June 25, 2015 | Patti Wieser
CTRI KL2 awardee Gabriel Wagner, MD, at the UC San Diego Center for AIDS Research
HIV dual infection, which occurs when an infected individual has been re-infected by the virus a second time, has been associated with certain markers of disease progression. Preliminary findings indicate it may also be linked to diminishing neurocognitive function.
Gabriel Wagner, MD, an assistant adjunct professor in the Division of Infectious Diseases at UC San Diego Department of Medicine, received a KL2 Junior Faculty Career Development Award in 2014 from UC San Diego Clinical and Translational Research Institute (CTRI) to investigate this possible link.
"My theory is that becoming infected by a second virus somehow stacks the odds in favor of HIV better penetrating the central nervous system – the brain and spinal cord – and therefore affecting it more readily than a single virus," Wagner said. "Through our research, we have found an association between dual infection and neurocognitive impairment."
Wagner, a clinician-researcher who treats HIV patients at UC San Diego's Owen Clinic and conducts research at the Center for AIDS Research (CFAR), presented findings from his KL2 project during poster sessions at the 2014 and 2015 Conference on Retroviruses and Opportunistic Infections, and is drafting a manuscript for submission to the Journal of NeuroVirology. In January, he co-authored a paper about related research, "HIV-1 neutralizing antibody response and viral genetic diversity characterized with next generation sequencing," in Virology.
Researchers had already established neurological complications from HIV infection. "The infection enters the central nervous system (CNS) early and is connected with HIV-associated neurocognitive impairment," Wagner said. Impairment ranges from having no clinically apparent symptoms to dementia so debilitating that patients have difficulty functioning.
Through the KL2 award, Wagner began investigating if dual infection hastened the neurological impact. He used next generation sequencing to identify cases of HIV dual infection in a group of chronically infected participants who are on antiretroviral therapy (ART). "We used the large, well-characterized CNS HIV Anti-Retroviral Therapy Effects Research (CHARTER) cohort to identify dual infection in blood, and study its associations with the presence of HIV associated neurocognitive disorders," he said. Next generation sequencing performs massively parallel sequencing, during which millions of DNA fragments from a single sample are sequenced in unison. HIV dual infection, also referred to as HIV superinfection, is not readily detectable in a clinical setting and typically requires research tools to confirm its detection. Markers such as increased viral loads are indicators of dual infection, but since dual infection responds well to modern ART, it is not often diagnosed.
Wagner said individuals were tested longitudinally, with blood plasma samples collected at time points. "HIV inserts into the human DNA, so we were looking for archived virus to see if two different viruses were archived in these individuals' DNA," he said.
HIV DNA was extracted from participants' blood cells, the viral DNA was amplified, and from this researchers performed sequencing of discreet pieces. "Next generation sequencing gives us thousands upon thousands of sequences per cell so we are able to see all the different viral lineages and variances that exist within an individual. We can see whether there are viral sequences that are widely different within a single sample by doing phylogenetic analysis," he said. If a virus is so different from another within a sample, it is identified as a separate virus. Phylogenetic refers to the genetic evolution of the viruses.
"When we looked at the blood samples of 38 individuals, we found that nine had dual infection. Of the 38, 20 had neurocognitive impairment," Wagner said. "Of those who had neurocognitive impairment, a greater proportion had dual infection. In fact, after accounting for other variables, the odds of individuals with dual infection also having neurocognitive impairment was 36 times greater than for singly infected individuals." Neurocognitive testing was conducted at the UC San Diego HIV Neurobehavioral Research Center, which performs highly sensitive neuropsychological testing to detect all levels of impairment, even the most subtle.
Wagner said he is excited about the early results from his study. "These are still very early observations, but potentially may teach us certain strategies that the virus uses to better penetrate and adapt to the central nervous system," he said. "Hopefully this can be used in the future as targets to prevent the neurological consequences of HIV infection."
The next research step is to see if there is evidence of two viruses in the spinal fluid from the same CHARTER individuals. Eventually, mechanistic studies to see how the phenomenon is occurring – how the infection damages the central nervous system – will be done.
Wagner stressed the importance of studying neurocognitive effects because they are prevalent in HIV dual infection. "As a researcher at CFAR, I'm able to use specimens that have been collected from these individuals to learn as much as we can about how to deal with the complications of HIV infection and ultimately curb the epidemic."
Wagner received a bachelor's degree in biology, biochemistry, and French from Case Western Reserve University in Cleveland, Ohio, and an MD from the University of Toledo College of Medicine in Toledo, Ohio, before beginning an infectious diseases fellowship at UC San Diego in 2009. He joined the UC San Diego faculty in 2014. His present work focuses on HIV superinfection and he works closely with research mentor Davey Smith, MD, director of CFAR Translational Virology Core.
Wagner said he was grateful to CTRI for the KL2 support, which has helped him carve out dedicated time for this research. "The KL2 has been instrumental in me being able to carry forward this project, providing me with protected research time and salary support," he said. "It has been invaluable."