Timber rattlesnake (Crotalus horridus): Biology, conservation, and envenomation in the Upper Mississippi River Valley (1982-2020).

The Timber Rattlesnake (Crotalus horridus) is the largest pit viper in the Northern United States and is the prominent venomous snake species indigenous to the bluff land habitats of the Upper Mississippi River Valley (UMRV). Conservation of C. horridus in this geographic region not only preserves the ecosystem's biodiversity and ecological balance, but also assures the continued study of their biomedically important venoms/toxins. Field studies of C. horridus biology and natural history performed from 1985 to 2015 in southeastern Minnesota and western Wisconsin along the Mississippi River showed populations have declined. Consequently, the implementation of improved conservation measures afforded the species protective status in both states. Historically, accounts of Timber Rattlesnake bites in the UMRV have been sparse, and medical consequences of envenomation have had limited documentation. However, in recent decades cases of envenomation by C. horridus have continued to occur. Retrospective analysis of clinical toxinology consultations documented from 1982 to 2020 on cases of envenomation by C. horridus in the UMRV revealed a very low incidence of bites annually and revealed that their venom can induce a rapid and precipitous decline in platelets.

Crotalus morulus (Viperidae: Crotalinae) envenoming and treatment with F(ab')2 antivenom.

We present the first published case of Tamaulipan Rock Rattlesnake (Crotalus morulus) envenoming. A 54-year-old male professional herpetologist was bitten on the left thumb by a captive C. morulus. Pain, swelling, bruising, and pressure in the thumb were experienced within minutes. On presentation, he reported 7/10 pain and had firm edema in his thumb and thenar eminence. Initial laboratory studies showed normal platelet count, PT, PTT, and creatine kinase. He was treated with pain medication and 10 vials of crotalidae immune F(ab')2 (equine) antivenom approximately 3 h post envenoming. Lymphangitic streaking and axillary lymphadenopathy developed, followed by progression of edema, emergence of a hemorrhagic bulla, and declining platelets, prompting treatment with two additional 10-vial antivenom doses. His platelet count declined to 125 × 103/µL 24 hours post envenoming and he developed numbness in his thumb. Following antivenom therapy completion no further decline in platelets occurred and thrombocytopenia improved to 131 × 103/µL prior to discharge 46 hours post envenoming; fibrinogen, PT, PTT, and CK remained normal. He had no residual signs or symptoms 5 months later. C. morulus venom includes proteolytic venom enzymes that induce local soft tissue destruction, pain, and edema with ecchymosis and blister formation. Although C. morulus venom contains a unique disintegrin, morulustatin, no fibrinogenolytic activity was observed.

Latrodectus geometricus (Aranea: Theridiidae) envenoming: Rapid resolution of symptoms following F(ab')2 antivenom therapy.

The Brown Widow spider (Latrodectus geometricus) is an invasive species whose geographic range has been expanding worldwide. It is a relative species of the Black Widow and Red-backed spiders of the genus Latrodectus. Despite its broad geographic distribution cases of Brown Widow envenomation have rarely been documented. The venom of L. geometricus is similar to the venom of L. mactans with the primary venom component being alpha-latrotoxin, and consequent envenoming by L. geometricus to humans has resulted in symptoms similar to those reported for other Latrodectus spp. Specific FDA approved Latrodectus antivenom (IgG) available in North America has been effectively used in treating venom-induced symptoms following L. mactans envenoming. The patient reported here involved a confirmed L. geometricus envenoming who was efficaciously treated with an alternately available F(ab')2 antivenom from Mexico.

Crotalus durissus terrificus (viperidae; crotalinae) envenomation: Respiratory failure and treatment with antivipmyn TRI® antivenom.

We report an envenomation to a professional herpetologist by a South American rattlesnake (Crotalus durissus terrificus) that resulted in respiratory failure, and therapeutic improvement following antivenom administration. A 56-year-old male was bitten on the left wrist by a Crotalus durissus terrificus (C. d. terrificus) while attempting to tube the snake for maintaining safe control while performing venom extraction. The patient was intubated due to rapidly ensuing respiratory failure and administration of Antivipmyn-TRI® was initiated while being transported via ambulance. The patient was admitted to the hospital unconscious and unresponsive. Mechanical ventilation was required until 5 h after completion of antivenom administration. No significant adverse effects were observed with antivenom administration. The patient was discharged approximately 55 h following envenomation. This is the first reported case in the United States of a patient following a C. d. terrificus envenomation with consequent respiratory failure, and in which Antivipmyn-TRI® was successfully administered.

