In April of this year, the Lyme Disease Foundation held its 11th International Research Conference on Lyme Disease and other Tick-Borne Illnesses. The focus of this years conference was supposed to emphasize the treatment of Lyme disease, but there was really very little new on treatment. Instead, the conference focused more on the pending vaccines and current vaccine research continuing in Europe. Despite the lack of new breakthrough miracle cures, there were some interesting topics discussed that will help us further our understanding of this complex and convoluted disease.
One question that Lyme patients and their doctors often face is whether or not they should use steroids such as prednisone to ameliorate their symptoms of Lyme disease. In a small study done on healthy beagles, Dr. Straubinger, DVM, presented evidence that steroids should be used cautiously. He took four healthy young beagles and infected them with Lyme disease. They became symptomatic with intermittent bouts of lameness that usually resolved in less than five days. After the first year post infection, all of the dogs were culture positive and tested positive for active infection, but the dogs had few outward signs of active disease.
He then treated the dogs with prednisone corticosteroid for fourteen days. Within five to eight days after the cessation of the steroid therapy, three of the dogs developed severe debilitating acute arthritis. Fifteen days later, the dogs were sacrificed and twenty-five tissues were cultured for the presence of organisms. All of the dogs were still infected 566 days post-infection.
The dogs were symptom free during steroid treatment, but soon developed severe, crippling polyarthritis shortly after the steroids were withdrawn. During therapy the dog's cellular immune response was severely suppressed, which also suppressed the symptoms of arthritis, but after the immunosuppressive drug was withdrawn there was rapid onset of arthritis, joint pain, swelling, and lameness. Within the joint tissue many organisms were recovered, indicating a reactivation of subclinical disease. Dr. Straubinger concluded that while steroids can give temporary relief to dogs, it can also reactivate infections in asymptomatic dogs with active disease.
The significance of this study becomes more apparent when you realize that at the NH-I conference the previous year, Dr. Straubinger presented another study with Dr. Max Appel showing that dogs can have chronic active Lyme disease despite antibiotic treatment. They took six beagles infected with Lyme and treated them with high doses of either doxycycline or amoxicillin for four weeks. Five still had active infection two years later after antibiotic treatment. This means we can't be certain if active infection remains post-treatment even in the absence of symptoms. This second dog study suggests that if active infection is still present and steroids are given, it could reactivate active Lyme disease and cause severe acute polyarthritis. [No data is available using steroids and antibiotics together in dogs with active infection but sub clinical symptoms.]
Another interesting and provocative presentation was one given by Dr. Willy Burgdorfer pertaining to some evidence that certain mosquitoes can be competent carriers and potentially transmitters of Lyme disease to humans. Dr. Burgdorfer was referring to work done in the Czech Republic in 1993 by Dr. Halouzka showing the presence of Borrelia afzellii within the salivary glands of mosquitoes in southern Moravia. Previous work cited by Dr. Burgdorfer indicated that live spirochetes have been successfully transmitted experimentally from Aedes aegypti mosquitoes to birds.
In America in 1985, Drs. Magnarelli, Johnson, and Barbour showed that three to eleven percent of the mosquitoes in the northeastern part of the US are infected with a spirochete that can live up to fourteen days. Later they showed that twenty-three percent of mosquitoes that fed on host animals infected with Borrelia burgdorferibecame infected themselves with the pathogen, which survived up to three days within the salivary glands.
In 1966, there was one reference in the medical literature describing a bull's-eye rash after the bite of a mosquito.
While no direct evidence exists that mosquitoes are a vector of Lyme disease to humans, we know that all the pieces of the puzzle necessary for them to be competent vectors are in place.
Recently, it was announced by the Institute for Genomic Research that nearly the entire gene sequence of Borrelia burgdorferi had been sequenced. What this means is that all of the genetic code of the DNA within the bacteria is now known, and can be compared to the genes of other bacteria that are stored in a computer library of known genes.
It was found that Borrelia burgdorferi has one main chromosome that has 853 genes, most of which are used for basic metabolism and other known functions. What was a surprise is that forty percent of the 838 additional plasmid genes are of unknown function. Also, many of these genes are paralogs or have sister genes on other plasmids, suggesting that the bacteria has a built-in capacity to create antigenic variation. This might account for this species of bacteria's ability to have so many strains and genospecies. A related bacteria that causes relapsing fever has over two dozen genospecies, and we are finding a similar pattern emerging for the Lyme spirochete as well.
It appears that the Lyme spirochete and the spirochete that causes syphilis are only about fifty percent similar genetically, and that the syphilis bacterium completely lacks the additional 838 plasmid genes of the Lyme bacterium. Since the plasmid genes are the genes which code for all of the transmembrane proteins and OSP lipoproteins, it appears that Borrelia, at least from a genetic standpoint, has a greater range of antigenic variation than the treponemes. This could suggest to some that the Lyme spirochete is more evolved, more advanced, and better equipped to deal with host immune systems.
The genomic work suggests that the Lyme spirochete only has rudimentary mechanisms for metabolism and is quite dependent on its host to provide fats, proteins, carbohydrates, amino acids and iron to survive. This might account for the bacteria's known ability to become metabolically inactive for long periods of time. If it cannot synthesize efficiently what it needs from basic chemicals, it is an evolutionary advantage to be able to go dormant for long periods of time until food becomes available.
One such growth-limiting nutrient is N-Acetyl Glucasamine (NAG), which is found in connective tissue and in the ticks chitinous shell. The gene researcher, Dr. Claire Fraser, found a gene that codes for a protein that transports NAG into the bacterium. If this protein could be targeted by researchers, it could be a potential inhibitor of this bacteria. It also suggests that NAG may be the bacteria's source of energy when inside the tick.
Other researchers, using the TIGR computer library of gene sequences at the NIH, found that the Lyme spirochete has some gene sequences that are similar to other bacterial toxins. One toxin in particular which seems to be active and functional is a cholera-like toxin. Using a special ribosylation assay this Borrelia protein seems to have some biologically active toxic ability, but, since his assay was originally designed for another bacteria, it is not sensitive enough to determine borrelia's complete potential to produce biologically active toxins. Further work needs to be done.
The most encouraging aspect of this conference is that it is clear that we now have powerful new technologies at our disposal that were not available even a few years ago. These new technologies will open new doors to our insight of this bacteria that we never dreamed possible when it was first isolated in 1981.