Malaria is one of the most widespread and devastating infectious diseases across the globe. This mosquito-borne parasitic disease killed approximately 619,000 people in 2021 alone, many of them children in Africa. In one of the deadliest forms of malaria, known as cerebral malaria, the patient experiences severe neurological symptoms, such as seizures and coma. Although only a small fraction of people who fall ill with malaria also experience cerebral malaria, the condition is lethal without treatment. Among hospitalized patients with the condition, death rates range between 15 and 20%. In a new paper, recently published in Science Translational Medicine, researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH, and their colleagues studied children with cerebral malaria in Malawi to better understand the underlying causes of these devastating symptoms in the hope of developing improved treatments.

Researchers know that the symptoms of cerebral malaria are caused when the brain swells within the confines of the skull, eventually impinging upon the brainstem, which causes breathing to stop. However, researchers have been unsure how malaria infection leads to brain swelling. Some researchers hypothesized that the main cause was a weakening of the blood-brain barrier, which would allow fluid to seep into the brain and cause it to swell. Others speculated that the primary driver behind the swelling was inside the blood vessels themselves. Red blood cells infected with P. falciparum, the parasite which causes malaria, can become “sticky,” adhering to the walls of blood vessels. Partial blockages inside the cerebral veins could slow the flow of blood leaving the brain, causing the blood vessels themselves to become engorged and expand the brain from within.

This illustration shows two different ways that cerebral malaria could cause brain swelling: fluid seeping into the brain (extravascular edema) or swollen blood vessels (venous congestion.)

Credit: Rose Perry-Gottschalk, NIAID Research Technologies Branch

To distinguish between these two hypotheses, NIAID researchers and their collaborators used non-invasive imaging techniques to study the flow of blood within the brains of 46 children who had been hospitalized for cerebral malaria at the Pediatric Research Ward of Queen Elizabeth Central Hospital in Blantyre, Malawi. As a comparison, they also studied 33 children with uncomplicated malaria and 26 healthy children from the local region. By using a light-based external monitoring tool (called near-infrared spectroscopy, or NIRS) the researchers were able to measure the amount of hemoglobin in the children’s brains. They reasoned that if excess fluid was the cause of brain swelling, then the hemoglobin concentration would be low, due to dilution. Alternatively, if the blood vessels were engorged with blood, then the hemoglobin concentration would be high.

The researchers found that children with cerebral malaria had significantly higher concentrations of hemoglobin inside their brains than children who had uncomplicated malaria, or healthy children—and among those with cerebral malaria, higher hemoglobin concentrations were correlated with greater brain swelling. In addition, hemoglobin concentrations fluctuated more unpredictably in children with cerebral malaria—suggesting that the normal mechanisms for controlling blood flow in the brain were disturbed. Together, these results support the hypothesis that obstruction to the outflow of blood from the brain, likely because the blood vessels themselves are clogged by red blood cells infected with P. falciparum adhering to the walls, is a main driver of brain swelling in patients with cerebral malaria.

The researchers say that these results may lead to a better understanding of why some treatments for cerebral malaria are not as effective as expected. For instance, steroids or osmotic agents are sometimes used to treat brain swelling by reducing the leakage of fluid from the blood vessels into the brain—but if the swelling is caused by the parasite-related effects within the blood vessels themselves, these treatments would not address the underlying problem. By pinpointing the exact mechanism by which cerebral malaria leads to brain damage, the researchers hope, we may improve treating it.

Reference: R L Smith et al. Increased brain microvascular hemoglobin concentrations in children with cerebral malaria. Science Translational Medicine DOI: 10.1126/scitranslmed.adh4293 (2023)
 

NIAID-Funded Study Traces Evolution of Malaria Drug Resistance in E. Africa – Emergence of Artemisinin Partial Resistance Mutations Found Across Uganda

Emerging resistance to common malaria treatments in Uganda could be connected to inconsistent use of measures to control mosquito populations, according to new findings published in the New England Journal of Medicine. The trend is worrisome, the NIAID-funded scientists state, because resistance mutations they tracked are taking root and spreading. Researchers at the University of California at San Francisco (UCSF), funded in part by NIAID’s International Centers of Excellence for Malaria Research program, led the international collaboration.

Malaria is one of the most common and serious infectious diseases. The World Health Organization (WHO) estimates that about half of the world’s population is at risk of getting malaria, which is caused primarily by Plasmodium falciparum parasites spread through the bites of female Anopheles mosquitos. In 2021, WHO estimated that about 247 million people contracted malaria in 85 countries; about 619,000 people died. About 95% of cases and deaths were in Africa.

For decades a combination of measures has resulted in effective malaria control in Africa: preventing malaria transmission with bed nets treated with insecticides; spraying insecticides indoors; treating malaria with artemisinin-based combination medicines; and preventing malaria with other drugs.