Local envenomation from the bite of a juvenile false water cobra (Hydrodynastes gigas; Dipsadidae).

The false water cobra (Hydrodynastes gigas) is a non-front-fanged colubroid snake frequently exhibited in zoos, and maintained by amateur collectors. Little detailed documentation regarding the time-course of symptoms development and the consequences of their bites to humans has been published. Reported here is a case of envenoming in a 25 yo male that occurred after the bite of a juvenile H. gigas. The victim was bitten on the fourth digit of the left hand while processing the snake for sex determination, and the snake remained attached to the digit for approximately 30 s; there was no jaw advancement. Within 5 min, intense local pain developed, and at 4hr post bite the entire dorsal aspect of the hand was significantly edematous, The local effects progressed and involved the entire forearm, and the local pain referred to the axillary region. Mild paresthesia and local blanching ("pallor") were noted in the affected digit, but resolved within 7 days. The clinical course in the patient showed that moderate localized symptoms may result from the bite of a juvenile H.gigas.

Antivenom for snakebite envenoming in Sri Lanka: the need for geographically specific antivenom and improved efficacy.

Sri Lanka is a tropical developing island nation that endures significant economic and medical burden as a result of snakebite envenomation, having not only a high prevalence of envenomations, but also one of the highest incidence rates (200 snakebites/100,000 people/year) of venomous snakebite in the world (Kasturiratne et al., 2005). Ironically, the very snakes responsible for this human morbidity and mortality are a valuable biomedical and ecological national resource, despite the medical and economic consequences of envenomation. Currently, no snake antivenom is produced using venoms from native Sri Lankan snakes as immunogens, and there is a true need for an efficacious Sri Lanka, poly-specific snake antivenom. An approach to fulfilling this need via combining the scientific, technological and economical resources from Costa Rica and the United States with the knowledge and talent of Sri Lankan official governmental agencies, legal counsels, environmental, medical and veterinary academic institutions, and religious and cultural leaders has been initiated, coordinated and funded by Animal Venom Research International (AVRI), a nonprofit charity. This bridging of nations and the cooperative pooling of their resources represents a potential avenue for antivenom development in a developing country that suffers the consequences of few specific resources for the medical management of venomous snakebite. The desired final outcome of such an endeavor for Sri Lanka is, most importantly, improved medical outcomes for snakebite patients, with enhanced and expanded science and technology relating to snake venoms and antivenoms, and the collateral benefits of reduced economic cost for the country.

Structurally distinct nicotine immunogens elicit antibodies with non-overlapping specificities.

Nicotine conjugate vaccine efficacy is limited by the concentration of nicotine-specific antibodies that can be reliably generated in serum. Previous studies suggest that the concurrent use of 2 structurally distinct nicotine immunogens in rats can generate additive antibody responses by stimulating distinct B cell populations. In the current study we investigated whether it is possible to identify a third immunologically distinct nicotine immunogen. The new 1'-SNic immunogen (2S)-N,N'-(disulfanediyldiethane-2,1-diyl)bis[4-(2-pyridin-3-ylpyrrolidin-1-yl)butanamide] conjugated to keyhole limpet hemocyanin (KLH) differed from the existing immunogens 3'-AmNic-rEPA and 6-CMUNic-BSA in linker position, linker composition, conjugation chemistry, and carrier protein. Vaccination of rats with 1'-SNic-KLH elicited high concentrations of high affinity nicotine-specific antibodies. The antibodies produced in response to 1'-SNic-KLH did not appreciably cross-react in ELISA with either 3'-AmNic-rEPA or 6-CMUNic-BSA or vice versa, showing that the B cell populations activated by each of these nicotine immunogens were non-overlapping and distinct. Nicotine retention in serum was increased and nicotine distribution to brain substantially reduced in rats vaccinated with 1'-SNic-KLH compared to controls. Effects of 1'-SNic-KLH on nicotine distribution were comparable to those of 3'-AmNic-rEPA which has progressed to late stage clinical trials as an adjunct to smoking cessation. These data show that it is possible to design multiple immunogens from a small molecule such as nicotine which elicit independent immune responses. This approach could be applicable to other addiction vaccines or small molecule targets as well.

