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By Dr. Priyom Bose, Ph.D. Reviewed by Danielle Ellis, B.Sc.

What happens after HIV infection?
Evolution of HIV diagnostic assays
Conclusions
References
Further reading

Acquired immunodeficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV) that attacks the body’s immune system, making it vulnerable to all infections. One of the major concerns of the early AIDS epidemic that began in 1981 was the lack of proper diagnostic measures to identify infected individuals.1 Since the development of the first HIV diagnostic assay in 1985, scientists have continued to improve diagnostic accuracy, detection speed, and cost.

Image Credit: Hanna Karpiak/Shutterstock.com What happens after HIV infection?

The immune system produces antibodies after encountering harmful foreign substances or antigens. HIV infects the vital cells associated with immunity, such as macrophages, helper T cells, and dendritic cells, and disrupts their function. The three important HIV antigens are p24, gp 41, and gp 120.2

HIV is a slow-replicating retrovirus that is transmitted through sexual intercourse, sharing an infected needle, or by blood transfer.3 After HIV infection, the viral load cannot be measured immediately due to low plasma load. Typically, the viral RNA can be measured within 10 to 12 days after infection.4

Antibodies to p24 and gp 41 are the first serological markers used to detect HIV infection. IgG antibodies appear approximately three weeks after infection. In the majority of HIV-infected individuals, HIV antibodies appear to circulate within 1 to 2 months of the infection. However, in a few cases, it may take up to six months to appear at a detectable level.5 Evolution of HIV diagnostic assays

Over the years, scientists have developed many immunoassays and nucleic acid amplification tests (NAATs) to accurately and high-throughput HIV diagnosis. These tests are broadly divided into two categories, namely, screening and confirmatory tests. Typically, HIV tests are performed on blood, oral fluids, or urine samples.6

HIV screening is performed by various immunoassays that focus on detecting IgG antibodies against HIV-1 antigens in the serum. Techniques such as Western blot, line immunoassay (LIA), and recombinant immunoblot are used as confirmatory tests.7 Some of the important HIV diagnostic assays are discussed below: Serological testing for HIV

In the mid-1980s, simple serological tests for HIV antibodies were developed based on culture-derived viral antigen preparation.7 These tests enabled HIV diagnosis and assessed blood and blood product supplies. Since the early assays, various serological assays have been developed that aided simple/rapid testing, high-throughput screening, confirmatory tests, incidence determination, and epidemiological surveillance. Since its first development, five generations of enzyme immunoassays (EIAs) have emerged based on varied antigen preparations and detection chemistries.8

First-generation assays: The first-generation EIAs detect IgG antibodies from antigens derived from whole viral lysates of HIV-positive cultures. Since crude antigen lysate contains impurities, this method exhibited reduced specificity and high false positivity. In contrast, immunofluorescence assays or Western blotting (WB) have shown higher specificity and lower false positivity.

Second-generation assays: Second-generation assays involve the use of recombinant proteins or synthetic peptides derived from the immunodominant regions (IDR) of HIV-1 proteins and gp36 of HIV-2, which increases sensitivity and decreases false positivity.

Third-generation assays: Third-generation assays, including the Genetic Systems HIV-1/HIV-2 Plus O EIA, use a variety of antigens to detect HIV-1 and -2 antibodies in the serum. A major advantage of third-generation sandwich format assays is their ability to detect HIV-1 IgM antibodies early, enabling quicker HIV diagnosis.

Fourth-generation assays: The fourth-generation EIAs, including the Abbott Architect HIV Ag/Ab Combo assay, utilize fully automated chemiluminescent microparticle technology that can instantaneously identify antibodies to HIV-1 and HIV-2 and HIV-1 p24 antigen. This technique has further allowed early HIV diagnosis. Other advantages of fourth-generation high-throughput assays are their capacity to perform more than 150 tests per hour and their ability to test specimens immediately upon arrival and generate results within 30 minutes.  These assays are suitable for facilities, such as blood banks, that handle high volumes of blood samples.