Artemisinins – originally extracted from the sweet wormwood plant, but also now available synthetically – rapidly eliminate malaria parasites from the bloodstream. They are used in combination with other longer-lasting drugs to effectively treat malaria. Beginning in 2008, however, studies in Southeast Asia identified poor results from artemisinins and eventually from artemisinin-based combination malaria treatments. Scientists soon found the primary reason – a protein (PfK13) in P. falciparum had developed mutations that made it partially resistant to artemisinins.

Since then, scientists in Africa have watched for the same mutations to emerge. The NEJM study identified five of these mutations, each of which may lead to partial resistance, that have emerged in different parts of Uganda. Their work used data from malaria cases and annual patient surveillance throughout Uganda between 2014 and 2022.

They found that two of the five key mutations appeared in far northern Uganda in 2016-17. The mutations then spread across much of northern Uganda and nearby regions, appearing in up to 54% of cases in one district. The other three key mutations emerged in western Uganda in about 2021-22, with prevalence up to 20% to 40% in different districts.

The study notes that in parts of Uganda where indoor spraying stopped between 2014 and 2018, cases of malaria quickly surged. Likewise, the emergence of any of the five key resistance mutations also surged, suggesting that the emergence was aided by malaria epidemics in populations where malaria had previously been well-controlled.

The researchers have different theories about how and why the mutations emerged. Their leading hypothesis, which they have targeted for more study, is that in populations with a low level of immunity to malaria, an epidemic increases the likelihood that resistance will emerge. “In northern Uganda,” the study states, “this scenario occurred after the withdrawal of effective malaria control, leading to high incidence of malaria in a population with relatively low antimalarial immunity.” They also suggest that fluctuating malaria transmission contributed to the emergence of drug resistance in southwestern Uganda. They emphasize the importance of maintaining malaria control interventions, with attention to malaria outbreaks, to decrease the likelihood of emergence or spread of drug resistance.

Others working on the project with UCSF include scientists from the Infectious Diseases Research Collaboration and Makerere University in Uganda; the University of Tubingen in Germany; Brown University in Rhode Island; and Dominican University of California.

Reference: 

M Conrad et al. Evolution of Partial Resistance to Artemisinins in Malaria Parasites in Uganda. New England Journal of Medicine DOI: 10.1056/NEJMoa2211803 (2023).

Mosquito-borne diseases include some of the most important human diseases worldwide, such as malaria and dengue. With global temperatures increasing because of climate change, mosquitoes and the pathogens they transmit are expanding their range. For example, the Centers for Disease Control and Prevention recently reported a number of malaria and dengue cases transmitted within the United States in Texas and Florida. Therefore, it has become more urgent to understand the interactions between climate, mosquitoes, and the pathogens mosquitoes transmit to humans.

The National Institutes of Health (NIH) Climate Change and Health Initiative is a collaborative effort across NIH Institutes and Centers to reduce the public health impact of climate change. As part of the Initiative’s Scholars Program, NIH brings climate and health scientists from outside the U.S. federal government to work with NIH staff to share knowledge and help build expertise in the scientific domains outlined in the Initiative’s Strategic Framework. 

Luis Chaves, Ph.D., is a 2023 Scholar working with NIAID. Dr. Chaves is an associate professor in the Department of Environmental and Occupational Health in the School of Public Health-Bloomington, Indiana University, and was previously an associate scientist at the Instituto Gorgas in Panama. His research focuses on understanding the impacts of environmental change on the ecology of insect vectors and the diseases they transmit. Over the last 20 years, he has combined field studies and modeling approaches, both statistical and mathematical, to address how insect vectors respond to changes in the environment and how these changes impact the transmission of diseases, such as malaria and dengue. NIAID spoke with Dr. Chaves about his work. 

Note: responses to the questions have been edited for clarity and brevity.

In what ways have you seen climate changes impact vectors and disease transmission?
There is very strong evidence that climate change has affected vector-borne diseases. This includes mosquito-borne diseases, like malaria and dengue, but also other diseases like leishmaniasis, which is transmitted by sandflies. Changes in temperature and rainfall affect the spread of disease vectors and impact their breeding behavior. For example, there is evidence of the impact of El Niño weather events on malaria transmission. Higher temperatures and more rainfall make a more suitable habitat for mosquito breeding, causing an increase in disease transmission. In other areas, El Niño weather patterns are associated with droughts, which may reduce disease transmission but cause food shortages. These weather patterns have been known and studied before, but climate change has generated more extreme conditions resulting in more extreme weather events. So, we can see that there is robust evidence that climate change is having a massive impact on human health and wellbeing.