Vaccination against nicotine alters the distribution of nicotine delivered via cigarette smoke inhalation to rats.

Preclinical models of nicotine vaccine pharmacology have relied on i.v. or s.c. administration of nicotine. Models using cigarette smoke inhalation might more accurately simulate nicotine exposure in smokers. Nicotine vaccine effects were examined in rats using two cigarette smoke exposure models: a 10 min nose-only exposure (NSE) producing serum nicotine levels equivalent to the nicotine boost from 1 cigarette in a smoker, and a 2h whole-body exposure (WBE) producing serum nicotine levels similar to those associated with regular mid-day smoking. Vaccination prior to 10min smoke NSE reduced nicotine distribution to brain by 90%, comparable to its effect on nicotine administered i.v. Vaccination prior to 2 h smoke WBE reduced nicotine distribution to brain by 35%. The nicotine concentration in broncheoalveolar lavage (BAL) fluid obtained after 2 h WBE was increased by 230% in vaccinated rats but was also increased in rats passively immunized with a nicotine-specific monoclonal antibody, and so was likely due to transfer of antibody from serum rather than local production at the pulmonary mucosa. Nicotine-specific IgA was not detectable in BAL fluid, but titers in serum were appreciable at 21-25% of the IgG titer and could contribute to vaccine efficacy. Both vaccination and passive immunization are effective in reducing nicotine distribution to brain in rats when nicotine is delivered via inhaled cigarette smoke. These data validate results previously obtained in rodents for nicotine vaccines using i.v. or s.c. nicotine dosing and provide a quantitative method for studying aspects of nicotine exposure which are unique to cigarette smoke inhalation.

Hyperglycemia in acute aluminum phosphide poisoning as a potential prognostic factor.

Aluminum phosphide (AlP) is a solid fumigant widely used in Iran as a grain preservative. When reacted with water or acids, AIP produces phosphine gas, a mitochondrial poison that interferes with oxidative phosphorylation and protein synthesis. Poisoning by AIP is one of the most important causes of fatal chemical toxicity in Iran. There are few studies in the medical literature addressing prognostic factors associated with AlP poisoning. In this prospective study conducted across a 14-month period commencing on 21st March 2006, we enrolled all patients admitted to the ICU of Loghman-Hakim Hospital Poison Center (Tehran, Iran) with AIP poisoning, no history of diabetes mellitus diagnosed before hospitalization, and normal body mass index. We recorded patient-specific demographic information, blood glucose level on presentation (before treatment), arterial blood gas (ABG) analysis, time elapsed between ingestion and presentation, ingested dose, duration of intensive care admission, and outcome data related to each presentation. We enrolled the group of patients who survived the intoxication as a control group and compared their blood glucose levels with those who died because of AlP poisoning. Data were analyzed by Statistical Product and Service Solutions (SPSS) software (Version 12; Chicago, Ilinois, USA) using logistic regression, Pearson correlation coefficient and Student's t-test. P values of 0.05 or less were considered as the statistical significant levels. Forty-five patients (21 women and 24 men) with acute AlP poisoning were included in the study. The mean age was 27.3 +/- 11.5 years (range: 14-62 years). Thirteen patients survived (29%) and 32 expired (71%). AlP poisoning followed deliberate ingestion in all patients. The time elapsed between ingestion and arrival at the hospital was 3.2 +/- 0.4 h. There was no significant difference between survived and non-survived groups according to age, gender, and time to treatment. However, the difference between mean blood glucose levels in survived (143.4 +/- 13.7 mg/dL) and non-survived (222.6 +/- 20 mg/dL) cases was statistically significant (P = 0.021). There was no significant correlation between blood glucose level and time to treatment, age, gender, pH, HCO3 concentration, and ingested dose. Twenty-three (71.9%) of non-survived and four (30.8%) of survived patients had a blood glucose level greater than 140 mg/dL. After adjusting according to age, gender, ingested dose, pH and HCO3 concentration The odds ratio for hyperglycemia as a risk factor for death was 5.7 (CI of 1.4-23.4). In our study, patients who succumbed to AIP poisoning had significantly higher mean blood glucose levels than those who survived. This correlation of hyperglycemic effect and mortality suggests that it may be useful in guiding risk assessment and treatment of AIP poisoning. Management of hyperglycemia may have a useful role in treatment of these patients by allowing increased entrance of glucose into cells and reducing oxygen consumption.

