Research with monkeys

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Monkeys are used only when it is not possible to use other species. They are employed primarily in research into the disorders, structure and function of the brain, and in research to produce a vaccine for HIV/AIDS. Monkeys are needed for this work because they are closely related to humans.

In studies of the safety of drug candidates before being used in humans documentation according to GLP (Good Laboratory Practice) is required. Monkeys are used only in cases where the drug authorities require that these tests are performed on monkeys.

The Astrid Fagræus Laboratory (AFL)

The Astrid Fagraeus Laboratory (AFL), where experiments with monkeys are performed, is now the only facility in Sweden who is authorized to conduct animal testing under GLP. AFL is also the first in Sweden to become accredited by AAALAC International Organization for its high quality of animal welfare.

Read more about housing at Astrid Fagraeus laboratory

HIV vaccine research

The HIV/AIDS epidemic continues to spread around the world, though it is concentrated in Africa and Asia. The WHO estimates that a total of 33 million people were carrying HIV at the end of 2008, with a further 2.7 million infected during the year. Without treatment, they are all at risk of dying within ten years. Almost 17 million children aged 17 and under have lost one or both of their parents to HIV/AIDS.

Around 90% of HIV carriers are in developing countries. It is primarily people of reproductive age who are affected, though children also account for a high percentage of those infected. Life expectancy in the hardest-hit countries in southern Africa has fallen from 62 to 47 since 1990 on account of AIDS. This epidemic is the world's largest yet, more deadly than either the Black Death or Spanish Flu. The disease is a major drain on countries' productivity and an entire continent is on its knees.

No cure in sight

The current treatments do not cure the HIV infection but can, in a best case scenario, slow its progression and prevent AIDS from developing. These medicines are expensive and can cause serious side-effects, are difficult to administer and require regular healthcare visits. Furthermore, they often become ineffective over time as the virus changes and develops resistance to them. They are not therefore a realistic alternative for the vast majority of HIV carriers living in developing countries.

In spite of major information and publicity campaigns, only a few developing countries have been able to demonstrate a trend towards a reduction in the spread of HIV. An effective and readily available vaccine could be a solution as a complement to preventive strategies.

Only monkeys and humans susceptible to HIV

There are two types of HIV that can lead to AIDS: HIV-1 and HIV-2. HIV-1 has spread virtually worldwide, while HIV-2 is to be found predominantly in west Africa. The HIV-like simian immunodeficiency virus (SIV) occurs in African monkeys without causing disease. However, SIV can induce an immunodeficiency disease similar to AIDS in experimentally infected Asian macaques such as rhesus and crab-eating macaques.

Animal research is necessary in the development of a vaccine for HIV/AIDS. It is primarily macaques that are used in studies involving experimental infection with HIV or SIV. Smaller experimental animals such as mice, guinea pigs and rabbits are not susceptible to these infections. Chimpanzees and gibbons have also been used in some cases as they are the animals that are most susceptible to HIV-1 infection, but ethical considerations have meant that the use of these animals for HIV vaccine trials is very limited. Asian monkeys are not susceptible to HIV-1. This being the case, the most regularly used animal models for AIDS research involve the experimental infection of macaques with SIV or HIV-2, or with a hybrid virus of SIV and HIV-1 known as SHIV.

What happens in a vaccine study?

It is possible to investigate the protective effect of HIV or SIV vaccines using a relatively small number of monkeys for each study. The animals are divided into different groups: some will be given the vaccines to be tested (candidate vaccines), while others will make up an unvaccinated control group. The animals will typically be vaccinated three to four times at intervals of a couple of months. After the final vaccination the monkeys are given an infectious virus to determine whether the vaccine offers protection against HIV/SIV infection. Researchers will often compare two or more candidate vaccines in the same trial, with six monkeys in each vaccine group and in the control group.

We do not yet fully understand how the body's immune system reacts during infection with HIV or SIV. It is therefore important to take blood samples during the trial to monitor the development and function of some cell types. These results are then compared with how the vaccination protects against infection. Only small volumes of blood are taken from the monkeys during the trial.

