Four scientists were trying to measure the effect of a new inhibitor X on the expression levels of transcription factor, HNF4alpha. They measured the inhibition levels by using RT-qPCR. In short they converted the total mRNA of the cells to cDNA (RT part), and used PCR to amplify the cDNA quantifying the amplification with a dsDNA binding dye (qPCR part). Which of the following group characteristics contains a virus(es) that has the enzyme necessary to convert the mRNA to cDNA used in the above scenario?
Q2
A 44-year-old with a past medical history significant for human immunodeficiency virus infection presents to the emergency department after he was found to be experiencing worsening confusion. The patient was noted to be disoriented by residents and staff at the homeless shelter where he resides. On presentation he reports headache and muscle aches but is unable to provide more information. His temperature is 102.2°F (39°C), blood pressure is 112/71 mmHg, pulse is 115/min, and respirations are 24/min. Knee extension with hips flexed produces significant resistance and pain. A lumbar puncture is performed with the following results:
Opening pressure: Normal
Fluid color: Clear
Cell count: Increased lymphocytes
Protein: Slightly elevated
Which of the following is the most likely cause of this patient's symptoms?
Q3
A 27-year-old man interested in pre-exposure therapy for HIV (PrEP) is being evaluated to qualify for a PrEP study. In order to qualify, patients must be HIV- and hepatitis B- and C-negative. Any other sexually transmitted infections require treatment prior to initiation of PrEP. The medical history is positive for a prior syphilis infection and bipolar affective disorder, for which he takes lithium. On his next visit, the liver and renal enzymes are within normal ranges. HIV and hepatitis B and C tests are negative. Which of the following about the HIV test is true?
Q4
A 32-year-old HIV positive male presents to the office complaining of difficulty swallowing and bad breath for the past couple of months. Upon further questioning, he says, "it feels like there’s something in my throat". He says that the difficulty is sometimes severe enough that he has to skip meals. He added that it mainly occurs with solid foods. He is concerned about his bad breath since he has regular meetings with his clients. Although he is on antiretroviral medications, he admits that he is noncompliant. On examination, the patient is cachectic with pale conjunctiva. On lab evaluation, the patient’s CD4+ count is 70/mm3. What is the most likely cause of his symptoms?
Q5
A 33-year-old man with HIV comes to the physician because of a nonproductive cough and shortness of breath for 3 weeks. He feels tired after walking up a flight of stairs and after long conversations on the phone. He appears chronically ill. His temperature is 38.5°C (101.3°F), and pulse is 110/min. Pulse oximetry on room air shows an oxygen saturation of 95%. Upon walking, his oxygen saturation decreases to 85%. Cardiopulmonary examination is normal. Laboratory studies show a CD4+ T-lymphocyte count of 176/mm3 (N > 500). Results of urine Legionella antigen testing are negative. A CT scan of the chest shows diffuse, bilateral ground-glass opacities. Microscopic examination of fluid obtained from bronchoalveolar lavage will most likely show which of the following findings?
HIV US Medical PG Practice Questions and MCQs
Question 1: Four scientists were trying to measure the effect of a new inhibitor X on the expression levels of transcription factor, HNF4alpha. They measured the inhibition levels by using RT-qPCR. In short they converted the total mRNA of the cells to cDNA (RT part), and used PCR to amplify the cDNA quantifying the amplification with a dsDNA binding dye (qPCR part). Which of the following group characteristics contains a virus(es) that has the enzyme necessary to convert the mRNA to cDNA used in the above scenario?
A. Enveloped, dimeric (+) ssRNA (Correct Answer)
B. Enveloped, circular (-) ssRNA
C. Nonenveloped, (+) ssRNA
D. Nonenveloped, ssDNA
E. Nonenveloped, circular dsDNA
Explanation: ***Enveloped, dimeric (+) ssRNA***
- This group describes **retroviruses**, which possess the enzyme **reverse transcriptase**.
- **Reverse transcriptase** is essential for converting their **RNA genome** into **cDNA**, a process analogous to the RT step in RT-qPCR.
- Examples include **HIV**, which is tagged to this topic.
*Enveloped, circular (-) ssRNA*
- This description does not accurately represent a major viral family.