What sparked your interest in examining how socio-economic conditions impact vector-borne disease transmission and control? 
I remember the first encounter I had with Chagas disease was visiting an uncle who lived in a rural setting. I was told not to visit a neighbor’s house because they had Chagas disease. There were lots of discussions about how his neighbor got Chagas because his home was made from mud, which is why kissing bugs, the vectors of Chagas disease, got inside. That was the first time I observed an increased prevalence of diseases in places with social exclusion and poverty. More generally, infectious diseases cannot be put out of the social and economic context where they emerge and are transmitted. If you have people with substandard housing, is that a choice, or a constraint because of the underlying socio-economic inequities? It is impossible to learn about the ecology of disease transmission without understanding that the ecology of transmission is not only ecological and environmental but also social. 

What are the advantages of using mathematical modeling to study vector-borne diseases?
Mathematical and quantitative modeling have been incredibly useful to expand the ways in which the relations shaping disease patterns can be studied This ability to understand interactions advances our capacity to engage in more relational science, where factors aren’t understood as fixed and independent forces, but as dynamic and interdependent. Relations between variables can’t be described by a fixed constant proportion, but by nonlinearities that can be easily grasped by machine learning algorithms and other data science tools.  Computers have made it easier to collect, process and analyze larger datasets. The automation of data assimilation using pipelines that integrate different data sources and algorithms can lead to robust “boosted” predictions about where and when to expect the transmission of some vector-borne diseases. Mathematical models also show how the stability of natural systems can collapse following small changes in the environment, and that has clear implications about why we need to worry as climate change continues its current course.   

What limitations do you see in the use of data science?
Data science poses ethical dilemmas, because not everyone mining freely available data is likely to do so with altruistic aims, nor is it clear how communities and individuals could benefit from the data they generated when someone profits from that or how communities, and even individuals, are protected from potential misuse.  I also think there is a need to always consider the context in which data are generated, as this approximation allows us to see what else is out there. The more nuanced our knowledge is, the more likely we can generate actionable knowledge that improves human health and wellbeing. That’s why it’s so important to include information on how data is collected (metadata) and how to use it.  The nuances don’t come from just looking at the data. They require experience, observation, and immersion in nature to create a clearer picture of vector-borne disease transmission. 

How has your work influenced vector control and prevention activities?
My research at the Costa Rican Institute for Research and Training in Nutrition and Health’s (INCIENSA) and the Costa Rican Vector Control Program was centered around developing insect vector maps and training people working in vector control about the impacts of climate change. This also involved evaluating past policies and their impact on parasitic and neglected tropical diseases. For example, comparing how different public health strategies like Mass Drug Administration versus vector control might impact malaria transmission and elimination. These activities increased the awareness about the importance of climate change, particularly among vector control inspectors, with whom I interacted closely on their work.  My research has also supported a focus on Mass Drug Administration as a major tool to eliminate malaria in Costa Rica.

What impact do you hope your research will have?
I’ll be happy if my research can serve, at least, the communities where the research is being done. As long as my research can lead to diminishing transmission of infectious pathogens or reducing the populations of vectors, then I will be happy. If that eventually leads to the elimination of those diseases, I’ll be even happier. I want to be able to provide resources for the local communities, so they can understand health problems or health threats within their local environment. For example, one of the nicest experiences I have had as a researcher was in Panama, where at least three or four studies on leishmaniasis have been done in the same community. In that community, we have seen how people come up with their own solutions, partly based on what they learn from when you did research in that location. You see how they modify their houses and look for changes in incidence of new cases. When they tell you that cases of leishmaniasis have gone down, that newborns and children aren´t getting the disease, that is very fulfilling.                     

NIAID’s VRC, S. Africa’s Afrigen Kick Off Vaccine-Sharing Efforts
Training Aimed at Making mRNA Technology Available Globally 

A team of vaccine production experts from South Africa recently finished training in Maryland as part of a global mRNA vaccine collaboration. The experts are working with scientists at NIAID’s Vaccine Research Center (VRC) to produce vaccines against a list of troubling infectious diseases.

The mRNA vaccine platform, which became commonly used during the COVID-19 pandemic, works by delivering a piece of genetic material to cells that instructs the body to make a protein fragment resembling one from a target pathogen (such as a virus). The immune system then recognizes and remembers the fragment, enabling it to mount a strong response if the body is exposed to that pathogen. The mRNA vaccine production process involves inserting the selected virus protein gene into a plasmid (a circular piece of DNA), the production of which was the topic of the visit from the South African scientists.

The seven-member team from Afrigen Biologics and Vaccines, a biotechnology company based in Cape Town, South Africa, arrived on July 21 for two weeks of collaboration and learning with VRC scientists. They focused on vaccine manufacturing at the VRC’s Vaccine Clinical Materials Program in Frederick, Maryland. Specific aspects included topics such as: inoculum growth, nutrient feeding, quality control, and other steps needed to make an mRNA vaccine. The Afrigen team also met with VRC leadership, including the recently appointed VRC Director, Dr. Ted Pierson. 

