Pathophysiology of Sexually Transmitted Infections PDF

Pathophysiology of Sexually Transmitted Infections Dr Ahmed Dowah [email protected]  Human Immunodeficiency Virus, HIV  Retrovirus  Enveloped, positive sense single-stranded RNA, reverse t...

Pathophysiology of Sexually Transmitted Infections Dr Ahmed Dowah [email protected]  Human Immunodeficiency Virus, HIV  Retrovirus  Enveloped, positive sense single-stranded RNA, reverse transcriptase  Polyhedral capsid  Spiked envelope  80-146 nm  2 variants of virus  HIV1 – predominant type of HIV throughout the world  HIV2 – found mainly in West Africa  50% sequence homology  Different kind of biology Normally we know that DNA is transcribed to RNA to make proteins Retroviruses transcribe DNA from RNA using reverse transcriptase Three steps  RNA-DNA hybrid made from +RNA genome using tRNA carried by virion. (-ssDNA produced)  RNA portion degraded by reverse transcriptase  Reverse transcriptase transcribes a complementary +ssDNA strand to create dsDNA  Replication cycle https://doi.org/10.3389/fmicb.2020.55 9792  Pathogenicity  Attachment to CD4 cells (Helper T cells)  Body fights the virus :HIV and cytotoxic T cells kill 100 million CD4 cells (Latent phase)  Body cannot make enough CD4 cells, so numbers decline over 5-10 years  HIV virus numbers increase  Other infections able to invade easily  AIDS – acquired immunodeficiency syndrome  Epidemiology  First discovered in young homosexual males in 1981 in USA  AIDS now found worldwide  There were an estimated 39.0 million people living with HIV at the end of 2022, two thirds of whom (25.6 million) are in the WHO African Region.  In 2022, 630 000 people died from HIV-related causes and 1.3 million people acquired HIV.  Sub Saharan Africa most affected area (71%)  Transmitted by sexual contact and intravenous drug abuse  Contact with bodily fluids can cause infection but rare  Symptoms  Symptoms from initial infection  Fever  Fatigue  Weight loss  Diarrhoea  Body aches  Onset of AIDS indicated by rare infections  Kaposi’s sarcoma  Disseminated herpes  Toxoplasmosis  Pneumocystis pneumonia  These infections are non -lethal in other patients  Diagnosis From initial symptoms (often mistaken for flu) Reduction in CD4 cells Serology testing for antibodies PCR of RNA for definitive test  Treatment  Anti-retroviral therapy (ART)  Cocktail of 3-4 different antiviral drugs  Nucleotide analogs  Integrase inhibitors  Protease inhibitors  Reverse transcriptase inhibitors  Expensive  Must be taken on a strict schedule  Stops replication  Vaccine  Development has difficult for several reasons  HIV highly mutable  HIV can spread through syncytia  HIV infects macrophages, dendritic cells, and Helper T cells – cells that normally would be activated by vaccine  Testing vaccine is ethically difficult as only humans affected  Human Papilloma virus (Genital warts)  Non-enveloped  Double-stranded circular DNA virus  HPV causes genital warts  Most common viral sexually transmitted infection (STI) diagnosed in the UK  The disease is transmitted mostly through sexual contact  Genital warts are small, rough lumps that can appear around the vagina, penis or anus  Human Papillomavirus (Genital warts)  In 90% of people the body controls the infection by itself.  Persistent HPV infection with high-risk HPV types is the cause of cervical cancer.  Cervical cancer is the most common type of cancer caused by HPV What is the treatment plan for this infection? How can this infection be prevented?  Trichomonas vaginalis  Parasite – protozoan  Obligate parasite – cannot live outside of human host  Transmitted exclusively via sex  Appears most frequently in people with other STI’s or with multiple sex partners  Life Cycle  Trichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate, where it replicates by binary fission  The parasite does not appear to have a cyst form, and does not survive well in the external environment  Symptoms women Men  Vaginosis  Generally asymptomatic  Purulent, odorous discharge  May cause inflammation of  Vaginal and cervical lesions the urethra and bladder  Abdominal pain  Painful urination  Painful sexual intercourse  Treatment and Diagnosis  Diagnosis by microscopic observation of trophozoites in vaginal and urethral secretions  Treatment with nitroimidazole drugs can work but should be aware that some strains are resistant  Summary  Pathogenesis of microbes  STI’s  Chlamydia  Gonorrhoea  Syphilis  Genital Warts/HPV  Genital Herpes  HIV / AIDS  Trichomonas vaginalis