![]() In vitro and in vivo studies showed that memory T cells are more susceptible to MV infection than naive T cells, due to higher expression of CD150 17, 18. Ensuing lymphocyte depletion and follicular exhaustion in lymphoid tissues have been described during prodromal measles in both humans and NHPs 16, 17. In experimentally infected non-human primates (NHPs), MV initially targets myeloid cells in the respiratory tract, which act as Trojan horses by transmitting MV to CD150 + lymphocytes in lymphoid tissues, leading to viraemia and systemic virus dissemination 12, 13, 14, 15. MV infects cells after binding to cellular receptors CD150 or nectin-4, expressed on subsets of immune cells or the adherens junctions of epithelial cells, respectively 9, 10, 11. A better understanding of the pathogenesis of measles and measles-associated immune suppression will help convey the message that vaccination is vital. ![]() To reach the goals set out in the Global Vaccine Action Plan, which include elimination of measles by 2020 in five out of six regions of the World Health Organisation (WHO) 8, improvement of public health information, education and communication is crucial. The increase of vaccine hesitancy is a major concern, since it appears to be linked to the lack of understanding of the impact of measles as serious childhood disease. In Europe, a four-fold increase in the number of measles cases was reported in 2017, largely due to declining vaccination coverage 7. Despite the availability of safe and effective live-attenuated vaccines, measles and its sequelae still cause more than 85,000 deaths globally 6. Paradoxically, measles also induces strong cellular and humoral immune responses that mediate lifelong protection 5. The disease is associated with a transient immune suppression and increased risk of childhood morbidity and mortality for a period of more than 2 years 2, 3, 4. Measles is characterised by fever, cough and a maculopapular skin rash 1. Measles virus (MV) is a highly infectious virus that is transmitted through aerosols and droplets and causes measles. This study emphasises the importance of maintaining high measles vaccination coverage. These data support our immune amnesia hypothesis and offer an explanation for the previously observed long-term effects of measles on host resistance. In paired PBMC collected before and after measles we found reduced frequencies of circulating memory B cells and increased frequencies of regulatory T cells and transitional B cells after measles. In peripheral blood mononuclear cells (PBMC) of prodromal measles patients, we detected MV-infected memory CD4 + and CD8 + T cells and naive and memory B cells at similar levels as those observed in NHPs. A measles outbreak in the Dutch Orthodox Protestant community provided a unique opportunity to study the pathogenesis of measles immune suppression in unvaccinated children. In experimentally infected non-human primates (NHPs) measles virus (MV) infects and depletes pre-existing memory lymphocytes, causing immune amnesia. Measles causes a transient immune suppression, leading to increased susceptibility to opportunistic infections.
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