Enhanced immunogenicity of a bivalent nicotine vaccine.

The efficacy of nicotine vaccines for smoking cessation is dependent upon their ability to elicit sufficiently high serum antibody concentrations. This study compared two nicotine immunogens representing different hapten presentations, 3'-aminomethyl nicotine conjugated to recombinant Pseudomonas exoprotein A (3'-AmNic-rEPA) and 6-carboxymethlureido nicotine conjugated to keyhole limpet hemocyanin (6-CMUNic-KLH), and assessed whether their concurrent administration would produce additive serum antibody concentrations in rats. Effects of vaccination on nicotine pharmacokinetics were also studied. Vaccination of rats with these immunogens produced non cross-reacting nicotine-specific antibodies (NicAb). Serum NicAb concentrations elicited by each individual immunogen were not affected by whether the immunogens were administered alone as monovalent vaccines or together as a bivalent vaccine. The total NicAb concentration in the bivalent vaccine group was additive compared to that of the monovalent vaccines alone. Higher serum NicAb concentrations, irrespective of which immunogen elicited the antibodies, were associated with greater binding of nicotine in serum, a lower unbound nicotine concentration in serum, and lower brain nicotine concentration. These results demonstrate that it is possible to design immunogens which provide distinct nicotine epitopes for immune presentation, and which produce additive serum antibody levels. The concurrent administration of these immunogens as a bivalent vaccine may provide a general strategy for enhancing the antibody response to small molecules such as nicotine.

Changes in maternal and fetal nicotine distribution after maternal administration of monoclonal nicotine-specific antibody to rats.

Vaccination against nicotine to elicit the production of nicotine-specific antibodies is a potential treatment for tobacco addiction which reduces nicotine distribution from serum to brain. Vaccination of pregnant rats also reduces the distribution of maternally-administered nicotine to the fetal brain. Whether this is due to maternal antibody reducing the transfer of nicotine from mother to fetus, or to fetal antibody altering the distribution of nicotine within the fetus, is not clear. In the current study, passive immunization of rats with the murine monoclonal nicotine-specific antibody Nic311 was used as a surrogate for vaccination because antibody transfer to the fetus was anticipated to be lower than with vaccination. Pregnant rats received nicotine from gestational day (GD) 18-20 as frequent i.v. boluses to simulate nicotine exposure from smoking. Nic311 was administered at doses of 30, 80 or 240 mg/kg on GD 19. Fetal serum Nic311 levels on GD 20 were <3% of concurrent maternal levels, but concentrations of up to 20 ug/ml in fetal serum were obtained owing to the very high levels in maternal serum. Accumulation of the chronically administered nicotine, measured on GD 20, was not changed by Nic311 treatment in either maternal or fetal brain. The early distribution of nicotine to maternal brain, measured 5 min after a dose, was markedly reduced by Nic311, while the early distribution of nicotine to whole fetus and fetal brain was not substantially altered. These data suggest that the limited transfer of Nic311 to the fetus in turn limits the ability of Nic311 to reduce nicotine distribution to the fetal brain.

Vaccination against nicotine does not prevent nicotine-induced changes in fetal nicotinic receptor binding and c-fos mRNA expression in rats.

