HIV antibodies revived as microbicide

Julian Meldrum
Estimated reading time 2 minutes
This article is more than 22 years old.

A study reported online by Nature Medicine claims the first evidence of protection for female macaques against infection with an SHIV, from topically applied anti-HIV antibodies.

A research group led by Dr John Moore at Cornell University found that applying 5mg of a broadly-neutralising monoclonal antibody against HIV (with the codename b12) two hours before monkeys were vaginally exposed to an SHIV virus with an HIV outer coat seemed to protect most of the monkeys from infection. Among monkeys treated with the antibody, 3 out of 12 became infected. In a control group, 12 out of 13 were infected (Veazey).

A biotech company called Epicyte in San Diego, California, is reported to be developing a system for producing this antibody in genetically engineered plants, which would allow it to be made cheaply in large quantities.

Glossary

microbicide

A product (such as a gel or cream) that is being tested in HIV prevention research. It could be applied topically to genital surfaces to prevent or reduce the transmission of HIV during sexual intercourse. Microbicides might also take other forms, including films, suppositories, and slow-releasing sponges or vaginal rings.

simian human immunodeficiency virus (SHIV)

An artificial form of HIV adapted to cause infection and disease in monkeys. It combines elements of a virus that affects monkeys (SIV) with the envelope protein of HIV itself. Researchers study SHIV as a way to learn more about HIV.

control group

A group of participants in a trial who receive standard treatment, or no treatment at all, rather than the experimental treatment which is being tested. Also known as a control arm.

formulation

The physical form in which a drug is manufactured or administered. Examples of formulations include tablets, capsules, powders, and oral and injectable solutions. A drug may be available in multiple formulations.

inflammation

The general term for the body’s response to injury, including injury by an infection. The acute phase (with fever, swollen glands, sore throat, headaches, etc.) is a sign that the immune system has been triggered by a signal announcing the infection. But chronic (or persisting) inflammation, even at low grade, is problematic, as it is associated in the long term to many conditions such as heart disease or cancer. The best treatment of HIV-inflammation is antiretroviral therapy.

While previous studies have found that injected antibodies are able to provide significant protection against exposure to SHIV across mucosal surfaces, there was no protection against infection when antibodies were applied to the surface or pre-incubated with the virus (Lewis).

A variety of microbicide candidates have been shown to protect monkeys against viral challenges. However, their effectiveness in humans remains to be proven. A substance that is to act as either a chemical or physical barrier against infection must be present in the right amounts, at the right place at the right time. To protect against HIV transmission during sexual contact, this means that the way a product is formulated and applied is likely to be just as important as the nature of the 'active ingredients'.

A further issue with all microbicides is that they must be safe for long-term use, without causing inflammation or other damage to tissues that could make people more vulnerable to infection with HIV and other diseases.

There is further discussion of microbicide development on aidsmap here. Links to external sources of information are listed here.

References

Lewis MG et al. Neutralizing antibodies applied to the mucosal surface, or preincubated with challenge virus ex vivo fail to protect macaques against SHIV challenge. 9th Conference on Retroviruses and Opportunistic Infections, Seattle, abstract 77, 2002.

Veazey RS et al. Prevention of virus transmission to macaque monkeys by a vaginally applied monoclonal antibody to HIV-1 gp120. Nature Medicine, published online, doi:10.1038/nm833, 2003.

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