The visit represented a significant milestone for an ongoing research collaboration established in March 2022 between NIAID and Afrigen. Their objective is to share knowledge, expertise, and data to expedite mRNA vaccine production globally. As part of the collaboration, NIAID – specifically scientists at the VRC – are making plasmid DNA that will be used for Afrigen’s in vitro transcription process. Additionally, the VRC is providing technology transfer and training on plasmid DNA manufacturing, which the Afrigen group observed during the visit. In turn, Afrigen is sharing knowledge and expertise with NIAID scientists about the in vitro transcription and lipid nanoparticle formulation processes. The mutually beneficial scientific collaboration will advance each institution’s work toward establishing mRNA vaccine production capabilities to support their respective missions.

The World Health Organization, the COVAX Vaccine Manufacturing Taskforce, and the Medicines Patent Pool established a formal agreement in July 2021 to build capacity in low- and middle-income countries to make mRNA vaccines, now known as the mRNA technology transfer programme. Afrigen was chosen as a center of excellence and training, or “technology transfer hub,” as part of the mRNA technology transfer programme. The hub is designed to improve the health and security of member nations by creating sustainable, locally owned mRNA vaccine manufacturing in those nations. Because mRNA vaccines can be cheaper to produce, quickly developed in response to outbreaks, and easily modified when new variants of pathogens emerge, the ability to produce these vaccines in low- and middle-income nations will contribute significantly to global health security.

Afrigen is working to establish mRNA vaccine production technology—initially for a COVID-19 vaccine candidate—and will work with local partners to conduct research to evaluate the vaccines, along with manufacturing the vaccines at scale. The eventual goal is to be able to share this established process with manufacturers across multiple countries. 

Though the effort began with COVID-19 in mind, the scientists are mutually hoping to use the mRNA vaccine platform to develop and test vaccines against an array of infectious diseases found globally, such as HIV, tuberculosis, malaria, influenza, cancer-associated viruses and more.

Afrigen scientists spent time getting to know colleagues at the Vaccine Research Center’s Vaccine Production Program (VPP) and Vaccine Clinical Materials Program (VCMP), including during a meet-and-greet with VRC leadership and staff at the VCMP pilot plant in Frederick, Maryland.

Credit: NIAID

NIAID scientists and colleagues are one step closer to developing a safe and effective therapy against alphaviruses with the identification of SKT05, a monoclonal antibody (mAb) derived from macaques vaccinated with virus-like particles (VLPs) representing three encephalitic alphaviruses.

Spread by mosquitos, alphaviruses primarily affect people in one of two ways: causing severe neurological impairment such as encephalitis (brain swelling) or crippling muscle pain similar to arthritis. Western, eastern and Venezuelan equine encephalitis viruses (EEV) are examples of the former, while chikungunya and Ross River viruses are examples of the latter.

Building on studies from the past decade, scientists in NIAID’s Vaccine Research Center and colleagues knew that macaques produce dozens of different protective antibodies when experimentally vaccinated against the EEVs. In a new study published in Cell, the research team identified 109 mAbs in macaques immunized with the experimental western, eastern, and Venezuelan EEV VLP vaccine. All antibodies were individually tested for binding and neutralization against the three EEVs, with the best ones also assessed against arthritogenic alphaviruses not included in the vaccine. Collaborators included scientists from NIAID’s Laboratory of Viral Diseases, USAMRIID’s Virology Division, and Columbia University.

Their work identified SKT05 as the most broadly reactive antibody – remarkably, it also provided protection against both types of alphaviruses, those that cause encephalitis and those that cause arthritic-like disease. High-resolution structural studies further revealed that the way SKT05 binds to alphaviruses could make it resistant to surface changes that can occur in viruses – which means the mAb is likely to have lasting effectiveness.

Further studies are planned to investigate potential clinical development of SKT05. They aim to better define how SKT05 interacts with viruses and whether it can confer protective benefits against additional alphaviruses.

References:
M Sutton et al. Vaccine elicitation and structural basis for antibody protection against alphaviruses. Cell DOI: https://doi.org/10.1016/j.cell.2023.05.019 (2023).

EE Coates, et al. Safety and immunogenicity of a trivalent virus-like particle vaccine against western, eastern, and Venezuelan equine encephalitis viruses: a phase 1, open-label, dose-escalation, randomised clinical trial. Lancet Infectious Diseases (2022).

SY Ko, et al. A virus-like particle vaccine prevents equine encephalitis virus infection in nonhuman primates. Science Translational Medicine (2019).