparent/asymptomatic carriers **Notifiable Disease in the US

Equine Infectious Anemia Virus (Swamp Fever): What kind of virus is this and what kind of diseases does it cause?

- ELISA => detects antigens and anti-FIV Ab; most common, rapid and reliable (doesnt work well in early infection) ** ALWAYS repeat this test to ensure result - Immunoblotting => Ab to detect FIV related proteins - PCR => detects viral DNA, useful for kittens born from FIV positive mother (check for false positives)

Feline Immunodeficiency Virus (FIV) + Diagnosis: What can we use to diagnose?

1) Replicates in CD4 T cells (main), B cells and macrophages 2) Binds to CD13 (TNFRSF4) and CD184) (CXCR4) on activated CD4 cells (highly expressed when the immune system is activated) 3) Causes infection of CD4 cells and reduces numbers 4) Causes IL-2 reduction and overall lymphopenia - FIV activates CD4/CD25 Treg cells in which their role is to increase IL-10 production and deepen immunosupression

Feline Immunodeficiency Virus (FIV) + Pathogenesis: Explain how this virus causes immunodefficiency

- Isolate infected cats and keep away from feral cats - Vaccinate - Spay and neuter outdoor cats and limit exposure by decreasing agressive behaviors

Feline Immunodeficiency Virus (FIV) + Prevention: How can we prevent the spread to other cats?

FIV cured vax availible but it does not provide full protection against all strains - Since it is a killed virus, adjuvants are used (possibility of vaccine associated sarcomas) - Vaccinated cats will always be FIV antibody positive (can be a problem if lost and placed in a shelter)

Feline Immunodeficiency Virus (FIV) + Prevention: Vaccination?

- No treatment to eliminate the virus, only symptomatic - Antibiotics for secondary infections, appetite stimulants, immunomodulatora and dental extractions if chronic gingivitis and stomatitis is present. - Some may require nutritional support and fluid therapy. - There are some anti-viral medications but tey are not very good they end up being more toxic to the cat

Feline Immunodeficiency Virus (FIV) + Treatment: How can we treat?

*Lentivirus (slow virus) - Long incubation period up to 6 years and will develop into feline immunodefficiency (disease name) - Disese attacks the immune system and weakens its response to cancers

Feline Immunodeficiency Virus (FIV): How is this virus categorized and what is the disease?

* Lymphoid tissue (good for samples) - Leads to immunosupression through the attack of the T cells and reduces their numbers

Feline Leukemia (FeLV) + Pathogenesis: What is the tropism for this virus and hat is the consequence?

* Deep bite wounds and scratches from an infected cat and its saliva - Passed from mother to kitten during parturition - In utero and through milk rare (only occurs if the mother is infected DURING pregnancy, not before) - Sexual contact not a major issue - Infected queens before pregnancy will have non-infected kittens

Feline Immunodeficiency Virus (FIV): Transmisison

- Poor coat - Consistent fever - Loss of appetite and lethargy - Gingivitis and stomatitis - Chronic/recurrent skin, urinary bladder and upper resp tract infections - Persistent diarrhea - Feline lymphocytic plasmacytic gingivitis (LPGS) * Slow and progressive weight loss and severe wasting - Cancer and blood diseases - Abortions in queens that become infected while pregnant - Neuro signs -> seizures, behavioral changes ect

Feline Immunodeficiency Virus (FIV): What are the CS

*Can infect any age cat - Outdoor, free roaming cats at greater risk - Males 1.5-3x more likely due to agressive behavior

Feline Immunodeficiency Virus (FIV): What are the presidposing factors?

About 1.5-3% of all cats in the USare infected (healthy cats)

Feline Immunodeficiency Virus (FIV): What is the prevelance?

Yes Wild felines are affected such as snow lepords, mountain lions, florida panthers ect

Feline Immunodeficiency Virus (FIV): Will it affect more then just domestic cats?

Real Time PCR and Reverse Transcriptase PCR - Reverse transcriptase PCR => isolates RNA, reverse transcribes it and then PCR it

Feline Leukemia (FeLV) + Diagnosis: What are the best methods to use?