Fifth-generation assays: Fifth-generation assays, such as the Bio-Rad BioPlex 2200 HIV Ag-Ab assay, use magnetic beads coated with p24 monoclonal antibodies and epitopes specific for HIV-1 and HIV-2. This type of assay has a major advantage in  that it can confirm HIV infection in a single test. Interested in Assay Kits? Explore Equipment Here

Despite the advancements in EIA assays, the challenges associated with the generation of false positive results persist. Therefore, EIA-reactive specimen is typically retested with supplemental tests, such as Western Blot. Rapid diagnostic tests Related StoriesSweden exceeds UNAIDS HIV goals but faces new challengesNutrition's pivotal role in combating tuberculosis: addressing N-AIDS for better outcomes

The first HIV rapid test was available in the early 1990s. It determined an individual's serostatus before surgery, maternal labor/delivery, and organ transplant. Rapid diagnostics is based on immunochromatographic technology that uses blood from finger pricks to assess HIV status. 9 This test can provide results in less than 30 minutes and can be used in point-of-care (POC) settings. Since this test presents both false positive and negative results, it is essential to confirm the findings with laboratory-based HIV assays.

The main advantage of this technique is that any non-laboratory staff can perform it in a primary health care center. Even though decentralization of HIV diagnostic services has increased HIV test service in remote areas, it has been challenged by the lack of national guidelines, waste disposal, inventory management, and quality assurance (QA) monitoring.10

HIV self-testing, based on rapid testing methods, has allowed individuals who would otherwise refrain from testing in fear of discrimination to perform the test privately and start proper intervention. The World Health Organization (WHO) has prequalified several HIV rapid tests for HIV self-testing, including the Insti HIV-1/HIV-2 antibody tests and the Oraquick rapid HIV-1/2 antibody test.10 Nucleic acid test (NAT)

The NAT identifies HIV nucleic acid, i.e., either RNA or proviral DNA, in the blood sample. This test is based on the principles of polymerase chain reaction (PCR), nucleic acid sequence-based amplification, or ligase chain reaction.11 This test has proved to be vital in situations when an antibody against HIV is absent in serum. NAT is also performed in newborns of HIV-infected mothers. Unlike other assays, this test can detect HIV even after recent or possible exposure to the virus. Furthermore, NAT can quantify viral load.

Revolutions in Infectious Disease Testing Conclusions

The advancements in HIV diagnostic assays have played a vital role in identifying, staging, and monitoring infected individuals, even when they are under antiretroviral therapy. These assays have played an important role in surveillance and identification of transmission hot spots. Extraordinary progress in HIV testing methodologies has not only reduced false positives but decreased assessment time as well. References Sharp PM, Hahn BH. Origins of HIV and the AIDS pandemic. Cold Spring Harb Perspect Med. 2011;1(1):a006841. doi: 10.1101/cshperspect.a006841. Foster JE., et al. Viruses as Pathogens: Animal Viruses, With Emphasis on Human Viruses. Viruses. 2018; 157-187. doi.org/10.1016/B978-0-12-811257-1.00007-3 Dasgupta A, Wahed. Human immunodeficiency virus (HIV) and hepatitis testing. Clinical Chemistry, Immunology and Laboratory Quality Control (Second Edition). 2021; 513-533. doi.org/10.1016/B978-0-12-815960-6.00015-7 Konrad BP, et al. On the duration of the period between exposure to HIV and detectable infection. Epidemics. 2017; 20, 73-83. doi.org/10.1016/j.epidem.2017.03.002 Davis LE. Acute viral meningitis and encephalitis. Infections of the Nervous System, 1987; 156-176. doi.org/10.1016/B978-0-407-02293-5.50014-3 Pant PN. Oral fluid-based rapid HIV testing: issues, challenges and research directions. Expert Review of Molecular Diagnostics. 2007; 7 (4), 325-328, DOI: 10.1586/14737159.7.4.325 Abdullah DM, et al. The contemporary immunoassays for HIV diagnosis: a concise overview. Asian Biomed (Res Rev News). 2023;17(1):3-12. doi: 10.2478/abm-2023-0038. Alexander TS. Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution. Clin Vaccine Immunol. 2016;23(4):249-53. doi: 10.1128/CVI.00053-16. Aidoo S, et al. Suitability of a rapid immunochromatographic test for detection of antibodies to human immunodeficiency virus in Ghana, West Africa. J Clin Microbiol. 2001;39(7):2572-5. doi: 10.1128/JCM.39.7.2572-2575.2001. Parekh BS, et al. Diagnosis of Human Immunodeficiency Virus Infection. Clin Microbiol Rev. 2018;32(1):e00064-18. doi: 10.1128/CMR.00064-18. Garrett, P. E. Quality control for nucleic acid tests: Common ground and special issues. Journal of Clinical Virology. 2001; 20(1-2), 15-21. doi.org/10.1016/S1386-6532(00)00150-5

Further ReadingAll HIV ContentThe Economic Impacts of AIDSRecent Advancements in Treating HIV

Last Updated: Nov 29, 2024

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Counter-terrorism police investigating after two women injured in Leeds

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Counter-terrorism police investigating after two women injured in Leeds

Counter-terrorism police are investigating after an incident involving a crossbow and a firearm left two women injured in Leeds.