Gestational exposure of rats to nicotine produces long-lasting alterations in brain development. Vaccination of adult female rats against nicotine reduces the distribution of maternally administered nicotine to fetal brain, suggesting that vaccination might protect against these effects. In the current study, the effects of vaccination on nicotine-induced changes in fetal (3)H-epibatidine binding and c-fos mRNA expression were evaluated using tissue from a previous pharmacokinetic study of vaccination. An intermittent nicotine dosing regimen designed to resemble nicotine intake in a smoker was administered from GD1-20. Peak nicotine levels in fetal brain were reduced by vaccination, whereas the chronic accumulation of nicotine in fetal brain was not. Gestational nicotine exposure produced significant increases in (125)I-epibatidine binding to brain and spinal cord on GD20, and decreased c-fos mRNA expression in fetal striatum, adrenal and lung. Vaccination did not significantly alter these effects. These data suggest that nicotine dosing, using a clinically relevant intermittent bolus dose regimen, produces substantial changes in fetal nicotinic receptor and c-fos mRNA expression. The decrease in c-fos mRNA expression contrasts with previously reported increases, and suggests that the nicotine dosing regimen used may influence its effects. The lack of effect of vaccination suggests that the cumulative exposure of fetal tissues to nicotine may influence the measured parameters to a greater extent than peak exposure levels.

Differential effects of passive immunization with nicotine-specific antibodies on the acute and chronic distribution of nicotine to brain in rats.

Vaccination against nicotine blocks or attenuates nicotine-related behaviors relevant to addiction in rats. Passive immunization with nicotine-specific antibodies is an alternative to vaccination with the potential advantages of allowing control of antibody dose and affinity. In the current study, the effects of two antibodies on the distribution of nicotine to brain were evaluated during chronic nicotine administration in rats; the monoclonal antibody Nic311 (K(d) = 60 nM) and nicotine-specific antiserum (K(d) = 1.6 nM). Nicotine was administered via repeated i.v. bolus doses over 2 days and antibody was administered during the first day. Neither antibody appreciably reduced the chronic accumulation of nicotine in brain, despite high protein binding of nicotine in serum (98.9%) and a 73% reduction in the unbound serum nicotine concentration with the highest Nic311 dose. However, both antibodies substantially reduced the early distribution of nicotine to brain 5 min after a dose. The higher affinity antibody was no more effective than Nic311. The highest Nic311 dose produced serum antibody levels 10 times higher than those reported with vaccination. The efficacy of Nic311 was dose-related, with the highest dose producing a 76% decrease in the early distribution of nicotine to brain. These findings, along with previous data, suggest that the primary effect of passive immunization is to slow, rather than prevent, the distribution of nicotine to brain. In the setting of chronic nicotine dosing, antibodies with a moderate affinity for nicotine produced substantial effects on the early distribution of nicotine to brain and were as effective as higher affinity antibodies.

Monoclonal nicotine-specific antibodies reduce nicotine distribution to brain in rats: dose- and affinity-response relationships.

Vaccination against nicotine is being studied as a potential treatment for nicotine dependence. Some of the limitations of vaccination, such as variability in antibody titer and affinity, might be overcome by instead using passive immunization with nicotine-specific monoclonal antibodies. The effects of antibodies on nicotine distribution to brain were studied using nicotine-specific monoclonal antibodies (NICmAbs) with K(d) values ranging from 60 to 250 nM and a high-affinity polyclonal rabbit antiserum (K(d) = 1.6 nM). Pretreatment with NICmAbs substantially increased the binding of nicotine in serum after a single nicotine dose, reduced the unbound nicotine concentration in serum, and reduced the distribution of nicotine to brain. Efficacy was directly related to antibody affinity for nicotine. Efficacy of the highest affinity NICmAb, NICmAb311, was dose-related, with the highest dose reducing nicotine distribution to brain by 78%. NICmAb311 decreased nicotine clearance by 90% and prolonged the terminal half-life of nicotine by 120%. At equivalent doses, NICmAb311 was less effective than the higher affinity rabbit antiserum but comparable efficacy could be achieved by increasing the NICmAb311 dose. These data suggest that passive immunization with nicotine-specific monoclonal antibodies substantially alters nicotine pharmacokinetics in a manner similar to that previously reported for vaccination against nicotine. Antibody efficacy is a function of both dose and affinity for nicotine.

Tissue-dependent effects of immunization with a nicotine conjugate vaccine on the distribution of nicotine in rats.

