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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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World

Israel attacking Lebanon every four hours as ceasefire frays

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Israel attacking Lebanon every four hours as ceasefire frays

It’s been more than a year since a ceasefire was agreed in Lebanon, but data shows that the truce between Israel and Hezbollah is more fragile than ever.

The independent conflict monitoring organisation ACLED has recorded 1,846 Israeli attacks on Lebanon since the ceasefire began.

On average, only two days of each month have not seen an Israeli attack.

The bombings have grown more frequent in recent weeks, with an average of six per day so far in December, or one every four hours – the fastest pace of attacks since March.


The Lebanese children bombed by Israel

Israel says it is targeting Hezbollah military infrastructure

The ceasefire deal requires both sides to withdraw from southern Lebanon, the area south of the Litani river.

The UN mission in southern Lebanon, UNIFIL, says the agreement has been violated more than 10,000 times – once every 53 minutes.

That includes the attacks monitored by ACLED, as well as more than 2,500 IDF ground activities and over 7,800 violations of Lebanese airspace.

It also includes the discovery, by UNIFIL, of more than 360 weapon and ammunition caches south of the Litani river.

Israel says that these caches are evidence that Hezbollah is seeking to rebuild its military infrastructure in southern Lebanon, an allegation denied by both Hezbollah and UNIFIL.

“None of these weapon caches were guarded,” says UNIFIL deputy spokesperson Kandice Ardiel. “They had no obvious signs of recent use and were presumably abandoned. Many were even destroyed already, or half-destroyed.”

An IDF spokesperson said that Hezbollah’s attempts to rebuild its military infrastructure in southern Lebanon “are not open to interpretation”.

“In the absence of sufficient enforcement by UNIFIL, and out of commitment to the security of the Israeli civilians, the IDF continues to operate in a focused manner against Hezbollah’s restoration attempts,” the spokesperson said.

At least 127 civilians have been killed by Israeli attacks since the ceasefire began, according to the UN.

Israel argues that the ceasefire agreement requires Hezbollah to disarm in all parts of Lebanon, not just the south. Hezbollah disputes this, and says it will not consider full disarmament until Israel withdraws entirely from Lebanese territory.

Israel has established five military bases inside Lebanon

This withdrawal was supposed to take place by 27 January 2025, a deadline that was later extended to 18 February.

But instead of withdrawing from its Lebanese bases, Israel began cementing its presence.

Sky News has confirmed, based on satellite imagery, that Israel started construction on a new base, shown below, between 8 and 18 February – within days of the withdrawal deadline.

Israeli base on Tzivoni ridge, Lebanon, 18 November 2025. Pic: Planet Labs PBC
Image:
Israeli base on Tzivoni ridge, Lebanon, 18 November 2025. Pic: Planet Labs PBC

Israel retains control of four other bases on Lebanese territory, scattered along hilltops near the border.

“We need to remain at those points at the moment to defend Israeli citizens, to make sure this process is complete and eventually hand it over to the Lebanese armed forces,” IDF spokesman Nadav Shoshani said in February.

Lebanon has raised complaints with the UN about these bases, as well as Israel’s recent extension of its border wall. The UN says that two sections of the wall cross into Lebanese territory, putting around one acre on the Israeli side.

Israeli border wall under construction near Yaroun, 18 November 2025. Pic: Planet Labs PBC
Image:
Israeli border wall under construction near Yaroun, 18 November 2025. Pic: Planet Labs PBC

Sky News asked the IDF whether it accepted the UN’s findings, but did not receive a response to this question.

In the image below, part of the newly constructed wall can be seen passing between border posts, highlighted in green, into Lebanese territory.

A newly-constructed portion of Israel's border wall is seen crossing into Lebanon, with border posts highlighted. Pic: AP
Image:
A newly-constructed portion of Israel’s border wall is seen crossing into Lebanon, with border posts highlighted. Pic: AP

Construction of the wall resumed over summer, having been halted since hostilities erupted in October 2023. Based on satellite imagery, Sky News estimates that a total of 12km of wall have been erected in recent months.

The continued presence of Israeli forces has hampered reconstruction efforts. More than 64,000 Lebanese people remain displaced from their homes.

Sky News visited one of the towns that sits in view of the Israeli base on Mount Balat. The town, Aita al Chaab, has been almost entirely destroyed.

Wreckage in the border town of Aita al Chaab
Image:
Wreckage in the border town of Aita al Chaab

Satellite imagery, taken on 24 November, shows the town in ruins. Out of 326 buildings in the town centre, 293 (91%) have been destroyed.

Since the ceasefire began, the destruction has continued and has spread to the Aita al Chaab’s outskirts.

“Anyone who comes to rebuild is attacked [by Israel],” one resident told Sky News.


The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.

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US

New plaques in Trump’s White House attack Joe Biden, Barack Obama and George W Bush

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New plaques in Trump's White House attack Joe Biden, Barack Obama and George W Bush

Donald Trump’s administration has installed new plaques beneath portraits of former presidents attacking his predecessors in the US president’s typical fashion.