Police were called to Otley Road at 2.47pm on Saturday to reports of a “serious incident involving a man seen with weapons”, West Yorkshire Police said.

Officers arrived at the scene to find two women injured – and a 38-year-old man with a self-inflicted injury. All three were taken to hospital, with the man held under arrest, but their injuries are not believed to be life-threatening.

“Two weapons have been recovered from the scene, which were a crossbow and a firearm,” Counter Terrorism Policing North East said in a statement.

The incident happened on the ‘Otley Run’ pub crawl, with one venue saying it was closed for the evening due to “unforeseen circumstances”.

Officers guard one of the crime scenes in Leeds
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Officers guard one of the crime scenes

Officers inside the cordon in Leeds
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Officers inside the cordon in Leeds

Counter Terrorism Policing’s statement added: “Due to the circumstances surrounding the incident, Counter Terrorism Policing North East have taken responsibility for leading the investigation with the support of West Yorkshire Police.

“Extensive enquiries continue to establish the full circumstances and explore any potential motivation.”

Home Secretary Yvette Cooper described it as a “serious violent incident” and said she was being kept updated by police.

“Thank you to the police and emergency services for their swift response,” she said. “My thoughts are with the victims and all those affected by this attack.”

This breaking news story is being updated and more details will be published shortly.

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Wrexham promoted for third season in a row under Ryan Reynolds and Rob McElhenney

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Wrexham promoted for third season in a row under Ryan Reynolds and Rob McElhenney

Wrexham AFC have been promoted for the third season in a row.

The North Wales-based side has gone from the National League to the Championship in just three seasons, under its Hollywood owners Ryan Reynolds and Rob McElhenney.

Wrexham were second in the table and had a run of eight games unbeaten ahead of their match against Charlton Athletic on Saturday, which they won 3-0.

Wrexham's James McClean lifts the trophy after the Sky Bet League One match at SToK Racecourse, Wrexham. Picture date: Saturday April 26, 2025.
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Wrexham’s James McClean lifts the League One trophy. Pic: PA

Wrexham's Dan Scarr celebrates with the fans on the pitch after Wrexham won promotion to the Sky Bet Championship after the Sky Bet League One match at SToK Racecourse, Wrexham. Picture date: Saturday April 26, 2025. PA Photo. See PA story SOCCER Wrexham. Photo credit should read: Martin Rickett/PA Wire...RESTRICTIONS: EDITORIAL USE ONLY No use with unauthorised audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 120 images, no video emulation. No use in betting, games or single club/league/player publications.
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Wrexham’s Dan Scarr celebrates with the fans on the pitch after Wrexham won promotion to the Championship. Pic: PA

It is the first time any club has been promoted for three consecutive seasons within the top five tiers of English football.

The third oldest association football club in the world, Wrexham AFC was bought by Reynolds and McElhenney in 2020, and has since been the subject of a Disney+ documentary, Welcome To Wrexham.

Reynolds, wearing a Wrexham sweatshirt, and McElhenney were pictured celebrating each goal, and after the game, as the fans came onto the pitch at the SToK Cae Ras (Racecourse Ground) to celebrate the victory with the players.

Wrexham co-owners Rob McElhenney (left) and Ryan Reynolds (right) and Ryan's wife Blake Lively before the Sky Bet League One match at SToK Racecourse, Wrexham. Picture date: Saturday April 26, 2025.
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Wrexham co-owners Rob McElhenney (L) and Ryan Reynolds and Ryan’s wife Blake Lively, before the match. Pic: PA

Both stars came onto the pitch after the supporters returned to the stands.

More on Ryan Reynolds

Speaking to Sky Sports, McElhenney praised those behind the scenes, referring to “so many that don’t get the credit they deserve, people who aren’t talked about”.

Reynolds said bringing success back to the club “seemed like an impossible dream” when they arrived in North Wales in 2020.

