The therapeutic efficacy of the Spirulina hot water soluble extract has been evaluated against HSV-1 corneal infection in hamsters. Hamsters fed with the extract at a dose of 100 or 500 mg/Kg body weight per day, for 7 days before the HSV-1 infection, have shown longer mean survival times, while all the animals of the control group died 8 days after the infection; about 15-30% of the animals treated with the extract remained alive. No evidence of toxicity was detected in the hamsters fed with food containing the Spirulina extract. These results suggest that the consumption of Spirulina in the diet may prevent herpetic encephalitis.11
The aqueous extract of S. maxima has also been tested using the zosteriform HSV-2 infection in mice. These animals received a topical application of the extract immediately before the viral infection, and after that, twice a day, for 5 days. The extract was used at a concentration of 3 mg/Kg body weight per day. HSV-2 could be recovered from a site of viral inoculation on the third day after infection, and on the next 5 days. There were no differences on the viral isolation from the zosteriform infection in the viral infected-control group, and in the Spirulina-treated infected group. However, 5 days after the viral infection, 7 out of 12 (58%) animals from the control-infected group developed signs of encephalitis, in comparison to 1 out of 12 (8.3%) from the Spirulina-treated infected group. The infected group showed severe signs of encephalitis like, kyphosis, piloerection, and rear limb ataxia, as well as a reduction on the body weight gain. The Spirulina-treated infected group showed a similar rate of body weight gain than the control groups: the Spirulina-treated mock infected and the noninfected groups. The virus was recovered from the central nervous system of the infected control group, but not from the Spirulina-treated infected group. These results suggest that S. maxima extract does not prevent the initial infection on the skin, but may successfully interfere with the neuroninvasiveness property of herpes simplex virus.21
When zosteriform infected mice received orally the Spirulina aqueous extract at the same concentration used for topical application, there were no differences on the rate of infection or development of encephalitis, between the infected-untreated group and the infected Spirulina-treated group. These findings were probably due to a low dose of the extract. None of the Spirulina-treated animals showed signs of toxicity, neither by topical application or oral ingestion. Therefore, it would be important to test higher concentrations or even better, to fractionate the extract and use higher concentration of the fractions with antiviral activity.21
In agreement with the idea that Spirulina contains different compounds with antiviral properties, an antiviral protein with molecular weight of 29 kDa has been identified from S. plantensis. This protein is active against the viral diseases produced by the nuclear polyhedrosis virus in the silkworm larvae Bombyx mori. The mechanism for this antiviral activity is still unknown and it could be similar to other antiviral proteins with carbohydrate-binding properties like cyanovirin.22
Proteins with antiviral properties have been found in other cyanobacteria like Nostoc ellipsosporum. From these cyanobacteria, an antiviral 11-kDa protein named cyanovirin (CV-N) has been isolated and purified. This protein belongs to the group of carbohydrate-binding proteins (CBP) which have been found in many species including cyanobacterias, sea corals, alga, plants, invertebrates, and vertebrates. CBPs have shown a potent anti-HIV activity, presumably acting by direct binding to the glycans that are abundantly present on the HIV-1 gP120 envelope. CN-V has shown to inhibit HIV infections in a vaginal transmission model in Macaca fascicularis infected with a pathogenic recombinant chimeric SIV/HIV.23
The antiviral effect observed in experiments in vivo with Spirulina or its extracts can not only be explained on the basis of a direct antiviral activity against the virus, because Spirulina has also immunomodulatory properties. In human volunteers who have received an oral dose of a hot water extract of Spirulina, more than 50% of them showed an enhancement of NK functions (IFN gamma production and cytolysis). The INF gamma was produced in an IL-12/IL18 dependent-pathway. It has been suggested that Spirulina may be involved in the signaling response through Toll in blood cells. In vitro stimulation of blood cells with Bacillus Calmette-Guerin (BCG) was more potent in volunteers who received the Spirulina. These results indicate that in humans Spirulina acts directly on myeloid lineages either directly or indirectly on NK cells.24
Patients with chronic viral hepatitis treated for 1 month with Spirulina did not show any improvement in the aminotransferases levels or in their general state.25 This result could be explained because until now, there is not any in vitro study showing that Spirulina has an antiviral effect on hepatitis B or C viruses, which are the viruses involved in chronic hepatitis. On the other hand, even though Spirulina could enhance the immune response of the patients, it is known that viral chronic hepatitis are related to alterations on the immune response induced by the viral infections.
Negative results with Spirulina either in patients or experimental animals could be the result of an insufficient concentration of the antiviral principle in the anatomical site where the virus is being replicated, or that the virus tested is not sensitive to the antiviral principles produced by Spirulina. For example S. platensis extracts have shown no antiviral activity against viruses like poliovirus and coxsackievirus.12 A similar situation has been found with S. maxima which has no antiviral activity against human adenovirus, poliovirus, rotavirus SA-11, measles vaccine virus, SSPE, and VSV.
Teas et al., 2004, have pointed out an intriguing epidemiological finding about HIV/AIDS rates. There is an enormous difference in the rate of HIV/AIDS incidence and prevalence found in Eastern Asia, 1/10,000 adults in Japan and Korea, compared to Africa, 1/10 adults, and such differences can be explained not only on the basis of intravenous drug use but also on the basis of sexual behavior. Even in Africa the HIV/AIDS rates vary, Chad reported low rates (2-4/100). These epidemiological data have been analyzed together with the alga consumption. People in Japan and Korea eat seaweed daily, and the Kanamemba, one of the major tribal group in Chad eat Spirulina, daily. The every day average consumption of alga in Asia and Africa ranges from 1 to 2 tablespoons (3-13 g). According to this general analysis, they have proposed the hypotheses that some of the differences in HIV/AIDS rates could be related to a regular consumption of dietary alga, which could prevent HIV infection and reduce the viral load among those infected. This hypothesis sounds interesting but it requires a deeper analysis of all the possible variables in order to determine if
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