Vaccination of rats against nicotine reduces nicotine distribution to brain even at nicotine doses greatly exceeding the estimated binding capacity of the available antibody. This observation suggests a differential effect by which vaccination reduces nicotine distribution to brain to a greater extent than to other tissues. To test this hypothesis, vaccinated rats received a single intravenous nicotine dose equal to twice the estimated binding capacity of nicotine-specific antibody in vaccinated rats. The total and bound serum nicotine concentrations were higher in the vaccinated rats compared to controls, while the unbound serum nicotine concentration was lower. Distribution of nicotine to brain was reduced in vaccinated rats in a time-dependent manner, with a greater reduction at 1 min (64%) than at 25 min (45%). Vaccination reduced nicotine distribution to muscle, testis, spleen, liver, heart, and kidney, but to a lesser extent than to brain, while nicotine distribution to fat was increased. Chronically infused nicotine showed a similarly altered pattern of tissue distribution in vaccinated rats, but differences were in general smaller than after a single nicotine dose; brain nicotine concentration was 24% lower in vaccinated rats, while lung nicotine concentration was higher. The presence of nicotine-specific antibody in tissues may have contributed to the increased nicotine concentrations in fat and lung. These data suggest that vaccination reduces nicotine distribution to brain not only by sequestering nicotine in serum but also by redirecting tissue distribution disproportionately away from brain, such that nicotine concentrations are reduced to a greater extent in brain than in other tissues.

Maternal vaccination against nicotine reduces nicotine distribution to fetal brain in rats.

Cigarette smoking during pregnancy is associated with a variety of adverse fetal outcomes. Nicotine is a likely contributor to these adverse effects, with fetal brain as one target organ. Vaccination of adult male rats against nicotine has been shown to reduce nicotine distribution to the brain. The current study examined whether vaccination of female rats before pregnancy would reduce the distribution to fetal brain of a single nicotine dose administered during gestation. Female rats immunized with a nicotine conjugate vaccine received a single dose of nicotine 0.03 mg/kg i.v. on gestational day 16 to 22. Five minutes later, vaccinated rats had substantially higher bound and lower unbound serum nicotine concentration and lower brain nicotine concentration than controls. Fetal brain nicotine concentration was reduced by 43% in vaccinated rats, comparable to the reduction in the maternal brain nicotine concentration. The whole-fetus nicotine concentration was not altered by vaccination. A similar experiment was performed in which pregnant rats were passively immunized with rabbit nicotine-specific IgG 7 or 21 mg/kg just before nicotine dosing. The effects of passive immunization on nicotine distribution in the mother were IgG dose-related and the higher dose reduced nicotine distribution to fetal brain by 60%. These data suggest that vaccine effects on nicotine distribution to serum and brain are similar in pregnant female rats to those previously reported in adult males. Vaccination of female rats before pregnancy, or passive immunization during pregnancy, can reduce the exposure of fetal brain to a single dose of maternally administered nicotine.

Inhibition of nicotine-induced seizures in rats by combining vaccination against nicotine with chronic nicotine infusion.

The ability of a nicotine vaccine to protect against nicotine-induced seizures was studied in rats. Groups of 10 rats were vaccinated with 3 doses of either a nicotine conjugate vaccine over 6 weeks to elicit high titers of nicotine-specific antibodies or with a control vaccine. Rats were then pretreated with a 1-week subcutaneous infusion of either nicotine 1 mg/kg/day or saline and then received a single 2 mg/kg ip dose of nicotine to provoke seizures. Vaccination reduced the incidence of seizures. The combination of vaccination and pretreatment with nicotine infusion was more effective than either treatment alone. These data suggest that vaccination is protective against this toxic effect of nicotine and that combining vaccination and chronic nicotine administration may provide a novel strategy for blocking some effects of nicotine.

Passive immunization against nicotine prevents nicotine alleviation of nicotine abstinence syndrome.