- SNAP FIV/FeLV combo (clinic) - p27 ELISA => sensitivity 90%, antigen detection - Immunoflorescence assay (IFA) => first test to be created, may be expensive annd not practical - Virus isolated culture => old gold standard test; now difficult and not routine - Real time PCR => detects RNA or DNA in asymptomatic animals - Reverse Transcriptase PCR => detects viral RNA in clinically affected animals - Serology => detects Ab against FeLV (hard to interpret because it could also be Ab from endogenous forms; little clinical value)

Feline Leukemia (FeLV) + Diagnosis: What are the tests that we can run?

Sick cats, cats with known recent exposure to an FeLV cat and cats living in households with other cats infected with FeLV - Cats with high risk lifestyles - Cats that donate blood or tissue - Before initial vax - Test before adoption and after escape if indoor cat

Feline Leukemia (FeLV) + Diagnosis: What cats should be tested?

Young age (highly susceptible when transitioning from maternal Ab to making their own) High pop density Poor hygine

Feline Leukemia (FeLV) + Epidemiology: Risk factors

- Will not survive outside of the host for long, destroyed readily by disinfectants, spao, heating and drying - FeLV low in single cat house holds (1%) - Prevelance in multi cat house holds may be over 20%

Feline Leukemia (FeLV) + Epidemiology: Stability in the environment and prevelance

Mainly via mutual grooming and bites

Feline Leukemia (FeLV) + Epidemiology: Transmission

* Cats that have FeLV viremis - Shed in saliva, nasal secretions, feces and milk

Feline Leukemia (FeLV) + Epidemiology: What are some sources of infection for non-infected cats

- Viremic queens will have embryonic death, still births or viremia in the kittens and the virus can be transmitted from the mammary glands - Young kittens are highly susceptible but older cats become somewhat resistant

Feline Leukemia (FeLV) + Epidemiology: What are the trends with viremic queens and age?

- Keep strictly indoors to prevent spread to feral cats - Minimise exposure of FeLV cats to other infectious agents (immunosupressed)

Feline Leukemia (FeLV) + Management: How can we manage these cats once they have the virus?

*Treat for the symptoms and treat any secondary infections - There is a vax but it doesnt prevent getting the disease, it will only lessen the symptoms

Feline Leukemia (FeLV) + Management: Is there a vaccine and how do we treat?

- Abortive infection/regressor cat => Develop good immune response and clears virus completely - Regressive/transient viremia => What most cats develop; may have CS, immune system is working but cant clear virus compleatly - Progressive infection/viremia => Full viremia and cat can either become a latent carrier or progress to clinical disease and death - Latent infection => Can either become a regressor cat or progress to clinical disease and die

Feline Leukemia (FeLV) + Outcomes: What are the possible outcomes of infection?

- Regenerative anemia (rare) caused by secondary opportunistic infections - Non-regenerative anemia (more common) caused by chronic inflammatory mechs, myelodestruction, myelosupression and myeloproliferative disease - Lymphomas and leukemias

Feline Leukemia (FeLV) + Outcomes: What can we see in the bloodwork?

Bite wounds, swollen lymph nodes, dehydration , neuro signs (chronic), persistent fever, weight loss, abcesses and immunosupression by secondary infections

Feline Leukemia (FeLV) + Outre comes: What athe CS?

1) Viral protein p15e blocks T cell receptors to IL-1, IL-2 and blocks production of hematopoetic cells leading to anemia 2) Reduces IgM levels and IgG normal 3) B cells unaffected, produce Ab which leads to deposition of Ag-Ab complexes and eventually glomerulonephritis (type III hypersensitivity)

Feline Leukemia (FeLV) + Pathogenesis: Explain the pathogenesis of how the virus acts on a cellular level

Attacks T cells through their receptors: - Phosphorus transportation protein (Pit 1) - FeLIX (FeLV infectivity X-essory protein)

Feline Leukemia (FeLV) + Pathogenesis: Explain what it will do the the T lymphocytes

- Infects through the oral or pharyngeal assoaciated tissue and replicates - Will then spread to periphereal tissues through infected monocytes and lymphocytes - Viremia will then develop within a few weeks of infection

Feline Leukemia (FeLV) + Pathogenesis: How will infection be aquired and how will it start?

