Page 105 - Annual report 2021-22

Annual Report 2021-22 |

Sheetal Gandotra

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Sheetal Gandotra’s lab studies host pathogen interactions in tuberculosis, particularly from the
standpoint of lipid metabolism.

Lipid remodelling is an important facet of mycobacterial physiology. Sheetal Gandotra’s group is
working on a family of enzymes called patatins. This eight-membered family in Mycobacterium
tuberculosis comprises diverse regulatory features. Her lab is utilizing lipid biochemistry and genetic
approaches to understand the function of these enzymes in lipid remodelling and pathogenesis.

One of the central questions in her lab is the role(s) played by host lipid accumulation during infection.
Following up on their previous work on the development of necrosis associated foamy macrophages
in tuberculosis, her lab aimed to address the role of triglyceride synthesis on the outcome of infection
using a susceptible mouse model. C3HeB/FeJ mice were used for these studies. These mice develop
necrotic lung lesions (granulomas) upon infection with M. tuberculosis Erdman strain. In this study,
mice were treated with a pharmacological inhibitor of the enzyme diacylglycerol-O-acyltransferase 1
after the establishment of infection. The inhibitor, T863, was administered via the intravenous route.
Treatment indeed led to decline in neutral lipid accumulation in the granuloma. 50% of T863 treated
mice exhibited improved control of infection and a decline in neutrophil infiltration and inflammatory
response. Triglycerides can be potential donors of fatty acids that are precursors for lipid mediators
of inflammation. Counterintuitively, several lipid mediators of inflammation were increased in the
lungs of T863 treated animals. However, levels of pro-resolution eicosanoids were increased in the
animals that reduced bacterial burden upon T863 treatment. This bimodal response to treatment
highlighted the association between neutral lipid levels, inflammation, and control of bacterial
infection and provided the first proof of concept that altering lipid accumulation pathways of the host
may provide a means for host targeting therapies against tuberculosis.

Taking this field forward, her lab is now addressing the role of lipid droplet associated proteins in
regulating inflammatory response to infection. Lipid droplets are storage organelles for triglycerides
and cholesterol esters. Her lab had previously identified that infection leads to alteration in the
proteome of macrophage lipid droplets. Her lab is working on how these proteins modify lipid droplets
and the role of these modifications in infection outcome.

Host response to infection can also be used to develop into differential diagnostic tools. With this in
mind, her lab is working towards identifying blood based signatures for differential diagnosis of
extrapulmonary tuberculosis. In partnership with Dr Vivek Rao at IGIB, Dr Joy Sarojini Michael at CMC
Vellore and Dr Rajesh Gokhale at National Institute of Immunology, peripheral blood was collected for
72 TB and 58 non-TB cases for pulmonary and extrapulmonary involvement. This includes 15 CNS TB
and 14 CNS-Non-TB, 15 LN TB and 12 LN non-TB samples. Initial screening for previously described
signatures of pulmonary TB did not hold true for differential diagnosis at extrapulmonary sites,
particularly for CNS and LN TB. RNA sequencing is now being done for de novo identification of TB
signatures that will be relevant for differential diagnosis of tuberculosis at extra-pulmonary sites.

Her lab also started work on SARS CoV2 pseudotype virus neutralization assays.