Overview Snapshot A 24-year-old man presents to his primary care physician with fever, headache, sore throat, and myalgias. He reports his symptoms began a few days ago and believes it is from a "cold." Social history is significant for having multiple male partners. He does not consistently use condoms. His last sexual encounter was 2 months ago. Physical exam is significant for cervical lymphadenopathy. An HIV-1/2 antigen/antibody combination immunoassay is positive for p24 antigen and an elevated HIV viral load. HIV-1/2 antibody differentiation immunoassay shows that he is solely HIV-1 reactive. Introduction Human immunodeficiency virus (HIV), an RNA retrovirus, can result in acquired immunodeficiency syndrome (AIDS) via gradually losing competence of the host's immune system, which results in opportunistic infections such as Pneumocystis jiroveci Toxoplasma gondii Mycobacterium avium-intracellulare HHV-8 Pathogenesis HIV infects CD4+ cells via binding to the CD4 receptor and co-receptors such as CCR5 on macrophages in early infection clinical correlate homozygous CCR5 mutations leads to immunity against HIV infection heterozygous CCR5 mutations leads to a slower infectious course CXCR4 on T cells in late infection the infected cells (CD4+ T-cells, dendritic cells, and macrophages) eventually serve as a reservoir for the virus which delivers the virus throughout the body HIV structure the viral particle contains two copies of an RNA genome as well as gp120 and gp41 result from the cleavage of gp 160 arise from the env gene gp120 allows for the attachment to the host's CD4+ cells allows for antigenic drift leading to evasion of antibody-mediated destruction gp41 allows for viral fusion and entry into the host cell p24 and p17 arise from the gag gene and serves as the viral capsid (p24) and viral matrix protein (p17) the pol gene leads to the synthesis of reverse transcriptase which synthesizes dsDNA from RNA in order to integrate the reversed transcribed viral DNA into host's DNA aspartate protease integrase which integrates the reverse transcribed DNA into the host's genome Diagnosis HIV-1/2 antigen/antibody combination immunoassay if positive for HIV-1/2 antibodies or HIV p24 antigen then perform an HIV-1/2 antibody differentiation immunoassay viral load determines the HIV RNA amount in the patient's plasma Opportunistic Infections Based on CD4+ Cell Count Cell Count (cells/mm3) Pathogen & Disease(s) < 500/mm3 Candida albicans oral thrush Bartonella henselae bacillary angiomatosis Epstein–Barr virus (EBV) oral hairy leukoplakia HHV-8 Kaposi sarcoma HPV squamous cell carcinoma of theanus and cervix < 200/mm3 Pneumocystis jirovecii pneumonia Reactivation of the JC virus progressive multifocal leukoencephalopathy Histoplasma capsulatum nonspecific symptoms such as fever, weight loss, and cough along with oval yeast cells within macrophages < 100/mm3 Candida albicans esophagitis Aspergillus fumigatus hemoptysis and pleurisy Mycobacterium avium-intracellulare and mycobacterium avium complex nonspecific findings such asfever, weight loss, and night sweats Toxoplasma gondii brain abscesses that can appear as ring-enhancing lesions on MRI Cryptococcus neoformans meningitis Cryptosporidium species watery diarrhea Epstein–Barr virus (EBV) B-cell lymphoma Cytomegalovirus retinitis esophagitis colitis encephalitis pneumonitis