Combination Therapy of Zinc and Trimethoprim Inhibits Influenza A Virus in Chick Embryo  

Abstract

Background. Respiratory RNA viruses including influenza virus have been a cause of health and economic hardships. These viruses depend on its host for replication and infection. Influenza virus infection is lethal to the chick embryo. We examined whether a combination of trimethoprim and zinc (Tri-Z), that acts on the host, can reduce the lethal effect of influenza A virus in chick embryo model. Method. Influenza virus was isolated from patients and propagated in eggs. We determined viral load that infects 50% of eggs (50% egg lethal dose, ELD50). We introduced 10 ELD50 into embryonated eggs and repeated the experiments using 100 ELD50. A mixture of zinc oxide (Zn) and trimethoprim (TMP) (weight / weight ratios ranged from 0.01 to 0.3, Zn/TMP with increment of 0.1) was tested for embryo survival of the infection (n = 12 per ratio, in triplicates). Embryo survival was determined by candling eggs daily for 7 days. Controls of Zn, TMP, saline or convalescent serum were conducted in parallel. The effect of Tri-Z on virus binding to its cell surface receptor was evaluated in a hemagglutination inhibition (HAI) assay using chicken red cells. HAI effect was expressed as scores where ++++ = no effect; 0 = complete HAI effect.Results. TMP, Zn or saline separately had no effect on embryo survival, none of the embryos survived influenza virus infection. All embryos treated with convalescent serum survived. Tri-Z, at ratio range of 0.15 to 0.2 (optimal ratio of 0.18) Zn / TMP, enabled embryos to survive influenza virus despite increasing viral load (>80% survival at optimal ratio). At concentration of 15 microgram/ml of optimal ratio, Tri-Z had total HAI effect (scored 0). However, at clinical concentration of 5 microgram/ml, Tri-Z had partial HAI effect (++).Conclusion. Acting on host cells, Tri-Z at optimal ratio can reduce the lethal effect of influenza A virus in chick embryo. Tri-Z has HAI effect. These findings suggest that combination of trimethoprim and zinc at optimal ratio can be provided as treatment for influenza and possibly other respiratory RNA viruses infection in man.

Tile: Combination Therapy of Zinc and Trimethoprim Inhibits Influenza A Virus In Chick Embryo

“…Under experimental conditions, Zn combines with TMP forming xed complex preserving the anti-bacterial properties of TMP but without evidence of anti-virus [ 40 , 41]. Whereas, in-vivo, the non-xed formulation of Zn and TMP (Tri-Z) inhibited in uenza virus in chick embryo, similar to that in man [8], enabling embryo survival of infection. The viral inhibition of Tri-Z appears to be ratio dependent.…”

“…Zinc ions were demonstrated to inhibit RNA virus, rhinovirus [7]. When combined at a ratio TMP and Zn may treat respiratory RNA virus infections [ 8].…”

“…There are several respiratory RNA viruses including in uenza virus, Coronavirus, Respiratory Syncytial virus and rhinovirus [ 9]. To infect, these viruses require attaching to the host cell surface receptors, internalization and replication using the host nucleus and intracellular organelles [2,8,9]. We used in uenza virus as a model because it shares similar mechanisms for infection, replication and pathogenesis with that of the respiratory RNA viruses [ 3,9].…”

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