In order to get an idea of the level of protection afforded against the virus (HIV or SIV) in the vaccinated monkeys, researchers measure the concentration of the virus in the blood during the first three to six months. Investigating the level of protection afforded against the full-blown disease (AIDS) would require the animals to be monitored for a longer period. But trials are never allowed to proceed to the point where the disease has developed fully. As soon as the monkeys show signs of the disease they are removed from the study and euthanised in a pain-free manner with an overdose of anaesthetic. At around a year, the follow-up period is considerably shorter in trials with monkeys than with humans (three to five years). This means that using monkeys ensures that the best strategies for vaccination against HIV benefit humans more quickly.

There are also other advantages to using monkeys when carrying out the initial studies. Studies with humans have to include far more people as it is not possible to control who will become infected. Furthermore, anyone contracting AIDS during a vaccine study will develop the full-blown disease or will have to undergo treatment for the rest of their life if they are to avoid dying of it.

Achieved research results from SMI/KI

Researchers at the Swedish Institute for Communicable Disease Control (SMI) and Karolinska Institutet (KI) have been working on HIV/SIV vaccine trials using macaques since 1988. Together with research groups in Europe and the US they have investigated different types of vaccine and found that live attenuated virus vaccines offer the best protection. However, it is unlikely that this type of HIV vaccine will ever be used for humans because of the risk of it causing the disease. Research is instead focusing on other types of vaccine and combinations of different types of vaccine produced using new techniques such as viral DNA plus live recombinant vaccines.

Researchers at SMI/KI were among the first in the world to use studies with monkeys to show that an HIV/SIV vaccine can offer protection against AIDS even if it does not confer full protection against the virus itself. This finding is important for future investigations into the protective effect of HIV vaccines in humans.

Animal trials led to vaccine studies with humans

For many years researchers at SMI/KI have been developing and testing HIV vaccines with funding from primarily the Swedish International Development Cooperation Agency (Sida) and the EU. This development work has included vaccine trials with monkeys and preparations for clinical trials of HIV vaccines in Tanzania.

An HIV vaccine trial on monkeys at the AFL used a combination of two vaccines  HIV DNA and HIV MVA. Promising results from the trial led to this vaccine combination being tested on humans in a study in Sweden and then in Tanzania. These studies showed that nearly all of the vaccinated participants developed a strong immune response to HIV. New, extended vaccine trials began in Sweden and Tanzania in 2010.

Malaria vaccine research

In November 2015, 24 rhesus macaques arrived at the Astrid Fagraeus Laboratory (AFL) and have acclimated well at our facilities. They were flown here from the US via Frankfurt, Germany and are now included in a preclinical study testing of a new malaria vaccine. The ethical permit for the malaria vaccine research covers the use of 120 animals, but no more than 24 are planned for the study.

According to the World Health Organization, there were around 200 million cases of malaria, primarily in Africa, in 2013 and around 600,000 deaths, half of them children under the age of five. There is therefore a desperate need for a vaccine. A protective vaccine would save the lives of hundreds of thousands of children every year.

Malaria is caused by parasites which are far more complex than the viruses and bacteria that we have vaccines for today. The malaria parasite has multiple stages in their life cycle where in each stage they express different antigens (proteins that are able create an immune response). This makes it very challenging for the development of an effective vaccine. Another challenge is that different types of vaccine responses (antibodies or cytotoxic T cell responses) are required for protection depending on where the parasite is in its life cycle. An intimate understanding of the interaction between the host immune system and the vaccine and how sustained and protective immunity can be generated is therefore critical. In addition, a malaria vaccine has to be affordable for large-scale production, allow for practical storage conditions and administration as well as having an exceptional safety profile to be given to children.

The malaria vaccine that is tested at the AFL is the result of decades of research and contributions from multiple research groups in different countries. Characterization and refinements of the vaccine using extensive laboratory analyses including cell cultures and studies in mice have been done. Testing the vaccine in rhesus macaques is the next critical step and a prerequisite to proceed with testing in humans. Rhesus macaques are an invaluable model to predict how a vaccine would perform in humans as their immune system and genetic diversity are very similar to humans. The malaria vaccine is based on a unique conserved antigen that has been selected for its low variability. Earlier studies have shown that vaccination using this antigen prevents mosquitos to further reproduce and transmit the parasite. The parasite can therefore potentially be eradicated from an area. However, a successful vaccine has to induce significant levels of malaria-specific immune responses. This means that the vaccine antigen has to be appropriately packaged so that it can effectively stimulate the immune system inducing the desired protective response. A new vaccine-packaging platform that has already been tested for other diseases in humans with promising results will therefore be the basis for the malaria vaccine in our study.