- Most enveloped negative-sense RNA viruses have **linear or segmented genomes** (e.g., **Orthomyxoviruses**, **Bunyaviruses**), not circular.
- These viruses replicate using an **RNA-dependent RNA polymerase** to synthesize mRNA from their negative-sense RNA genome.
- They do not inherently carry or require **reverse transcriptase** for their life cycle.
*Nonenveloped, (+) ssRNA*
- These viruses, like **Picornaviruses**, directly use their positive-sense RNA as mRNA and replicate via an **RNA-dependent RNA polymerase**.
- They do not possess **reverse transcriptase** for cDNA synthesis.
*Nonenveloped, ssDNA*
- Viruses with a **single-stranded DNA genome**, such as **Parvoviruses**, replicate by first synthesizing a double-stranded DNA intermediate.
- Their replication machinery does not involve **reverse transcriptase** to convert RNA to DNA.
*Nonenveloped, circular dsDNA*
- Viruses in this group, like **Papillomaviruses** and **Polyomaviruses**, have a circular double-stranded DNA genome and replicate within the host nucleus using the host's DNA polymerase.
- They do not utilize or encode **reverse transcriptase** for their replication cycle.
Question 2: A 44-year-old with a past medical history significant for human immunodeficiency virus infection presents to the emergency department after he was found to be experiencing worsening confusion. The patient was noted to be disoriented by residents and staff at the homeless shelter where he resides. On presentation he reports headache and muscle aches but is unable to provide more information. His temperature is 102.2°F (39°C), blood pressure is 112/71 mmHg, pulse is 115/min, and respirations are 24/min. Knee extension with hips flexed produces significant resistance and pain. A lumbar puncture is performed with the following results:
Opening pressure: Normal
Fluid color: Clear
Cell count: Increased lymphocytes
Protein: Slightly elevated
Which of the following is the most likely cause of this patient's symptoms?
A. Herpes simplex virus
B. Group B streptococcus
C. Cryptococcus (Correct Answer)
D. Tuberculosis
E. Neisseria meningitidis
Explanation: ***Cryptococcus***
- **Cryptococcus neoformans** is the **most common cause of meningitis** in HIV-positive patients, particularly those with CD4 counts <100 cells/μL.
- The CSF findings are **classic for cryptococcal meningitis**: clear fluid, **lymphocytic pleocytosis**, normal or mildly elevated opening pressure, and **slightly elevated protein** with normal or mildly decreased glucose.
- The patient's **subacute presentation** with confusion, fever, and meningeal signs in the context of **HIV infection** strongly suggests cryptococcal meningitis as the most likely diagnosis.
- Diagnosis is confirmed with **CSF cryptococcal antigen**, India ink stain, or fungal culture.
*Herpes simplex virus*
- While HSV can cause meningitis or encephalitis, it is **not the most common cause** of meningitis in HIV-positive patients.
- **HSV encephalitis** typically presents with more prominent temporal lobe involvement, including personality changes, seizures, and focal neurological deficits.
- HSV meningitis is more common in **immunocompetent individuals** and would be less likely than cryptococcal infection in an HIV patient.
*Group B streptococcus*
- This causes **bacterial meningitis** with a **neutrophilic predominance** in CSF, not lymphocytic.
- CSF would show **markedly elevated protein**, **decreased glucose**, and cloudy appearance.
- More common in neonates and elderly patients, not typically associated with HIV.
*Neisseria meningitidis*
- This is a cause of **acute bacterial meningitis** with rapid onset and often a **petechial rash**.
- CSF would show **neutrophilic predominance**, **high protein**, **low glucose**, and turbid appearance.
- The lymphocytic pleocytosis rules out typical bacterial meningitis.
*Tuberculosis*
- **Tuberculous (TB) meningitis** is an important consideration in HIV-positive patients and can present with lymphocytic pleocytosis.
- However, TB meningitis typically shows **markedly elevated protein** (often >100 mg/dL, not "slightly elevated"), **low glucose** (<45 mg/dL), and may have a "spider-web clot" on standing CSF.
- The **more subacute to chronic course** (weeks) and absence of very high protein make TB less likely than cryptococcal meningitis in this acute presentation.