Passive immunization against nicotine interferes with its locomotor and pressor effects. The current study determined whether immunization could prevent another nicotine action: the reversal of nicotine abstinence syndrome. IgG containing 4.4-5.6% nicotine-specific antibody was isolated from rabbits immunized with 3'-amino-methyl-nicotine conjugated to a carrier protein. Twenty rats were rendered dependent by 7 days of subcutaneous infusion of 3.15 mg/kg/day nicotine (expressed as the base). Upon termination of nicotine infusion, each rat was injected intraperitoneally with 150 mg of IgG from normal serum (n=13) or from nicotine antiserum (n=7). Twenty-two and one-half hours later, all rats were observed over 15 min for baseline nicotine abstinence signs. Two and one-half hours after baseline observations, seven of the 13 rats pretreated with control IgG and all seven rats pretreated with nicotine-specific IgG were then challenged by 0.12 mg/kg (sc) nicotine. The remaining six rats pretreated with control IgG were challenged with saline alone. All rats were then observed again for abstinence signs. Nicotine injection caused significantly less reduction of abstinence signs in the immunized rats. The nicotine effect in immunized rats was comparable to the saline effect in nonimmunized rats. Immunization also significantly reduced free serum nicotine concentration and nicotine distribution to the brain. These results raise the possibility that immunization might prevent nicotine consumption from relieving the discomforts of smoking cessation.

Vaccination against nicotine during continued nicotine administration in rats: immunogenicity of the vaccine and effects on nicotine distribution to brain.

Vaccination against nicotine has been proposed as a potential treatment for nicotine dependence. Because vaccination may take months to elicit satisfactory antibody levels, the clinical usefulness of this approach will be enhanced if vaccination can be accomplished during continued nicotine intake (e.g., before a smoker quits). The current study examined the immunogenicity of a nicotine conjugate vaccine during continued nicotine dosing in rats, and its effects on nicotine distribution to brain. In the first experiment, nicotine was administered over 11 weeks as 20 intra venous (i.v.) bolus injections per day during the rat's active cycle to simulate the usual pattern of nicotine intake from cigarette smoking. In the second experiment, rats received a continuous s.c. infusion of nicotine by osmotic pump for 11 weeks to provide serum nicotine concentrations equivalent to those of a heavy smoker and 24 h/day nicotine exposure. Nicotine-specific antibody titers after the third booster dose were not compromised by either regimen of concurrent nicotine administration compared to those of rats receiving saline. A single additional i.v. nicotine dose was administered at the end of each experiment. The distribution of this single nicotine dose to brain was reduced by 40-60% in vaccinated rats compared to controls. Vaccine efficacy in reducing nicotine distribution to brain was not compromised by concurrent nicotine administration. These data suggest that vaccination during concurrent nicotine administration is feasible, and that the ability of vaccination to reduce nicotine distribution to brain is preserved even after months of nicotine dosing at rates approximating cigarette smoking.

A nicotine conjugate vaccine reduces nicotine distribution to brain and attenuates its behavioral and cardiovascular effects in rats.

Vaccination of animals to elicit drug-specific antibodies, or the passive transfer of such antibodies from other animals, can reduce the behavioral effects of drugs such as cocaine and heroin. To study the potential application of this approach to treating nicotine dependence, IgG was isolated from rabbits immunized with a nicotine-protein conjugate vaccine. Anesthetized rats received immune IgG containing nicotine-specific antibodies (Nic-IgG) or control-IgG i.v.. Thirty minutes later, rats received nicotine at 0.03 mg/kg i.v., equivalent on an mg/kg basis to the nicotine intake from two cigarettes by a smoker. Compared to control-IgG, Nic-IgG reduced the brain nicotine concentration in a dose-related manner (65% reduction at the highest IgG dose). Pretreatment with Nic-IgG also reduced the distribution to brain of five repeated doses of nicotine (equivalent to the nicotine intake from 10 cigarettes) administered over 80 min. To study blood pressure effects, rats received control-IgG or Nic-IgG 1 day prior to administering nicotine. Nicotine-induced systolic blood pressure increases were attenuated by Nic-IgG in a dose-related manner, and were almost completely blocked by the highest Nic-IgG dose. Pretreatment with Nic-IgG also completely prevented the nicotine-induced stimulation of locomotor activity observed in rats receiving control-IgG. Nic-IgG did not prevent locomotor activation from cocaine, demonstrating its specificity for nicotine. These data demonstrate that the administration of nicotine-specific antibodies can reduce or prevent some of the pharmacokinetic, cardiovascular, and behavioral consequences of nicotine in rats. Effects were observed at nicotine doses and nicotine serum concentrations equal to or exceeding those typically associated with nicotine exposure in cigarette smokers. A potential role for immunization in the treatment of nicotine dependence is suggested.