There is little to no cellular immunity

Feline Leukemia (FeLV) + Pathogenesis: IS there cellular immunity?

The surface glycoprotien (SU) - Can change what the virus binds to

Feline Leukemia (FeLV) + Pathogenesis: What determines pathogenisity of the virus?

Infectious peritonitis, mycoplasmosis, toxoplasmosis and fungal infections

Feline Leukemia (FeLV) + Pathogenesis: What kind of infections will the immunosupression caused leave the cat predisposed to?

Develop during recurrent infections - Depending on the severity of the secondary infections there may be atrophy or hyperplasia of lymphoid tissue

Feline Leukemia (FeLV) + Pathogenesis: What will cause wasting syndrome and atrophy of the thymus?

- A = ubiquitous and involved in every infection (most common - B = recombination of FeLV A with enFeLV (endogenous and exogenous forms combine) - C = results from mutations in the env gene of FeLV - T = tropism for T lymohocytes

Feline Leukemia (FeLV): What are the 4 subtypes?

Exogenous form Endogenous feline leukemia virus (enFeLV)

Feline Leukemia (FeLV): What are the forms that this virus comes in?

- Envelope gene (env) that encodes for the glycoprotein gp70(SU) and transmembrane protein p15E (TM) - Polymerase gene (pol) coding for reverse transcriptase, protease and integrase - Gag gene codng for structural proteins like p27

Feline Leukemia (FeLV): What are the three important genes that these viruses contain?

Gammaretrovirus effecting cats worldwide

Feline Leukemia (FeLV): What kind of virus is this?

Use the integrase enzyme - Integrate randomly into the host RNA (now a pro-virus) and then that RNA will be integrated into the geneome

General: How are they able to integrate their geneome into the host geneome?

May alter or aquire host geneome sequences and may activate or inactivate particular host genes located near the integration site

General: What can the viral RNA sequences do to the host geneome?

- Enveloped RNA viruses that get their envelope from budding (most wont damage cell upon exit but some will lyse) - Diploid geneome with 2 copies of single stranded positive sense RNA

General: What is their structure?

1) Normal cell infected with retrovirus (normal) 2) Retroviral dsRNA integrated into the host cell DNA and replication occurs 3) Attatched host gene undergoes mutation and becomes an oncogene 4) Virus with oncogene is released from host cell and goes to infect other cells 5) New cells infected with the retrovirus carrying the oncogene now have it integrated in their geneome

Oncogenesis: Explain the process of the proro-oncogene becoming a viral oncogene

They undergo mutations that removes the regulatory mechanisms for growth - Results in transformation of infected cells by acting as a growth factor, receptor, intracellular signal transducer or intracellular transcription factor

Oncogenesis: What happens for these c-onc to become v-onc?

Proto oncogenes (required for normal cell growth and division

Oncogenesis: What kind of genes will cells have for normal growth?

They get cellular proto-oncogenes and these genes then become viral oncogenes (v-onc)

Oncogenesis: What will retroviruses aquire during replication?

Susceptible to lipid solvents or detergents and heating and can become easily inactivated

Retrovirus Morphology: What are these virons susceptible to due to their lipid envelope?

Resistant to ultraviolet and X rays

Retrovirus Morphology: What are these viruses resistant to?

- Two single stranded viral RNAs - Reverse transcriptase - Integrase - Protease

Retrovirus Morphology: What is inside the nucleocapsid?

- Diameter = 80-100 nm - Each RNA geneome is 7-11 kb and has a 3'-5' orientation

Retrovirus Morphology: What is the diameter of the viron and how long is the geneome?

- Virons are spherical and are surrounded by a lipid bilayer envelope - Have envelope glycoprotein projections useful in diagnosing and in pathogenesis

Retrovirus Morphology: What is their shape and structure of the envelope?

The matrix (replication role) and an a nucleocapsid that contains the viral RNA

Retrovirus Morphology: What lays beneath the envelope?