Question 3: A 27-year-old man interested in pre-exposure therapy for HIV (PrEP) is being evaluated to qualify for a PrEP study. In order to qualify, patients must be HIV- and hepatitis B- and C-negative. Any other sexually transmitted infections require treatment prior to initiation of PrEP. The medical history is positive for a prior syphilis infection and bipolar affective disorder, for which he takes lithium. On his next visit, the liver and renal enzymes are within normal ranges. HIV and hepatitis B and C tests are negative. Which of the following about the HIV test is true?
A. It is a quantitative test used for screening purposes.
B. It is a qualitative test used for screening purposes. (Correct Answer)
C. A secondary reagent is needed to interpret the results.
D. A known antigen binds directly to the patient's serum.
E. An unknown antigen binds to the known serum.
Explanation: ***It is a qualitative test used for screening purposes.***
- **HIV screening tests** (e.g., 4th generation antibody/antigen combination assays) are typically **qualitative**, meaning they detect the presence or absence of HIV markers, not their exact amount.
- These tests are primarily used for broad **screening** of populations to identify potential cases of HIV infection.
*It is a quantitative test used for screening purposes.*
- **Quantitative tests** for HIV, such as viral load tests, measure the amount of virus in the blood and are typically used for monitoring disease progression or treatment effectiveness, not for initial screening.
- Screening tests are designed for high sensitivity to detect infection, even with low viral loads or early antibody responses, making a quantitative measurement less relevant for initial screening.
*A secondary reagent is needed to interpret the results.*
- While some complex immunoassays might involve multiple steps, modern **HIV screening tests** often use advanced technologies that directly yield results, making a separate secondary reagent for interpretation generally unnecessary.
- The results are typically indicated by a color change or a signal detected by an instrument, without requiring an additional interpretive reagent.
*A known antigen binds directly to the patient's serum.*
- **HIV antibody tests** detect **antibodies** produced by the patient's immune system in response to HIV infection.
- In such tests, **known HIV antigens** (from the test kit) bind to **HIV-specific antibodies present in the patient's serum**, not to serum components directly.
- This option is incorrect because it omits the critical role of antibodies as the target molecules being detected.
*An unknown antigen binds to the known serum.*
- This statement describes a different type of immunological assay where an unknown antigen is being identified using a known antibody, which is contrary to how **HIV screening tests** for infection are typically structured.
- **HIV screening tests** use known components (e.g., HIV antigens or antibodies) in the test kit to detect unknown components (e.g., HIV antibodies or viral antigens) in the patient's sample.
Question 4: A 32-year-old HIV positive male presents to the office complaining of difficulty swallowing and bad breath for the past couple of months. Upon further questioning, he says, "it feels like there’s something in my throat". He says that the difficulty is sometimes severe enough that he has to skip meals. He added that it mainly occurs with solid foods. He is concerned about his bad breath since he has regular meetings with his clients. Although he is on antiretroviral medications, he admits that he is noncompliant. On examination, the patient is cachectic with pale conjunctiva. On lab evaluation, the patient’s CD4+ count is 70/mm3. What is the most likely cause of his symptoms?
A. Candida albicans (Correct Answer)
B. Human papilloma virus
C. Cytomegalovirus
D. HHV-8
E. Irritation due to medication therapy
Explanation: ***Candida albicans***
- The patient's presentation with **dysphagia** (difficulty swallowing), **bad breath**, and sensation of something in the throat, combined with **HIV positive status** and a very **low CD4+ count (70/mm³)**, is highly suggestive of **esophageal candidiasis**.
- **Esophageal candidiasis** is a common **opportunistic infection** in immunocompromised individuals, particularly those with advanced HIV (typically CD4+ <100/mm³), and presents with difficulty swallowing (especially solids), halitosis, sensation of food impaction, and can lead to malnutrition and cachexia.
*Human papilloma virus*
- While **HPV infections** can occur in HIV-positive individuals and cause squamous lesions, they typically manifest as warts or papillomas and are less likely to be the primary cause of such severe, obstructive dysphagia without other characteristic findings.
- HPV-related lesions in the esophagus are relatively rare and usually do not present with the specific "something in my throat" sensation or the degree of malnourishment seen in this patient due to diffuse candidal inflammation.
*Cytomegalovirus*
- **Cytomegalovirus (CMV) esophagitis** is a serious opportunistic infection in HIV patients with very low CD4+ counts (typically <50/mm³), and it can cause dysphagia.