The strength of the malaria vaccine response required to inhibit parasite replication in mosquitos and further transmission to people has been determined. This means that we can benchmark our results to known required levels. Immunological assays are available to measure the vaccine responses as well as to functionally prove that the response is in fact able to inhibit parasite reproduction. There is therefore no reason to infect the animals in our study with live malaria parasites. The magnitude, durability and protective effect found in our study will determine whether the vaccine will continue to clinical testing in humans. We are hopeful that this malaria vaccine has prospects of being the first to provide protection against malaria.

Study Procedure

The animals will receive the malaria vaccine three times and the immune responses will be carefully monitored by collecting regular blood samples (approx. 1 - 2 per month) for at least nine months. No other tissues are planned to be collected. As mentioned previously, the animals will not be challenged with any malaria parasites since there are laboratory analyses available using the blood samples that can predict the capacity of the immune responses to block infection. The animals will be sedated during the procedures. Vaccination and a blood draw take about 10 minutes.

The animals are housed in groups of two or three in an enriched environment that gives them the ability to express their natural behaviours. Significant focus is directed towards creating harmonic and social milieus for the animals. The animals are grouped with individuals they grew up with and get along with. They all have established relationships with their personal care-taker who trains and offers them daily intellectual and physical exercises.

Find out more about the living and social environments for macaques at AFL.

Research into the brain's function

Positron emission tomography (PET) has enabled major progress in biomedical research, particularly in research into the structure and function of the brain. It is also important for detecting tumours and developing new medications. PET involves labelling organic molecules with a radioactive isotope and then injecting these tracers into one of the patient's blood vessels. The positron camera is then used to monitor how the molecules are absorbed into the brain. Before a tracer can be used on patients, it must first be tested on research animals, normally monkeys as they are closest to human beings in terms of brain structure and function.

Research with monkeys teaches us more about the human brain

The PET research carried out on the AFL monkeys is intended to develop new tracers so that PET can be used to investigate signalling systems in the living human brain. These systems are vital for diagnosing and treating neurological and neuropsychiatric disorders such as Alzheimer's, Parkinson's, schizophrenia, depression and ADHD. The close correlation between the results from monkey experiments and subsequent studies with humans has meant that researchers at Karolinska Institutet (KI) have been able to confirm the value of the monkey studies for developing suitable tracers. This work has included producing markers to investigate subtypes of dopamine, serotonin, noradrenaline and GABA receptors. Researchers at KI have developed a tracer that has made it possible for the first time to investigate the serotonin transporter (SERT). They have shown in studies using monkeys that the marker binds selectively to SERT, paving the way for studies with humans. This method will be used in investigations into depressive disorders and into the mode of action and clinical guidelines for antidepressants.

What happens in a PET trial with monkeys?

The monkeys used for PET trials are totally healthy and live together in compatible groups of four to ten. In this type of experiment a monkey is used roughly once a month, though often less frequently. It is anaesthetised in its cage at the AFL and remains anaesthetised throughout the experiment. Several hours later once it has fully regained consciousness it is returned to its cage. By way of preparation, a cannula is inserted into one of the monkey's legs at the AFL so that researchers can administer the tracer safely and take blood samples. Blood samples are taken during the experiment to enable analysis of the tracer in the blood plasma.

Each day will generally involve two experiments. The first sees the tracer being injected so that researchers can study its distribution in the brain. The second PET experiment is identical to the first except that a known reference substance is injected 10-20 minutes before the tracer. The reference substance binds to the receptor in question, thus preventing the tracer from doing so. These experiments demonstrate the degree to which the tracer binds specifically to the receptor, and are extremely important for subsequent studies on humans.

Animal experiment