Wrexham's Sam Smith celebrates in front of the fans on the pitch after Wrexham won promotion to the Sky Bet Championship after the Sky Bet League One match at SToK Racecourse, Wrexham. Picture date: Saturday April 26, 2025. PA Photo. See PA story SOCCER Wrexham. Photo credit should read: Martin Rickett/PA Wire...RESTRICTIONS: EDITORIAL USE ONLY No use with unauthorised audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 120 images, no video emulation. No use in betting, games or single club/league/player publications.
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Wrexham’s Sam Smith celebrates in front of the fans after Wrexham won promotion to the Championship. Pic: PA

He put the three promotions down to “the coaching staff, the greatest dressing room” and an “all for one, one for all” attitude throughout the club, adding he was “speechless with their commitment and their emotion”.

As for the mouth-watering prospect of another promotion to the promised land of the Premier League, the pair agreed it was “for tomorrow”, before ending the interview with a joint mic-drop.

Veteran striker Steven Fletcher said, “as soon as I came to this club, I knew it was something special. We want to go again. We’ll reset in the summer, take a break and go again”.

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Direct action group Just Stop Oil holds final protest, claiming it has been ‘successful’

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Direct action group Just Stop Oil holds final protest, claiming it has been 'successful'

“It has been a success.”

Just Stop Oil (JSO) insists it’s been “successful” – as its members ceremoniously hang up their orange high-vis vests during a march in central London.

Since the group formed three years ago, it’s drawn attention and criticism for its colourful, controversial protests, which ranged from disrupting sporting events to throwing soup on Vincent van Gogh’s Sunflowers, and climbing on gantries over the M25. It sprayed orange paint over Stonehenge, and cost police forces tens of millions of pounds.

Those days are now behind it; to the relief of many.

Read more
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Activists target grave of Charles Darwin
77 year old JSO activist recalled to prison

As a few hundred activists marched through London on Saturday, blocking roads as they went; taxi drivers blared their horns and football fans shouted abuse from the pavement.

The PA News Agency filmed the moment a white minivan seemed to drive towards a group of protesters blocking the road.

Protesters shouted “I’m being pushed back!” to police, while the driver could be heard shouting “What about my right to get home?” to the officers gathered.

But JSO never set out to be popular. And it believes its tactics – though hated – have been successful; thanks to the new Labour government’s commitment to not issue new oil or gas exploration licences.

That’s why, it says, its ceasing direct action.

JSO hangs up its high vis jackets in central London on Saturday
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JSO hangs up its high-vis jackets in central London on Saturday

A washing line of high-vis jackets signifies JSO's disbanding
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A washing line of high-vis jackets signifies JSO’s disbanding

“This moment marks the success of the JSO campaign – our demand was to end new oil and gas licences and that is now government policy.

“As a result of which four billion barrels of oil are being kept under the North Sea. The campaign has reached a natural end.”

Dr Oscar Berglund, senior lecturer in international public and social policy, disagrees that JSO is disappearing because it’s been “successful”.

He told Sky News policing strength and public perception might have more to do with it.

“They have very low levels of popularity. About 17% of the British population are kind of broadly supportive of what Just Stop Oil do. And that’s too low to recruit.

“It’s difficult to recruit members to something that is that unpopular, and then that a lot of people for good reason I think have kind of stopped believing in that kind of disruption as a means to achieve meaningful change.”

Group triggers specific new protest laws

One thing it did change is the law.

Policing commentator Graham Wettone tells us: “Obstruction of the highway, obstruction of rail networks for example, these are specific offences now.

“It’s given the police more tactics, more methods, more offences they can consider, even stopping and searching somebody who may have something to either lock themselves on or glue themselves to something.”

A JSO activist holds a picture of an imprisoned colleague
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A JSO activist holds a picture of an imprisoned colleague

Emma Smart was held in prison for her activism with both Insulate Britain and Just Stop Oil.

“The high-vis might be going away,” she tells me, “but we aren’t.”

“These people aren’t going anywhere, we are still committed, dedicated, terrified by the failings of this government and governments around the world.”

JSO activists throw orange paint at van Gogh's sunflowers
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JSO activists throw orange paint at van Gogh’s sunflowers

Orange smoke set off by JSO protesters at Stonehenge
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Orange smoke set off by JSO protesters at Stonehenge

She hopes for a time of reflection before it returns in a new form but says the need for climate activism is stronger than ever.

She also believes that while most people dislike JSO tactics, it still raises awareness of the cause and might even push people to more moderate campaign groups.

Just Stop Oil came behind other, similarly controversial climate campaign groups like Insulate Britain and Extinction Rebellion, and as it says goodbye, its disruptive methods have been seized upon by other organisations like the Pro-Palestinian Youth Justice.

The infamous Just Stop Oil orange vests might be going away, but the individual activists, their cause and campaign tactics feel here to stay.

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