- However, CMV esophagitis typically presents with **painful swallowing (odynophagia)** and **linear or deep ulcers** on endoscopy rather than the diffuse inflammation and white plaques characteristic of candidiasis. The patient's presentation of difficulty (not pain) with solids and the "something in the throat" sensation is more typical of candidiasis.
*HHV-8*
- **Human Herpesvirus 8 (HHV-8)** is primarily associated with **Kaposi's sarcoma (KS)**, which can affect the gastrointestinal tract, including the esophagus.
- While KS lesions in the esophagus can cause dysphagia, they are typically described as **purplish, raised lesions**, and the patient's symptoms of bad breath and a feeling of "something in my throat" are not the most common presentation for esophageal Kaposi's sarcoma.
*Irritation due to medication therapy*
- Although some medications, including certain antiretrovirals, can cause **pill esophagitis** or irritation, the patient's symptoms are chronic ("past couple of months"), severe enough to cause **cachexia**, and his **noncompliance** would make medication-induced irritation less likely to be the sole cause of such severe and prolonged symptoms.
- The patient's **compromised immune status** (low CD4+ count) strongly points towards an opportunistic infection rather than merely drug-induced irritation.
Question 5: A 33-year-old man with HIV comes to the physician because of a nonproductive cough and shortness of breath for 3 weeks. He feels tired after walking up a flight of stairs and after long conversations on the phone. He appears chronically ill. His temperature is 38.5°C (101.3°F), and pulse is 110/min. Pulse oximetry on room air shows an oxygen saturation of 95%. Upon walking, his oxygen saturation decreases to 85%. Cardiopulmonary examination is normal. Laboratory studies show a CD4+ T-lymphocyte count of 176/mm3 (N > 500). Results of urine Legionella antigen testing are negative. A CT scan of the chest shows diffuse, bilateral ground-glass opacities. Microscopic examination of fluid obtained from bronchoalveolar lavage will most likely show which of the following findings?
A. Silver-staining, disc-shaped cysts (Correct Answer)
B. Silver-staining, gram-negative bacilli
C. Septate, acute-angle branching hyphae
D. Gram-positive, catalase-positive cocci
E. Intracellular, acid-fast bacteria
Explanation: **Silver-staining, disc-shaped cysts**
- The patient's presentation with **nonproductive cough**, **shortness of breath**, fever, and **exertional hypoxemia** (desaturation upon walking) in the context of **HIV with a low CD4+ count (176/mm3)** is highly suggestive of **Pneumocystis pneumonia (PCP)**.
- **Pneumocystis jirovecii** (formerly *Pneumocystis carinii*) is the causative agent and is characterized by **disc-shaped cysts that stain with silver stains** (e.g., GMS stain) in bronchoalveolar lavage (BAL) fluid.
*Silver-staining, gram-negative bacilli*
- This description is characteristic of **Legionella pneumophila**, which can cause pneumonia, but the **urine Legionella antigen test was negative**, making this diagnosis less likely.
- While Legionella is a gram-negative bacillus and can be stained with silver, the overall clinical picture and negative antigen test point away from it.
*Septate, acute-branching hyphae*
- This morphology is characteristic of **Aspergillus species**, which can cause invasive aspergillosis, particularly in immunocompromised patients.
- However, aspergillosis typically presents with different radiological findings (e.g., nodules, cavitations, halo sign, or air crescent sign), and the clinical picture in this case is more typical of PCP.
*Gram-positive, catalase-positive cocci*
- This description is typical for **Staphylococcus aureus**, which can cause bacterial pneumonia.
- While *S. aureus* can cause pneumonia in immunocompromised patients, the diffuse **ground-glass opacities** and exertional hypoxemia, coupled with a low CD4 count, are not typical for staphylococcal pneumonia.
*Intracellular, acid-fast bacteria*
- This morphology is characteristic of **Mycobacterium species**, such as **Mycobacterium tuberculosis** or **Mycobacterium avium complex (MAC)**.
- While TB and MAC infections are common in HIV patients with low CD4 counts, they usually present with different radiological patterns (e.g., cavitations, lymphadenopathy for TB; disseminated disease for MAC) and the sudden onset of profound exertional hypoxemia is less typical.
