Human Immunodeficiency Virus (HIV) and Hepatitis C Virus (HCV) co-infection is a multi-faceted, chronic condition that significantly impacts public health. According to the World Health Organization (WHO), 2 to 15% of those infected with HIV are also affected by HCV, increasing their risk of morbidity and mortality due to accelerated liver disease. The burden of co-infection is especially high in certain high-risk groups, such as intravenous drug users and men who have sex with men. These individuals who are HIV-positive are commonly co-infected with HCV due to shared routes of transmission including, but not limited to, exposure to HIV-positive blood, sexual intercourse, and passage of the Hepatitis C virus from mother to infant during childbirth.
Infection with HCV can be asymptomatic, resolve itself without treatment, or can lead to cirrhosis or cancer.
Signs and symptoms
Although symptoms of HIV and HCV mono-infection have been well-studied over the years, the symptoms associated with HIV and HCV co-infection remain a developing field of research. Many co-infected individuals report a difficulty in attributing their symptoms to a particular viral infection, indicating an overlap in symptoms of both diseases. This suggests that interventions aiming to reduce the disease burden associated with HIV and HCV co-infection must consist of strategies to manage symptoms of each individual infection.
In contrast to HIV and HCV co-infection, there has been significant research delineating the signs and symptoms of each of these individual illnesses. Common symptoms experienced by HIV-infected individuals include fever, night sweats, diarrhea, nausea, headache, and fatigue. On the other hand, symptoms associated with HCV infection include fatigue, depression, urticaria, peripheral neuropathy, joint pain, and irritability. Co-infected individuals can experience a range of these symptoms, with some studies showing fatigue to be the most prevalent symptom.
Risk factors
Due to the similar routes of transmission of HIV and HCV, HIV-positive individuals are at great risk of HIV and HCV co-infection. These routes of transmission include percutaneous blood exposure, sexual intercourse, and mother-to-child transmission. In the United States, injection drug use is known to be the most common mode of transmission of HCV. Some studies have shown that co-infection is significantly associated with older age as well as illicit intravenous and non-intravenous drug use, and HIV-infected individuals have a higher overall risk of HCV infection irrespective of intravenous drug use or other risk factors.
Mechanism
HIV
HIV is contracted by coming in contact with the bodily fluids of someone HIV positive. These fluids include blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk. An individual can become infected with HIV if these fluids enter the bloodstream by way of a mucous membrane, damaged tissue or injection. Common HIV routes of transmission include sharing needles, having unprotected sex with someone who is HIV positive, mother to fetus during pregnancy, being stuck with an HIV-contaminated sharp object, etc. Once the virus has entered the blood stream, it attaches to and enters t-helper cells (CD4 cells) in order to replicate. After reverse transcription, the new viral DNA integrates itself into the host cell's DNA and instructs the cell to produce viral proteins. These viral proteins bud off of the host CD4 cell and move on to infect other CD4 cells which is how the virus spreads in the body and destroys the immune system.
HCV
HCV is transmitted by coming in contact with the blood of someone infected with HCV. The virus is commonly spread by sharing needles, mother to infant during birth, improperly sterilized medical equipment, intercourse with an infected individual, and unregulated tattoos. Once inside the body, the virus enters the liver's hepatocyte cells via receptor-mediated endocytosis. Inside the cell, the viral RNA undergoes translation and at the end of the whole process, viral proteins are created. These proteins fuse with lipid droplets in the cytosol of the hepatocyte to form a cell known as a high-density HCV precursor. In the golgi apparatus, the HCV precursor cell fuses with two more cells before becoming the HCV lipoviral particle. HCV in this particle form is protected from antibody neutralization which would normally stop the virus from spreading. These lipoviral particles are released out of the hepatocyte to find other hepatocytes to infect.