Among the plaques, apparently written by Mr Trump himself, is one for Joe Biden reading: “Sleepy Joe Biden was, by far, the worst president in American history.”

The “Presidential Walk of Fame” at the White House features a picture or painting of every former US president – except Mr Biden, who has been replaced by a photo of an autopen.

Biden's refers to 'Sleepy Joe'. Pic: Reuters
Image:
Biden’s refers to ‘Sleepy Joe’. Pic: Reuters

Mr Trump has repeatedly claimed Mr Biden was not mentally capable by the end of his term as president and his staff made decisions on his behalf, using an autopen to sign them off without his knowledge.

The device reproduces a person’s signature, allowing them to repeatedly sign documents without having to do so by hand each time.

The damning decoration goes on to falsely accuse Mr Biden of winning the “most corrupt election ever” and claims he made “unprecedented use of the autopen.”

Obama's says he presided over a 'stagnant economy'. Pic: Reuters
Image:
Obama’s says he presided over a ‘stagnant economy’. Pic: Reuters

Another plaque refers to “Barack Hussein Obama” as “one of the most divisive political figures in American history.”

The plaque underneath Bill Clinton’s photo reads: “In 2016, president Clinton’s wife, Hillary Clinton, lost the presidency to President Donald J Trump!”

Even George W Bush, a fellow Republican – though not a Trump supporter – is given a badge of rebuke, with his plaque saying the former president “started wars in Afghanistan and Iraq, both of which should not have happened.”

Bush's plaque attacks the wars in Iraq and Afghanistan. Pic: Reuters
Image:
Bush’s plaque attacks the wars in Iraq and Afghanistan. Pic: Reuters

The “Presidential Walk of Fame” is a recent addition to Mr Trump’s White House and displays the portraits along corridors between the Oval Office and the South Lawn.

The White House press secretary, Karoline Leavitt, said the plaques were an “eloquent” description of each president’s legacy.

“As a student of history, many were written directly by the president himself,” she said.

It is the latest change to Mr Trump’s White House, which has seen the increased use of gold-coloured accents and gilded fixtures that mimic the decorations in Trump Tower in New York and his Mar-a-Lago estate in Florida.

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Politics

US Fed pulls guidance blocking its banks from engaging with crypto

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US Fed pulls guidance blocking its banks from engaging with crypto

The US Federal Reserve has withdrawn a 2023 guidance that limited how Fed-supervised banks, including uninsured ones, engaged with crypto, as US regulators continue to pivot positively toward digital assets. 

The 2023 guidance required uninsured banks to follow the same rules as federally insured institutions, based on the principle that similar activities pose similar risks and should be subject to identical regulation.

This prevented uninsured banks from engaging in activities that weren’t permitted for national banks, like crypto services, which automatically disqualified Fed membership because the institution’s primary activities weren’t allowed.

Fed says financial system has evolved since 2023

The Fed said a key reason for withdrawing the guidance was that it was outdated and “the financial system and the Board’s understanding of innovative products and services have evolved.”

“As a result, the 2023 policy statement is no longer appropriate and has been withdrawn,” it said. 

Caitlin Long, the CEO of the crypto‑focused Custodia Bank, applauded the move in an X post on Wednesday, explaining the 2023 guidance was why her institution’s application for a master account was previously denied. 

Source: Cailtin Long 

A master account with the Fed enables a financial institution to hold balances directly with the US central bank and access its core payment systems, allowing for payment settlement in central bank money rather than relying on another bank as an intermediary.

Related: Trump’s views on interest rates will hold ‘no weight’ at Fed: Hassett

“The Fed broke the law by citing this very guidance in the Custodia denial, even tho the guidance hadn’t become official yet, that didn’t happen until Feb 2023,” Long said. 

“But most of that team is now gone or out of power at the Fed. Nature is healing. Thank you VCS Bowman & Gov Waller!” she added. 

New guidance to boost bank innovation

The move on Wednesday came as the Federal Reserve issued new guidance to establish a formal pathway for both insured and uninsured Federal Reserve-supervised state member banks to pursue “innovative activities,” such as cryptocurrencies, provided risk-management expectations are met, according to a statement on Wednesday by the Fed.

Source: Federal Reserve 

Fed vice chair for Supervision Michelle Bowman said that by “creating a pathway for responsible, innovative products and services, the Board is helping ensure that the banking sector remains safe and sound while also modern, efficient, and effective.”

Fed decision wasn’t unanimous

Fed Governor Michael Barr dissented to the decision, arguing that the principle of equal treatment among banks helps maintain a level playing field and prevents regulatory arbitrage.

“This principle continues to hold true today. Therefore, I cannot agree to rescind the current policy statement and adopt a new one that would, in effect, encourage regulatory arbitrage, undermine a level playing field, and promote incentives misaligned with maintaining financial stability. I dissent,” he said.

Barr has been accused of being linked to Operation Chokepoint 2.0, a federal effort to debank crypto companies. However, he was also previously an adviser at Ripple and has pushed for responsible stablecoin regulation.

Magazine: Unstablecoins: Depegging, bank runs and other risks loom