Frail medical infrastructure in countries stricken with malnutrition has limited the collection of community-wide dietary data. Whilst malnutrition has been linked with economic fragility, the paucity of studies linking forms of malnutrition in zinc, copper and iron deficiencies with higher propensity to viral infection has limited the development of novel antiviral strategies. Research in zinc’s role in the antiviral response could open a new, cheaper alternative therapy for Dengue, West Nile and Yellow Fever, in West African countries such as Ghana, Nigeria and Benin.
Dengue, West Nile and Yellow Fever are collectively known as the flaviviruses. The World Health Organisation has predicted a maximum infection rate per annum of 7.75 million individuals in Nigeria, and 1 million infections in Togo, Cameroon, Benin and Ghana. A recently identified protein, RIG-1, is able to detect infection by flaviviruses in human cells. Research at the Laboratory of Molecular Genetics at Kyoto University, Japan has deepened understanding of this protein and our initial response to viral infection. The antiviral response begins when the RIG-1 protein detects the virus in cells, for which zinc has recently shown to be an essential structural component and cofactor.
Zinc has also been shown to be important in the production of T cells, infection fighting immune cells that can specifically recognise the virus. It’s important for the development of young T and B cells to mature forms that are able to fight the virus by producing neutralizing antibodies and killing infected cells. In the zinc deficient state, global immune system reprogramming reduces the production of antiviral T and B cells.
Zinc deficiency is usually associated with high amounts of phytate, which is found in abundance in unpolished rice, maize, groundnut and cereal. Phytate forms an insoluble complex with zinc in the small intestine – meaning zinc cannot be absorbed into the blood stream. Alarmingly, a study at the university of Ghana found that 46% of adolescents in the Greater Accra and Upper East regions were zinc deficient in a sample totaling over 300 individuals.
The traditional practices of communal eating and staple diets in low-income households may mean whole communities are zinc deficient as a result of high-phytate diets. Such clustering of zinc deficient individuals puts entire communities at risk of being unable to detect infection by viruses, and to mount the necessary immune response to stop those viruses proliferating. This concept is referred to as ‘herd immunity’. If no individuals can mount an immune response to the virus, the virus proliferates and spreads at a faster rate through a localized community. Nutrition is the factor that provides the basal, starting point from which every individual is able to mount an immune response. Flaviviruses may therefore have an unimpeded highway through ‘immunocompromised’ communities, the establishment of which is likely exacerbated by cultural practices of communal living and staple diet subsistence.
A vaccine against Dengue Fever is yet to be developed, but economic burdens will slow its distribution if a vaccine does pass trial. The same economic frailty that exacerbates malnutrition and viral flow would limit access to vaccination therapy. As such, cheaper alternative therapies need to be considered. The collection of dietary data in isolated West African communities is paramount to assess the viability of zinc supplementation in potentially deficient communities, those economically confined to a high-phytate, rice based diet that may serve to increase the pool of immunocompromised individuals. Understanding the extent of nutrient malnourishment of factors crucial to the immune responses could allow us to delay and impede the flow of viruses through communities, in the current absence of a vaccination promise.
- Samir B, Peter W. et al – The global distribution and burden of Dengue. Nature, Volume 496 (7446) pg. 504-507
- Achindiba Abbey G. – Prevalence of zinc deficiency among Ghanaian adolescents versus food components of zinc and phytate. Dept. of Nutrition and Food Science. University of Ghana 2004
- Ibs K, Rink L. – Zinc altered immune function. The Journal of Nutrition 2003 pg. 1452-1456