Encodes viral envelope proteins, surface (SU) and transmembrane (TM) proteins

Retrovirus Properties: Env gene

*Encodes for viral core proteins: - Capsid (CA) - Nucleoprotein (NC) - Matrix (MA)

Retrovirus Properties: Gag gene

Encodes reverse transcriptase (RT) and integrase (IN)

Retrovirus Properties: Pol gene

Encodes for the protesase (some viruses will have a different gene code for this)

Retrovirus Properties: Pro gene

Gag, pol, env and pro

Retrovirus Properties: What are the 4 important genes?

1) Receptor binding and membrane fusion 2) Internalization and uncoating 3) Reverse transcription of RNA geneome to form linear strands (dsRNA) 4) Nuclear entry of dsRNA 5) Integration of dsRNA into host geneome via integrase = provirus 6) Transcription of provirus to form viral RNA 7) SPlicing and nuclear transport to the cytoplasm 8) Translation of RNA to form precursor proteins 9) Assembly of virons and packaging of viral RNA geneome 10) Budding and release of virons 11) Proteolytic processing of precursors and maturation of the virons

Retrovirus Replication: Explain the steps in replication of these viruses

1) Virus induces transformation to malgnant cells 2) Chronic infection with intermitten signs 3) Latent infection 4) Release of virus by budding or lysis after re-actvation from stress

Retrovirus Replication: What are the outcomes of a retrovirus infection?

- There are 30 molecules of RT in each viron * RT is required for all retroviruses to replicate, without it they can not and will not replicate

Reverse Transcriptase: How many molecules are in each viron and what is this required for?

RNA Dependent DNA polymerase DNA dependent DNA polymerase RNase H -> cuts off RNA after reverse transcription

Reverse Transcriptase: What will RT serve as (3 things)?

Aka retroviral elements, viruses included in the geneome of most if not all animals - Transmitted vertically as part of the host geneome - Passed generationally

Subfam Orthoreovirinae + Alpharetrovirus: What are endogenous viruses?

Viruses obtained horizontally and are rarely transmitted in utero or germline formation - Most alpharetroviruses are exogenous

Subfam Orthoreovirinae + Alpharetrovirus: What are exogenous viruses?

*Mostly exogenous and endogenous viruses of chickens* Avian leucosis Sarcoma virus (ALSV) Avian myeloblastosis virus Rous sarcoma virus

Subfam Orthoreovirinae + Alpharetrovirus: What are the viruses in this group?

- Reffered to as simple viruses - Genes gag, pro, pol and env

Subfam Orthoreovirinae + Alpharetrovirus: What kind of viruses are these and what are the genes they have in their geneome?

* Complex viruses (more than the 4 genes) - Human T-lymphocytic virus (HTLV) - Bovine leukemia virus

Subfam Orthoreovirinae + Deltaretroviruses: What kind of viruses are these and what are the members?

*Complex viruses * Represented by Walleye dermal sarcoma virus (the only endogenous retroviruss found in fish and reptiles)

Subfam Orthoreovirinae + Epsilonretroviruses: What kind of viruses are these and what virus represents this category?

These are retroviruses of reptiles and mammals - Both exogenous and endogenous members

Subfam Orthoreovirinae + Gammaretroviruses: Are these viruses exogenous or endogenous and what animals do they infect?

Simple viruses - Has the largest number of members: - Murine leukemia virus - Feline leukemia virus - Feline sarcoma virus - Avian reticuloenotheliosis virus

Subfam Orthoreovirinae + Gammaretroviruses: What are these viruses considered and what are the members?

Humman immunodefficiency virus (HIV) Feline immunodefficiency virus (FIV) Caprine arthritis-encephalitis virus Maedi-visna virus

Subfam Orthoreovirinae + Lentiviruses: What are the most important members of this group?

Complex virus with a cylindrical or conical shaped head

Subfam Orthoreovirinae + Lentiviruses: What kind of viruses are these and what is their shape?

They have a long incubation period (months to years)

Subfam Orthoreovirinae + Lentiviruses: Why are these called slow viruses?

Acute transformation or chronic transformation

Transformation: Ddepending on the presence of key transforming genes in the viral geneome, infections with retroviruses may lead to what?

They have the ability to insert a gene or cause a mutation through random integration into the host geneome

Transformation: What allows a retrovirus to cause a chronic transformation?

They will contain viral oncogenes (v-onc)

Transformation: What allows a retrovirus to cause acute transformation?